From mboxrd@z Thu Jan 1 00:00:00 1970 From: William Manley Subject: Re: [PATCH] net: igmp: Reduce Unsolicited report interval to 1s when using IGMPv3 Date: Wed, 24 Jul 2013 14:45:08 +0100 Message-ID: <51EFDA64.4020409@youview.com> References: <1374527349.1635.55.camel@bwh-desktop.uk.level5networks.com> <1374673098-10295-1-git-send-email-william.manley@youview.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: To: William Manley Return-path: Received: from va3ehsobe003.messaging.microsoft.com ([216.32.180.13]:48567 "EHLO va3outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751243Ab3GXNpf (ORCPT ); Wed, 24 Jul 2013 09:45:35 -0400 Received: from mail26-va3 (localhost [127.0.0.1]) by mail26-va3-R.bigfish.com (Postfix) with ESMTP id 32B7D200BC for ; Wed, 24 Jul 2013 13:45:34 +0000 (UTC) Received: from VA3EHSMHS017.bigfish.com (unknown [10.7.14.237]) by mail26-va3.bigfish.com (Postfix) with ESMTP id D59453E016A for ; Wed, 24 Jul 2013 13:45:32 +0000 (UTC) In-Reply-To: <1374673098-10295-1-git-send-email-william.manley@youview.com> Sender: netdev-owner@vger.kernel.org List-ID: On 24/07/13 14:38, William Manley wrote: > If an IGMP join packet is lost you will not receive data sent to the > multicast group so if no data arrives from that multicast group in a > period of time after the IGMP join a second IGMP join will be sent. The > delay between joins is the "IGMP Unsolicited Report Interval". > > Previously this value was hard coded to be chosen randomly between 0-10s. > This can be too long for some use-cases, such as IPTV as it can cause > channel change to be slow in the presence of packet loss. > > The value 10s has come from IGMPv2 RFC2236, which was reduced to 1s in > IGMPv3 RFC3376. This patch makes the kernel use the 1s value from the > later RFC if we are operating in IGMPv3 mode. IGMPv2 behaviour is > unaffected. > > Tested with Wireshark and a simple program to join a (non-existant) > multicast group. The distribution of timings for the second join differ > based upon setting /proc/sys/net/ipv4/conf/eth0/force_igmp_version. > --- > net/ipv4/igmp.c | 17 ++++++++++++++--- > 1 file changed, 14 insertions(+), 3 deletions(-) I'm also working on a patch which builds on this adding a procfs knob similar to force_igmp_version but called "force_igmp_unsolicited_report_interval". This will allow the interval to be overridden from user-space independent of the version of IGMP in use as for our use-case we want the interval to be short even for IGMPv2. Thanks Will