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Subject[PATCH net-next v2 3/4] bridge: join all-snoopers multicast address
Date
Next to snooping IGMP/MLD queries RFC4541, section 2.1.1.a) recommends
to snoop multicast router advertisements to detect multicast routers.

Multicast router advertisements are sent to an "all-snoopers"
multicast address. To be able to receive them reliably, we need to
join this group.

Otherwise other snooping switches might refrain from forwarding these
advertisements to us.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
---
include/uapi/linux/in.h | 9 +++---
net/bridge/br_multicast.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++-
net/ipv6/mcast.c | 2 ++
3 files changed, 78 insertions(+), 5 deletions(-)

diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h
index f6052e70bf40..7ab685cacb8f 100644
--- a/include/uapi/linux/in.h
+++ b/include/uapi/linux/in.h
@@ -292,10 +292,11 @@ struct sockaddr_in {
#define IN_LOOPBACK(a) ((((long int) (a)) & 0xff000000) == 0x7f000000)

/* Defines for Multicast INADDR */
-#define INADDR_UNSPEC_GROUP 0xe0000000U /* 224.0.0.0 */
-#define INADDR_ALLHOSTS_GROUP 0xe0000001U /* 224.0.0.1 */
-#define INADDR_ALLRTRS_GROUP 0xe0000002U /* 224.0.0.2 */
-#define INADDR_MAX_LOCAL_GROUP 0xe00000ffU /* 224.0.0.255 */
+#define INADDR_UNSPEC_GROUP 0xe0000000U /* 224.0.0.0 */
+#define INADDR_ALLHOSTS_GROUP 0xe0000001U /* 224.0.0.1 */
+#define INADDR_ALLRTRS_GROUP 0xe0000002U /* 224.0.0.2 */
+#define INADDR_ALLSNOOPERS_GROUP 0xe000006aU /* 224.0.0.106 */
+#define INADDR_MAX_LOCAL_GROUP 0xe00000ffU /* 224.0.0.255 */
#endif

/* <asm/byteorder.h> contains the htonl type stuff.. */
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 156c4905639e..2366f4a2780e 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1780,6 +1780,68 @@ void br_multicast_init(struct net_bridge *br)
INIT_HLIST_HEAD(&br->mdb_list);
}

+static void br_ip4_multicast_join_snoopers(struct net_bridge *br)
+{
+ struct in_device *in_dev = in_dev_get(br->dev);
+
+ if (!in_dev)
+ return;
+
+ ip_mc_inc_group(in_dev, htonl(INADDR_ALLSNOOPERS_GROUP));
+ in_dev_put(in_dev);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void br_ip6_multicast_join_snoopers(struct net_bridge *br)
+{
+ struct in6_addr addr;
+
+ ipv6_addr_set(&addr, htonl(0xff020000), 0, 0, htonl(0x6a));
+ ipv6_dev_mc_inc(br->dev, &addr);
+}
+#else
+static inline void br_ip6_multicast_join_snoopers(struct net_bridge *br)
+{
+}
+#endif
+
+static void br_multicast_join_snoopers(struct net_bridge *br)
+{
+ br_ip4_multicast_join_snoopers(br);
+ br_ip6_multicast_join_snoopers(br);
+}
+
+static void br_ip4_multicast_leave_snoopers(struct net_bridge *br)
+{
+ struct in_device *in_dev = in_dev_get(br->dev);
+
+ if (WARN_ON(!in_dev))
+ return;
+
+ ip_mc_dec_group(in_dev, htonl(INADDR_ALLSNOOPERS_GROUP));
+ in_dev_put(in_dev);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void br_ip6_multicast_leave_snoopers(struct net_bridge *br)
+{
+ struct in6_addr addr;
+
+ ipv6_addr_set(&addr, htonl(0xff020000), 0, 0, htonl(0x6a));
+ ipv6_dev_mc_dec(br->dev, &addr);
+}
+#else
+static inline void br_ip6_multicast_leave_snoopers(struct net_bridge *br)
+{
+}
+#endif
+
+static void br_multicast_leave_snoopers(struct net_bridge *br)
+{
+ br_ip4_multicast_leave_snoopers(br);
+ br_ip6_multicast_leave_snoopers(br);
+}
+
static void __br_multicast_open(struct net_bridge *br,
struct bridge_mcast_own_query *query)
{
@@ -1793,6 +1855,9 @@ static void __br_multicast_open(struct net_bridge *br,

void br_multicast_open(struct net_bridge *br)
{
+ if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
+ br_multicast_join_snoopers(br);
+
__br_multicast_open(br, &br->ip4_own_query);
#if IS_ENABLED(CONFIG_IPV6)
__br_multicast_open(br, &br->ip6_own_query);
@@ -1808,6 +1873,9 @@ void br_multicast_stop(struct net_bridge *br)
del_timer_sync(&br->ip6_other_query.timer);
del_timer_sync(&br->ip6_own_query.timer);
#endif
+
+ if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
+ br_multicast_leave_snoopers(br);
}

void br_multicast_dev_del(struct net_bridge *br)
@@ -1943,8 +2011,10 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val)

br_mc_disabled_update(br->dev, val);
br_opt_toggle(br, BROPT_MULTICAST_ENABLED, !!val);
- if (!br_opt_get(br, BROPT_MULTICAST_ENABLED))
+ if (!br_opt_get(br, BROPT_MULTICAST_ENABLED)) {
+ br_multicast_leave_snoopers(br);
goto unlock;
+ }

if (!netif_running(br->dev))
goto unlock;
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 21f6deb2aec9..42f3f5cd349f 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -940,6 +940,7 @@ int ipv6_dev_mc_inc(struct net_device *dev, const struct in6_addr *addr)
{
return __ipv6_dev_mc_inc(dev, addr, MCAST_EXCLUDE);
}
+EXPORT_SYMBOL(ipv6_dev_mc_inc);

/*
* device multicast group del
@@ -987,6 +988,7 @@ int ipv6_dev_mc_dec(struct net_device *dev, const struct in6_addr *addr)

return err;
}
+EXPORT_SYMBOL(ipv6_dev_mc_dec);

/*
* check if the interface/address pair is valid
--
2.11.0
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