[PATCH net v2] bonding: Add net_ratelimit for bond_xdp_get_xmit_slave in bond_main.c

[Jiwon Kim <jiwonaid0@gmail.com>]

Add net_ratelimit to reduce warnings and logs.
This addresses the WARNING in bond_xdp_get_xmit_slave reported by syzbot.

Setup:
    # Need xdp_tx_prog with return XDP_TX;
    ip l add veth0 type veth peer veth1
    ip l add veth3 type veth peer veth4
    ip l add bond0 type bond mode 6 # <- BOND_MODE_ALB, unsupported by xdp
    ip l add bond1 type bond # <- BOND_MODE_ROUNDROBIN by default
    ip l set veth0 master bond1
    ip l set bond1 up
    ip l set dev bond1 xdpdrv object tx_xdp.o section xdp_tx
    ip l set veth3 master bond0
    ip l set bond0 up
    ip l set veth4 up
    ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx

Reported-by: syzbot+c187823a52ed505b2257@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c187823a52ed505b2257
Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
Signed-off-by: Jiwon Kim <jiwonaid0@gmail.com>
---
v2: Change the patch to fix bond_xdp_get_xmit_slave
---
 drivers/net/bonding/bond_main.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index b560644ee1b1..91b9cbdcf274 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5610,9 +5610,12 @@ bond_xdp_get_xmit_slave(struct net_device *bond_dev, struct xdp_buff *xdp)
 		break;
 
 	default:
-		/* Should never happen. Mode guarded by bond_xdp_check() */
-		netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n", BOND_MODE(bond));
-		WARN_ON_ONCE(1);
+		/* This might occur when a bond device increases bpf_master_redirect_enabled_key,
+		 * and another bond device with XDP_TX and bond slave.
+		 */
+		if (net_ratelimit())
+			netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n",
+				   BOND_MODE(bond));
 		return NULL;
 	}
 
-- 
2.43.0