Guard e2e udp and tun channels when closed (#934)

overlay/tun_tester.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"net"
 	"os"
+	"sync/atomic"
 
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/cidr"
@@ -21,6 +22,7 @@ type TestTun struct {
 	routeTree *cidr.Tree4
 	l         *logrus.Logger
 
+	closed    atomic.Bool
 	rxPackets chan []byte // Packets to receive into nebula
 	TxPackets chan []byte // Packets transmitted outside by nebula
 }
@@ -50,6 +52,10 @@ func newTunFromFd(_ *logrus.Logger, _ int, _ *net.IPNet, _ int, _ []Route, _ int
 // These are unencrypted ip layer frames destined for another nebula node.
 // packets should exit the udp side, capture them with udpConn.Get
 func (t *TestTun) Send(packet []byte) {
+	if t.closed.Load() {
+		return
+	}
+
 	if t.l.Level >= logrus.DebugLevel {
 		t.l.WithField("dataLen", len(packet)).Debug("Tun receiving injected packet")
 	}
@@ -98,6 +104,10 @@ func (t *TestTun) Name() string {
 }
 
 func (t *TestTun) Write(b []byte) (n int, err error) {
+	if t.closed.Load() {
+		return 0, io.ErrClosedPipe
+	}
+
 	packet := make([]byte, len(b), len(b))
 	copy(packet, b)
 	t.TxPackets <- packet
@@ -105,7 +115,10 @@ func (t *TestTun) Write(b []byte) (n int, err error) {
 }
 
 func (t *TestTun) Close() error {
-	close(t.rxPackets)
+	if t.closed.CompareAndSwap(false, true) {
+		close(t.rxPackets)
+		close(t.TxPackets)
+	}
 	return nil
 }