[PATCH net-next] net: dsa: set random switch address

[Vivien Didelot]

An Ethernet switch may support having a MAC address, which can be used
as the switch's source address in transmitted full-duplex Pause frames.

If a DSA switch supports the related .set_addr operation, the DSA core
sets the master's MAC address on the switch.

This won't make sense anymore in a multi-CPU ports system, because there
won't be a unique master device assigned to a switch tree.

To fix this, assign a random MAC address to the switch chip instead.

Signed-off-by: Vivien Didelot <vivien.dide...@savoirfairelinux.com>
---
 net/dsa/dsa2.c     |  8 +++-----
 net/dsa/dsa_priv.h |  1 +
 net/dsa/legacy.c   |  8 +++-----
 net/dsa/switch.c   | 17 +++++++++++++++++
 4 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index 54ed054777bd..8e5780ddd7f9 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -336,11 +336,9 @@ static int dsa_ds_apply(struct dsa_switch_tree *dst, 
struct dsa_switch *ds)
        if (err)
                return err;
 
-       if (ds->ops->set_addr) {
-               err = ds->ops->set_addr(ds, dst->cpu_dp->netdev->dev_addr);
-               if (err < 0)
-                       return err;
-       }
+       err = dsa_switch_set_addr(ds);
+       if (err)
+               return err;
 
        if (!ds->slave_mii_bus && ds->ops->phy_read) {
                ds->slave_mii_bus = devm_mdiobus_alloc(ds->dev);
diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 2850077cc9cc..9c4c17a4bd6b 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -172,6 +172,7 @@ void dsa_slave_unregister_notifier(void);
 /* switch.c */
 int dsa_switch_register_notifier(struct dsa_switch *ds);
 void dsa_switch_unregister_notifier(struct dsa_switch *ds);
+int dsa_switch_set_addr(struct dsa_switch *ds);
 
 /* tag_brcm.c */
 extern const struct dsa_device_ops brcm_netdev_ops;
diff --git a/net/dsa/legacy.c b/net/dsa/legacy.c
index 19ff6e0a21dc..340ca7997271 100644
--- a/net/dsa/legacy.c
+++ b/net/dsa/legacy.c
@@ -172,11 +172,9 @@ static int dsa_switch_setup_one(struct dsa_switch *ds,
        if (ret)
                return ret;
 
-       if (ops->set_addr) {
-               ret = ops->set_addr(ds, master->dev_addr);
-               if (ret < 0)
-                       return ret;
-       }
+       ret = dsa_switch_set_addr(ds);
+       if (ret)
+               return ret;
 
        if (!ds->slave_mii_bus && ops->phy_read) {
                ds->slave_mii_bus = devm_mdiobus_alloc(ds->dev);
diff --git a/net/dsa/switch.c b/net/dsa/switch.c
index e6c06aa349a6..b45a26b006af 100644
--- a/net/dsa/switch.c
+++ b/net/dsa/switch.c
@@ -10,6 +10,7 @@
  * (at your option) any later version.
  */
 
+#include <linux/etherdevice.h>
 #include <linux/netdevice.h>
 #include <linux/notifier.h>
 #include <net/switchdev.h>
@@ -267,3 +268,19 @@ void dsa_switch_unregister_notifier(struct dsa_switch *ds)
        if (err)
                dev_err(ds->dev, "failed to unregister notifier (%d)\n", err);
 }
+
+int dsa_switch_set_addr(struct dsa_switch *ds)
+{
+       u8 addr[6];
+       int err;
+
+       if (ds->ops->set_addr) {
+               eth_random_addr(addr);
+
+               err = ds->ops->set_addr(ds, addr);
+               if (err)
+                       return err;
+       }
+
+       return 0;
+}
-- 
2.14.2