[client, management] Add port forwarding (#3275)

Add initial support to ingress ports on the client code.

- new types where added
- new protocol messages and controller

client/internal/routemanager/ipfwdstate/ipfwdstate.go

@@ -0,0 +1,51 @@
+package ipfwdstate
+
+import (
+	"fmt"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/internal/routemanager/systemops"
+)
+
+// IPForwardingState is a struct that keeps track of the IP forwarding state.
+// todo: read initial state of the IP forwarding from the system and reset the state based on it
+type IPForwardingState struct {
+	enabledCounter int
+}
+
+func NewIPForwardingState() *IPForwardingState {
+	return &IPForwardingState{}
+}
+
+func (f *IPForwardingState) RequestForwarding() error {
+	if f.enabledCounter != 0 {
+		f.enabledCounter++
+		return nil
+	}
+
+	if err := systemops.EnableIPForwarding(); err != nil {
+		return fmt.Errorf("failed to enable IP forwarding with sysctl: %w", err)
+	}
+	f.enabledCounter = 1
+	log.Info("IP forwarding enabled")
+
+	return nil
+}
+
+func (f *IPForwardingState) ReleaseForwarding() error {
+	if f.enabledCounter == 0 {
+		return nil
+	}
+
+	if f.enabledCounter > 1 {
+		f.enabledCounter--
+		return nil
+	}
+
+	// if failed to disable IP forwarding we anyway decrement the counter
+	f.enabledCounter = 0
+
+	// todo call systemops.DisableIPForwarding()
+	return nil
+}