3 files changed, 32 insertions, 6 deletions
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index 9b5fa3f6e..81aba0923 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -105,6 +105,18 @@ func (e *endpoint) handleICMP(r *stack.Route, vv buffer.VectorisedView) {
 		pkt[icmpV6OptOffset] = ndpOptDstLinkAddr
 		pkt[icmpV6LengthOffset] = 1
 		copy(pkt[icmpV6LengthOffset+1:], r.LocalLinkAddress[:])
+
+		// ICMPv6 Neighbor Solicit messages are always sent to
+		// specially crafted IPv6 multicast addresses. As a result, the
+		// route we end up with here has as its LocalAddress such a
+		// multicast address. It would be nonsense to claim that our
+		// source address is a multicast address, so we manually set
+		// the source address to the target address requested in the
+		// solicit message. Since that requires mutating the route, we
+		// must first clone it.
+		r := r.Clone()
+		defer r.Release()
+		r.LocalAddress = targetAddr
 		pkt.SetChecksum(icmpChecksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
 		r.WritePacket(hdr, buffer.VectorisedView{}, header.ICMPv6ProtocolNumber, r.DefaultTTL())
 
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index e548784ac..a8eef4cf2 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -41,6 +41,11 @@ var (
 	lladdr1 = header.LinkLocalAddr(linkAddr1)
 )
 
+type icmpInfo struct {
+	typ header.ICMPv6Type
+	src tcpip.Address
+}
+
 type testContext struct {
 	t  *testing.T
 	s0 *stack.Stack
@@ -49,7 +54,7 @@ type testContext struct {
 	linkEP0 *channel.Endpoint
 	linkEP1 *channel.Endpoint
 
-	icmpCh chan header.ICMPv6Type
+	icmpCh chan icmpInfo
 }
 
 type endpointWithResolutionCapability struct {
@@ -65,7 +70,7 @@ func newTestContext(t *testing.T) *testContext {
 		t:      t,
 		s0:     stack.New([]string{ProtocolName}, []string{ping.ProtocolName6}, stack.Options{}),
 		s1:     stack.New([]string{ProtocolName}, []string{ping.ProtocolName6}, stack.Options{}),
-		icmpCh: make(chan header.ICMPv6Type, 10),
+		icmpCh: make(chan icmpInfo, 10),
 	}
 
 	const defaultMTU = 65536
@@ -132,7 +137,10 @@ func (c *testContext) countPacket(pkt channel.PacketInfo) {
 	}
 	b := pkt.Header[header.IPv6MinimumSize:]
 	icmp := header.ICMPv6(b)
-	c.icmpCh <- icmp.Type()
+	c.icmpCh <- icmpInfo{
+		typ: icmp.Type(),
+		src: ipv6.SourceAddress(),
+	}
 }
 
 func (c *testContext) routePackets(ch <-chan channel.PacketInfo, ep *channel.Endpoint) {
@@ -198,8 +206,14 @@ func TestLinkResolution(t *testing.T) {
 		case <-ctx.Done():
 			t.Errorf("timeout waiting for ICMP, got: %#+v", stats)
 			return
-		case typ := <-c.icmpCh:
-			stats[typ]++
+		case icmpInfo := <-c.icmpCh:
+			switch icmpInfo.typ {
+			case header.ICMPv6NeighborAdvert:
+				if got, want := icmpInfo.src, lladdr1; got != want {
+					t.Errorf("got ICMPv6NeighborAdvert.sourceAddress = %v, want = %v", got, want)
+				}
+			}
+			stats[icmpInfo.typ]++
 
 			if stats[header.ICMPv6NeighborSolicit] > 0 &&
 				stats[header.ICMPv6NeighborAdvert] > 0 &&
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index e1f4ea863..25bd998e5 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -91,7 +91,7 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload b
 		PayloadLength: length,
 		NextHeader:    uint8(protocol),
 		HopLimit:      ttl,
-		SrcAddr:       e.id.LocalAddress,
+		SrcAddr:       r.LocalAddress,
 		DstAddr:       r.RemoteAddress,
 	})
 	r.Stats().IP.PacketsSent.Increment()