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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Dan Akunis <dan.akunis@gmail.com>
Cc: labbott@redhat.com, David Miller <davem@davemloft.net>,
	kuznet@ms2.inr.ac.ru, jmorris@namei.org, yoshfuji@linux-ipv6.org,
	kaber@trash.net, samanthakumar@google.com, willemb@google.com,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [REGRESSION] Select hang with zero sized UDP packets
Date: Wed, 24 Aug 2016 06:02:15 -0700	[thread overview]
Message-ID: <1472043735.14381.69.camel@edumazet-glaptop3.roam.corp.google.com> (raw)
In-Reply-To: <2ABF798B42E64D9C89DEB806A2E636B5@mtl.com>

On Wed, 2016-08-24 at 11:22 +0300, Dan Akunis wrote:
> When select wakes up on a UDP socket, user is expecting to get data. Getting 
> 0 from recvfrom() or whatever read function she uses, is a wrong attitude.
> I agree with David.
> 
> The unit test that expects select to wake up is wrong and should be changed.
> 

Please do not top post on netdev mailing list.

Program is fine and wont be changed to work around a kernel bug.

We definitely can send and receive UDP messages with 0 payload.

So select() should unblock when one such frame is received, otherwise
you could fill up the receive queue with a lot of frames like that and
when SO_RCVBUF limit is reached, block future messages.

UDP is a datagram protocol.

Bug fix is merged :
https://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=e83c6744e81abc93a20d0eb3b7f504a176a6126a

  reply	other threads:[~2016-08-24 13:02 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-23 17:53 [REGRESSION] Select hang with zero sized UDP packets Laura Abbott
2016-08-23 18:25 ` David Miller
2016-08-23 19:03   ` Eric Dumazet
2016-08-23 20:06     ` Laura Abbott
2016-08-23 20:42       ` Eric Dumazet
2016-08-23 20:53       ` [PATCH net] udp: fix poll() issue with zero sized packets Eric Dumazet
2016-08-23 20:56         ` Eric Dumazet
2016-08-23 20:59         ` [PATCH v2 " Eric Dumazet
2016-08-23 23:39           ` David Miller
2016-08-24  8:22   ` [REGRESSION] Select hang with zero sized UDP packets Dan Akunis
2016-08-24 13:02     ` Eric Dumazet [this message]
2016-08-24 13:42     ` One Thousand Gnomes

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