Support client default routes for Linux (#1667)

All routes are now installed in a custom netbird routing table.
Management and wireguard traffic is now marked with a custom fwmark.
When the mark is present the traffic is routed via the main routing table, bypassing the VPN.
When the mark is absent the traffic is routed via the netbird routing table, if:
- there's no match in the main routing table
- it would match the default route in the routing table

IPv6 traffic is blocked when a default route IPv4 route is configured to avoid leakage.

client/internal/routemanager/server_nonandroid.go

@@ -4,6 +4,7 @@ package routemanager
 
 import (
 	"context"
+	"fmt"
 	"net/netip"
 	"sync"
 
@@ -48,7 +49,7 @@ func (m *defaultServerRouter) updateRoutes(routesMap map[string]*route.Route) er
 		oldRoute := m.routes[routeID]
 		err := m.removeFromServerNetwork(oldRoute)
 		if err != nil {
-			log.Errorf("unable to remove route id: %s, network %s, from server, got: %v",
+			log.Errorf("Unable to remove route id: %s, network %s, from server, got: %v",
 				oldRoute.ID, oldRoute.Network, err)
 		}
 		delete(m.routes, routeID)
@@ -62,7 +63,7 @@ func (m *defaultServerRouter) updateRoutes(routesMap map[string]*route.Route) er
 
 		err := m.addToServerNetwork(newRoute)
 		if err != nil {
-			log.Errorf("unable to add route %s from server, got: %v", newRoute.ID, err)
+			log.Errorf("Unable to add route %s from server, got: %v", newRoute.ID, err)
 			continue
 		}
 		m.routes[id] = newRoute
@@ -81,15 +82,22 @@ func (m *defaultServerRouter) updateRoutes(routesMap map[string]*route.Route) er
 func (m *defaultServerRouter) removeFromServerNetwork(route *route.Route) error {
 	select {
 	case <-m.ctx.Done():
-		log.Infof("not removing from server network because context is done")
+		log.Infof("Not removing from server network because context is done")
 		return m.ctx.Err()
 	default:
 		m.mux.Lock()
 		defer m.mux.Unlock()
-		err := m.firewall.RemoveRoutingRules(routeToRouterPair(m.wgInterface.Address().String(), route))
+
+		routerPair, err := routeToRouterPair(m.wgInterface.Address().Masked().String(), route)
 		if err != nil {
-			return err
+			return fmt.Errorf("parse prefix: %w", err)
 		}
+
+		err = m.firewall.RemoveRoutingRules(routerPair)
+		if err != nil {
+			return fmt.Errorf("remove routing rules: %w", err)
+		}
+
 		delete(m.routes, route.ID)
 
 		state := m.statusRecorder.GetLocalPeerState()
@@ -103,15 +111,22 @@ func (m *defaultServerRouter) removeFromServerNetwork(route *route.Route) error
 func (m *defaultServerRouter) addToServerNetwork(route *route.Route) error {
 	select {
 	case <-m.ctx.Done():
-		log.Infof("not adding to server network because context is done")
+		log.Infof("Not adding to server network because context is done")
 		return m.ctx.Err()
 	default:
 		m.mux.Lock()
 		defer m.mux.Unlock()
-		err := m.firewall.InsertRoutingRules(routeToRouterPair(m.wgInterface.Address().String(), route))
+
+		routerPair, err := routeToRouterPair(m.wgInterface.Address().Masked().String(), route)
 		if err != nil {
-			return err
+			return fmt.Errorf("parse prefix: %w", err)
 		}
+
+		err = m.firewall.InsertRoutingRules(routerPair)
+		if err != nil {
+			return fmt.Errorf("insert routing rules: %w", err)
+		}
+
 		m.routes[route.ID] = route
 
 		state := m.statusRecorder.GetLocalPeerState()
@@ -129,9 +144,15 @@ func (m *defaultServerRouter) cleanUp() {
 	m.mux.Lock()
 	defer m.mux.Unlock()
 	for _, r := range m.routes {
-		err := m.firewall.RemoveRoutingRules(routeToRouterPair(m.wgInterface.Address().String(), r))
+		routerPair, err := routeToRouterPair(m.wgInterface.Address().Masked().String(), r)
 		if err != nil {
-			log.Warnf("failed to remove clean up route: %s", r.ID)
+			log.Errorf("Failed to convert route to router pair: %v", err)
+			continue
+		}
+
+		err = m.firewall.RemoveRoutingRules(routerPair)
+		if err != nil {
+			log.Errorf("Failed to remove cleanup route: %v", err)
 		}
 
 		state := m.statusRecorder.GetLocalPeerState()
@@ -139,13 +160,15 @@ func (m *defaultServerRouter) cleanUp() {
 		m.statusRecorder.UpdateLocalPeerState(state)
 	}
 }
-
-func routeToRouterPair(source string, route *route.Route) firewall.RouterPair {
-	parsed := netip.MustParsePrefix(source).Masked()
+func routeToRouterPair(source string, route *route.Route) (firewall.RouterPair, error) {
+	parsed, err := netip.ParsePrefix(source)
+	if err != nil {
+		return firewall.RouterPair{}, err
+	}
 	return firewall.RouterPair{
 		ID:          route.ID,
 		Source:      parsed.String(),
 		Destination: route.Network.Masked().String(),
 		Masquerade:  route.Masquerade,
-	}
+	}, nil
 }