netdev - Re: [PATCH net] tcp: fix fastopen code vs usec TS

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Message-ID: <CADVnQy=Ln_SyA=VBxNNSPBqt8KY11k0tDtXZtHMxBoyatcF5Wg@mail.gmail.com>
Date: Tue, 31 Oct 2023 08:03:33 -0400
From: Neal Cardwell <ncardwell@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	kernel test robot <oliver.sang@...el.com>, David Morley <morleyd@...gle.com>
Subject: Re: [PATCH net] tcp: fix fastopen code vs usec TS

On Tue, Oct 31, 2023 at 2:19 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> After blamed commit, TFO client-ack-dropped-then-recovery-ms-timestamps
> packetdrill test failed.
>
> David Morley and Neal Cardwell started investigating and Neal pointed
> that we had :
>
> tcp_conn_request()
>   tcp_try_fastopen()
>    -> tcp_fastopen_create_child
>      -> child = inet_csk(sk)->icsk_af_ops->syn_recv_sock()
>        -> tcp_create_openreq_child()
>           -> copy req_usec_ts from req:
>           newtp->tcp_usec_ts = treq->req_usec_ts;
>           // now the new TFO server socket always does usec TS, no matter
>           // what the route options are...
>   send_synack()
>     -> tcp_make_synack()
>         // disable tcp_rsk(req)->req_usec_ts if route option is not present:
>         if (tcp_rsk(req)->req_usec_ts < 0)
>                 tcp_rsk(req)->req_usec_ts = dst_tcp_usec_ts(dst);
>
> tcp_conn_request() has the initial dst, we can initialize
> tcp_rsk(req)->req_usec_ts there instead of later in send_synack();
>
> This means tcp_rsk(req)->req_usec_ts can be a boolean.
>
> Many thanks to David an Neal for their help.
>
> Fixes: 614e8316aa4c ("tcp: add support for usec resolution in TCP TS values")
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Closes: https://lore.kernel.org/oe-lkp/202310302216.f79d78bc-oliver.sang@intel.com
> Suggested-by: Neal Cardwell <ncardwell@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: David Morley <morleyd@...gle.com>
> ---

Looks great to me. Thanks, Eric!

Acked-by: Neal Cardwell <ncardwell@...gle.com>

neal