netdev - Re: [RFC PATCH v2 00/14] Introducing AF

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Message-ID: <CAJ+HfNi+WX-0Q_zQLnvRhJGvWSDaFXzi2EBPVA6c6Znh=cRC=g@mail.gmail.com>
Date:   Thu, 29 Mar 2018 08:16:23 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Eric Leblond <eric@...it.org>
Cc:     "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Netdev <netdev@...r.kernel.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        michael.lundkvist@...csson.com,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Singhai, Anjali" <anjali.singhai@...el.com>,
        "Zhang, Qi Z" <qi.z.zhang@...el.com>, ravineet.singh@...csson.com
Subject: Re: [RFC PATCH v2 00/14] Introducing AF_XDP support

2018-03-28 23:18 GMT+02:00 Eric Leblond <eric@...it.org>:
> Hello,
>
> On Tue, 2018-03-27 at 18:59 +0200, Björn Töpel wrote:
>> From: Björn Töpel <bjorn.topel@...el.com>
>>
>>
> optimized for high performance packet processing and, in upcoming
>> patch sets, zero-copy semantics. In this v2 version, we have removed
>> all zero-copy related code in order to make it smaller, simpler and
>> hopefully more review friendly. This RFC only supports copy-mode for
>> the generic XDP path (XDP_SKB) for both RX and TX and copy-mode for
>> RX
>>
>
> ...
>>
>> How is then packets distributed between these two XSK? We have
>> introduced a new BPF map called XSKMAP (or BPF_MAP_TYPE_XSKMAP in
>> full). The user-space application can place an XSK at an arbitrary
>> place in this map. The XDP program can then redirect a packet to a
>> specific index in this map and at this point XDP validates that the
>> XSK in that map was indeed bound to that device and queue number. If
>> not, the packet is dropped. If the map is empty at that index, the
>> packet is also dropped. This also means that it is currently
>> mandatory
>> to have an XDP program loaded (and one XSK in the XSKMAP) to be able
>> to get any traffic to user space through the XSK.
>
> If I get it correctly, this feature will have to be used to bound
> multiple sockets to a single queue and the eBPF filter will be
> responsible of the load balancing. Am I correct ?
>

Exactly! The XDP program executing for a certain Rx queue will
distribute the packets to the socket(s) in the xskmap.

>> AF_XDP can operate in two different modes: XDP_SKB and XDP_DRV. If
>> the
>> driver does not have support for XDP, or XDP_SKB is explicitly chosen
> ...
>
> Thanks a lot for this work, I'm gonna try to implement this in
> Suricata.
>

Thanks for trying it out! All input is very much appreciated
(clunkiness of API, crashes...)!


Björn

> Best regards,
> --
> Eric Leblond