RE: [PATCH] IGMP: Inhibit reports for local multicast groups
> -Original Message- > From: Cong Wang [mailto:cw...@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-ker...@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 <pdow...@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
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
On Thu, Aug 27, 2015 at 8:46 AM, Philip Downey pdow...@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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
From: Philip Downey pdow...@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 pdow...@brocade.com Applied to net-next, thanks. -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] 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 pdow...@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(-)
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
RE: [PATCH] IGMP: Inhibit reports for local multicast groups
-Original Message- From: David Miller [mailto:da...@davemloft.net] Sent: Tuesday, August 25, 2015 10:20 PM To: Philip Downey Cc: kuz...@ms2.inr.ac.ru; jmor...@namei.org; yoshf...@linux-ipv6.org; ka...@trash.net; linux-ker...@vger.kernel.org; netdev@vger.kernel.org Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups From: Philip Downey pdow...@brocade.com Date: Mon, 24 Aug 2015 12:39:17 +0100 +extern int sysctl_igmp_link_local_reports; ... +/* IGMP reports for link-local multicast groups are enabled by default */ +#define IGMP_ENABLE_LLM 1 + +int sysctl_igmp_link_local_reports __read_mostly = IGMP_ENABLE_LLM; + +#define IGMP_INHIBIT_LINK_LOCAL_REPORTS(_ipaddr) \ + (ipv4_is_local_multicast(_ipaddr) \ +(sysctl_igmp_link_local_reports == 0)) + People know that 1 and 0 means enable and disable respectively, so this macros is pretty excessive. Just remove it. Also, simplify the name of the sysctl to something like sysctl_igmp_llm_reports or similar, and simplify the test against 0 to be in the canonical !x format. Then the test can fit on one line: (ipv4_is_local_multicast(_ipaddr) !sysctl_igmp_llm_reports). Thanks for reviewing David. I will make the requested changes (fitting the test on a single line was my main reason for introducing the macro - that and making it patently obvious what the test was doing. Your suggestion would seem to meet that aim). Will amend and resubmit. Regards Philip -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
From: Philip Downey pdow...@brocade.com Date: Mon, 24 Aug 2015 12:39:17 +0100 +extern int sysctl_igmp_link_local_reports; ... +/* IGMP reports for link-local multicast groups are enabled by default */ +#define IGMP_ENABLE_LLM 1 + +int sysctl_igmp_link_local_reports __read_mostly = IGMP_ENABLE_LLM; + +#define IGMP_INHIBIT_LINK_LOCAL_REPORTS(_ipaddr) \ + (ipv4_is_local_multicast(_ipaddr) \ + (sysctl_igmp_link_local_reports == 0)) + People know that 1 and 0 means enable and disable respectively, so this macros is pretty excessive. Just remove it. Also, simplify the name of the sysctl to something like sysctl_igmp_llm_reports or similar, and simplify the test against 0 to be in the canonical !x format. Then the test can fit on one line: (ipv4_is_local_multicast(_ipaddr) !sysctl_igmp_llm_reports) -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] 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_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_reports
Signed-off-by: Philip Downey pdow...@brocade.com
---
include/linux/igmp.h |1 +
net/ipv4/igmp.c| 29 -
net/ipv4/sysctl_net_ipv4.c |7 +++
3 files changed, 36 insertions(+), 1 deletion(-)
diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 193ad48..e3e0dae 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_link_local_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..a3df89d 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -110,6 +110,15 @@
#define IP_MAX_MEMBERSHIPS 20
#define IP_MAX_MSF 10
+/* IGMP reports for link-local multicast groups are enabled by default */
+#define IGMP_ENABLE_LLM 1
+
+int sysctl_igmp_link_local_reports __read_mostly = IGMP_ENABLE_LLM;
+
+#define IGMP_INHIBIT_LINK_LOCAL_REPORTS(_ipaddr) \
+ (ipv4_is_local_multicast(_ipaddr) \
+(sysctl_igmp_link_local_reports == 0))
+
#ifdef CONFIG_IP_MULTICAST
/* Parameter names and values are taken from igmp-v2-06 draft */
@@ -437,6 +446,8 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct
ip_mc_list *pmc,
if (pmc-multiaddr == IGMP_ALL_HOSTS)
return skb;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(pmc-multiaddr))
+ return skb;
isquery = type == IGMPV3_MODE_IS_INCLUDE ||
type == IGMPV3_MODE_IS_EXCLUDE;
@@ -545,6 +556,8 @@ 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 (IGMP_INHIBIT_LINK_LOCAL_REPORTS(pmc-multiaddr))
+ continue;
spin_lock_bh(pmc-lock);
if (pmc-sfcount[MCAST_EXCLUDE])
type = IGMPV3_MODE_IS_EXCLUDE;
@@ -678,7 +691,11 @@ 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 (IGMP_INHIBIT_LINK_LOCAL_REPORTS(group))
+ return 0;
+
+ if (type == IGMP_HOST_LEAVE_MESSAGE)
dst = IGMP_ALL_ROUTER;
else
dst = group;
@@ -851,6 +868,8 @@ static bool igmp_heard_report(struct in_device *in_dev,
__be32 group)
if (group == IGMP_ALL_HOSTS)
return false;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(group))
+ return false;
rcu_read_lock();
for_each_pmc_rcu(in_dev, im) {
@@ -957,6 +976,8 @@ static bool igmp_heard_query(struct in_device *in_dev,
struct sk_buff *skb,
continue;
if (im-multiaddr == IGMP_ALL_HOSTS)
continue;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(im-multiaddr))
+ continue;
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
Hi Philip So with a bit of poking and prodding, we have a much better understanding as to why this is O.K. Maybe your next patch can quote the relevant RFCs and have a much fuller commit message? Thanks Andrew -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH] IGMP: Inhibit reports for local multicast groups
Sorry for the duplication - I responded in a similar manner before seeing this. Thanks Philip -Original Message- From: Thadeu Lima de Souza Cascardo [mailto:casca...@redhat.com] Sent: Thursday, August 13, 2015 7:08 PM To: Andrew Lunn Cc: Philip Downey; David Miller; kuz...@ms2.inr.ac.ru; jmor...@namei.org; yoshf...@linux-ipv6.org; ka...@trash.net; linux-ker...@vger.kernel.org; netdev@vger.kernel.org Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups On Thu, Aug 13, 2015 at 07:01:37PM +0200, Andrew Lunn wrote: On Thu, Aug 13, 2015 at 04:52:32PM +, Philip Downey wrote: Hi Andrew IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined. Link- Local multicast traffic should not have an IGMP client since it is reserved for routing protocols. One would expect that IGMP snooping needs to ignore local multicast traffic in the reserved range intended for routers since there should be no IGMP client to make join requests. The point of this patch is that Linux is sending out group membership for these addresses, it is acting as a client. What happens with a switch which is applying IGMP snooping to link-local multicast groups? You turn on this feature, and you no longer get your routing protocol messages. I had a quick look at RFC 3376. The only mention i spotted for not sending IGMP messages is: The all-systems multicast address, 224.0.0.1, is handled as a special case. On all systems -- that is all hosts and routers, including multicast routers -- reception of packets destined to the all-systems multicast address, from all sources, is permanently enabled on all interfaces on which multicast reception is supported. No IGMP messages are ever sent regarding the all-systems multicast address. IGMP v2 has something similar: The all-systems group (address 224.0.0.1) is handled as a special case. The host starts in Idle Member state for that group on every interface, never transitions to another state, and never sends a report for that group. But i did not find anything which says all other link-local addresses don't need member reports. Did i miss something? Andrew From RFC 4541 (Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches): 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. This recommendation is based on the fact that many host systems do not send Join IP multicast addresses in this range before sending or listening to IP multicast packets. Furthermore, since the 224.0.0.X address range is defined as link-local (not to be routed), it seems unnecessary to keep the state for each address in this range. Additionally, some routers operate in the 224.0.0.X address range without issuing IGMP Joins, and these applications would break if the switch were to prune them due to not having seen a Join Group message from the router. So, it looks like some hosts and routers out there in the field do not send joins for those local addresses. In fact, IPv4 local multicast addresses are ignored when Linux bridge multicast snooping adds a new group. static int br_ip4_multicast_add_group(struct net_bridge *br, ... if (ipv4_is_local_multicast(group)) return 0; Cascardo. -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH] IGMP: Inhibit reports for local multicast groups
Hi Andrew Answers inline... -Original Message- From: Andrew Lunn [mailto:and...@lunn.ch] Sent: Thursday, August 13, 2015 6:02 PM To: Philip Downey Cc: David Miller; kuz...@ms2.inr.ac.ru; jmor...@namei.org; yoshfuji@linux- ipv6.org; ka...@trash.net; linux-ker...@vger.kernel.org; netdev@vger.kernel.org Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups On Thu, Aug 13, 2015 at 04:52:32PM +, Philip Downey wrote: Hi Andrew IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined. Link- Local multicast traffic should not have an IGMP client since it is reserved for routing protocols. One would expect that IGMP snooping needs to ignore local multicast traffic in the reserved range intended for routers since there should be no IGMP client to make join requests. The point of this patch is that Linux is sending out group membership for these addresses, it is acting as a client. What happens with a switch which is applying IGMP snooping to link-local multicast groups? You turn on this feature, and you no longer get your routing protocol messages. It is expected that link-local multicast is always forwarded by switches otherwise routers may not function correctly. From the relevant RFC: RFC 4541 IGMP and MLD Snooping Switches Considerations May 2006 2.1.2. Data Forwarding Rules 1) Packets with a destination IP address outside 224.0.0.X which are not IGMP should be forwarded according to group-based port membership tables and must also be forwarded on router ports. This is the main IGMP snooping functionality for the data path. One approach that an implementation could take would be to maintain separate membership and multicast router tables in software and then merge these tables into a forwarding cache. 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. This recommendation is based on the fact that many host systems do not send Join IP multicast addresses in this range before sending or listening to IP multicast packets. Furthermore, since the 224.0.0.X address range is defined as link-local (not to be routed), it seems unnecessary to keep the state for each address in this range. Additionally, some routers operate in the 224.0.0.X address range without issuing IGMP Joins, and these applications would break if the switch were to prune them due to not having seen a Join Group message from the router. I had a quick look at RFC 3376. The only mention i spotted for not sending IGMP messages is: The all-systems multicast address, 224.0.0.1, is handled as a special case. On all systems -- that is all hosts and routers, including multicast routers -- reception of packets destined to the all-systems multicast address, from all sources, is permanently enabled on all interfaces on which multicast reception is supported. No IGMP messages are ever sent regarding the all-systems multicast address. IGMP v2 has something similar: The all-systems group (address 224.0.0.1) is handled as a special case. The host starts in Idle Member state for that group on every interface, never transitions to another state, and never sends a report for that group. But i did not find anything which says all other link-local addresses don't need member reports. Did i miss something? No you did not miss anything - that is correct. However, the RFCs don't really cover the behavior of routers well in some areas. Routing protocols which use the 224.0.0.x address space do not need IGMP therefore it makes no sense to distribute membership reports for these groups. A router which receives an IGMP membership report which includes groups from this reserved address range will ignore it -and probably generate debug messages highlighting an invalid address. Regards Philip Andrew -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH] IGMP: Inhibit reports for local multicast groups
Hi Andrew Will resubmit with the information you suggest. There might be a slight delay for this as I am on holiday now for a week. Rest regards Philip -Original Message- From: Andrew Lunn [mailto:and...@lunn.ch] Sent: Friday, August 14, 2015 2:35 PM To: Philip Downey Cc: David Miller; kuz...@ms2.inr.ac.ru; jmor...@namei.org; yoshfuji@linux- ipv6.org; ka...@trash.net; linux-ker...@vger.kernel.org; netdev@vger.kernel.org Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups Hi Philip So with a bit of poking and prodding, we have a much better understanding as to why this is O.K. Maybe your next patch can quote the relevant RFCs and have a much fuller commit message? Thanks Andrew -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH] IGMP: Inhibit reports for local multicast groups
Hi David Thanks for taking the time to review and comment. This is my first upstream request so please forgive any ignorance on my part. I have added a new proposed commit wording below with a view to agreeing the content before resubmitting the patch. I hope it is sufficient to address your concerns. 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. IGMP reports for local multicast groups can now be inhibited by means of a system control variable (setting the value to zero). To retain backwards compatibility the previous behaviour is retained by default on system boot. Signed-off-by: Philip Downey pdow...@brocade.com Regards Philip -Original Message- From: David Miller [mailto:da...@davemloft.net] Sent: Thursday, August 13, 2015 12:45 AM To: Philip Downey Cc: kuz...@ms2.inr.ac.ru; jmor...@namei.org; yoshf...@linux-ipv6.org; ka...@trash.net; linux-ker...@vger.kernel.org; netdev@vger.kernel.org Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups From: Philip Downey pdow...@brocade.com Date: Wed, 12 Aug 2015 17:13:53 +0100 IGMP reports are generated for link local multicast groups (224.0.0.1 - 224.0.0.255) used by the routing protocols such as RIP, OSPF etc. In general routers do not generate reports for local multicast groups. IGMP reports for local multicast groups can now be inhibited by means of a system control variable (setting the value to zero). To retain backwards compatibility the previous behaviour is retained by default on system boot. Signed-off-by: Philip Downey pdow...@brocade.com I'm always hesitent to apply patches like this. I can't even understand from your explanation: 1) what about local reporting behavior is so bad 2) why you want to inhibit them at all For example, this: In general routers do not generate reports for local multicast groups. Doesn't tell me anything. You need to go into more detail about this, and explain the situation sufficiently. -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH] IGMP: Inhibit reports for local multicast groups
Hi Andrew IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined. Link-Local multicast traffic should not have an IGMP client since it is reserved for routing protocols. One would expect that IGMP snooping needs to ignore local multicast traffic in the reserved range intended for routers since there should be no IGMP client to make join requests. Regards Philip -Original Message- From: Andrew Lunn [mailto:and...@lunn.ch] Sent: Thursday, August 13, 2015 5:06 PM To: Philip Downey Cc: David Miller; kuz...@ms2.inr.ac.ru; jmor...@namei.org; yoshfuji@linux- ipv6.org; ka...@trash.net; linux-ker...@vger.kernel.org; netdev@vger.kernel.org Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups On Thu, Aug 13, 2015 at 02:48:23PM +, Philip Downey wrote: Hi David Thanks for taking the time to review and comment. This is my first upstream request so please forgive any ignorance on my part. I have added a new proposed commit wording below with a view to agreeing the content before resubmitting the patch. I hope it is sufficient to address your concerns. 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. Hi Philip What about switches which are doing IGMP snooping? Andrew -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
On Thu, Aug 13, 2015 at 04:52:32PM +, Philip Downey wrote: Hi Andrew IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined. Link-Local multicast traffic should not have an IGMP client since it is reserved for routing protocols. One would expect that IGMP snooping needs to ignore local multicast traffic in the reserved range intended for routers since there should be no IGMP client to make join requests. The point of this patch is that Linux is sending out group membership for these addresses, it is acting as a client. What happens with a switch which is applying IGMP snooping to link-local multicast groups? You turn on this feature, and you no longer get your routing protocol messages. I had a quick look at RFC 3376. The only mention i spotted for not sending IGMP messages is: The all-systems multicast address, 224.0.0.1, is handled as a special case. On all systems -- that is all hosts and routers, including multicast routers -- reception of packets destined to the all-systems multicast address, from all sources, is permanently enabled on all interfaces on which multicast reception is supported. No IGMP messages are ever sent regarding the all-systems multicast address. IGMP v2 has something similar: The all-systems group (address 224.0.0.1) is handled as a special case. The host starts in Idle Member state for that group on every interface, never transitions to another state, and never sends a report for that group. But i did not find anything which says all other link-local addresses don't need member reports. Did i miss something? Andrew -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
On Thu, Aug 13, 2015 at 07:01:37PM +0200, Andrew Lunn wrote: On Thu, Aug 13, 2015 at 04:52:32PM +, Philip Downey wrote: Hi Andrew IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined. Link-Local multicast traffic should not have an IGMP client since it is reserved for routing protocols. One would expect that IGMP snooping needs to ignore local multicast traffic in the reserved range intended for routers since there should be no IGMP client to make join requests. The point of this patch is that Linux is sending out group membership for these addresses, it is acting as a client. What happens with a switch which is applying IGMP snooping to link-local multicast groups? You turn on this feature, and you no longer get your routing protocol messages. I had a quick look at RFC 3376. The only mention i spotted for not sending IGMP messages is: The all-systems multicast address, 224.0.0.1, is handled as a special case. On all systems -- that is all hosts and routers, including multicast routers -- reception of packets destined to the all-systems multicast address, from all sources, is permanently enabled on all interfaces on which multicast reception is supported. No IGMP messages are ever sent regarding the all-systems multicast address. IGMP v2 has something similar: The all-systems group (address 224.0.0.1) is handled as a special case. The host starts in Idle Member state for that group on every interface, never transitions to another state, and never sends a report for that group. But i did not find anything which says all other link-local addresses don't need member reports. Did i miss something? Andrew From RFC 4541 (Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches): 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. This recommendation is based on the fact that many host systems do not send Join IP multicast addresses in this range before sending or listening to IP multicast packets. Furthermore, since the 224.0.0.X address range is defined as link-local (not to be routed), it seems unnecessary to keep the state for each address in this range. Additionally, some routers operate in the 224.0.0.X address range without issuing IGMP Joins, and these applications would break if the switch were to prune them due to not having seen a Join Group message from the router. So, it looks like some hosts and routers out there in the field do not send joins for those local addresses. In fact, IPv4 local multicast addresses are ignored when Linux bridge multicast snooping adds a new group. static int br_ip4_multicast_add_group(struct net_bridge *br, ... if (ipv4_is_local_multicast(group)) return 0; Cascardo. -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
On Thu, Aug 13, 2015 at 02:48:23PM +, Philip Downey wrote: Hi David Thanks for taking the time to review and comment. This is my first upstream request so please forgive any ignorance on my part. I have added a new proposed commit wording below with a view to agreeing the content before resubmitting the patch. I hope it is sufficient to address your concerns. 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. Hi Philip What about switches which are doing IGMP snooping? Andrew -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] IGMP: Inhibit reports for local multicast groups
From: Philip Downey pdow...@brocade.com Date: Wed, 12 Aug 2015 17:13:53 +0100 IGMP reports are generated for link local multicast groups (224.0.0.1 - 224.0.0.255) used by the routing protocols such as RIP, OSPF etc. In general routers do not generate reports for local multicast groups. IGMP reports for local multicast groups can now be inhibited by means of a system control variable (setting the value to zero). To retain backwards compatibility the previous behaviour is retained by default on system boot. Signed-off-by: Philip Downey pdow...@brocade.com I'm always hesitent to apply patches like this. I can't even understand from your explanation: 1) what about local reporting behavior is so bad 2) why you want to inhibit them at all For example, this: In general routers do not generate reports for local multicast groups. Doesn't tell me anything. You need to go into more detail about this, and explain the situation sufficiently. -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] IGMP: Inhibit reports for local multicast groups
IGMP reports are generated for link local multicast groups (224.0.0.1
- 224.0.0.255) used by the routing protocols such as RIP, OSPF etc.
In general routers do not generate reports for local multicast groups.
IGMP reports for local multicast groups can now be inhibited by means
of a system control variable (setting the value to zero).
To retain backwards compatibility the previous behaviour is retained by
default on system boot.
Signed-off-by: Philip Downey pdow...@brocade.com
---
include/linux/igmp.h |1 +
net/ipv4/igmp.c| 29 -
net/ipv4/sysctl_net_ipv4.c |7 +++
3 files changed, 36 insertions(+), 1 deletion(-)
diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 193ad48..e3e0dae 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_link_local_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 651cdf6..2e4d5b8 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -110,6 +110,15 @@
#define IP_MAX_MEMBERSHIPS 20
#define IP_MAX_MSF 10
+/* IGMP reports for link-local multicast groups are enabled by default */
+#define IGMP_ENABLE_LLM 1
+
+int sysctl_igmp_link_local_reports __read_mostly = IGMP_ENABLE_LLM;
+
+#define IGMP_INHIBIT_LINK_LOCAL_REPORTS(_ipaddr) \
+ (ipv4_is_local_multicast(_ipaddr) \
+(sysctl_igmp_link_local_reports == 0))
+
#ifdef CONFIG_IP_MULTICAST
/* Parameter names and values are taken from igmp-v2-06 draft */
@@ -437,6 +446,8 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct
ip_mc_list *pmc,
if (pmc-multiaddr == IGMP_ALL_HOSTS)
return skb;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(pmc-multiaddr))
+ return skb;
isquery = type == IGMPV3_MODE_IS_INCLUDE ||
type == IGMPV3_MODE_IS_EXCLUDE;
@@ -545,6 +556,8 @@ 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 (IGMP_INHIBIT_LINK_LOCAL_REPORTS(pmc-multiaddr))
+ continue;
spin_lock_bh(pmc-lock);
if (pmc-sfcount[MCAST_EXCLUDE])
type = IGMPV3_MODE_IS_EXCLUDE;
@@ -678,7 +691,11 @@ 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 (IGMP_INHIBIT_LINK_LOCAL_REPORTS(group))
+ return 0;
+
+ if (type == IGMP_HOST_LEAVE_MESSAGE)
dst = IGMP_ALL_ROUTER;
else
dst = group;
@@ -851,6 +868,8 @@ static bool igmp_heard_report(struct in_device *in_dev,
__be32 group)
if (group == IGMP_ALL_HOSTS)
return false;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(group))
+ return false;
rcu_read_lock();
for_each_pmc_rcu(in_dev, im) {
@@ -957,6 +976,8 @@ static bool igmp_heard_query(struct in_device *in_dev,
struct sk_buff *skb,
continue;
if (im-multiaddr == IGMP_ALL_HOSTS)
continue;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(im-multiaddr))
+ continue;
spin_lock_bh(im-lock);
if (im-tm_running)
im-gsquery = im-gsquery mark;
@@ -1181,6 +1202,8 @@ static void igmp_group_dropped(struct ip_mc_list *im)
#ifdef CONFIG_IP_MULTICAST
if (im-multiaddr == IGMP_ALL_HOSTS)
return;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(im-multiaddr))
+ return;
reporter = im-reporter;
igmp_stop_timer(im);
@@ -1213,6 +1236,8 @@ static void igmp_group_added(struct ip_mc_list *im)
#ifdef CONFIG_IP_MULTICAST
if (im-multiaddr == IGMP_ALL_HOSTS)
return;
+ if (IGMP_INHIBIT_LINK_LOCAL_REPORTS(im-multiaddr))
+ return;
if (in_dev-dead)
return;
@@ -1515,6 +1540,8 @@ 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 (IGMP_INHIBIT_LINK_LOCAL_REPORTS(im-multiaddr))
+ 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 433231c..e7fd509 100644
---
