How to read whole ip layer and tcp layer from a packet when using scapy?

Question

I am doing a TCP retransmission behavior test when receiving ICMP Destination unreachable (Fragmentation needed ICMP TYPE=3 CODE=4) message with scapy.

The test flow like this:
1. Establish a TCP connection to the server
2. Send a HTTP GET request to the server when TCP is established
3. When HTTP Response back
4. Send an ICMP type 3 code 4 message to the server with s small MTU set

The question is that ICMP TYPE=3 CODE=4 message include the IP Header and partial TCP header (srt, dst and seq number) of that HTTP Response packets. Currently, I just read each paramemter (like IP identification, frag tag, ttl etc.) from that HTTP Response packets. The question is: is there any way that I can read the whole IP and TCP header from that packet:

ICMP(TYPE=3 CODE=4)/IP Header/TCP Header

Answer 1

Hopefully the following will help:

>>> pkt = ICMP()/IP()/TCP()
>>> ip_header = pkt.getlayer(IP) 
>>> ip_header 
<IP  frag=0 proto=tcp |<TCP  |>>
>>> 

To retrieve just the IP header:

>>> pkt = Ether()/IP()/TCP()
>>> ip = pkt.getlayer(IP)
>>> ip
<IP  frag=0 proto=tcp |<TCP  |>>
>>> ip.remove_payload()
>>> ip
<IP  |>
>>>