change checks before route adding to not only check for default gateway (test missing)

client/internal/routemanager/systemops_nonandroid.go

@@ -6,27 +6,51 @@ import (
 	"fmt"
 	"net"
 	"net/netip"
+	"syscall"
 
 	"github.com/libp2p/go-netroute"
 	log "github.com/sirupsen/logrus"
+	"golang.org/x/net/route"
+)
+
+// selected BSD Route flags.
+const (
+	RTF_UP        = 0x1
+	RTF_GATEWAY   = 0x2
+	RTF_HOST      = 0x4
+	RTF_REJECT    = 0x8
+	RTF_DYNAMIC   = 0x10
+	RTF_MODIFIED  = 0x20
+	RTF_STATIC    = 0x800
+	RTF_BLACKHOLE = 0x1000
+	RTF_LOCAL     = 0x200000
+	RTF_BROADCAST = 0x400000
+	RTF_MULTICAST = 0x800000
 )
 
 var errRouteNotFound = fmt.Errorf("route not found")
 
 func addToRouteTableIfNoExists(prefix netip.Prefix, addr string) error {
-	gateway, err := getExistingRIBRouteGateway(netip.MustParsePrefix("0.0.0.0/0"))
-	if err != nil && err != errRouteNotFound {
-		return err
-	}
-	prefixGateway, err := getExistingRIBRouteGateway(prefix)
+	defaultGateway, err := getExistingRIBRouteGateway(netip.MustParsePrefix("0.0.0.0/0"))
 	if err != nil && err != errRouteNotFound {
 		return err
 	}
 
-	if prefixGateway != nil && !prefixGateway.Equal(gateway) {
-		log.Warnf("skipping adding a new route for network %s because it already exists and is pointing to the non default gateway: %s", prefix, prefixGateway)
+	gatewayIP := netip.MustParseAddr(defaultGateway.String())
+	if prefix.Contains(gatewayIP) {
+		log.Warnf("skipping adding a new route for network %s because it overlaps with the default gateway: %s", prefix, gatewayIP)
 		return nil
 	}
+
+	ok, err := existsInRouteTable(prefix)
+	if err != nil {
+		return err
+	}
+	if ok {
+		log.Warnf("skipping adding a new route for network %s because it already exists", prefix)
+		return nil
+	}
+
 	return addToRouteTable(prefix, addr)
 }
 
@@ -48,14 +72,70 @@ func getExistingRIBRouteGateway(prefix netip.Prefix) (net.IP, error) {
 	if err != nil {
 		return nil, err
 	}
-	_, gateway, preferredSrc, err := r.Route(prefix.Addr().AsSlice())
+	_, gateway, _, err := r.Route(prefix.Addr().AsSlice())
 	if err != nil {
 		log.Errorf("getting routes returned an error: %v", err)
 		return nil, errRouteNotFound
 	}
-	if gateway == nil {
-		return preferredSrc, nil
-	}
 
 	return gateway, nil
 }
+
+func existsInRouteTable(prefix netip.Prefix) (bool, error) {
+	tab, err := route.FetchRIB(syscall.AF_UNSPEC, route.RIBTypeRoute, 0)
+	if err != nil {
+		return false, err
+	}
+	msgs, err := route.ParseRIB(route.RIBTypeRoute, tab)
+	if err != nil {
+		return false, err
+	}
+
+	for _, msg := range msgs {
+		m := msg.(*route.RouteMessage)
+
+		if m.Version < 3 || m.Version > 5 {
+			return false, fmt.Errorf("unexpected RIB message version: %d", m.Version)
+		}
+		if m.Type != 4 /* RTM_GET */ {
+			return true, fmt.Errorf("unexpected RIB message type: %d", m.Type)
+		}
+
+		if m.Flags&RTF_UP == 0 ||
+			m.Flags&(RTF_REJECT|RTF_BLACKHOLE) != 0 {
+			continue
+		}
+
+		dst, err := toIPAddr(m.Addrs[0])
+		log.Debugf("checking route: %s", dst)
+		if err != nil {
+			return true, fmt.Errorf("unexpected RIB destination: %v", err)
+		}
+
+		mask, err := toIPAddr(m.Addrs[2])
+		log.Debugf("checking route mask: %s", mask)
+		if err != nil {
+			return true, fmt.Errorf("unexpected RIB destination: %v", err)
+		}
+		cidr, _ := net.IPMask(mask.To4()).Size()
+		if dst.String() == prefix.Addr().String() && cidr == prefix.Bits() {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}
+
+func toIPAddr(a route.Addr) (net.IP, error) {
+	switch t := a.(type) {
+	case *route.Inet4Addr:
+		ip := net.IPv4(t.IP[0], t.IP[1], t.IP[2], t.IP[3])
+		return ip, nil
+	case *route.Inet6Addr:
+		ip := make(net.IP, net.IPv6len)
+		copy(ip, t.IP[:])
+		return ip, nil
+	default:
+		return net.IP{}, fmt.Errorf("unknown family: %v", t)
+	}
+}

client/internal/routemanager/systemops_nonandroid_test.go

@@ -2,14 +2,20 @@ package routemanager
 
 import (
 	"fmt"
-	"github.com/netbirdio/netbird/iface"
-	"github.com/pion/transport/v2/stdnet"
-	"github.com/stretchr/testify/require"
 	"net"
 	"net/netip"
 	"testing"
+
+	"github.com/pion/transport/v2/stdnet"
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/iface"
 )
 
+// func TestAddRoute(t *testing.T) {
+// 	addToRouteTableIfNoExists()
+// }
+
 func TestAddRemoveRoutes(t *testing.T) {
 	testCases := []struct {
 		name                   string