[client] Use native windows sock opts to avoid routing loops (#4314)

- Move `util/grpc` and `util/net` to `client` so `internal` packages can be accessed
 - Add methods to return the next best interface after the NetBird interface.
- Use `IP_UNICAST_IF` sock opt to force the outgoing interface for the NetBird `net.Dialer` and `net.ListenerConfig` to avoid routing loops. The interface is picked by the new route lookup method.
- Some refactoring to avoid import cycles
- Old behavior is available through `NB_USE_LEGACY_ROUTING=true` env var

client/iface/bind/control.go

@@ -3,7 +3,7 @@ package bind
 import (
 	wireguard "golang.zx2c4.com/wireguard/conn"
 
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 // TODO: This is most likely obsolete since the control fns should be called by the wrapped udpconn (ice_bind.go)

client/iface/bind/ice_bind.go

@@ -17,7 +17,7 @@ import (
 
 	"github.com/netbirdio/netbird/client/iface/udpmux"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 type RecvMessage struct {

client/iface/configurer/usp.go

@@ -17,8 +17,8 @@ import (
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
 	"github.com/netbirdio/netbird/client/iface/bind"
+	nbnet "github.com/netbirdio/netbird/client/net"
 	"github.com/netbirdio/netbird/monotime"
-	nbnet "github.com/netbirdio/netbird/util/net"
 )
 
 const (
@@ -409,7 +409,7 @@ func toBytes(s string) (int64, error) {
 }
 
 func getFwmark() int {
-	if nbnet.AdvancedRouting() {
+	if nbnet.AdvancedRouting() && runtime.GOOS == "linux" {
 		return nbnet.ControlPlaneMark
 	}
 	return 0

client/iface/device/device_kernel_unix.go

@@ -15,8 +15,8 @@ import (
 	"github.com/netbirdio/netbird/client/iface/configurer"
 	"github.com/netbirdio/netbird/client/iface/udpmux"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
+	nbnet "github.com/netbirdio/netbird/client/net"
 	"github.com/netbirdio/netbird/sharedsock"
-	nbnet "github.com/netbirdio/netbird/util/net"
 )
 
 type TunKernelDevice struct {
@@ -101,13 +101,8 @@ func (t *TunKernelDevice) Up() (*udpmux.UniversalUDPMuxDefault, error) {
 		return nil, err
 	}
 
-	var udpConn net.PacketConn = rawSock
-	if !nbnet.AdvancedRouting() {
-		udpConn = nbnet.WrapPacketConn(rawSock)
-	}
-
 	bindParams := udpmux.UniversalUDPMuxParams{
-		UDPConn:   udpConn,
+		UDPConn:   nbnet.WrapPacketConn(rawSock),
 		Net:       t.transportNet,
 		FilterFn:  t.filterFn,
 		WGAddress: t.address,

client/iface/device/device_netstack.go

@@ -12,7 +12,7 @@ import (
 	nbnetstack "github.com/netbirdio/netbird/client/iface/netstack"
 	"github.com/netbirdio/netbird/client/iface/udpmux"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 type TunNetstackDevice struct {

client/iface/udpmux/mux_generic.go

@@ -3,7 +3,7 @@
 package udpmux
 
 import (
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 func (m *SingleSocketUDPMux) notifyAddressRemoval(addr string) {

client/iface/wgproxy/ebpf/proxy.go

@@ -20,7 +20,7 @@ import (
 	"github.com/netbirdio/netbird/client/iface/bufsize"
 	"github.com/netbirdio/netbird/client/internal/ebpf"
 	ebpfMgr "github.com/netbirdio/netbird/client/internal/ebpf/manager"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 const (