chore(settings): refactor settings processing (#756)

- Better settings tree structure logged using `qdm12/gotree`
- Read settings from environment variables, then files, then secret files
- Settings methods to default them, merge them and override them
- `DNS_PLAINTEXT_ADDRESS` default changed to `127.0.0.1` to use DoT. Warning added if set to something else.
- `HTTPPROXY_LISTENING_ADDRESS` instead of `HTTPPROXY_PORT` (with retro-compatibility)

internal/configuration/settings/dns.go

@@ -0,0 +1,82 @@
+package settings
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+// DNS contains settings to configure DNS.
+type DNS struct {
+	// ServerAddress is the DNS server to use inside
+	// the Go program and for the system.
+	// It defaults to '127.0.0.1' to be used with the
+	// DoT server. It cannot be nil in the internal
+	// state.
+	ServerAddress net.IP
+	// KeepNameserver is true if the Docker DNS server
+	// found in /etc/resolv.conf should be kept.
+	// Note settings this to true will go around the
+	// DoT server blocking.
+	// It defaults to false and cannot be nil in the
+	// internal state.
+	KeepNameserver *bool
+	// DOT contains settings to configure the DoT
+	// server.
+	DoT DoT
+}
+
+func (d DNS) validate() (err error) {
+	err = d.DoT.validate()
+	if err != nil {
+		return fmt.Errorf("failed validating DoT settings: %w", err)
+	}
+
+	return nil
+}
+
+func (d *DNS) Copy() (copied DNS) {
+	return DNS{
+		ServerAddress:  helpers.CopyIP(d.ServerAddress),
+		KeepNameserver: helpers.CopyBoolPtr(d.KeepNameserver),
+		DoT:            d.DoT.copy(),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (d *DNS) mergeWith(other DNS) {
+	d.ServerAddress = helpers.MergeWithIP(d.ServerAddress, other.ServerAddress)
+	d.KeepNameserver = helpers.MergeWithBool(d.KeepNameserver, other.KeepNameserver)
+	d.DoT.mergeWith(other.DoT)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (d *DNS) overrideWith(other DNS) {
+	d.ServerAddress = helpers.OverrideWithIP(d.ServerAddress, other.ServerAddress)
+	d.KeepNameserver = helpers.OverrideWithBool(d.KeepNameserver, other.KeepNameserver)
+	d.DoT.overrideWith(other.DoT)
+}
+
+func (d *DNS) setDefaults() {
+	localhost := net.IPv4(127, 0, 0, 1) //nolint:gomnd
+	d.ServerAddress = helpers.DefaultIP(d.ServerAddress, localhost)
+	d.KeepNameserver = helpers.DefaultBool(d.KeepNameserver, false)
+	d.DoT.setDefaults()
+}
+
+func (d DNS) String() string {
+	return d.toLinesNode().String()
+}
+
+func (d DNS) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("DNS settings:")
+	node.Appendf("DNS server address to use: %s", d.ServerAddress)
+	node.Appendf("Keep existing nameserver(s): %s", helpers.BoolPtrToYesNo(d.KeepNameserver))
+	node.AppendNode(d.DoT.toLinesNode())
+	return node
+}

internal/configuration/settings/dnsblacklist.go

@@ -0,0 +1,138 @@
+package settings
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+
+	"github.com/qdm12/dns/pkg/blacklist"
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+	"inet.af/netaddr"
+)
+
+// DNSBlacklist is settings for the DNS blacklist building.
+type DNSBlacklist struct {
+	BlockMalicious       *bool
+	BlockAds             *bool
+	BlockSurveillance    *bool
+	AllowedHosts         []string
+	AddBlockedHosts      []string
+	AddBlockedIPs        []netaddr.IP
+	AddBlockedIPPrefixes []netaddr.IPPrefix
+}
+
+func (b *DNSBlacklist) setDefaults() {
+	b.BlockMalicious = helpers.DefaultBool(b.BlockMalicious, true)
+	b.BlockAds = helpers.DefaultBool(b.BlockAds, false)
+	b.BlockSurveillance = helpers.DefaultBool(b.BlockSurveillance, true)
+}
+
+var hostRegex = regexp.MustCompile(`^([a-zA-Z0-9]|[a-zA-Z0-9_][a-zA-Z0-9\-_]{0,61}[a-zA-Z0-9_])(\.([a-zA-Z0-9]|[a-zA-Z0-9_][a-zA-Z0-9\-_]{0,61}[a-zA-Z0-9]))*$`) //nolint:lll
+
+var (
+	ErrAllowedHostNotValid = errors.New("allowed host is not valid")
+	ErrBlockedHostNotValid = errors.New("blocked host is not valid")
+)
+
+func (b DNSBlacklist) validate() (err error) {
+	for _, host := range b.AllowedHosts {
+		if !hostRegex.MatchString(host) {
+			return fmt.Errorf("%w: %s", ErrAllowedHostNotValid, host)
+		}
+	}
+
+	for _, host := range b.AddBlockedHosts {
+		if !hostRegex.MatchString(host) {
+			return fmt.Errorf("%w: %s", ErrBlockedHostNotValid, host)
+		}
+	}
+
+	return nil
+}
+
+func (b DNSBlacklist) copy() (copied DNSBlacklist) {
+	return DNSBlacklist{
+		BlockMalicious:       helpers.CopyBoolPtr(b.BlockMalicious),
+		BlockAds:             helpers.CopyBoolPtr(b.BlockAds),
+		BlockSurveillance:    helpers.CopyBoolPtr(b.BlockSurveillance),
+		AllowedHosts:         helpers.CopyStringSlice(b.AllowedHosts),
+		AddBlockedHosts:      helpers.CopyStringSlice(b.AddBlockedHosts),
+		AddBlockedIPs:        helpers.CopyNetaddrIPsSlice(b.AddBlockedIPs),
+		AddBlockedIPPrefixes: helpers.CopyIPPrefixSlice(b.AddBlockedIPPrefixes),
+	}
+}
+
+func (b *DNSBlacklist) mergeWith(other DNSBlacklist) {
+	b.BlockMalicious = helpers.MergeWithBool(b.BlockMalicious, other.BlockMalicious)
+	b.BlockAds = helpers.MergeWithBool(b.BlockAds, other.BlockAds)
+	b.BlockSurveillance = helpers.MergeWithBool(b.BlockSurveillance, other.BlockSurveillance)
+	b.AllowedHosts = helpers.MergeStringSlices(b.AllowedHosts, other.AllowedHosts)
+	b.AddBlockedHosts = helpers.MergeStringSlices(b.AddBlockedHosts, other.AddBlockedHosts)
+	b.AddBlockedIPs = helpers.MergeNetaddrIPsSlices(b.AddBlockedIPs, other.AddBlockedIPs)
+	b.AddBlockedIPPrefixes = helpers.MergeIPPrefixesSlices(b.AddBlockedIPPrefixes, other.AddBlockedIPPrefixes)
+}
+
+func (b *DNSBlacklist) overrideWith(other DNSBlacklist) {
+	b.BlockMalicious = helpers.OverrideWithBool(b.BlockMalicious, other.BlockMalicious)
+	b.BlockAds = helpers.OverrideWithBool(b.BlockAds, other.BlockAds)
+	b.BlockSurveillance = helpers.OverrideWithBool(b.BlockSurveillance, other.BlockSurveillance)
+	b.AllowedHosts = helpers.OverrideWithStringSlice(b.AllowedHosts, other.AllowedHosts)
+	b.AddBlockedHosts = helpers.OverrideWithStringSlice(b.AddBlockedHosts, other.AddBlockedHosts)
+	b.AddBlockedIPs = helpers.OverrideWithNetaddrIPsSlice(b.AddBlockedIPs, other.AddBlockedIPs)
+	b.AddBlockedIPPrefixes = helpers.OverrideWithIPPrefixesSlice(b.AddBlockedIPPrefixes, other.AddBlockedIPPrefixes)
+}
+
+func (b DNSBlacklist) ToBlacklistFormat() (settings blacklist.BuilderSettings, err error) {
+	return blacklist.BuilderSettings{
+		BlockMalicious:       *b.BlockMalicious,
+		BlockAds:             *b.BlockAds,
+		BlockSurveillance:    *b.BlockSurveillance,
+		AllowedHosts:         b.AllowedHosts,
+		AddBlockedHosts:      b.AddBlockedHosts,
+		AddBlockedIPs:        b.AddBlockedIPs,
+		AddBlockedIPPrefixes: b.AddBlockedIPPrefixes,
+	}, nil
+}
+
+func (b DNSBlacklist) String() string {
+	return b.toLinesNode().String()
+}
+
+func (b DNSBlacklist) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("DNS filtering settings:")
+
+	node.Appendf("Block malicious: %s", helpers.BoolPtrToYesNo(b.BlockMalicious))
+	node.Appendf("Block ads: %s", helpers.BoolPtrToYesNo(b.BlockAds))
+	node.Appendf("Block surveillance: %s", helpers.BoolPtrToYesNo(b.BlockSurveillance))
+
+	if len(b.AllowedHosts) > 0 {
+		allowedHostsNode := node.Appendf("Allowed hosts:")
+		for _, host := range b.AllowedHosts {
+			allowedHostsNode.Appendf(host)
+		}
+	}
+
+	if len(b.AddBlockedHosts) > 0 {
+		blockedHostsNode := node.Appendf("Blocked hosts:")
+		for _, host := range b.AddBlockedHosts {
+			blockedHostsNode.Appendf(host)
+		}
+	}
+
+	if len(b.AddBlockedIPs) > 0 {
+		blockedIPsNode := node.Appendf("Blocked IP addresses:")
+		for _, ip := range b.AddBlockedIPs {
+			blockedIPsNode.Appendf(ip.String())
+		}
+	}
+
+	if len(b.AddBlockedIPPrefixes) > 0 {
+		blockedIPPrefixesNode := node.Appendf("Blocked IP networks:")
+		for _, ipNetwork := range b.AddBlockedIPPrefixes {
+			blockedIPPrefixesNode.Appendf(ipNetwork.String())
+		}
+	}
+
+	return node
+}

internal/configuration/settings/dot.go

@@ -0,0 +1,113 @@
+package settings
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+// DoT contains settings to configure the DoT server.
+type DoT struct {
+	// Enabled is true if the DoT server should be running
+	// and used. It defaults to true, and cannot be nil
+	// in the internal state.
+	Enabled *bool
+	// UpdatePeriod is the period to update DNS block
+	// lists and cryptographic files for DNSSEC validation.
+	// It can be set to 0 to disable the update.
+	// It defaults to 24h and cannot be nil in
+	// the internal state.
+	UpdatePeriod *time.Duration
+	// Unbound contains settings to configure Unbound.
+	Unbound Unbound
+	// Blacklist contains settings to configure the filter
+	// block lists.
+	Blacklist DNSBlacklist
+}
+
+var (
+	ErrDoTUpdatePeriodTooShort = errors.New("update period is too short")
+)
+
+func (d DoT) validate() (err error) {
+	const minUpdatePeriod = 30 * time.Second
+	if *d.UpdatePeriod < minUpdatePeriod {
+		return fmt.Errorf("%w: %s must be bigger than %s",
+			ErrDoTUpdatePeriodTooShort, *d.UpdatePeriod, minUpdatePeriod)
+	}
+
+	err = d.Unbound.validate()
+	if err != nil {
+		return err
+	}
+
+	err = d.Blacklist.validate()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (d *DoT) copy() (copied DoT) {
+	return DoT{
+		Enabled:      helpers.CopyBoolPtr(d.Enabled),
+		UpdatePeriod: helpers.CopyDurationPtr(d.UpdatePeriod),
+		Unbound:      d.Unbound.copy(),
+		Blacklist:    d.Blacklist.copy(),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (d *DoT) mergeWith(other DoT) {
+	d.Enabled = helpers.MergeWithBool(d.Enabled, other.Enabled)
+	d.UpdatePeriod = helpers.MergeWithDuration(d.UpdatePeriod, other.UpdatePeriod)
+	d.Unbound.mergeWith(other.Unbound)
+	d.Blacklist.mergeWith(other.Blacklist)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (d *DoT) overrideWith(other DoT) {
+	d.Enabled = helpers.OverrideWithBool(d.Enabled, other.Enabled)
+	d.UpdatePeriod = helpers.OverrideWithDuration(d.UpdatePeriod, other.UpdatePeriod)
+	d.Unbound.overrideWith(other.Unbound)
+	d.Blacklist.overrideWith(other.Blacklist)
+}
+
+func (d *DoT) setDefaults() {
+	d.Enabled = helpers.DefaultBool(d.Enabled, true)
+	const defaultUpdatePeriod = 24 * time.Hour
+	d.UpdatePeriod = helpers.DefaultDuration(d.UpdatePeriod, defaultUpdatePeriod)
+	d.Unbound.setDefaults()
+	d.Blacklist.setDefaults()
+}
+
+func (d DoT) String() string {
+	return d.toLinesNode().String()
+}
+
+func (d DoT) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("DNS over TLS settings:")
+
+	node.Appendf("Enabled: %s", helpers.BoolPtrToYesNo(d.Enabled))
+	if !*d.Enabled {
+		return node
+	}
+
+	update := "disabled"
+	if *d.UpdatePeriod > 0 {
+		update = "every " + d.UpdatePeriod.String()
+	}
+	node.Appendf("Update period: %s", update)
+
+	node.AppendNode(d.Unbound.toLinesNode())
+	node.AppendNode(d.Blacklist.toLinesNode())
+
+	return node
+}

internal/configuration/settings/errors.go

@@ -0,0 +1,51 @@
+package settings
+
+import "errors"
+
+var (
+	ErrCityNotValid                    = errors.New("the city specified is not valid")
+	ErrControlServerPrivilegedPort     = errors.New("cannot use privileged port without running as root")
+	ErrCountryNotValid                 = errors.New("the country specified is not valid")
+	ErrFirewallZeroPort                = errors.New("cannot have a zero port to block")
+	ErrHostnameNotValid                = errors.New("the hostname specified is not valid")
+	ErrISPNotValid                     = errors.New("the ISP specified is not valid")
+	ErrNameNotValid                    = errors.New("the server name specified is not valid")
+	ErrOpenVPNClientCertMissing        = errors.New("client certificate is missing")
+	ErrOpenVPNClientCertNotValid       = errors.New("client certificate is not valid")
+	ErrOpenVPNClientKeyMissing         = errors.New("client key is missing")
+	ErrOpenVPNClientKeyNotValid        = errors.New("client key is not valid")
+	ErrOpenVPNConfigFile               = errors.New("custom configuration file error")
+	ErrOpenVPNCustomPortNotAllowed     = errors.New("custom endpoint port is not allowed")
+	ErrOpenVPNEncryptionPresetNotValid = errors.New("PIA encryption preset is not valid")
+	ErrOpenVPNInterfaceNotValid        = errors.New("interface name is not valid")
+	ErrOpenVPNMSSFixIsTooHigh          = errors.New("mssfix option value is too high")
+	ErrOpenVPNPasswordIsEmpty          = errors.New("password is empty")
+	ErrOpenVPNTCPNotSupported          = errors.New("TCP protocol is not supported")
+	ErrOpenVPNUserIsEmpty              = errors.New("user is empty")
+	ErrOpenVPNVerbosityIsOutOfBounds   = errors.New("verbosity value is out of bounds")
+	ErrOpenVPNVersionIsNotValid        = errors.New("version is not valid")
+	ErrPortForwardingEnabled           = errors.New("port forwarding cannot be enabled")
+	ErrPortForwardingFilepathNotValid  = errors.New("port forwarding filepath given is not valid")
+	ErrPublicIPFilepathNotValid        = errors.New("public IP address file path is not valid")
+	ErrPublicIPPeriodTooShort          = errors.New("public IP address check period is too short")
+	ErrRegionNotValid                  = errors.New("the region specified is not valid")
+	ErrServerAddressNotValid           = errors.New("server listening address is not valid")
+	ErrSystemPGIDNotValid              = errors.New("process group id is not valid")
+	ErrSystemPUIDNotValid              = errors.New("process user id is not valid")
+	ErrSystemTimezoneNotValid          = errors.New("timezone is not valid")
+	ErrVPNProviderNameNotValid         = errors.New("VPN provider name is not valid")
+	ErrVPNTypeNotValid                 = errors.New("VPN type is not valid")
+	ErrWireguardEndpointIPNotSet       = errors.New("endpoint IP is not set")
+	ErrWireguardEndpointPortNotAllowed = errors.New("endpoint port is not allowed")
+	ErrWireguardEndpointPortNotSet     = errors.New("endpoint port is not set")
+	ErrWireguardInterfaceAddressNotSet = errors.New("interface address is not set")
+	ErrWireguardInterfaceNotValid      = errors.New("interface name is not valid")
+	ErrWireguardPreSharedKeyNotSet     = errors.New("pre-shared key is not set")
+	ErrWireguardPreSharedKeyNotValid   = errors.New("pre-shared key is not valid")
+	ErrWireguardPrivateKeyNotSet       = errors.New("private key is not set")
+	ErrWireguardPrivateKeyNotValid     = errors.New("private key is not valid")
+	ErrWireguardPublicKeyNotSet        = errors.New("public key is not set")
+	ErrWireguardPublicKeyNotValid      = errors.New("public key is not valid")
+
+	ErrUpdaterPeriodTooSmall = errors.New("VPN server data updater period is too small")
+)

internal/configuration/settings/firewall.go

@@ -0,0 +1,117 @@
+package settings
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+// Firewall contains settings to customize the firewall operation.
+type Firewall struct {
+	VPNInputPorts   []uint16
+	InputPorts      []uint16
+	OutboundSubnets []net.IPNet
+	Enabled         *bool
+	Debug           *bool
+}
+
+func (f Firewall) validate() (err error) {
+	if hasZeroPort(f.VPNInputPorts) {
+		return fmt.Errorf("VPN input ports: %w", ErrFirewallZeroPort)
+	}
+
+	if hasZeroPort(f.InputPorts) {
+		return fmt.Errorf("input ports: %w", ErrFirewallZeroPort)
+	}
+
+	return nil
+}
+
+func hasZeroPort(ports []uint16) (has bool) {
+	for _, port := range ports {
+		if port == 0 {
+			return true
+		}
+	}
+	return false
+}
+
+func (f *Firewall) copy() (copied Firewall) {
+	return Firewall{
+		VPNInputPorts:   helpers.CopyUint16Slice(f.VPNInputPorts),
+		InputPorts:      helpers.CopyUint16Slice(f.InputPorts),
+		OutboundSubnets: helpers.CopyIPNetSlice(f.OutboundSubnets),
+		Enabled:         helpers.CopyBoolPtr(f.Enabled),
+		Debug:           helpers.CopyBoolPtr(f.Debug),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+// It merges values of slices together, even if they
+// are set in the receiver settings.
+func (f *Firewall) mergeWith(other Firewall) {
+	f.VPNInputPorts = helpers.MergeUint16Slices(f.VPNInputPorts, other.VPNInputPorts)
+	f.InputPorts = helpers.MergeUint16Slices(f.InputPorts, other.InputPorts)
+	f.OutboundSubnets = helpers.MergeIPNetsSlices(f.OutboundSubnets, other.OutboundSubnets)
+	f.Enabled = helpers.MergeWithBool(f.Enabled, other.Enabled)
+	f.Debug = helpers.MergeWithBool(f.Debug, other.Debug)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (f *Firewall) overrideWith(other Firewall) {
+	f.VPNInputPorts = helpers.OverrideWithUint16Slice(f.VPNInputPorts, other.VPNInputPorts)
+	f.InputPorts = helpers.OverrideWithUint16Slice(f.InputPorts, other.InputPorts)
+	f.OutboundSubnets = helpers.OverrideWithIPNetsSlice(f.OutboundSubnets, other.OutboundSubnets)
+	f.Enabled = helpers.OverrideWithBool(f.Enabled, other.Enabled)
+	f.Debug = helpers.OverrideWithBool(f.Debug, other.Debug)
+}
+
+func (f *Firewall) setDefaults() {
+	f.Enabled = helpers.DefaultBool(f.Enabled, true)
+	f.Debug = helpers.DefaultBool(f.Debug, false)
+}
+
+func (f Firewall) String() string {
+	return f.toLinesNode().String()
+}
+
+func (f Firewall) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Firewall settings:")
+
+	node.Appendf("Enabled: %s", helpers.BoolPtrToYesNo(f.Enabled))
+	if !*f.Enabled {
+		return node
+	}
+
+	if *f.Debug {
+		node.Appendf("Debug mode: on")
+	}
+
+	if len(f.VPNInputPorts) > 0 {
+		vpnInputPortsNode := node.Appendf("VPN input ports:")
+		for _, port := range f.VPNInputPorts {
+			vpnInputPortsNode.Appendf("%d", port)
+		}
+	}
+
+	if len(f.InputPorts) > 0 {
+		inputPortsNode := node.Appendf("Input ports:")
+		for _, port := range f.InputPorts {
+			inputPortsNode.Appendf("%d", port)
+		}
+	}
+
+	if len(f.OutboundSubnets) > 0 {
+		outboundSubnets := node.Appendf("Outbound subnets:")
+		for _, subnet := range f.OutboundSubnets {
+			outboundSubnets.Appendf("%s", subnet)
+		}
+	}
+
+	return node
+}

internal/configuration/settings/health.go

@@ -0,0 +1,83 @@
+package settings
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+	"github.com/qdm12/govalid/address"
+)
+
+// Health contains settings for the healthcheck and health server.
+type Health struct {
+	// ServerAddress is the listening address
+	// for the health check server.
+	// It cannot be the empty string in the internal state.
+	ServerAddress string
+	// AddressToPing is the IP address or domain name to
+	// ping periodically for the health check.
+	// It cannot be the empty string in the internal state.
+	AddressToPing string
+	VPN           HealthyWait
+}
+
+func (h Health) Validate() (err error) {
+	uid := os.Getuid()
+	_, err = address.Validate(h.ServerAddress,
+		address.OptionListening(uid))
+	if err != nil {
+		return fmt.Errorf("%w: %s",
+			ErrServerAddressNotValid, err)
+	}
+
+	err = h.VPN.validate()
+	if err != nil {
+		return fmt.Errorf("health VPN settings validation failed: %w", err)
+	}
+
+	return nil
+}
+
+func (h *Health) copy() (copied Health) {
+	return Health{
+		ServerAddress: h.ServerAddress,
+		AddressToPing: h.AddressToPing,
+		VPN:           h.VPN.copy(),
+	}
+}
+
+// MergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (h *Health) MergeWith(other Health) {
+	h.ServerAddress = helpers.MergeWithString(h.ServerAddress, other.ServerAddress)
+	h.AddressToPing = helpers.MergeWithString(h.AddressToPing, other.AddressToPing)
+	h.VPN.mergeWith(other.VPN)
+}
+
+// OverrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (h *Health) OverrideWith(other Health) {
+	h.ServerAddress = helpers.OverrideWithString(h.ServerAddress, other.ServerAddress)
+	h.AddressToPing = helpers.OverrideWithString(h.AddressToPing, other.AddressToPing)
+	h.VPN.overrideWith(other.VPN)
+}
+
+func (h *Health) SetDefaults() {
+	h.ServerAddress = helpers.DefaultString(h.ServerAddress, "127.0.0.1:9999")
+	h.AddressToPing = helpers.DefaultString(h.AddressToPing, "github.com")
+	h.VPN.setDefaults()
+}
+
+func (h Health) String() string {
+	return h.toLinesNode().String()
+}
+
+func (h Health) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Health settings:")
+	node.Appendf("Server listening address: %s", h.ServerAddress)
+	node.Appendf("Address to ping: %s", h.AddressToPing)
+	node.AppendNode(h.VPN.toLinesNode("VPN"))
+	return node
+}

internal/configuration/settings/healthywait.go

@@ -0,0 +1,66 @@
+package settings
+
+import (
+	"time"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+type HealthyWait struct {
+	// Initial is the initial duration to wait for the program
+	// to be healthy before taking action.
+	// It cannot be nil in the internal state.
+	Initial *time.Duration
+	// Addition is the duration to add to the Initial duration
+	// after Initial has expired to wait longer for the program
+	// to be healthy.
+	// It cannot be nil in the internal state.
+	Addition *time.Duration
+}
+
+func (h HealthyWait) validate() (err error) {
+	return nil
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (h *HealthyWait) copy() (copied HealthyWait) {
+	return HealthyWait{
+		Initial:  helpers.CopyDurationPtr(h.Initial),
+		Addition: helpers.CopyDurationPtr(h.Addition),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (h *HealthyWait) mergeWith(other HealthyWait) {
+	h.Initial = helpers.MergeWithDuration(h.Initial, other.Initial)
+	h.Addition = helpers.MergeWithDuration(h.Addition, other.Addition)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (h *HealthyWait) overrideWith(other HealthyWait) {
+	h.Initial = helpers.OverrideWithDuration(h.Initial, other.Initial)
+	h.Addition = helpers.OverrideWithDuration(h.Addition, other.Addition)
+}
+
+func (h *HealthyWait) setDefaults() {
+	const initialDurationDefault = 6 * time.Second
+	const additionDurationDefault = 5 * time.Second
+	h.Initial = helpers.DefaultDuration(h.Initial, initialDurationDefault)
+	h.Addition = helpers.DefaultDuration(h.Addition, additionDurationDefault)
+}
+
+func (h HealthyWait) String() string {
+	return h.toLinesNode("Health").String()
+}
+
+func (h HealthyWait) toLinesNode(kind string) (node *gotree.Node) {
+	node = gotree.New(kind + " wait durations:")
+	node.Appendf("Initial duration: %s", *h.Initial)
+	node.Appendf("Additional duration: %s", *h.Addition)
+	return node
+}

internal/configuration/settings/helpers/belong.go

@@ -0,0 +1,45 @@
+package helpers
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+func IsOneOf(value string, choices ...string) (ok bool) {
+	for _, choice := range choices {
+		if value == choice {
+			return true
+		}
+	}
+	return false
+}
+
+var ErrValueNotOneOf = errors.New("value is not one of the possible choices")
+
+func AreAllOneOf(values, choices []string) (err error) {
+	set := make(map[string]struct{}, len(choices))
+	for _, choice := range choices {
+		choice = strings.ToLower(choice)
+		set[choice] = struct{}{}
+	}
+
+	for _, value := range values {
+		_, ok := set[value]
+		if !ok {
+			return fmt.Errorf("%w: value %q, choices available are %s",
+				ErrValueNotOneOf, value, strings.Join(choices, ", "))
+		}
+	}
+
+	return nil
+}
+
+func Uint16IsOneOf(port uint16, choices []uint16) (ok bool) {
+	for _, choice := range choices {
+		if port == choice {
+			return true
+		}
+	}
+	return false
+}

internal/configuration/settings/helpers/copy.go

@@ -0,0 +1,190 @@
+package helpers
+
+import (
+	"net"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+	"inet.af/netaddr"
+)
+
+func CopyStringPtr(original *string) (copied *string) {
+	if original == nil {
+		return nil
+	}
+	copied = new(string)
+	*copied = *original
+	return copied
+}
+
+func CopyBoolPtr(original *bool) (copied *bool) {
+	if original == nil {
+		return nil
+	}
+	copied = new(bool)
+	*copied = *original
+	return copied
+}
+
+func CopyUint8Ptr(original *uint8) (copied *uint8) {
+	if original == nil {
+		return nil
+	}
+	copied = new(uint8)
+	*copied = *original
+	return copied
+}
+
+func CopyUint16Ptr(original *uint16) (copied *uint16) {
+	if original == nil {
+		return nil
+	}
+	copied = new(uint16)
+	*copied = *original
+	return copied
+}
+
+func CopyIntPtr(original *int) (copied *int) {
+	if original == nil {
+		return nil
+	}
+	copied = new(int)
+	*copied = *original
+	return copied
+}
+
+func CopyDurationPtr(original *time.Duration) (copied *time.Duration) {
+	if original == nil {
+		return nil
+	}
+	copied = new(time.Duration)
+	*copied = *original
+	return copied
+}
+
+func CopyLogLevelPtr(original *logging.Level) (copied *logging.Level) {
+	if original == nil {
+		return nil
+	}
+	copied = new(logging.Level)
+	*copied = *original
+	return copied
+}
+
+func CopyIP(original net.IP) (copied net.IP) {
+	if original == nil {
+		return nil
+	}
+	copied = make(net.IP, len(original))
+	copy(copied, original)
+	return copied
+}
+
+func CopyIPNet(original net.IPNet) (copied net.IPNet) {
+	if original.IP != nil {
+		copied.IP = make(net.IP, len(original.IP))
+		copy(copied.IP, original.IP)
+	}
+
+	if original.Mask != nil {
+		copied.Mask = make(net.IPMask, len(original.Mask))
+		copy(copied.Mask, original.Mask)
+	}
+
+	return copied
+}
+
+func CopyIPNetPtr(original *net.IPNet) (copied *net.IPNet) {
+	if original == nil {
+		return nil
+	}
+
+	copied = new(net.IPNet)
+	*copied = CopyIPNet(*original)
+	return copied
+}
+
+func CopyNetaddrIP(original netaddr.IP) (copied netaddr.IP) {
+	b, err := original.MarshalBinary()
+	if err != nil {
+		panic(err)
+	}
+
+	err = copied.UnmarshalBinary(b)
+	if err != nil {
+		panic(err)
+	}
+
+	return copied
+}
+
+func CopyIPPrefix(original netaddr.IPPrefix) (copied netaddr.IPPrefix) {
+	b, err := original.MarshalText()
+	if err != nil {
+		panic(err)
+	}
+
+	err = copied.UnmarshalText(b)
+	if err != nil {
+		panic(err)
+	}
+
+	return copied
+}
+
+func CopyStringSlice(original []string) (copied []string) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]string, len(original))
+	copy(copied, original)
+	return copied
+}
+
+func CopyUint16Slice(original []uint16) (copied []uint16) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]uint16, len(original))
+	copy(copied, original)
+	return copied
+}
+
+func CopyIPNetSlice(original []net.IPNet) (copied []net.IPNet) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]net.IPNet, len(original))
+	for i := range original {
+		copied[i] = CopyIPNet(original[i])
+	}
+	return copied
+}
+
+func CopyIPPrefixSlice(original []netaddr.IPPrefix) (copied []netaddr.IPPrefix) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]netaddr.IPPrefix, len(original))
+	for i := range original {
+		copied[i] = CopyIPPrefix(original[i])
+	}
+	return copied
+}
+
+func CopyNetaddrIPsSlice(original []netaddr.IP) (copied []netaddr.IP) {
+	if original == nil {
+		return nil
+	}
+
+	copied = make([]netaddr.IP, len(original))
+	for i := range original {
+		copied[i] = CopyNetaddrIP(original[i])
+	}
+
+	return copied
+}

internal/configuration/settings/helpers/default.go

@@ -0,0 +1,93 @@
+package helpers
+
+import (
+	"net"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+)
+
+func DefaultInt(existing *int, defaultValue int) (
+	result *int) {
+	if existing != nil {
+		return existing
+	}
+	result = new(int)
+	*result = defaultValue
+	return result
+}
+
+func DefaultUint8(existing *uint8, defaultValue uint8) (
+	result *uint8) {
+	if existing != nil {
+		return existing
+	}
+	result = new(uint8)
+	*result = defaultValue
+	return result
+}
+
+func DefaultUint16(existing *uint16, defaultValue uint16) (
+	result *uint16) {
+	if existing != nil {
+		return existing
+	}
+	result = new(uint16)
+	*result = defaultValue
+	return result
+}
+
+func DefaultBool(existing *bool, defaultValue bool) (
+	result *bool) {
+	if existing != nil {
+		return existing
+	}
+	result = new(bool)
+	*result = defaultValue
+	return result
+}
+
+func DefaultString(existing string, defaultValue string) (
+	result string) {
+	if existing != "" {
+		return existing
+	}
+	return defaultValue
+}
+
+func DefaultStringPtr(existing *string, defaultValue string) (result *string) {
+	if existing != nil {
+		return existing
+	}
+	result = new(string)
+	*result = defaultValue
+	return result
+}
+
+func DefaultDuration(existing *time.Duration,
+	defaultValue time.Duration) (result *time.Duration) {
+	if existing != nil {
+		return existing
+	}
+	result = new(time.Duration)
+	*result = defaultValue
+	return result
+}
+
+func DefaultLogLevel(existing *logging.Level,
+	defaultValue logging.Level) (result *logging.Level) {
+	if existing != nil {
+		return existing
+	}
+	result = new(logging.Level)
+	*result = defaultValue
+	return result
+}
+
+func DefaultIP(existing net.IP, defaultValue net.IP) (
+	result net.IP) {
+	if existing != nil {
+		return existing
+	}
+	return defaultValue
+}

internal/configuration/settings/helpers/files.go

@@ -0,0 +1,31 @@
+package helpers
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+var (
+	ErrFileDoesNotExist = errors.New("file does not exist")
+	ErrFileRead         = errors.New("cannot read file")
+	ErrFileClose        = errors.New("cannot close file")
+)
+
+func FileExists(path string) (err error) {
+	path = filepath.Clean(path)
+
+	f, err := os.Open(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("%w: %s", ErrFileDoesNotExist, path)
+	} else if err != nil {
+		return fmt.Errorf("%w: %s", ErrFileRead, err)
+	}
+
+	if err := f.Close(); err != nil {
+		return fmt.Errorf("%w: %s", ErrFileClose, err)
+	}
+
+	return nil
+}

internal/configuration/settings/helpers/merge.go

@@ -0,0 +1,226 @@
+package helpers
+
+import (
+	"net"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+	"inet.af/netaddr"
+)
+
+func MergeWithBool(existing, other *bool) (result *bool) {
+	if existing != nil {
+		return existing
+	} else if other == nil {
+		return nil
+	}
+	result = new(bool)
+	*result = *other
+	return result
+}
+
+func MergeWithString(existing, other string) (result string) {
+	if existing != "" {
+		return existing
+	}
+	return other
+}
+
+func MergeWithStringPtr(existing, other *string) (result *string) {
+	if existing != nil {
+		return existing
+	} else if other == nil {
+		return nil
+	}
+	result = new(string)
+	*result = *other
+	return result
+}
+
+func MergeWithInt(existing, other *int) (result *int) {
+	if existing != nil {
+		return existing
+	} else if other == nil {
+		return nil
+	}
+	result = new(int)
+	*result = *other
+	return result
+}
+
+func MergeWithUint8(existing, other *uint8) (result *uint8) {
+	if existing != nil {
+		return existing
+	} else if other == nil {
+		return nil
+	}
+	result = new(uint8)
+	*result = *other
+	return result
+}
+
+func MergeWithUint16(existing, other *uint16) (result *uint16) {
+	if existing != nil {
+		return existing
+	} else if other == nil {
+		return nil
+	}
+	result = new(uint16)
+	*result = *other
+	return result
+}
+
+func MergeWithIP(existing, other net.IP) (result net.IP) {
+	if existing != nil {
+		return existing
+	} else if other == nil {
+		return nil
+	}
+	result = make(net.IP, len(other))
+	copy(result, other)
+	return result
+}
+
+func MergeWithDuration(existing, other *time.Duration) (result *time.Duration) {
+	if existing != nil {
+		return existing
+	}
+	return other
+}
+
+func MergeWithLogLevel(existing, other *logging.Level) (result *logging.Level) {
+	if existing != nil {
+		return existing
+	} else if other == nil {
+		return nil
+	}
+	result = new(logging.Level)
+	*result = *other
+	return result
+}
+
+func MergeStringSlices(a, b []string) (result []string) {
+	if a == nil && b == nil {
+		return nil
+	}
+
+	seen := make(map[string]struct{}, len(a)+len(b))
+	result = make([]string, 0, len(a)+len(b))
+	for _, s := range a {
+		if _, ok := seen[s]; ok {
+			continue // duplicate
+		}
+		result = append(result, s)
+		seen[s] = struct{}{}
+	}
+	for _, s := range b {
+		if _, ok := seen[s]; ok {
+			continue // duplicate
+		}
+		result = append(result, s)
+		seen[s] = struct{}{}
+	}
+	return result
+}
+
+func MergeUint16Slices(a, b []uint16) (result []uint16) {
+	if a == nil && b == nil {
+		return nil
+	}
+
+	seen := make(map[uint16]struct{}, len(a)+len(b))
+	result = make([]uint16, 0, len(a)+len(b))
+	for _, n := range a {
+		if _, ok := seen[n]; ok {
+			continue // duplicate
+		}
+		result = append(result, n)
+		seen[n] = struct{}{}
+	}
+	for _, n := range b {
+		if _, ok := seen[n]; ok {
+			continue // duplicate
+		}
+		result = append(result, n)
+		seen[n] = struct{}{}
+	}
+	return result
+}
+
+func MergeIPNetsSlices(a, b []net.IPNet) (result []net.IPNet) {
+	if a == nil && b == nil {
+		return nil
+	}
+
+	seen := make(map[string]struct{}, len(a)+len(b))
+	result = make([]net.IPNet, 0, len(a)+len(b))
+	for _, ipNet := range a {
+		key := ipNet.String()
+		if _, ok := seen[key]; ok {
+			continue // duplicate
+		}
+		result = append(result, ipNet)
+		seen[key] = struct{}{}
+	}
+	for _, ipNet := range b {
+		key := ipNet.String()
+		if _, ok := seen[key]; ok {
+			continue // duplicate
+		}
+		result = append(result, ipNet)
+		seen[key] = struct{}{}
+	}
+	return result
+}
+
+func MergeNetaddrIPsSlices(a, b []netaddr.IP) (result []netaddr.IP) {
+	if a == nil && b == nil {
+		return nil
+	}
+
+	seen := make(map[string]struct{}, len(a)+len(b))
+	result = make([]netaddr.IP, 0, len(a)+len(b))
+	for _, ip := range a {
+		key := ip.String()
+		if _, ok := seen[key]; ok {
+			continue // duplicate
+		}
+		result = append(result, ip)
+		seen[key] = struct{}{}
+	}
+	for _, ip := range b {
+		key := ip.String()
+		if _, ok := seen[key]; ok {
+			continue // duplicate
+		}
+		result = append(result, ip)
+		seen[key] = struct{}{}
+	}
+	return result
+}
+
+func MergeIPPrefixesSlices(a, b []netaddr.IPPrefix) (result []netaddr.IPPrefix) {
+	if a == nil && b == nil {
+		return nil
+	}
+
+	seen := make(map[string]struct{}, len(a)+len(b))
+	result = make([]netaddr.IPPrefix, 0, len(a)+len(b))
+	for _, ipPrefix := range a {
+		key := ipPrefix.String()
+		if _, ok := seen[key]; ok {
+			continue // duplicate
+		}
+		result = append(result, ipPrefix)
+		seen[key] = struct{}{}
+	}
+	for _, ipPrefix := range b {
+		key := ipPrefix.String()
+		if _, ok := seen[key]; ok {
+			continue // duplicate
+		}
+		result = append(result, ipPrefix)
+		seen[key] = struct{}{}
+	}
+	return result
+}

internal/configuration/settings/helpers/messages.go

@@ -0,0 +1,29 @@
+package helpers
+
+import (
+	"fmt"
+	"strings"
+)
+
+func ChoicesOrString(choices []string) string {
+	return strings.Join(
+		choices[:len(choices)-1], ", ") +
+		" or " + choices[len(choices)-1]
+}
+
+func PortChoicesOrString(ports []uint16) (s string) {
+	switch len(ports) {
+	case 0:
+		return "there is no allowed port"
+	case 1:
+		return "allowed port is " + fmt.Sprint(ports[0])
+	}
+
+	s = "allowed ports are "
+	portStrings := make([]string, len(ports))
+	for i := range ports {
+		portStrings[i] = fmt.Sprint(ports[i])
+	}
+	s += ChoicesOrString(portStrings)
+	return s
+}

internal/configuration/settings/helpers/obfuscate.go

@@ -0,0 +1,25 @@
+package helpers
+
+func ObfuscateWireguardKey(fullKey string) (obfuscatedKey string) {
+	const minKeyLength = 10
+	if len(fullKey) < minKeyLength {
+		return "(too short)"
+	}
+
+	lastIndex := len(fullKey) - 1
+	return fullKey[0:2] + "..." + fullKey[lastIndex-2:]
+}
+
+func ObfuscatePassword(password string) (obfuscatedPassword string) {
+	if password != "" {
+		return "[set]"
+	}
+	return "[not set]"
+}
+
+func ObfuscateData(data string) (obfuscated string) {
+	if data != "" {
+		return "[set]"
+	}
+	return "[not set]"
+}

internal/configuration/settings/helpers/override.go

@@ -0,0 +1,133 @@
+package helpers
+
+import (
+	"net"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+	"inet.af/netaddr"
+)
+
+func OverrideWithBool(existing, other *bool) (result *bool) {
+	if other == nil {
+		return existing
+	}
+	result = new(bool)
+	*result = *other
+	return result
+}
+
+func OverrideWithString(existing, other string) (result string) {
+	if other == "" {
+		return existing
+	}
+	return other
+}
+
+func OverrideWithStringPtr(existing, other *string) (result *string) {
+	if other == nil {
+		return existing
+	}
+	result = new(string)
+	*result = *other
+	return result
+}
+
+func OverrideWithInt(existing, other *int) (result *int) {
+	if other == nil {
+		return existing
+	}
+	result = new(int)
+	*result = *other
+	return result
+}
+
+func OverrideWithUint8(existing, other *uint8) (result *uint8) {
+	if other == nil {
+		return existing
+	}
+	result = new(uint8)
+	*result = *other
+	return result
+}
+
+func OverrideWithUint16(existing, other *uint16) (result *uint16) {
+	if other == nil {
+		return existing
+	}
+	result = new(uint16)
+	*result = *other
+	return result
+}
+
+func OverrideWithIP(existing, other net.IP) (result net.IP) {
+	if other == nil {
+		return existing
+	}
+	result = make(net.IP, len(other))
+	copy(result, other)
+	return result
+}
+
+func OverrideWithDuration(existing, other *time.Duration) (result *time.Duration) {
+	if other == nil {
+		return existing
+	}
+	result = new(time.Duration)
+	*result = *other
+	return result
+}
+
+func OverrideWithLogLevel(existing, other *logging.Level) (result *logging.Level) {
+	if other == nil {
+		return existing
+	}
+	result = new(logging.Level)
+	*result = *other
+	return result
+}
+
+func OverrideWithStringSlice(existing, other []string) (result []string) {
+	if other == nil {
+		return existing
+	}
+	result = make([]string, len(other))
+	copy(result, other)
+	return result
+}
+
+func OverrideWithUint16Slice(existing, other []uint16) (result []uint16) {
+	if other == nil {
+		return existing
+	}
+	result = make([]uint16, len(other))
+	copy(result, other)
+	return result
+}
+
+func OverrideWithIPNetsSlice(existing, other []net.IPNet) (result []net.IPNet) {
+	if other == nil {
+		return existing
+	}
+	result = make([]net.IPNet, len(other))
+	copy(result, other)
+	return result
+}
+
+func OverrideWithNetaddrIPsSlice(existing, other []netaddr.IP) (result []netaddr.IP) {
+	if other == nil {
+		return existing
+	}
+	result = make([]netaddr.IP, len(other))
+	copy(result, other)
+	return result
+}
+
+func OverrideWithIPPrefixesSlice(existing, other []netaddr.IPPrefix) (result []netaddr.IPPrefix) {
+	if other == nil {
+		return existing
+	}
+	result = make([]netaddr.IPPrefix, len(other))
+	copy(result, other)
+	return result
+}

internal/configuration/settings/helpers/pointers.go

@@ -0,0 +1,11 @@
+package helpers
+
+import "time"
+
+// StringPtr returns a pointer to the string value
+// passed as argument.
+func StringPtr(s string) *string { return &s }
+
+// DurationPtr returns a pointer to the duration value
+// passed as argument.
+func DurationPtr(d time.Duration) *time.Duration { return &d }

internal/configuration/settings/helpers/string.go

@@ -0,0 +1,15 @@
+package helpers
+
+func BoolPtrToYesNo(b *bool) string {
+	if *b {
+		return "yes"
+	}
+	return "no"
+}
+
+func TCPPtrToString(tcp *bool) string {
+	if *tcp {
+		return "TCP"
+	}
+	return "UDP"
+}

internal/configuration/settings/helpers_test.go

@@ -0,0 +1,4 @@
+package settings
+
+func boolPtr(b bool) *bool    { return &b }
+func uint8Ptr(n uint8) *uint8 { return &n }

internal/configuration/settings/httpproxy.go

@@ -0,0 +1,112 @@
+package settings
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+	"github.com/qdm12/govalid/address"
+)
+
+// HTTPProxy contains settings to configure the HTTP proxy.
+type HTTPProxy struct {
+	// User is the username to use for the HTTP proxy.
+	// It cannot be nil in the internal state.
+	User *string
+	// Password is the password to use for the HTTP proxy.
+	// It cannot be nil in the internal state.
+	Password *string
+	// ListeningAddress is the listening address
+	// of the HTTP proxy server.
+	// It cannot be the empty string in the internal state.
+	ListeningAddress string
+	// Enabled is true if the HTTP proxy server should run,
+	// and false otherwise. It cannot be nil in the
+	// internal state.
+	Enabled *bool
+	// Stealth is true if the HTTP proxy server should hide
+	// each request has been proxied to the destination.
+	// It cannot be nil in the internal state.
+	Stealth *bool
+	// Log is true if the HTTP proxy server should log
+	// each request/response. It cannot be nil in the
+	// internal state.
+	Log *bool
+}
+
+func (h HTTPProxy) validate() (err error) {
+	// Do not validate user and password
+
+	uid := os.Getuid()
+	_, err = address.Validate(h.ListeningAddress, address.OptionListening(uid))
+	if err != nil {
+		return fmt.Errorf("%w: %s",
+			ErrServerAddressNotValid, h.ListeningAddress)
+	}
+
+	return nil
+}
+
+func (h *HTTPProxy) copy() (copied HTTPProxy) {
+	return HTTPProxy{
+		User:             helpers.CopyStringPtr(h.User),
+		Password:         helpers.CopyStringPtr(h.Password),
+		ListeningAddress: h.ListeningAddress,
+		Enabled:          helpers.CopyBoolPtr(h.Enabled),
+		Stealth:          helpers.CopyBoolPtr(h.Stealth),
+		Log:              helpers.CopyBoolPtr(h.Log),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (h *HTTPProxy) mergeWith(other HTTPProxy) {
+	h.User = helpers.MergeWithStringPtr(h.User, other.User)
+	h.Password = helpers.MergeWithStringPtr(h.Password, other.Password)
+	h.ListeningAddress = helpers.MergeWithString(h.ListeningAddress, other.ListeningAddress)
+	h.Enabled = helpers.MergeWithBool(h.Enabled, other.Enabled)
+	h.Stealth = helpers.MergeWithBool(h.Stealth, other.Stealth)
+	h.Log = helpers.MergeWithBool(h.Log, other.Log)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (h *HTTPProxy) overrideWith(other HTTPProxy) {
+	h.User = helpers.OverrideWithStringPtr(h.User, other.User)
+	h.Password = helpers.OverrideWithStringPtr(h.Password, other.Password)
+	h.ListeningAddress = helpers.OverrideWithString(h.ListeningAddress, other.ListeningAddress)
+	h.Enabled = helpers.OverrideWithBool(h.Enabled, other.Enabled)
+	h.Stealth = helpers.OverrideWithBool(h.Stealth, other.Stealth)
+	h.Log = helpers.OverrideWithBool(h.Log, other.Log)
+}
+
+func (h *HTTPProxy) setDefaults() {
+	h.User = helpers.DefaultStringPtr(h.User, "")
+	h.Password = helpers.DefaultStringPtr(h.Password, "")
+	h.ListeningAddress = helpers.DefaultString(h.ListeningAddress, "")
+	h.Enabled = helpers.DefaultBool(h.Enabled, false)
+	h.Stealth = helpers.DefaultBool(h.Stealth, false)
+	h.Log = helpers.DefaultBool(h.Log, false)
+}
+
+func (h HTTPProxy) String() string {
+	return h.toLinesNode().String()
+}
+
+func (h HTTPProxy) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("HTTP proxy settings:")
+	node.Appendf("Enabled: %s", helpers.BoolPtrToYesNo(h.Enabled))
+	if !*h.Enabled {
+		return node
+	}
+
+	node.Appendf("Listening address: %s", h.ListeningAddress)
+	node.Appendf("User: %s", *h.User)
+	node.Appendf("Password: %s", helpers.ObfuscatePassword(*h.Password))
+	node.Appendf("Stealth mode: %s", helpers.BoolPtrToYesNo(h.Stealth))
+	node.Appendf("Log: %s", helpers.BoolPtrToYesNo(h.Log))
+
+	return node
+}

internal/configuration/settings/log.go

@@ -0,0 +1,51 @@
+package settings
+
+import (
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/golibs/logging"
+	"github.com/qdm12/gotree"
+)
+
+// Log contains settings to configure the logger.
+type Log struct {
+	// Level is the log level of the logger.
+	// It cannot be nil in the internal state.
+	Level *logging.Level
+}
+
+func (l Log) validate() (err error) {
+	return nil
+}
+
+func (l *Log) copy() (copied Log) {
+	return Log{
+		Level: helpers.CopyLogLevelPtr(l.Level),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (l *Log) mergeWith(other Log) {
+	l.Level = helpers.MergeWithLogLevel(l.Level, other.Level)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (l *Log) overrideWith(other Log) {
+	l.Level = helpers.OverrideWithLogLevel(l.Level, other.Level)
+}
+
+func (l *Log) setDefaults() {
+	l.Level = helpers.DefaultLogLevel(l.Level, logging.LevelInfo)
+}
+
+func (l Log) String() string {
+	return l.toLinesNode().String()
+}
+
+func (l Log) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Log settings:")
+	node.Appendf("Log level: %s", l.Level.String())
+	return node
+}

internal/configuration/settings/openvpn.go

@@ -0,0 +1,318 @@
+package settings
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/openvpn/parse"
+	"github.com/qdm12/gotree"
+)
+
+// OpenVPN contains settings to configure the OpenVPN client.
+type OpenVPN struct {
+	// Version is the OpenVPN version to run.
+	// It can only be "2.4" or "2.5".
+	Version string
+	// User is the OpenVPN authentication username.
+	// It cannot be an empty string in the internal state
+	// if OpenVPN is used.
+	User string
+	// Password is the OpenVPN authentication password.
+	// It cannot be an empty string in the internal state
+	// if OpenVPN is used.
+	Password string
+	// ConfFile is a custom OpenVPN configuration file path.
+	// It can be set to the empty string for it to be ignored.
+	// It cannot be nil in the internal state.
+	ConfFile *string
+	// Ciphers is a list of ciphers to use for OpenVPN,
+	// different from the ones specified by the VPN
+	// service provider configuration files.
+	Ciphers []string
+	// Auth is an auth algorithm to use in OpenVPN instead
+	// of the one specified by the VPN service provider.
+	// It cannot be nil in the internal state.
+	// It is ignored if it is set to the empty string.
+	Auth *string
+	// ClientCrt is the OpenVPN client certificate.
+	// This is notably used by Cyberghost.
+	// It can be set to the empty string to be ignored.
+	// It cannot be nil in the internal state.
+	ClientCrt *string
+	// ClientKey is the OpenVPN client key.
+	// This is used by Cyberghost and VPN Unlimited.
+	// It can be set to the empty string to be ignored.
+	// It cannot be nil in the internal state.
+	ClientKey *string
+	// PIAEncPreset is the encryption preset for
+	// Private Internet Access. It can be set to an
+	// empty string for other providers.
+	PIAEncPreset *string
+	// IPv6 is set to true if IPv6 routing should be
+	// set to be tunnel in OpenVPN, and false otherwise.
+	// It cannot be nil in the internal state.
+	IPv6 *bool // TODO automate like with Wireguard
+	// MSSFix is the value (1 to 10000) to set for the
+	// mssfix option for OpenVPN. It is ignored if set to 0.
+	// It cannot be nil in the internal state.
+	MSSFix *uint16
+	// Interface is the OpenVPN device interface name.
+	// It cannot be an empty string in the internal state.
+	Interface string
+	// Root is true if OpenVPN is to be run as root,
+	// and false otherwise. It cannot be nil in the
+	// internal state.
+	Root *bool
+	// ProcUser is the OpenVPN process OS username
+	// to use. It cannot be nil in the internal state.
+	// This is set and injected at runtime.
+	// TODO only use ProcUser and not Root field.
+	ProcUser string
+	// Verbosity is the OpenVPN verbosity level from 0 to 6.
+	// It cannot be nil in the internal state.
+	Verbosity *int
+	// Flags is a slice of additional flags to be passed
+	// to the OpenVPN program.
+	Flags []string
+}
+
+func (o OpenVPN) validate(vpnProvider string) (err error) {
+	// Validate version
+	validVersions := []string{constants.Openvpn24, constants.Openvpn25}
+	if !helpers.IsOneOf(o.Version, validVersions...) {
+		return fmt.Errorf("%w: %q can only be one of %s",
+			ErrOpenVPNVersionIsNotValid, o.Version, strings.Join(validVersions, ", "))
+	}
+
+	if o.User == "" {
+		return ErrOpenVPNUserIsEmpty
+	}
+
+	if o.Password == "" {
+		return ErrOpenVPNPasswordIsEmpty
+	}
+
+	// Validate ConfFile
+	if vpnProvider == constants.Custom {
+		if *o.ConfFile == "" {
+			return fmt.Errorf("%w: no file path specified", ErrOpenVPNConfigFile)
+		}
+		err := helpers.FileExists(*o.ConfFile)
+		if err != nil {
+			return fmt.Errorf("%w: %s", ErrOpenVPNConfigFile, err)
+		}
+	}
+
+	// Check client certificate
+	switch vpnProvider {
+	case
+		constants.Cyberghost,
+		constants.VPNUnlimited:
+		if *o.ClientCrt == "" {
+			return ErrOpenVPNClientCertMissing
+		}
+	}
+	if *o.ClientCrt != "" {
+		_, err = parse.ExtractCert([]byte(*o.ClientCrt))
+		if err != nil {
+			return fmt.Errorf("%w: %s", ErrOpenVPNClientCertNotValid, err)
+		}
+	}
+
+	// Check client key
+	switch vpnProvider {
+	case
+		constants.Cyberghost,
+		constants.VPNUnlimited,
+		constants.Wevpn:
+		if *o.ClientKey == "" {
+			return ErrOpenVPNClientKeyMissing
+		}
+	}
+	if *o.ClientKey != "" {
+		_, err = parse.ExtractPrivateKey([]byte(*o.ClientKey))
+		if err != nil {
+			return fmt.Errorf("%w: %s", ErrOpenVPNClientKeyNotValid, err)
+		}
+	}
+
+	// Validate MSSFix
+	const maxMSSFix = 10000
+	if *o.MSSFix > maxMSSFix {
+		return fmt.Errorf("%w: %d is over the maximum value of %d",
+			ErrOpenVPNMSSFixIsTooHigh, *o.MSSFix, maxMSSFix)
+	}
+
+	if !regexpInterfaceName.MatchString(o.Interface) {
+		return fmt.Errorf("%w: '%s' does not match regex '%s'",
+			ErrOpenVPNInterfaceNotValid, o.Interface, regexpInterfaceName)
+	}
+
+	// Validate Verbosity
+	if *o.Verbosity < 0 || *o.Verbosity > 6 {
+		return fmt.Errorf("%w: %d can only be between 0 and 5",
+			ErrOpenVPNVerbosityIsOutOfBounds, o.Verbosity)
+	}
+
+	return nil
+}
+
+func (o *OpenVPN) copy() (copied OpenVPN) {
+	return OpenVPN{
+		Version:      o.Version,
+		User:         o.User,
+		Password:     o.Password,
+		ConfFile:     helpers.CopyStringPtr(o.ConfFile),
+		Ciphers:      helpers.CopyStringSlice(o.Ciphers),
+		Auth:         helpers.CopyStringPtr(o.Auth),
+		ClientCrt:    helpers.CopyStringPtr(o.ClientCrt),
+		ClientKey:    helpers.CopyStringPtr(o.ClientKey),
+		PIAEncPreset: helpers.CopyStringPtr(o.PIAEncPreset),
+		IPv6:         helpers.CopyBoolPtr(o.IPv6),
+		MSSFix:       helpers.CopyUint16Ptr(o.MSSFix),
+		Interface:    o.Interface,
+		Root:         helpers.CopyBoolPtr(o.Root),
+		ProcUser:     o.ProcUser,
+		Verbosity:    helpers.CopyIntPtr(o.Verbosity),
+		Flags:        helpers.CopyStringSlice(o.Flags),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (o *OpenVPN) mergeWith(other OpenVPN) {
+	o.Version = helpers.MergeWithString(o.Version, other.Version)
+	o.User = helpers.MergeWithString(o.User, other.User)
+	o.Password = helpers.MergeWithString(o.Password, other.Password)
+	o.ConfFile = helpers.MergeWithStringPtr(o.ConfFile, other.ConfFile)
+	o.Ciphers = helpers.MergeStringSlices(o.Ciphers, other.Ciphers)
+	o.Auth = helpers.MergeWithStringPtr(o.Auth, other.Auth)
+	o.ClientCrt = helpers.MergeWithStringPtr(o.ClientCrt, other.ClientCrt)
+	o.ClientKey = helpers.MergeWithStringPtr(o.ClientKey, other.ClientKey)
+	o.PIAEncPreset = helpers.MergeWithStringPtr(o.PIAEncPreset, other.PIAEncPreset)
+	o.IPv6 = helpers.MergeWithBool(o.IPv6, other.IPv6)
+	o.MSSFix = helpers.MergeWithUint16(o.MSSFix, other.MSSFix)
+	o.Interface = helpers.MergeWithString(o.Interface, other.Interface)
+	o.Root = helpers.MergeWithBool(o.Root, other.Root)
+	o.ProcUser = helpers.MergeWithString(o.ProcUser, other.ProcUser)
+	o.Verbosity = helpers.MergeWithInt(o.Verbosity, other.Verbosity)
+	o.Flags = helpers.MergeStringSlices(o.Flags, other.Flags)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (o *OpenVPN) overrideWith(other OpenVPN) {
+	o.Version = helpers.OverrideWithString(o.Version, other.Version)
+	o.User = helpers.OverrideWithString(o.User, other.User)
+	o.Password = helpers.OverrideWithString(o.Password, other.Password)
+	o.ConfFile = helpers.OverrideWithStringPtr(o.ConfFile, other.ConfFile)
+	o.Ciphers = helpers.OverrideWithStringSlice(o.Ciphers, other.Ciphers)
+	o.Auth = helpers.OverrideWithStringPtr(o.Auth, other.Auth)
+	o.ClientCrt = helpers.OverrideWithStringPtr(o.ClientCrt, other.ClientCrt)
+	o.ClientKey = helpers.OverrideWithStringPtr(o.ClientKey, other.ClientKey)
+	o.PIAEncPreset = helpers.OverrideWithStringPtr(o.PIAEncPreset, other.PIAEncPreset)
+	o.IPv6 = helpers.OverrideWithBool(o.IPv6, other.IPv6)
+	o.MSSFix = helpers.OverrideWithUint16(o.MSSFix, other.MSSFix)
+	o.Interface = helpers.OverrideWithString(o.Interface, other.Interface)
+	o.Root = helpers.OverrideWithBool(o.Root, other.Root)
+	o.ProcUser = helpers.OverrideWithString(o.ProcUser, other.ProcUser)
+	o.Verbosity = helpers.OverrideWithInt(o.Verbosity, other.Verbosity)
+	o.Flags = helpers.OverrideWithStringSlice(o.Flags, other.Flags)
+}
+
+func (o *OpenVPN) setDefaults(vpnProvider string) {
+	o.Version = helpers.DefaultString(o.Version, constants.Openvpn25)
+	if vpnProvider == constants.Mullvad {
+		o.Password = "m"
+	}
+
+	o.ConfFile = helpers.DefaultStringPtr(o.ConfFile, "")
+	o.Auth = helpers.DefaultStringPtr(o.Auth, "")
+	o.ClientCrt = helpers.DefaultStringPtr(o.ClientCrt, "")
+	o.ClientKey = helpers.DefaultStringPtr(o.ClientKey, "")
+
+	var defaultEncPreset string
+	if vpnProvider == constants.PrivateInternetAccess {
+		defaultEncPreset = constants.PIAEncryptionPresetStrong
+	}
+	o.PIAEncPreset = helpers.DefaultStringPtr(o.PIAEncPreset, defaultEncPreset)
+
+	o.IPv6 = helpers.DefaultBool(o.IPv6, false)
+	o.MSSFix = helpers.DefaultUint16(o.MSSFix, 0)
+	o.Interface = helpers.DefaultString(o.Interface, "tun0")
+	o.Root = helpers.DefaultBool(o.Root, true)
+	o.ProcUser = helpers.DefaultString(o.ProcUser, "root")
+	o.Verbosity = helpers.DefaultInt(o.Verbosity, 1)
+}
+
+func (o OpenVPN) String() string {
+	return o.toLinesNode().String()
+}
+
+func (o OpenVPN) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("OpenVPN server selection settings:")
+	node.Appendf("OpenVPN version: %s", o.Version)
+	node.Appendf("User: %s", helpers.ObfuscatePassword(o.User))
+	node.Appendf("Password: %s", helpers.ObfuscatePassword(o.Password))
+
+	if *o.ConfFile != "" {
+		node.Appendf("Custom configuration file: %s", *o.ConfFile)
+	}
+
+	if len(o.Ciphers) > 0 {
+		node.Appendf("Ciphers: %s", o.Ciphers)
+	}
+
+	if *o.Auth != "" {
+		node.Appendf("Auth: %s", *o.Auth)
+	}
+
+	if *o.ClientCrt != "" {
+		node.Appendf("Client crt: %s", helpers.ObfuscateData(*o.ClientCrt))
+	}
+
+	if *o.ClientKey != "" {
+		node.Appendf("Client key: %s", helpers.ObfuscateData(*o.ClientKey))
+	}
+
+	if *o.PIAEncPreset != "" {
+		node.Appendf("Private Internet Access encryption preset: %s", *o.PIAEncPreset)
+	}
+
+	node.Appendf("Tunnel IPv6: %s", helpers.BoolPtrToYesNo(o.IPv6))
+
+	if *o.MSSFix > 0 {
+		node.Appendf("MSS Fix: %d", *o.MSSFix)
+	}
+
+	if o.Interface != "" {
+		node.Appendf("Network interface: %s", o.Interface)
+	}
+
+	processUser := "root"
+	if !*o.Root {
+		processUser = "some non root user" // TODO
+		if o.ProcUser != "" {
+			processUser = o.ProcUser
+		}
+	}
+	node.Appendf("Run OpenVPN as: %s", processUser)
+
+	node.Appendf("Verbosity level: %d", *o.Verbosity)
+
+	if len(o.Flags) > 0 {
+		node.Appendf("Flags: %s", o.Flags)
+	}
+
+	return node
+}
+
+// WithDefaults is a shorthand using setDefaults.
+// It's used in unit tests in other packages.
+func (o OpenVPN) WithDefaults(provider string) OpenVPN {
+	o.setDefaults(provider)
+	return o
+}

internal/configuration/settings/openvpnselection.go

@@ -0,0 +1,170 @@
+package settings
+
+import (
+	"fmt"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gotree"
+)
+
+type OpenVPNSelection struct {
+	// ConfFile is the custom configuration file path.
+	// It can be set to an empty string to indicate to
+	// NOT use a custom configuration file.
+	// It cannot be nil in the internal state.
+	ConfFile *string
+	// TCP is true if the OpenVPN protocol is TCP,
+	// and false for UDP.
+	// It cannot be nil in the internal state.
+	TCP *bool
+	// CustomPort is the OpenVPN server endpoint port.
+	// It can be set to 0 to indicate no custom port should
+	// be used. It cannot be nil in the internal state.
+	CustomPort *uint16 // HideMyAss, Mullvad, PIA, ProtonVPN, WeVPN, Windscribe
+	// PIAEncPreset is the encryption preset for
+	// Private Internet Access. It can be set to an
+	// empty string for other providers.
+	PIAEncPreset *string
+}
+
+func (o OpenVPNSelection) validate(vpnProvider string) (err error) {
+	// Validate ConfFile
+	if confFile := *o.ConfFile; confFile != "" {
+		err := helpers.FileExists(confFile)
+		if err != nil {
+			return fmt.Errorf("%w: %s", ErrOpenVPNConfigFile, err)
+		}
+	}
+
+	// Validate TCP
+	if *o.TCP && helpers.IsOneOf(vpnProvider,
+		constants.Perfectprivacy,
+		constants.Privado,
+		constants.Vyprvpn,
+	) {
+		return fmt.Errorf("%w: for VPN service provider %s",
+			ErrOpenVPNTCPNotSupported, vpnProvider)
+	}
+
+	// Validate CustomPort
+	if *o.CustomPort != 0 {
+		switch vpnProvider {
+		// no restriction on port
+		case constants.Cyberghost, constants.HideMyAss,
+			constants.PrivateInternetAccess, constants.Privatevpn,
+			constants.Protonvpn, constants.Torguard:
+		// no custom port allowed
+		case constants.Expressvpn, constants.Fastestvpn,
+			constants.Ipvanish, constants.Nordvpn,
+			constants.Privado, constants.Purevpn,
+			constants.Surfshark, constants.VPNUnlimited,
+			constants.Vyprvpn:
+			return fmt.Errorf("%w: for VPN service provider %s",
+				ErrOpenVPNCustomPortNotAllowed, vpnProvider)
+		default:
+			var allowedTCP, allowedUDP []uint16
+			switch vpnProvider {
+			case constants.Ivpn:
+				allowedTCP = []uint16{80, 443, 1143}
+				allowedUDP = []uint16{53, 1194, 2049, 2050}
+			case constants.Mullvad:
+				allowedTCP = []uint16{80, 443, 1401}
+				allowedUDP = []uint16{53, 1194, 1195, 1196, 1197, 1300, 1301, 1302, 1303, 1400}
+			case constants.Perfectprivacy:
+				allowedTCP = []uint16{44, 443, 4433}
+				allowedUDP = []uint16{44, 443, 4433}
+			case constants.Wevpn:
+				allowedTCP = []uint16{53, 1195, 1199, 2018}
+				allowedUDP = []uint16{80, 1194, 1198}
+			case constants.Windscribe:
+				allowedTCP = []uint16{21, 22, 80, 123, 143, 443, 587, 1194, 3306, 8080, 54783}
+				allowedUDP = []uint16{53, 80, 123, 443, 1194, 54783}
+			}
+
+			if *o.TCP && !helpers.Uint16IsOneOf(*o.CustomPort, allowedTCP) {
+				return fmt.Errorf("%w: %d for VPN service provider %s; %s",
+					ErrOpenVPNCustomPortNotAllowed, o.CustomPort, vpnProvider,
+					helpers.PortChoicesOrString(allowedTCP))
+			} else if !*o.TCP && !helpers.Uint16IsOneOf(*o.CustomPort, allowedUDP) {
+				return fmt.Errorf("%w: %d for VPN service provider %s; %s",
+					ErrOpenVPNCustomPortNotAllowed, o.CustomPort, vpnProvider,
+					helpers.PortChoicesOrString(allowedUDP))
+			}
+		}
+	}
+
+	// Validate EncPreset
+	if vpnProvider == constants.PrivateInternetAccess {
+		validEncryptionPresets := []string{
+			constants.PIAEncryptionPresetNone,
+			constants.PIAEncryptionPresetNormal,
+			constants.PIACertificateStrong,
+		}
+		if !helpers.IsOneOf(*o.PIAEncPreset, validEncryptionPresets...) {
+			return fmt.Errorf("%w: %s; valid presets are %s",
+				ErrOpenVPNEncryptionPresetNotValid, *o.PIAEncPreset,
+				helpers.ChoicesOrString(validEncryptionPresets))
+		}
+	}
+
+	return nil
+}
+
+func (o *OpenVPNSelection) copy() (copied OpenVPNSelection) {
+	return OpenVPNSelection{
+		ConfFile:     helpers.CopyStringPtr(o.ConfFile),
+		TCP:          helpers.CopyBoolPtr(o.TCP),
+		CustomPort:   helpers.CopyUint16Ptr(o.CustomPort),
+		PIAEncPreset: helpers.CopyStringPtr(o.PIAEncPreset),
+	}
+}
+
+func (o *OpenVPNSelection) mergeWith(other OpenVPNSelection) {
+	o.ConfFile = helpers.MergeWithStringPtr(o.ConfFile, other.ConfFile)
+	o.TCP = helpers.MergeWithBool(o.TCP, other.TCP)
+	o.CustomPort = helpers.MergeWithUint16(o.CustomPort, other.CustomPort)
+	o.PIAEncPreset = helpers.MergeWithStringPtr(o.PIAEncPreset, other.PIAEncPreset)
+}
+
+func (o *OpenVPNSelection) overrideWith(other OpenVPNSelection) {
+	o.ConfFile = helpers.OverrideWithStringPtr(o.ConfFile, other.ConfFile)
+	o.TCP = helpers.OverrideWithBool(o.TCP, other.TCP)
+	o.CustomPort = helpers.OverrideWithUint16(o.CustomPort, other.CustomPort)
+	o.PIAEncPreset = helpers.OverrideWithStringPtr(o.PIAEncPreset, other.PIAEncPreset)
+}
+
+func (o *OpenVPNSelection) setDefaults(vpnProvider string) {
+	o.ConfFile = helpers.DefaultStringPtr(o.ConfFile, "")
+	o.TCP = helpers.DefaultBool(o.TCP, false)
+	o.CustomPort = helpers.DefaultUint16(o.CustomPort, 0)
+
+	var defaultEncPreset string
+	if vpnProvider == constants.PrivateInternetAccess {
+		defaultEncPreset = constants.PIAEncryptionPresetStrong
+	}
+	o.PIAEncPreset = helpers.DefaultStringPtr(o.PIAEncPreset, defaultEncPreset)
+}
+
+func (o OpenVPNSelection) String() string {
+	return o.toLinesNode().String()
+}
+
+func (o OpenVPNSelection) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("OpenVPN server selection settings:")
+	node.Appendf("Protocol: %s", helpers.TCPPtrToString(o.TCP))
+
+	if *o.CustomPort != 0 {
+		node.Appendf("Custom port: %d", *o.CustomPort)
+	}
+
+	if *o.PIAEncPreset != "" {
+		node.Appendf("Private Internet Access encryption preset: %s", *o.PIAEncPreset)
+	}
+
+	if *o.ConfFile != "" {
+		node.Appendf("Custom configuration file: %s", *o.ConfFile)
+	}
+
+	return node
+}

internal/configuration/settings/portforward.go

@@ -0,0 +1,89 @@
+package settings
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gotree"
+)
+
+// PortForwarding contains settings for port forwarding.
+type PortForwarding struct {
+	// Enabled is true if port forwarding should be activated.
+	// It cannot be nil for the internal state.
+	Enabled *bool
+	// Filepath is the port forwarding status file path
+	// to use. It can be the empty string to indicate not
+	// to write to a file. It cannot be nil for the
+	// internal state
+	Filepath *string
+}
+
+func (p PortForwarding) validate(vpnProvider string) (err error) {
+	if !*p.Enabled {
+		return nil
+	}
+
+	// Validate Enabled
+	validProviders := []string{constants.PrivateInternetAccess}
+	if !helpers.IsOneOf(vpnProvider, validProviders...) {
+		return fmt.Errorf("%w: for provider %s, it is only available for %s",
+			ErrPortForwardingEnabled, vpnProvider, strings.Join(validProviders, ", "))
+	}
+
+	// Validate Filepath
+	if *p.Filepath != "" { // optional
+		_, err := filepath.Abs(*p.Filepath)
+		if err != nil {
+			return fmt.Errorf("%w: %s", ErrPortForwardingFilepathNotValid, err)
+		}
+	}
+
+	return nil
+}
+
+func (p *PortForwarding) copy() (copied PortForwarding) {
+	return PortForwarding{
+		Enabled:  helpers.CopyBoolPtr(p.Enabled),
+		Filepath: helpers.CopyStringPtr(p.Filepath),
+	}
+}
+
+func (p *PortForwarding) mergeWith(other PortForwarding) {
+	p.Enabled = helpers.MergeWithBool(p.Enabled, other.Enabled)
+	p.Filepath = helpers.MergeWithStringPtr(p.Filepath, other.Filepath)
+}
+
+func (p *PortForwarding) overrideWith(other PortForwarding) {
+	p.Enabled = helpers.OverrideWithBool(p.Enabled, other.Enabled)
+	p.Filepath = helpers.OverrideWithStringPtr(p.Filepath, other.Filepath)
+}
+
+func (p *PortForwarding) setDefaults() {
+	p.Enabled = helpers.DefaultBool(p.Enabled, false)
+	p.Filepath = helpers.DefaultStringPtr(p.Filepath, "/tmp/gluetun/forwarded_port")
+}
+
+func (p PortForwarding) String() string {
+	return p.toLinesNode().String()
+}
+
+func (p PortForwarding) toLinesNode() (node *gotree.Node) {
+	if !*p.Enabled {
+		return nil
+	}
+
+	node = gotree.New("Automatic port forwarding settings:")
+	node.Appendf("Enabled: yes")
+
+	filepath := *p.Filepath
+	if filepath == "" {
+		filepath = "[not set]"
+	}
+	node.Appendf("Forwarded port file path: %s", filepath)
+
+	return node
+}

internal/configuration/settings/portforward_test.go

@@ -0,0 +1,19 @@
+package settings
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_PortForwarding_String(t *testing.T) {
+	t.Parallel()
+
+	settings := PortForwarding{
+		Enabled: boolPtr(false),
+	}
+
+	s := settings.String()
+
+	assert.Empty(t, s)
+}

internal/configuration/settings/provider.go

@@ -0,0 +1,92 @@
+package settings
+
+import (
+	"fmt"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gotree"
+)
+
+// Provider contains settings specific to a VPN provider.
+type Provider struct {
+	// Name is the VPN service provider name.
+	// It cannot be nil in the internal state.
+	Name *string
+	// ServerSelection is the settings to
+	// select the VPN server.
+	ServerSelection ServerSelection
+	// PortForwarding is the settings about port forwarding.
+	PortForwarding PortForwarding
+}
+
+func (p Provider) validate(vpnType string, allServers models.AllServers) (err error) {
+	// Validate Name
+	var validNames []string
+	if vpnType == constants.OpenVPN {
+		validNames = constants.AllProviders()
+		validNames = append(validNames, "pia") // Retro-compatibility
+	} else { // Wireguard
+		validNames = []string{
+			constants.Custom,
+			constants.Ivpn,
+			constants.Mullvad,
+			constants.Windscribe,
+		}
+	}
+	if !helpers.IsOneOf(*p.Name, validNames...) {
+		return fmt.Errorf("%w: %q can only be one of %s",
+			ErrVPNProviderNameNotValid, *p.Name, helpers.ChoicesOrString(validNames))
+	}
+
+	err = p.ServerSelection.validate(*p.Name, allServers)
+	if err != nil {
+		return fmt.Errorf("server selection settings validation failed: %w", err)
+	}
+
+	err = p.PortForwarding.validate(*p.Name)
+	if err != nil {
+		return fmt.Errorf("port forwarding settings validation failed: %w", err)
+	}
+
+	return nil
+}
+
+func (p *Provider) copy() (copied Provider) {
+	return Provider{
+		Name:            helpers.CopyStringPtr(p.Name),
+		ServerSelection: p.ServerSelection.copy(),
+		PortForwarding:  p.PortForwarding.copy(),
+	}
+}
+
+func (p *Provider) mergeWith(other Provider) {
+	p.Name = helpers.MergeWithStringPtr(p.Name, other.Name)
+	p.ServerSelection.mergeWith(other.ServerSelection)
+	p.PortForwarding.mergeWith(other.PortForwarding)
+}
+
+func (p *Provider) overrideWith(other Provider) {
+	p.Name = helpers.OverrideWithStringPtr(p.Name, other.Name)
+	p.ServerSelection.overrideWith(other.ServerSelection)
+	p.PortForwarding.overrideWith(other.PortForwarding)
+}
+
+func (p *Provider) setDefaults() {
+	p.Name = helpers.DefaultStringPtr(p.Name, constants.PrivateInternetAccess)
+	p.ServerSelection.setDefaults(*p.Name)
+	p.PortForwarding.setDefaults()
+}
+
+func (p Provider) String() string {
+	return p.toLinesNode().String()
+}
+
+func (p Provider) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("VPN provider settings:")
+	node.Appendf("Name: %s", *p.Name)
+	node.AppendNode(p.ServerSelection.toLinesNode())
+	node.AppendNode(p.PortForwarding.toLinesNode())
+	return node
+}

internal/configuration/settings/publicip.go

@@ -0,0 +1,89 @@
+package settings
+
+import (
+	"fmt"
+	"path/filepath"
+	"time"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+// PublicIP contains settings for port forwarding.
+type PublicIP struct {
+	// Period is the period to get the public IP address.
+	// It can be set to 0 to disable periodic checking.
+	// It cannot be nil for the internal state.
+	// TODO change to value and add enabled field
+	Period *time.Duration
+	// IPFilepath is the public IP address status file path
+	// to use. It can be the empty string to indicate not
+	// to write to a file. It cannot be nil for the
+	// internal state
+	IPFilepath *string
+}
+
+func (p PublicIP) validate() (err error) {
+	const minPeriod = 5 * time.Second
+	if *p.Period < minPeriod {
+		return fmt.Errorf("%w: %s must be at least %s",
+			ErrPublicIPPeriodTooShort, p.Period, minPeriod)
+	}
+
+	if *p.IPFilepath != "" { // optional
+		_, err := filepath.Abs(*p.IPFilepath)
+		if err != nil {
+			return fmt.Errorf("%w: %s", ErrPublicIPFilepathNotValid, err)
+		}
+	}
+
+	return nil
+}
+
+func (p *PublicIP) copy() (copied PublicIP) {
+	return PublicIP{
+		Period:     helpers.CopyDurationPtr(p.Period),
+		IPFilepath: helpers.CopyStringPtr(p.IPFilepath),
+	}
+}
+
+func (p *PublicIP) mergeWith(other PublicIP) {
+	p.Period = helpers.MergeWithDuration(p.Period, other.Period)
+	p.IPFilepath = helpers.MergeWithStringPtr(p.IPFilepath, other.IPFilepath)
+}
+
+func (p *PublicIP) overrideWith(other PublicIP) {
+	p.Period = helpers.OverrideWithDuration(p.Period, other.Period)
+	p.IPFilepath = helpers.OverrideWithStringPtr(p.IPFilepath, other.IPFilepath)
+}
+
+func (p *PublicIP) setDefaults() {
+	const defaultPeriod = 12 * time.Hour
+	p.Period = helpers.DefaultDuration(p.Period, defaultPeriod)
+	p.IPFilepath = helpers.DefaultStringPtr(p.IPFilepath, "/tmp/gluetun/ip")
+}
+
+func (p PublicIP) String() string {
+	return p.toLinesNode().String()
+}
+
+func (p PublicIP) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Public IP settings:")
+
+	if *p.Period == 0 {
+		node.Appendf("Enabled: no")
+		return node
+	}
+
+	updatePeriod := "disabled"
+	if *p.Period > 0 {
+		updatePeriod = "every " + p.Period.String()
+	}
+	node.Appendf("Fetching: %s", updatePeriod)
+
+	if *p.IPFilepath != "" {
+		node.Appendf("IP file path: %s", *p.IPFilepath)
+	}
+
+	return node
+}

internal/configuration/settings/server.go

@@ -0,0 +1,71 @@
+package settings
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+// ControlServer contains settings to customize the control server operation.
+type ControlServer struct {
+	// Port is the listening port to use.
+	// It can be set to 0 to bind to a random port.
+	// It cannot be nil in the internal state.
+	// TODO change to address
+	Port *uint16
+	// Log can be true or false to enable logging on requests.
+	// It cannot be nil in the internal state.
+	Log *bool
+}
+
+func (c ControlServer) validate() (err error) {
+	uid := os.Getuid()
+	const maxPrivilegedPort uint16 = 1023
+	if uid != 0 && *c.Port <= maxPrivilegedPort {
+		return fmt.Errorf("%w: %d when running with user ID %d",
+			ErrControlServerPrivilegedPort, *c.Port, uid)
+	}
+
+	return nil
+}
+
+func (c *ControlServer) copy() (copied ControlServer) {
+	return ControlServer{
+		Port: helpers.CopyUint16Ptr(c.Port),
+		Log:  helpers.CopyBoolPtr(c.Log),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (c *ControlServer) mergeWith(other ControlServer) {
+	c.Port = helpers.MergeWithUint16(c.Port, other.Port)
+	c.Log = helpers.MergeWithBool(c.Log, other.Log)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (c *ControlServer) overrideWith(other ControlServer) {
+	c.Port = helpers.MergeWithUint16(c.Port, other.Port)
+	c.Log = helpers.MergeWithBool(c.Log, other.Log)
+}
+
+func (c *ControlServer) setDefaults() {
+	const defaultPort = 8000
+	c.Port = helpers.DefaultUint16(c.Port, defaultPort)
+	c.Log = helpers.DefaultBool(c.Log, true)
+}
+
+func (c ControlServer) String() string {
+	return c.toLinesNode().String()
+}
+
+func (c ControlServer) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Control server settings:")
+	node.Appendf("Listening port: %d", *c.Port)
+	node.Appendf("Logging: %s", helpers.BoolPtrToYesNo(c.Log))
+	return node
+}

internal/configuration/settings/serverselection.go

@@ -0,0 +1,386 @@
+package settings
+
+import (
+	"fmt"
+	"net"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gotree"
+)
+
+type ServerSelection struct { //nolint:maligned
+	// VPN is the VPN type which can be 'openvpn'
+	// or 'wireguard'. It cannot be the empty string
+	// in the internal state.
+	VPN string
+	// TargetIP is the server endpoint IP address to use.
+	// It will override any IP address from the picked
+	// built-in server. It cannot be nil in the internal
+	// state, and can be set to an empty net.IP{} to indicate
+	// there is not target IP address to use.
+	TargetIP net.IP
+	// Counties is the list of countries to filter VPN servers with.
+	Countries []string
+	// Regions is the list of regions to filter VPN servers with.
+	Regions []string
+	// Cities is the list of cities to filter VPN servers with.
+	Cities []string
+	// ISPs is the list of ISP names to filter VPN servers with.
+	ISPs []string
+	// Names is the list of server names to filter VPN servers with.
+	Names []string
+	// Numbers is the list of server numbers to filter VPN servers with.
+	Numbers []uint16
+	// Hostnames is the list of hostnames to filter VPN servers with.
+	Hostnames []string
+	// OwnedOnly is true if only VPN provider owned servers
+	// should be filtered. This is used with Mullvad.
+	OwnedOnly *bool
+	// FreeOnly is true if only free VPN servers
+	// should be filtered. This is used with ProtonVPN.
+	FreeOnly *bool
+	// FreeOnly is true if only free VPN servers
+	// should be filtered. This is used with ProtonVPN.
+	StreamOnly *bool
+	// MultiHopOnly is true if only multihop VPN servers
+	// should be filtered. This is used with Surfshark.
+	MultiHopOnly *bool
+
+	// OpenVPN contains settings to select OpenVPN servers
+	// and the final connection.
+	OpenVPN OpenVPNSelection
+	// Wireguard contains settings to select Wireguard servers
+	// and the final connection.
+	Wireguard WireguardSelection
+}
+
+func (ss *ServerSelection) validate(vpnServiceProvider string,
+	allServers models.AllServers) (err error) {
+	switch ss.VPN {
+	case constants.OpenVPN, constants.Wireguard:
+	default:
+		return fmt.Errorf("%w: %s", ErrVPNTypeNotValid, ss.VPN)
+	}
+
+	var countryChoices, regionChoices, cityChoices,
+		ispChoices, nameChoices, hostnameChoices []string
+	switch vpnServiceProvider {
+	case constants.Cyberghost:
+		servers := allServers.GetCyberghost()
+		countryChoices = constants.CyberghostCountryChoices(servers)
+		hostnameChoices = constants.CyberghostHostnameChoices(servers)
+	case constants.Expressvpn:
+		servers := allServers.GetExpressvpn()
+		countryChoices = constants.ExpressvpnCountriesChoices(servers)
+		cityChoices = constants.ExpressvpnCityChoices(servers)
+		hostnameChoices = constants.ExpressvpnHostnameChoices(servers)
+	case constants.Fastestvpn:
+		servers := allServers.GetFastestvpn()
+		countryChoices = constants.FastestvpnCountriesChoices(servers)
+		hostnameChoices = constants.FastestvpnHostnameChoices(servers)
+	case constants.HideMyAss:
+		servers := allServers.GetHideMyAss()
+		countryChoices = constants.HideMyAssCountryChoices(servers)
+		regionChoices = constants.HideMyAssRegionChoices(servers)
+		cityChoices = constants.HideMyAssCityChoices(servers)
+		hostnameChoices = constants.HideMyAssHostnameChoices(servers)
+	case constants.Ipvanish:
+		servers := allServers.GetIpvanish()
+		countryChoices = constants.IpvanishCountryChoices(servers)
+		cityChoices = constants.IpvanishCityChoices(servers)
+		hostnameChoices = constants.IpvanishHostnameChoices(servers)
+	case constants.Ivpn:
+		servers := allServers.GetIvpn()
+		countryChoices = constants.IvpnCountryChoices(servers)
+		cityChoices = constants.IvpnCityChoices(servers)
+		ispChoices = constants.IvpnISPChoices(servers)
+		hostnameChoices = constants.IvpnHostnameChoices(servers)
+	case constants.Mullvad:
+		servers := allServers.GetMullvad()
+		countryChoices = constants.MullvadCountryChoices(servers)
+		cityChoices = constants.MullvadCityChoices(servers)
+		ispChoices = constants.MullvadISPChoices(servers)
+		hostnameChoices = constants.MullvadHostnameChoices(servers)
+	case constants.Nordvpn:
+		servers := allServers.GetNordvpn()
+		regionChoices = constants.NordvpnRegionChoices(servers)
+		hostnameChoices = constants.NordvpnHostnameChoices(servers)
+	case constants.Perfectprivacy:
+		servers := allServers.GetPerfectprivacy()
+		cityChoices = constants.PerfectprivacyCityChoices(servers)
+	case constants.Privado:
+		servers := allServers.GetPrivado()
+		countryChoices = constants.PrivadoCountryChoices(servers)
+		regionChoices = constants.PrivadoRegionChoices(servers)
+		cityChoices = constants.PrivadoCityChoices(servers)
+		hostnameChoices = constants.PrivadoHostnameChoices(servers)
+	case constants.PrivateInternetAccess:
+		servers := allServers.GetPia()
+		regionChoices = constants.PIAGeoChoices(servers)
+		hostnameChoices = constants.PIAHostnameChoices(servers)
+		nameChoices = constants.PIANameChoices(servers)
+	case constants.Privatevpn:
+		servers := allServers.GetPrivatevpn()
+		countryChoices = constants.PrivatevpnCountryChoices(servers)
+		cityChoices = constants.PrivatevpnCityChoices(servers)
+		hostnameChoices = constants.PrivatevpnHostnameChoices(servers)
+	case constants.Protonvpn:
+		servers := allServers.GetProtonvpn()
+		countryChoices = constants.ProtonvpnCountryChoices(servers)
+		regionChoices = constants.ProtonvpnRegionChoices(servers)
+		cityChoices = constants.ProtonvpnCityChoices(servers)
+		nameChoices = constants.ProtonvpnNameChoices(servers)
+		hostnameChoices = constants.ProtonvpnHostnameChoices(servers)
+	case constants.Purevpn:
+		servers := allServers.GetPurevpn()
+		countryChoices = constants.PurevpnCountryChoices(servers)
+		regionChoices = constants.PurevpnRegionChoices(servers)
+		cityChoices = constants.PurevpnCityChoices(servers)
+		hostnameChoices = constants.PurevpnHostnameChoices(servers)
+	case constants.Surfshark:
+		servers := allServers.GetSurfshark()
+		countryChoices = constants.SurfsharkCountryChoices(servers)
+		cityChoices = constants.SurfsharkCityChoices(servers)
+		hostnameChoices = constants.SurfsharkHostnameChoices(servers)
+		regionChoices = constants.SurfsharkRegionChoices(servers)
+		// TODO v4 remove
+		regionChoices = append(regionChoices, constants.SurfsharkRetroLocChoices(servers)...)
+		if err := helpers.AreAllOneOf(ss.Regions, regionChoices); err != nil {
+			return fmt.Errorf("%w: %s", ErrRegionNotValid, err)
+		}
+		// Retro compatibility
+		// TODO remove in v4
+		*ss = surfsharkRetroRegion(*ss)
+	case constants.Torguard:
+		servers := allServers.GetTorguard()
+		countryChoices = constants.TorguardCountryChoices(servers)
+		cityChoices = constants.TorguardCityChoices(servers)
+		hostnameChoices = constants.TorguardHostnameChoices(servers)
+	case constants.VPNUnlimited:
+		servers := allServers.GetVPNUnlimited()
+		countryChoices = constants.VPNUnlimitedCountryChoices(servers)
+		cityChoices = constants.VPNUnlimitedCityChoices(servers)
+		hostnameChoices = constants.VPNUnlimitedHostnameChoices(servers)
+	case constants.Vyprvpn:
+		servers := allServers.GetVyprvpn()
+		regionChoices = constants.VyprvpnRegionChoices(servers)
+	case constants.Wevpn:
+		servers := allServers.GetWevpn()
+		cityChoices = constants.WevpnCityChoices(servers)
+		hostnameChoices = constants.WevpnHostnameChoices(servers)
+	case constants.Windscribe:
+		servers := allServers.GetWindscribe()
+		regionChoices = constants.WindscribeRegionChoices(servers)
+		cityChoices = constants.WindscribeCityChoices(servers)
+		hostnameChoices = constants.WindscribeHostnameChoices(servers)
+	default:
+		return fmt.Errorf("%w: %s", ErrVPNProviderNameNotValid, ss.VPN)
+	}
+
+	err = validateServerFilters(*ss, countryChoices, regionChoices, cityChoices,
+		ispChoices, nameChoices, hostnameChoices)
+	if err != nil {
+		return err // already wrapped error
+	}
+
+	err = ss.OpenVPN.validate(vpnServiceProvider)
+	if err != nil {
+		return fmt.Errorf("OpenVPN server selection settings validation failed: %w", err)
+	}
+
+	err = ss.Wireguard.validate(vpnServiceProvider)
+	if err != nil {
+		return fmt.Errorf("Wireguard server selection settings validation failed: %w", err)
+	}
+
+	return nil
+}
+
+// validateServerFilters validates filters against the choices given as arguments.
+// Set an argument to nil to pass the check for a particular filter.
+func validateServerFilters(settings ServerSelection,
+	countryChoices, regionChoices, cityChoices, ispChoices,
+	nameChoices, hostnameChoices []string) (err error) {
+	if countryChoices != nil {
+		if err := helpers.AreAllOneOf(settings.Countries, countryChoices); err != nil {
+			return fmt.Errorf("%w: %s", ErrCountryNotValid, err)
+		}
+	}
+
+	if regionChoices != nil {
+		if err := helpers.AreAllOneOf(settings.Regions, regionChoices); err != nil {
+			return fmt.Errorf("%w: %s", ErrRegionNotValid, err)
+		}
+	}
+
+	if cityChoices != nil {
+		if err := helpers.AreAllOneOf(settings.Cities, cityChoices); err != nil {
+			return fmt.Errorf("%w: %s", ErrCityNotValid, err)
+		}
+	}
+
+	if ispChoices != nil {
+		if err := helpers.AreAllOneOf(settings.ISPs, ispChoices); err != nil {
+			return fmt.Errorf("%w: %s", ErrISPNotValid, err)
+		}
+	}
+
+	if hostnameChoices != nil {
+		if err := helpers.AreAllOneOf(settings.Hostnames, hostnameChoices); err != nil {
+			return fmt.Errorf("%w: %s", ErrHostnameNotValid, err)
+		}
+	}
+
+	if nameChoices != nil {
+		if err := helpers.AreAllOneOf(settings.Names, nameChoices); err != nil {
+			return fmt.Errorf("%w: %s", ErrNameNotValid, err)
+		}
+	}
+
+	return nil
+}
+
+func (ss *ServerSelection) copy() (copied ServerSelection) {
+	return ServerSelection{
+		VPN:          ss.VPN,
+		TargetIP:     helpers.CopyIP(ss.TargetIP),
+		Countries:    helpers.CopyStringSlice(ss.Countries),
+		Regions:      helpers.CopyStringSlice(ss.Regions),
+		Cities:       helpers.CopyStringSlice(ss.Cities),
+		ISPs:         helpers.CopyStringSlice(ss.ISPs),
+		Hostnames:    helpers.CopyStringSlice(ss.Hostnames),
+		Names:        helpers.CopyStringSlice(ss.Names),
+		Numbers:      helpers.CopyUint16Slice(ss.Numbers),
+		OwnedOnly:    helpers.CopyBoolPtr(ss.OwnedOnly),
+		FreeOnly:     helpers.CopyBoolPtr(ss.FreeOnly),
+		StreamOnly:   helpers.CopyBoolPtr(ss.StreamOnly),
+		MultiHopOnly: helpers.CopyBoolPtr(ss.MultiHopOnly),
+		OpenVPN:      ss.OpenVPN.copy(),
+		Wireguard:    ss.Wireguard.copy(),
+	}
+}
+
+func (ss *ServerSelection) mergeWith(other ServerSelection) {
+	ss.VPN = helpers.MergeWithString(ss.VPN, other.VPN)
+	ss.TargetIP = helpers.MergeWithIP(ss.TargetIP, other.TargetIP)
+	ss.Countries = helpers.MergeStringSlices(ss.Countries, other.Countries)
+	ss.Regions = helpers.MergeStringSlices(ss.Regions, other.Regions)
+	ss.Cities = helpers.MergeStringSlices(ss.Cities, other.Cities)
+	ss.ISPs = helpers.MergeStringSlices(ss.ISPs, other.ISPs)
+	ss.Hostnames = helpers.MergeStringSlices(ss.Hostnames, other.Hostnames)
+	ss.Names = helpers.MergeStringSlices(ss.Hostnames, other.Names)
+	ss.Numbers = helpers.MergeUint16Slices(ss.Numbers, other.Numbers)
+	ss.OwnedOnly = helpers.MergeWithBool(ss.OwnedOnly, other.OwnedOnly)
+	ss.FreeOnly = helpers.MergeWithBool(ss.FreeOnly, other.FreeOnly)
+	ss.StreamOnly = helpers.MergeWithBool(ss.StreamOnly, other.StreamOnly)
+	ss.MultiHopOnly = helpers.MergeWithBool(ss.MultiHopOnly, other.MultiHopOnly)
+
+	ss.OpenVPN.mergeWith(other.OpenVPN)
+	ss.Wireguard.mergeWith(other.Wireguard)
+}
+
+func (ss *ServerSelection) overrideWith(other ServerSelection) {
+	ss.VPN = helpers.OverrideWithString(ss.VPN, other.VPN)
+	ss.TargetIP = helpers.OverrideWithIP(ss.TargetIP, other.TargetIP)
+	ss.Countries = helpers.OverrideWithStringSlice(ss.Countries, other.Countries)
+	ss.Regions = helpers.OverrideWithStringSlice(ss.Regions, other.Regions)
+	ss.Cities = helpers.OverrideWithStringSlice(ss.Cities, other.Cities)
+	ss.ISPs = helpers.OverrideWithStringSlice(ss.ISPs, other.ISPs)
+	ss.Hostnames = helpers.OverrideWithStringSlice(ss.Hostnames, other.Hostnames)
+	ss.Names = helpers.OverrideWithStringSlice(ss.Hostnames, other.Names)
+	ss.Numbers = helpers.OverrideWithUint16Slice(ss.Numbers, other.Numbers)
+	ss.OwnedOnly = helpers.OverrideWithBool(ss.OwnedOnly, other.OwnedOnly)
+	ss.FreeOnly = helpers.OverrideWithBool(ss.FreeOnly, other.FreeOnly)
+	ss.StreamOnly = helpers.OverrideWithBool(ss.StreamOnly, other.StreamOnly)
+	ss.MultiHopOnly = helpers.OverrideWithBool(ss.MultiHopOnly, other.MultiHopOnly)
+	ss.OpenVPN.overrideWith(other.OpenVPN)
+	ss.Wireguard.overrideWith(other.Wireguard)
+}
+
+func (ss *ServerSelection) setDefaults(vpnProvider string) {
+	ss.VPN = helpers.DefaultString(ss.VPN, constants.OpenVPN)
+	ss.TargetIP = helpers.DefaultIP(ss.TargetIP, net.IP{})
+	ss.OwnedOnly = helpers.DefaultBool(ss.OwnedOnly, false)
+	ss.FreeOnly = helpers.DefaultBool(ss.FreeOnly, false)
+	ss.StreamOnly = helpers.DefaultBool(ss.StreamOnly, false)
+	ss.MultiHopOnly = helpers.DefaultBool(ss.MultiHopOnly, false)
+	ss.OpenVPN.setDefaults(vpnProvider)
+	ss.Wireguard.setDefaults()
+}
+
+func (ss ServerSelection) String() string {
+	return ss.toLinesNode().String()
+}
+
+func (ss ServerSelection) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Server selection settings:")
+	node.Appendf("VPN type: %s", ss.VPN)
+	if len(ss.TargetIP) > 0 {
+		node.Appendf("Target IP address: %s", ss.TargetIP)
+	}
+
+	if len(ss.Countries) > 0 {
+		node.Appendf("Countries: %s", strings.Join(ss.Countries, ", "))
+	}
+
+	if len(ss.Regions) > 0 {
+		node.Appendf("Regions: %s", strings.Join(ss.Regions, ", "))
+	}
+
+	if len(ss.Cities) > 0 {
+		node.Appendf("Cities: %s", strings.Join(ss.Cities, ", "))
+	}
+
+	if len(ss.ISPs) > 0 {
+		node.Appendf("ISPs: %s", strings.Join(ss.ISPs, ", "))
+	}
+
+	if len(ss.Names) > 0 {
+		node.Appendf("Server names: %s", strings.Join(ss.Names, ", "))
+	}
+
+	if len(ss.Numbers) > 0 {
+		numbersNode := node.Appendf("Server numbers:")
+		for _, number := range ss.Numbers {
+			numbersNode.Appendf("%d", number)
+		}
+	}
+
+	if len(ss.Hostnames) > 0 {
+		node.Appendf("Hostnames: %s", strings.Join(ss.Hostnames, ", "))
+	}
+
+	if *ss.OwnedOnly {
+		node.Appendf("Owned only servers: yes")
+	}
+
+	if *ss.FreeOnly {
+		node.Appendf("Free only servers: yes")
+	}
+
+	if *ss.StreamOnly {
+		node.Appendf("Stream only servers: yes")
+	}
+
+	if *ss.MultiHopOnly {
+		node.Appendf("Multi-hop only servers: yes")
+	}
+
+	if ss.VPN == constants.OpenVPN {
+		node.AppendNode(ss.OpenVPN.toLinesNode())
+	} else {
+		node.AppendNode(ss.Wireguard.toLinesNode())
+	}
+
+	return node
+}
+
+// WithDefaults is a shorthand using setDefaults.
+// It's used in unit tests in other packages.
+func (ss ServerSelection) WithDefaults(provider string) ServerSelection {
+	ss.setDefaults(provider)
+	return ss
+}

internal/configuration/settings/settings.go

@@ -0,0 +1,144 @@
+package settings
+
+import (
+	"fmt"
+
+	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gotree"
+)
+
+type Settings struct {
+	ControlServer ControlServer
+	DNS           DNS
+	Firewall      Firewall
+	Health        Health
+	HTTPProxy     HTTPProxy
+	Log           Log
+	PublicIP      PublicIP
+	Shadowsocks   Shadowsocks
+	System        System
+	Updater       Updater
+	Version       Version
+	VPN           VPN
+}
+
+func (s Settings) Validate(allServers models.AllServers) (err error) {
+	nameToValidation := map[string]func() error{
+		"control server":  s.ControlServer.validate,
+		"dns":             s.DNS.validate,
+		"firewall":        s.Firewall.validate,
+		"health":          s.Health.Validate,
+		"http proxy":      s.HTTPProxy.validate,
+		"log":             s.Log.validate,
+		"public ip check": s.PublicIP.validate,
+		"shadowsocks":     s.Shadowsocks.validate,
+		"system":          s.System.validate,
+		"updater":         s.Updater.Validate,
+		"version":         s.Version.validate,
+		"VPN": func() error {
+			return s.VPN.validate(allServers)
+		},
+	}
+
+	for name, validation := range nameToValidation {
+		err = validation()
+		if err != nil {
+			return fmt.Errorf("failed validating %s settings: %w", name, err)
+		}
+	}
+
+	return nil
+}
+
+func (s *Settings) copy() (copied Settings) {
+	return Settings{
+		ControlServer: s.ControlServer.copy(),
+		DNS:           s.DNS.Copy(),
+		Firewall:      s.Firewall.copy(),
+		Health:        s.Health.copy(),
+		HTTPProxy:     s.HTTPProxy.copy(),
+		Log:           s.Log.copy(),
+		PublicIP:      s.PublicIP.copy(),
+		Shadowsocks:   s.Shadowsocks.copy(),
+		System:        s.System.copy(),
+		Updater:       s.Updater.copy(),
+		Version:       s.Version.copy(),
+		VPN:           s.VPN.copy(),
+	}
+}
+
+func (s *Settings) MergeWith(other Settings) {
+	s.ControlServer.mergeWith(other.ControlServer)
+	s.DNS.mergeWith(other.DNS)
+	s.Firewall.mergeWith(other.Firewall)
+	s.Health.MergeWith(other.Health)
+	s.HTTPProxy.mergeWith(other.HTTPProxy)
+	s.Log.mergeWith(other.Log)
+	s.PublicIP.mergeWith(other.PublicIP)
+	s.Shadowsocks.mergeWith(other.Shadowsocks)
+	s.System.mergeWith(other.System)
+	s.Updater.mergeWith(other.Updater)
+	s.Version.mergeWith(other.Version)
+	s.VPN.mergeWith(other.VPN)
+}
+
+func (s *Settings) OverrideWith(other Settings,
+	allServers models.AllServers) (err error) {
+	patchedSettings := s.copy()
+	patchedSettings.ControlServer.overrideWith(other.ControlServer)
+	patchedSettings.DNS.overrideWith(other.DNS)
+	patchedSettings.Firewall.overrideWith(other.Firewall)
+	patchedSettings.Health.OverrideWith(other.Health)
+	patchedSettings.HTTPProxy.overrideWith(other.HTTPProxy)
+	patchedSettings.Log.overrideWith(other.Log)
+	patchedSettings.PublicIP.overrideWith(other.PublicIP)
+	patchedSettings.Shadowsocks.overrideWith(other.Shadowsocks)
+	patchedSettings.System.overrideWith(other.System)
+	patchedSettings.Updater.overrideWith(other.Updater)
+	patchedSettings.Version.overrideWith(other.Version)
+	patchedSettings.VPN.overrideWith(other.VPN)
+	err = patchedSettings.Validate(allServers)
+	if err != nil {
+		return err
+	}
+	*s = patchedSettings
+	return nil
+}
+
+func (s *Settings) SetDefaults() {
+	s.ControlServer.setDefaults()
+	s.DNS.setDefaults()
+	s.Firewall.setDefaults()
+	s.Health.SetDefaults()
+	s.HTTPProxy.setDefaults()
+	s.Log.setDefaults()
+	s.PublicIP.setDefaults()
+	s.Shadowsocks.setDefaults()
+	s.System.setDefaults()
+	s.Updater.setDefaults()
+	s.Version.setDefaults()
+	s.VPN.setDefaults()
+}
+
+func (s Settings) String() string {
+	return s.toLinesNode().String()
+}
+
+func (s Settings) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Settings summary:")
+
+	node.AppendNode(s.VPN.toLinesNode())
+	node.AppendNode(s.DNS.toLinesNode())
+	node.AppendNode(s.Firewall.toLinesNode())
+	node.AppendNode(s.Log.toLinesNode())
+	node.AppendNode(s.Health.toLinesNode())
+	node.AppendNode(s.Shadowsocks.toLinesNode())
+	node.AppendNode(s.HTTPProxy.toLinesNode())
+	node.AppendNode(s.ControlServer.toLinesNode())
+	node.AppendNode(s.System.toLinesNode())
+	node.AppendNode(s.PublicIP.toLinesNode())
+	node.AppendNode(s.Updater.toLinesNode())
+	node.AppendNode(s.Version.toLinesNode())
+
+	return node
+}

internal/configuration/settings/settings_test.go

@@ -0,0 +1,101 @@
+package settings
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Settings_String(t *testing.T) {
+	t.Parallel()
+
+	withDefaults := func(s Settings) Settings {
+		s.SetDefaults()
+		return s
+	}
+
+	testCases := map[string]struct {
+		settings Settings
+		s        string
+	}{
+		"default settings": {
+			settings: withDefaults(Settings{}),
+			s: `Settings summary:
+├── VPN settings:
+|   ├── VPN provider settings:
+|   |   ├── Name: private internet access
+|   |   └── Server selection settings:
+|   |       ├── VPN type: openvpn
+|   |       └── OpenVPN server selection settings:
+|   |           ├── Protocol: UDP
+|   |           └── Private Internet Access encryption preset: strong
+|   └── OpenVPN server selection settings:
+|       ├── OpenVPN version: 2.5
+|       ├── User: [not set]
+|       ├── Password: [not set]
+|       ├── Private Internet Access encryption preset: strong
+|       ├── Tunnel IPv6: no
+|       ├── Network interface: tun0
+|       ├── Run OpenVPN as: root
+|       └── Verbosity level: 1
+├── DNS settings:
+|   ├── DNS server address to use: 127.0.0.1
+|   ├── Keep existing nameserver(s): no
+|   └── DNS over TLS settings:
+|       ├── Enabled: yes
+|       ├── Update period: every 24h0m0s
+|       ├── Unbound settings:
+|       |   ├── Authoritative servers:
+|       |   |   └── Cloudflare
+|       |   ├── Caching: yes
+|       |   ├── IPv6: no
+|       |   ├── Verbosity level: 1
+|       |   ├── Verbosity details level: 0
+|       |   ├── Validation log level: 0
+|       |   ├── System user: root
+|       |   └── Allowed networks:
+|       |       ├── 0.0.0.0/0
+|       |       └── ::/0
+|       └── DNS filtering settings:
+|           ├── Block malicious: yes
+|           ├── Block ads: no
+|           └── Block surveillance: yes
+├── Firewall settings:
+|   └── Enabled: yes
+├── Log settings:
+|   └── Log level: INFO
+├── Health settings:
+|   ├── Server listening address: 127.0.0.1:9999
+|   ├── Address to ping: github.com
+|   └── VPN wait durations:
+|       ├── Initial duration: 6s
+|       └── Additional duration: 5s
+├── Shadowsocks server settings:
+|   └── Enabled: no
+├── HTTP proxy settings:
+|   └── Enabled: no
+├── Control server settings:
+|   ├── Listening port: 8000
+|   └── Logging: yes
+├── OS Alpine settings:
+|   ├── Process UID: 1000
+|   └── Process GID: 1000
+├── Public IP settings:
+|   ├── Fetching: every 12h0m0s
+|   └── IP file path: /tmp/gluetun/ip
+└── Version settings:
+    └── Enabled: yes`,
+		},
+	}
+
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			s := testCase.settings.String()
+
+			assert.Equal(t, testCase.s, s)
+		})
+	}
+}

internal/configuration/settings/shadowsocks.go

@@ -0,0 +1,68 @@
+package settings
+
+import (
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+	"github.com/qdm12/ss-server/pkg/tcpudp"
+)
+
+// Shadowsocks contains settings to configure the Shadowsocks server.
+type Shadowsocks struct {
+	// Enabled is true if the server should be running.
+	// It defaults to false, and cannot be nil in the internal state.
+	Enabled *bool
+	// Settings are settings for the TCP+UDP server.
+	tcpudp.Settings
+}
+
+func (s Shadowsocks) validate() (err error) {
+	return s.Settings.Validate()
+}
+
+func (s *Shadowsocks) copy() (copied Shadowsocks) {
+	return Shadowsocks{
+		Enabled:  helpers.CopyBoolPtr(s.Enabled),
+		Settings: s.Settings.Copy(),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (s *Shadowsocks) mergeWith(other Shadowsocks) {
+	s.Enabled = helpers.MergeWithBool(s.Enabled, other.Enabled)
+	s.Settings.MergeWith(other.Settings)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (s *Shadowsocks) overrideWith(other Shadowsocks) {
+	s.Enabled = helpers.OverrideWithBool(s.Enabled, other.Enabled)
+	s.Settings.OverrideWith(other.Settings)
+}
+
+func (s *Shadowsocks) setDefaults() {
+	s.Enabled = helpers.DefaultBool(s.Enabled, false)
+	s.Settings.SetDefaults()
+}
+
+func (s Shadowsocks) String() string {
+	return s.toLinesNode().String()
+}
+
+func (s Shadowsocks) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Shadowsocks server settings:")
+
+	node.Appendf("Enabled: %s", helpers.BoolPtrToYesNo(s.Enabled))
+	if !*s.Enabled {
+		return node
+	}
+
+	// TODO have ToLinesNode in qdm12/ss-server
+	node.Appendf("Listening address: %s", s.Address)
+	node.Appendf("Cipher: %s", s.CipherName)
+	node.Appendf("Password: %s", helpers.ObfuscatePassword(*s.Password))
+	node.Appendf("Log addresses: %s", helpers.BoolPtrToYesNo(s.LogAddresses))
+
+	return node
+}

internal/configuration/settings/surfshark_retro.go

@@ -0,0 +1,56 @@
+package settings
+
+import (
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+func surfsharkRetroRegion(selection ServerSelection) (
+	updatedSelection ServerSelection) {
+	locationData := constants.SurfsharkLocationData()
+
+	retroToLocation := make(map[string]models.SurfsharkLocationData, len(locationData))
+	for _, data := range locationData {
+		if data.RetroLoc == "" {
+			continue
+		}
+		retroToLocation[strings.ToLower(data.RetroLoc)] = data
+	}
+
+	for i, region := range selection.Regions {
+		location, ok := retroToLocation[region]
+		if !ok {
+			continue
+		}
+		selection.Regions[i] = strings.ToLower(location.Region)
+		selection.Countries = append(selection.Countries, strings.ToLower(location.Country))
+		selection.Cities = append(selection.Cities, strings.ToLower(location.City)) // even empty string
+		selection.Hostnames = append(selection.Hostnames, location.Hostname)
+	}
+
+	selection.Regions = dedupSlice(selection.Regions)
+	selection.Countries = dedupSlice(selection.Countries)
+	selection.Cities = dedupSlice(selection.Cities)
+	selection.Hostnames = dedupSlice(selection.Hostnames)
+
+	return selection
+}
+
+func dedupSlice(slice []string) (deduped []string) {
+	if slice == nil {
+		return nil
+	}
+
+	deduped = make([]string, 0, len(slice))
+	seen := make(map[string]struct{}, len(slice))
+	for _, s := range slice {
+		if _, ok := seen[s]; !ok {
+			seen[s] = struct{}{}
+			deduped = append(deduped, s)
+		}
+	}
+
+	return deduped
+}

internal/configuration/settings/system.go

@@ -0,0 +1,61 @@
+package settings
+
+import (
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+// System contains settings to configure system related elements.
+type System struct {
+	PUID     *uint16
+	PGID     *uint16
+	Timezone string
+}
+
+// Validate validates System settings.
+func (s System) validate() (err error) {
+	return nil
+}
+
+func (s *System) copy() (copied System) {
+	return System{
+		PUID:     helpers.CopyUint16Ptr(s.PUID),
+		PGID:     helpers.CopyUint16Ptr(s.PGID),
+		Timezone: s.Timezone,
+	}
+}
+
+func (s *System) mergeWith(other System) {
+	s.PUID = helpers.MergeWithUint16(s.PUID, other.PUID)
+	s.PGID = helpers.MergeWithUint16(s.PGID, other.PGID)
+	s.Timezone = helpers.MergeWithString(s.Timezone, other.Timezone)
+}
+
+func (s *System) overrideWith(other System) {
+	s.PUID = helpers.OverrideWithUint16(s.PUID, other.PUID)
+	s.PGID = helpers.OverrideWithUint16(s.PGID, other.PGID)
+	s.Timezone = helpers.OverrideWithString(s.Timezone, other.Timezone)
+}
+
+func (s *System) setDefaults() {
+	const defaultID = 1000
+	s.PUID = helpers.DefaultUint16(s.PUID, defaultID)
+	s.PGID = helpers.DefaultUint16(s.PGID, defaultID)
+}
+
+func (s System) String() string {
+	return s.toLinesNode().String()
+}
+
+func (s System) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("OS Alpine settings:")
+
+	node.Appendf("Process UID: %d", *s.PUID)
+	node.Appendf("Process GID: %d", *s.PGID)
+
+	if s.Timezone != "" {
+		node.Appendf("Timezone: %s", s.Timezone)
+	}
+
+	return node
+}

internal/configuration/settings/unbound.go

@@ -0,0 +1,193 @@
+package settings
+
+import (
+	"errors"
+	"fmt"
+	"net"
+
+	"github.com/qdm12/dns/pkg/provider"
+	"github.com/qdm12/dns/pkg/unbound"
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+	"inet.af/netaddr"
+)
+
+// Unbound is settings for the Unbound program.
+type Unbound struct {
+	Providers             []string
+	Caching               *bool
+	IPv6                  *bool
+	VerbosityLevel        *uint8
+	VerbosityDetailsLevel *uint8
+	ValidationLogLevel    *uint8
+	Username              string
+	Allowed               []netaddr.IPPrefix
+}
+
+func (u *Unbound) setDefaults() {
+	if len(u.Providers) == 0 {
+		u.Providers = []string{
+			provider.Cloudflare().String(),
+		}
+	}
+
+	u.Caching = helpers.DefaultBool(u.Caching, true)
+	u.IPv6 = helpers.DefaultBool(u.IPv6, false)
+
+	const defaultVerbosityLevel = 1
+	u.VerbosityLevel = helpers.DefaultUint8(u.VerbosityLevel, defaultVerbosityLevel)
+
+	const defaultVerbosityDetailsLevel = 0
+	u.VerbosityDetailsLevel = helpers.DefaultUint8(u.VerbosityDetailsLevel, defaultVerbosityDetailsLevel)
+
+	const defaultValidationLogLevel = 0
+	u.ValidationLogLevel = helpers.DefaultUint8(u.ValidationLogLevel, defaultValidationLogLevel)
+
+	if u.Allowed == nil {
+		u.Allowed = []netaddr.IPPrefix{
+			netaddr.IPPrefixFrom(netaddr.IPv4(0, 0, 0, 0), 0),
+			netaddr.IPPrefixFrom(netaddr.IPv6Raw([16]byte{}), 0),
+		}
+	}
+
+	u.Username = helpers.DefaultString(u.Username, "root")
+}
+
+var (
+	ErrUnboundVerbosityLevelNotValid        = errors.New("Unbound verbosity level is not valid")
+	ErrUnboundVerbosityDetailsLevelNotValid = errors.New("Unbound verbosity details level is not valid")
+	ErrUnboundValidationLogLevelNotValid    = errors.New("Unbound validation log level is not valid")
+)
+
+func (u Unbound) validate() (err error) {
+	for _, s := range u.Providers {
+		_, err := provider.Parse(s)
+		if err != nil {
+			return err
+		}
+	}
+
+	const maxVerbosityLevel = 5
+	if *u.VerbosityLevel > maxVerbosityLevel {
+		return fmt.Errorf("%w: %d must be between 0 and %d",
+			ErrUnboundVerbosityLevelNotValid,
+			*u.VerbosityLevel,
+			maxVerbosityLevel)
+	}
+
+	const maxVerbosityDetailsLevel = 4
+	if *u.VerbosityDetailsLevel > maxVerbosityDetailsLevel {
+		return fmt.Errorf("%w: %d must be between 0 and %d",
+			ErrUnboundVerbosityDetailsLevelNotValid,
+			*u.VerbosityDetailsLevel,
+			maxVerbosityDetailsLevel)
+	}
+
+	const maxValidationLogLevel = 2
+	if *u.ValidationLogLevel > maxValidationLogLevel {
+		return fmt.Errorf("%w: %d must be between 0 and %d",
+			ErrUnboundValidationLogLevelNotValid,
+			*u.ValidationLogLevel, maxValidationLogLevel)
+	}
+
+	return nil
+}
+
+func (u Unbound) copy() (copied Unbound) {
+	return Unbound{
+		Providers:             helpers.CopyStringSlice(u.Providers),
+		Caching:               helpers.CopyBoolPtr(u.Caching),
+		IPv6:                  helpers.CopyBoolPtr(u.IPv6),
+		VerbosityLevel:        helpers.CopyUint8Ptr(u.VerbosityLevel),
+		VerbosityDetailsLevel: helpers.CopyUint8Ptr(u.VerbosityDetailsLevel),
+		ValidationLogLevel:    helpers.CopyUint8Ptr(u.ValidationLogLevel),
+		Username:              u.Username,
+		Allowed:               helpers.CopyIPPrefixSlice(u.Allowed),
+	}
+}
+
+func (u *Unbound) mergeWith(other Unbound) {
+	u.Providers = helpers.MergeStringSlices(u.Providers, other.Providers)
+	u.Caching = helpers.MergeWithBool(u.Caching, other.Caching)
+	u.IPv6 = helpers.MergeWithBool(u.IPv6, other.IPv6)
+	u.VerbosityLevel = helpers.MergeWithUint8(u.VerbosityLevel, other.VerbosityLevel)
+	u.VerbosityDetailsLevel = helpers.MergeWithUint8(u.VerbosityDetailsLevel, other.VerbosityDetailsLevel)
+	u.ValidationLogLevel = helpers.MergeWithUint8(u.ValidationLogLevel, other.ValidationLogLevel)
+	u.Username = helpers.MergeWithString(u.Username, other.Username)
+	u.Allowed = helpers.MergeIPPrefixesSlices(u.Allowed, other.Allowed)
+}
+
+func (u *Unbound) overrideWith(other Unbound) {
+	u.Providers = helpers.OverrideWithStringSlice(u.Providers, other.Providers)
+	u.Caching = helpers.OverrideWithBool(u.Caching, other.Caching)
+	u.IPv6 = helpers.OverrideWithBool(u.IPv6, other.IPv6)
+	u.VerbosityLevel = helpers.OverrideWithUint8(u.VerbosityLevel, other.VerbosityLevel)
+	u.VerbosityDetailsLevel = helpers.OverrideWithUint8(u.VerbosityDetailsLevel, other.VerbosityDetailsLevel)
+	u.ValidationLogLevel = helpers.OverrideWithUint8(u.ValidationLogLevel, other.ValidationLogLevel)
+	u.Username = helpers.OverrideWithString(u.Username, other.Username)
+	u.Allowed = helpers.OverrideWithIPPrefixesSlice(u.Allowed, other.Allowed)
+}
+
+func (u Unbound) ToUnboundFormat() (settings unbound.Settings, err error) {
+	providers := make([]provider.Provider, len(u.Providers))
+	for i := range providers {
+		providers[i], err = provider.Parse(u.Providers[i])
+		if err != nil {
+			return settings, err
+		}
+	}
+
+	const port = 53
+
+	return unbound.Settings{
+		ListeningPort:         port,
+		IPv4:                  true,
+		Providers:             providers,
+		Caching:               *u.Caching,
+		IPv6:                  *u.IPv6,
+		VerbosityLevel:        *u.VerbosityLevel,
+		VerbosityDetailsLevel: *u.VerbosityDetailsLevel,
+		ValidationLogLevel:    *u.ValidationLogLevel,
+		AccessControl: unbound.AccessControlSettings{
+			Allowed: u.Allowed,
+		},
+		Username: u.Username,
+	}, nil
+}
+
+func (u Unbound) GetFirstPlaintextIPv4() (ipv4 net.IP, err error) {
+	s := u.Providers[0]
+	provider, err := provider.Parse(s)
+	if err != nil {
+		return nil, err
+	}
+
+	return provider.DNS().IPv4[0], nil
+}
+
+func (u Unbound) String() string {
+	return u.toLinesNode().String()
+}
+
+func (u Unbound) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Unbound settings:")
+
+	authServers := node.Appendf("Authoritative servers:")
+	for _, provider := range u.Providers {
+		authServers.Appendf(provider)
+	}
+
+	node.Appendf("Caching: %s", helpers.BoolPtrToYesNo(u.Caching))
+	node.Appendf("IPv6: %s", helpers.BoolPtrToYesNo(u.IPv6))
+	node.Appendf("Verbosity level: %d", *u.VerbosityLevel)
+	node.Appendf("Verbosity details level: %d", *u.VerbosityDetailsLevel)
+	node.Appendf("Validation log level: %d", *u.ValidationLogLevel)
+	node.Appendf("System user: %s", u.Username)
+
+	allowedNetworks := node.Appendf("Allowed networks:")
+	for _, network := range u.Allowed {
+		allowedNetworks.Appendf(network.String())
+	}
+
+	return node
+}

internal/configuration/settings/unbound_test.go

@@ -0,0 +1,43 @@
+package settings
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"inet.af/netaddr"
+)
+
+func Test_Unbound_JSON(t *testing.T) {
+	t.Parallel()
+
+	settings := Unbound{
+		Providers:             []string{"cloudflare"},
+		Caching:               boolPtr(true),
+		IPv6:                  boolPtr(false),
+		VerbosityLevel:        uint8Ptr(1),
+		VerbosityDetailsLevel: nil,
+		ValidationLogLevel:    uint8Ptr(0),
+		Username:              "user",
+		Allowed: []netaddr.IPPrefix{
+			netaddr.IPPrefixFrom(netaddr.IPv4(0, 0, 0, 0), 0),
+			netaddr.IPPrefixFrom(netaddr.IPv6Raw([16]byte{}), 0),
+		},
+	}
+
+	b, err := json.Marshal(settings)
+	require.NoError(t, err)
+
+	const expected = `{"Providers":["cloudflare"],"Caching":true,"IPv6":false,` +
+		`"VerbosityLevel":1,"VerbosityDetailsLevel":null,"ValidationLogLevel":0,` +
+		`"Username":"user","Allowed":["0.0.0.0/0","::/0"]}`
+
+	assert.Equal(t, expected, string(b))
+
+	var resultSettings Unbound
+	err = json.Unmarshal(b, &resultSettings)
+	require.NoError(t, err)
+
+	assert.Equal(t, settings, resultSettings)
+}

internal/configuration/settings/updater.go

@@ -0,0 +1,113 @@
+package settings
+
+import (
+	"fmt"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gotree"
+)
+
+// Updater contains settings to configure the VPN
+// server information updater.
+type Updater struct {
+	// Period is the period for which the updater
+	// should run. It can be set to 0 to disable the
+	// updater. It cannot be nil in the internal state.
+	// TODO change to value and add Enabled field.
+	Period *time.Duration
+	// DNSAddress is the DNS server address to use
+	// to resolve VPN server hostnames to IP addresses.
+	// It cannot be nil in the internal state.
+	DNSAddress net.IP
+	// Providers is the list of VPN service providers
+	// to update server information for.
+	Providers []string
+	// CLI is to precise the updater is running in CLI
+	// mode. This is set automatically and cannot be set
+	// by settings sources. It cannot be nil in the
+	// internal state.
+	CLI *bool
+}
+
+func (u Updater) Validate() (err error) {
+	const minPeriod = time.Minute
+	if *u.Period > 0 && *u.Period < minPeriod {
+		return fmt.Errorf("%w: %d must be larger than %s",
+			ErrUpdaterPeriodTooSmall, *u.Period, minPeriod)
+	}
+
+	for i, provider := range u.Providers {
+		valid := false
+		for _, validProvider := range constants.AllProviders() {
+			if provider == validProvider {
+				valid = true
+				break
+			}
+		}
+		if !valid {
+			return fmt.Errorf("%w: %s at index %d",
+				ErrVPNProviderNameNotValid, provider, i)
+		}
+	}
+
+	return nil
+}
+
+func (u *Updater) copy() (copied Updater) {
+	return Updater{
+		Period:     helpers.CopyDurationPtr(u.Period),
+		DNSAddress: helpers.CopyIP(u.DNSAddress),
+		Providers:  helpers.CopyStringSlice(u.Providers),
+		CLI:        u.CLI,
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (u *Updater) mergeWith(other Updater) {
+	u.Period = helpers.MergeWithDuration(u.Period, other.Period)
+	u.DNSAddress = helpers.MergeWithIP(u.DNSAddress, other.DNSAddress)
+	u.Providers = helpers.MergeStringSlices(u.Providers, other.Providers)
+	u.CLI = helpers.MergeWithBool(u.CLI, other.CLI)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (u *Updater) overrideWith(other Updater) {
+	u.Period = helpers.OverrideWithDuration(u.Period, other.Period)
+	u.DNSAddress = helpers.OverrideWithIP(u.DNSAddress, other.DNSAddress)
+	u.Providers = helpers.OverrideWithStringSlice(u.Providers, other.Providers)
+	u.CLI = helpers.MergeWithBool(u.CLI, other.CLI)
+}
+
+func (u *Updater) setDefaults() {
+	u.Period = helpers.DefaultDuration(u.Period, 0)
+	u.DNSAddress = helpers.DefaultIP(u.DNSAddress, net.IPv4(1, 1, 1, 1))
+	u.CLI = helpers.DefaultBool(u.CLI, false)
+}
+
+func (u Updater) String() string {
+	return u.toLinesNode().String()
+}
+
+func (u Updater) toLinesNode() (node *gotree.Node) {
+	if *u.Period == 0 {
+		return nil
+	}
+
+	node = gotree.New("Server data updater settings:")
+	node.Appendf("Update period: %s", *u.Period)
+	node.Appendf("DNS address: %s", u.DNSAddress)
+	node.Appendf("Providers to update: %s", strings.Join(u.Providers, ", "))
+
+	if *u.CLI {
+		node.Appendf("CLI mode: enabled")
+	}
+
+	return node
+}

internal/configuration/settings/version.go

@@ -0,0 +1,53 @@
+package settings
+
+import (
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gotree"
+)
+
+// Version contains settings to configure the version
+// information fetcher.
+type Version struct {
+	// Enabled is true if the version information should
+	// be fetched from Github.
+	Enabled *bool
+}
+
+func (v Version) validate() (err error) {
+	return nil
+}
+
+func (v *Version) copy() (copied Version) {
+	return Version{
+		Enabled: helpers.CopyBoolPtr(v.Enabled),
+	}
+}
+
+// mergeWith merges the other settings into any
+// unset field of the receiver settings object.
+func (v *Version) mergeWith(other Version) {
+	v.Enabled = helpers.MergeWithBool(v.Enabled, other.Enabled)
+}
+
+// overrideWith overrides fields of the receiver
+// settings object with any field set in the other
+// settings.
+func (v *Version) overrideWith(other Version) {
+	v.Enabled = helpers.OverrideWithBool(v.Enabled, other.Enabled)
+}
+
+func (v *Version) setDefaults() {
+	v.Enabled = helpers.DefaultBool(v.Enabled, true)
+}
+
+func (v Version) String() string {
+	return v.toLinesNode().String()
+}
+
+func (v Version) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Version settings:")
+
+	node.Appendf("Enabled: %s", helpers.BoolPtrToYesNo(v.Enabled))
+
+	return node
+}

internal/configuration/settings/vpn.go

@@ -0,0 +1,98 @@
+package settings
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gotree"
+)
+
+type VPN struct {
+	// Type is the VPN type and can only be
+	// 'openvpn' or 'wireguard'. It cannot be the
+	// empty string in the internal state.
+	Type      string
+	Provider  Provider
+	OpenVPN   OpenVPN
+	Wireguard Wireguard
+}
+
+// Validate validates VPN settings.
+func (v VPN) validate(allServers models.AllServers) (err error) {
+	// Validate Type
+	validVPNTypes := []string{constants.OpenVPN, constants.Wireguard}
+	if !helpers.IsOneOf(v.Type, validVPNTypes...) {
+		return fmt.Errorf("%w: %q and can only be one of %s",
+			ErrVPNTypeNotValid, v.Type, strings.Join(validVPNTypes, ", "))
+	}
+
+	err = v.Provider.validate(v.Type, allServers)
+	if err != nil {
+		return fmt.Errorf("provider settings validation failed: %w", err)
+	}
+
+	if v.Type == constants.OpenVPN {
+		err := v.OpenVPN.validate(*v.Provider.Name)
+		if err != nil {
+			return fmt.Errorf("OpenVPN settings validation failed: %w", err)
+		}
+	} else {
+		err := v.Wireguard.validate(*v.Provider.Name)
+		if err != nil {
+			return fmt.Errorf("Wireguard settings validation failed: %w", err)
+		}
+	}
+
+	return nil
+}
+
+func (v *VPN) copy() (copied VPN) {
+	return VPN{
+		Type:      v.Type,
+		Provider:  v.Provider.copy(),
+		OpenVPN:   v.OpenVPN.copy(),
+		Wireguard: v.Wireguard.copy(),
+	}
+}
+
+func (v *VPN) mergeWith(other VPN) {
+	v.Type = helpers.MergeWithString(v.Type, other.Type)
+	v.Provider.mergeWith(other.Provider)
+	v.OpenVPN.mergeWith(other.OpenVPN)
+	v.Wireguard.mergeWith(other.Wireguard)
+}
+
+func (v *VPN) overrideWith(other VPN) {
+	v.Type = helpers.OverrideWithString(v.Type, other.Type)
+	v.Provider.overrideWith(other.Provider)
+	v.OpenVPN.overrideWith(other.OpenVPN)
+	v.Wireguard.overrideWith(other.Wireguard)
+}
+
+func (v *VPN) setDefaults() {
+	v.Type = helpers.DefaultString(v.Type, constants.OpenVPN)
+	v.Provider.setDefaults()
+	v.OpenVPN.setDefaults(*v.Provider.Name)
+	v.Wireguard.setDefaults()
+}
+
+func (v VPN) String() string {
+	return v.toLinesNode().String()
+}
+
+func (v VPN) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("VPN settings:")
+
+	node.AppendNode(v.Provider.toLinesNode())
+
+	if v.Type == constants.OpenVPN {
+		node.AppendNode(v.OpenVPN.toLinesNode())
+	} else {
+		node.AppendNode(v.Wireguard.toLinesNode())
+	}
+
+	return node
+}

internal/configuration/settings/wireguard.go

@@ -0,0 +1,138 @@
+package settings
+
+import (
+	"fmt"
+	"net"
+	"regexp"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gotree"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+)
+
+// Wireguard contains settings to configure the Wireguard client.
+type Wireguard struct {
+	// PrivateKey is the Wireguard client peer private key.
+	// It cannot be nil in the internal state.
+	PrivateKey *string
+	// PreSharedKey is the Wireguard pre-shared key.
+	// It can be the empty string to indicate there
+	// is no pre-shared key.
+	// It cannot be nil in the internal state.
+	PreSharedKey *string
+	// Addresses are the Wireguard interface addresses.
+	Addresses []net.IPNet
+	// Interface is the name of the Wireguard interface
+	// to create. It cannot be the empty string in the
+	// internal state.
+	Interface string
+}
+
+var regexpInterfaceName = regexp.MustCompile(`^[a-zA-Z0-9_]+$`)
+
+// Validate validates Wireguard settings.
+// It should only be ran if the VPN type chosen is Wireguard.
+func (w Wireguard) validate(vpnProvider string) (err error) {
+	if !helpers.IsOneOf(vpnProvider,
+		constants.Custom,
+		constants.Ivpn,
+		constants.Mullvad,
+		constants.Windscribe,
+	) {
+		// do not validate for VPN provider not supporting Wireguard
+		return nil
+	}
+
+	// Validate PrivateKey
+	if *w.PrivateKey == "" {
+		return ErrWireguardPrivateKeyNotSet
+	}
+	_, err = wgtypes.ParseKey(*w.PrivateKey)
+	if err != nil {
+		return fmt.Errorf("%w: %s", ErrWireguardPrivateKeyNotValid, err)
+	}
+
+	// Validate PreSharedKey
+	if *w.PreSharedKey != "" { // Note: this is optional
+		_, err = wgtypes.ParseKey(*w.PreSharedKey)
+		if err != nil {
+			return fmt.Errorf("%w: %s", ErrWireguardPreSharedKeyNotValid, err)
+		}
+	}
+
+	// Validate Addresses
+	if len(w.Addresses) == 0 {
+		return ErrWireguardInterfaceAddressNotSet
+	}
+	for i, ipNet := range w.Addresses {
+		if ipNet.IP == nil || ipNet.Mask == nil {
+			return fmt.Errorf("%w: for address at index %d: %s",
+				ErrWireguardInterfaceAddressNotSet, i, ipNet.String())
+		}
+	}
+
+	// Validate interface
+	if !regexpInterfaceName.MatchString(w.Interface) {
+		return fmt.Errorf("%w: '%s' does not match regex '%s'",
+			ErrWireguardInterfaceNotValid, w.Interface, regexpInterfaceName)
+	}
+
+	return nil
+}
+
+func (w *Wireguard) copy() (copied Wireguard) {
+	return Wireguard{
+		PrivateKey:   helpers.CopyStringPtr(w.PrivateKey),
+		PreSharedKey: helpers.CopyStringPtr(w.PreSharedKey),
+		Addresses:    helpers.CopyIPNetSlice(w.Addresses),
+		Interface:    w.Interface,
+	}
+}
+
+func (w *Wireguard) mergeWith(other Wireguard) {
+	w.PrivateKey = helpers.MergeWithStringPtr(w.PrivateKey, other.PrivateKey)
+	w.PreSharedKey = helpers.MergeWithStringPtr(w.PreSharedKey, other.PreSharedKey)
+	w.Addresses = helpers.MergeIPNetsSlices(w.Addresses, other.Addresses)
+	w.Interface = helpers.MergeWithString(w.Interface, other.Interface)
+}
+
+func (w *Wireguard) overrideWith(other Wireguard) {
+	w.PrivateKey = helpers.OverrideWithStringPtr(w.PrivateKey, other.PrivateKey)
+	w.PreSharedKey = helpers.OverrideWithStringPtr(w.PreSharedKey, other.PreSharedKey)
+	w.Addresses = helpers.OverrideWithIPNetsSlice(w.Addresses, other.Addresses)
+	w.Interface = helpers.OverrideWithString(w.Interface, other.Interface)
+}
+
+func (w *Wireguard) setDefaults() {
+	w.PrivateKey = helpers.DefaultStringPtr(w.PrivateKey, "")
+	w.PreSharedKey = helpers.DefaultStringPtr(w.PreSharedKey, "")
+	w.Interface = helpers.DefaultString(w.Interface, "wg0")
+}
+
+func (w Wireguard) String() string {
+	return w.toLinesNode().String()
+}
+
+func (w Wireguard) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Wireguard settings:")
+
+	if *w.PrivateKey != "" {
+		s := helpers.ObfuscateWireguardKey(*w.PrivateKey)
+		node.Appendf("Private key: %s", s)
+	}
+
+	if *w.PreSharedKey != "" {
+		s := helpers.ObfuscateWireguardKey(*w.PreSharedKey)
+		node.Appendf("Pre-shared key: %s", s)
+	}
+
+	addressesNode := node.Appendf("Interface addresses:")
+	for _, address := range w.Addresses {
+		addressesNode.Appendf(address.String())
+	}
+
+	node.Appendf("Network interface: %s", w.Interface)
+
+	return node
+}

internal/configuration/settings/wireguardselection.go

@@ -0,0 +1,144 @@
+package settings
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gotree"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+)
+
+type WireguardSelection struct {
+	// EndpointIP is the server endpoint IP address.
+	// It is only used with VPN providers generating Wireguard
+	// configurations specific to each server and user.
+	// To indicate it should not be used, it should be set
+	// to the empty net.IP{} slice. It can never be nil
+	// in the internal state.
+	EndpointIP net.IP
+	// EndpointPort is a the server port to use for the VPN server.
+	// It is optional for VPN providers IVPN, Mullvad
+	// and Windscribe, and compulsory for the others.
+	// When optional, it can be set to 0 to indicate not use
+	// a custom endpoint port. It cannot be nil in the internal
+	// state.
+	EndpointPort *uint16
+	// PublicKey is the server public key.
+	// It is only used with VPN providers generating Wireguard
+	// configurations specific to each server and user.
+	PublicKey string
+}
+
+// Validate validates WireguardSelection settings.
+// It should only be ran if the VPN type chosen is Wireguard.
+func (w WireguardSelection) validate(vpnProvider string) (err error) {
+	// Validate EndpointIP
+	switch vpnProvider {
+	case constants.Ivpn, constants.Mullvad, constants.Windscribe: // endpoint IP addresses are baked in
+	case constants.Custom:
+		if len(w.EndpointIP) == 0 {
+			return ErrWireguardEndpointIPNotSet
+		}
+	default: // Providers not supporting Wireguard
+	}
+
+	// Validate EndpointPort
+	switch vpnProvider {
+	// EndpointPort is required
+	case constants.Custom:
+		if *w.EndpointPort == 0 {
+			return ErrWireguardEndpointPortNotSet
+		}
+	case constants.Ivpn, constants.Mullvad, constants.Windscribe:
+		// EndpointPort is optional and can be 0
+		if *w.EndpointPort == 0 {
+			break // no custom endpoint port set
+		}
+		if vpnProvider == constants.Mullvad {
+			break // no restriction on custom endpoint port value
+		}
+		var allowed []uint16
+		switch vpnProvider {
+		case constants.Ivpn:
+			allowed = []uint16{2049, 2050, 53, 30587, 41893, 48574, 58237}
+		case constants.Windscribe:
+			allowed = []uint16{53, 80, 123, 443, 1194, 65142}
+		}
+
+		if helpers.Uint16IsOneOf(*w.EndpointPort, allowed) {
+			break
+		}
+		return fmt.Errorf("%w: %d for VPN service provider %s; %s",
+			ErrWireguardEndpointPortNotAllowed, w.EndpointPort, vpnProvider,
+			helpers.PortChoicesOrString(allowed))
+	default: // Providers not supporting Wireguard
+	}
+
+	// Validate PublicKey
+	switch vpnProvider {
+	case constants.Ivpn, constants.Mullvad, constants.Windscribe: // public keys are baked in
+	case constants.Custom:
+		if w.PublicKey == "" {
+			return ErrWireguardPublicKeyNotSet
+		}
+	default: // Providers not supporting Wireguard
+	}
+	if w.PublicKey != "" {
+		_, err := wgtypes.ParseKey(w.PublicKey)
+		if err != nil {
+			return fmt.Errorf("%w: %s: %s",
+				ErrWireguardPublicKeyNotValid, w.PublicKey, err)
+		}
+	}
+
+	return nil
+}
+
+func (w *WireguardSelection) copy() (copied WireguardSelection) {
+	return WireguardSelection{
+		EndpointIP:   helpers.CopyIP(w.EndpointIP),
+		EndpointPort: helpers.CopyUint16Ptr(w.EndpointPort),
+		PublicKey:    w.PublicKey,
+	}
+}
+
+func (w *WireguardSelection) mergeWith(other WireguardSelection) {
+	w.EndpointIP = helpers.MergeWithIP(w.EndpointIP, other.EndpointIP)
+	w.EndpointPort = helpers.MergeWithUint16(w.EndpointPort, other.EndpointPort)
+	w.PublicKey = helpers.MergeWithString(w.PublicKey, other.PublicKey)
+}
+
+func (w *WireguardSelection) overrideWith(other WireguardSelection) {
+	w.EndpointIP = helpers.OverrideWithIP(w.EndpointIP, other.EndpointIP)
+	w.EndpointPort = helpers.OverrideWithUint16(w.EndpointPort, other.EndpointPort)
+	w.PublicKey = helpers.OverrideWithString(w.PublicKey, other.PublicKey)
+}
+
+func (w *WireguardSelection) setDefaults() {
+	w.EndpointIP = helpers.DefaultIP(w.EndpointIP, net.IP{})
+	w.EndpointPort = helpers.DefaultUint16(w.EndpointPort, 0)
+}
+
+func (w WireguardSelection) String() string {
+	return w.toLinesNode().String()
+}
+
+func (w WireguardSelection) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Wireguard selection settings:")
+
+	if len(w.EndpointIP) > 0 {
+		node.Appendf("Endpoint IP address: %s", w.EndpointIP)
+	}
+
+	if *w.EndpointPort != 0 {
+		node.Appendf("Endpoint port: %d", *w.EndpointPort)
+	}
+
+	if w.PublicKey != "" {
+		node.Appendf("Server public key: %s", w.PublicKey)
+	}
+
+	return node
+}