linux-kernel - Re: [PATCH net-next v2 3/4] bonding/balance-alb: don't tx balance multicast traffic either

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Date:   Fri, 21 May 2021 10:02:05 -0700
From:   Jay Vosburgh <jay.vosburgh@...onical.com>
To:     Jarod Wilson <jarod@...hat.com>
cc:     linux-kernel@...r.kernel.org, Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Davis <tadavis@....gov>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 3/4] bonding/balance-alb: don't tx balance multicast traffic either

Jarod Wilson <jarod@...hat.com> wrote:

>Multicast traffic going out the non-primary interface can come back in
>through the primary interface in alb mode. When there's a bridge sitting
>on top of the bond, with virtual machines behind it, attached to vnetX
>interfaces also acting as bridge ports, this can cause problems. The
>looped frame has the source MAC of the VM behind the bridge, and ends up
>rewriting the bridge forwarding database entries, replacing a vnetX entry
>in the fdb with the bond instead, at which point, we lose traffic. If we
>don't tx balance multicast traffic, we don't break connectivity.
>
>Cc: Jay Vosburgh <j.vosburgh@...il.com>
>Cc: Veaceslav Falico <vfalico@...il.com>
>Cc: Andy Gospodarek <andy@...yhouse.net>
>Cc: "David S. Miller" <davem@...emloft.net>
>Cc: Jakub Kicinski <kuba@...nel.org>
>Cc: Thomas Davis <tadavis@....gov>
>Cc: netdev@...r.kernel.org
>Signed-off-by: Jarod Wilson <jarod@...hat.com>

Acked-by: Jay Vosburgh <jay.vosburgh@...onical.com>


>---
> drivers/net/bonding/bond_alb.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>index c57f62e43328..cddc4d8b2519 100644
>--- a/drivers/net/bonding/bond_alb.c
>+++ b/drivers/net/bonding/bond_alb.c
>@@ -1418,7 +1418,7 @@ struct slave *bond_xmit_alb_slave_get(struct bonding *bond,
> 	case ETH_P_IP: {
> 		const struct iphdr *iph;
> 
>-		if (is_broadcast_ether_addr(eth_data->h_dest) ||
>+		if (is_multicast_ether_addr(eth_data->h_dest) ||
> 		    !pskb_network_may_pull(skb, sizeof(*iph))) {
> 			do_tx_balance = false;
> 			break;
>@@ -1438,7 +1438,7 @@ struct slave *bond_xmit_alb_slave_get(struct bonding *bond,
> 		/* IPv6 doesn't really use broadcast mac address, but leave
> 		 * that here just in case.
> 		 */
>-		if (is_broadcast_ether_addr(eth_data->h_dest)) {
>+		if (is_multicast_ether_addr(eth_data->h_dest)) {
> 			do_tx_balance = false;
> 			break;
> 		}
>-- 
>2.30.2
>