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SubjectRe: [PATCH] fix tuntap oversight
Jeremy Martin wrote:
> On Mon, Apr 12, 2004 at 12:15:51AM -0700, David S. Miller wrote:
>
>>This netif_running() check is not necessary, and in fact
>>wrong.
>>
>>In fact, if ethernet drivers erroneously do this, this causes
>>them to fail to support the ALB bonding driver modes which
>>require on-the-fly MAC address changes while the interface is
>>up.
>>
>
>
> I just took a look in drivers/net/
> and
> acenic.c
> atarilance.c
> b44.c
> cs89x0.c
> net_init.c
> typhoon.c
>
> all use that netif_running() check when setting the MAC. I actually just pulled
> the function from net_init.c for the tun change. Are these broken?
> (I'm asking in total ignorance so be gentle :).

It's different for a driver that drives real hardware.

struct net_device::set_mac_address() is called inside rtnl_lock(). The
safe thing to do is
1) read MAC address from eeprom on probe
2) write MAC address to hardware upon each dev->open()
3) use default eth_mac_addr() from net_init.c

And the netif_running() check in eth_mac_addr() is correct, because it
does not update the hardware MAC address (which in this API would be
impossible).

Normally the netif_running() check is for hardware that cannot update
its MAC address safely during operation.

Jeff



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