Re: XDP multi-buffer and AF_XDP

Kal Cutter Conley <[email protected]> writes:

>>
>> Hi,
>> We are very interested in receiving jumbo frames (> 8000 bytes) over
>> AF_XDP. Does XDP multi-buffer support XDP_REDIRECT with AF_XDP? What
>> about in zero-copy mode?
>>
>> Cheers,
>> Kal
>
> Looking into this more I found this comment in the mlx5 driver:
>
> /* Don't enable multi buffer on XDP_REDIRECT SQ, as it's not yet
> * supported by upstream, and there is no defined trigger to allow
> * transmitting redirected multi-buffer frames.
> */
>
> So at least mlx5 does not yet support XDP multi-buffer with
> XDP_REDIRECT. What "upstream" support is required to get XDP_REDIRECT
> to work with XSKs?

Well, the initial patch set for multibuf explicitly blocked XDP_REDIRECT
between interfaces, which is what that comment is referring to (the TX
side).

For AF_XDP we'd also need to define the UAPI, and maybe add a socket
flag so the userspace program can signal to the kernel that it
understands it? Not sure about the details.

You're definitely not the only person who wants this, though; adding in
some people who may have a better idea of the exact steps needed.

-Toke