python - Scapy - insert packet layer between two other layers -


i doing little networking project using scapy library python. project involves sniffing in packets, , shimming new layer between layers 3 , 4.

using guide, http://www.secdev.org/projects/scapy/doc/build_dissect.html

i able create new packet layer. can add layer on top of existing packet doing like, 

packet = newlayer()/packet

and newlayer() layer placed below ip layer. want, however, sandwich new layer between layers 3 , 4 (instead of below ip). can't seem figure out easy way accomplish this.

i know can create new packet , like,

packet = ether()/ip()/newlayer()/tcp()

however since, want insert layer packets i've sniffed, i'd modify original packet instead of creating new packet scratch.

any appreciated!

here's example shows how inject dot1q() header between layer 1 , layer 2 (counting ether() layer 0):

>>> pkt = ether() / dot1q() / ip() / tcp() >>> payload = pkt.getlayer(1).payload >>> payload <ip  frag=0 proto=tcp |<tcp  |>> >>> pkt.getlayer(1).remove_payload() >>> pkt <ether  type=n_802_1q |<dot1q  |>> >>> newpkt = pkt / dot1q() / payload >>> newpkt <ether  type=n_802_1q |<dot1q  type=n_802_1q |<dot1q  type=ipv4 |<ip  frag=0 proto=tcp |<tcp  |>>>>> >>>

there may easier way, above easy enough think.


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