[net-next,v2] net: allow setting mac address of loopback device

We are trying to mirror the local traffic from lo to eth0,
allowing setting mac address of lo to eth0 would make
the ether addresses in these packets correct, so that
we don't have to modify the ether header again.

Since usually no one cares about its mac address (all-zero),
it is safe to allow those who care to set its mac address.

Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

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On Tue, Feb 11, 2014 at 05:21:26PM -0800, Cong Wang wrote:
> We are trying to mirror the local traffic from lo to eth0,
> allowing setting mac address of lo to eth0 would make
> the ether addresses in these packets correct, so that
> we don't have to modify the ether header again.
> 
> Since usually no one cares about its mac address (all-zero),
> it is safe to allow those who care to set its mac address.
> 
> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Cc: Neil Horman <nhorman@tuxdriver.com>
> Cc: Stephen Hemminger <stephen@networkplumber.org>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: David S. Miller <davem@davemloft.net>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> 
Acked-by: Neil Horman <nhorman@tuxdriver.com>

> ---
> diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
> index c5011e0..e7c1d5f 100644
> --- a/drivers/net/loopback.c
> +++ b/drivers/net/loopback.c
> @@ -160,6 +160,7 @@ static const struct net_device_ops loopback_ops = {
>  	.ndo_init      = loopback_dev_init,
>  	.ndo_start_xmit= loopback_xmit,
>  	.ndo_get_stats64 = loopback_get_stats64,
> +	.ndo_set_mac_address = eth_mac_addr,
>  };
>  
>  /*
> @@ -174,6 +175,7 @@ static void loopback_setup(struct net_device *dev)
>  	dev->tx_queue_len	= 0;
>  	dev->type		= ARPHRD_LOOPBACK;	/* 0x0001*/
>  	dev->flags		= IFF_LOOPBACK;
> +	dev->priv_flags		|= IFF_LIVE_ADDR_CHANGE;
>  	dev->priv_flags	       &= ~IFF_XMIT_DST_RELEASE;
>  	dev->hw_features	= NETIF_F_ALL_TSO | NETIF_F_UFO;
>  	dev->features 		= NETIF_F_SG | NETIF_F_FRAGLIST
> 
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From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Tue, 11 Feb 2014 17:21:26 -0800

> We are trying to mirror the local traffic from lo to eth0,
> allowing setting mac address of lo to eth0 would make
> the ether addresses in these packets correct, so that
> we don't have to modify the ether header again.
> 
> Since usually no one cares about its mac address (all-zero),
> it is safe to allow those who care to set its mac address.
> 
> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Cc: Neil Horman <nhorman@tuxdriver.com>
> Cc: Stephen Hemminger <stephen@networkplumber.org>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: David S. Miller <davem@davemloft.net>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied, thanks.
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