[PATCH net] net: sparx5: make ports inherit the switch base mac address type

[PATCH net] net: sparx5: make ports inherit the switch base mac address type

[Quentin Freimanis]

When the switch uses a random base MAC address it does not mark each
port's address as random:

  $ dmesg | grep "MAC addr"
  sparx5-switch e00c0000.switch: MAC addr was not set, use random MAC
  $ cat /sys/class/net/eth0/addr_assign_type
  0

0 is NET_ADDR_PERM, so userspace thinks this is a stable address. Fix by
tracking the base MAC address assign type in the sparx5 struct and
applying it to each port's netdev.

Fixes: f3cad2611a77 ("net: sparx5: add hostmode with phylink support")
Signed-off-by: Quentin Freimanis <quentin@q-lab.dev>
---
 drivers/net/ethernet/microchip/sparx5/sparx5_main.c   | 1 +
 drivers/net/ethernet/microchip/sparx5/sparx5_main.h   | 1 +
 drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c | 1 +
 3 files changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_main.c b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
index dad713e9ddd5..b530fb6d3d0c 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
@@ -898,6 +898,7 @@ static int mchp_sparx5_probe(struct platform_device *pdev)
 		dev_info(sparx5->dev, "MAC addr was not set, use random MAC\n");
 		eth_random_addr(sparx5->base_mac);
 		sparx5->base_mac[5] = 0;
+		sparx5->base_mac_assign_type = NET_ADDR_RANDOM;
 	}
 
 	sparx5->fdma_irq = platform_get_irq_byname(sparx5->pdev, "fdma");
diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_main.h b/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
index eb57b86fbe22..0f7d8440f614 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
@@ -392,6 +392,7 @@ struct sparx5 {
 	struct notifier_block switchdev_blocking_nb;
 	/* Switch state */
 	u8 base_mac[ETH_ALEN];
+	u8 base_mac_assign_type;
 	/* Associated bridge device (when bridged) */
 	struct net_device *hw_bridge_dev;
 	/* Bridged interfaces */
diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c b/drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c
index 4dedf5d92641..b3725cf2dd44 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c
@@ -294,6 +294,7 @@ struct net_device *sparx5_create_netdev(struct sparx5 *sparx5, u32 portno)
 	ndev->ethtool_ops = &sparx5_ethtool_ops;
 
 	eth_hw_addr_gen(ndev, sparx5->base_mac, portno + 1);
+	ndev->addr_assign_type = sparx5->base_mac_assign_type;
 
 	return ndev;
 }
-- 
2.55.0

Re: [PATCH net] net: sparx5: make ports inherit the switch base mac address type

[Simon Horman]

On Sun, Sep 27, 2026 at 09:50:12PM -0700, Quentin Freimanis wrote:
> When the switch uses a random base MAC address it does not mark each
> port's address as random:
> 
>   $ dmesg | grep "MAC addr"
>   sparx5-switch e00c0000.switch: MAC addr was not set, use random MAC
>   $ cat /sys/class/net/eth0/addr_assign_type
>   0
> 
> 0 is NET_ADDR_PERM, so userspace thinks this is a stable address. Fix by
> tracking the base MAC address assign type in the sparx5 struct and
> applying it to each port's netdev.
> 
> Fixes: f3cad2611a77 ("net: sparx5: add hostmode with phylink support")
> Signed-off-by: Quentin Freimanis <quentin@q-lab.dev>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net] net: sparx5: make ports inherit the switch base mac address type

[Daniel Machon]

> When the switch uses a random base MAC address it does not mark each
> port's address as random:
> 
>   $ dmesg | grep "MAC addr"
>   sparx5-switch e00c0000.switch: MAC addr was not set, use random MAC
>   $ cat /sys/class/net/eth0/addr_assign_type
>   0
> 
> 0 is NET_ADDR_PERM, so userspace thinks this is a stable address. Fix by
> tracking the base MAC address assign type in the sparx5 struct and
> applying it to each port's netdev.
> 
> Fixes: f3cad2611a77 ("net: sparx5: add hostmode with phylink support")
> Signed-off-by: Quentin Freimanis <quentin@q-lab.dev>

Reviewed-by: Daniel Machon <daniel.machon@microchip.com>

Re: [PATCH net] net: sparx5: make ports inherit the switch base mac address type

[Jakub Kicinski]

On Sun, 27 Sep 2026 21:50:12 -0700 Quentin Freimanis wrote:
> 0 is NET_ADDR_PERM, so userspace thinks this is a stable address. 

Could you please explain the end-user impact of this?
Unclear to me from the commit msg if this is something that broke
your deployment / scripts or maybe you simply noticed it from code
inspection / LLM scan.

No need to repost, just explain, I'll add it when applying.

> Fix by tracking the base MAC address assign type in the sparx5 struct
> and applying it to each port's netdev.

Generally no need to repeat what an average reader can easily grok 
from the diff.

Re: [PATCH net] net: sparx5: make ports inherit the switch base mac address type

[Quentin Freimanis]

Hi Jakub,

On 9/29/26 6:59 PM, Jakub Kicinski wrote:
> On Sun, 27 Sep 2026 21:50:12 -0700 Quentin Freimanis wrote:
>> 0 is NET_ADDR_PERM, so userspace thinks this is a stable address.
> 
> Could you please explain the end-user impact of this?
> Unclear to me from the commit msg if this is something that broke
> your deployment / scripts or maybe you simply noticed it from code
> inspection / LLM scan.
> 
> No need to repost, just explain, I'll add it when applying.
> 

With a random MAC reported as NET_ADDR_PERM, systemd's 
MACAddressPolicy=persistent [1] leaves it unchanged, so a DHCP client 
gets a new IP address every boot and a static reservation can't be used. 
Reporting it as NET_ADDR_RANDOM makes systemd replace it with a stable 
address derived from the interface name and machine-id.

(this is my use case, and how I found the bug)

>> Fix by tracking the base MAC address assign type in the sparx5 struct
>> and applying it to each port's netdev.
> 
> Generally no need to repeat what an average reader can easily grok
> from the diff.

Ack.

- Quentin

[1] 
https://www.freedesktop.org/software/systemd/man/latest/systemd.link.html#MACAddressPolicy=