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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Song Liu <songliubraving@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <ast@kernel.org>, Martin Lau <kafai@fb.com>,
	Yonghong Song <yhs@fb.com>,
	Marek Majkowski <marek@cloudflare.com>,
	Lorenz Bauer <lmb@cloudflare.com>,
	David Miller <davem@davemloft.net>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	"netdev\@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf\@vger.kernel.org" <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through chain calls
Date: Thu, 03 Oct 2019 09:59:55 +0200	[thread overview]
Message-ID: <87a7aiqmx0.fsf@toke.dk> (raw)
In-Reply-To: <B1372BF2-E0A2-4D01-B012-181B108CF994@fb.com>

Song Liu <songliubraving@fb.com> writes:

>> On Oct 2, 2019, at 12:23 PM, Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>> 
>> Song Liu <songliubraving@fb.com> writes:
>> 
>>>> On Oct 2, 2019, at 6:30 AM, Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>>> 
>>>> This series adds support for executing multiple XDP programs on a single
>>>> interface in sequence, through the use of chain calls, as discussed at the Linux
>>>> Plumbers Conference last month:
>>>> 
>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__linuxplumbersconf.org_event_4_contributions_460_&d=DwIDaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YXqqHTC51zXBviPBEk55y-fQjFQwcXWFlH0IoOqm2KU&s=NF4w3eSPmNhSpJr1-0FLqqlqfgEV8gsCQb9YqWQ9p-k&e= 
>>>> 
>>>> # HIGH-LEVEL IDEA
>>>> 
>>>> The basic idea is to express the chain call sequence through a special map type,
>>>> which contains a mapping from a (program, return code) tuple to another program
>>>> to run in next in the sequence. Userspace can populate this map to express
>>>> arbitrary call sequences, and update the sequence by updating or replacing the
>>>> map.
>>>> 
>>>> The actual execution of the program sequence is done in bpf_prog_run_xdp(),
>>>> which will lookup the chain sequence map, and if found, will loop through calls
>>>> to BPF_PROG_RUN, looking up the next XDP program in the sequence based on the
>>>> previous program ID and return code.
>>>> 
>>>> An XDP chain call map can be installed on an interface by means of a new netlink
>>>> attribute containing an fd pointing to a chain call map. This can be supplied
>>>> along with the XDP prog fd, so that a chain map is always installed together
>>>> with an XDP program.
>>> 
>>> Interesting work!
>>> 
>>> Quick question: can we achieve the same by adding a "retval to
>>> call_tail_next" map to each program?
>> 
>> Hmm, that's an interesting idea; I hadn't thought of that. As long as
>> that map can be manipulated outside of the program itself, it may work.
>> I wonder how complex it gets to modify the call sequence, though; say
>> you want to change A->B->C to A->C->B - how do you do that without
>> interrupting the sequence while you're modifying things? Or is it OK if
>> that is not possible?
>
> We can always load another copy of B and C, say D == B, and E == C. And 
> make it A->E->D. 

Yes, thinking some more about this I don't think it's actually a
problem. I'll go prototype something...

      reply	other threads:[~2019-10-03  8:00 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-02 13:30 [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through chain calls Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 1/9] hashtab: Add new bpf_map_fd_put_value op Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 2/9] xdp: Add new xdp_chain_map type for specifying XDP call sequences Toke Høiland-Jørgensen
2019-10-02 15:50   ` Lorenz Bauer
2019-10-02 18:25     ` Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 3/9] xdp: Support setting and getting device chain map Toke Høiland-Jørgensen
2019-10-02 15:50   ` Lorenz Bauer
2019-10-02 18:32     ` Toke Høiland-Jørgensen
2019-10-02 18:07   ` kbuild test robot
2019-10-02 18:29   ` kbuild test robot
2019-10-02 13:30 ` [PATCH bpf-next 4/9] xdp: Implement chain call logic to support multiple programs on one interface Toke Høiland-Jørgensen
2019-10-02 17:33   ` kbuild test robot
2019-10-02 17:53   ` kbuild test robot
2019-10-02 13:30 ` [PATCH bpf-next 5/9] tools/include/uapi: Add XDP chain map definitions Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 6/9] tools/libbpf_probes: Add support for xdp_chain map type Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 7/9] bpftool: Add definitions " Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 8/9] libbpf: Add support for setting and getting XDP chain maps Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 9/9] selftests: Add tests for XDP chain calls Toke Høiland-Jørgensen
2019-10-02 15:10 ` [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through " Alan Maguire
2019-10-02 15:33   ` Toke Høiland-Jørgensen
2019-10-02 16:34     ` John Fastabend
2019-10-02 18:33       ` Toke Høiland-Jørgensen
2019-10-02 20:34         ` John Fastabend
2019-10-03  7:48           ` Toke Høiland-Jørgensen
2019-10-03 10:09             ` Jesper Dangaard Brouer
2019-10-03 19:45               ` John Fastabend
2019-10-02 16:35 ` Lorenz Bauer
2019-10-02 18:54   ` Toke Høiland-Jørgensen
2019-10-02 16:43 ` John Fastabend
2019-10-02 19:09   ` Toke Høiland-Jørgensen
2019-10-02 19:15   ` Daniel Borkmann
2019-10-02 19:29     ` Toke Høiland-Jørgensen
2019-10-02 19:46     ` Alexei Starovoitov
2019-10-03  7:58       ` Toke Høiland-Jørgensen
2019-10-02 18:38 ` Song Liu
2019-10-02 18:54   ` Song Liu
2019-10-02 19:25     ` Toke Høiland-Jørgensen
2019-10-03  8:53       ` Jesper Dangaard Brouer
2019-10-03 14:03         ` Alexei Starovoitov
2019-10-03 14:33           ` Toke Høiland-Jørgensen
2019-10-03 14:53             ` Edward Cree
2019-10-03 18:49               ` Jesper Dangaard Brouer
2019-10-03 19:35               ` John Fastabend
2019-10-04  8:09                 ` Toke Høiland-Jørgensen
2019-10-04 10:34                   ` Edward Cree
2019-10-04 15:58                     ` Lorenz Bauer
2019-10-07 16:43                       ` Edward Cree
2019-10-07 17:12                         ` Lorenz Bauer
2019-10-07 19:21                           ` Edward Cree
2019-10-07 21:01                         ` Alexei Starovoitov
2019-10-02 19:23   ` Toke Høiland-Jørgensen
2019-10-02 19:49     ` Song Liu
2019-10-03  7:59       ` Toke Høiland-Jørgensen [this message]

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