Hello Björn,
On 2018-11-01 19:49, Björn Töpel wrote:
> Den tors 1 nov. 2018 kl 18:14 skrev Konrad Djimeli <kdjimeli@xxxxxxxxxx>:
>>
>> Hello,
>>
>> I am working on developing a Snabb Switch app which uses Af_XDP sockets
>> and so far I have not found any AF_XDP sample example online, except for
>> the sample in the Linux Kernel source. I have tried modifying the
>> example, to create two sockets (sock1 and sock2) sharing a UMEM with
>> custom write_sock and read_sock functions. But when I do a write with
>> "sock1" I am unable to read the data with "sock2". Here is the code
>> https://github.com/djkonro/afxdp/blob/master/xdpsock/xdpsock_user.c ,
>> and I am new to working with AF_XDP sockets and I wish I could get some
>> pointers to what may be wrong with the program.
>>
>
> Hi Konrad,
>
> Let's recap what your application does:
>
> 1. Create two AF_XDP sockets bound to ifindex and a shared UMEM.
> 2. The pass NUM_DESCS descriptors to the UMEM fill ring
> 3. In write_sock BATCH_SIZE packets are put on the Tx ring.
> 4. In read_sock up to BATCH_SIZE packets are picked from the Rx ring.
> 5. The application exits.
>
> In terms of correctness:
>
> In 3. you pass the same UMEM indicies to the Tx ring (ids={0,
> FRAME_SIZE, 2*FRAME_SIZE, ...}), as you have passed to the fill
> ring. This is not correct. Userspace to track what ids are owned by
> the user and by the kernel. Now, both the fill ring and Tx ring
> contain the same id.
Please I have been looking into this for some days now, but I have not
been able to understand what you where referring to and how to fix it.
I also updated the xdp program bpf_redirect_map index to write to the
second socket (sock2) but I can not observe the reading working when I
use any other networking interface except for the 'lo' interface. I
would like to inquire if it may have something to do with the code.
- https://github.com/djkonro/afxdp/blob/master/xdpsock/xdpsock_kern.c
- https://github.com/djkonro/afxdp/blob/master/xdpsock/xdpsock_user.c
Thanks
Konrad
>
> I'm not sure what the expected output of your program should be? Have
> you verified that packets are being sent? Is the inferface/queue 0
> receiving packets?
>
> I think it would help if you explained what you are trying to do
> first!
>
> What XDP program are you running?
>
>
> Cheers,
> Björn
>
>
>
> *
>
>> Thanks,
>> Konrad
>> www.djimeli.me
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