Subject: Re: [PATCH net-next] bonding: allow bond in mode balance-alb to work properly in bridge -try4.3

From: Eric Dumazet <[email-masked]>
Date: Thu, 28 May 2009 13:41:59 +0200

Jiri Pirko a écrit :
> [PATCH net-next] bonding: allow bond in mode balance-alb to work properly in bridge -try4.3
> 
> (updated)
> changes v4.2 -> v4.3
> - memcpy the address always, not just in case it differs from master->dev_addr
> - compare_ether_addr_64bits() is not used so there is no direct need to make new
>   header file (I think it would be good to have bond stuff in separate file
>   anyway).

Yes, this could be done in a future cleanup patch.
I find this (short) version easier to review for a new feature.

Signed-off-by: Eric Dumazet <[email-masked]>

> 
> changes v4.1 -> v4.2
> - use skb->pkt_type == PACKET_HOST compare rather then comparing skb dest addr
>   against skb->dev->dev_addr
> 
> Hi all.
> 
> The problem is described in following bugzilla:
> https://bugzilla.redhat.com/show_bug.cgi?id=487763
> 
> Basically here's what's going on. In every mode, bonding interface uses the same
> mac address for all enslaved devices (except fail_over_mac). Only balance-alb
> will simultaneously use multiple MAC addresses across different slaves. When you
> put this kind of bond device into a bridge it will only add one of mac adresses
> into a hash list of mac addresses, say X. This mac address is marked as local.
> But this bonding interface also has mac address Y. Now then packet arrives with
> destination address Y, this address is not marked as local and the packed looks
> like it needs to be forwarded. This packet is then lost which is wrong.
> 
> Notice that interfaces can be added and removed from bond while it is in bridge.
> 
> ***
> When the multiple addresses for bridge port approach failed to solve this issue
> due to STP I started to think other way to solve this. I returned to previous
> solution but tweaked one.
> 
> This patch solves the situation in the bonding without touching bridge code.
> For every incoming frame to bonding the destination address is compared to
> current address of the slave device from which tha packet came. If these two
> match destination address is replaced by mac address of the master. This address
> is known by bridge so it is delivered properly. Note that the comparsion is not
> made directly, it's used skb->pkt_type == PACKET_HOST instead. This is "set"
> previously in eth_type_trans().
> 
> I experimentally tried that this works as good as searching through the slave
> list (v4 of this patch).
> 
> Jirka
> 
> 
> Signed-off-by: Jiri Pirko <[email-masked]>
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 371ece5..9b4db94 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1920,6 +1920,16 @@ static inline void netif_set_gso_max_size(struct net_device *dev,
>  	dev->gso_max_size = size;
>  }
>  
> +static inline void skb_bond_set_mac_by_master(struct sk_buff *skb,
> +					      struct net_device *master)
> +{
> +	if (skb->pkt_type == PACKET_HOST) {
> +		u16 *dest = (u16 *) eth_hdr(skb)->h_dest;
> +
> +		memcpy(dest, master->dev_addr, ETH_ALEN);
> +	}
> +}
> +
>  /* On bonding slaves other than the currently active slave, suppress
>   * duplicates except for 802.3ad ETH_P_SLOW, alb non-mcast/bcast, and
>   * ARP on active-backup slaves with arp_validate enabled.
> @@ -1933,6 +1943,14 @@ static inline int skb_bond_should_drop(struct sk_buff *skb)
>  		if (master->priv_flags & IFF_MASTER_ARPMON)
>  			dev->last_rx = jiffies;
>  
> +		if ((master->priv_flags & IFF_MASTER_ALB) && master->br_port) {
> +			/* Do address unmangle. The local destination address
> +			 * will be always the one master has. Provides the right
> +			 * functionality in a bridge.
> +			 */
> +			skb_bond_set_mac_by_master(skb, master);
> +		}
> +
>  		if (dev->priv_flags & IFF_SLAVE_INACTIVE) {
>  			if ((dev->priv_flags & IFF_SLAVE_NEEDARP) &&
>  			    skb->protocol == __cpu_to_be16(ETH_P_ARP))