From: Vladimir Oltean vladimir.oltean@nxp.com
[ Upstream commit 7df4e7449489d82cee6813dccbb4ae4f3f26ef7b ]
Qingfang points out that when a bridge with the default settings is created and a port joins it:
ip link add br0 type bridge ip link set swp0 master br0
DSA calls br_multicast_router() on the bridge to see if the br0 device is a multicast router port, and if it is, it enables multicast flooding to the CPU port, otherwise it disables it.
If we look through the multicast_router_show() sysfs or at the IFLA_BR_MCAST_ROUTER netlink attribute, we see that the default mrouter attribute for the bridge device is "1" (MDB_RTR_TYPE_TEMP_QUERY).
However, br_multicast_router() will return "0" (MDB_RTR_TYPE_DISABLED), because an mrouter port in the MDB_RTR_TYPE_TEMP_QUERY state may not be actually _active_ until it receives an actual IGMP query. So, the br_multicast_router() function should really have been called br_multicast_router_active() perhaps.
When/if an IGMP query is received, the bridge device will transition via br_multicast_mark_router() into the active state until the ip4_mc_router_timer expires after an multicast_querier_interval.
Of course, this does not happen if the bridge is created with an mcast_router attribute of "2" (MDB_RTR_TYPE_PERM).
The point is that in lack of any IGMP query messages, and in the default bridge configuration, unregistered multicast packets will not be able to reach the CPU port through flooding, and this breaks many use cases (most obviously, IPv6 ND, with its ICMP6 neighbor solicitation multicast messages).
Leave the multicast flooding setting towards the CPU port down to a driver level decision.
Fixes: 010e269f91be ("net: dsa: sync up switchdev objects and port attributes when joining the bridge") Reported-by: DENG Qingfang dqfext@gmail.com Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/dsa/port.c | 10 ---------- 1 file changed, 10 deletions(-)
diff --git a/net/dsa/port.c b/net/dsa/port.c index 6379d66a6bb3..fad55372e461 100644 --- a/net/dsa/port.c +++ b/net/dsa/port.c @@ -186,10 +186,6 @@ static int dsa_port_switchdev_sync(struct dsa_port *dp, if (err && err != -EOPNOTSUPP) return err;
- err = dsa_port_mrouter(dp->cpu_dp, br_multicast_router(br), extack); - if (err && err != -EOPNOTSUPP) - return err; - err = dsa_port_ageing_time(dp, br_get_ageing_time(br)); if (err && err != -EOPNOTSUPP) return err; @@ -235,12 +231,6 @@ static void dsa_port_switchdev_unsync(struct dsa_port *dp)
/* VLAN filtering is handled by dsa_switch_bridge_leave */
- /* Some drivers treat the notification for having a local multicast - * router by allowing multicast to be flooded to the CPU, so we should - * allow this in standalone mode too. - */ - dsa_port_mrouter(dp->cpu_dp, true, NULL); - /* Ageing time may be global to the switch chip, so don't change it * here because we have no good reason (or value) to change it to. */