Re: [Xen-devel] [PATCH 1/3] bridge: preserve random init MAC address

[Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx>]

(2014/03/13 12:15), Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>
> 
> As it is now if you add create a bridge it gets started
> with a random MAC address and if you then add a net_device
> as a slave but later kick it out you end up with a zero
> MAC address. Instead preserve the original random MAC
> address and use it.
> 
> If you manually set the bridge address that will always
> be respected. This change only takes effect if at the time
> of computing the new root port we determine we have found
> no candidates.
> 
> Cc: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
> Cc: bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx
> Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxx>
> ---
>  net/bridge/br_device.c  | 1 +
>  net/bridge/br_private.h | 1 +
>  net/bridge/br_stp_if.c  | 3 +++
>  3 files changed, 5 insertions(+)
> 
> diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
> index b063050..5f13eac 100644
> --- a/net/bridge/br_device.c
> +++ b/net/bridge/br_device.c
> @@ -368,6 +368,7 @@ void br_dev_setup(struct net_device *dev)
>       br->bridge_id.prio[1] = 0x00;
>  
>       ether_addr_copy(br->group_addr, eth_reserved_addr_base);
> +     ether_addr_copy(br->random_init_addr, dev->dev_addr);
>  
>       br->stp_enabled = BR_NO_STP;
>       br->group_fwd_mask = BR_GROUPFWD_DEFAULT;
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index e1ca1dc..32a06da 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -240,6 +240,7 @@ struct net_bridge
>       unsigned long                   bridge_hello_time;
>       unsigned long                   bridge_forward_delay;
>  
> +     u8                              random_init_addr[ETH_ALEN];
>       u8                              group_addr[ETH_ALEN];
>       u16                             root_port;
>  
> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> index 189ba1e..4c9ad45 100644
> --- a/net/bridge/br_stp_if.c
> +++ b/net/bridge/br_stp_if.c
> @@ -239,6 +239,9 @@ bool br_stp_recalculate_bridge_id(struct net_bridge *br)
>       if (ether_addr_equal(br->bridge_id.addr, addr))
>               return false;   /* no change */
>  
> +     if (ether_addr_equal(addr, br_mac_zero))
> +             addr = br->random_init_addr;
> +
>       br_stp_change_bridge_id(br, addr);
>       return true;
>  }

nit,
If the last detached port happens to have the same addr as
random_init_addr, this seems to call br_stp_change_bridge_id() even
though bridge_id is not changed.

Shouldn't the assignment of random_init_addr be done before the check of
"no change"?

Toshiaki Makita

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