netdev - Re: [RFC PATCH bpf-next 3/3] samples/bpf: Add a simple bridge example accelerated with XDP

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Message-Id: <1BA4E035-5045-4D62-BA39-F3990CA4EF1E@gmail.com>
Date:   Tue, 4 Aug 2020 19:35:08 +0900
From:   Yoshiki Komachi <komachi.yoshiki@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        KP Singh <kpsingh@...omium.org>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        David Ahern <dsahern@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        bridge@...ts.linux-foundation.org, bpf <bpf@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 3/3] samples/bpf: Add a simple bridge example
 accelerated with XDP


> 2020/08/01 2:48、Andrii Nakryiko <andrii.nakryiko@...il.com>のメール:
> 
> On Thu, Jul 30, 2020 at 9:45 PM Yoshiki Komachi
> <komachi.yoshiki@...il.com> wrote:
>> 
>> This patch adds a simple example of XDP-based bridge with the new
>> bpf_fdb_lookup helper. This program simply forwards packets based
>> on the destination port given by FDB in the kernel. Note that both
>> vlan filtering and learning features are currently unsupported in
>> this example.
>> 
>> There is another plan to recreate a userspace application
>> (xdp_bridge_user.c) as a daemon process, which helps to automate
>> not only detection of status changes in bridge port but also
>> handling vlan protocol updates.
>> 
>> Note: David Ahern suggested a new bpf helper [1] to get master
>> vlan/bonding devices in XDP programs attached to their slaves
>> when the master vlan/bonding devices are bridge ports. If this
>> idea is accepted and the helper is introduced in the future, we
>> can handle interfaces slaved to vlan/bonding devices in this
>> sample by calling the suggested bpf helper (I guess it can get
>> vlan/bonding ifindex from their slave ifindex). Notice that we
>> don't need to change bpf_fdb_lookup() API to use such a feature,
>> but we just need to modify bpf programs like this sample.
>> 
>> [1]: http://vger.kernel.org/lpc-networking2018.html#session-1
>> 
>> Signed-off-by: Yoshiki Komachi <komachi.yoshiki@...il.com>
>> ---
> 
> Have you tried using a BPF skeleton for this? It could have saved a
> bunch of mechanical code for your example. Also libbpf supports map
> pinning out of the box now, I wonder if it would just work in your
> case. Also it would be nice if you tried using BPF link-based approach
> for this example, to show how it can be used. Thanks!
> 

It is still under consideration, but these features seems to be useful for
this example.

I would try to apply them in the next version.

Thank you for giving me good advice.

Best regards,

> 
>> samples/bpf/Makefile          |   3 +
>> samples/bpf/xdp_bridge_kern.c | 129 ++++++++++++++++++
>> samples/bpf/xdp_bridge_user.c | 239 ++++++++++++++++++++++++++++++++++
>> 3 files changed, 371 insertions(+)
>> create mode 100644 samples/bpf/xdp_bridge_kern.c
>> create mode 100644 samples/bpf/xdp_bridge_user.c
>> 
> 
> [...]

—
Yoshiki Komachi
komachi.yoshiki@...il.com