linux-kernel - [PATCH 3/4] bond_alb: don't tx balance multicast traffic either

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Date:   Tue, 18 May 2021 17:08:48 -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 3/4] bond_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
multicast traffic 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, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index ce8257c7cbea..4df661b77252 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1422,6 +1422,7 @@ struct slave *bond_xmit_alb_slave_get(struct bonding *bond,
 		const struct iphdr *iph;
 
 		if (is_broadcast_ether_addr(eth_data->h_dest) ||
+		    is_multicast_ether_addr(eth_data->h_dest) ||
 		    !pskb_network_may_pull(skb, sizeof(*iph))) {
 			do_tx_balance = false;
 			break;
@@ -1441,7 +1442,8 @@ 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_broadcast_ether_addr(eth_data->h_dest) ||
+		    is_multicast_ether_addr(eth_data->h_dest)) {
 			do_tx_balance = false;
 			break;
 		}
-- 
2.30.2