From: Vlad Buslov <vladbu@nvidia.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>, <bpf@vger.kernel.org>,
<brouer@redhat.com>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>, Shuah Khan <shuah@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"Jakub Kicinski" <kuba@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
<linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
<linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH bpf-next 3/5] libbpf: add low level TC-BPF API
Date: Mon, 29 Mar 2021 15:49:58 +0300 [thread overview]
Message-ID: <ygnheefygm4p.fsf@nvidia.com> (raw)
In-Reply-To: <87ft0eta27.fsf@toke.dk>
On Mon 29 Mar 2021 at 15:32, Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> Vlad Buslov <vladbu@nvidia.com> writes:
>
>> On Thu 25 Mar 2021 at 14:00, Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>>> This adds functions that wrap the netlink API used for adding,
>>> manipulating, and removing filters and actions. These functions operate
>>> directly on the loaded prog's fd, and return a handle to the filter and
>>> action using an out parameter (id for tc_cls, and index for tc_act).
>>>
>>> The basic featureset is covered to allow for attaching, manipulation of
>>> properties, and removal of filters and actions. Some additional features
>>> like TCA_BPF_POLICE and TCA_RATE for tc_cls have been omitted. These can
>>> added on top later by extending the bpf_tc_cls_opts struct.
>>>
>>> Support for binding actions directly to a classifier by passing them in
>>> during filter creation has also been omitted for now. These actions
>>> have an auto clean up property because their lifetime is bound to the
>>> filter they are attached to. This can be added later, but was omitted
>>> for now as direct action mode is a better alternative to it.
>>>
>>> An API summary:
>>>
>>> The BPF TC-CLS API
>>>
>>> bpf_tc_act_{attach, change, replace}_{dev, block} may be used to attach,
>>> change, and replace SCHED_CLS bpf classifiers. Separate set of functions
>>> are provided for network interfaces and shared filter blocks.
>>>
>>> bpf_tc_cls_detach_{dev, block} may be used to detach existing SCHED_CLS
>>> filter. The bpf_tc_cls_attach_id object filled in during attach,
>>> change, or replace must be passed in to the detach functions for them to
>>> remove the filter and its attached classififer correctly.
>>>
>>> bpf_tc_cls_get_info is a helper that can be used to obtain attributes
>>> for the filter and classififer. The opts structure may be used to
>>> choose the granularity of search, such that info for a specific filter
>>> corresponding to the same loaded bpf program can be obtained. By
>>> default, the first match is returned to the user.
>>>
>>> Examples:
>>>
>>> struct bpf_tc_cls_attach_id id = {};
>>> struct bpf_object *obj;
>>> struct bpf_program *p;
>>> int fd, r;
>>>
>>> obj = bpf_object_open("foo.o");
>>> if (IS_ERR_OR_NULL(obj))
>>> return PTR_ERR(obj);
>>>
>>> p = bpf_object__find_program_by_title(obj, "classifier");
>>> if (IS_ERR_OR_NULL(p))
>>> return PTR_ERR(p);
>>>
>>> if (bpf_object__load(obj) < 0)
>>> return -1;
>>>
>>> fd = bpf_program__fd(p);
>>>
>>> r = bpf_tc_cls_attach_dev(fd, if_nametoindex("lo"),
>>> BPF_TC_CLSACT_INGRESS, ETH_P_IP,
>>> NULL, &id);
>>> if (r < 0)
>>> return r;
>>>
>>> ... which is roughly equivalent to (after clsact qdisc setup):
>>> # tc filter add dev lo ingress bpf obj /home/kkd/foo.o sec classifier
>>>
>>> If a user wishes to modify existing options on an attached filter, the
>>> bpf_tc_cls_change_{dev, block} API may be used. Parameters like
>>> chain_index, priority, and handle are ignored in the bpf_tc_cls_opts
>>> struct as they cannot be modified after attaching a filter.
>>>
>>> Example:
>>>
>>> /* Optional parameters necessary to select the right filter */
>>> DECLARE_LIBBPF_OPTS(bpf_tc_cls_opts, opts,
>>> .handle = id.handle,
>>> .priority = id.priority,
>>> .chain_index = id.chain_index)
>>> /* Turn on direct action mode */
>>> opts.direct_action = true;
>>> r = bpf_tc_cls_change_dev(fd, id.ifindex, id.parent_id,
>>> id.protocol, &opts, &id);
>>> if (r < 0)
>>> return r;
>>>
>>> /* Verify that the direct action mode has been set */
>>> struct bpf_tc_cls_info info = {};
>>> r = bpf_tc_cls_get_info_dev(fd, id.ifindex, id.parent_id,
>>> id.protocol, &opts, &info);
>>> if (r < 0)
>>> return r;
>>>
>>> assert(info.bpf_flags & TCA_BPF_FLAG_ACT_DIRECT);
>>>
>>> This would be roughly equivalent to doing:
>>> # tc filter change dev lo egress prio <p> handle <h> bpf obj /home/kkd/foo.o section classifier da
>>>
>>> ... except a new bpf program will be loaded and replace existing one.
>>>
>>> If a user wishes to either replace an existing filter, or create a new
>>> one with the same properties, they can use bpf_tc_cls_replace_dev. The
>>> benefit of bpf_tc_cls_change is that it fails if no matching filter
>>> exists.
>>>
>>> The BPF TC-ACT API
>>>
>>> bpf_tc_act_{attach, replace} may be used to attach and replace already
>>> attached SCHED_ACT actions. Passing an index of 0 has special meaning,
>>> in that an index will be automatically chosen by the kernel. The index
>>> chosen by the kernel is the return value of these functions in case of
>>> success.
>>>
>>> bpf_tc_act_detach may be used to detach a SCHED_ACT action prog
>>> identified by the index parameter. The index 0 again has a special
>>> meaning, in that passing it will flush all existing SCHED_ACT actions
>>> loaded using the ACT API.
>>>
>>> bpf_tc_act_get_info is a helper to get the required attributes of a
>>> loaded program to be able to manipulate it futher, by passing them
>>> into the aforementioned functions.
>>>
>>> Example:
>>>
>>> struct bpf_object *obj;
>>> struct bpf_program *p;
>>> __u32 index;
>>> int fd, r;
>>>
>>> obj = bpf_object_open("foo.o");
>>> if (IS_ERR_OR_NULL(obj))
>>> return PTR_ERR(obj);
>>>
>>> p = bpf_object__find_program_by_title(obj, "action");
>>> if (IS_ERR_OR_NULL(p))
>>> return PTR_ERR(p);
>>>
>>> if (bpf_object__load(obj) < 0)
>>> return -1;
>>>
>>> fd = bpf_program__fd(p);
>>>
>>> r = bpf_tc_act_attach(fd, NULL, &index);
>>> if (r < 0)
>>> return r;
>>>
>>> if (bpf_tc_act_detach(index))
>>> return -1;
>>>
>>> ... which is equivalent to the following sequence:
>>> tc action add action bpf obj /home/kkd/foo.o sec action
>>> tc action del action bpf index <idx>
>>
>> How do you handle the locking here? Please note that while
>> RTM_{NEW|GET|DEL}FILTER API has been refactored to handle its own
>> locking internally (and registered with RTNL_FLAG_DOIT_UNLOCKED flag),
>> RTM_{NEW|GET|DEL}ACTION API still expects to be called with rtnl lock
>> taken.
>
> Huh, locking? This is all userspace code that uses the netlink API...
>
> -Toke
Thanks for the clarification. I'm not familiar with libbpf internals and
it wasn't obvious to me that this functionality is not for creating
classifiers/actions from BPF program executing in kernel-space.
next prev parent reply other threads:[~2021-03-29 12:51 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 11:59 [PATCH bpf-next 0/5] libbpf: Add TC-BPF API Kumar Kartikeya Dwivedi
2021-03-25 11:59 ` [PATCH bpf-next 1/5] tools pkt_cls.h: sync with kernel sources Kumar Kartikeya Dwivedi
2021-03-26 23:25 ` Andrii Nakryiko
2021-03-27 3:54 ` Kumar Kartikeya Dwivedi
2021-03-27 3:58 ` Andrii Nakryiko
2021-03-25 12:00 ` [PATCH bpf-next 2/5] libbpf: add helpers for preparing netlink attributes Kumar Kartikeya Dwivedi
2021-03-26 23:52 ` Andrii Nakryiko
2021-03-25 12:00 ` [PATCH bpf-next 3/5] libbpf: add low level TC-BPF API Kumar Kartikeya Dwivedi
2021-03-28 4:42 ` Andrii Nakryiko
2021-03-28 8:11 ` Kumar Kartikeya Dwivedi
2021-03-30 20:39 ` Andrii Nakryiko
2021-03-30 21:11 ` Toke Høiland-Jørgensen
2021-03-31 9:32 ` Kumar Kartikeya Dwivedi
2021-03-30 21:25 ` Daniel Borkmann
2021-03-30 23:30 ` Alexei Starovoitov
2021-03-31 9:44 ` Kumar Kartikeya Dwivedi
2021-04-02 0:19 ` Daniel Borkmann
2021-04-02 15:27 ` Kumar Kartikeya Dwivedi
2021-04-02 18:32 ` Alexei Starovoitov
2021-04-02 19:08 ` Kumar Kartikeya Dwivedi
2021-04-03 17:47 ` Alexei Starovoitov
2021-04-05 17:27 ` Andrii Nakryiko
2021-04-06 10:06 ` Toke Høiland-Jørgensen
2021-04-14 0:47 ` Andrii Nakryiko
2021-04-14 10:58 ` Toke Høiland-Jørgensen
2021-04-14 22:22 ` Andrii Nakryiko
2021-04-14 22:51 ` Toke Høiland-Jørgensen
2021-04-14 23:19 ` Andrii Nakryiko
2021-04-14 23:32 ` Daniel Borkmann
2021-04-14 23:58 ` Andrii Nakryiko
2021-04-15 22:10 ` Daniel Borkmann
2021-04-15 22:22 ` Andrii Nakryiko
2021-04-15 23:10 ` Daniel Borkmann
2021-04-16 9:01 ` Toke Høiland-Jørgensen
2021-04-15 15:57 ` Toke Høiland-Jørgensen
2021-04-15 21:09 ` Andrii Nakryiko
2021-04-05 17:21 ` Andrii Nakryiko
2021-04-06 19:05 ` Kumar Kartikeya Dwivedi
2021-03-31 9:51 ` Toke Høiland-Jørgensen
2021-03-29 11:46 ` Vlad Buslov
2021-03-29 12:32 ` Toke Høiland-Jørgensen
2021-03-29 12:49 ` Vlad Buslov [this message]
2021-03-25 12:00 ` [PATCH bpf-next 4/5] libbpf: add high " Kumar Kartikeya Dwivedi
2021-03-25 12:00 ` [PATCH bpf-next 5/5] libbpf: add selftests for " Kumar Kartikeya Dwivedi
2021-03-27 2:15 ` Alexei Starovoitov
2021-03-27 15:17 ` Toke Høiland-Jørgensen
2021-03-29 1:26 ` Alexei Starovoitov
2021-03-29 1:45 ` Kumar Kartikeya Dwivedi
2021-03-28 4:32 ` Andrii Nakryiko
2021-03-29 1:40 ` Alexei Starovoitov
2021-03-29 2:38 ` Andrii Nakryiko
2021-03-30 3:28 ` Alexei Starovoitov
2021-03-30 20:28 ` Andrii Nakryiko
2021-03-30 23:27 ` Alexei Starovoitov
2021-03-29 9:56 ` Toke Høiland-Jørgensen
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