disable GSO if sending fails for a particular remote address

send_conn_test.go

@@ -2,46 +2,81 @@ package quic
 
 import (
 	"net"
+	"net/netip"
 
+	"github.com/quic-go/quic-go/internal/utils"
+
+	"github.com/golang/mock/gomock"
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 )
 
+// Only if appendUDPSegmentSizeMsg actually appends a message (and isn't only a stub implementation),
+// GSO is actually supported on this platform.
+var platformSupportsGSO = len(appendUDPSegmentSizeMsg([]byte{}, 1337)) > 0
+
 var _ = Describe("Connection (for sending packets)", func() {
-	var (
-		c          sendConn
-		packetConn *MockPacketConn
-		addr       net.Addr
-	)
+	remoteAddr := &net.UDPAddr{IP: net.IPv4(192, 168, 100, 200), Port: 1337}
 
-	BeforeEach(func() {
-		addr = &net.UDPAddr{IP: net.IPv4(192, 168, 100, 200), Port: 1337}
-		packetConn = NewMockPacketConn(mockCtrl)
-		rawConn, err := wrapConn(packetConn)
-		Expect(err).ToNot(HaveOccurred())
-		c = newSendConnWithPacketInfo(rawConn, addr, packetInfo{})
-	})
-
-	It("writes", func() {
-		packetConn.EXPECT().WriteTo([]byte("foobar"), addr)
-		Expect(c.Write([]byte("foobar"), 6)).To(Succeed())
-	})
-
-	It("gets the remote address", func() {
+	It("gets the local and remote addresses", func() {
+		localAddr := &net.UDPAddr{IP: net.IPv4(192, 168, 0, 1), Port: 1234}
+		rawConn := NewMockRawConn(mockCtrl)
+		rawConn.EXPECT().LocalAddr().Return(localAddr)
+		c := newSendConn(rawConn, remoteAddr, packetInfo{}, utils.DefaultLogger)
+		Expect(c.LocalAddr().String()).To(Equal("192.168.0.1:1234"))
 		Expect(c.RemoteAddr().String()).To(Equal("192.168.100.200:1337"))
 	})
 
-	It("gets the local address", func() {
-		addr := &net.UDPAddr{
-			IP:   net.IPv4(192, 168, 0, 1),
-			Port: 1234,
-		}
-		packetConn.EXPECT().LocalAddr().Return(addr)
-		Expect(c.LocalAddr()).To(Equal(addr))
+	It("uses the local address from the packet info", func() {
+		localAddr := &net.UDPAddr{IP: net.IPv4(192, 168, 0, 1), Port: 1234}
+		rawConn := NewMockRawConn(mockCtrl)
+		rawConn.EXPECT().LocalAddr().Return(localAddr)
+		c := newSendConn(rawConn, remoteAddr, packetInfo{addr: netip.AddrFrom4([4]byte{127, 0, 0, 42})}, utils.DefaultLogger)
+		Expect(c.LocalAddr().String()).To(Equal("127.0.0.42:1234"))
 	})
 
-	It("closes", func() {
-		packetConn.EXPECT().Close()
-		Expect(c.Close()).To(Succeed())
-	})
+	if platformSupportsGSO {
+		It("writes with GSO", func() {
+			rawConn := NewMockRawConn(mockCtrl)
+			rawConn.EXPECT().LocalAddr()
+			rawConn.EXPECT().capabilities().Return(connCapabilities{GSO: true}).AnyTimes()
+			c := newSendConn(rawConn, remoteAddr, packetInfo{}, utils.DefaultLogger)
+			rawConn.EXPECT().WritePacket([]byte("foobar"), remoteAddr, gomock.Any()).Do(func(_ []byte, _ net.Addr, oob []byte) {
+				msg := appendUDPSegmentSizeMsg([]byte{}, 3)
+				Expect(oob).To(Equal(msg))
+			})
+			Expect(c.Write([]byte("foobar"), 3)).To(Succeed())
+		})
+
+		It("disables GSO if writing fails", func() {
+			rawConn := NewMockRawConn(mockCtrl)
+			rawConn.EXPECT().LocalAddr()
+			rawConn.EXPECT().capabilities().Return(connCapabilities{GSO: true}).AnyTimes()
+			c := newSendConn(rawConn, remoteAddr, packetInfo{}, utils.DefaultLogger)
+			Expect(c.capabilities().GSO).To(BeTrue())
+			gomock.InOrder(
+				rawConn.EXPECT().WritePacket([]byte("foobar"), remoteAddr, gomock.Any()).DoAndReturn(func(_ []byte, _ net.Addr, oob []byte) (int, error) {
+					msg := appendUDPSegmentSizeMsg([]byte{}, 3)
+					Expect(oob).To(Equal(msg))
+					return 0, errGSO
+				}),
+				rawConn.EXPECT().WritePacket([]byte("foo"), remoteAddr, []byte{}).Return(3, nil),
+				rawConn.EXPECT().WritePacket([]byte("bar"), remoteAddr, []byte{}).Return(3, nil),
+			)
+			Expect(c.Write([]byte("foobar"), 3)).To(Succeed())
+			Expect(c.capabilities().GSO).To(BeFalse()) // GSO support is now disabled
+			// make sure we actually enforce that
+			Expect(func() { c.Write([]byte("foobar"), 3) }).To(PanicWith("inconsistent packet size (6 vs 3)"))
+		})
+	} else {
+		It("writes without GSO", func() {
+			remoteAddr := &net.UDPAddr{IP: net.IPv4(192, 168, 100, 200), Port: 1337}
+			rawConn := NewMockRawConn(mockCtrl)
+			rawConn.EXPECT().LocalAddr()
+			rawConn.EXPECT().capabilities()
+			c := newSendConn(rawConn, remoteAddr, packetInfo{}, utils.DefaultLogger)
+			rawConn.EXPECT().WritePacket([]byte("foobar"), remoteAddr, nil)
+			Expect(c.Write([]byte("foobar"), 6)).To(Succeed())
+		})
+	}
 })