netdev - Re: [RFC PATCH v2 bpf-next 00/15] xdp

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Date:   Mon, 28 Oct 2019 13:05:56 -0600
From:   David Ahern <dsahern@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Toshiaki Makita <toshiaki.makita1@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Pravin B Shelar <pshelar@....org>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        William Tu <u9012063@...il.com>,
        Stanislav Fomichev <sdf@...ichev.me>
Subject: Re: [RFC PATCH v2 bpf-next 00/15] xdp_flow: Flow offload to XDP

On 10/28/19 2:36 AM, Toke Høiland-Jørgensen wrote:
> 
>> Linux bridge on the other hand seems fairly straightforward to
>> refactor. One helper is needed to convert ingress <port,mac,vlan> to
>> an L2 device (and needs to consider stacked devices) and then a second
>> one to access the fdb for that device.
> 
> Why not just a single lookup like what you did for routing? Not too
> familiar with the routing code...

The current code for routing only works for forwarding across ports
without vlans or other upper level devices. That is a very limited use
case and needs to be extended for VLANs and bonds (I have a POC for both).

The API is setup for the extra layers:

struct bpf_fib_lookup {
    ...
    /* input: L3 device index for lookup
     * output: device index from FIB lookup
     */
    __u32   ifindex;
   ...

For bridging, certainly step 1 is the same - define a bpf_fdb_lookup
struct and helper that takes on L2 device index and returns a
<port,vlan> pair.

However, this thread is about bridging with VMs / containers. A viable
solution for this use case MUST handle both vlans and bonds.