only print the warning about the UDP receive buffer size once

packet_handler_map.go

@@ -4,6 +4,7 @@ import (
 	"crypto/hmac"
 	"crypto/rand"
 	"crypto/sha256"
+	"errors"
 	"fmt"
 	"hash"
 	"log"
@@ -54,40 +55,38 @@ type packetHandlerMap struct {
 
 var _ packetHandlerManager = &packetHandlerMap{}
 
-func setReceiveBuffer(c net.PacketConn, logger utils.Logger) {
+func setReceiveBuffer(c net.PacketConn, logger utils.Logger) error {
 	conn, ok := c.(interface{ SetReadBuffer(int) error })
 	if !ok {
-		logger.Debugf("Connection doesn't allow setting of receive buffer size")
+		return errors.New("connection doesn't allow setting of receive buffer size")
-		return
 	}
 	size, err := inspectReadBuffer(c)
 	if err != nil {
-		log.Printf("Failed to determine receive buffer size: %s", err)
+		return fmt.Errorf("failed to determine receive buffer size: %w", err)
-		return
 	}
 	if size >= protocol.DesiredReceiveBufferSize {
 		logger.Debugf("Conn has receive buffer of %d kiB (wanted: at least %d kiB)", size/1024, protocol.DesiredReceiveBufferSize/1024)
 	}
 	if err := conn.SetReadBuffer(protocol.DesiredReceiveBufferSize); err != nil {
-		log.Printf("Failed to increase receive buffer size: %s\n", err)
+		return fmt.Errorf("failed to increase receive buffer size: %w", err)
-		return
 	}
 	newSize, err := inspectReadBuffer(c)
 	if err != nil {
-		log.Printf("Failed to determine receive buffer size: %s", err)
+		return fmt.Errorf("failed to determine receive buffer size: %w", err)
-		return
 	}
 	if newSize == size {
-		log.Printf("Failed to determine receive buffer size: %s", err)
+		return fmt.Errorf("failed to determine receive buffer size: %w", err)
-		return
 	}
 	if newSize < protocol.DesiredReceiveBufferSize {
-		log.Printf("Failed to sufficiently increase receive buffer size. Was: %d kiB, wanted: %d kiB, got: %d kiB.", size/1024, protocol.DesiredReceiveBufferSize/1024, newSize/1024)
+		return fmt.Errorf("failed to sufficiently increase receive buffer size (was: %d kiB, wanted: %d kiB, got: %d kiB)", size/1024, protocol.DesiredReceiveBufferSize/1024, newSize/1024)
-		return
 	}
 	logger.Debugf("Increased receive buffer size to %d kiB", newSize/1024)
+	return nil
 }
 
+// only print warnings about the UPD receive buffer size once
+var receiveBufferWarningOnce sync.Once
+
 func newPacketHandlerMap(
 	c net.PacketConn,
 	connIDLen int,
@@ -95,7 +94,11 @@ func newPacketHandlerMap(
 	tracer logging.Tracer,
 	logger utils.Logger,
 ) (packetHandlerManager, error) {
-	setReceiveBuffer(c, logger)
+	if err := setReceiveBuffer(c, logger); err != nil {
+		receiveBufferWarningOnce.Do(func() {
+			log.Println(err)
+		})
+	}
 	conn, err := wrapConn(c)
 	if err != nil {
 		return nil, err

packet_handler_map_test.go

@@ -4,7 +4,10 @@ import (
 	"bytes"
 	"crypto/rand"
 	"errors"
+	"io/ioutil"
+	"log"
 	"net"
+	"os"
 	"time"
 
 	mocklogging "github.com/lucas-clemente/quic-go/internal/mocks/logging"
@@ -63,6 +66,7 @@ var _ = Describe("Packet Handler Map", func() {
 	})
 
 	JustBeforeEach(func() {
+		log.SetOutput(ioutil.Discard)
 		conn = NewMockPacketConn(mockCtrl)
 		conn.EXPECT().LocalAddr().Return(&net.UDPAddr{}).AnyTimes()
 		conn.EXPECT().ReadFrom(gomock.Any()).DoAndReturn(func(b []byte) (int, net.Addr, error) {
@@ -77,6 +81,8 @@ var _ = Describe("Packet Handler Map", func() {
 		handler = phm.(*packetHandlerMap)
 	})
 
+	AfterEach(func() { log.SetOutput(os.Stdout) })
+
 	It("closes", func() {
 		getMultiplexer() // make the sync.Once execute
 		// replace the clientMuxer. getClientMultiplexer will now return the MockMultiplexer