[PATCH dpdk v4] net: fix VLAN packet type

[David Marchand]

On Thu, 23 Apr 2026 at 13:25, Robin Jarry <rjarry at redhat.com> wrote:
> diff --git a/lib/net/rte_net.c b/lib/net/rte_net.c
> index 458b4814a9c9..a871318b21c2 100644
> --- a/lib/net/rte_net.c
> +++ b/lib/net/rte_net.c
> @@ -357,12 +357,14 @@ uint32_t rte_net_get_ptype(const struct rte_mbuf *m,
>                 const struct rte_vlan_hdr *vh;
>                 struct rte_vlan_hdr vh_copy;
>
> +               if (vlan_depth == 0) {
> +                       pkt_type =
> +                               proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_VLAN) ?
> +                                        RTE_PTYPE_L2_ETHER_VLAN :
> +                                        RTE_PTYPE_L2_ETHER_QINQ;
> +               }

This code is becoming too complex.
The original usecase with more than 2 stacked vlan is a bit strange,
but the max depth limit seems just arbitrary (why 8?).
We have clear boundaries, with the size of the packet (see below,
check on vh == NULL).

The offending commit also allows stacking mpls on top of vlan, without
mentioning it.
I think we want this behavior, but still was it intended?

In the end, reverting the previous fix then just advancing off and
breaking once proto is not a vlan/qinq type gives a much simpler fix
when compared to v25.11.

(ignoring indent changes with -w)

$ git diff -w v25.11 lib/net/rte_net.c
diff --git a/lib/net/rte_net.c b/lib/net/rte_net.c
index c70b57fdc0..f58d699c83 100644
--- a/lib/net/rte_net.c
+++ b/lib/net/rte_net.c
@@ -349,30 +349,28 @@ uint32_t rte_net_get_ptype(const struct rte_mbuf *m,
        if (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_IPV4))
                goto l3; /* fast path if packet is IPv4 */

-       if (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_VLAN)) {
+       if (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_VLAN) ||
+                       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;
                        off += sizeof(*vh);
                        hdr_lens->l2_len += sizeof(*vh);
                        proto = vh->eth_proto;
-       } else if (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_QINQ)) {
-               const struct rte_vlan_hdr *vh;
-               struct rte_vlan_hdr vh_copy;
+               } while (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_VLAN) ||
+                               proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_QINQ));
+       }

-               pkt_type = RTE_PTYPE_L2_ETHER_QINQ;
-               vh = rte_pktmbuf_read(m, off + sizeof(*vh), sizeof(*vh),
-                       &vh_copy);
-               if (unlikely(vh == NULL))
-                       return pkt_type;
-               off += 2 * sizeof(*vh);
-               hdr_lens->l2_len += 2 * sizeof(*vh);
-               proto = vh->eth_proto;
-       } else if ((proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_MPLS)) ||
+       if ((proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_MPLS)) ||
                (proto == rte_cpu_to_be_16(RTE_ETHER_TYPE_MPLSM))) {
                unsigned int i;
                const struct rte_mpls_hdr *mh;


This is untested, but what do you think?


-- 
David Marchand