Clear pending packet queue when nic is removed.

Updates #6910

PiperOrigin-RevId: 428925334

pkg/tcpip/stack/nic.go

@@ -316,9 +316,13 @@ func (n *nic) remove() tcpip.Error {
 		ep.Close()
 	}
 
+	// drain and drop any packets pending link resolution.
+	n.linkResQueue.cancel()
+
 	// Prevent packets from going down to the link before shutting the link down.
 	n.qDisc.Close()
 	n.NetworkLinkEndpoint.Attach(nil)
+
 	return nil
 }
 

pkg/tcpip/stack/pending_packets.go

@@ -70,6 +70,20 @@ func (f *packetsPendingLinkResolution) init(nic *nic) {
 	f.mu.packets = make(map[<-chan struct{}][]pendingPacket)
 }
 
+// cancel drains all pending packet queues and release all packet
+// references.
+func (f *packetsPendingLinkResolution) cancel() {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	for ch, pendingPackets := range f.mu.packets {
+		for _, p := range pendingPackets {
+			p.pkt.DecRef()
+		}
+		delete(f.mu.packets, ch)
+	}
+	f.mu.cancelChans = nil
+}
+
 // dequeue any pending packets associated with ch.
 //
 // If err is nil, packets will be written and sent to the given remote link