netdev - [PATCH net-next 4/6] net: dsa: be mostly no-op in dsa_slave_set_mac

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Date:   Tue,  8 Mar 2022 11:15:13 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        Alvin Šipraga <alsi@...g-olufsen.dk>
Subject: [PATCH net-next 4/6] net: dsa: be mostly no-op in dsa_slave_set_mac_address when down

Since the slave unicast address is synced to hardware and to the DSA
master during dsa_slave_open(), this means that a call to
dsa_slave_set_mac_address() while the slave interface is down will
result to a call to dsa_port_standalone_host_fdb_del() and to
dev_uc_del() for the MAC address while there was no previous
dsa_port_standalone_host_fdb_add() or dev_uc_add().

This is a partial revert of the blamed commit below, which was too
aggressive.

Fixes: 35aae5ab9121 ("net: dsa: remove workarounds for changing master promisc/allmulti only while up")
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 net/dsa/slave.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 42436ac6993b..a61a7c54af20 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -305,6 +305,12 @@ static int dsa_slave_set_mac_address(struct net_device *dev, void *a)
 	if (!is_valid_ether_addr(addr->sa_data))
 		return -EADDRNOTAVAIL;
 
+	/* If the port is down, the address isn't synced yet to hardware or
+	 * to the DSA master, so there is nothing to change.
+	 */
+	if (!(dev->flags & IFF_UP))
+		goto out_change_dev_addr;
+
 	if (dsa_switch_supports_uc_filtering(ds)) {
 		err = dsa_port_standalone_host_fdb_add(dp, addr->sa_data, 0);
 		if (err)
@@ -323,6 +329,7 @@ static int dsa_slave_set_mac_address(struct net_device *dev, void *a)
 	if (dsa_switch_supports_uc_filtering(ds))
 		dsa_port_standalone_host_fdb_del(dp, dev->dev_addr, 0);
 
+out_change_dev_addr:
 	eth_hw_addr_set(dev, addr->sa_data);
 
 	return 0;
-- 
2.25.1