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SubjectRe: [PATCH][TCP]: simplify tcp_mark_lost_retrans()
Ilpo Järvinen schrieb:
> On Wed, 7 Jan 2009, Arnd Hannemann wrote:
>
>
>> I noticed
>>
>
> Good that somebody else is looking TCP code besides me... :-)
>
Well I try hard... ;-)
>
>> that in tcp_mark_lost_retrans the for-loop is only entered
>> if tcp_is_fack(tp) evaluates to true:
>>
>> if (!tcp_is_fack(tp) || !tp->retrans_out ||
>> !after(received_upto, tp->lost_retrans_low) ||
>> icsk->icsk_ca_state != TCP_CA_Recovery)
>> return;
>>
>> Therefore the following check in the for-loop seems to be redundant,
>> because it always evaluates to true:
>>
>> (tcp_is_fack(tp) ||
>> !before(received_upto,
>> ack_seq + tp->reordering * tp->mss_cache))
>>
>> Did I miss something?
>>
>
> It was just a left over from the RFC3517 SACK addition which added that
> !tcp_is_fack(tp) there above. ...It would have been nice to have similar
> lost rexmit feature without FACK as well but calculating that wasn't
> trivial (or I didn't find that too trivial) and could end up being
> extremely expensive in case of large holes. (So I also left it there as
> sort of reminder).
>
Perhaps it would be better to let the comments reflect
what you just said and remove the redundant check
anyway to reduce the dead code a newcomer has to understand ;-)
I would have included a patch for the comments, but as you have a
deeper understanding of the code it would probably
be better if you can do it.

Best regards,
Arnd



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