From owner-freebsd-net  Tue Mar 13 17:56:41 2001
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Date: Tue, 13 Mar 2001 20:56:32 -0500 (EST)
From: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
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To: Lars Eggert <larse@ISI.EDU>
Cc: net@FreeBSD.ORG
Subject: Changing UDP select() behavior
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<<On Tue, 13 Mar 2001 16:43:26 -0800, Lars Eggert <larse@ISI.EDU> said:

> I'm considering changing this, so that a select-to-write on a UDP socket
> will block until queue space becomes available.

Impossible.  The only way to find out whether a packet (or set of
packets, or a fragment of a packet) would be successfully enqueued is
to try it.  Even then there's no guarantee that it will get sent.

(Actually, ``impossible'' is too strong -- we could restructure the
entire network stack to make it possible to speculatively send packets
just to support this change in select() semantics.  It's merely
impractical.)

-GAWollman


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