linux-kernel - [PATCH net-next v2 2/4] bonding/balance-lb: don't rewrite bridged non-local MACs

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Date:   Fri, 21 May 2021 09:27:54 -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 2/4] bonding/balance-lb: don't rewrite bridged non-local MACs

With a virtual machine behind a bridge that directly incorporates a
balance-alb bond as one of its ports, outgoing traffic should retain the
VM's source MAC. That works fine most of the time, until doing a failover,
and then the MAC gets rewritten to the bond slave's MAC, and the return
traffic gets dropped. If we don't rewrite the MAC there, we don't lose the
traffic.

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 | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 3455f2cc13f2..c57f62e43328 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1302,6 +1302,23 @@ void bond_alb_deinitialize(struct bonding *bond)
 		rlb_deinitialize(bond);
 }
 
+static bool bond_alb_bridged_mac(struct bonding *bond, struct ethhdr *eth_data)
+{
+	if (BOND_MODE(bond) != BOND_MODE_ALB)
+		return false;
+
+	/* Don't modify source MACs that do not originate locally
+	 * (e.g.,arrive via a bridge).
+	 */
+	if (!netif_is_bridge_port(bond->dev))
+		return false;
+
+	if (bond_slave_has_mac_rx(bond, eth_data->h_source))
+		return false;
+
+	return true;
+}
+
 static netdev_tx_t bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
 				    struct slave *tx_slave)
 {
@@ -1316,7 +1333,8 @@ static netdev_tx_t bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
 	}
 
 	if (tx_slave && bond_slave_can_tx(tx_slave)) {
-		if (tx_slave != rcu_access_pointer(bond->curr_active_slave)) {
+		if (tx_slave != rcu_access_pointer(bond->curr_active_slave) &&
+		    !bond_alb_bridged_mac(bond, eth_data)) {
 			ether_addr_copy(eth_data->h_source,
 					tx_slave->dev->dev_addr);
 		}
-- 
2.30.2