Merge branch 'bpf-max-pkt-offset'

Jiong Wang says:

====================
The maximum packet offset accessed by one BPF program is useful
information.

Because sometimes there could be packet split and it is possible for some
reasons (for example performance) we want to reject the BPF program if the
maximum packet size would trigger such split. Normally, MTU value is
treated as the maximum packet size, but one BPF program does not always
access the whole packet, it could only access the head portion of the data.

We could let verifier calculate the maximum packet offset ever used and
record it inside prog auxiliar information structure as a new field
"max_pkt_offset".
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>