[PATCH dpdk v5 2/5] net: support multiple stacked VLAN tags

[Kevin Traynor]

On 5/20/26 1:42 PM, David Marchand wrote:
> On Wed, 20 May 2026 at 13:09, Robin Jarry <rjarry at redhat.com> wrote:
>>>> -       } else if (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_QINQ)) {
>>>> -               const struct rte_vlan_hdr *vh;
>>>> -               struct rte_vlan_hdr vh_copy;
>>>> +               if (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_VLAN))
>>>> +                       pkt_type = RTE_PTYPE_L2_ETHER_VLAN;
>>>> +               else
>>>> +                       pkt_type = RTE_PTYPE_L2_ETHER_QINQ;
>>>> +
>>>> +               do {
>>>> +                       vh = rte_pktmbuf_read(m, off, sizeof(*vh), &vh_copy);
>>>> +                       if (unlikely(vh == NULL))
>>>> +                               return pkt_type;
>>>
>>> Kevin noted that it is weird to report back some packet type when the
>>> packet is malformed.
>>> Maybe return RTE_PTYPE_UNKNOWN here so that the application is forced
>>> to validate the packet? (it should already be doing it, in any
>>> case..).
>>
>> If we do this, we need to fix it in the entire function. There are
>> several other places where the "current" value of pkt_type is returned
>> on error.
> 
> There is this point and the code has been behaving like this for
> years, so some applications may have been relying on this behavior.
> I don't mind leaving as is.
> 
> 

I can agree with Hyrum's law :-) https://xkcd.com/1172/