On 25/04/2023 15:29, Ilya Maximets wrote:
> On 4/25/23 08:32, Roi Dayan via dev wrote:
>> From: Gavin Li <[email protected]>
>>
>> Linux kernel netlink module added NLA_F_NESTED flag checking for nested
>> netlink messages in 5.2. A nested message without the flag set will be
>> treated as malformated one. The check is optional and is controlled by
>> message policy. To avoid this, add NLA_F_NESTED explicitly for all
>> nested netlink messages.
>>
>> Signed-off-by: Gavin Li <[email protected]>
>> Reviewed-by: Roi Dayan <[email protected]>
>> ---
>> lib/netlink.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/netlink.c b/lib/netlink.c
>> index 6215282d6fbe..f128b63074f9 100644
>> --- a/lib/netlink.c
>> +++ b/lib/netlink.c
>> @@ -519,7 +519,7 @@ size_t
>> nl_msg_start_nested(struct ofpbuf *msg, uint16_t type)
>> {
>> size_t offset = msg->size;
>> - nl_msg_put_unspec_uninit(msg, type, 0);
>> + nl_msg_put_unspec_uninit(msg, type | NLA_F_NESTED, 0);
>
>
> Are you sure this is safe?
>
> IIRC, the NLA_F_NESTED checking is not enforced on legacy interfaces
> like the OVS family. And the OVS kernel module in not using netlink
> macros in various places for iteration or attribute checking, so it
> may misinterpret the extra bit as an unknown attribute.
>
> Best regards, Ilya Maximets.
we haven't encountered an issue with it.
I think it just being ignored then.
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