10 files changed, 54 insertions, 3 deletions
diff --git a/pkg/tcpip/link/channel/channel.go b/pkg/tcpip/link/channel/channel.go
index eec430d0a..18adb2085 100644
--- a/pkg/tcpip/link/channel/channel.go
+++ b/pkg/tcpip/link/channel/channel.go
@@ -133,3 +133,6 @@ func (e *Endpoint) WritePacket(_ *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 
 	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 adcf21371..584db710e 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -41,6 +41,7 @@ package fdbased
 
 import (
 	"fmt"
+	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
@@ -81,6 +82,7 @@ const (
 	PacketMMap
 )
 
+// An endpoint implements the link-layer using a message-oriented file descriptor.
 type endpoint struct {
 	// fds is the set of file descriptors each identifying one inbound/outbound
 	// channel. The endpoint will dispatch from all inbound channels as well as
@@ -114,6 +116,9 @@ type endpoint struct {
 	// gsoMaxSize is the maximum GSO packet size. It is zero if GSO is
 	// disabled.
 	gsoMaxSize uint32
+
+	// wg keeps track of running goroutines.
+	wg sync.WaitGroup
 }
 
 // Options specify the details about the fd-based endpoint to be created.
@@ -164,7 +169,8 @@ type Options struct {
 // New creates a new fd-based endpoint.
 //
 // Makes fd non-blocking, but does not take ownership of fd, which must remain
-// open for the lifetime of the returned endpoint.
+// open for the lifetime of the returned endpoint (until after the endpoint has
+// stopped being using and Wait returns).
 func New(opts *Options) (stack.LinkEndpoint, error) {
 	caps := stack.LinkEndpointCapabilities(0)
 	if opts.RXChecksumOffload {
@@ -290,7 +296,11 @@ func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	// saved, they stop sending outgoing packets and all incoming packets
 	// are rejected.
 	for i := range e.inboundDispatchers {
-		go e.dispatchLoop(e.inboundDispatchers[i]) // S/R-SAFE: See above.
+		e.wg.Add(1)
+		go func(i int) { // S/R-SAFE: See above.
+			e.dispatchLoop(e.inboundDispatchers[i])
+			e.wg.Done()
+		}(i)
 	}
 }
 
@@ -320,6 +330,12 @@ func (e *endpoint) LinkAddress() tcpip.LinkAddress {
 	return e.addr
 }
 
+// Wait implements stack.LinkEndpoint.Wait. It waits for the endpoint to stop
+// reading from its FD.
+func (e *endpoint) Wait() {
+	e.wg.Wait()
+}
+
 // virtioNetHdr is declared in linux/virtio_net.h.
 type virtioNetHdr struct {
 	flags      uint8
diff --git a/pkg/tcpip/link/loopback/loopback.go b/pkg/tcpip/link/loopback/loopback.go
index e121ea1a5..b36629d2c 100644
--- a/pkg/tcpip/link/loopback/loopback.go
+++ b/pkg/tcpip/link/loopback/loopback.go
@@ -85,3 +85,6 @@ func (e *endpoint) WritePacket(_ *stack.Route, _ *stack.GSO, hdr buffer.Prependa
 
 	return nil
 }
+
+// Wait implements stack.LinkEndpoint.Wait.
+func (*endpoint) Wait() {}
diff --git a/pkg/tcpip/link/muxed/injectable.go b/pkg/tcpip/link/muxed/injectable.go
index 3ed7b98d1..7c946101d 100644
--- a/pkg/tcpip/link/muxed/injectable.go
+++ b/pkg/tcpip/link/muxed/injectable.go
@@ -104,6 +104,13 @@ func (m *InjectableEndpoint) WriteRawPacket(dest tcpip.Address, packet []byte) *
 	return endpoint.WriteRawPacket(dest, packet)
 }
 
+// Wait implements stack.LinkEndpoint.Wait.
+func (m *InjectableEndpoint) Wait() {
+	for _, ep := range m.routes {
+		ep.Wait()
+	}
+}
+
 // NewInjectableEndpoint creates a new multi-endpoint injectable endpoint.
 func NewInjectableEndpoint(routes map[tcpip.Address]stack.InjectableLinkEndpoint) *InjectableEndpoint {
 	return &InjectableEndpoint{
diff --git a/pkg/tcpip/link/sharedmem/sharedmem.go b/pkg/tcpip/link/sharedmem/sharedmem.go
index ba387af73..9e71d4edf 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem.go
@@ -132,7 +132,8 @@ func (e *endpoint) Close() {
 	}
 }
 
-// Wait waits until all workers have stopped after a Close() call.
+// Wait implements stack.LinkEndpoint.Wait. It waits until all workers have
+// stopped after a Close() call.
 func (e *endpoint) Wait() {
 	e.completed.Wait()
 }
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index e7b6d7912..e401dce44 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -240,6 +240,9 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 	return e.lower.WritePacket(r, gso, hdr, payload, protocol)
 }
 
+// Wait implements stack.LinkEndpoint.Wait.
+func (*endpoint) Wait() {}
+
 func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.View, gso *stack.GSO) {
 	// Figure out the network layer info.
 	var transProto uint8
diff --git a/pkg/tcpip/link/waitable/waitable.go b/pkg/tcpip/link/waitable/waitable.go
index 408cc62f7..5a1791cb5 100644
--- a/pkg/tcpip/link/waitable/waitable.go
+++ b/pkg/tcpip/link/waitable/waitable.go
@@ -120,3 +120,6 @@ func (e *Endpoint) WaitWrite() {
 func (e *Endpoint) WaitDispatch() {
 	e.dispatchGate.Close()
 }
+
+// Wait implements stack.LinkEndpoint.Wait.
+func (e *Endpoint) Wait() {}
diff --git a/pkg/tcpip/link/waitable/waitable_test.go b/pkg/tcpip/link/waitable/waitable_test.go
index 1031438b1..ae23c96b7 100644
--- a/pkg/tcpip/link/waitable/waitable_test.go
+++ b/pkg/tcpip/link/waitable/waitable_test.go
@@ -70,6 +70,9 @@ func (e *countedEndpoint) WritePacket(r *stack.Route, _ *stack.GSO, hdr buffer.P
 	return nil
 }
 
+// Wait implements stack.LinkEndpoint.Wait.
+func (*countedEndpoint) Wait() {}
+
 func TestWaitWrite(t *testing.T) {
 	ep := &countedEndpoint{}
 	wep := New(ep)
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index 4b3bd74fa..6a40e7ee3 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -144,6 +144,9 @@ func (*testObject) LinkAddress() tcpip.LinkAddress {
 	return ""
 }
 
+// Wait implements stack.LinkEndpoint.Wait.
+func (*testObject) Wait() {}
+
 // WritePacket is called by network endpoints after producing a packet and
 // writing it to the link endpoint. This is used by the test object to verify
 // that the produced packet is as expected.
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index 88a698b18..07e4c770d 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -295,6 +295,15 @@ type LinkEndpoint interface {
 	// IsAttached returns whether a NetworkDispatcher is attached to the
 	// endpoint.
 	IsAttached() bool
+
+	// Wait waits for any worker goroutines owned by the endpoint to stop.
+	//
+	// For now, requesting that an endpoint's worker goroutine(s) stop is
+	// implementation specific.
+	//
+	// Wait will not block if the endpoint hasn't started any goroutines
+	// yet, even if it might later.
+	Wait()
 }
 
 // InjectableLinkEndpoint is a LinkEndpoint where inbound packets are