bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jakub Sitnicki <jakub@cloudflare.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Networking <netdev@vger.kernel.org>,
	kernel-team <kernel-team@cloudflare.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Marek Majkowski <marek@cloudflare.com>
Subject: Re: [PATCH bpf-next v4 04/16] inet: Run SK_LOOKUP BPF program on socket lookup
Date: Thu, 16 Jul 2020 14:32:45 +0200	[thread overview]
Message-ID: <875zany70y.fsf@cloudflare.com> (raw)
In-Reply-To: <CAEf4BzY0Gc_FH=KUWY3xz6qG8yk+0U0mjXcAx7+39tWt_kQnGQ@mail.gmail.com>

On Thu, Jul 16, 2020 at 04:23 AM CEST, Andrii Nakryiko wrote:
> On Mon, Jul 13, 2020 at 10:47 AM Jakub Sitnicki <jakub@cloudflare.com> wrote:
>>
>> Run a BPF program before looking up a listening socket on the receive path.
>> Program selects a listening socket to yield as result of socket lookup by
>> calling bpf_sk_assign() helper and returning SK_PASS code. Program can
>> revert its decision by assigning a NULL socket with bpf_sk_assign().
>>
>> Alternatively, BPF program can also fail the lookup by returning with
>> SK_DROP, or let the lookup continue as usual with SK_PASS on return, when
>> no socket has not been selected with bpf_sk_assign(). Other return values
>
> you probably meant "no socket has been selected"?

Yes, a typo. Will fix.

>
>> are treated the same as SK_DROP.
>
>
> Why not enforce it instead? Check check_return_code() in verifier.c,
> it's trivial to do it for SK_LOOKUP.

That's a game changer D-: Thank you. This will simplify the prog
runners.

>
>
>>
>> This lets the user match packets with listening sockets freely at the last
>> possible point on the receive path, where we know that packets are destined
>> for local delivery after undergoing policing, filtering, and routing.
>>
>> With BPF code selecting the socket, directing packets destined to an IP
>> range or to a port range to a single socket becomes possible.
>>
>> In case multiple programs are attached, they are run in series in the order
>> in which they were attached. The end result is determined from return codes
>> of all the programs according to following rules:
>>
>>  1. If any program returned SK_PASS and selected a valid socket, the socket
>>     is used as result of socket lookup.
>>  2. If more than one program returned SK_PASS and selected a socket,
>>     last selection takes effect.
>>  3. If any program returned SK_DROP or an invalid return code, and no
>>     program returned SK_PASS and selected a socket, socket lookup fails
>>     with -ECONNREFUSED.
>>  4. If all programs returned SK_PASS and none of them selected a socket,
>>     socket lookup continues to htable-based lookup.
>>
>> Suggested-by: Marek Majkowski <marek@cloudflare.com>
>> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
>> ---
>>
>> Notes:
>>     v4:
>>     - Reduce BPF sk_lookup prog return codes to SK_PASS/SK_DROP. (Lorenz)
>
> your description above still assumes prog can return something besides
> SK_PASS and SK_DROP?

I should have written 'reduce allowed prog return codes'.

>
>>     - Default to drop & warn on illegal return value from BPF prog. (Lorenz)
>>     - Rename netns_bpf_attach_type_enable/disable to _need/unneed. (Lorenz)
>>     - Export bpf_sk_lookup_enabled symbol for CONFIG_IPV6=m (kernel test robot)
>>     - Invert return value from bpf_sk_lookup_run_v4 to true on skip reuseport.
>>     - Move dedicated prog_array runner close to its callers in filter.h.
>>
>>     v3:
>>     - Use a static_key to minimize the hook overhead when not used. (Alexei)
>>     - Adapt for running an array of attached programs. (Alexei)
>>     - Adapt for optionally skipping reuseport selection. (Martin)
>>
>>  include/linux/filter.h     | 102 +++++++++++++++++++++++++++++++++++++
>>  kernel/bpf/net_namespace.c |  32 +++++++++++-
>>  net/core/filter.c          |   3 ++
>>  net/ipv4/inet_hashtables.c |  31 +++++++++++
>>  4 files changed, 167 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/filter.h b/include/linux/filter.h
>> index 380746f47fa1..b9ad0fdabca5 100644
>> --- a/include/linux/filter.h
>> +++ b/include/linux/filter.h
>> @@ -1295,4 +1295,106 @@ struct bpf_sk_lookup_kern {
>>         bool            no_reuseport;
>>  };
>>
>> +extern struct static_key_false bpf_sk_lookup_enabled;
>> +
>> +/* Runners for BPF_SK_LOOKUP programs to invoke on socket lookup.
>> + *
>> + * Allowed return values for a BPF SK_LOOKUP program are SK_PASS and
>> + * SK_DROP. Any other return value is treated as SK_DROP. Their
>> + * meaning is as follows:
>> + *
>> + *  SK_PASS && ctx.selected_sk != NULL: use selected_sk as lookup result
>> + *  SK_PASS && ctx.selected_sk == NULL: continue to htable-based socket lookup
>> + *  SK_DROP                           : terminate lookup with -ECONNREFUSED
>> + *
>> + * This macro aggregates return values and selected sockets from
>> + * multiple BPF programs according to following rules:
>> + *
>> + *  1. If any program returned SK_PASS and a non-NULL ctx.selected_sk,
>> + *     macro result is SK_PASS and last ctx.selected_sk is used.
>> + *  2. If any program returned non-SK_PASS return value,
>> + *     macro result is the last non-SK_PASS return value.
>> + *  3. Otherwise result is SK_PASS and ctx.selected_sk is NULL.
>> + *
>> + * Caller must ensure that the prog array is non-NULL, and that the
>> + * array as well as the programs it contains remain valid.
>> + */
>> +#define BPF_PROG_SK_LOOKUP_RUN_ARRAY(array, ctx, func)                 \
>> +       ({                                                              \
>> +               struct bpf_sk_lookup_kern *_ctx = &(ctx);               \
>> +               struct bpf_prog_array_item *_item;                      \
>> +               struct sock *_selected_sk;                              \
>> +               struct bpf_prog *_prog;                                 \
>> +               u32 _ret, _last_ret;                                    \
>> +               bool _no_reuseport;                                     \
>> +                                                                       \
>> +               migrate_disable();                                      \
>> +               _last_ret = SK_PASS;                                    \
>> +               _selected_sk = NULL;                                    \
>> +               _no_reuseport = false;                                  \
>
> these three could be moved before migrate_disable(), or even better
> just initialize corresponding variables above?

I was torn between keeping all info needed to read through the loop
close to it and keeping the critical section tight. I can move it up.

>
>
>> +               _item = &(array)->items[0];                             \
>> +               while ((_prog = READ_ONCE(_item->prog))) {              \
>> +                       /* restore most recent selection */             \
>> +                       _ctx->selected_sk = _selected_sk;               \
>> +                       _ctx->no_reuseport = _no_reuseport;             \
>> +                                                                       \
>> +                       _ret = func(_prog, _ctx);                       \
>> +                       if (_ret == SK_PASS) {                          \
>> +                               /* remember last non-NULL socket */     \
>> +                               if (_ctx->selected_sk) {                \
>> +                                       _selected_sk = _ctx->selected_sk;       \
>> +                                       _no_reuseport = _ctx->no_reuseport;     \
>> +                               }                                       \
>> +                       } else {                                        \
>> +                               /* remember last non-PASS ret code */   \
>> +                               _last_ret = _ret;                       \
>> +                       }                                               \
>> +                       _item++;                                        \
>> +               }                                                       \
>> +               _ctx->selected_sk = _selected_sk;                       \
>> +               _ctx->no_reuseport = _no_reuseport;                     \
>> +               migrate_enable();                                       \
>> +               _ctx->selected_sk ? SK_PASS : _last_ret;                \
>> +        })
>> +
>
> [...]

  reply	other threads:[~2020-07-16 12:32 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-13 17:46 [PATCH bpf-next v4 00/16] Run a " Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 01/16] bpf, netns: Handle multiple link attachments Jakub Sitnicki
2020-07-15 21:30   ` Andrii Nakryiko
2020-07-13 17:46 ` [PATCH bpf-next v4 02/16] bpf: Introduce SK_LOOKUP program type with a dedicated attach point Jakub Sitnicki
2020-07-16  1:41   ` Andrii Nakryiko
2020-07-16 12:17     ` Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 03/16] inet: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-16  1:44   ` Andrii Nakryiko
2020-07-13 17:46 ` [PATCH bpf-next v4 04/16] inet: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-16  2:23   ` Andrii Nakryiko
2020-07-16 12:32     ` Jakub Sitnicki [this message]
2020-07-13 17:46 ` [PATCH bpf-next v4 05/16] inet6: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 06/16] inet6: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 07/16] udp: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 08/16] udp: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 09/16] udp6: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 10/16] udp6: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 11/16] bpf: Sync linux/bpf.h to tools/ Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 12/16] libbpf: Add support for SK_LOOKUP program type Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 13/16] tools/bpftool: Add name mappings for SK_LOOKUP prog and attach type Jakub Sitnicki
2020-07-16  2:10   ` Andrii Nakryiko
2020-07-13 17:46 ` [PATCH bpf-next v4 14/16] selftests/bpf: Add verifier tests for bpf_sk_lookup context access Jakub Sitnicki
2020-07-16  2:13   ` Andrii Nakryiko
2020-07-13 17:46 ` [PATCH bpf-next v4 15/16] selftests/bpf: Rename test_sk_lookup_kern.c to test_ref_track_kern.c Jakub Sitnicki
2020-07-13 17:46 ` [PATCH bpf-next v4 16/16] selftests/bpf: Tests for BPF_SK_LOOKUP attach point Jakub Sitnicki
2020-07-16  2:19   ` Andrii Nakryiko
2020-07-16  2:25 ` [PATCH bpf-next v4 00/16] Run a BPF program on socket lookup Andrii Nakryiko

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=875zany70y.fsf@cloudflare.com \
    --to=jakub@cloudflare.com \
    --cc=andrii.nakryiko@gmail.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=kernel-team@cloudflare.com \
    --cc=kuba@kernel.org \
    --cc=marek@cloudflare.com \
    --cc=netdev@vger.kernel.org \
    --subject='Re: [PATCH bpf-next v4 04/16] inet: Run SK_LOOKUP BPF program on socket lookup' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).