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SubjectRe: [PATCH] sctp: do trace_sctp_probe after SACK validation and check
On Fri, Dec 20, 2019 at 04:47:03AM +0000, Kevin Kou wrote:
> The function sctp_sf_eat_sack_6_2 now performs
> the Verification Tag validation, Chunk length validation, Bogu check,
> and also the detection of out-of-order SACK based on the RFC2960
> Section 6.2 at the beginning, and finally performs the further
> processing of SACK. The trace_sctp_probe now triggered before
> the above necessary validation and check.
>
> This patch is to do the trace_sctp_probe after the necessary check
> and validation to SACK.
>
> Signed-off-by: Kevin Kou <qdkevin.kou@gmail.com>
> ---
> net/sctp/sm_statefuns.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index 42558fa..b4a54df 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -3281,7 +3281,6 @@ enum sctp_disposition sctp_sf_eat_sack_6_2(struct net *net,
> struct sctp_sackhdr *sackh;
> __u32 ctsn;
>
> - trace_sctp_probe(ep, asoc, chunk);
>
> if (!sctp_vtag_verify(chunk, asoc))
> return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
> @@ -3319,6 +3318,8 @@ enum sctp_disposition sctp_sf_eat_sack_6_2(struct net *net,
> if (!TSN_lt(ctsn, asoc->next_tsn))
> return sctp_sf_violation_ctsn(net, ep, asoc, type, arg, commands);
>
> + trace_sctp_probe(ep, asoc, chunk);
> +

Moving it here will be after the check against ctsn_ack_point, which
could cause duplicated SACKs to be missed from the log.

Yes, from the sender-side CC we don't care about it (yet), but it
helps to spot probably avoidable retransmissions.

I think this is cleaning up the noise too much. I can agree with
moving it to after the chunk sanity tests, though.

> /* Return this SACK for further processing. */
> sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_SACK, SCTP_CHUNK(chunk));
>
> --
> 1.8.3.1
>

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