Re: [PATCH ipsec 4/7] xfrm: prevent AES-GCM nonce reuse after early GSO

[Sabrina Dubroca <sd@queasysnail.net>]

2026-09-30, 14:45:21 +0000, Jérémy Jean wrote:
> In the software ESP offload path, xfrm_output_gso() leaves its segments
> sharing a secpath extension. Each segment gets its own ESP sequence
> number, but stores it in the same xo->seq field for IV generation.
> 
> If encryption is delayed, later segments overwrite the value needed by
> earlier ones: esp*_xmit() can then encrypt several packets with the same
> AES-GCM nonce, despite their distinct ESP sequence numbers.

Here again, your commit message could describe much more precisely
what actually happens.

I'm guessing you mean something that starts like

xfrm_output_gso
  segs = skb0,skb1... all with the same xo
  ...
  xfrm_output_one(skb0)
    xfrm_replay_overflow(skb0) xo->seq = N
  xfrm_output_one(skb1)
    xfrm_replay_overflow(skb1) xo->seq = N+1
  ...

[and then some more stuff happens that gives them the right
esph->seq_no but wrong 64b seqno used for the IV]

But please help reviewers trace the codepath you've already gone down,
without having to guess what you mean. You don't need to give the full
call graph with the state of each variable, but there needs to be more
than just the very beginning and the very end.

-- 
Sabrina