5 files changed, 38 insertions, 4 deletions
diff --git a/pkg/tcpip/link/channel/channel.go b/pkg/tcpip/link/channel/channel.go
index 8c0d11288..f7501a1bc 100644
--- a/pkg/tcpip/link/channel/channel.go
+++ b/pkg/tcpip/link/channel/channel.go
@@ -28,6 +28,7 @@ type PacketInfo struct {
 	Header  buffer.View
 	Payload buffer.View
 	Proto   tcpip.NetworkProtocolNumber
+	GSO     *stack.GSO
 }
 
 // Endpoint is link layer endpoint that stores outbound packets in a channel
@@ -36,6 +37,7 @@ type Endpoint struct {
 	dispatcher stack.NetworkDispatcher
 	mtu        uint32
 	linkAddr   tcpip.LinkAddress
+	GSO        bool
 
 	// C is where outbound packets are queued.
 	C chan PacketInfo
@@ -93,8 +95,17 @@ func (e *Endpoint) MTU() uint32 {
 }
 
 // Capabilities implements stack.LinkEndpoint.Capabilities.
-func (*Endpoint) Capabilities() stack.LinkEndpointCapabilities {
-	return 0
+func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
+	caps := stack.LinkEndpointCapabilities(0)
+	if e.GSO {
+		caps |= stack.CapabilityGSO
+	}
+	return caps
+}
+
+// GSOMaxSize returns the maximum GSO packet size.
+func (*Endpoint) GSOMaxSize() uint32 {
+	return 1 << 15
 }
 
 // MaxHeaderLength returns the maximum size of the link layer header. Given it
@@ -109,11 +120,12 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 }
 
 // WritePacket stores outbound packets into the channel.
-func (e *Endpoint) WritePacket(_ *stack.Route, _ *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (e *Endpoint) WritePacket(_ *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
 	p := PacketInfo{
 		Header:  hdr.View(),
 		Proto:   protocol,
 		Payload: payload.ToView(),
+		GSO:     gso,
 	}
 
 	select {
diff --git a/pkg/tcpip/link/fdbased/endpoint_test.go b/pkg/tcpip/link/fdbased/endpoint_test.go
index 5a06c6387..c8b037d57 100644
--- a/pkg/tcpip/link/fdbased/endpoint_test.go
+++ b/pkg/tcpip/link/fdbased/endpoint_test.go
@@ -166,6 +166,7 @@ func testWritePacket(t *testing.T, plen int, eth bool, gsoMaxSize uint32) {
 			CsumOffset: csumOffset,
 			MSS:        gsoMSS,
 			MaxSize:    gsoMaxSize,
+			L3HdrLen:   header.IPv4MaximumHeaderSize,
 		}
 	}
 	if err := c.ep.WritePacket(r, gso, hdr, payload.ToVectorisedView(), proto); err != nil {
diff --git a/pkg/tcpip/transport/tcp/dual_stack_test.go b/pkg/tcpip/transport/tcp/dual_stack_test.go
index 52f20bef1..2886cc707 100644
--- a/pkg/tcpip/transport/tcp/dual_stack_test.go
+++ b/pkg/tcpip/transport/tcp/dual_stack_test.go
@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/checker"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/network/ipv4"
@@ -330,6 +331,9 @@ func TestV6RefuseOnBoundToV4Mapped(t *testing.T) {
 }
 
 func testV4Accept(t *testing.T, c *context.Context) {
+	c.SetGSOEnabled(true)
+	defer c.SetGSOEnabled(false)
+
 	// Start listening.
 	if err := c.EP.Listen(10); err != nil {
 		t.Fatalf("Listen failed: %v", err)
@@ -406,6 +410,14 @@ func testV4Accept(t *testing.T, c *context.Context) {
 	if addr.Addr != context.TestAddr {
 		t.Fatalf("Unexpected remote address: got %v, want %v", addr.Addr, context.TestAddr)
 	}
+
+	data := "Don't panic"
+	nep.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{})
+	b = c.GetPacket()
+	tcp = header.TCP(header.IPv4(b).Payload())
+	if string(tcp.Payload()) != data {
+		t.Fatalf("Unexpected data: got %v, want %v", string(tcp.Payload()), data)
+	}
 }
 
 func TestV4AcceptOnV6(t *testing.T) {
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index b5d05af7d..c0b785431 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1717,7 +1717,7 @@ func (e *endpoint) initGSO() {
 	}
 
 	gso := &stack.GSO{}
-	switch e.netProto {
+	switch e.route.NetProto {
 	case header.IPv4ProtocolNumber:
 		gso.Type = stack.GSOTCPv4
 		gso.L3HdrLen = header.IPv4MinimumSize
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index 8ac411b1d..6e2fed880 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -234,6 +234,10 @@ func (c *Context) GetPacket() []byte {
 		copy(b, p.Header)
 		copy(b[len(p.Header):], p.Payload)
 
+		if p.GSO != nil && p.GSO.L3HdrLen != header.IPv4MinimumSize {
+			c.t.Errorf("L3HdrLen %v (expected %v)", p.GSO.L3HdrLen, header.IPv4MinimumSize)
+		}
+
 		checker.IPv4(c.t, b, checker.SrcAddr(StackAddr), checker.DstAddr(TestAddr))
 		return b
 
@@ -956,3 +960,8 @@ func (c *Context) SACKEnabled() bool {
 	}
 	return bool(v)
 }
+
+// SetGSOEnabled enables or disables generic segmentation offload.
+func (c *Context) SetGSOEnabled(enable bool) {
+	c.linkEP.GSO = enable
+}