Re: Packet rate limiting

On Sun, Jul 13, 2003 at 02:26:24AM +0200, alessandro salvatori wrote:
> when you say a thing is not athomic you presume that it returns even though what was fired by it had not yet ended. if you set the send buffer to zero as in the patch i submitted today it won't return till everything is done. sure, this is not suitable for real-time applications... since a context switch would make we wait... but we would wait all the same even if it returned much before the kernel did write the packet to the wire. hence, this way, when we go on we go on because the packet is written.

/me scratches head

Uh, where are you reading that setting SO_SNDBUF to 0, it blocks until "everything is done"? My understanding is that the SO_SNDBUF changes the advertized window size under TCP and the max datagram size under UDP. Obviously we're talking about a different socket type, but my gut says that it would work the same was as a UDP socket. I would expect that setting SO_SNDBUF to 0 would result in an ENOBUFS error foreach packet assuming that the kernel would let you set it that low (I would hope not).

You might have better luck setting SO_PRIORITY which under Linux at least is used to prioritize the network queues.

If you're right, then I'll be adding that trick in tcpreplay. :-)

-- 
Aaron Turner   
http://synfin.net/aturner
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