[PATCH net-next] net: dsa: fix missing host-filtered multicast addresses

[Vladimir Oltean <vladimir.oltean@nxp.com>]

DSA ports are stacked devices, so they use dev_mc_add() to sync their
address list to their lower interface (DSA master). But they are also
hardware devices, so they program those addresses to hardware using the
__dev_mc_add() sync and unsync callbacks.

Unfortunately both cannot work at the same time, and it seems that the
multicast addresses which are already present on the DSA master, like
33:33:00:00:00:01 (added by addrconf.c as in6addr_linklocal_allnodes)
are synced to the master via dev_mc_sync(), but not to hardware by
__dev_mc_sync().

This happens because both the dev_mc_sync() -> __hw_addr_sync_one()
code path, as well as __dev_mc_sync() -> __hw_addr_sync_dev(), operate
on the same variable: ha->sync_cnt, in a way that causes the "sync"
method (dsa_slave_sync_mc) to no longer be called.

To fix the issue we need to work with the API in the way in which it was
intended to be used, and therefore, call dev_uc_add() and friends for
each individual hardware address, from the sync and unsync callbacks.

Fixes: 5e8a1e03aa4d ("net: dsa: install secondary unicast and multicast addresses as host FDB/MDB")
Link: https://lore.kernel.org/netdev/20220321163213.lrn5sk7m6grighbl@skbuf/
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 net/dsa/slave.c | 44 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index d1a3be158d8d..41c69a6e7854 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -111,24 +111,56 @@ static int dsa_slave_schedule_standalone_work(struct net_device *dev,
 static int dsa_slave_sync_uc(struct net_device *dev,
 			     const unsigned char *addr)
 {
+	struct net_device *master = dsa_slave_to_master(dev);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+
+	dev_uc_add(master, addr);
+
+	if (!dsa_switch_supports_uc_filtering(dp->ds))
+		return 0;
+
 	return dsa_slave_schedule_standalone_work(dev, DSA_UC_ADD, addr, 0);
 }
 
 static int dsa_slave_unsync_uc(struct net_device *dev,
 			       const unsigned char *addr)
 {
+	struct net_device *master = dsa_slave_to_master(dev);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+
+	dev_uc_del(master, addr);
+
+	if (!dsa_switch_supports_uc_filtering(dp->ds))
+		return 0;
+
 	return dsa_slave_schedule_standalone_work(dev, DSA_UC_DEL, addr, 0);
 }
 
 static int dsa_slave_sync_mc(struct net_device *dev,
 			     const unsigned char *addr)
 {
+	struct net_device *master = dsa_slave_to_master(dev);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+
+	dev_mc_add(master, addr);
+
+	if (!dsa_switch_supports_mc_filtering(dp->ds))
+		return 0;
+
 	return dsa_slave_schedule_standalone_work(dev, DSA_MC_ADD, addr, 0);
 }
 
 static int dsa_slave_unsync_mc(struct net_device *dev,
 			       const unsigned char *addr)
 {
+	struct net_device *master = dsa_slave_to_master(dev);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+
+	dev_mc_del(master, addr);
+
+	if (!dsa_switch_supports_mc_filtering(dp->ds))
+		return 0;
+
 	return dsa_slave_schedule_standalone_work(dev, DSA_MC_DEL, addr, 0);
 }
 
@@ -283,16 +315,8 @@ static void dsa_slave_change_rx_flags(struct net_device *dev, int change)
 
 static void dsa_slave_set_rx_mode(struct net_device *dev)
 {
-	struct net_device *master = dsa_slave_to_master(dev);
-	struct dsa_port *dp = dsa_slave_to_port(dev);
-	struct dsa_switch *ds = dp->ds;
-
-	dev_mc_sync(master, dev);
-	dev_uc_sync(master, dev);
-	if (dsa_switch_supports_mc_filtering(ds))
-		__dev_mc_sync(dev, dsa_slave_sync_mc, dsa_slave_unsync_mc);
-	if (dsa_switch_supports_uc_filtering(ds))
-		__dev_uc_sync(dev, dsa_slave_sync_uc, dsa_slave_unsync_uc);
+	__dev_mc_sync(dev, dsa_slave_sync_mc, dsa_slave_unsync_mc);
+	__dev_uc_sync(dev, dsa_slave_sync_uc, dsa_slave_unsync_uc);
 }
 
 static int dsa_slave_set_mac_address(struct net_device *dev, void *a)
-- 
2.25.1