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authorPhilip Downey <pdowney@brocade.com>2015-08-27 16:46:26 +0100
committerDavid S. Miller <davem@davemloft.net>2015-08-28 13:28:47 -0700
commitdf2cf4a78e488d26728590cb3c6b4fe4c4862c77 (patch)
treeab8481b26180c4ac66ea6321e27c0cbdca16f842
parentr8169: Add software counter for multicast packages (diff)
downloadlinux-dev-df2cf4a78e488d26728590cb3c6b4fe4c4862c77.tar.xz
linux-dev-df2cf4a78e488d26728590cb3c6b4fe4c4862c77.zip
IGMP: Inhibit reports for local multicast groups
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> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/igmp.h1
-rw-r--r--net/ipv4/igmp.c26
-rw-r--r--net/ipv4/sysctl_net_ipv4.c7
3 files changed, 33 insertions, 1 deletions
diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 193ad488d3e2..908429216d9f 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 9fdfd9deac11..d38b8b61eaee 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 879bdc5c95b1..894da3a70aff 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -929,6 +929,13 @@ 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
+ },
{ }
};