[RFC PATCH] net: bridge: multicast: add support for L2 entries

From: Vladimir Oltean
Date: Sat Oct 17 2020 - 14:42:17 EST

From: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>

Extend the bridge multicast control and data path to configure routes
for L2 (non-IP) multicast groups.

The uapi struct br_mdb_entry union u is extended with another variant,
interpretation, mac_addr, which does not change the structure size, and
which is valid when the MDB_FLAGS_L2 flag is found set.

To be compatible with the forwarding code that is already in place,
which acts as an IGMP/MLD snooping bridge with querier capabilities, we
need to declare that for L2 MDB entries (for which there exists no such
thing as IGMP/MLD snooping/querying), that there is always a querier.
Otherwise, these entries would be flooded to all bridge ports and not
just to those that are members of the L2 multicast group.

Needless to say, only permanent L2 multicast groups can be installed on
a bridge port.

Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
This patch is adapted from the version that Nikolay posted here:
https://lore.kernel.org/netdev/20200708090454.zvb6o7jr2woirw3i@skbuf/

There, he marked the patch as "unfinished". I haven't made any major
modifications to it, but I've tested it and it appears to work ok,
including with offloading. Hence, I would appreciate some tips regarding
things that might be missing.

include/linux/if_bridge.h | 1 +
include/uapi/linux/if_bridge.h | 2 ++
net/bridge/br_device.c | 2 +-
net/bridge/br_input.c | 2 +-
net/bridge/br_mdb.c | 24 ++++++++++++++++++++----
net/bridge/br_multicast.c | 12 ++++++++++--
net/bridge/br_private.h | 7 +++++--
7 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index 556caed00258..b135ad714383 100644
--- a/include/linux/if_bridge.h
+++ b/include/linux/if_bridge.h
@@ -26,6 +26,7 @@ struct br_ip {
struct in6_addr ip6;
#endif
} dst;
+ unsigned char mac_addr[ETH_ALEN];
__be16 proto;
__u16 vid;
};
diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index 4c687686aa8f..a25f6f9aa8c3 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -520,12 +520,14 @@ struct br_mdb_entry {
#define MDB_FLAGS_FAST_LEAVE (1 << 1)
#define MDB_FLAGS_STAR_EXCL (1 << 2)
#define MDB_FLAGS_BLOCKED (1 << 3)
+#define MDB_FLAGS_L2 (1 << 5)
__u8 flags;
__u16 vid;
struct {
union {
__be32 ip4;
struct in6_addr ip6;
+ unsigned char mac_addr[ETH_ALEN];
} u;
__be16 proto;
} addr;
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 6f742fee874a..06c28753b911 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -93,7 +93,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)

mdst = br_mdb_get(br, skb, vid);
if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
- br_multicast_querier_exists(br, eth_hdr(skb)))
+ br_multicast_querier_exists(br, eth_hdr(skb), mdst))
br_multicast_flood(mdst, skb, false, true);
else
br_flood(br, skb, BR_PKT_MULTICAST, false, true);
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 59a318b9f646..d31b5c18c6a1 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -134,7 +134,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
case BR_PKT_MULTICAST:
mdst = br_mdb_get(br, skb, vid);
if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
- br_multicast_querier_exists(br, eth_hdr(skb))) {
+ br_multicast_querier_exists(br, eth_hdr(skb), mdst)) {
if ((mdst && mdst->host_joined) ||
br_multicast_is_router(br)) {
local_rcv = true;
diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index e15bab19a012..4decf3eb7001 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -66,6 +66,8 @@ static void __mdb_entry_fill_flags(struct br_mdb_entry *e, unsigned char flags)
e->flags |= MDB_FLAGS_STAR_EXCL;
if (flags & MDB_PG_FLAGS_BLOCKED)
e->flags |= MDB_FLAGS_BLOCKED;
+ if (flags & MDB_PG_FLAGS_L2)
+ e->flags |= MDB_FLAGS_L2;
}

static void __mdb_entry_to_br_ip(struct br_mdb_entry *entry, struct br_ip *ip,
@@ -87,6 +89,8 @@ static void __mdb_entry_to_br_ip(struct br_mdb_entry *entry, struct br_ip *ip,
ip->src.ip6 = nla_get_in6_addr(mdb_attrs[MDBE_ATTR_SOURCE]);
break;
#endif
+ default:
+ ether_addr_copy(ip->mac_addr, entry->addr.u.mac_addr);
}

}
@@ -174,9 +178,11 @@ static int __mdb_fill_info(struct sk_buff *skb,
if (mp->addr.proto == htons(ETH_P_IP))
e.addr.u.ip4 = mp->addr.dst.ip4;
#if IS_ENABLED(CONFIG_IPV6)
- if (mp->addr.proto == htons(ETH_P_IPV6))
+ else if (mp->addr.proto == htons(ETH_P_IPV6))
e.addr.u.ip6 = mp->addr.dst.ip6;
#endif
+ else
+ ether_addr_copy(e.addr.u.mac_addr, mp->addr.mac_addr);
e.addr.proto = mp->addr.proto;
nest_ent = nla_nest_start_noflag(skb,
MDBA_MDB_ENTRY_INFO);
@@ -210,6 +216,8 @@ static int __mdb_fill_info(struct sk_buff *skb,
}
break;
#endif
+ default:
+ ether_addr_copy(e.addr.u.mac_addr, mp->addr.mac_addr);
}
if (p) {
if (nla_put_u8(skb, MDBA_MDB_EATTR_RTPROT, p->rt_protocol))
@@ -562,9 +570,12 @@ void br_mdb_notify(struct net_device *dev,
if (mp->addr.proto == htons(ETH_P_IP))
ip_eth_mc_map(mp->addr.dst.ip4, mdb.addr);
#if IS_ENABLED(CONFIG_IPV6)
- else
+ else if (mp->addr.proto == htons(ETH_P_IPV6))
ipv6_eth_mc_map(&mp->addr.dst.ip6, mdb.addr);
#endif
+ else
+ ether_addr_copy(mdb.addr, mp->addr.mac_addr);
+
mdb.obj.orig_dev = pg->key.port->dev;
switch (type) {
case RTM_NEWMDB:
@@ -693,7 +704,7 @@ static bool is_valid_mdb_entry(struct br_mdb_entry *entry,
return false;
}
#endif
- } else {
+ } else if (entry->addr.proto != 0) {
NL_SET_ERR_MSG_MOD(extack, "Unknown entry protocol");
return false;
}
@@ -857,6 +868,11 @@ static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
return err;
}

+ if (entry->state != MDB_PERMANENT && mp->l2) {
+ NL_SET_ERR_MSG_MOD(extack, "Only permanent L2 entries allowed");
+ return -EINVAL;
+ }
+
/* host join */
if (!port) {
if (mp->host_joined) {
@@ -891,7 +907,7 @@ static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
return -ENOMEM;
}
rcu_assign_pointer(*pp, p);
- if (entry->state == MDB_TEMPORARY)
+ if (entry->state == MDB_TEMPORARY && !mp->l2)
mod_timer(&p->timer, now + br->multicast_membership_interval);
br_mdb_notify(br->dev, mp, p, RTM_NEWMDB);
/* if we are adding a new EXCLUDE port group (*,G) it needs to be also
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index eae898c3cff7..bc03057e7caf 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -179,7 +179,8 @@ struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
break;
#endif
default:
- return NULL;
+ ip.proto = 0;
+ ether_addr_copy(ip.mac_addr, eth_hdr(skb)->h_dest);
}

return br_mdb_ip_get_rcu(br, &ip);
@@ -1050,6 +1051,7 @@ struct net_bridge_mdb_entry *br_multicast_new_group(struct net_bridge *br,

mp->br = br;
mp->addr = *group;
+ mp->l2 = !!(group->proto == 0);
mp->mcast_gc.destroy = br_multicast_destroy_mdb_entry;
timer_setup(&mp->timer, br_multicast_group_expired, 0);
err = rhashtable_lookup_insert_fast(&br->mdb_hash_tbl, &mp->rhnode,
@@ -1169,6 +1171,8 @@ struct net_bridge_port_group *br_multicast_new_port_group(
p->key.addr = *group;
p->key.port = port;
p->flags = flags;
+ if (group->proto == htons(0))
+ p->flags |= MDB_PG_FLAGS_L2;
p->filter_mode = filter_mode;
p->rt_protocol = rt_protocol;
p->mcast_gc.destroy = br_multicast_destroy_port_group;
@@ -1203,6 +1207,10 @@ void br_multicast_host_join(struct net_bridge_mdb_entry *mp, bool notify)
if (notify)
br_mdb_notify(mp->br->dev, mp, NULL, RTM_NEWMDB);
}
+
+ if (mp->l2)
+ return;
+
mod_timer(&mp->timer, jiffies + mp->br->multicast_membership_interval);
}

@@ -3690,7 +3698,7 @@ bool br_multicast_has_querier_anywhere(struct net_device *dev, int proto)
memset(&eth, 0, sizeof(eth));
eth.h_proto = htons(proto);

- ret = br_multicast_querier_exists(br, &eth);
+ ret = br_multicast_querier_exists(br, &eth, NULL);

unlock:
rcu_read_unlock();
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 345118e35c42..63a98c1af351 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -215,6 +215,7 @@ struct net_bridge_fdb_entry {
#define MDB_PG_FLAGS_FAST_LEAVE BIT(2)
#define MDB_PG_FLAGS_STAR_EXCL BIT(3)
#define MDB_PG_FLAGS_BLOCKED BIT(4)
+#define MDB_PG_FLAGS_L2 BIT(5)

#define PG_SRC_ENT_LIMIT 32

@@ -272,6 +273,7 @@ struct net_bridge_mdb_entry {
struct net_bridge_port_group __rcu *ports;
struct br_ip addr;
bool host_joined;
+ bool l2;

struct timer_list timer;
struct hlist_node mdb_node;
@@ -871,7 +873,8 @@ __br_multicast_querier_exists(struct net_bridge *br,
}

static inline bool br_multicast_querier_exists(struct net_bridge *br,
- struct ethhdr *eth)
+ struct ethhdr *eth,
+ const struct net_bridge_mdb_entry *mdb)
{
switch (eth->h_proto) {
case (htons(ETH_P_IP)):
@@ -883,7 +886,7 @@ static inline bool br_multicast_querier_exists(struct net_bridge *br,
&br->ip6_other_query, true);
#endif
default:
- return false;
+ return !!(mdb && mdb->l2);
}
}

--
2.25.1