- 01 Jun, 2020 40 commits
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Alexei Starovoitov authored
Jakub Sitnicki says: ==================== One of the pieces of feedback from recent review of BPF hooks for socket lookup [0] was that new program types should use bpf_link-based attachment. This series introduces new bpf_link type for attaching to network namespace. All link operations are supported. Errors returned from ops follow cgroup example. Patch 4 description goes into error semantics. The major change in v2 is a switch away from RCU to mutex-only synchronization. Andrii pointed out that it is not needed, and it makes sense to keep locking straightforward. Also, there were a couple of bugs in update_prog and fill_info initial implementation, one picked up by kbuild. Those are now fixed. Tests have been extended to cover them. Full changelog below. Series is organized as so: Patches 1-3 prepare a space in struct net to keep state for attached BPF programs, and massage the code in flow_dissector to make it attach type agnostic, to finally move it under kernel/bpf/. Patch 4, the most important one, introduces new bpf_link link type for attaching to network namespace. Patch 5 unifies the update error (ENOLINK) between BPF cgroup and netns. Patches 6-8 make libbpf and bpftool aware of the new link type. Patches 9-12 Add and extend tests to check that link low- and high-level API for operating on links to netns works as intended. Thanks to Alexei, Andrii, Lorenz, Marek, and Stanislav for feedback. -jkbs [0] https://lore.kernel.org/bpf/20200511185218.1422406-1-jakub@cloudflare.com/ Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> Cc: Lorenz Bauer <lmb@cloudflare.com> Cc: Marek Majkowski <marek@cloudflare.com> Cc: Stanislav Fomichev <sdf@google.com> v1 -> v2: - Switch to mutex-only synchronization. Don't rely on RCU grace period guarantee when accessing struct net from link release / update / fill_info, and when accessing bpf_link from pernet pre_exit callback. (Andrii) - Drop patch 1, no longer needed with mutex-only synchronization. - Don't leak uninitialized variable contents from fill_info callback when link is in defunct state. (kbuild) - Make fill_info treat the link as defunct (i.e. no attached netns) when struct net refcount is 0, but link has not been yet auto-detached. - Add missing BPF_LINK_TYPE define in bpf_types.h for new link type. - Fix link update_prog callback to update the prog that will run, and not just the link itself. - Return EEXIST on prog attach when link already exists, and on link create when prog is already attached directly. (Andrii) - Return EINVAL on prog detach when link is attached. (Andrii) - Fold __netns_bpf_link_attach into its only caller. (Stanislav) - Get rid of a wrapper around container_of() (Andrii) - Use rcu_dereference_protected instead of rcu_access_pointer on update-side. (Stanislav) - Make return-on-success from netns_bpf_link_create less confusing. (Andrii) - Adapt bpf_link for cgroup to return ENOLINK when updating a defunct link. (Andrii, Alexei) - Order new exported symbols in libbpf.map alphabetically (Andrii) - Keep libbpf's "failed to attach link" warning message clear as to what we failed to attach to (cgroup vs netns). (Andrii) - Extract helpers for printing link attach type. (bpftool, Andrii) - Switch flow_dissector tests to BPF skeleton and extend them to exercise link-based flow dissector attachment. (Andrii) - Harden flow dissector attachment tests with prog query checks after prog attach/detach, or link create/update/close. - Extend flow dissector tests to cover fill_info for defunct links. - Rebase onto recent bpf-next ==================== Signed-off-by:
Alexei Starovoitov <ast@kernel.org>
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Jakub Sitnicki authored
Extend the existing flow_dissector test case to run tests once using direct prog attachments, and then for the second time using indirect attachment via link. The intention is to exercises the newly added high-level API for attaching programs to network namespace with links (bpf_program__attach_netns). Signed-off-by:
Jakub Sitnicki <jakub@cloudflare.com> Signed-off-by:
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Jakub Sitnicki authored
Switch flow dissector test setup from custom BPF object loader to BPF skeleton to save boilerplate and prepare for testing higher-level API for attaching flow dissector with bpf_link. To avoid depending on program order in the BPF object when populating the flow dissector PROG_ARRAY map, change the program section names to contain the program index into the map. This follows the example set by tailcall tests. Signed-off-by:
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Jakub Sitnicki authored
test_flow_dissector leaves a TAP device after it's finished, potentially interfering with other tests that will run after it. Fix it by closing the TAP descriptor on cleanup. Fixes: 0905beec ("selftests/bpf: run flow dissector tests in skb-less mode") Signed-off-by:
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Jakub Sitnicki authored
Extend the existing test case for flow dissector attaching to cover: - link creation, - link updates, - link info querying, - mixing links with direct prog attachment. Signed-off-by:
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Jakub Sitnicki authored
Make `bpf link show` aware of new link type, that is links attached to netns. When listing netns-attached links, display netns inode number as its identifier and link attach type. Sample session: # readlink /proc/self/ns/net net:[4026532251] # bpftool prog show 357: flow_dissector tag a04f5eef06a7f555 gpl loaded_at 2020-05-30T16:53:51+0200 uid 0 xlated 16B jited 37B memlock 4096B 358: flow_dissector tag a04f5eef06a7f555 gpl loaded_at 2020-05-30T16:53:51+0200 uid 0 xlated 16B jited 37B memlock 4096B # bpftool link show 108: netns prog 357 netns_ino 4026532251 attach_type flow_dissector # bpftool link -jp show [{ "id": 108, "type": "netns", "prog_id": 357, "netns_ino": 4026532251, "attach_type": "flow_dissector" } ] (... after netns is gone ...) # bpftool link show 108: netns prog 357 netns_ino 0 attach_type flow_dissector # bpftool link -jp show [{ "id": 108, "type": "netns", "prog_id": 357, "netns_ino": 0, "attach_type": "flow_dissector" } ] Signed-off-by: -
Jakub Sitnicki authored
Code for printing link attach_type is duplicated in a couple of places, and likely will be duplicated for future link types as well. Create helpers to prevent duplication. Suggested-by:
Andrii Nakryiko <andriin@fb.com> Signed-off-by:
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Jakub Sitnicki authored
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:
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Jakub Sitnicki authored
Failure to update a bpf_link because it has been auto-detached by a dying cgroup currently results in EINVAL error, even though the arguments passed to bpf() syscall are not wrong. bpf_links attaching to netns in this case will return ENOLINK, which carries the message that the link is no longer attached to anything. Change cgroup bpf_links to do the same to keep the uAPI errors consistent. Fixes: 0c991ebc ("bpf: Implement bpf_prog replacement for an active bpf_cgroup_link") Suggested-by:
Lorenz Bauer <lmb@cloudflare.com> Signed-off-by:
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Jakub Sitnicki authored
Extend bpf() syscall subcommands that operate on bpf_link, that is LINK_CREATE, LINK_UPDATE, OBJ_GET_INFO, to accept attach types tied to network namespaces (only flow dissector at the moment). Link-based and prog-based attachment can be used interchangeably, but only one can exist at a time. Attempts to attach a link when a prog is already attached directly, and the other way around, will be met with -EEXIST. Attempts to detach a program when link exists result in -EINVAL. Attachment of multiple links of same attach type to one netns is not supported with the intention to lift the restriction when a use-case presents itself. Because of that link create returns -E2BIG when trying to create another netns link, when one already exists. Link-based attachments to netns don't keep a netns alive by holding a ref to it. Instead links get auto-detached from netns when the latter is being destroyed, using a pernet pre_exit callback. When auto-detached, link lives in defunct state as long there are open FDs for it. -ENOLINK is returned if a user tries to update a defunct link. Because bpf_link to netns doesn't hold a ref to struct net, special care is taken when releasing, updating, or filling link info. The netns might be getting torn down when any of these link operations are in progress. That is why auto-detach and update/release/fill_info are synchronized by the same mutex. Also, link ops have to always check if auto-detach has not happened yet and if netns is still alive (refcnt > 0). Signed-off-by:
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Jakub Sitnicki authored
Move functions to manage BPF programs attached to netns that are not specific to flow dissector to a dedicated module named bpf/net_namespace.c. The set of functions will grow with the addition of bpf_link support for netns attached programs. This patch prepares ground by creating a place for it. This is a code move with no functional changes intended. Signed-off-by:
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Jakub Sitnicki authored
In order to: (1) attach more than one BPF program type to netns, or (2) support attaching BPF programs to netns with bpf_link, or (3) support multi-prog attach points for netns we will need to keep more state per netns than a single pointer like we have now for BPF flow dissector program. Prepare for the above by extracting netns_bpf that is part of struct net, for storing all state related to BPF programs attached to netns. Turn flow dissector callbacks for querying/attaching/detaching a program into generic ones that operate on netns_bpf. Next patch will move the generic callbacks into their own module. This is similar to how it is organized for cgroup with cgroup_bpf. Signed-off-by:
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Jakub Sitnicki authored
Split out the part of attach callback that happens with attach/detach lock acquired. This structures the prog attach callback in a way that opens up doors for moving the locking out of flow_dissector and into generic callbacks for attaching/detaching progs to netns in subsequent patches. Signed-off-by:
Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/bpf/20200531082846.2117903-2-jakub@cloudflare.com
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Andrii Nakryiko authored
On systems with recent enough glibc, reallocarray compat won't kick in, so reallocarray() itself has to come from stdlib.h include. But _GNU_SOURCE is necessary to enable it. So add it. Fixes: bf99c936 ("libbpf: Add BPF ring buffer support") Signed-off-by:
Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20200601202601.2139477-1-andriin@fb.com
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Jiri Olsa authored
Currenty lsm uses bpf_tracing_func_proto helpers which do not include stack trace or perf event output. It's useful to have those for bpftrace lsm support [1]. Using tracing_prog_func_proto helpers for lsm programs. [1] https://github.com/iovisor/bpftrace/pull/1347Signed-off-by:
Jiri Olsa <jolsa@kernel.org> Signed-off-by:
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Lorenzo Bianconi authored
In order to use standard 'xdp' prefix, rename convert_to_xdp_frame utility routine in xdp_convert_buff_to_frame and replace all the occurrences Signed-off-by:
Lorenzo Bianconi <lorenzo@kernel.org> Signed-off-by:
Jesper Dangaard Brouer <brouer@redhat.com> Link: https://lore.kernel.org/bpf/6344f739be0d1a08ab2b9607584c4d5478c8c083.1590698295.git.lorenzo@kernel.org
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Lorenzo Bianconi authored
Introduce xdp_convert_frame_to_buff utility routine to initialize xdp_buff fields from xdp_frames ones. Rely on xdp_convert_frame_to_buff in veth xdp code. Suggested-by:
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Alexei Starovoitov authored
Ferenc Fejes says: ==================== This option makes it possible to programatically bind sockets to netdevices. With the help of this option sockets of VRF unaware applications could be distributed between multiple VRFs with an eBPF program. This lets the applications benefit from multiple possible routes. v2: - splitting up the patch to three parts - lock_sk parameter for optional locking in sock_bindtoindex - Stanislav Fomichev - testing the SO_BINDTODEVICE option - Andrii Nakryiko ==================== Signed-off-by: -
Ferenc Fejes authored
This test intended to verify if SO_BINDTODEVICE option works in bpf_setsockopt. Because we already in the SOL_SOCKET level in this connect bpf prog its safe to verify the sanity in the beginning of the connect_v4_prog by calling the bind_to_device test helper. The testing environment already created by the test_sock_addr.sh script so this test assume that two netdevices already existing in the system: veth pair with names test_sock_addr1 and test_sock_addr2. The test will try to bind the socket to those devices first. Then the test assume there are no netdevice with "nonexistent_dev" name so the bpf_setsockopt will give use ENODEV error. At the end the test remove the device binding from the socket by binding it to an empty name. Signed-off-by:
Ferenc Fejes <fejes@inf.elte.hu> Signed-off-by:
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Ferenc Fejes authored
Extending the supported sockopts in bpf_setsockopt with SO_BINDTODEVICE. We call sock_bindtoindex with parameter lock_sk = false in this context because we already owning the socket. Signed-off-by:
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Ferenc Fejes authored
The sock_bindtoindex intended for kernel wide usage however it will lock the socket regardless of the context. This modification relax this behavior optionally: locking the socket will be optional by calling the sock_bindtoindex with lock_sk = true. The modification applied to all users of the sock_bindtoindex. Signed-off-by:
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Denis Efremov authored
buf_prevkey in generic_map_lookup_batch() is allocated with kmalloc(). It's safe to free it with kfree(). Fixes: cb4d03ab ("bpf: Add generic support for lookup batch op") Signed-off-by:
Denis Efremov <efremov@linux.com> Signed-off-by:
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Alexei Starovoitov authored
John Fastabend says: ==================== If a socket is running a BPF_SK_SKB_SREAM_VERDICT program and KTLS is enabled the data stream may be broken if both TLS stream parser and BPF stream parser try to handle data. Fix this here by making KTLS stream parser run first to ensure TLS messages are received correctly and then calling the verdict program. This analogous to how we handle a similar conflict on the TX side. Note, this is a fix but it doesn't make sense to push this late to bpf tree so targeting bpf-next and keeping fixes tags. ==================== Signed-off-by: -
Alexei Starovoitov authored
Sync bpf.h into tool/include/uapi/ Signed-off-by: -
John Fastabend authored
This adds a test for bpf ingress policy. To ensure data writes happen as expected with extra TLS headers we run these tests with data verification enabled by default. This will test receive packets have "PASS" stamped into the front of the payload. Signed-off-by:
John Fastabend <john.fastabend@gmail.com> Signed-off-by:
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Alexei Starovoitov authored
David Ahern says: ==================== Implementation of Daniel's proposal for allowing DEVMAP entries to be a device index, program fd pair. Programs are run after XDP_REDIRECT and have access to both Rx device and Tx device. v4 - moved struct bpf_devmap_val from uapi to devmap.c, named the union and dropped the prefix from the elements - Jesper - fixed 2 bugs in selftests v3 - renamed struct to bpf_devmap_val - used offsetofend to check for expected map size, modification of Toke's comment - check for explicit value sizes - adjusted switch statement in dev_map_run_prog per Andrii's comment - changed SEC shortcut to xdp_devmap - changed selftests to use skeleton and new map declaration v2 - moved dev_map_ext_val definition to uapi to formalize the API for devmap extensions; add bpf_ prefix to the prog_fd and prog_id entries - changed devmap code to handle struct in a way that it can support future extensions - fixed subject in libbpf patch v1 - fixed prog put on invalid program - Toke - changed write value from id to fd per Toke's comments about capabilities - add test cases ==================== Signed-off-by: -
John Fastabend authored
KTLS uses a stream parser to collect TLS messages and send them to the upper layer tls receive handler. This ensures the tls receiver has a full TLS header to parse when it is run. However, when a socket has BPF_SK_SKB_STREAM_VERDICT program attached before KTLS is enabled we end up with two stream parsers running on the same socket. The result is both try to run on the same socket. First the KTLS stream parser runs and calls read_sock() which will tcp_read_sock which in turn calls tcp_rcv_skb(). This dequeues the skb from the sk_receive_queue. When this is done KTLS code then data_ready() callback which because we stacked KTLS on top of the bpf stream verdict program has been replaced with sk_psock_start_strp(). This will in turn kick the stream parser again and eventually do the same thing KTLS did above calling into tcp_rcv_skb() and dequeuing a skb from the sk_receive_queue. At this point the data stream is broke. Part of the stream was handled by the KTLS side some other bytes may have been handled by the BPF side. Generally this results in either missing data or more likely a "Bad Message" complaint from the kTLS receive handler as the BPF program steals some bytes meant to be in a TLS header and/or the TLS header length is no longer correct. We've already broke the idealized model where we can stack ULPs in any order with generic callbacks on the TX side to handle this. So in this patch we do the same thing but for RX side. We add a sk_psock_strp_enabled() helper so TLS can learn a BPF verdict program is running and add a tls_sw_has_ctx_rx() helper so BPF side can learn there is a TLS ULP on the socket. Then on BPF side we omit calling our stream parser to avoid breaking the data stream for the KTLS receiver. Then on the KTLS side we call BPF_SK_SKB_STREAM_VERDICT once the KTLS receiver is done with the packet but before it posts the msg to userspace. This gives us symmetry between the TX and RX halfs and IMO makes it usable again. On the TX side we process packets in this order BPF -> TLS -> TCP and on the receive side in the reverse order TCP -> TLS -> BPF. Discovered while testing OpenSSL 3.0 Alpha2.0 release. Fixes: d829e9c4 ("tls: convert to generic sk_msg interface") Signed-off-by:
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David Ahern authored
Add tests to verify ability to add an XDP program to a entry in a DEVMAP. Add negative tests to show DEVMAP programs can not be attached to devices as a normal XDP program, and accesses to egress_ifindex require BPF_XDP_DEVMAP attach type. Signed-off-by:
David Ahern <dsahern@kernel.org> Signed-off-by:
Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/bpf/20200529220716.75383-6-dsahern@kernel.orgSigned-off-by:
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John Fastabend authored
We will need this block of code called from tls context shortly lets refactor the redirect logic so its easy to use. This also cleans up the switch stmt so we have fewer fallthrough cases. No logic changes are intended. Fixes: d829e9c4 ("tls: convert to generic sk_msg interface") Signed-off-by:
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David Ahern authored
Support SEC("xdp_devmap*") as a short cut for loading the program with type BPF_PROG_TYPE_XDP and expected attach type BPF_XDP_DEVMAP. Signed-off-by: -
David Ahern authored
Add xdp_txq_info as the Tx counterpart to xdp_rxq_info. At the moment only the device is added. Other fields (queue_index) can be added as use cases arise. >From a UAPI perspective, add egress_ifindex to xdp context for bpf programs to see the Tx device. Update the verifier to only allow accesses to egress_ifindex by XDP programs with BPF_XDP_DEVMAP expected attach type. Signed-off-by:
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David Ahern authored
Add BPF_XDP_DEVMAP attach type for use with programs associated with a DEVMAP entry. Allow DEVMAPs to associate a program with a device entry by adding a bpf_prog.fd to 'struct bpf_devmap_val'. Values read show the program id, so the fd and id are a union. bpf programs can get access to the struct via vmlinux.h. The program associated with the fd must have type XDP with expected attach type BPF_XDP_DEVMAP. When a program is associated with a device index, the program is run on an XDP_REDIRECT and before the buffer is added to the per-cpu queue. At this point rxq data is still valid; the next patch adds tx device information allowing the prorgam to see both ingress and egress device indices. XDP generic is skb based and XDP programs do not work with skb's. Block the use case by walking maps used by a program that is to be attached via xdpgeneric and fail if any of them are DEVMAP / DEVMAP_HASH with Block attach of BPF_XDP_DEVMAP programs to devices. Signed-off-by:
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Yonghong Song authored
In bpf_seq_printf() helper, when user specified a "%s" in the format string, strncpy_from_unsafe() is used to read the actual string to a buffer. The string could be a format string or a string in the kernel data structure. It is really unlikely that the string will reside in the user memory. This is different from Commit b2a5212f ("bpf: Restrict bpf_trace_printk()'s %s usage and add %pks, %pus specifier") which still used strncpy_from_unsafe() for "%s" to preserve the old behavior. If in the future, bpf_seq_printf() indeed needs to read user memory, we can implement "%pus" format string. Based on discussion in [1], if the intent is to read kernel memory, strncpy_from_unsafe_strict() should be used. So this patch changed to use strncpy_from_unsafe_strict(). [1]: https://lore.kernel.org/bpf/20200521152301.2587579-1-hch@lst.de/T/ Fixes: 492e639f ("bpf: Add bpf_seq_printf and bpf_seq_write helpers") Signed-off-by:
Yonghong Song <yhs@fb.com> Signed-off-by:
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David Ahern authored
Add 'struct bpf_devmap_val' to formalize the expected values that can be passed in for a DEVMAP. Update devmap code to use the struct. Signed-off-by:
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Amritha Nambiar authored
Add "rx_queue_mapping" to bpf_sock. This gives read access for the existing field (sk_rx_queue_mapping) of struct sock from bpf_sock. Semantics for the bpf_sock rx_queue_mapping access are similar to sk_rx_queue_get(), i.e the value NO_QUEUE_MAPPING is not allowed and -1 is returned in that case. This is useful for transmit queue selection based on the received queue index which is cached in the socket in the receive path. v3: Addressed review comments to add usecase in patch description, and fixed default value for rx_queue_mapping. v2: fixed build error for CONFIG_XPS wrapping, reported by kbuild test robot <lkp@intel.com> Signed-off-by:Amritha Nambiar <amritha.nambiar@intel.com> Signed-off-by:
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Daniel Borkmann authored
Andrii Nakryiko says: ==================== Implement a new BPF ring buffer, as presented at BPF virtual conference ([0]). It presents an alternative to perf buffer, following its semantics closely, but allowing sharing same instance of ring buffer across multiple CPUs efficiently. Most patches have extensive commentary explaining various aspects, so I'll keep cover letter short. Overall structure of the patch set: - patch #1 adds BPF ring buffer implementation to kernel and necessary verifier support; - patch #2 adds libbpf consumer implementation for BPF ringbuf; - patch #3 adds selftest, both for single BPF ring buf use case, as well as using it with array/hash of maps; - patch #4 adds extensive benchmarks and provide some analysis in commit message, it builds upon selftests/bpf's bench runner. - patch #5 adds most of patch #1 commit message as a doc under Documentation/bpf/ringbuf.rst. Litmus tests, validating consumer/producer protocols and memory orderings, were moved out as discussed in [1] and are going to be posted against -rcu tree and put under Documentation/litmus-tests/bpf-rb. [0] https://docs.google.com/presentation/d/18ITdg77Bj6YDOH2LghxrnFxiPWe0fAqcmJY95t_qr0w [1] https://lkml.org/lkml/2020/5/22/1011 v3->v4: - fix ringbuf freeing (vunmap, __free_page); verified with a trivial loop creating and closing ringbuf map endlessly (Daniel); v2->v3: - dropped unnecessary smp_wmb() (Paul); - verifier reference type enhancement patch was dropped (Alexei); - better verifier message for various memory access checks (Alexei); - clarified a bit roundup_len() bit shifting (Alexei); - converted doc to .rst (Alexei); - fixed warning on 32-bit arches regarding tautological ring area size check. v1->v2: - commit()/discard()/output() accept flags (NO_WAKEUP/FORCE_WAKEUP) (Stanislav); - bpf_ringbuf_query() added, returning available data size, ringbuf size, consumer/producer positions, needed to implement smarter notification policy (Stanislav); - added ringbuf UAPI constants to include/uapi/linux/bpf.h (Jonathan); - fixed sample size check, added proper ringbuf size check (Jonathan, Alexei); - wake_up_all() is done through irq_work (Alexei); - consistent use of smp_load_acquire/smp_store_release, no READ_ONCE/WRITE_ONCE (Alexei); - added Documentation/bpf/ringbuf.txt (Stanislav); - updated litmus test with smp_load_acquire/smp_store_release changes; - added ring_buffer__consume() API to libbpf for busy-polling; - ring_buffer__poll() on success returns number of records consumed; - fixed EPOLL notifications, don't assume available data, done similarly to perfbuf's implementation; - both ringbuf and perfbuf now have --rb-sampled mode, instead of pb-raw/pb-custom mode, updated benchmark results; - extended ringbuf selftests to validate epoll logic/manual notification logic, as well as bpf_ringbuf_query(). ==================== Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net>
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Anton Protopopov authored
For write-only stacks and queues bpf_map_update_elem should be allowed, but bpf_map_lookup_elem and bpf_map_lookup_and_delete_elem should fail with EPERM. Signed-off-by:
Anton Protopopov <a.s.protopopov@gmail.com> Signed-off-by:
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Andrii Nakryiko authored
Add commit description from patch #1 as a stand-alone documentation under Documentation/bpf, as it might be more convenient format, in long term perspective. Suggested-by:
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Andrii Nakryiko authored
Extend bench framework with ability to have benchmark-provided child argument parser for custom benchmark-specific parameters. This makes bench generic code modular and independent from any specific benchmark. Also implement a set of benchmarks for new BPF ring buffer and existing perf buffer. 4 benchmarks were implemented: 2 variations for each of BPF ringbuf and perfbuf:, - rb-libbpf utilizes stock libbpf ring_buffer manager for reading data; - rb-custom implements custom ring buffer setup and reading code, to eliminate overheads inherent in generic libbpf code due to callback functions and the need to update consumer position after each consumed record, instead of batching updates (due to pessimistic assumption that user callback might take long time and thus could unnecessarily hold ring buffer space for too long); - pb-libbpf uses stock libbpf perf_buffer code with all the default settings, though uses higher-performance raw event callback to minimize unnecessary overhead; - pb-custom implements its own custom consumer code to minimize any possible overhead of generic libbpf implementation and indirect function calls. All of the test support default, no data notification skipped, mode, as well as sampled mode (with --rb-sampled flag), which allows to trigger epoll notification less frequently and reduce overhead. As will be shown, this mode is especially critical for perf buffer, which suffers from high overhead of wakeups in kernel. Otherwise, all benchamrks implement similar way to generate a batch of records by using fentry/sys_getpgid BPF program, which pushes a bunch of records in a tight loop and records number of successful and dropped samples. Each record is a small 8-byte integer, to minimize the effect of memory copying with bpf_perf_event_output() and bpf_ringbuf_output(). Benchmarks that have only one producer implement optional back-to-back mode, in which record production and consumption is alternating on the same CPU. This is the highest-throughput happy case, showing ultimate performance achievable with either BPF ringbuf or perfbuf. All the below scenarios are implemented in a script in benchs/run_bench_ringbufs.sh. Tests were performed on 28-core/56-thread Intel Xeon CPU E5-2680 v4 @ 2.40GHz CPU. Single-producer, parallel producer ================================== rb-libbpf 12.054 ± 0.320M/s (drops 0.000 ± 0.000M/s) rb-custom 8.158 ± 0.118M/s (drops 0.001 ± 0.003M/s) pb-libbpf 0.931 ± 0.007M/s (drops 0.000 ± 0.000M/s) pb-custom 0.965 ± 0.003M/s (drops 0.000 ± 0.000M/s) Single-producer, parallel producer, sampled notification ======================================================== rb-libbpf 11.563 ± 0.067M/s (drops 0.000 ± 0.000M/s) rb-custom 15.895 ± 0.076M/s (drops 0.000 ± 0.000M/s) pb-libbpf 9.889 ± 0.032M/s (drops 0.000 ± 0.000M/s) pb-custom 9.866 ± 0.028M/s (drops 0.000 ± 0.000M/s) Single producer on one CPU, consumer on another one, both running at full speed. Curiously, rb-libbpf has higher throughput than objectively faster (due to more lightweight consumer code path) rb-custom. It appears that faster consumer causes kernel to send notifications more frequently, because consumer appears to be caught up more frequently. Performance of perfbuf suffers from default "no sampling" policy and huge overhead that causes. In sampled mode, rb-custom is winning very significantly eliminating too frequent in-kernel wakeups, the gain appears to be more than 2x. Perf buffer achieves even more impressive wins, compared to stock perfbuf settings, with 10x improvements in throughput with 1:500 sampling rate. The trade-off is that with sampling, application might not get next X events until X+1st arrives, which is not always acceptable. With steady influx of events, though, this shouldn't be a problem. Overall, single-producer performance of ring buffers seems to be better no matter the sampled/non-sampled modes, but it especially beats ring buffer without sampling due to its adaptive notification approach. Single-producer, back-to-back mode ================================== rb-libbpf 15.507 ± 0.247M/s (drops 0.000 ± 0.000M/s) rb-libbpf-sampled 14.692 ± 0.195M/s (drops 0.000 ± 0.000M/s) rb-custom 21.449 ± 0.157M/s (drops 0.000 ± 0.000M/s) rb-custom-sampled 20.024 ± 0.386M/s (drops 0.000 ± 0.000M/s) pb-libbpf 1.601 ± 0.015M/s (drops 0.000 ± 0.000M/s) pb-libbpf-sampled 8.545 ± 0.064M/s (drops 0.000 ± 0.000M/s) pb-custom 1.607 ± 0.022M/s (drops 0.000 ± 0.000M/s) pb-custom-sampled 8.988 ± 0.144M/s (drops 0.000 ± 0.000M/s) Here we test a back-to-back mode, which is arguably best-case scenario both for BPF ringbuf and perfbuf, because there is no contention and for ringbuf also no excessive notification, because consumer appears to be behind after the first record. For ringbuf, custom consumer code clearly wins with 21.5 vs 16 million records per second exchanged between producer and consumer. Sampled mode actually hurts a bit due to slightly slower producer logic (it needs to fetch amount of data available to decide whether to skip or force notification). Perfbuf with wakeup sampling gets 5.5x throughput increase, compared to no-sampling version. There also doesn't seem to be noticeable overhead from generic libbpf handling code. Perfbuf back-to-back, effect of sample rate =========================================== pb-sampled-1 1.035 ± 0.012M/s (drops 0.000 ± 0.000M/s) pb-sampled-5 3.476 ± 0.087M/s (drops 0.000 ± 0.000M/s) pb-sampled-10 5.094 ± 0.136M/s (drops 0.000 ± 0.000M/s) pb-sampled-25 7.118 ± 0.153M/s (drops 0.000 ± 0.000M/s) pb-sampled-50 8.169 ± 0.156M/s (drops 0.000 ± 0.000M/s) pb-sampled-100 8.887 ± 0.136M/s (drops 0.000 ± 0.000M/s) pb-sampled-250 9.180 ± 0.209M/s (drops 0.000 ± 0.000M/s) pb-sampled-500 9.353 ± 0.281M/s (drops 0.000 ± 0.000M/s) pb-sampled-1000 9.411 ± 0.217M/s (drops 0.000 ± 0.000M/s) pb-sampled-2000 9.464 ± 0.167M/s (drops 0.000 ± 0.000M/s) pb-sampled-3000 9.575 ± 0.273M/s (drops 0.000 ± 0.000M/s) This benchmark shows the effect of event sampling for perfbuf. Back-to-back mode for highest throughput. Just doing every 5th record notification gives 3.5x speed up. 250-500 appears to be the point of diminishing return, with almost 9x speed up. Most benchmarks use 500 as the default sampling for pb-raw and pb-custom. Ringbuf back-to-back, effect of sample rate =========================================== rb-sampled-1 1.106 ± 0.010M/s (drops 0.000 ± 0.000M/s) rb-sampled-5 4.746 ± 0.149M/s (drops 0.000 ± 0.000M/s) rb-sampled-10 7.706 ± 0.164M/s (drops 0.000 ± 0.000M/s) rb-sampled-25 12.893 ± 0.273M/s (drops 0.000 ± 0.000M/s) rb-sampled-50 15.961 ± 0.361M/s (drops 0.000 ± 0.000M/s) rb-sampled-100 18.203 ± 0.445M/s (drops 0.000 ± 0.000M/s) rb-sampled-250 19.962 ± 0.786M/s (drops 0.000 ± 0.000M/s) rb-sampled-500 20.881 ± 0.551M/s (drops 0.000 ± 0.000M/s) rb-sampled-1000 21.317 ± 0.532M/s (drops 0.000 ± 0.000M/s) rb-sampled-2000 21.331 ± 0.535M/s (drops 0.000 ± 0.000M/s) rb-sampled-3000 21.688 ± 0.392M/s (drops 0.000 ± 0.000M/s) Similar benchmark for ring buffer also shows a great advantage (in terms of throughput) of skipping notifications. Skipping every 5th one gives 4x boost. Also similar to perfbuf case, 250-500 seems to be the point of diminishing returns, giving roughly 20x better results. Keep in mind, for this test, notifications are controlled manually with BPF_RB_NO_WAKEUP and BPF_RB_FORCE_WAKEUP. As can be seen from previous benchmarks, adaptive notifications based on consumer's positions provides same (or even slightly better due to simpler load generator on BPF side) benefits in favorable back-to-back scenario. Over zealous and fast consumer, which is almost always caught up, will make thoughput numbers smaller. That's the case when manual notification control might prove to be extremely beneficial. Ringbuf back-to-back, reserve+commit vs output ============================================== reserve 22.819 ± 0.503M/s (drops 0.000 ± 0.000M/s) output 18.906 ± 0.433M/s (drops 0.000 ± 0.000M/s) Ringbuf sampled, reserve+commit vs output ========================================= reserve-sampled 15.350 ± 0.132M/s (drops 0.000 ± 0.000M/s) output-sampled 14.195 ± 0.144M/s (drops 0.000 ± 0.000M/s) BPF ringbuf supports two sets of APIs with various usability and performance tradeoffs: bpf_ringbuf_reserve()+bpf_ringbuf_commit() vs bpf_ringbuf_output(). This benchmark clearly shows superiority of reserve+commit approach, despite using a small 8-byte record size. Single-producer, consumer/producer competing on the same CPU, low batch count ============================================================================= rb-libbpf 3.045 ± 0.020M/s (drops 3.536 ± 0.148M/s) rb-custom 3.055 ± 0.022M/s (drops 3.893 ± 0.066M/s) pb-libbpf 1.393 ± 0.024M/s (drops 0.000 ± 0.000M/s) pb-custom 1.407 ± 0.016M/s (drops 0.000 ± 0.000M/s) This benchmark shows one of the worst-case scenarios, in which producer and consumer do not coordinate *and* fight for the same CPU. No batch count and sampling settings were able to eliminate drops for ringbuffer, producer is just too fast for consumer to keep up. But ringbuf and perfbuf still able to pass through quite a lot of messages, which is more than enough for a lot of applications. Ringbuf, multi-producer contention ================================== rb-libbpf nr_prod 1 10.916 ± 0.399M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 2 4.931 ± 0.030M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 3 4.880 ± 0.006M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 4 3.926 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 8 4.011 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 12 3.967 ± 0.016M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 16 2.604 ± 0.030M/s (drops 0.001 ± 0.002M/s) rb-libbpf nr_prod 20 2.233 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 24 2.085 ± 0.015M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 28 2.055 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 32 1.962 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 36 2.089 ± 0.005M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 40 2.118 ± 0.006M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 44 2.105 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 48 2.120 ± 0.058M/s (drops 0.000 ± 0.001M/s) rb-libbpf nr_prod 52 2.074 ± 0.024M/s (drops 0.007 ± 0.014M/s) Ringbuf uses a very short-duration spinlock during reservation phase, to check few invariants, increment producer count and set record header. This is the biggest point of contention for ringbuf implementation. This benchmark evaluates the effect of multiple competing writers on overall throughput of a single shared ringbuffer. Overall throughput drops almost 2x when going from single to two highly-contended producers, gradually dropping with additional competing producers. Performance drop stabilizes at around 20 producers and hovers around 2mln even with 50+ fighting producers, which is a 5x drop compared to non-contended case. Good kernel implementation in kernel helps maintain decent performance here. Note, that in the intended real-world scenarios, it's not expected to get even close to such a high levels of contention. But if contention will become a problem, there is always an option of sharding few ring buffers across a set of CPUs. Signed-off-by: -
Andrii Nakryiko authored
Both singleton BPF ringbuf and BPF ringbuf with map-in-map use cases are tested. Also reserve+submit/discards and output variants of API are validated. Signed-off-by:
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