5 files changed, 56 insertions, 9 deletions
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 1d032ebf8..8b6c17a90 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -486,7 +486,7 @@ func (n *NIC) DeliverNetworkPacket(linkEP LinkEndpoint, remote, _ tcpip.LinkAddr
 			vv.RemoveFirst()
 
 			// TODO: use route.WritePacket.
-			if err := n.linkEP.WritePacket(&r, hdr, vv, protocol); err != nil {
+			if err := n.linkEP.WritePacket(&r, nil /* gso */, hdr, vv, protocol); err != nil {
 				r.Stats().IP.OutgoingPacketErrors.Increment()
 			} else {
 				n.stats.Tx.Packets.Increment()
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index cf4d52fe9..ff356ea22 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -161,7 +161,7 @@ type NetworkEndpoint interface {
 
 	// WritePacket writes a packet to the given destination address and
 	// protocol.
-	WritePacket(r *Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8, loop PacketLooping) *tcpip.Error
+	WritePacket(r *Route, gso *GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8, loop PacketLooping) *tcpip.Error
 
 	// ID returns the network protocol endpoint ID.
 	ID() *NetworkEndpointID
@@ -226,6 +226,7 @@ const (
 	CapabilitySaveRestore
 	CapabilityDisconnectOk
 	CapabilityLoopback
+	CapabilityGSO
 )
 
 // LinkEndpoint is the interface implemented by data link layer protocols (e.g.,
@@ -258,7 +259,7 @@ type LinkEndpoint interface {
 	// To participate in transparent bridging, a LinkEndpoint implementation
 	// should call eth.Encode with header.EthernetFields.SrcAddr set to
 	// r.LocalLinkAddress if it is provided.
-	WritePacket(r *Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error
+	WritePacket(r *Route, gso *GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error
 
 	// Attach attaches the data link layer endpoint to the network-layer
 	// dispatcher of the stack.
@@ -381,3 +382,41 @@ func FindLinkEndpoint(id tcpip.LinkEndpointID) LinkEndpoint {
 
 	return linkEndpoints[id]
 }
+
+// GSOType is the type of GSO segments.
+//
+// +stateify savable
+type GSOType int
+
+// Types of gso segments.
+const (
+	GSONone GSOType = iota
+	GSOTCPv4
+	GSOTCPv6
+)
+
+// GSO contains generic segmentation offload properties.
+//
+// +stateify savable
+type GSO struct {
+	// Type is one of GSONone, GSOTCPv4, etc.
+	Type GSOType
+	// NeedsCsum is set if the checksum offload is enabled.
+	NeedsCsum bool
+	// CsumOffset is offset after that to place checksum.
+	CsumOffset uint16
+
+	// Mss is maximum segment size.
+	MSS uint16
+	// L3Len is L3 (IP) header length.
+	L3HdrLen uint16
+
+	// MaxSize is maximum GSO packet size.
+	MaxSize uint32
+}
+
+// GSOEndpoint provides access to GSO properties.
+type GSOEndpoint interface {
+	// GSOMaxSize returns the maximum GSO packet size.
+	GSOMaxSize() uint32
+}
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index ee860eafe..8ae562dcd 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -97,6 +97,14 @@ func (r *Route) Capabilities() LinkEndpointCapabilities {
 	return r.ref.ep.Capabilities()
 }
 
+// GSOMaxSize returns the maximum GSO packet size.
+func (r *Route) GSOMaxSize() uint32 {
+	if gso, ok := r.ref.ep.(GSOEndpoint); ok {
+		return gso.GSOMaxSize()
+	}
+	return 0
+}
+
 // Resolve attempts to resolve the link address if necessary. Returns ErrWouldBlock in
 // case address resolution requires blocking, e.g. wait for ARP reply. Waker is
 // notified when address resolution is complete (success or not).
@@ -144,8 +152,8 @@ func (r *Route) IsResolutionRequired() bool {
 }
 
 // WritePacket writes the packet through the given route.
-func (r *Route) WritePacket(hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8) *tcpip.Error {
-	err := r.ref.ep.WritePacket(r, hdr, payload, protocol, ttl, r.loop)
+func (r *Route) WritePacket(gso *GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8) *tcpip.Error {
+	err := r.ref.ep.WritePacket(r, gso, hdr, payload, protocol, ttl, r.loop)
 	if err != nil {
 		r.Stats().IP.OutgoingPacketErrors.Increment()
 	} else {
diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index da8269999..b5375df3c 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -112,7 +112,7 @@ func (f *fakeNetworkEndpoint) Capabilities() stack.LinkEndpointCapabilities {
 	return f.linkEP.Capabilities()
 }
 
-func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, _ uint8, loop stack.PacketLooping) *tcpip.Error {
+func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, _ uint8, loop stack.PacketLooping) *tcpip.Error {
 	// Increment the sent packet count in the protocol descriptor.
 	f.proto.sendPacketCount[int(r.RemoteAddress[0])%len(f.proto.sendPacketCount)]++
 
@@ -134,7 +134,7 @@ func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, hdr buffer.Prependable
 		return nil
 	}
 
-	return f.linkEP.WritePacket(r, hdr, payload, fakeNetNumber)
+	return f.linkEP.WritePacket(r, gso, hdr, payload, fakeNetNumber)
 }
 
 func (*fakeNetworkEndpoint) Close() {}
@@ -281,7 +281,7 @@ func sendTo(t *testing.T, s *stack.Stack, addr tcpip.Address, payload buffer.Vie
 	defer r.Release()
 
 	hdr := buffer.NewPrependable(int(r.MaxHeaderLength()))
-	if err := r.WritePacket(hdr, payload.ToVectorisedView(), fakeTransNumber, 123); err != nil {
+	if err := r.WritePacket(nil /* gso */, hdr, payload.ToVectorisedView(), fakeTransNumber, 123); err != nil {
 		t.Errorf("WritePacket failed: %v", err)
 	}
 }
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 279ab3c56..dfd31557a 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -74,7 +74,7 @@ func (f *fakeTransportEndpoint) Write(p tcpip.Payload, opts tcpip.WriteOptions)
 	if err != nil {
 		return 0, nil, err
 	}
-	if err := f.route.WritePacket(hdr, buffer.View(v).ToVectorisedView(), fakeTransNumber, 123); err != nil {
+	if err := f.route.WritePacket(nil /* gso */, hdr, buffer.View(v).ToVectorisedView(), fakeTransNumber, 123); err != nil {
 		return 0, nil, err
 	}