Add support for UDP routing in systemd socket activation

pkg/server/socket_activation_unix.go

@@ -9,16 +9,36 @@ import (
 	"github.com/rs/zerolog/log"
 )
 
-func populateSocketActivationListeners() {
-	listenersWithName, _ := activation.ListenersWithNames()
+func populateSocketActivationListeners() *SocketActivation {
+	// We use Files api due to activation not providing method for get PacketConn with names
+	files := activation.Files(true)
+	sa := &SocketActivation{enabled: false}
+	sa.listeners = make(map[string]net.Listener)
+	sa.conns = make(map[string]net.PacketConn)
 
-	socketActivationListeners = make(map[string]net.Listener)
-	for name, lns := range listenersWithName {
-		if len(lns) != 1 {
-			log.Error().Str("listenersName", name).Msg("Socket activation listeners must have one and only one listener per name")
-			continue
+	if len(files) > 0 {
+		sa.enabled = true
+
+		for _, f := range files {
+			if lc, err := net.FileListener(f); err == nil {
+				_, ok := sa.listeners[f.Name()]
+				if ok {
+					log.Error().Str("listenersName", f.Name()).Msg("Socket activation TCP listeners must have one and only one listener per name")
+				} else {
+					sa.listeners[f.Name()] = lc
+				}
+				f.Close()
+			} else if pc, err := net.FilePacketConn(f); err == nil {
+				_, ok := sa.conns[f.Name()]
+				if ok {
+					log.Error().Str("listenersName", f.Name()).Msg("Socket activation UDP listeners must have one and only one listener per name")
+				} else {
+					sa.conns[f.Name()] = pc
+				}
+				f.Close()
+			}
 		}
-
-		socketActivationListeners[name] = lns[0]
 	}
+
+	return sa
 }