rtnetlink: bridge: mcast: Relax group address validation in common code

In the upcoming VXLAN MDB implementation, the 0.0.0.0 and :: MDB entries
will act as catchall entries for unregistered IP multicast traffic in a
similar fashion to the 00:00:00:00:00:00 VXLAN FDB entry that is used to
transmit BUM traffic.

In deployments where inter-subnet multicast forwarding is used, not all
the VTEPs in a tenant domain are members in all the broadcast domains.
It is therefore advantageous to transmit BULL (broadcast, unknown
unicast and link-local multicast) and unregistered IP multicast traffic
on different tunnels. If the same tunnel was used, a VTEP only
interested in IP multicast traffic would also pull all the BULL traffic
and drop it as it is not a member in the originating broadcast domain
[1].

Prepare for this change by allowing the 0.0.0.0 group address in the
common rtnetlink MDB code and forbid it in the bridge driver. A similar
change is not needed for IPv6 because the common code only validates
that the group address is not the all-nodes address.

[1] https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-irb-mcast#section-2.6

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index 76636c6..7305f5f 100644 (file)
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -1246,6 +1246,12 @@ static int br_mdb_config_init(struct br_mdb_config *cfg, struct net_device *dev,
                }
        }
 
+       if (cfg->entry->addr.proto == htons(ETH_P_IP) &&
+           ipv4_is_zeronet(cfg->entry->addr.u.ip4)) {
+               NL_SET_ERR_MSG_MOD(extack, "IPv4 entry group address 0.0.0.0 is not allowed");
+               return -EINVAL;
+       }
+
        if (tb[MDBA_SET_ENTRY_ATTRS])
                return br_mdb_config_attrs_init(tb[MDBA_SET_ENTRY_ATTRS], cfg,
                                                extack);

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index f347d9f..b7b1661 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -6152,8 +6152,9 @@ static int rtnl_validate_mdb_entry(const struct nlattr *attr,
        }
 
        if (entry->addr.proto == htons(ETH_P_IP)) {
-               if (!ipv4_is_multicast(entry->addr.u.ip4)) {
-                       NL_SET_ERR_MSG(extack, "IPv4 entry group address is not multicast");
+               if (!ipv4_is_multicast(entry->addr.u.ip4) &&
+                   !ipv4_is_zeronet(entry->addr.u.ip4)) {
+                       NL_SET_ERR_MSG(extack, "IPv4 entry group address is not multicast or 0.0.0.0");
                        return -EINVAL;
                }
                if (ipv4_is_local_multicast(entry->addr.u.ip4)) {