[PATCH] net/rte_net: fix inner L2 length for tunneled Ethernet packets

[Ivan Malov]

Hi,

On Fri, 1 Aug 2025, Khadem Ullah wrote:

> Hi Andrew,
>
> Thanks for your feedback.
>
> Please check mbuf packet types and the following test case:
> https://doc.dpdk.org/dts-20.02/test_plans/uni_pkt_test_plan.html#test-case-vxlan-tunnel-packet-type-detect
> sendp([Ether()/IP()/UDP()/Vxlan()/Ether()/IP(frag=5)/Raw('\0'*40)],
> iface=txItf)
>
> (outer) L2 type: ETHER
> (outer) L3 type: IPV4_EXT_UNKNOWN
> (outer) L4 type: Unknown
> Tunnel type: GRENAT
> Inner L2 type: ETHER
> Inner L3 type: IPV4_EXT_UNKNOWN
> Inner L4 type: L4_FRAG
>
>
> union {
>        uint32_t packet_type; /**< L2/L3/L4 and tunnel information. */
>        __extension__
>        struct {
>          uint8_t l2_type:4;   /**< (Outer) L2 type. */
>          uint8_t l3_type:4;   /**< (Outer) L3 type. */
>          uint8_t l4_type:4;   /**< (Outer) L4 type. */
>          uint8_t tun_type:4;  /**< Tunnel type. */
>          union {
>            uint8_t inner_esp_next_proto;
>            /**< ESP next protocol type, valid if
>             * RTE_PTYPE_TUNNEL_ESP tunnel type is set
>             * on both Tx and Rx.
>             */
>            __extension__
>            struct {
>              uint8_t inner_l2_type:4;
>              /**< Inner L2 type. */
>              uint8_t inner_l3_type:4;
>              /**< Inner L3 type. */
>            };
>          };
>          uint8_t inner_l4_type:4; /**< Inner L4 type. */
>        };
>      };
>
>
> Based on the above, it seems that inner_l2_len have to the length of Ether.
> Ther might need to be some correspondent between both fields to potray the same information.
> Or, the inner_l2_type and inner_l2_len are completly different ?

On the one hand, there is mbuf structure, which has got no 'tunnel_len' field.
It has 'l2_len' field [1] with a comment saying that for a tunnel packet, it
includes some extra terms apart from just 'inner L2 header size'. This use of
the 'l2_len' mbuf field is absolutely legitimate, and PMDs confirm this stance.

On the other hand, there is 'rte_net_hdr_lens' structure [2], which does have a
separate 'tunnel_len' field and, in general, has got slightly different naming.
And the 'inner_l2_len' field has a comment that looks almost like a copy-paste
from the mbuf structure. So does 'inner_l2_len' really need to include extra
terms, given the presence of a dedicated 'tunnel_len' field? Is it at all
correct or could it have been overlooked? One should take a closer look.

[1] https://github.com/DPDK/dpdk/blob/b222395561638f89562e4ef42e1eabf2d6db43dd/lib/mbuf/rte_mbuf_core.h#L628
[2] https://github.com/DPDK/dpdk/blob/b222395561638f89562e4ef42e1eabf2d6db43dd/lib/net/rte_net.h#L22

Thank you.

>
> Best Regards,
> Khadem
>