Question

In Scapy (or even just Python, for that sake), how do I get the size in bytes of a given packet?
I’m tempted to use the function len but I’m not sure what exactly it returns in the case of packets.

>>> len(IP(dst="www.google.com"))
20

>>> len(IP(dst="www.google.com")/TCP(dport=80))
40

Answer 1

>>> len(IP(dst="www.google.com"))
20

There are 20 bytes in a minimal IP header.

>>> len(IP(dst="www.google.com")/TCP(dport=80))
40

There are another 20 bytes in a minimal TCP header (20+20==40).

So it seems that len is returning the packet length.