Introduce stack.WritePacketToRemote, remove LinkEndpoint.WriteRawPacket

Redefine stack.WritePacket into stack.WritePacketToRemote which lets the NIC
decide whether to append link headers.

PiperOrigin-RevId: 343071742

22 files changed, 68 insertions, 186 deletions

diff --git a/pkg/tcpip/link/channel/BUILD b/pkg/tcpip/link/channel/BUILD
index 39ca774ef..973f06cbc 100644
--- a/pkg/tcpip/link/channel/BUILD
+++ b/pkg/tcpip/link/channel/BUILD
@@ -9,7 +9,6 @@ go_library(
     deps = [
         "//pkg/sync",
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
     ],
diff --git a/pkg/tcpip/link/channel/channel.go b/pkg/tcpip/link/channel/channel.go
index c95aef63c..a7f5f4979 100644
--- a/pkg/tcpip/link/channel/channel.go
+++ b/pkg/tcpip/link/channel/channel.go
@@ -22,7 +22,6 @@ import (
 
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -271,21 +270,6 @@ func (e *Endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	return n, nil
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *Endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	p := PacketInfo{
-		Pkt: stack.NewPacketBuffer(stack.PacketBufferOptions{
-			Data: vv,
-		}),
-		Proto: 0,
-		GSO:   nil,
-	}
-
-	e.q.Write(p)
-
-	return nil
-}
-
 // Wait implements stack.LinkEndpoint.Wait.
 func (*Endpoint) Wait() {}
 
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index 975309fc8..fc620c7d5 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -558,11 +558,6 @@ func viewsEqual(vs1, vs2 []buffer.View) bool {
 	return len(vs1) == len(vs2) && (len(vs1) == 0 || &vs1[0] == &vs2[0])
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	return rawfile.NonBlockingWrite(e.fds[0], vv.ToView())
-}
-
 // InjectOutobund implements stack.InjectableEndpoint.InjectOutbound.
 func (e *endpoint) InjectOutbound(dest tcpip.Address, packet []byte) *tcpip.Error {
 	return rawfile.NonBlockingWrite(e.fds[0], packet)
diff --git a/pkg/tcpip/link/loopback/loopback.go b/pkg/tcpip/link/loopback/loopback.go
index 38aa694e4..edca57e4e 100644
--- a/pkg/tcpip/link/loopback/loopback.go
+++ b/pkg/tcpip/link/loopback/loopback.go
@@ -96,23 +96,6 @@ func (e *endpoint) WritePackets(*stack.Route, *stack.GSO, stack.PacketBufferList
 	panic("not implemented")
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
-		Data: vv,
-	})
-	// There should be an ethernet header at the beginning of vv.
-	hdr, ok := pkt.LinkHeader().Consume(header.EthernetMinimumSize)
-	if !ok {
-		// Reject the packet if it's shorter than an ethernet header.
-		return tcpip.ErrBadAddress
-	}
-	linkHeader := header.Ethernet(hdr)
-	e.dispatcher.DeliverNetworkPacket("" /* remote */, "" /* local */, linkHeader.Type(), pkt)
-
-	return nil
-}
-
 // ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType.
 func (*endpoint) ARPHardwareType() header.ARPHardwareType {
 	return header.ARPHardwareLoopback
diff --git a/pkg/tcpip/link/muxed/BUILD b/pkg/tcpip/link/muxed/BUILD
index e7493e5c5..cbda59775 100644
--- a/pkg/tcpip/link/muxed/BUILD
+++ b/pkg/tcpip/link/muxed/BUILD
@@ -8,7 +8,6 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
     ],
diff --git a/pkg/tcpip/link/muxed/injectable.go b/pkg/tcpip/link/muxed/injectable.go
index 56a611825..22e79ce3a 100644
--- a/pkg/tcpip/link/muxed/injectable.go
+++ b/pkg/tcpip/link/muxed/injectable.go
@@ -17,7 +17,6 @@ package muxed
 
 import (
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -106,13 +105,6 @@ func (m *InjectableEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, protoco
 	return tcpip.ErrNoRoute
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (m *InjectableEndpoint) WriteRawPacket(buffer.VectorisedView) *tcpip.Error {
-	// WriteRawPacket doesn't get a route or network address, so there's
-	// nowhere to write this.
-	return tcpip.ErrNoRoute
-}
-
 // InjectOutbound writes outbound packets to the appropriate
 // LinkInjectableEndpoint based on the dest address.
 func (m *InjectableEndpoint) InjectOutbound(dest tcpip.Address, packet []byte) *tcpip.Error {
diff --git a/pkg/tcpip/link/nested/BUILD b/pkg/tcpip/link/nested/BUILD
index 2cdb23475..00b42b924 100644
--- a/pkg/tcpip/link/nested/BUILD
+++ b/pkg/tcpip/link/nested/BUILD
@@ -11,7 +11,6 @@ go_library(
     deps = [
         "//pkg/sync",
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
     ],
diff --git a/pkg/tcpip/link/nested/nested.go b/pkg/tcpip/link/nested/nested.go
index d40de54df..0ee54c3d5 100644
--- a/pkg/tcpip/link/nested/nested.go
+++ b/pkg/tcpip/link/nested/nested.go
@@ -19,7 +19,6 @@ package nested
 import (
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -123,11 +122,6 @@ func (e *Endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	return e.child.WritePackets(r, gso, pkts, protocol)
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.
-func (e *Endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	return e.child.WriteRawPacket(vv)
-}
-
 // Wait implements stack.LinkEndpoint.
 func (e *Endpoint) Wait() {
 	e.child.Wait()
diff --git a/pkg/tcpip/link/pipe/pipe.go b/pkg/tcpip/link/pipe/pipe.go
index 523b0d24b..71fcb73e1 100644
--- a/pkg/tcpip/link/pipe/pipe.go
+++ b/pkg/tcpip/link/pipe/pipe.go
@@ -67,11 +67,6 @@ func (*Endpoint) WritePackets(*stack.Route, *stack.GSO, stack.PacketBufferList,
 	panic("not implemented")
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.
-func (*Endpoint) WriteRawPacket(buffer.VectorisedView) *tcpip.Error {
-	panic("not implemented")
-}
-
 // Attach implements stack.LinkEndpoint.
 func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.dispatcher = dispatcher
diff --git a/pkg/tcpip/link/qdisc/fifo/BUILD b/pkg/tcpip/link/qdisc/fifo/BUILD
index 1d0079bd6..5bea598eb 100644
--- a/pkg/tcpip/link/qdisc/fifo/BUILD
+++ b/pkg/tcpip/link/qdisc/fifo/BUILD
@@ -13,7 +13,6 @@ go_library(
         "//pkg/sleep",
         "//pkg/sync",
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
     ],
diff --git a/pkg/tcpip/link/qdisc/fifo/endpoint.go b/pkg/tcpip/link/qdisc/fifo/endpoint.go
index fc1e34fc7..9b41d60d5 100644
--- a/pkg/tcpip/link/qdisc/fifo/endpoint.go
+++ b/pkg/tcpip/link/qdisc/fifo/endpoint.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sleep"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -197,13 +196,6 @@ func (e *endpoint) WritePackets(_ *stack.Route, _ *stack.GSO, pkts stack.PacketB
 	return enqueued, nil
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	// TODO(gvisor.dev/issue/3267): Queue these packets as well once
-	// WriteRawPacket takes PacketBuffer instead of VectorisedView.
-	return e.lower.WriteRawPacket(vv)
-}
-
 // Wait implements stack.LinkEndpoint.Wait.
 func (e *endpoint) Wait() {
 	e.lower.Wait()
diff --git a/pkg/tcpip/link/sharedmem/sharedmem.go b/pkg/tcpip/link/sharedmem/sharedmem.go
index 7fb8a6c49..a1e7018c8 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem.go
@@ -224,21 +224,6 @@ func (e *endpoint) WritePackets(r *stack.Route, _ *stack.GSO, pkts stack.PacketB
 	panic("not implemented")
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	views := vv.Views()
-	// Transmit the packet.
-	e.mu.Lock()
-	ok := e.tx.transmit(views...)
-	e.mu.Unlock()
-
-	if !ok {
-		return tcpip.ErrWouldBlock
-	}
-
-	return nil
-}
-
 // dispatchLoop reads packets from the rx queue in a loop and dispatches them
 // to the network stack.
 func (e *endpoint) dispatchLoop(d stack.NetworkDispatcher) {
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index 178e658df..8d9a91020 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -202,14 +202,6 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	return e.Endpoint.WritePackets(r, gso, pkts, protocol)
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	e.dumpPacket(directionSend, nil, 0, stack.NewPacketBuffer(stack.PacketBufferOptions{
-		Data: vv,
-	}))
-	return e.Endpoint.WriteRawPacket(vv)
-}
-
 func logPacket(prefix string, dir direction, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer, gso *stack.GSO) {
 	// Figure out the network layer info.
 	var transProto uint8
diff --git a/pkg/tcpip/link/waitable/BUILD b/pkg/tcpip/link/waitable/BUILD
index ee84c3d96..9b4602c1b 100644
--- a/pkg/tcpip/link/waitable/BUILD
+++ b/pkg/tcpip/link/waitable/BUILD
@@ -11,7 +11,6 @@ go_library(
     deps = [
         "//pkg/gate",
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
     ],
@@ -25,7 +24,6 @@ go_test(
     library = ":waitable",
     deps = [
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
     ],
diff --git a/pkg/tcpip/link/waitable/waitable.go b/pkg/tcpip/link/waitable/waitable.go
index b152a0f26..cf0077f43 100644
--- a/pkg/tcpip/link/waitable/waitable.go
+++ b/pkg/tcpip/link/waitable/waitable.go
@@ -24,7 +24,6 @@ package waitable
 import (
 	"gvisor.dev/gvisor/pkg/gate"
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -132,17 +131,6 @@ func (e *Endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	return n, err
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *Endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	if !e.writeGate.Enter() {
-		return nil
-	}
-
-	err := e.lower.WriteRawPacket(vv)
-	e.writeGate.Leave()
-	return err
-}
-
 // WaitWrite prevents new calls to WritePacket from reaching the lower endpoint,
 // and waits for inflight ones to finish before returning.
 func (e *Endpoint) WaitWrite() {
diff --git a/pkg/tcpip/link/waitable/waitable_test.go b/pkg/tcpip/link/waitable/waitable_test.go
index 94827fc56..cf7fb5126 100644
--- a/pkg/tcpip/link/waitable/waitable_test.go
+++ b/pkg/tcpip/link/waitable/waitable_test.go
@@ -18,7 +18,6 @@ import (
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -81,11 +80,6 @@ func (e *countedEndpoint) WritePackets(r *stack.Route, _ *stack.GSO, pkts stack.
 	return pkts.Len(), nil
 }
 
-func (e *countedEndpoint) WriteRawPacket(buffer.VectorisedView) *tcpip.Error {
-	e.writeCount++
-	return nil
-}
-
 // ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType.
 func (*countedEndpoint) ARPHardwareType() header.ARPHardwareType {
 	panic("unimplemented")
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index d49c44846..787399e08 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -193,10 +193,6 @@ func (*testObject) WritePackets(_ *stack.Route, _ *stack.GSO, pkt stack.PacketBu
 	panic("not implemented")
 }
 
-func (*testObject) WriteRawPacket(_ buffer.VectorisedView) *tcpip.Error {
-	return tcpip.ErrNotSupported
-}
-
 // ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType.
 func (*testObject) ARPHardwareType() header.ARPHardwareType {
 	panic("not implemented")
diff --git a/pkg/tcpip/network/testutil/testutil.go b/pkg/tcpip/network/testutil/testutil.go
index 7cc52985e..5c3363759 100644
--- a/pkg/tcpip/network/testutil/testutil.go
+++ b/pkg/tcpip/network/testutil/testutil.go
@@ -85,21 +85,6 @@ func (ep *MockLinkEndpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts st
 	return n, nil
 }
 
-// WriteRawPacket implements LinkEndpoint.WriteRawPacket.
-func (ep *MockLinkEndpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	if ep.allowPackets == 0 {
-		return ep.err
-	}
-	ep.allowPackets--
-
-	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
-		Data: vv,
-	})
-	ep.WrittenPackets = append(ep.WrittenPackets, pkt)
-
-	return nil
-}
-
 // Attach implements LinkEndpoint.Attach.
 func (*MockLinkEndpoint) Attach(stack.NetworkDispatcher) {}
 
diff --git a/pkg/tcpip/stack/forwarding_test.go b/pkg/tcpip/stack/forwarding_test.go
index 6dc9e7859..cb7dec1ea 100644
--- a/pkg/tcpip/stack/forwarding_test.go
+++ b/pkg/tcpip/stack/forwarding_test.go
@@ -333,20 +333,6 @@ func (e *fwdTestLinkEndpoint) WritePackets(r *Route, gso *GSO, pkts PacketBuffer
 	return n, nil
 }
 
-// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *fwdTestLinkEndpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	p := fwdTestPacketInfo{
-		Pkt: NewPacketBuffer(PacketBufferOptions{Data: vv}),
-	}
-
-	select {
-	case e.C <- p:
-	default:
-	}
-
-	return nil
-}
-
 // Wait implements stack.LinkEndpoint.Wait.
 func (*fwdTestLinkEndpoint) Wait() {}
 
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index 2cb13c6fa..43ca03ada 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -739,10 +739,6 @@ type LinkEndpoint interface {
 	// endpoint.
 	Capabilities() LinkEndpointCapabilities
 
-	// WriteRawPacket writes a packet directly to the link. The packet
-	// should already have an ethernet header. It takes ownership of vv.
-	WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error
-
 	// Attach attaches the data link layer endpoint to the network-layer
 	// dispatcher of the stack.
 	//
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index e0025e0a9..f4504e633 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -1810,49 +1810,20 @@ func (s *Stack) unregisterPacketEndpointLocked(nicID tcpip.NICID, netProto tcpip
 	nic.unregisterPacketEndpoint(netProto, ep)
 }
 
-// WritePacket writes data directly to the specified NIC. It adds an ethernet
-// header based on the arguments.
-func (s *Stack) WritePacket(nicID tcpip.NICID, dst tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, payload buffer.VectorisedView) *tcpip.Error {
+// WritePacketToRemote writes a payload on the specified NIC using the provided
+// network protocol and remote link address.
+func (s *Stack) WritePacketToRemote(nicID tcpip.NICID, remote tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, payload buffer.VectorisedView) *tcpip.Error {
 	s.mu.Lock()
 	nic, ok := s.nics[nicID]
 	s.mu.Unlock()
 	if !ok {
 		return tcpip.ErrUnknownDevice
 	}
-
-	// Add our own fake ethernet header.
-	ethFields := header.EthernetFields{
-		SrcAddr: nic.LinkEndpoint.LinkAddress(),
-		DstAddr: dst,
-		Type:    netProto,
-	}
-	fakeHeader := make(header.Ethernet, header.EthernetMinimumSize)
-	fakeHeader.Encode(&ethFields)
-	vv := buffer.View(fakeHeader).ToVectorisedView()
-	vv.Append(payload)
-
-	if err := nic.LinkEndpoint.WriteRawPacket(vv); err != nil {
-		return err
-	}
-
-	return nil
-}
-
-// WriteRawPacket writes data directly to the specified NIC without adding any
-// headers.
-func (s *Stack) WriteRawPacket(nicID tcpip.NICID, payload buffer.VectorisedView) *tcpip.Error {
-	s.mu.Lock()
-	nic, ok := s.nics[nicID]
-	s.mu.Unlock()
-	if !ok {
-		return tcpip.ErrUnknownDevice
-	}
-
-	if err := nic.LinkEndpoint.WriteRawPacket(payload); err != nil {
-		return err
-	}
-
-	return nil
+	pkt := NewPacketBuffer(PacketBufferOptions{
+		ReserveHeaderBytes: int(nic.MaxHeaderLength()),
+		Data:               payload,
+	})
+	return nic.WritePacketToRemote(remote, nil, 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 61db3164b..0d94af139 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -4152,3 +4152,63 @@ func TestFindRouteWithForwarding(t *testing.T) {
 		})
 	}
 }
+
+func TestWritePacketToRemote(t *testing.T) {
+	const nicID = 1
+	const MTU = 1280
+	e := channel.New(1, MTU, linkAddr1)
+	s := stack.New(stack.Options{})
+	if err := s.CreateNIC(nicID, e); err != nil {
+		t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
+	}
+	if err := s.EnableNIC(nicID); err != nil {
+		t.Fatalf("CreateNIC(%d) = %s", nicID, err)
+	}
+	tests := []struct {
+		name     string
+		protocol tcpip.NetworkProtocolNumber
+		payload  []byte
+	}{
+		{
+			name:     "SuccessIPv4",
+			protocol: header.IPv4ProtocolNumber,
+			payload:  []byte{1, 2, 3, 4},
+		},
+		{
+			name:     "SuccessIPv6",
+			protocol: header.IPv6ProtocolNumber,
+			payload:  []byte{5, 6, 7, 8},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if err := s.WritePacketToRemote(nicID, linkAddr2, test.protocol, buffer.View(test.payload).ToVectorisedView()); err != nil {
+				t.Fatalf("s.WritePacketToRemote(_, _, _, _) = %s", err)
+			}
+
+			pkt, ok := e.Read()
+			if got, want := ok, true; got != want {
+				t.Fatalf("e.Read() = %t, want %t", got, want)
+			}
+			if got, want := pkt.Proto, test.protocol; got != want {
+				t.Fatalf("pkt.Proto = %d, want %d", got, want)
+			}
+			if got, want := pkt.Route.RemoteLinkAddress, linkAddr2; got != want {
+				t.Fatalf("pkt.Route.RemoteAddress = %s, want %s", got, want)
+			}
+			if diff := cmp.Diff(pkt.Pkt.Data.ToView(), buffer.View(test.payload)); diff != "" {
+				t.Errorf("pkt.Pkt.Data mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+
+	t.Run("InvalidNICID", func(t *testing.T) {
+		if got, want := s.WritePacketToRemote(234, linkAddr2, header.IPv4ProtocolNumber, buffer.View([]byte{1}).ToVectorisedView()), tcpip.ErrUnknownDevice; got != want {
+			t.Fatalf("s.WritePacketToRemote(_, _, _, _) = %s, want = %s", got, want)
+		}
+		pkt, ok := e.Read()
+		if got, want := ok, false; got != want {
+			t.Fatalf("e.Read() = %t, %v; want %t", got, pkt, want)
+		}
+	})
+}