Re: [PATCH net] selftests: forwarding: skip if kernel not support setting bridge fdb learning limit

[Nikolay Aleksandrov <razor@blackwall.org>]

On 23/07/2024 12:24, Paolo Abeni wrote:
> 
> 
> On 7/23/24 10:30, Nikolay Aleksandrov wrote:
>> On 23/07/2024 11:22, Hangbin Liu wrote:
>>> If the testing kernel doesn't support setting fdb_max_learned or show
>>> fdb_n_learned, just skip it. Or we will get errors like
>>>
>>> ./bridge_fdb_learning_limit.sh: line 218: [: null: integer expression expected
>>> ./bridge_fdb_learning_limit.sh: line 225: [: null: integer expression expected
>>>
>>> Fixes: 6f84090333bb ("selftests: forwarding: bridge_fdb_learning_limit: Add a new selftest")
>>> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
>>> ---
>>>   .../forwarding/bridge_fdb_learning_limit.sh    | 18 ++++++++++++++++++
>>>   1 file changed, 18 insertions(+)
>>>
>>> diff --git a/tools/testing/selftests/net/forwarding/bridge_fdb_learning_limit.sh b/tools/testing/selftests/net/forwarding/bridge_fdb_learning_limit.sh
>>> index 0760a34b7114..a21b7085da2e 100755
>>> --- a/tools/testing/selftests/net/forwarding/bridge_fdb_learning_limit.sh
>>> +++ b/tools/testing/selftests/net/forwarding/bridge_fdb_learning_limit.sh
>>> @@ -178,6 +178,22 @@ fdb_del()
>>>       check_err $? "Failed to remove a FDB entry of type ${type}"
>>>   }
>>>   +check_fdb_n_learned_support()
>>> +{
>>> +    if ! ip link help bridge 2>&1 | grep -q "fdb_max_learned"; then
>>> +        echo "SKIP: iproute2 too old, missing bridge max learned support"
>>> +        exit $ksft_skip
>>> +    fi
>>> +
>>> +    ip link add dev br0 type bridge
>>> +    local learned=$(fdb_get_n_learned)
>>> +    ip link del dev br0
>>> +    if [ "$learned" == "null" ]; then
>>> +        echo "SKIP: kernel too old; bridge fdb_n_learned feature not supported."
>>> +        exit $ksft_skip
>>> +    fi
>>> +}
>>> +
>>>   check_accounting_one_type()
>>>   {
>>>       local type=$1 is_counted=$2 overrides_learned=$3
>>> @@ -274,6 +290,8 @@ check_limit()
>>>       done
>>>   }
>>>   +check_fdb_n_learned_support
>>> +
>>>   trap cleanup EXIT
>>>     setup_prepare
>>
>> Isn't the selftest supposed to be added after the feature was included?
>>
>> I don't understand why this one is special, we should have the same
>> issue with all new features.
> 
> I must admit I was surprised when I learned the fact, but the stable team routinely runs up2date upstream self-tests on top of stable/older kernels:
> 
> https://lore.kernel.org/mptcp/ZAHLYvOPEYghRcJ1@kroah.com/
> 
> The expected self-test design is to probe the tested feature and skip if not available in the running kernel. The self-test should not break when run on an older kernel not offering such feature.
> 
> I understand some (most?) of the self-tests do not cope with the above perfectly, but we can improve ;).
> 
> Thanks,
> 
> Paolo
> 
> 

Interesting, and unexpected at least for me. :) But okay, I'll keep it in mind
when sending/reviewing patches.

Thanks!

For the patch:
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>