Re: [PATCH] net: igmp: Reduce Unsolicited report interval to 1s when using IGMPv3
From: Sergei Shtylyov <hidden>
Date: 2013-07-24 14:51:32
Hello. On 24-07-2013 17:38, 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(-)
quoted hunk ↗ jump to hunk
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index d8c2327..f8142df 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c
[...]
quoted hunk ↗ jump to hunk
@@ -138,6 +139,15 @@ ((in_dev)->mr_v2_seen && \ time_before(jiffies, (in_dev)->mr_v2_seen))) +static int unsolicited_report_interval(struct in_device *in_dev) +{ + if (IGMP_V2_SEEN(in_dev)) { + return IGMP_V2_Unsolicited_Report_Interval; + } else { /* v3 */ + return IGMP_V3_Unsolicited_Report_Interval; + }
{} not needed on either arm of *if*. I guess scripts/checkpatch.pl should
have warned you...
WBR, Sergei