[TEST] bond_macvlan_ipvlan.sh flakiness

[Jakub Kicinski <kuba@kernel.org>]

Hi Hangbin!

The flakiness of bond_macvlan_ipvlan.sh has increased quite a lot
recently. Not sure if there's any correlation with kernel changes,
I didn't spot anything in bonding itself. Here's the history of runs:

https://netdev.bots.linux.dev/contest.html?executor=vmksft-bonding&test=bond-macvlan-ipvlan-sh

It looks like it's gotten much worse starting around the 9th?

Only the non-debug kernel build is flaking, debug builds are completely
clear:

https://netdev.bots.linux.dev/flakes.html?min-flip=0&tn-needle=bond-macvlan-ipvlan-sh

A few things that stood out to me, all the failures are like this:

# TEST: balance-$lb/$$$vlan_bridge: IPv4: client->$$$vlan_2   [FAIL]

Always IPv4 ping to the second interface, always fails neighbor
resolution:

# 192.0.2.12 dev eth0 FAILED 

If it's ipvlan that fails rather than macvlan there is a bunch of
otherhost drops:

# 17: ipvlan0@if15: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
#     link/ether 00:0a:0b:0c:0d:01 brd ff:ff:ff:ff:ff:ff link-netns s-8BLcCn
#     RX:  bytes packets errors dropped  missed   mcast           
#            702      10      0       0       0       3 
#     RX errors:  length    crc   frame    fifo overrun otherhost
#                      0      0       0       0       0         4

FWIW here's the contents of the branches if you want to look thru:
https://netdev.bots.linux.dev/static/nipa/branch_deltas/net-next-2025-11-09--12-00.html
but 9th was the weekend, and the failure just got more frequent,
we've been trying to track this down for a while..