Maint: refactor internal/routing

- Split Go files better
- Reduce public API for exported errors

internal/routing/local.go

@@ -0,0 +1,121 @@
+package routing
+
+import (
+	"errors"
+	"fmt"
+	"net"
+
+	"github.com/qdm12/gluetun/internal/netlink"
+)
+
+var (
+	ErrLinkList              = errors.New("cannot list links")
+	ErrLinkLocalNotFound     = errors.New("local link not found")
+	ErrSubnetDefaultNotFound = errors.New("default subnet not found")
+	ErrSubnetLocalNotFound   = errors.New("local subnet not found")
+)
+
+type LocalNetwork struct {
+	IPNet         *net.IPNet
+	InterfaceName string
+	IP            net.IP
+}
+
+type LocalSubnetGetter interface {
+	LocalSubnet() (defaultSubnet net.IPNet, err error)
+}
+
+func (r *Routing) LocalSubnet() (defaultSubnet net.IPNet, err error) {
+	routes, err := r.netLinker.RouteList(nil, netlink.FAMILY_ALL)
+	if err != nil {
+		return defaultSubnet, fmt.Errorf("%w: %s", ErrRoutesList, err)
+	}
+
+	defaultLinkIndex := -1
+	for _, route := range routes {
+		if route.Dst == nil {
+			defaultLinkIndex = route.LinkIndex
+			break
+		}
+	}
+	if defaultLinkIndex == -1 {
+		return defaultSubnet, fmt.Errorf("%w: in %d route(s)", ErrLinkDefaultNotFound, len(routes))
+	}
+
+	for _, route := range routes {
+		if route.Gw != nil || route.LinkIndex != defaultLinkIndex {
+			continue
+		}
+		defaultSubnet = *route.Dst
+		r.logger.Info("local subnet found: " + defaultSubnet.String())
+		return defaultSubnet, nil
+	}
+
+	return defaultSubnet, fmt.Errorf("%w: in %d routes", ErrSubnetDefaultNotFound, len(routes))
+}
+
+type LocalNetworksGetter interface {
+	LocalNetworks() (localNetworks []LocalNetwork, err error)
+}
+
+func (r *Routing) LocalNetworks() (localNetworks []LocalNetwork, err error) {
+	links, err := r.netLinker.LinkList()
+	if err != nil {
+		return localNetworks, fmt.Errorf("%w: %s", ErrLinkList, err)
+	}
+
+	localLinks := make(map[int]struct{})
+
+	for _, link := range links {
+		if link.Attrs().EncapType != "ether" {
+			continue
+		}
+
+		localLinks[link.Attrs().Index] = struct{}{}
+		r.logger.Info("local ethernet link found: " + link.Attrs().Name)
+	}
+
+	if len(localLinks) == 0 {
+		return localNetworks, fmt.Errorf("%w: in %d links", ErrLinkLocalNotFound, len(links))
+	}
+
+	routes, err := r.netLinker.RouteList(nil, netlink.FAMILY_V4)
+	if err != nil {
+		return localNetworks, fmt.Errorf("%w: %s", ErrRoutesList, err)
+	}
+
+	for _, route := range routes {
+		if route.Gw != nil || route.Dst == nil {
+			continue
+		} else if _, ok := localLinks[route.LinkIndex]; !ok {
+			continue
+		}
+
+		var localNet LocalNetwork
+
+		localNet.IPNet = route.Dst
+		r.logger.Info("local ipnet found: " + localNet.IPNet.String())
+
+		link, err := r.netLinker.LinkByIndex(route.LinkIndex)
+		if err != nil {
+			return localNetworks, fmt.Errorf("%w: at index %d: %s", ErrLinkByIndex, route.LinkIndex, err)
+		}
+
+		localNet.InterfaceName = link.Attrs().Name
+
+		ip, err := r.assignedIP(localNet.InterfaceName)
+		if err != nil {
+			return localNetworks, err
+		}
+
+		localNet.IP = ip
+
+		localNetworks = append(localNetworks, localNet)
+	}
+
+	if len(localNetworks) == 0 {
+		return localNetworks, fmt.Errorf("%w: in %d routes", ErrSubnetLocalNotFound, len(routes))
+	}
+
+	return localNetworks, nil
+}