Only carry GSO options in the packet buffer

With this change, GSO options no longer needs to be passed around as
a function argument in the write path.

This change is done in preparation for a later change that defers
segmentation, and may change GSO options for a packet as it flows
down the stack.

Updates #170.

PiperOrigin-RevId: 369774872

14 files changed, 71 insertions, 75 deletions

diff --git a/pkg/tcpip/stack/conntrack.go b/pkg/tcpip/stack/conntrack.go
index 41e964cf3..5720e7543 100644
--- a/pkg/tcpip/stack/conntrack.go
+++ b/pkg/tcpip/stack/conntrack.go
@@ -372,7 +372,7 @@ func (ct *ConnTrack) insertConn(conn *conn) {
 // handlePacket will manipulate the port and address of the packet if the
 // connection exists. Returns whether, after the packet traverses the tables,
 // it should create a new entry in the table.
-func (ct *ConnTrack) handlePacket(pkt *PacketBuffer, hook Hook, gso *GSO, r *Route) bool {
+func (ct *ConnTrack) handlePacket(pkt *PacketBuffer, hook Hook, r *Route) bool {
 	if pkt.NatDone {
 		return false
 	}
@@ -446,7 +446,7 @@ func (ct *ConnTrack) handlePacket(pkt *PacketBuffer, hook Hook, gso *GSO, r *Rou
 		tcpHeader.SetChecksum(0)
 		length := uint16(len(tcpHeader) + pkt.Data().Size())
 		xsum := header.PseudoHeaderChecksum(header.TCPProtocolNumber, netHeader.SourceAddress(), netHeader.DestinationAddress(), length)
-		if gso != nil && gso.NeedsCsum {
+		if pkt.GSOOptions.Type != GSONone && pkt.GSOOptions.NeedsCsum {
 			tcpHeader.SetChecksum(xsum)
 		} else if r.RequiresTXTransportChecksum() {
 			xsum = header.ChecksumCombine(xsum, pkt.Data().AsRange().Checksum())
diff --git a/pkg/tcpip/stack/forwarding_test.go b/pkg/tcpip/stack/forwarding_test.go
index 16ee75bc4..2d74e0abc 100644
--- a/pkg/tcpip/stack/forwarding_test.go
+++ b/pkg/tcpip/stack/forwarding_test.go
@@ -117,7 +117,7 @@ func (f *fwdTestNetworkEndpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNu
 	return f.proto.Number()
 }
 
-func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
+func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
 	// Add the protocol's header to the packet and send it to the link
 	// endpoint.
 	b := pkt.NetworkHeader().Push(fwdTestNetHeaderLen)
@@ -125,11 +125,11 @@ func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, gso *GSO, params NetworkH
 	b[srcAddrOffset] = r.LocalAddress()[0]
 	b[protocolNumberOffset] = byte(params.Protocol)
 
-	return f.nic.WritePacket(r, gso, fwdTestNetNumber, pkt)
+	return f.nic.WritePacket(r, fwdTestNetNumber, pkt)
 }
 
 // WritePackets implements LinkEndpoint.WritePackets.
-func (*fwdTestNetworkEndpoint) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
+func (*fwdTestNetworkEndpoint) WritePackets(r *Route, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
@@ -139,7 +139,7 @@ func (f *fwdTestNetworkEndpoint) WriteHeaderIncludedPacket(r *Route, pkt *Packet
 		return &tcpip.ErrMalformedHeader{}
 	}
 
-	return f.nic.WritePacket(r, nil /* gso */, fwdTestNetNumber, pkt)
+	return f.nic.WritePacket(r, fwdTestNetNumber, pkt)
 }
 
 func (f *fwdTestNetworkEndpoint) Close() {
@@ -322,7 +322,7 @@ func (e *fwdTestLinkEndpoint) LinkAddress() tcpip.LinkAddress {
 	return e.linkAddr
 }
 
-func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	p := fwdTestPacketInfo{
 		RemoteLinkAddress: r.RemoteLinkAddress,
 		LocalLinkAddress:  r.LocalLinkAddress,
@@ -338,10 +338,10 @@ func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, gso *GSO, protocol tcpip.N
 }
 
 // WritePackets stores outbound packets into the channel.
-func (e *fwdTestLinkEndpoint) WritePackets(r RouteInfo, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *fwdTestLinkEndpoint) WritePackets(r RouteInfo, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	n := 0
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-		e.WritePacket(r, gso, protocol, pkt)
+		e.WritePacket(r, protocol, pkt)
 		n++
 	}
 
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go
index 7ea87d325..e2894c548 100644
--- a/pkg/tcpip/stack/iptables.go
+++ b/pkg/tcpip/stack/iptables.go
@@ -267,12 +267,12 @@ const (
 // should continue traversing the network stack and false when it should be
 // dropped.
 //
-// TODO(gvisor.dev/issue/170): PacketBuffer should hold the GSO and route, from
+// TODO(gvisor.dev/issue/170): PacketBuffer should hold the route, from
 // which address can be gathered. Currently, address is only needed for
 // prerouting.
 //
 // Precondition: pkt.NetworkHeader is set.
-func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) bool {
+func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) bool {
 	if pkt.NetworkProtocolNumber != header.IPv4ProtocolNumber && pkt.NetworkProtocolNumber != header.IPv6ProtocolNumber {
 		return true
 	}
@@ -286,7 +286,7 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, prer
 
 	// Packets are manipulated only if connection and matching
 	// NAT rule exists.
-	shouldTrack := it.connections.handlePacket(pkt, hook, gso, r)
+	shouldTrack := it.connections.handlePacket(pkt, hook, r)
 
 	// Go through each table containing the hook.
 	priorities := it.priorities[hook]
@@ -303,7 +303,7 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, prer
 			table = it.v4Tables[tableID]
 		}
 		ruleIdx := table.BuiltinChains[hook]
-		switch verdict := it.checkChain(hook, pkt, table, ruleIdx, gso, r, preroutingAddr, inNicName, outNicName); verdict {
+		switch verdict := it.checkChain(hook, pkt, table, ruleIdx, r, preroutingAddr, inNicName, outNicName); verdict {
 		// If the table returns Accept, move on to the next table.
 		case chainAccept:
 			continue
@@ -314,7 +314,7 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, prer
 			// Any Return from a built-in chain means we have to
 			// call the underflow.
 			underflow := table.Rules[table.Underflows[hook]]
-			switch v, _ := underflow.Target.Action(pkt, &it.connections, hook, gso, r, preroutingAddr); v {
+			switch v, _ := underflow.Target.Action(pkt, &it.connections, hook, r, preroutingAddr); v {
 			case RuleAccept:
 				continue
 			case RuleDrop:
@@ -386,10 +386,10 @@ func (it *IPTables) startReaper(interval time.Duration) {
 //
 // NOTE: unlike the Check API the returned map contains packets that should be
 // dropped.
-func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, gso *GSO, r *Route, inNicName, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
+func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, r *Route, inNicName, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		if !pkt.NatDone {
-			if ok := it.Check(hook, pkt, gso, r, "", inNicName, outNicName); !ok {
+			if ok := it.Check(hook, pkt, r, "", inNicName, outNicName); !ok {
 				if drop == nil {
 					drop = make(map[*PacketBuffer]struct{})
 				}
@@ -409,11 +409,11 @@ func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, gso *GSO, r *
 // Preconditions:
 // * pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
 // * pkt.NetworkHeader is not nil.
-func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, gso *GSO, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) chainVerdict {
+func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) chainVerdict {
 	// Start from ruleIdx and walk the list of rules until a rule gives us
 	// a verdict.
 	for ruleIdx < len(table.Rules) {
-		switch verdict, jumpTo := it.checkRule(hook, pkt, table, ruleIdx, gso, r, preroutingAddr, inNicName, outNicName); verdict {
+		switch verdict, jumpTo := it.checkRule(hook, pkt, table, ruleIdx, r, preroutingAddr, inNicName, outNicName); verdict {
 		case RuleAccept:
 			return chainAccept
 
@@ -430,7 +430,7 @@ func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleId
 				ruleIdx++
 				continue
 			}
-			switch verdict := it.checkChain(hook, pkt, table, jumpTo, gso, r, preroutingAddr, inNicName, outNicName); verdict {
+			switch verdict := it.checkChain(hook, pkt, table, jumpTo, r, preroutingAddr, inNicName, outNicName); verdict {
 			case chainAccept:
 				return chainAccept
 			case chainDrop:
@@ -456,7 +456,7 @@ func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleId
 // Preconditions:
 // * pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
 // * pkt.NetworkHeader is not nil.
-func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, gso *GSO, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) (RuleVerdict, int) {
+func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) (RuleVerdict, int) {
 	rule := table.Rules[ruleIdx]
 
 	// Check whether the packet matches the IP header filter.
@@ -479,7 +479,7 @@ func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx
 	}
 
 	// All the matchers matched, so run the target.
-	return rule.Target.Action(pkt, &it.connections, hook, gso, r, preroutingAddr)
+	return rule.Target.Action(pkt, &it.connections, hook, r, preroutingAddr)
 }
 
 // OriginalDst returns the original destination of redirected connections. It
diff --git a/pkg/tcpip/stack/iptables_targets.go b/pkg/tcpip/stack/iptables_targets.go
index 317efe754..2812c89aa 100644
--- a/pkg/tcpip/stack/iptables_targets.go
+++ b/pkg/tcpip/stack/iptables_targets.go
@@ -29,7 +29,7 @@ type AcceptTarget struct {
 }
 
 // Action implements Target.Action.
-func (*AcceptTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*AcceptTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleAccept, 0
 }
 
@@ -40,7 +40,7 @@ type DropTarget struct {
 }
 
 // Action implements Target.Action.
-func (*DropTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*DropTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleDrop, 0
 }
 
@@ -52,7 +52,7 @@ type ErrorTarget struct {
 }
 
 // Action implements Target.Action.
-func (*ErrorTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*ErrorTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	log.Debugf("ErrorTarget triggered.")
 	return RuleDrop, 0
 }
@@ -67,7 +67,7 @@ type UserChainTarget struct {
 }
 
 // Action implements Target.Action.
-func (*UserChainTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*UserChainTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	panic("UserChainTarget should never be called.")
 }
 
@@ -79,7 +79,7 @@ type ReturnTarget struct {
 }
 
 // Action implements Target.Action.
-func (*ReturnTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*ReturnTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleReturn, 0
 }
 
@@ -103,7 +103,7 @@ type RedirectTarget struct {
 // TODO(gvisor.dev/issue/170): Parse headers without copying. The current
 // implementation only works for Prerouting and calls pkt.Clone(), neither
 // of which should be the case.
-func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso *GSO, r *Route, address tcpip.Address) (RuleVerdict, int) {
+func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, address tcpip.Address) (RuleVerdict, int) {
 	// Sanity check.
 	if rt.NetworkProtocol != pkt.NetworkProtocolNumber {
 		panic(fmt.Sprintf(
@@ -174,7 +174,7 @@ func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gs
 		// packet of the connection comes here. Other packets will be
 		// manipulated in connection tracking.
 		if conn := ct.insertRedirectConn(pkt, hook, rt.Port, address); conn != nil {
-			ct.handlePacket(pkt, hook, gso, r)
+			ct.handlePacket(pkt, hook, r)
 		}
 	default:
 		return RuleDrop, 0
@@ -194,7 +194,7 @@ type SNATTarget struct {
 }
 
 // Action implements Target.Action.
-func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso *GSO, r *Route, address tcpip.Address) (RuleVerdict, int) {
+func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, address tcpip.Address) (RuleVerdict, int) {
 	// Sanity check.
 	if st.NetworkProtocol != pkt.NetworkProtocolNumber {
 		panic(fmt.Sprintf(
@@ -252,7 +252,7 @@ func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso *G
 		// packet of the connection comes here. Other packets will be
 		// manipulated in connection tracking.
 		if conn := ct.insertSNATConn(pkt, hook, st.Port, st.Addr); conn != nil {
-			ct.handlePacket(pkt, hook, gso, r)
+			ct.handlePacket(pkt, hook, r)
 		}
 	default:
 		return RuleDrop, 0
diff --git a/pkg/tcpip/stack/iptables_types.go b/pkg/tcpip/stack/iptables_types.go
index b0d84befb..4631ab93f 100644
--- a/pkg/tcpip/stack/iptables_types.go
+++ b/pkg/tcpip/stack/iptables_types.go
@@ -345,5 +345,5 @@ type Target interface {
 	// Action takes an action on the packet and returns a verdict on how
 	// traversal should (or should not) continue. If the return value is
 	// Jump, it also returns the index of the rule to jump to.
-	Action(packet *PacketBuffer, connections *ConnTrack, hook Hook, gso *GSO, r *Route, address tcpip.Address) (RuleVerdict, int)
+	Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int)
 }
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index ca15c0691..8d615500f 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -316,30 +316,30 @@ func (n *nic) IsLoopback() bool {
 }
 
 // WritePacket implements NetworkLinkEndpoint.
-func (n *nic) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
-	_, err := n.enqueuePacketBuffer(r, gso, protocol, pkt)
+func (n *nic) WritePacket(r *Route, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+	_, err := n.enqueuePacketBuffer(r, protocol, pkt)
 	return err
 }
 
-func (n *nic) writePacketBuffer(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
+func (n *nic) writePacketBuffer(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	switch pkt := pkt.(type) {
 	case *PacketBuffer:
-		if err := n.writePacket(r, gso, protocol, pkt); err != nil {
+		if err := n.writePacket(r, protocol, pkt); err != nil {
 			return 0, err
 		}
 		return 1, nil
 	case *PacketBufferList:
-		return n.writePackets(r, gso, protocol, *pkt)
+		return n.writePackets(r, protocol, *pkt)
 	default:
 		panic(fmt.Sprintf("unrecognized pending packet buffer type = %T", pkt))
 	}
 }
 
-func (n *nic) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
+func (n *nic) enqueuePacketBuffer(r *Route, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	routeInfo, _, err := r.resolvedFields(nil)
 	switch err.(type) {
 	case nil:
-		return n.writePacketBuffer(routeInfo, gso, protocol, pkt)
+		return n.writePacketBuffer(routeInfo, protocol, pkt)
 	case *tcpip.ErrWouldBlock:
 		// As per relevant RFCs, we should queue packets while we wait for link
 		// resolution to complete.
@@ -358,28 +358,27 @@ func (n *nic) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProt
 		//   SHOULD be limited to some small value. When a queue overflows, the new
 		//   arrival SHOULD replace the oldest entry. Once address resolution
 		//   completes, the node transmits any queued packets.
-		return n.linkResQueue.enqueue(r, gso, protocol, pkt)
+		return n.linkResQueue.enqueue(r, protocol, pkt)
 	default:
 		return 0, err
 	}
 }
 
 // WritePacketToRemote implements NetworkInterface.
-func (n *nic) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+func (n *nic) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	var r RouteInfo
 	r.NetProto = protocol
 	r.RemoteLinkAddress = remoteLinkAddr
-	return n.writePacket(r, gso, protocol, pkt)
+	return n.writePacket(r, protocol, pkt)
 }
 
-func (n *nic) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+func (n *nic) writePacket(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	// WritePacket takes ownership of pkt, calculate numBytes first.
 	numBytes := pkt.Size()
 
 	pkt.EgressRoute = r
-	pkt.GSOOptions = gso
 	pkt.NetworkProtocolNumber = protocol
-	if err := n.LinkEndpoint.WritePacket(r, gso, protocol, pkt); err != nil {
+	if err := n.LinkEndpoint.WritePacket(r, protocol, pkt); err != nil {
 		return err
 	}
 
@@ -389,18 +388,17 @@ func (n *nic) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolN
 }
 
 // WritePackets implements NetworkLinkEndpoint.
-func (n *nic) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
-	return n.enqueuePacketBuffer(r, gso, protocol, &pkts)
+func (n *nic) WritePackets(r *Route, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+	return n.enqueuePacketBuffer(r, protocol, &pkts)
 }
 
-func (n *nic) writePackets(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkts PacketBufferList) (int, tcpip.Error) {
+func (n *nic) writePackets(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkts PacketBufferList) (int, tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		pkt.EgressRoute = r
-		pkt.GSOOptions = gso
 		pkt.NetworkProtocolNumber = protocol
 	}
 
-	writtenPackets, err := n.LinkEndpoint.WritePackets(r, gso, pkts, protocol)
+	writtenPackets, err := n.LinkEndpoint.WritePackets(r, pkts, protocol)
 	n.stats.Tx.Packets.IncrementBy(uint64(writtenPackets))
 	writtenBytes := 0
 	for i, pb := 0, pkts.Front(); i < writtenPackets && pb != nil; i, pb = i+1, pb.Next() {
diff --git a/pkg/tcpip/stack/nic_test.go b/pkg/tcpip/stack/nic_test.go
index c0f956e53..8a3005295 100644
--- a/pkg/tcpip/stack/nic_test.go
+++ b/pkg/tcpip/stack/nic_test.go
@@ -65,12 +65,12 @@ func (e *testIPv6Endpoint) MaxHeaderLength() uint16 {
 }
 
 // WritePacket implements NetworkEndpoint.WritePacket.
-func (*testIPv6Endpoint) WritePacket(*Route, *GSO, NetworkHeaderParams, *PacketBuffer) tcpip.Error {
+func (*testIPv6Endpoint) WritePacket(*Route, NetworkHeaderParams, *PacketBuffer) tcpip.Error {
 	return nil
 }
 
 // WritePackets implements NetworkEndpoint.WritePackets.
-func (*testIPv6Endpoint) WritePackets(*Route, *GSO, PacketBufferList, NetworkHeaderParams) (int, tcpip.Error) {
+func (*testIPv6Endpoint) WritePackets(*Route, PacketBufferList, NetworkHeaderParams) (int, tcpip.Error) {
 	// Our tests don't use this so we don't support it.
 	return 0, &tcpip.ErrNotSupported{}
 }
diff --git a/pkg/tcpip/stack/packet_buffer.go b/pkg/tcpip/stack/packet_buffer.go
index c10304d5f..646979d1e 100644
--- a/pkg/tcpip/stack/packet_buffer.go
+++ b/pkg/tcpip/stack/packet_buffer.go
@@ -103,7 +103,7 @@ type PacketBuffer struct {
 	// The following fields are only set by the qdisc layer when the packet
 	// is added to a queue.
 	EgressRoute RouteInfo
-	GSOOptions  *GSO
+	GSOOptions  GSO
 
 	// NatDone indicates if the packet has been manipulated as per NAT
 	// iptables rule.
diff --git a/pkg/tcpip/stack/pending_packets.go b/pkg/tcpip/stack/pending_packets.go
index e936aa728..13e8907ec 100644
--- a/pkg/tcpip/stack/pending_packets.go
+++ b/pkg/tcpip/stack/pending_packets.go
@@ -46,7 +46,6 @@ func (p *PacketBufferList) len() int {
 
 type pendingPacket struct {
 	routeInfo RouteInfo
-	gso       *GSO
 	proto     tcpip.NetworkProtocolNumber
 	pkt       pendingPacketBuffer
 }
@@ -119,7 +118,7 @@ func (f *packetsPendingLinkResolution) dequeue(ch <-chan struct{}, linkAddr tcpi
 // If the maximum number of pending resolutions is reached, the packets
 // associated with the oldest link resolution will be dequeued as if they failed
 // link resolution.
-func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
+func (f *packetsPendingLinkResolution) enqueue(r *Route, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	f.mu.Lock()
 	// Make sure we attempt resolution while holding f's lock so that we avoid
 	// a race where link resolution completes before we enqueue the packets.
@@ -137,7 +136,7 @@ func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.N
 		// The route resolved immediately, so we don't need to wait for link
 		// resolution to send the packet.
 		f.mu.Unlock()
-		return f.nic.writePacketBuffer(routeInfo, gso, proto, pkt)
+		return f.nic.writePacketBuffer(routeInfo, proto, pkt)
 	case *tcpip.ErrWouldBlock:
 		// We need to wait for link resolution to complete.
 	default:
@@ -150,7 +149,6 @@ func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.N
 	packets, ok := f.mu.packets[ch]
 	packets = append(packets, pendingPacket{
 		routeInfo: routeInfo,
-		gso:       gso,
 		proto:     proto,
 		pkt:       pkt,
 	})
@@ -211,7 +209,7 @@ func (f *packetsPendingLinkResolution) dequeuePackets(packets []pendingPacket, l
 	for _, p := range packets {
 		if err == nil {
 			p.routeInfo.RemoteLinkAddress = linkAddr
-			_, _ = f.nic.writePacketBuffer(p.routeInfo, p.gso, p.proto, p.pkt)
+			_, _ = f.nic.writePacketBuffer(p.routeInfo, p.proto, p.pkt)
 		} else {
 			f.incrementOutgoingPacketErrors(p.proto, p.pkt)
 
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index ff3a385e1..7ad206f6d 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -537,14 +537,14 @@ type NetworkInterface interface {
 	CheckLocalAddress(tcpip.NetworkProtocolNumber, tcpip.Address) bool
 
 	// WritePacketToRemote writes the packet to the given remote link address.
-	WritePacketToRemote(tcpip.LinkAddress, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
+	WritePacketToRemote(tcpip.LinkAddress, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePacket writes a packet with the given protocol through the given
 	// route.
 	//
 	// WritePacket takes ownership of the packet buffer. The packet buffer's
 	// network and transport header must be set.
-	WritePacket(*Route, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
+	WritePacket(*Route, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets with the given protocol through the given
 	// route. Must not be called with an empty list of packet buffers.
@@ -554,7 +554,7 @@ type NetworkInterface interface {
 	// Right now, WritePackets is used only when the software segmentation
 	// offload is enabled. If it will be used for something else, syscall filters
 	// may need to be updated.
-	WritePackets(*Route, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
+	WritePackets(*Route, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
 
 	// HandleNeighborProbe processes an incoming neighbor probe (e.g. ARP
 	// request or NDP Neighbor Solicitation).
@@ -610,12 +610,12 @@ type NetworkEndpoint interface {
 	// WritePacket writes a packet to the given destination address and
 	// protocol. It takes ownership of pkt. pkt.TransportHeader must have
 	// already been set.
-	WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error
+	WritePacket(r *Route, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets to the given destination address and
 	// protocol. pkts must not be zero length. It takes ownership of pkts and
 	// underlying packets.
-	WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error)
+	WritePackets(r *Route, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error)
 
 	// WriteHeaderIncludedPacket writes a packet that includes a network
 	// header to the given destination address. It takes ownership of pkt.
@@ -832,7 +832,7 @@ 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(RouteInfo, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
+	WritePacket(RouteInfo, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets with the given protocol and route. Must not be
 	// called with an empty list of packet buffers.
@@ -842,7 +842,7 @@ type LinkEndpoint interface {
 	// Right now, WritePackets is used only when the software segmentation
 	// offload is enabled. If it will be used for something else, syscall filters
 	// may need to be updated.
-	WritePackets(RouteInfo, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
+	WritePackets(RouteInfo, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
 }
 
 // InjectableLinkEndpoint is a LinkEndpoint where inbound packets are
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 4ae6bed5a..4ecde5995 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -448,22 +448,22 @@ func (r *Route) isValidForOutgoingRLocked() bool {
 }
 
 // WritePacket writes the packet through the given route.
-func (r *Route) WritePacket(gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
+func (r *Route) WritePacket(params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
 	if !r.isValidForOutgoing() {
 		return &tcpip.ErrInvalidEndpointState{}
 	}
 
-	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePacket(r, gso, params, pkt)
+	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePacket(r, params, pkt)
 }
 
 // WritePackets writes a list of n packets through the given route and returns
 // the number of packets written.
-func (r *Route) WritePackets(gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
+func (r *Route) WritePackets(pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
 	if !r.isValidForOutgoing() {
 		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
-	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePackets(r, gso, pkts, params)
+	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePackets(r, pkts, params)
 }
 
 // WriteHeaderIncludedPacket writes a packet already containing a network
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index 21cfbad71..843118b13 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -1573,7 +1573,7 @@ func (s *Stack) WritePacketToRemote(nicID tcpip.NICID, remote tcpip.LinkAddress,
 		ReserveHeaderBytes: int(nic.MaxHeaderLength()),
 		Data:               payload,
 	})
-	return nic.WritePacketToRemote(remote, nil, netProto, pkt)
+	return nic.WritePacketToRemote(remote, netProto, pkt)
 }
 
 // NetworkProtocolInstance returns the protocol instance in the stack for the
diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index a0bd69d9a..8ead3b8df 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -171,7 +171,7 @@ func (f *fakeNetworkEndpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumbe
 	return f.proto.Number()
 }
 
-func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
+func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
 	// Increment the sent packet count in the protocol descriptor.
 	f.proto.sendPacketCount[int(r.RemoteAddress()[0])%len(f.proto.sendPacketCount)]++
 
@@ -190,11 +190,11 @@ func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, params
 		return nil
 	}
 
-	return f.nic.WritePacket(r, gso, fakeNetNumber, pkt)
+	return f.nic.WritePacket(r, fakeNetNumber, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (*fakeNetworkEndpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
+func (*fakeNetworkEndpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
@@ -437,7 +437,7 @@ func sendTo(s *stack.Stack, addr tcpip.Address, payload buffer.View) tcpip.Error
 }
 
 func send(r *stack.Route, payload buffer.View) tcpip.Error {
-	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, stack.NewPacketBuffer(stack.PacketBufferOptions{
+	return r.WritePacket(stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: int(r.MaxHeaderLength()),
 		Data:               payload.ToVectorisedView(),
 	}))
@@ -1462,7 +1462,7 @@ func TestExternalSendWithHandleLocal(t *testing.T) {
 					if n := ep.Drain(); n != 0 {
 						t.Fatalf("got ep.Drain() = %d, want = 0", n)
 					}
-					if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
+					if err := r.WritePacket(stack.NetworkHeaderParams{
 						Protocol: fakeTransNumber,
 						TTL:      123,
 						TOS:      stack.DefaultTOS,
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 0adedd7c0..839178809 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -106,7 +106,7 @@ func (f *fakeTransportEndpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions
 		Data:               buffer.View(v).ToVectorisedView(),
 	})
 	_ = pkt.TransportHeader().Push(fakeTransHeaderLen)
-	if err := f.route.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, pkt); err != nil {
+	if err := f.route.WritePacket(stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, pkt); err != nil {
 		return 0, err
 	}