Subject: Re: [PATCH v4 3/3] net: igmp: Allow user-space configuration of igmp unsolicited report interval

From: Benjamin LaHaise <[email-masked]>
Date: Wed, 7 Aug 2013 09:43:41 -0400

On Tue, Aug 06, 2013 at 07:03:15PM +0100, William Manley wrote:
> Adds the new procfs knobs:
> 
>     /proc/sys/net/ipv4/conf/*/igmpv2_unsolicited_report_interval
>     /proc/sys/net/ipv4/conf/*/igmpv3_unsolicited_report_interval
> 
> Which will allow userspace configuration of the IGMP unsolicited report
> interval (see below) in milliseconds.  The defaults are 10000ms for IGMPv2
> and 1000ms for IGMPv3 in accordance with RFC2236 and RFC3376.
> 
> Background:
> 
> 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".
> 
> Prior to this patch this value was hard coded in the kernel to 10s for
> IGMPv2 and 1s for IGMPv3.  10s is unsuitable for some use-cases, such as
> IPTV as it can cause channel change to be slow in the presence of packet
> loss.
> 
> This patch allows the value to be overridden from userspace for both
> IGMPv2 and IGMPv3 such that it can be tuned accoding to the network.
> 
> Tested with Wireshark and a simple program to join a (non-existent)
> multicast group.  The distribution of timings for the second join differ
> based upon setting the procfs knobs.
> 
> igmpvX_unsolicited_report_interval is intended to follow the pattern
> established by force_igmp_version, and while a procfs entry has been added
> a corresponding sysctl knob has not as it is my understanding that sysctl
> is deprecated[1].
> 
> [1]: http://lwn.net/Articles/247243/
> 
> Signed-off-by: William Manley <[email-masked]>

Acked-by: Benjamin LaHaise <[email-masked]>

Also good.  Thanks!

		-ben

> ---
>  include/linux/inetdevice.h |    2 ++
>  net/ipv4/devinet.c         |    8 ++++++++
>  net/ipv4/igmp.c            |   19 +++++++++++++++++--
>  3 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
> index d4c56fc..43b3c72 100644
> --- a/include/linux/inetdevice.h
> +++ b/include/linux/inetdevice.h
> @@ -28,6 +28,8 @@ enum
>  	IPV4_DEVCONF_ARPFILTER,
>  	IPV4_DEVCONF_MEDIUM_ID,
>  	IPV4_DEVCONF_FORCE_IGMP_VERSION,
> +	IPV4_DEVCONF_IGMPV2_UNSOLICITED_REPORT_INTERVAL,
> +	IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL,
>  	IPV4_DEVCONF_NOXFRM,
>  	IPV4_DEVCONF_NOPOLICY,
>  	IPV4_DEVCONF_ARP_ANNOUNCE,
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index a9561c4..56ecb1b 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -73,6 +73,8 @@ static struct ipv4_devconf ipv4_devconf = {
>  		[IPV4_DEVCONF_SEND_REDIRECTS - 1] = 1,
>  		[IPV4_DEVCONF_SECURE_REDIRECTS - 1] = 1,
>  		[IPV4_DEVCONF_SHARED_MEDIA - 1] = 1,
> +		[IPV4_DEVCONF_IGMPV2_UNSOLICITED_REPORT_INTERVAL - 1] = 10000 /*ms*/,
> +		[IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL - 1] =  1000 /*ms*/,
>  	},
>  };
>  
> @@ -83,6 +85,8 @@ static struct ipv4_devconf ipv4_devconf_dflt = {
>  		[IPV4_DEVCONF_SECURE_REDIRECTS - 1] = 1,
>  		[IPV4_DEVCONF_SHARED_MEDIA - 1] = 1,
>  		[IPV4_DEVCONF_ACCEPT_SOURCE_ROUTE - 1] = 1,
> +		[IPV4_DEVCONF_IGMPV2_UNSOLICITED_REPORT_INTERVAL - 1] = 10000 /*ms*/,
> +		[IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL - 1] =  1000 /*ms*/,
>  	},
>  };
>  
> @@ -2096,6 +2100,10 @@ static struct devinet_sysctl_table {
>  		DEVINET_SYSCTL_RW_ENTRY(PROXY_ARP_PVLAN, "proxy_arp_pvlan"),
>  		DEVINET_SYSCTL_RW_ENTRY(FORCE_IGMP_VERSION,
>  					"force_igmp_version"),
> +		DEVINET_SYSCTL_RW_ENTRY(IGMPV2_UNSOLICITED_REPORT_INTERVAL,
> +					"igmpv2_unsolicited_report_interval"),
> +		DEVINET_SYSCTL_RW_ENTRY(IGMPV3_UNSOLICITED_REPORT_INTERVAL,
> +					"igmpv3_unsolicited_report_interval"),
>  
>  		DEVINET_SYSCTL_FLUSHING_ENTRY(NOXFRM, "disable_xfrm"),
>  		DEVINET_SYSCTL_FLUSHING_ENTRY(NOPOLICY, "disable_policy"),
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 9f0aaea..c5541da 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -141,10 +141,25 @@
>  
>  static int unsolicited_report_interval(struct in_device *in_dev)
>  {
> +	int interval_ms, interval_jiffies;
> +
>  	if (IGMP_V1_SEEN(in_dev) || IGMP_V2_SEEN(in_dev))
> -		return IGMP_V2_Unsolicited_Report_Interval;
> +		interval_ms = IN_DEV_CONF_GET(
> +			in_dev,
> +			IGMPV2_UNSOLICITED_REPORT_INTERVAL);
>  	else /* v3 */
> -		return IGMP_V3_Unsolicited_Report_Interval;
> +		interval_ms = IN_DEV_CONF_GET(
> +			in_dev,
> +			IGMPV3_UNSOLICITED_REPORT_INTERVAL);
> +
> +	interval_jiffies = msecs_to_jiffies(interval_ms);
> +
> +	/* _timer functions can't handle a delay of 0 jiffies so ensure
> +	 *  we always return a positive value.
> +	 */
> +	if (interval_jiffies <= 0)
> +		interval_jiffies = 1;
> +	return interval_jiffies;
>  }
>  
>  static void igmpv3_add_delrec(struct in_device *in_dev, struct ip_mc_list *im);
> -- 
> 1.7.10.4

-- 
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