[tunnel/connection] AI does not know RFC 791

Author: dilyevsky

pkg/tunnel/connection/muxed_conn.go

@@ -145,7 +145,7 @@ func (m *MuxedConn) WritePacket(pkt []byte) ([]byte, error) {
 // IPv4 packet (RFC 791)
 if len(pkt) >= 20 {
 var addr [4]byte
-copy(addr[:], pkt[12:16])
+copy(addr[:], pkt[16:20])
 dstIP = netip.AddrFrom4(addr)
 } else {
 return nil, fmt.Errorf("IPv4 packet too short: %d", len(pkt))