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

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Date:	Wed, 19 Mar 2014 09:42:42 +0900
From:	Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	netdev@...r.kernel.org
CC:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	xen-devel@...ts.xenproject.org, mcgrof@...e.com,
	Stephen Hemminger <stephen@...workplumber.org>,
	bridge@...ts.linux-foundation.org
Subject: Re: [PATCH 1/3] bridge: preserve random init MAC address

(2014/03/13 12:15), Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez" <mcgrof@...e.com>
> 
> 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@...workplumber.org>
> Cc: bridge@...ts.linux-foundation.org
> Cc: netdev@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: xen-devel@...ts.xenproject.org
> Cc: kvm@...r.kernel.org
> Signed-off-by: Luis R. Rodriguez <mcgrof@...e.com>
> ---
>  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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