bind vxlan-gpe over udp on port 4790 (#424)

* bind vxlan-gpe over udp on port 4790

As defined here :
https://tools.ietf.org/html/draft-ietf-nvo3-vxlan-gpe-03#section-5.3



Signed-off-by: Gabriel Ganne <gabriel.ganne@qosmos.com>

* Typo fixed

scapy/layers/vxlan.py

@@ -64,7 +64,8 @@ class VXLAN(Packet):
         else:
             return self.sprintf("VXLAN (vni=%VXLAN.vni%)")
 
-bind_layers(UDP, VXLAN, dport=4789)  # RFC standard port
+bind_layers(UDP, VXLAN, dport=4789)  # RFC standard vxlan port
+bind_layers(UDP, VXLAN, dport=4790)  # RFC standard vxlan-gpe port
 bind_layers(UDP, VXLAN, dport=6633)  # New IANA assigned port for use with NSH
 bind_layers(UDP, VXLAN, dport=8472)  # Linux implementation port
 bind_layers(VXLAN, Ether, {'flags': 0x8})