refactor: pass in listener to the log receiver

This allows to easily bind to a random part and learn that port.

Signed-off-by: Andrey Smirnov <andrey.smirnov@talos-systems.com>

cmd/siderolink-agent/log_receiver.go

@@ -6,6 +6,7 @@ package main
 
 import (
 	"context"
+	"net"
 
 	"go.uber.org/zap"
 	"golang.org/x/sync/errgroup"
@@ -25,7 +26,12 @@ func logHandler(logger *zap.Logger) logreceiver.Handler {
 }
 
 func logReceiver(ctx context.Context, eg *errgroup.Group, logger *zap.Logger) error {
-	srv, err := logreceiver.NewServer(logger, logReceiverFlags.endpoint, logHandler(logger))
+	lis, err := net.Listen("tcp", logReceiverFlags.endpoint)
+	if err != nil {
+		return err
+	}
+
+	srv, err := logreceiver.NewServer(logger, lis, logHandler(logger))
 	if err != nil {
 		return err
 	}

pkg/logreceiver/server.go

@@ -26,15 +26,10 @@ type Server struct {
 // Handler is called for each received message.
 type Handler func(srcAddress netaddr.IP, msg map[string]interface{})
 
-// NewServer initializes new Server and starts listening.
-func NewServer(logger *zap.Logger, listenAddress string, handler Handler) (*Server, error) {
-	lis, err := net.Listen("tcp", listenAddress)
-	if err != nil {
-		return nil, fmt.Errorf("error listening: %w", err)
-	}
-
+// NewServer initializes new Server.
+func NewServer(logger *zap.Logger, listener net.Listener, handler Handler) (*Server, error) {
 	return &Server{
-		listener: lis,
+		listener: listener,
 		logger:   logger,
 		handler:  handler,
 	}, nil