net/packet: add IPv6 source and destination IPs to Parsed.

Signed-off-by: David Anderson <danderson@tailscale.com>

wgengine/tstun/tun.go

@@ -283,7 +283,7 @@ func (t *TUN) Read(buf []byte, offset int) (int, error) {
 	p.Decode(buf[offset : offset+n])
 
 	if m, ok := t.destIPActivity.Load().(map[packet.IP4]func()); ok {
-		if fn := m[p.DstIP]; fn != nil {
+		if fn := m[p.DstIP4]; fn != nil {
 			fn()
 		}
 	}