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

[Paolo Abeni <pabeni@redhat.com>]

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