netdev - Re: UDP splice

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Message-ID: <CACYKsS5uy6nGbtCYit0eNyBSemzimgLrVdUJAgeBmZwDAy7F-A@mail.gmail.com>
Date:	Mon, 24 Jun 2013 14:09:19 -0300
From:	Ricardo Landim <ricardolan@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>,
	Ricardo Landim <ricardolan@...il.com>, netdev@...r.kernel.org
Subject: Re: UDP splice

Useful for UDP proxy, mainly for RTP payload including voice (voip)
and video live stream...

2013/6/24 Hannes Frederic Sowa <hannes@...essinduktion.org>:
> On Mon, Jun 24, 2013 at 05:02:56PM +0100, Ben Hutchings wrote:
>> On Mon, 2013-06-24 at 17:51 +0200, Hannes Frederic Sowa wrote:
>> > On Mon, Jun 24, 2013 at 04:42:34PM +0100, Ben Hutchings wrote:
>> > > splice() works with streams, but UDP is a message-oriented protocol.
>> > > How would a UDP implementation of splice() decide where to put the
>> > > message boundaries, or to distinguish the messages?
>> >
>> > Splicing a pipe to udp socket should work nontheless. Splicing from udp socket
>> > to pipe does not work.
>>
>> Should it?  I suppose it could work for UDP-based protocols that include
>> their own framing, but I can't see that it's generally useful.
>
> It is the same with sendfile: One splice-call would result in one udp
> message and could span several ip fragments. So, message boundaries
> would be maintained. splice is good for large data but the generation of
> fragments defeat its use here.
>
> I don't know what would be most suitable to use for copying udp fragments
> from one socket to another socket. I would have tried recvmmsg/sendmmsg.
>
> Greetings,
>
>   Hannes
>
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