On Mon, 24 Jan 2022 at 15:13, Maxim Mikityanskiy [off-list ref] wrote:

bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie expect the full length
of the TCP header (with all extensions). Fix the documentation that says
it should be sizeof(struct tcphdr).

I don't understand this change, sorry. Are you referring to the fact
that the check is len < sizeof(*th) instead of len != sizeof(*th)?

Your commit message makes me think that the helpers will access data
in the extension headers, which isn't true as far as I can tell. That
would be a problem in fact, since it could be used to read memory that
the verifier hasn't deemed safe.

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