[RFC incomplete] net: bridge: mdb: Extend with multicast LLADDR

[Horatiu Vultur]

Based on the discussion on the topic[1], we extend the functionality of
the 'bridge mdb' command to accept link layer multicast address. This
required only few changes and it fits nicely with the current
implementation and also the old implementation was not changed.

In this patch, we have added a MAC address to the union in 'struct br_ip'.
If we want to continue like this we should properly rename the structure as
it is not an IP any more.

To create a group for two of the front ports the following entries can
be added:
bridge mdb add dev br0 port eth0 grp 01:00:00:00:00:04 permanent vid 1
bridge mdb add dev br0 port eth1 grp 01:00:00:00:00:04 permanent vid 1

Now the entries will be display as following:
dev br0 port eth0 grp 01:00:00:00:00:04 permanent offload vid 1
dev br0 port eth1 grp 01:00:00:00:00:04 permanent offload vid 1

This requires changes to iproute2 as well, see the follogin patch for that.

Now if frame with dmac '01:00:00:00:00:04' will arrive at one of the front
ports. If we have HW offload support, then the frame will be forwarded by
the switch, and need not to go to the CPU. In a pure SW world, the frame is
forwarded by the SW bridge, which will flooded it only the ports which are
part of the group.

So far so good. This is an important part of the problem we wanted to solve.

But, there is one drawback of this approach. If you want to add two of the
front ports and br0 to receive the frame then I can't see a way of doing it
with the bridge mdb command. To do that it requireds many more changes to
the existing code.

Example:
bridge mdb add dev br0 port eth0 grp 01:00:00:00:00:04 permanent vid 1
bridge mdb add dev br0 port eth1 grp 01:00:00:00:00:04 permanent vid 1
bridge mdb add dev br0 port br0 grp 01:00:00:00:00:04 permanent vid 1 // This looks wrong.

We believe we come a long way by re-using the facilities in MDB (thanks for
convincing us in doing this), but we are still not completely happy with
the result.

If I only look at the user-interface (iproute2), and completely ignore all
the implementation details, then I still think that the FDB sub command is
more suitable for this. Today, FDB is for unicast, and MDB is for multicast.
We could change this such that MDB is for IP-multicast, and FDB is
forwarding in general (we should prevent FDB in install IP-multicast rules,
but we suggest to allow it to install MAC-Multicast rules).

The example from above would now look like this:
bridge fdb add 01:00:00:00:00:04 dev eth0 static self master
bridge fdb add 01:00:00:00:00:04 dev eth1 static self master
bridge fdb add 01:00:00:00:00:04 dev br0 static self master

It would be very similar to the "bridge vlan" command which also allow to
specify groups with and without br0.

Next observation is on the hashing data structure. In 'net_bridge_mdb_entry'
we only use/need the net_bridge_port_group/ports member (and the MAC
address, which we hacked into the br_ip struct) when we are a L2-multicast
entry. This type allow use to re-use the br_multicast_flood function
which does a lot of the work for us.

Also, the key used to do the lookup in the FDB is already a MAC address
(no need to hack the br_ip).

Regarding the events generated by switchdev: In the current proposal this
is a SWITCHDEV_OBJ_ID_PORT_MDB which refer to the switchdev_obj_port_mdb
type. If we changed to use the SWITCHDEV_FDB_ADD_TO_BRIDGE event, then
the associated data type would be switchdev_notifier_fdb_info - which also
has the information we need.

Using the FDB database, can still reuse the net_bridge_port_group type (and
associated functions), and I other parts from the MDB call graph as well.

If this sounds appealing, then we can do a proposal based on the idea.

If the MDB patch is what we can agree on, then we will continue polish this
and look for a solution to control the inclusion/exclusion of the br0
device (hints will be most appreciated).

[1] https://patchwork.ozlabs.org/patch/1136878/

Signed-off-by: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
Co-developed-by: Allan W. Nielsen <allan.nielsen@xxxxxxxxxxxxx>
Signed-off-by: Allan W. Nielsen <allan.nielsen@xxxxxxxxxxxxx>
---
 include/linux/if_bridge.h      |  1 +
 include/uapi/linux/if_bridge.h |  1 +
 net/bridge/br_device.c         |  7 +++--
 net/bridge/br_forward.c        |  3 ++-
 net/bridge/br_input.c          | 13 ++++++++--
 net/bridge/br_mdb.c            | 47 ++++++++++++++++++++++++++++------
 net/bridge/br_multicast.c      |  4 ++-
 net/bridge/br_private.h        |  3 ++-
 8 files changed, 64 insertions(+), 15 deletions(-)

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index 9e57c4411734..68f2558b1a23 100644
--- a/include/linux/if_bridge.h
+++ b/include/linux/if_bridge.h
@@ -16,6 +16,7 @@
 struct br_ip {
 	union {
 		__be32	ip4;
+		__u8	mac[ETH_ALEN];
 #if IS_ENABLED(CONFIG_IPV6)
 		struct in6_addr ip6;
 #endif
diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index 1b3c2b643a02..49a2de0b7420 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -244,6 +244,7 @@ struct br_mdb_entry {
 		union {
 			__be32	ip4;
 			struct in6_addr ip6;
+			__u8	mac[ETH_ALEN];
 		} u;
 		__be16		proto;
 	} addr;
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 681b72862c16..581d6875cdb2 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -84,7 +84,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 		br_flood(br, skb, BR_PKT_BROADCAST, false, true);
 	} else if (is_multicast_ether_addr(dest)) {
 		if (unlikely(netpoll_tx_running(dev))) {
-			br_flood(br, skb, BR_PKT_MULTICAST, false, true);
+			br_flood(br, skb, BR_PKT_MULTICAST_IP, false, true);
 			goto out;
 		}
 		if (br_multicast_rcv(br, NULL, skb, vid)) {
@@ -96,8 +96,11 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
 		    br_multicast_querier_exists(br, eth_hdr(skb)))
 			br_multicast_flood(mdst, skb, false, true);
+		else if (mdst && skb->protocol != htons(ETH_P_IP) &&
+			 skb->protocol != htons(ETH_P_IPV6))
+			br_multicast_flood(mdst, skb, false, true);
 		else
-			br_flood(br, skb, BR_PKT_MULTICAST, false, true);
+			br_flood(br, skb, BR_PKT_MULTICAST_IP, false, true);
 	} else if ((dst = br_fdb_find_rcu(br, dest, vid)) != NULL) {
 		br_forward(dst->dst, skb, false, true);
 	} else {
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 86637000f275..36b58e86d719 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -203,7 +203,8 @@ void br_flood(struct net_bridge *br, struct sk_buff *skb,
 			if (!(p->flags & BR_FLOOD))
 				continue;
 			break;
-		case BR_PKT_MULTICAST:
+		case BR_PKT_MULTICAST_IP:
+		case BR_PKT_MULTICAST_L2:
 			if (!(p->flags & BR_MCAST_FLOOD) && skb->dev != br->dev)
 				continue;
 			break;
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 09b1dd8cd853..f69e710a7f55 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -97,9 +97,13 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 			pkt_type = BR_PKT_BROADCAST;
 			local_rcv = true;
 		} else {
-			pkt_type = BR_PKT_MULTICAST;
+			pkt_type = BR_PKT_MULTICAST_IP;
 			if (br_multicast_rcv(br, p, skb, vid))
 				goto drop;
+
+			if (skb->protocol != htons(ETH_P_IP) &&
+			    skb->protocol != htons(ETH_P_IPV6))
+				pkt_type = BR_PKT_MULTICAST_L2;
 		}
 	}
 
@@ -127,7 +131,12 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 	}
 
 	switch (pkt_type) {
-	case BR_PKT_MULTICAST:
+	case BR_PKT_MULTICAST_L2:
+		mdst = br_mdb_get(br, skb, vid);
+		if (mdst)
+			mcast_hit = true;
+		break;
+	case BR_PKT_MULTICAST_IP:
 		mdst = br_mdb_get(br, skb, vid);
 		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
 		    br_multicast_querier_exists(br, eth_hdr(skb))) {
diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index 428af1abf8cc..25d182f45fde 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -69,12 +69,19 @@ static void __mdb_entry_to_br_ip(struct br_mdb_entry *entry, struct br_ip *ip)
 	memset(ip, 0, sizeof(struct br_ip));
 	ip->vid = entry->vid;
 	ip->proto = entry->addr.proto;
-	if (ip->proto == htons(ETH_P_IP))
+	switch (ip->proto) {
+	case htons(ETH_P_IP):
 		ip->u.ip4 = entry->addr.u.ip4;
+		break;
 #if IS_ENABLED(CONFIG_IPV6)
-	else
+	case htons(ETH_P_IPV6):
 		ip->u.ip6 = entry->addr.u.ip6;
+		break;
 #endif
+	default:
+		ether_addr_copy(ip->u.mac, entry->addr.u.mac);
+		break;
+	}
 }
 
 static int br_mdb_fill_info(struct sk_buff *skb, struct netlink_callback *cb,
@@ -119,12 +126,19 @@ static int br_mdb_fill_info(struct sk_buff *skb, struct netlink_callback *cb,
 			e.ifindex = port->dev->ifindex;
 			e.vid = p->addr.vid;
 			__mdb_entry_fill_flags(&e, p->flags);
-			if (p->addr.proto == htons(ETH_P_IP))
+			switch (p->addr.proto) {
+			case htons(ETH_P_IP):
 				e.addr.u.ip4 = p->addr.u.ip4;
+				break;
 #if IS_ENABLED(CONFIG_IPV6)
-			if (p->addr.proto == htons(ETH_P_IPV6))
+			case htons(ETH_P_IPV6):
 				e.addr.u.ip6 = p->addr.u.ip6;
+				break;
 #endif
+			default:
+				ether_addr_copy(e.addr.u.mac, p->addr.u.mac);
+				break;
+			}
 			e.addr.proto = p->addr.proto;
 			nest_ent = nla_nest_start_noflag(skb,
 							 MDBA_MDB_ENTRY_INFO);
@@ -324,12 +338,19 @@ static void br_mdb_switchdev_host_port(struct net_device *dev,
 		.vid = entry->vid,
 	};
 
-	if (entry->addr.proto == htons(ETH_P_IP))
+	switch (entry->addr.proto) {
+	case htons(ETH_P_IP):
 		ip_eth_mc_map(entry->addr.u.ip4, mdb.addr);
+		break;
 #if IS_ENABLED(CONFIG_IPV6)
-	else
+	case htons(ETH_P_IPV6):
 		ipv6_eth_mc_map(&entry->addr.u.ip6, mdb.addr);
+		break;
 #endif
+	default:
+		ether_addr_copy(mdb.addr, entry->addr.u.mac);
+		break;
+	}
 
 	mdb.obj.orig_dev = dev;
 	switch (type) {
@@ -369,12 +390,19 @@ static void __br_mdb_notify(struct net_device *dev, struct net_bridge_port *p,
 	int err = -ENOBUFS;
 
 	port_dev = __dev_get_by_index(net, entry->ifindex);
-	if (entry->addr.proto == htons(ETH_P_IP))
+	switch (entry->addr.proto) {
+	case htons(ETH_P_IP):
 		ip_eth_mc_map(entry->addr.u.ip4, mdb.addr);
+		break;
 #if IS_ENABLED(CONFIG_IPV6)
-	else
+	case htons(ETH_P_IPV6):
 		ipv6_eth_mc_map(&entry->addr.u.ip6, mdb.addr);
+		break;
 #endif
+	default:
+		ether_addr_copy(mdb.addr, entry->addr.u.mac);
+		break;
+	}
 
 	mdb.obj.orig_dev = port_dev;
 	if (p && port_dev && type == RTM_NEWMDB) {
@@ -425,6 +453,7 @@ void br_mdb_notify(struct net_device *dev, struct net_bridge_port *port,
 #if IS_ENABLED(CONFIG_IPV6)
 	entry.addr.u.ip6 = group->u.ip6;
 #endif
+	ether_addr_copy(group->u.mac, entry.addr.u.mac);
 	entry.vid = group->vid;
 	__mdb_entry_fill_flags(&entry, flags);
 	__br_mdb_notify(dev, port, &entry, type);
@@ -512,6 +541,8 @@ static bool is_valid_mdb_entry(struct br_mdb_entry *entry)
 		if (ipv6_addr_is_ll_all_nodes(&entry->addr.u.ip6))
 			return false;
 #endif
+	} else if (is_multicast_ether_addr(entry->addr.u.mac)) {
+		;
 	} else
 		return false;
 	if (entry->state != MDB_PERMANENT && entry->state != MDB_TEMPORARY)
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 3d4b2817687f..aa28a322ce9d 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -133,7 +133,9 @@ struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
 		break;
 #endif
 	default:
-		return NULL;
+		ip.proto = 0;
+		ether_addr_copy(ip.u.mac, eth_hdr(skb)->h_dest);
+		break;
 	}
 
 	return br_mdb_ip_get_rcu(br, &ip);
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index c4fd307fbfdc..1f2a880a9d17 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -592,7 +592,8 @@ void br_fdb_offloaded_set(struct net_bridge *br, struct net_bridge_port *p,
 /* br_forward.c */
 enum br_pkt_type {
 	BR_PKT_UNICAST,
-	BR_PKT_MULTICAST,
+	BR_PKT_MULTICAST_IP,
+	BR_PKT_MULTICAST_L2,
 	BR_PKT_BROADCAST
 };
 int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb);
-- 
2.21.0


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