Re: 2.6.7-rc2-mm2 udp multicast problem (sendto hangs)

[Martin Zwickel <martin.zwickel@technotrend.de>]

On Wed, 23 Jun 2004 13:34:57 +0300
Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> bubbled:

> On Wednesday 23 June 2004 12:56, Martin Zwickel wrote:
> > if I use MSG_DONTWAIT with sendto, I get temporarily unavailable resources
> > (many!):
> >
> > sendto(sendfd): Resource temporarily unavailable
> >
> > but isn't udp supposed to not block?
> 
> Think about what will happen if you will try to spew
> udp packets continuously:
> 
> while(1)
> 	sendto(...);
> 
> They will pile up in queue and eventually it will fill up.
> Then kernel may either drop excess packets silently
> or return you EAGAIN.

Yes, but why does the kernel not send out the queue?(I don't know if the queue
is empty or full when my sendto stops)
Without MSG_DONTWAIT, sendto waits endlessly. But on what?
Normally the kernel should put the queued packets on the line and accept new
ones, or did I misunderstand this?

My program sends out many udp packets, and sometimes it just stops until the
kernel receives a network packet or I access the local network(with arp
command).

So if I run arp in an endless loop(while :; do arp; done), sendto runs smooth.

For me it smells like a bug ;)

Martin

-- 
MyExcuse:
I'd love to help you -- it's just that the Boss won't let me near the computer.

Martin Zwickel <martin.zwickel@technotrend.de>
Research & Development

TechnoTrend AG <http://www.technotrend.de>