bonding: don't set oif to bond dev when getting NS target destination

Unlike IPv4, IPv6 routing strictly requires the source address to be valid
on the outgoing interface. If the NS target is set to a remote VLAN interface,
and the source address is also configured on a VLAN over a bond interface,
setting the oif to the bond device will fail to retrieve the correct
destination route.

Fix this by not setting the oif to the bond device when retrieving the NS
target destination. This allows the correct destination device (the VLAN
interface) to be determined, so that bond_verify_device_path can return the
proper VLAN tags for sending NS messages.

Reported-by: David Wilder <wilder@us.ibm.com>
Closes: https://lore.kernel.org/netdev/aGOKggdfjv0cApTO@fedora/
Suggested-by: Jay Vosburgh <jv@jvosburgh.net>
Tested-by: David Wilder <wilder@us.ibm.com>
Acked-by: Jay Vosburgh <jv@jvosburgh.net>
Fixes: 4e24be0 ("bonding: add new parameter ns_targets")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://patch.msgid.link/20250916080127.430626-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: liuhangbin

drivers/net/bonding/bond_main.c

@@ -3356,7 +3356,6 @@ static void bond_ns_send_all(struct bonding *bond, struct slave *slave)
 		/* Find out through which dev should the packet go */
 		memset(&fl6, 0, sizeof(struct flowi6));
 		fl6.daddr = targets[i];
-		fl6.flowi6_oif = bond->dev->ifindex;
 
 		dst = ip6_route_output(dev_net(bond->dev), NULL, &fl6);
 		if (dst->error) {