netdev - Re: Problem with semantics?

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Date:	14 Aug 2007 02:38:13 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Shay Goikhman <GOIKHMAN@...ibm.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, mtk-manpages@....net
Subject: Re: Problem with semantics?

Shay Goikhman <GOIKHMAN@...ibm.com> writes:

> Dear Linux maintainers,
> 
>  I'm doing :
> 
>       setsockopt(s,  SO_RCVTIMEO, t1 );                  // set time-out
> t1 on socket while block receiving on it
>       select(,,, &fd_set_including(s), .., &errs, t2);      // block till
> receive or time-out  t 2 jointly on a set of sockets
> 
> Apparently, I could no find reference on the coupled behavior of the two
> above statements in Linux documentation.
> As I understand the blocking semantics, I would expect  that  if t1<t2 ,
> select should return after t1 with the descriptor 's' in 'errs' if 's' does
> not become readable in the t1 interval.
> 
> It is not so in life -- select ignores t1 altogether.
> 
> Do you have some enlightening knowledge on the matter?

RCVTIMEO only applies to recvmsg et.al., similar to SNDTIMEO only
apply to sendmsg etc. But select/poll only report events, they
do not actually send or receive by themselves.

Michael, perhaps you can clarify that in the manpages

-Andi
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