Previous commit adjusted kernel uapi for map
element bpf iterator. This patch adjusted libbpf API
due to uapi change. bpftool and bpf_iter selftests
are also changed accordingly.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200805055058.1457623-1-yhs@fb.com

Add low-level bpf_link_detach() API. Also add higher-level bpf_link__detach()
one.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200731182830.286260-3-andriin@fb.com

Sync UAPI header and add support for using bpf_link-based XDP attachment.
Make xdp/ prog type set expected attach type. Kernel didn't enforce
attach_type for XDP programs before, so there is no backwards compatiblity
issues there.

Also fix section_names selftest to recognize that xdp prog types now have
expected attach type.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-8-andriin@fb.com

Add map_fd to bpf_iter_attach_opts and flags to
bpf_link_create_opts. Later on, bpftool or selftest
will be able to create a bpf map element iterator
by passing map_fd to the kernel during link
creation time.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184117.590673-1-yhs@fb.com

Make libbpf aware of the newly added program type, and assign it a
section name.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200717103536.397595-13-jakub@cloudflare.com

Currently, bpf_object__load() (and by induction skeleton's load), will always
attempt to prepare, relocate, and load into kernel every single BPF program
found inside the BPF object file. This is often convenient and the right thing
to do and what users expect.

But there are plenty of cases (especially with BPF development constantly
picking up the pace), where BPF application is intended to work with old
kernels, with potentially reduced set of features. But on kernels supporting
extra features, it would like to take a full advantage of them, by employing
extra BPF program. This could be a choice of using fentry/fexit over
kprobe/kretprobe, if kernel is recent enough and is built with BTF. Or BPF
program might be providing optimized bpf_iter-based solution that user-space
might want to use, whenever available. And so on.

With libbpf and BPF CO-RE in particular, it's advantageous to not have to
maintain two separate BPF object files to achieve this. So to enable such use
cases, this patch adds ability to request not auto-loading chosen BPF
programs. In such case, libbpf won't attempt to perform relocations (which
might fail due to old kernel), won't try to resolve BTF types for
BTF-aware (tp_btf/fentry/fexit/etc) program types, because BTF might not be
present, and so on. Skeleton will also automatically skip auto-attachment step
for such not loaded BPF programs.

Overall, this feature allows to simplify development and deployment of
real-world BPF applications with complicated compatibility requirements.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200625232629.3444003-2-andriin@fb.com

Add a bunch of getter for various aspects of BPF map. Some of these attribute
(e.g., key_size, value_size, type, etc) are available right now in struct
bpf_map_def, but this patch adds getter allowing to fetch them individually.
bpf_map_def approach isn't very scalable, when ABI stability requirements are
taken into account. It's much easier to extend libbpf and add support for new
features, when each aspect of BPF map has separate getter/setter.

Getters follow the common naming convention of not explicitly having "get" in
its name: bpf_map__type() returns map type, bpf_map__key_size() returns
key_size. Setters, though, explicitly have set in their name:
bpf_map__set_type(), bpf_map__set_key_size().

This patch ensures we now have a getter and a setter for the following
map attributes:
  - type;
  - max_entries;
  - map_flags;
  - numa_node;
  - key_size;
  - value_size;
  - ifindex.

bpf_map__resize() enforces unnecessary restriction of max_entries > 0. It is
unnecessary, because libbpf actually supports zero max_entries for some cases
(e.g., for PERF_EVENT_ARRAY map) and treats it specially during map creation
time. To allow setting max_entries=0, new bpf_map__set_max_entries() setter is
added. bpf_map__resize()'s behavior is preserved for backwards compatibility
reasons.

Map ifindex getter is added as well. There is a setter already, but no
corresponding getter. Fix this assymetry as well. bpf_map__set_ifindex()
itself is converted from void function into error-returning one, similar to
other setters. The only error returned right now is -EBUSY, if BPF map is
already loaded and has corresponding FD.

One lacking attribute with no ability to get/set or even specify it
declaratively is numa_node. This patch fixes this gap and both adds
programmatic getter/setter, as well as adds support for numa_node field in
BTF-defined map.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20200621062112.3006313-1-andriin@fb.com

Add bpf_program__attach_nets(), which uses LINK_CREATE subcommand to create
an FD-based kernel bpf_link, for attach types tied to network namespace,
that is BPF_FLOW_DISSECTOR for the moment.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200531082846.2117903-7-jakub@cloudflare.com

Declaring and instantiating BPF ring buffer doesn't require any changes to
libbpf, as it's just another type of maps. So using existing BTF-defined maps
syntax with __uint(type, BPF_MAP_TYPE_RINGBUF) and __uint(max_elements,
<size-of-ring-buf>) is all that's necessary to create and use BPF ring buffer.

This patch adds BPF ring buffer consumer to libbpf. It is very similar to
perf_buffer implementation in terms of API, but also attempts to fix some
minor problems and inconveniences with existing perf_buffer API.

ring_buffer support both single ring buffer use case (with just using
ring_buffer__new()), as well as allows to add more ring buffers, each with its
own callback and context. This allows to efficiently poll and consume
multiple, potentially completely independent, ring buffers, using single
epoll instance.

The latter is actually a problem in practice for applications
that are using multiple sets of perf buffers. They have to create multiple
instances for struct perf_buffer and poll them independently or in a loop,
each approach having its own problems (e.g., inability to use a common poll
timeout). struct ring_buffer eliminates this problem by aggregating many
independent ring buffer instances under the single "ring buffer manager".

Second, perf_buffer's callback can't return error, so applications that need
to stop polling due to error in data or data signalling the end, have to use
extra mechanisms to signal that polling has to stop. ring_buffer's callback
can return error, which will be passed through back to user code and can be
acted upon appropariately.

Two APIs allow to consume ring buffer data:
  - ring_buffer__poll(), which will wait for data availability notification
    and will consume data only from reported ring buffer(s); this API allows
    to efficiently use resources by reading data only when it becomes
    available;
  - ring_buffer__consume(), will attempt to read new records regardless of
    data availablity notification sub-system. This API is useful for cases
    when lowest latency is required, in expense of burning CPU resources.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200529075424.3139988-3-andriin@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This new API, perf_buffer__consume, can be used as follows:

- When you have a perf ring where wakeup_events is higher than 1,
  and you have remaining data in the rings you would like to pull
  out on exit (or maybe based on a timeout).

- For low latency cases where you burn a CPU that constantly polls
  the queues.

Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/159048487929.89441.7465713173442594608.stgit@ebuild
Signed-off-by: Alexei Starovoitov <ast@kernel.org>