| Message ID | 6112e6ccb97c5015b6f8125d8c0f75c179b53198.1440689853.git.pdowney@brocade.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Philip Downey <pdowney@brocade.com> Date: Thu, 27 Aug 2015 16:46:26 +0100 > The range of addresses between 224.0.0.0 and 224.0.0.255 inclusive, is > reserved for the use of routing protocols and other low-level topology > discovery or maintenance protocols, such as gateway discovery and > group membership reporting. Multicast routers should not forward any > multicast datagram with destination addresses in this range, > regardless of its TTL. > > Currently, IGMP reports are generated for this reserved range of > addresses even though a router will ignore this information since it > has no purpose. However, the presence of reserved group addresses in > an IGMP membership report uses up network bandwidth and can also > obscure addresses of interest when inspecting membership reports using > packet inspection or debug messages. > > Although the RFCs for the various version of IGMP (e.g.RFC 3376 for > v3) do not specify that the reserved addresses be excluded from > membership reports, it should do no harm in doing so. In particular > there should be no adverse effect in any IGMP snooping functionality > since 224.0.0.x is specifically excluded as per RFC 4541 (IGMP and MLD > Snooping Switches Considerations) section 2.1.2. Data Forwarding > Rules: > > 2) Packets with a destination IP (DIP) address in the 224.0.0.X > range which are not IGMP must be forwarded on all ports. > > IGMP reports for local multicast groups can now be optionally > inhibited by means of a system control variable (by setting the value > to zero) e.g.: > echo 0 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > > To retain backwards compatibility the previous behaviour is retained > by default on system boot or reverted by setting the value back to > non-zero e.g.: > echo 1 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > > Signed-off-by: Philip Downey <pdowney@brocade.com> Applied to net-next, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Aug 27, 2015 at 8:46 AM, Philip Downey <pdowney@brocade.com> wrote: > IGMP reports for local multicast groups can now be optionally > inhibited by means of a system control variable (by setting the value > to zero) e.g.: > echo 0 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > > To retain backwards compatibility the previous behaviour is retained > by default on system boot or reverted by setting the value back to > non-zero e.g.: > echo 1 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > Please document it in Documentation/networking/ip-sysctl.txt. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> -----Original Message----- > From: Cong Wang [mailto:cwang@twopensource.com] > Sent: Friday, August 28, 2015 10:20 PM > To: Philip Downey > Cc: David Miller; Alexey Kuznetsov; James Morris; Hideaki YOSHIFUJI; Patrick > McHardy; linux-kernel@vger.kernel.org; netdev > Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups > > On Thu, Aug 27, 2015 at 8:46 AM, Philip Downey <pdowney@brocade.com> > wrote: > > IGMP reports for local multicast groups can now be optionally > > inhibited by means of a system control variable (by setting the value > > to zero) e.g.: > > echo 0 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > > > > To retain backwards compatibility the previous behaviour is retained > > by default on system boot or reverted by setting the value back to > > non-zero e.g.: > > echo 1 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > > > > Please document it in Documentation/networking/ip-sysctl.txt. Thanks for the comment. I have generated a new patch for the proposed documentation change. Hope this is the correct thing to do. Regards Philip
diff --git a/include/linux/igmp.h b/include/linux/igmp.h index 193ad48..9084292 100644 --- a/include/linux/igmp.h +++ b/include/linux/igmp.h @@ -37,6 +37,7 @@ static inline struct igmpv3_query * return (struct igmpv3_query *)skb_transport_header(skb); } +extern int sysctl_igmp_llm_reports; extern int sysctl_igmp_max_memberships; extern int sysctl_igmp_max_msf; extern int sysctl_igmp_qrv; diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index 9fdfd9d..d38b8b6 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -110,6 +110,9 @@ #define IP_MAX_MEMBERSHIPS 20 #define IP_MAX_MSF 10 +/* IGMP reports for link-local multicast groups are enabled by default */ +int sysctl_igmp_llm_reports __read_mostly = 1; + #ifdef CONFIG_IP_MULTICAST /* Parameter names and values are taken from igmp-v2-06 draft */ @@ -437,6 +440,8 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc, if (pmc->multiaddr == IGMP_ALL_HOSTS) return skb; + if (ipv4_is_local_multicast(pmc->multiaddr) && !sysctl_igmp_llm_reports) + return skb; isquery = type == IGMPV3_MODE_IS_INCLUDE || type == IGMPV3_MODE_IS_EXCLUDE; @@ -545,6 +550,9 @@ static int igmpv3_send_report(struct in_device *in_dev, struct ip_mc_list *pmc) for_each_pmc_rcu(in_dev, pmc) { if (pmc->multiaddr == IGMP_ALL_HOSTS) continue; + if (ipv4_is_local_multicast(pmc->multiaddr) && + !sysctl_igmp_llm_reports) + continue; spin_lock_bh(&pmc->lock); if (pmc->sfcount[MCAST_EXCLUDE]) type = IGMPV3_MODE_IS_EXCLUDE; @@ -678,7 +686,11 @@ static int igmp_send_report(struct in_device *in_dev, struct ip_mc_list *pmc, if (type == IGMPV3_HOST_MEMBERSHIP_REPORT) return igmpv3_send_report(in_dev, pmc); - else if (type == IGMP_HOST_LEAVE_MESSAGE) + + if (ipv4_is_local_multicast(group) && !sysctl_igmp_llm_reports) + return 0; + + if (type == IGMP_HOST_LEAVE_MESSAGE) dst = IGMP_ALL_ROUTER; else dst = group; @@ -851,6 +863,8 @@ static bool igmp_heard_report(struct in_device *in_dev, __be32 group) if (group == IGMP_ALL_HOSTS) return false; + if (ipv4_is_local_multicast(group) && !sysctl_igmp_llm_reports) + return false; rcu_read_lock(); for_each_pmc_rcu(in_dev, im) { @@ -957,6 +971,9 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb, continue; if (im->multiaddr == IGMP_ALL_HOSTS) continue; + if (ipv4_is_local_multicast(im->multiaddr) && + !sysctl_igmp_llm_reports) + continue; spin_lock_bh(&im->lock); if (im->tm_running) im->gsquery = im->gsquery && mark; @@ -1181,6 +1198,8 @@ static void igmp_group_dropped(struct ip_mc_list *im) #ifdef CONFIG_IP_MULTICAST if (im->multiaddr == IGMP_ALL_HOSTS) return; + if (ipv4_is_local_multicast(im->multiaddr) && !sysctl_igmp_llm_reports) + return; reporter = im->reporter; igmp_stop_timer(im); @@ -1213,6 +1232,8 @@ static void igmp_group_added(struct ip_mc_list *im) #ifdef CONFIG_IP_MULTICAST if (im->multiaddr == IGMP_ALL_HOSTS) return; + if (ipv4_is_local_multicast(im->multiaddr) && !sysctl_igmp_llm_reports) + return; if (in_dev->dead) return; @@ -1518,6 +1539,9 @@ static void ip_mc_rejoin_groups(struct in_device *in_dev) for_each_pmc_rtnl(in_dev, im) { if (im->multiaddr == IGMP_ALL_HOSTS) continue; + if (ipv4_is_local_multicast(im->multiaddr) && + !sysctl_igmp_llm_reports) + continue; /* a failover is happening and switches * must be notified immediately diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 0330ab2..74eede2 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -910,6 +910,13 @@ static struct ctl_table ipv4_net_table[] = { .mode = 0644, .proc_handler = proc_dointvec, }, + { + .procname = "igmp_link_local_mcast_reports", + .data = &sysctl_igmp_llm_reports, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec + }, { } };
The range of addresses between 224.0.0.0 and 224.0.0.255 inclusive, is reserved for the use of routing protocols and other low-level topology discovery or maintenance protocols, such as gateway discovery and group membership reporting. Multicast routers should not forward any multicast datagram with destination addresses in this range, regardless of its TTL. Currently, IGMP reports are generated for this reserved range of addresses even though a router will ignore this information since it has no purpose. However, the presence of reserved group addresses in an IGMP membership report uses up network bandwidth and can also obscure addresses of interest when inspecting membership reports using packet inspection or debug messages. Although the RFCs for the various version of IGMP (e.g.RFC 3376 for v3) do not specify that the reserved addresses be excluded from membership reports, it should do no harm in doing so. In particular there should be no adverse effect in any IGMP snooping functionality since 224.0.0.x is specifically excluded as per RFC 4541 (IGMP and MLD Snooping Switches Considerations) section 2.1.2. Data Forwarding Rules: 2) Packets with a destination IP (DIP) address in the 224.0.0.X range which are not IGMP must be forwarded on all ports. IGMP reports for local multicast groups can now be optionally inhibited by means of a system control variable (by setting the value to zero) e.g.: echo 0 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports To retain backwards compatibility the previous behaviour is retained by default on system boot or reverted by setting the value back to non-zero e.g.: echo 1 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports Signed-off-by: Philip Downey <pdowney@brocade.com> --- include/linux/igmp.h | 1 + net/ipv4/igmp.c | 26 +++++++++++++++++++++++++- net/ipv4/sysctl_net_ipv4.c | 7 +++++++ 3 files changed, 33 insertions(+), 1 deletion(-)