[PATCH net-next] selftests: net: add a hint about MACAddressPolicy=persistent

[PATCH net-next] selftests: net: add a hint about MACAddressPolicy=persistent

[Jakub Kicinski]

New NIPA installation had been reporting a few flaky tests.
arp_ndisc_evict_nocarrier is most flaky of them all.
I suspect that the flakiness is due to udev swapping the MAC
addresses on the interfaces. Extend the message in
arp_ndisc_evict_nocarrier to hint at this potential issue.
Having the neigh get fail right after ping is rather unusual,
unless udev changes the MAC addr causing a flush in the meantime.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: shuah@kernel.org
CC: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/net/arp_ndisc_evict_nocarrier.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/arp_ndisc_evict_nocarrier.sh b/tools/testing/selftests/net/arp_ndisc_evict_nocarrier.sh
index 92eb880c52f2..00758f00efbf 100755
--- a/tools/testing/selftests/net/arp_ndisc_evict_nocarrier.sh
+++ b/tools/testing/selftests/net/arp_ndisc_evict_nocarrier.sh
@@ -75,7 +75,7 @@ setup_v4() {
     ip neigh get $V4_ADDR1 dev veth0 >/dev/null 2>&1
     if [ $? -ne 0 ]; then
         cleanup_v4
-        echo "failed"
+        echo "failed; is the system using MACAddressPolicy=persistent ?"
         exit 1
     fi
 
-- 
2.51.1

Re: [PATCH net-next] selftests: net: add a hint about MACAddressPolicy=persistent

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 27 Nov 2025 11:45:56 -0800 you wrote:
> New NIPA installation had been reporting a few flaky tests.
> arp_ndisc_evict_nocarrier is most flaky of them all.
> I suspect that the flakiness is due to udev swapping the MAC
> addresses on the interfaces. Extend the message in
> arp_ndisc_evict_nocarrier to hint at this potential issue.
> Having the neigh get fail right after ping is rather unusual,
> unless udev changes the MAC addr causing a flush in the meantime.
> 
> [...]

Here is the summary with links:
  - [net-next] selftests: net: add a hint about MACAddressPolicy=persistent
    https://git.kernel.org/netdev/net-next/c/aadff9f76639

You are awesome, thank you!
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