[dpdk-dev] Byte order of vlan_tci of rte_mbuf is different on different source

[Olivier Matz]

Hi,

On 04/25/2016 04:35 AM, zhang.xinghua1 at zte.com.cn wrote:
> When using I350 working on SR-IOV mode, we got confused that byte order 
> of vlan_tci in the VF received packet descriptor is different when the
> packet source is different.
> 
> 1) Packets from VF to VF, the byte order is big-endian. (e.g. 0xF00)
> 2) Packets from PC to VF, the byte order is little-endian. (e.g. 0xF)
> 
> Below is the testing net-work:
>         VM0            VM1             PC
>         VF0            VF1              |
>           |             |               |
>           +------+------+               |
>                  |                      |
>                  PF                     |
>              hypervisor                 |
>              SR-IOV NIC                 |
>                  |                      |
>                  |        VLAN 15       |
>                  +---------switch-------+
> 
> 
> We make a breakpoint at the following line of eth_igb_recv_pkts, the 
> vlan_tci
> we observed that everytime.
> 
> uint16_t
> eth_igb_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>                uint16_t nb_pkts)
> 
>                 /* Only valid if PKT_RX_VLAN_PKT set in pkt_flags */
>                 rxm->vlan_tci = rte_le_to_cpu_16(rxd.wb.upper.vlan);

In rte_mbuf.h, it is specified that these values (vlan_tci and
vlan_tci_outer) must be stored in CPU order.

It's probably a driver or hardware issue. Note that in linux there is
something that looks similar to your issue:

http://lxr.free-electrons.com/source/drivers/net/ethernet/intel/igb/igb_main.c#L1278

      /* On i350, i354, i210, and i211, loopback VLAN packets
       * have the tag byte-swapped.
       */
      if (adapter->hw.mac.type >= e1000_i350)
          set_bit(IGB_RING_FLAG_RX_LB_VLAN_BSWAP, &ring->flags);

I think you could check if the same thing is done in the
dpdk driver.


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Regards,
Olivier