Netlink Go library to interact with IP routes (#267)
This commit is contained in:
Quentin McGaw
@@ -4,120 +4,105 @@ import (
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"bytes"
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"fmt"
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"net"
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"strings"
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"github.com/qdm12/gluetun/internal/constants"
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"github.com/qdm12/golibs/files"
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"github.com/vishvananda/netlink"
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)
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func parseRoutingTable(data []byte) (entries []routingEntry, err error) {
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lines := strings.Split(strings.TrimSuffix(string(data), "\n"), "\n")
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lines = lines[1:]
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entries = make([]routingEntry, len(lines))
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for i := range lines {
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entries[i], err = parseRoutingEntry(lines[i])
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if err != nil {
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return nil, fmt.Errorf("line %d in %s: %w", i+1, constants.NetRoute, err)
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}
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}
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return entries, nil
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}
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func getRoutingEntries(fileManager files.FileManager) (entries []routingEntry, err error) {
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data, err := fileManager.ReadFile(string(constants.NetRoute))
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if err != nil {
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return nil, err
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}
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return parseRoutingTable(data)
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}
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func (r *routing) DefaultRoute() (defaultInterface string, defaultGateway net.IP, err error) {
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entries, err := getRoutingEntries(r.fileManager)
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routes, err := netlink.RouteList(nil, netlink.FAMILY_ALL)
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if err != nil {
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return "", nil, err
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return "", nil, fmt.Errorf("cannot list routes: %w", err)
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}
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const minEntries = 2
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if len(entries) < minEntries {
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return "", nil, fmt.Errorf("not enough entries (%d) found in %s", len(entries), constants.NetRoute)
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}
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var defaultRouteEntry routingEntry
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for _, entry := range entries {
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if entry.mask.String() == "00000000" {
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defaultRouteEntry = entry
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break
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for _, route := range routes {
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if route.Dst == nil {
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defaultGateway = route.Gw
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linkIndex := route.LinkIndex
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link, err := netlink.LinkByIndex(linkIndex)
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if err != nil {
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return "", nil, fmt.Errorf("cannot obtain link with index %d for default route: %w", linkIndex, err)
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}
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attributes := link.Attrs()
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defaultInterface = attributes.Name
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r.logger.Info("default route found: interface %s, gateway %s", defaultInterface, defaultGateway.String())
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return defaultInterface, defaultGateway, nil
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}
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}
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if defaultRouteEntry.iface == "" {
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return "", nil, fmt.Errorf("cannot find default route")
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}
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defaultInterface = defaultRouteEntry.iface
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defaultGateway = defaultRouteEntry.gateway
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r.logger.Info("default route found: interface %s, gateway %s", defaultInterface, defaultGateway.String())
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return defaultInterface, defaultGateway, nil
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return "", nil, fmt.Errorf("cannot find default route in %d routes", len(routes))
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}
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func (r *routing) LocalSubnet() (defaultSubnet net.IPNet, err error) {
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entries, err := getRoutingEntries(r.fileManager)
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routes, err := netlink.RouteList(nil, netlink.FAMILY_ALL)
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if err != nil {
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return defaultSubnet, err
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return defaultSubnet, fmt.Errorf("cannot find local subnet: %w", err)
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}
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const minEntries = 2
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if len(entries) < minEntries {
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return defaultSubnet, fmt.Errorf("not enough entries (%d) found in %s", len(entries), constants.NetRoute)
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}
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var localSubnetEntry routingEntry
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for _, entry := range entries {
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if entry.gateway.Equal(net.IP{0, 0, 0, 0}) && !strings.HasPrefix(entry.iface, "tun") {
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localSubnetEntry = entry
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defaultLinkIndex := -1
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for _, route := range routes {
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if route.Dst == nil {
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defaultLinkIndex = route.LinkIndex
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break
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}
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}
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if localSubnetEntry.iface == "" {
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return defaultSubnet, fmt.Errorf("cannot find local subnet route")
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if defaultLinkIndex == -1 {
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return defaultSubnet, fmt.Errorf("cannot find local subnet: cannot find default link")
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}
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defaultSubnet = net.IPNet{IP: localSubnetEntry.destination, Mask: localSubnetEntry.mask}
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r.logger.Info("local subnet found: %s", defaultSubnet.String())
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return defaultSubnet, nil
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for _, route := range routes {
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if route.Gw != nil || route.LinkIndex != defaultLinkIndex {
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continue
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}
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defaultSubnet = *route.Dst
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r.logger.Info("local subnet found: %s", defaultSubnet.String())
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return defaultSubnet, nil
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}
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return defaultSubnet, fmt.Errorf("cannot find default subnet in %d routes", len(routes))
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}
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func (r *routing) routeExists(subnet net.IPNet) (exists bool, err error) {
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entries, err := getRoutingEntries(r.fileManager)
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func (r *routing) VPNDestinationIP() (ip net.IP, err error) {
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routes, err := netlink.RouteList(nil, netlink.FAMILY_ALL)
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if err != nil {
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return false, fmt.Errorf("cannot check route existence: %w", err)
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return nil, fmt.Errorf("cannot find VPN destination IP: %w", err)
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}
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for _, entry := range entries {
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entrySubnet := net.IPNet{IP: entry.destination, Mask: entry.mask}
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if entrySubnet.String() == subnet.String() {
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return true, nil
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}
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}
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return false, nil
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}
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func (r *routing) VPNDestinationIP(defaultInterface string) (ip net.IP, err error) {
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entries, err := getRoutingEntries(r.fileManager)
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if err != nil {
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return nil, fmt.Errorf("cannot find VPN gateway IP address: %w", err)
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}
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for _, entry := range entries {
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if entry.iface == defaultInterface &&
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!ipIsPrivate(entry.destination) &&
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bytes.Equal(entry.mask, net.IPMask{255, 255, 255, 255}) {
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return entry.destination, nil
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defaultLinkIndex := -1
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for _, route := range routes {
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if route.Dst == nil {
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defaultLinkIndex = route.LinkIndex
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break
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}
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}
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return nil, fmt.Errorf("cannot find VPN gateway IP address from ip routes")
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if defaultLinkIndex == -1 {
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return nil, fmt.Errorf("cannot find VPN destination IP: cannot find default link")
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}
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for _, route := range routes {
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if route.LinkIndex == defaultLinkIndex &&
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route.Dst != nil &&
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!ipIsPrivate(route.Dst.IP) &&
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bytes.Equal(route.Dst.Mask, net.IPMask{255, 255, 255, 255}) {
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return route.Dst.IP, nil
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}
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}
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return nil, fmt.Errorf("cannot find VPN destination IP address from ip routes")
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}
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func (r *routing) VPNLocalGatewayIP() (ip net.IP, err error) {
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entries, err := getRoutingEntries(r.fileManager)
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routes, err := netlink.RouteList(nil, netlink.FAMILY_ALL)
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if err != nil {
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return nil, fmt.Errorf("cannot find VPN local gateway IP address: %w", err)
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return nil, fmt.Errorf("cannot find VPN local gateway IP: %w", err)
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}
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for _, entry := range entries {
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if entry.iface == string(constants.TUN) &&
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entry.destination.Equal(net.IP{0, 0, 0, 0}) {
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return entry.gateway, nil
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for _, route := range routes {
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link, err := netlink.LinkByIndex(route.LinkIndex)
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if err != nil {
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return nil, fmt.Errorf("cannot find VPN local gateway IP: %w", err)
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}
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interfaceName := link.Attrs().Name
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if interfaceName == string(constants.TUN) &&
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route.Dst != nil &&
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route.Dst.IP.Equal(net.IP{0, 0, 0, 0}) {
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return route.Gw, nil
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}
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}
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return nil, fmt.Errorf("cannot find VPN local gateway IP address from ip routes")
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