Re: [dpdk-users] mlx5 driver didn't set corresponding packet_type flag in TCP_ACK packet case

[Bin Huang <huangbin.mails@gmail.com>]

Hi Nélio, Yongseok,


On Wed, Mar 28, 2018 at 5:12 AM, Yongseok Koh <yskoh@mellanox.com> wrote:
> On Tue, Mar 27, 2018 at 09:14:34AM +0200, Nélio Laranjeiro wrote:
>> Hi Bin,
>>
>> On Mon, Mar 26, 2018 at 06:09:35PM +0800, Bin Huang wrote:
>> > Greetings all,
>> >
>> >
>> > I have run l3fwd example program using two mlx5 NIC(
>> > MLNX_OFED_LINUX-4.3-1.0.1.0 ) base on DPDK 17.08 and use pktgen as
>> > flowgen.
>> >
>> > This demo provided by DPDK works fine in UDP case, but in pktgen TCP
>> > case, l3fwd can't forward packet to nexthop port.
>> >
>> >
>> > After look into function rxq_cq_to_pkt_type(), I found while handling
>> > IPv4 TCP ACK packets:
>> >
>> > > l4_hdr_type bits[2:0] in CQE is (100)
>> >
>> > > l3_hdr_type bits[1:0] in CQE is (10)
>> >
>> >
>> > It looks fine according to CQE format in
>> > <Ethernet_Adapters_Programming_Manual> doc:
>> >
>> > > l4_hdr_type:
>> >     0 - None
>> >     1 - TCP header was present in the packet
>> >     2 - UDP header was present in the packet
>> >     3 - TCP header was present in the packet with Empty TCP ACK
>> > indication. (TCP packet <ACK> flag is set, and packet carries no data)
>> >     4 - TCP header was present in the packet with TCP ACK indication.
>> > (TCP packet <ACK> flag is set, and packet carries data).
>> >
>> > > l3_hdr_type:
>> >
>> >     00 - None
>> >     01 - IPv6
>> >     10 - IPv4
>> >
>> >
>> > But combined l4_hdr_type and l3_hdr_type into idx, the idx would be
>> > 0x12, which was not reserved in mlx5_set_ptype_type().
>> >
>> > Then RTE_PTYPE_UNKNOWN would be return to caller which caused
>> > sub-sequence procedure going wrong.
>> >
>> >
>> > Did I omit any possible configuration to make ptype flag work for TCP
>> > ACK packets, or should I add (*p)[0x12] in mlx5_set_ptype_type() to
>> > make this work?
>>
>> According to the mlx5_set_ptype_table(), the index of the array is a
>> little more complex:
>>
>>  /*
>>   * The index to the array should have:
>>   * bit[1:0] = l3_hdr_type
>>   * bit[4:2] = l4_hdr_type
>>   * bit[5] = ip_frag
>>   * bit[6] = tunneled
>>   * bit[7] = outer_l3_type
>>   */
>>
>> If in the CQE the other three fields are 0, your hypothesis is correct
>> and index 0x12 should be filled.
>>
>> Can you also check it?

I have checked other three bit fields from CQE:
bit[5] = ip_frag
bit[6] = tunneled
bit[7] = outer_l3_type
 they are all 0 as I use non-tunneled packet.

>
> When I changed it to the current array-based conversion, I followed the use of
> MLX5_CQE_RX_TCP_PACKET [1], but it looks Bin is right. A packet should be
> identified as TCP packet if l4_hdr_type is 1, 3 or 4.
>
> Bin, will you send out a patch for it or shall I?
> I'd love to see a patch from you. :-)
>

Sure, I will send out a patch for review.

>
> [1] http://dpdk.org/browse/dpdk/commit/?id=ea16068c00647fb6c7fe8704d8ad2adff6bf378f
>
> Thanks,
> Yongseok

Thanks,
Bin