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Date:      Wed, 7 Feb 2001 10:59:06 -0800
From:      Alfred Perlstein <bright@wintelcom.net>
To:        Luigi Rizzo <rizzo@aciri.org>
Cc:        net@FreeBSD.ORG
Subject:   Re: send problem on udp socket...
Message-ID:  <20010207105906.O26076@fw.wintelcom.net>
In-Reply-To: <200102071757.f17HvGu75581@iguana.aciri.org>; from rizzo@aciri.org on Wed, Feb 07, 2001 at 09:57:16AM -0800
References:  <20010207093731.N26076@fw.wintelcom.net> <200102071757.f17HvGu75581@iguana.aciri.org>

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* Luigi Rizzo <rizzo@aciri.org> [010207 09:57] wrote:
> 
> not really. The problem is not running out of mbufs, is that the
> interface queue (usually limited to net.inet.ip.intr_queue_maxlen)
> fills up, and this has nothing to do with NMBCLUSTERS. This used
> not to be a problem in the past precisely because boxes were slower
> than ethernet cards.
> 
> And trying to push through a device more than it can handle
> happens all the time with disks, and it is the reason why
> you want to have blocking behaviour.
> 
> <proposed solution skipped because it seems to deal with mbuf
>  exhaustion whereas the problem is elsewhere>

Oh, sorry, I'm pretty used to seeing the issue I _thought_ you
brought up so I instictively sent the pre-thought out message. :)

> Re. the race that you mention below, again it happens all
> the times -- select tells you can do X, then someone else
> is faster and your X syscall fails. See the case of multiple
> servers trying to accept() on a socket.

Er, that I understand.  But it's not that expected when you're
the only one writing/accepting.  I guess defensive coding is
a good thing. :)

Since this is UDP, I'm not sure much should be done, perhaps
just document the return value, but honestly since it's _U_DP
it could just easily fail silently as long as local datagrams
are allowed to be lossy.

-- 
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."


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