Pass PacketBuffer as pointer.

Historically we've been passing PacketBuffer by shallow copying through out
the stack. Right now, this is only correct as the caller would not use
PacketBuffer after passing into the next layer in netstack.

With new buffer management effort in gVisor/netstack, PacketBuffer will
own a Buffer (to be added). Internally, both PacketBuffer and Buffer may
have pointers and shallow copying shouldn't be used.

Updates #2404.

PiperOrigin-RevId: 314610879

15 files changed, 37 insertions, 33 deletions

diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index b1d820372..29ff68df3 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -450,7 +450,7 @@ func send4(r *stack.Route, ident uint16, data buffer.View, ttl uint8, owner tcpi
 	if ttl == 0 {
 		ttl = r.DefaultTTL()
 	}
-	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, stack.PacketBuffer{
+	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, &stack.PacketBuffer{
 		Header:          hdr,
 		Data:            data.ToVectorisedView(),
 		TransportHeader: buffer.View(icmpv4),
@@ -481,7 +481,7 @@ func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) *tcpip.Err
 	if ttl == 0 {
 		ttl = r.DefaultTTL()
 	}
-	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, stack.PacketBuffer{
+	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, &stack.PacketBuffer{
 		Header:          hdr,
 		Data:            dataVV,
 		TransportHeader: buffer.View(icmpv6),
@@ -743,7 +743,7 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 
 // HandlePacket is called by the stack when new packets arrive to this transport
 // endpoint.
-func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) {
+func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {
 	// Only accept echo replies.
 	switch e.NetProto {
 	case header.IPv4ProtocolNumber:
@@ -805,7 +805,7 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
 }
 
 // HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket.
-func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, pkt stack.PacketBuffer) {
+func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, pkt *stack.PacketBuffer) {
 }
 
 // State implements tcpip.Endpoint.State. The ICMP endpoint currently doesn't
diff --git a/pkg/tcpip/transport/icmp/protocol.go b/pkg/tcpip/transport/icmp/protocol.go
index 3c47692b2..2ec6749c7 100644
--- a/pkg/tcpip/transport/icmp/protocol.go
+++ b/pkg/tcpip/transport/icmp/protocol.go
@@ -104,7 +104,7 @@ func (p *protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error)
 
 // HandleUnknownDestinationPacket handles packets targeted at this protocol but
 // that don't match any existing endpoint.
-func (*protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, stack.PacketBuffer) bool {
+func (*protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, *stack.PacketBuffer) bool {
 	return true
 }
 
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 23158173d..bab2d63ae 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -298,7 +298,7 @@ func (ep *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 }
 
 // HandlePacket implements stack.PacketEndpoint.HandlePacket.
-func (ep *endpoint) HandlePacket(nicID tcpip.NICID, localAddr tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, pkt stack.PacketBuffer) {
+func (ep *endpoint) HandlePacket(nicID tcpip.NICID, localAddr tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
 	ep.rcvMu.Lock()
 
 	// Drop the packet if our buffer is currently full.
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index eee754a5a..25a17940d 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -348,7 +348,7 @@ func (e *endpoint) finishWrite(payloadBytes []byte, route *stack.Route) (int64,
 	switch e.NetProto {
 	case header.IPv4ProtocolNumber:
 		if !e.associated {
-			if err := route.WriteHeaderIncludedPacket(stack.PacketBuffer{
+			if err := route.WriteHeaderIncludedPacket(&stack.PacketBuffer{
 				Data: buffer.View(payloadBytes).ToVectorisedView(),
 			}); err != nil {
 				return 0, nil, err
@@ -357,7 +357,7 @@ func (e *endpoint) finishWrite(payloadBytes []byte, route *stack.Route) (int64,
 		}
 
 		hdr := buffer.NewPrependable(len(payloadBytes) + int(route.MaxHeaderLength()))
-		if err := route.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: e.TransProto, TTL: route.DefaultTTL(), TOS: stack.DefaultTOS}, stack.PacketBuffer{
+		if err := route.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: e.TransProto, TTL: route.DefaultTTL(), TOS: stack.DefaultTOS}, &stack.PacketBuffer{
 			Header: hdr,
 			Data:   buffer.View(payloadBytes).ToVectorisedView(),
 			Owner:  e.owner,
@@ -584,7 +584,7 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 }
 
 // HandlePacket implements stack.RawTransportEndpoint.HandlePacket.
-func (e *endpoint) HandlePacket(route *stack.Route, pkt stack.PacketBuffer) {
+func (e *endpoint) HandlePacket(route *stack.Route, pkt *stack.PacketBuffer) {
 	e.rcvMu.Lock()
 
 	// Drop the packet if our buffer is currently full.
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index e4a06c9e1..7da93dcc4 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -833,13 +833,13 @@ func sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stac
 		return sendTCPBatch(r, tf, data, gso, owner)
 	}
 
-	pkt := stack.PacketBuffer{
+	pkt := &stack.PacketBuffer{
 		Header: buffer.NewPrependable(header.TCPMinimumSize + int(r.MaxHeaderLength()) + optLen),
 		Data:   data,
 		Hash:   tf.txHash,
 		Owner:  owner,
 	}
-	buildTCPHdr(r, tf, &pkt, gso)
+	buildTCPHdr(r, tf, pkt, gso)
 
 	if tf.ttl == 0 {
 		tf.ttl = r.DefaultTTL()
diff --git a/pkg/tcpip/transport/tcp/dispatcher.go b/pkg/tcpip/transport/tcp/dispatcher.go
index 6062ca916..047704c80 100644
--- a/pkg/tcpip/transport/tcp/dispatcher.go
+++ b/pkg/tcpip/transport/tcp/dispatcher.go
@@ -186,7 +186,7 @@ func (d *dispatcher) wait() {
 	}
 }
 
-func (d *dispatcher) queuePacket(r *stack.Route, stackEP stack.TransportEndpoint, id stack.TransportEndpointID, pkt stack.PacketBuffer) {
+func (d *dispatcher) queuePacket(r *stack.Route, stackEP stack.TransportEndpoint, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {
 	ep := stackEP.(*endpoint)
 	s := newSegment(r, id, pkt)
 	if !s.parse() {
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index b5ba972f1..d048ef90c 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -2462,7 +2462,7 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
 	}, nil
 }
 
-func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) {
+func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {
 	// TCP HandlePacket is not required anymore as inbound packets first
 	// land at the Dispatcher which then can either delivery using the
 	// worker go routine or directly do the invoke the tcp processing inline
@@ -2481,7 +2481,7 @@ func (e *endpoint) enqueueSegment(s *segment) bool {
 }
 
 // HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket.
-func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, pkt stack.PacketBuffer) {
+func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, pkt *stack.PacketBuffer) {
 	switch typ {
 	case stack.ControlPacketTooBig:
 		e.sndBufMu.Lock()
diff --git a/pkg/tcpip/transport/tcp/forwarder.go b/pkg/tcpip/transport/tcp/forwarder.go
index 704d01c64..070b634b4 100644
--- a/pkg/tcpip/transport/tcp/forwarder.go
+++ b/pkg/tcpip/transport/tcp/forwarder.go
@@ -61,7 +61,7 @@ func NewForwarder(s *stack.Stack, rcvWnd, maxInFlight int, handler func(*Forward
 //
 // This function is expected to be passed as an argument to the
 // stack.SetTransportProtocolHandler function.
-func (f *Forwarder) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) bool {
+func (f *Forwarder) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) bool {
 	s := newSegment(r, id, pkt)
 	defer s.decRef()
 
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index 2a2a7ddeb..c827d0277 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -206,7 +206,7 @@ func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
 // to a specific processing queue. Each queue is serviced by its own processor
 // goroutine which is responsible for dequeuing and doing full TCP dispatch of
 // the packet.
-func (p *protocol) QueuePacket(r *stack.Route, ep stack.TransportEndpoint, id stack.TransportEndpointID, pkt stack.PacketBuffer) {
+func (p *protocol) QueuePacket(r *stack.Route, ep stack.TransportEndpoint, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {
 	p.dispatcher.queuePacket(r, ep, id, pkt)
 }
 
@@ -217,7 +217,7 @@ func (p *protocol) QueuePacket(r *stack.Route, ep stack.TransportEndpoint, id st
 // a reset is sent in response to any incoming segment except another reset. In
 // particular, SYNs addressed to a non-existent connection are rejected by this
 // means."
-func (*protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) bool {
+func (*protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) bool {
 	s := newSegment(r, id, pkt)
 	defer s.decRef()
 
diff --git a/pkg/tcpip/transport/tcp/segment.go b/pkg/tcpip/transport/tcp/segment.go
index 074edded6..0c099e2fd 100644
--- a/pkg/tcpip/transport/tcp/segment.go
+++ b/pkg/tcpip/transport/tcp/segment.go
@@ -60,7 +60,7 @@ type segment struct {
 	xmitCount uint32
 }
 
-func newSegment(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) *segment {
+func newSegment(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) *segment {
 	s := &segment{
 		refCnt: 1,
 		id:     id,
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index 7b1d72cf4..9721f6caf 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -316,7 +316,7 @@ func (c *Context) SendICMPPacket(typ header.ICMPv4Type, code uint8, p1, p2 []byt
 	copy(icmp[header.ICMPv4PayloadOffset:], p2)
 
 	// Inject packet.
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
 		Data: buf.ToVectorisedView(),
 	})
 }
@@ -372,7 +372,7 @@ func (c *Context) BuildSegmentWithAddrs(payload []byte, h *Headers, src, dst tcp
 // SendSegment sends a TCP segment that has already been built and written to a
 // buffer.VectorisedView.
 func (c *Context) SendSegment(s buffer.VectorisedView) {
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
 		Data: s,
 	})
 }
@@ -380,7 +380,7 @@ func (c *Context) SendSegment(s buffer.VectorisedView) {
 // SendPacket builds and sends a TCP segment(with the provided payload & TCP
 // headers) in an IPv4 packet via the link layer endpoint.
 func (c *Context) SendPacket(payload []byte, h *Headers) {
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
 		Data: c.BuildSegment(payload, h),
 	})
 }
@@ -389,7 +389,7 @@ func (c *Context) SendPacket(payload []byte, h *Headers) {
 // & TCPheaders) in an IPv4 packet via the link layer endpoint using the
 // provided source and destination IPv4 addresses.
 func (c *Context) SendPacketWithAddrs(payload []byte, h *Headers, src, dst tcpip.Address) {
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
 		Data: c.BuildSegmentWithAddrs(payload, h, src, dst),
 	})
 }
@@ -564,7 +564,7 @@ func (c *Context) SendV6PacketWithAddrs(payload []byte, h *Headers, src, dst tcp
 	t.SetChecksum(^t.CalculateChecksum(xsum))
 
 	// Inject packet.
-	c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
 		Data: buf.ToVectorisedView(),
 	})
 }
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 647b2067a..79faa7869 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -921,7 +921,11 @@ func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort u
 	if useDefaultTTL {
 		ttl = r.DefaultTTL()
 	}
-	if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: ProtocolNumber, TTL: ttl, TOS: tos}, stack.PacketBuffer{
+	if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
+		Protocol: ProtocolNumber,
+		TTL:      ttl,
+		TOS:      tos,
+	}, &stack.PacketBuffer{
 		Header:          hdr,
 		Data:            data,
 		TransportHeader: buffer.View(udp),
@@ -1269,7 +1273,7 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 
 // HandlePacket is called by the stack when new packets arrive to this transport
 // endpoint.
-func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) {
+func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {
 	// Get the header then trim it from the view.
 	hdr, ok := pkt.Data.PullUp(header.UDPMinimumSize)
 	if !ok || int(header.UDP(hdr).Length()) > pkt.Data.Size() {
@@ -1336,7 +1340,7 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
 }
 
 // HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket.
-func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, pkt stack.PacketBuffer) {
+func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, pkt *stack.PacketBuffer) {
 	if typ == stack.ControlPortUnreachable {
 		e.mu.RLock()
 		defer e.mu.RUnlock()
diff --git a/pkg/tcpip/transport/udp/forwarder.go b/pkg/tcpip/transport/udp/forwarder.go
index a674ceb68..7abfa0ed2 100644
--- a/pkg/tcpip/transport/udp/forwarder.go
+++ b/pkg/tcpip/transport/udp/forwarder.go
@@ -43,7 +43,7 @@ func NewForwarder(s *stack.Stack, handler func(*ForwarderRequest)) *Forwarder {
 //
 // This function is expected to be passed as an argument to the
 // stack.SetTransportProtocolHandler function.
-func (f *Forwarder) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) bool {
+func (f *Forwarder) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) bool {
 	f.handler(&ForwarderRequest{
 		stack: f.stack,
 		route: r,
@@ -61,7 +61,7 @@ type ForwarderRequest struct {
 	stack *stack.Stack
 	route *stack.Route
 	id    stack.TransportEndpointID
-	pkt   stack.PacketBuffer
+	pkt   *stack.PacketBuffer
 }
 
 // ID returns the 4-tuple (src address, src port, dst address, dst port) that
diff --git a/pkg/tcpip/transport/udp/protocol.go b/pkg/tcpip/transport/udp/protocol.go
index 52af6de22..e320c5758 100644
--- a/pkg/tcpip/transport/udp/protocol.go
+++ b/pkg/tcpip/transport/udp/protocol.go
@@ -66,7 +66,7 @@ func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
 
 // HandleUnknownDestinationPacket handles packets targeted at this protocol but
 // that don't match any existing endpoint.
-func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) bool {
+func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) bool {
 	// Get the header then trim it from the view.
 	h, ok := pkt.Data.PullUp(header.UDPMinimumSize)
 	if !ok {
@@ -140,7 +140,7 @@ func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.Trans
 		pkt.SetType(header.ICMPv4DstUnreachable)
 		pkt.SetCode(header.ICMPv4PortUnreachable)
 		pkt.SetChecksum(header.ICMPv4Checksum(pkt, payload))
-		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, stack.PacketBuffer{
+		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, &stack.PacketBuffer{
 			Header: hdr,
 			Data:   payload,
 		})
@@ -177,7 +177,7 @@ func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.Trans
 		pkt.SetType(header.ICMPv6DstUnreachable)
 		pkt.SetCode(header.ICMPv6PortUnreachable)
 		pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, payload))
-		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, stack.PacketBuffer{
+		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, &stack.PacketBuffer{
 			Header: hdr,
 			Data:   payload,
 		})
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index 8acaa607a..e8ade882b 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -440,7 +440,7 @@ func (c *testContext) injectV6Packet(payload []byte, h *header4Tuple, valid bool
 	u.SetChecksum(^u.CalculateChecksum(xsum))
 
 	// Inject packet.
-	c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
 		Data:            buf.ToVectorisedView(),
 		NetworkHeader:   buffer.View(ip),
 		TransportHeader: buffer.View(u),
@@ -487,7 +487,7 @@ func (c *testContext) injectV4Packet(payload []byte, h *header4Tuple, valid bool
 
 	// Inject packet.
 
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
 		Data:            buf.ToVectorisedView(),
 		NetworkHeader:   buffer.View(ip),
 		TransportHeader: buffer.View(u),