1 files changed, 32 insertions, 20 deletions

diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index 4e20cfbf8..152d8f0b2 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -55,10 +55,15 @@ type endpoint struct {
 	// its end of the communication pipe.
 	closed func(*tcpip.Error)
 
-	vv       *buffer.VectorisedView
-	iovecs   []syscall.Iovec
-	views    []buffer.View
-	attached bool
+	vv         *buffer.VectorisedView
+	iovecs     []syscall.Iovec
+	views      []buffer.View
+	dispatcher stack.NetworkDispatcher
+
+	// handleLocal indicates whether packets destined to itself should be
+	// handled by the netstack internally (true) or be forwarded to the FD
+	// endpoint (false).
+	handleLocal bool
 }
 
 // Options specify the details about the fd-based endpoint to be created.
@@ -71,6 +76,7 @@ type Options struct {
 	Address         tcpip.LinkAddress
 	SaveRestore     bool
 	DisconnectOk    bool
+	HandleLocal     bool
 }
 
 // New creates a new fd-based endpoint.
@@ -100,14 +106,15 @@ func New(opts *Options) tcpip.LinkEndpointID {
 	}
 
 	e := &endpoint{
-		fd:      opts.FD,
-		mtu:     opts.MTU,
-		caps:    caps,
-		closed:  opts.ClosedFunc,
-		addr:    opts.Address,
-		hdrSize: hdrSize,
-		views:   make([]buffer.View, len(BufConfig)),
-		iovecs:  make([]syscall.Iovec, len(BufConfig)),
+		fd:          opts.FD,
+		mtu:         opts.MTU,
+		caps:        caps,
+		closed:      opts.ClosedFunc,
+		addr:        opts.Address,
+		hdrSize:     hdrSize,
+		views:       make([]buffer.View, len(BufConfig)),
+		iovecs:      make([]syscall.Iovec, len(BufConfig)),
+		handleLocal: opts.HandleLocal,
 	}
 	vv := buffer.NewVectorisedView(0, e.views)
 	e.vv = &vv
@@ -117,16 +124,16 @@ func New(opts *Options) tcpip.LinkEndpointID {
 // Attach launches the goroutine that reads packets from the file descriptor and
 // dispatches them via the provided dispatcher.
 func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
-	e.attached = true
+	e.dispatcher = dispatcher
 	// Link endpoints are not savable. When transportation endpoints are
 	// saved, they stop sending outgoing packets and all incoming packets
 	// are rejected.
-	go e.dispatchLoop(dispatcher) // S/R-SAFE: See above.
+	go e.dispatchLoop() // S/R-SAFE: See above.
 }
 
 // IsAttached implements stack.LinkEndpoint.IsAttached.
 func (e *endpoint) IsAttached() bool {
-	return e.attached
+	return e.dispatcher != nil
 }
 
 // MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
@@ -153,6 +160,12 @@ func (e *endpoint) LinkAddress() tcpip.LinkAddress {
 // 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, hdr *buffer.Prependable, payload buffer.View, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+	if e.handleLocal && r.LocalAddress != "" && r.LocalAddress == r.RemoteAddress {
+		hdrView := hdr.View()
+		vv := buffer.NewVectorisedView(len(hdrView)+len(payload), []buffer.View{hdrView, payload})
+		e.dispatcher.DeliverNetworkPacket(e, r.RemoteLinkAddress, protocol, &vv)
+		return nil
+	}
 	if e.hdrSize > 0 {
 		// Add ethernet header if needed.
 		eth := header.Ethernet(hdr.Prepend(header.EthernetMinimumSize))
@@ -165,7 +178,6 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr *buffer.Prependable, payload
 
 	if len(payload) == 0 {
 		return rawfile.NonBlockingWrite(e.fd, hdr.UsedBytes())
-
 	}
 
 	return rawfile.NonBlockingWrite2(e.fd, hdr.UsedBytes(), payload)
@@ -198,7 +210,7 @@ func (e *endpoint) allocateViews(bufConfig []int) {
 }
 
 // dispatch reads one packet from the file descriptor and dispatches it.
-func (e *endpoint) dispatch(d stack.NetworkDispatcher, largeV buffer.View) (bool, *tcpip.Error) {
+func (e *endpoint) dispatch(largeV buffer.View) (bool, *tcpip.Error) {
 	e.allocateViews(BufConfig)
 
 	n, err := rawfile.BlockingReadv(e.fd, e.iovecs)
@@ -234,7 +246,7 @@ func (e *endpoint) dispatch(d stack.NetworkDispatcher, largeV buffer.View) (bool
 	e.vv.SetSize(n)
 	e.vv.TrimFront(e.hdrSize)
 
-	d.DeliverNetworkPacket(e, addr, p, e.vv)
+	e.dispatcher.DeliverNetworkPacket(e, addr, p, e.vv)
 
 	// Prepare e.views for another packet: release used views.
 	for i := 0; i < used; i++ {
@@ -246,10 +258,10 @@ func (e *endpoint) dispatch(d stack.NetworkDispatcher, largeV buffer.View) (bool
 
 // dispatchLoop reads packets from the file descriptor in a loop and dispatches
 // them to the network stack.
-func (e *endpoint) dispatchLoop(d stack.NetworkDispatcher) *tcpip.Error {
+func (e *endpoint) dispatchLoop() *tcpip.Error {
 	v := buffer.NewView(header.MaxIPPacketSize)
 	for {
-		cont, err := e.dispatch(d, v)
+		cont, err := e.dispatch(v)
 		if err != nil || !cont {
 			if e.closed != nil {
 				e.closed(err)