linux-kernel - [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 09:27:55 -0400
From:   Jarod Wilson <jarod@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Jarod Wilson <jarod@...hat.com>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        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: [PATCH net-next v2 3/4] bonding/balance-alb: don't tx balance multicast traffic either

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>
---
 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