Make `stack.Route` thread safe

Currently we rely on the user to take the lock on the endpoint that owns the
route, in order to modify it safely. We can instead move
`Route.RemoteLinkAddress` under `Route`'s mutex, and allow non-locking and
thread-safe access to other fields of `Route`.

PiperOrigin-RevId: 345461586

8 files changed, 27 insertions, 33 deletions

diff --git a/pkg/tcpip/link/ethernet/ethernet.go b/pkg/tcpip/link/ethernet/ethernet.go
index 3eef7cd56..beefcd008 100644
--- a/pkg/tcpip/link/ethernet/ethernet.go
+++ b/pkg/tcpip/link/ethernet/ethernet.go
@@ -62,7 +62,7 @@ func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
 
 // WritePacket implements stack.LinkEndpoint.
 func (e *Endpoint) WritePacket(r *stack.Route, gso *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
-	e.AddHeader(e.Endpoint.LinkAddress(), r.RemoteLinkAddress, proto, pkt)
+	e.AddHeader(e.Endpoint.LinkAddress(), r.RemoteLinkAddress(), proto, pkt)
 	return e.Endpoint.WritePacket(r, gso, proto, pkt)
 }
 
@@ -71,7 +71,7 @@ func (e *Endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	linkAddr := e.Endpoint.LinkAddress()
 
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-		e.AddHeader(linkAddr, r.RemoteLinkAddress, proto, pkt)
+		e.AddHeader(linkAddr, r.RemoteLinkAddress(), proto, pkt)
 	}
 
 	return e.Endpoint.WritePackets(r, gso, pkts, proto)
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index fc620c7d5..9f2084eae 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -410,7 +410,7 @@ func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.Net
 // currently writable, the packet is dropped.
 func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
 	if e.hdrSize > 0 {
-		e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
+		e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress(), protocol, pkt)
 	}
 
 	var builder iovec.Builder
@@ -453,7 +453,7 @@ func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, *tc
 	mmsgHdrs := make([]rawfile.MMsgHdr, 0, len(batch))
 	for _, pkt := range batch {
 		if e.hdrSize > 0 {
-			e.AddHeader(pkt.EgressRoute.LocalLinkAddress, pkt.EgressRoute.RemoteLinkAddress, pkt.NetworkProtocolNumber, pkt)
+			e.AddHeader(pkt.EgressRoute.LocalLinkAddress, pkt.EgressRoute.RemoteLinkAddress(), pkt.NetworkProtocolNumber, pkt)
 		}
 
 		var vnetHdrBuf []byte
diff --git a/pkg/tcpip/link/fdbased/endpoint_test.go b/pkg/tcpip/link/fdbased/endpoint_test.go
index 709f829c8..ce4da7230 100644
--- a/pkg/tcpip/link/fdbased/endpoint_test.go
+++ b/pkg/tcpip/link/fdbased/endpoint_test.go
@@ -183,9 +183,8 @@ func testWritePacket(t *testing.T, plen int, eth bool, gsoMaxSize uint32, hash u
 	c := newContext(t, &Options{Address: laddr, MTU: mtu, EthernetHeader: eth, GSOMaxSize: gsoMaxSize})
 	defer c.cleanup()
 
-	r := &stack.Route{
-		RemoteLinkAddress: raddr,
-	}
+	var r stack.Route
+	r.ResolveWith(raddr)
 
 	// Build payload.
 	payload := buffer.NewView(plen)
@@ -220,7 +219,7 @@ func testWritePacket(t *testing.T, plen int, eth bool, gsoMaxSize uint32, hash u
 			L3HdrLen:   header.IPv4MaximumHeaderSize,
 		}
 	}
-	if err := c.ep.WritePacket(r, gso, proto, pkt); err != nil {
+	if err := c.ep.WritePacket(&r, gso, proto, pkt); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 
@@ -325,9 +324,9 @@ func TestPreserveSrcAddress(t *testing.T) {
 
 	// Set LocalLinkAddress in route to the value of the bridged address.
 	r := &stack.Route{
-		RemoteLinkAddress: raddr,
-		LocalLinkAddress:  baddr,
+		LocalLinkAddress: baddr,
 	}
+	r.ResolveWith(raddr)
 
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 		// WritePacket panics given a prependable with anything less than
diff --git a/pkg/tcpip/link/packetsocket/endpoint.go b/pkg/tcpip/link/packetsocket/endpoint.go
index 3922c2a04..9a1b0c0c2 100644
--- a/pkg/tcpip/link/packetsocket/endpoint.go
+++ b/pkg/tcpip/link/packetsocket/endpoint.go
@@ -36,14 +36,14 @@ func New(lower stack.LinkEndpoint) stack.LinkEndpoint {
 
 // WritePacket implements stack.LinkEndpoint.WritePacket.
 func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
-	e.Endpoint.DeliverOutboundPacket(r.RemoteLinkAddress, r.LocalLinkAddress, protocol, pkt)
+	e.Endpoint.DeliverOutboundPacket(r.RemoteLinkAddress(), r.LocalLinkAddress, protocol, pkt)
 	return e.Endpoint.WritePacket(r, gso, protocol, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
 func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-		e.Endpoint.DeliverOutboundPacket(pkt.EgressRoute.RemoteLinkAddress, pkt.EgressRoute.LocalLinkAddress, pkt.NetworkProtocolNumber, pkt)
+		e.Endpoint.DeliverOutboundPacket(pkt.EgressRoute.RemoteLinkAddress(), pkt.EgressRoute.LocalLinkAddress, pkt.NetworkProtocolNumber, pkt)
 	}
 
 	return e.Endpoint.WritePackets(r, gso, pkts, proto)
diff --git a/pkg/tcpip/link/pipe/pipe.go b/pkg/tcpip/link/pipe/pipe.go
index 71fcb73e1..25c364391 100644
--- a/pkg/tcpip/link/pipe/pipe.go
+++ b/pkg/tcpip/link/pipe/pipe.go
@@ -55,7 +55,7 @@ func (e *Endpoint) WritePacket(r *stack.Route, _ *stack.GSO, proto tcpip.Network
 	// remote address from the perspective of the other end of the pipe
 	// (e.linked). Similarly, the remote address from the perspective of this
 	// endpoint is the local address on the other end.
-	e.linked.dispatcher.DeliverNetworkPacket(r.LocalLinkAddress /* remote */, r.RemoteLinkAddress /* local */, proto, stack.NewPacketBuffer(stack.PacketBufferOptions{
+	e.linked.dispatcher.DeliverNetworkPacket(r.LocalLinkAddress /* remote */, r.RemoteLinkAddress() /* local */, proto, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buffer.NewVectorisedView(pkt.Size(), pkt.Views()),
 	}))
 
diff --git a/pkg/tcpip/link/sharedmem/sharedmem.go b/pkg/tcpip/link/sharedmem/sharedmem.go
index a1e7018c8..5660418fa 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem.go
@@ -204,7 +204,7 @@ func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.Net
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
 func (e *endpoint) WritePacket(r *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
-	e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
+	e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress(), protocol, pkt)
 
 	views := pkt.Views()
 	// Transmit the packet.
diff --git a/pkg/tcpip/link/sharedmem/sharedmem_test.go b/pkg/tcpip/link/sharedmem/sharedmem_test.go
index 22d5c97f1..7131392cc 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem_test.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem_test.go
@@ -260,9 +260,8 @@ func TestSimpleSend(t *testing.T) {
 	defer c.cleanup()
 
 	// Prepare route.
-	r := stack.Route{
-		RemoteLinkAddress: remoteLinkAddr,
-	}
+	var r stack.Route
+	r.ResolveWith(remoteLinkAddr)
 
 	for iters := 1000; iters > 0; iters-- {
 		func() {
@@ -342,9 +341,9 @@ func TestPreserveSrcAddressInSend(t *testing.T) {
 	newLocalLinkAddress := tcpip.LinkAddress(strings.Repeat("0xFE", 6))
 	// Set both remote and local link address in route.
 	r := stack.Route{
-		RemoteLinkAddress: remoteLinkAddr,
-		LocalLinkAddress:  newLocalLinkAddress,
+		LocalLinkAddress: newLocalLinkAddress,
 	}
+	r.ResolveWith(remoteLinkAddr)
 
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 		// WritePacket panics given a prependable with anything less than
@@ -395,9 +394,8 @@ func TestFillTxQueue(t *testing.T) {
 	defer c.cleanup()
 
 	// Prepare to send a packet.
-	r := stack.Route{
-		RemoteLinkAddress: remoteLinkAddr,
-	}
+	var r stack.Route
+	r.ResolveWith(remoteLinkAddr)
 
 	buf := buffer.NewView(100)
 
@@ -444,9 +442,8 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 	c.txq.rx.Flush()
 
 	// Prepare to send a packet.
-	r := stack.Route{
-		RemoteLinkAddress: remoteLinkAddr,
-	}
+	var r stack.Route
+	r.ResolveWith(remoteLinkAddr)
 
 	buf := buffer.NewView(100)
 
@@ -509,9 +506,8 @@ func TestFillTxMemory(t *testing.T) {
 	defer c.cleanup()
 
 	// Prepare to send a packet.
-	r := stack.Route{
-		RemoteLinkAddress: remoteLinkAddr,
-	}
+	var r stack.Route
+	r.ResolveWith(remoteLinkAddr)
 
 	buf := buffer.NewView(100)
 
@@ -557,9 +553,8 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 	defer c.cleanup()
 
 	// Prepare to send a packet.
-	r := stack.Route{
-		RemoteLinkAddress: remoteLinkAddr,
-	}
+	var r stack.Route
+	r.ResolveWith(remoteLinkAddr)
 
 	buf := buffer.NewView(100)
 
diff --git a/pkg/tcpip/link/tun/device.go b/pkg/tcpip/link/tun/device.go
index 9a76bdba7..a364c5801 100644
--- a/pkg/tcpip/link/tun/device.go
+++ b/pkg/tcpip/link/tun/device.go
@@ -264,7 +264,7 @@ func (d *Device) encodePkt(info *channel.PacketInfo) (buffer.View, bool) {
 	// If the packet does not already have link layer header, and the route
 	// does not exist, we can't compute it. This is possibly a raw packet, tun
 	// device doesn't support this at the moment.
-	if info.Pkt.LinkHeader().View().IsEmpty() && info.Route.RemoteLinkAddress == "" {
+	if info.Pkt.LinkHeader().View().IsEmpty() && info.Route.RemoteLinkAddress() == "" {
 		return nil, false
 	}
 
@@ -272,7 +272,7 @@ func (d *Device) encodePkt(info *channel.PacketInfo) (buffer.View, bool) {
 	if d.hasFlags(linux.IFF_TAP) {
 		// Add ethernet header if not provided.
 		if info.Pkt.LinkHeader().View().IsEmpty() {
-			d.endpoint.AddHeader(info.Route.LocalLinkAddress, info.Route.RemoteLinkAddress, info.Proto, info.Pkt)
+			d.endpoint.AddHeader(info.Route.LocalLinkAddress, info.Route.RemoteLinkAddress(), info.Proto, info.Pkt)
 		}
 		vv.AppendView(info.Pkt.LinkHeader().View())
 	}