Currently, suppose a userspace application has loaded a bpf program
and attached it to a tracepoint/kprobe/uprobe, and a bpf
introspection tool, e.g., bpftool, wants to show which bpf program
is attached to which tracepoint/kprobe/uprobe. Such attachment
information will be really useful to understand the overall bpf
deployment in the system.
There is a name field (16 bytes) for each program, which could
be used to encode the attachment point. There are some drawbacks
for this approaches. First, bpftool user (e.g., an admin) may not
really understand the association between the name and the
attachment point. Second, if one program is attached to multiple
places, encoding a proper name which can imply all these
attachments becomes difficult.
This patch introduces a new bpf subcommand BPF_TASK_FD_QUERY.
Given a pid and fd, if the <pid, fd> is associated with a
tracepoint/kprobe/uprobe perf event, BPF_TASK_FD_QUERY will return
. prog_id
. tracepoint name, or
. k[ret]probe funcname + offset or kernel addr, or
. u[ret]probe filename + offset
to the userspace.
The user can use "bpftool prog" to find more information about
bpf program itself with prog_id.
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch adds the End.BPF action to the LWT seg6local infrastructure.
This action works like any other seg6local End action, meaning that an IPv6
header with SRH is needed, whose DA has to be equal to the SID of the
action. It will also advance the SRH to the next segment, the BPF program
does not have to take care of this.
Since the BPF program may not be a source of instability in the kernel, it
is important to ensure that the integrity of the packet is maintained
before yielding it back to the IPv6 layer. The hook hence keeps track if
the SRH has been altered through the helpers, and re-validates its
content if needed with seg6_validate_srh. The state kept for validation is
stored in a per-CPU buffer. The BPF program is not allowed to directly
write into the packet, and only some fields of the SRH can be altered
through the helper bpf_lwt_seg6_store_bytes.
Performances profiling has shown that the SRH re-validation does not induce
a significant overhead. If the altered SRH is deemed as invalid, the packet
is dropped.
This validation is also done before executing any action through
bpf_lwt_seg6_action, and will not be performed again if the SRH is not
modified after calling the action.
The BPF program may return 3 types of return codes:
- BPF_OK: the End.BPF action will look up the next destination through
seg6_lookup_nexthop.
- BPF_REDIRECT: if an action has been executed through the
bpf_lwt_seg6_action helper, the BPF program should return this
value, as the skb's destination is already set and the default
lookup should not be performed.
- BPF_DROP : the packet will be dropped.
Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Acked-by: David Lebrun <dlebrun@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
The BPF seg6local hook should be powerful enough to enable users to
implement most of the use-cases one could think of. After some thinking,
we figured out that the following actions should be possible on a SRv6
packet, requiring 3 specific helpers :
- bpf_lwt_seg6_store_bytes: Modify non-sensitive fields of the SRH
- bpf_lwt_seg6_adjust_srh: Allow to grow or shrink a SRH
(to add/delete TLVs)
- bpf_lwt_seg6_action: Apply some SRv6 network programming actions
(specifically End.X, End.T, End.B6 and
End.B6.Encap)
The specifications of these helpers are provided in the patch (see
include/uapi/linux/bpf.h).
The non-sensitive fields of the SRH are the following : flags, tag and
TLVs. The other fields can not be modified, to maintain the SRH
integrity. Flags, tag and TLVs can easily be modified as their validity
can be checked afterwards via seg6_validate_srh. It is not allowed to
modify the segments directly. If one wants to add segments on the path,
he should stack a new SRH using the End.B6 action via
bpf_lwt_seg6_action.
Growing, shrinking or editing TLVs via the helpers will flag the SRH as
invalid, and it will have to be re-validated before re-entering the IPv6
layer. This flag is stored in a per-CPU buffer, along with the current
header length in bytes.
Storing the SRH len in bytes in the control block is mandatory when using
bpf_lwt_seg6_adjust_srh. The Header Ext. Length field contains the SRH
len rounded to 8 bytes (a padding TLV can be inserted to ensure the 8-bytes
boundary). When adding/deleting TLVs within the BPF program, the SRH may
temporary be in an invalid state where its length cannot be rounded to 8
bytes without remainder, hence the need to store the length in bytes
separately. The caller of the BPF program can then ensure that the SRH's
final length is valid using this value. Again, a final SRH modified by a
BPF program which doesn’t respect the 8-bytes boundary will be discarded
as it will be considered as invalid.
Finally, a fourth helper is provided, bpf_lwt_push_encap, which is
available from the LWT BPF IN hook, but not from the seg6local BPF one.
This helper allows to encapsulate a Segment Routing Header (either with
a new outer IPv6 header, or by inlining it directly in the existing IPv6
header) into a non-SRv6 packet. This helper is required if we want to
offer the possibility to dynamically encapsulate a SRH for non-SRv6 packet,
as the BPF seg6local hook only works on traffic already containing a SRH.
This is the BPF equivalent of the seg6 LWT infrastructure, which achieves
the same purpose but with a static SRH per route.
These helpers require CONFIG_IPV6=y (and not =m).
Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Acked-by: David Lebrun <dlebrun@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This adds new two new fields to struct bpf_prog_info. For
multi-function programs, these fields can be used to pass
a list of the JITed image lengths of each function for a
given program to userspace using the bpf system call with
the BPF_OBJ_GET_INFO_BY_FD command.
This can be used by userspace applications like bpftool
to split up the contiguous JITed dump, also obtained via
the system call, into more relatable chunks corresponding
to each function.
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This adds new two new fields to struct bpf_prog_info. For
multi-function programs, these fields can be used to pass
a list of kernel symbol addresses for all functions in a
given program to userspace using the bpf system call with
the BPF_OBJ_GET_INFO_BY_FD command.
When bpf_jit_kallsyms is enabled, we can get the address
of the corresponding kernel symbol for a callee function
and resolve the symbol's name. The address is determined
by adding the value of the call instruction's imm field
to __bpf_call_base. This offset gets assigned to the imm
field by the verifier.
For some architectures, such as powerpc64, the imm field
is not large enough to hold this offset.
We resolve this by:
[1] Assigning the subprog id to the imm field of a call
instruction in the verifier instead of the offset of
the callee's symbol's address from __bpf_call_base.
[2] Determining the address of a callee's corresponding
symbol by using the imm field as an index for the
list of kernel symbol addresses now available from
the program info.
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
In "struct bpf_map_info", the name "btf_id", "btf_key_id" and "btf_value_id"
could cause confusion because the "id" of "btf_id" means the BPF obj id
given to the BTF object while
"btf_key_id" and "btf_value_id" means the BTF type id within
that BTF object.
To make it clear, btf_key_id and btf_value_id are
renamed to btf_key_type_id and btf_value_type_id.
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Currently sk_msg programs only have access to the raw data. However,
it is often useful when building policies to have the policies specific
to the socket endpoint. This allows using the socket tuple as input
into filters, etc.
This patch adds ctx access to the sock fields.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Sockmap is currently backed by an array and enforces keys to be
four bytes. This works well for many use cases and was originally
modeled after devmap which also uses four bytes keys. However,
this has become limiting in larger use cases where a hash would
be more appropriate. For example users may want to use the 5-tuple
of the socket as the lookup key.
To support this add hash support.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Provide a helper for doing a FIB and neighbor lookup in the kernel
tables from an XDP program. The helper provides a fastpath for forwarding
packets. If the packet is a local delivery or for any reason is not a
simple lookup and forward, the packet continues up the stack.
If it is to be forwarded, the forwarding can be done directly if the
neighbor is already known. If the neighbor does not exist, the first
few packets go up the stack for neighbor resolution. Once resolved, the
xdp program provides the fast path.
On successful lookup the nexthop dmac, current device smac and egress
device index are returned.
The API supports IPv4, IPv6 and MPLS protocols, but only IPv4 and IPv6
are implemented in this patch. The API includes layer 4 parameters if
the XDP program chooses to do deep packet inspection to allow compare
against ACLs implemented as FIB rules.
Header rewrite is left to the XDP program.
The lookup takes 2 flags:
- BPF_FIB_LOOKUP_DIRECT to do a lookup that bypasses FIB rules and goes
straight to the table associated with the device (expert setting for
those looking to maximize throughput)
- BPF_FIB_LOOKUP_OUTPUT to do a lookup from the egress perspective.
Default is an ingress lookup.
Initial performance numbers collected by Jesper, forwarded packets/sec:
Full stack XDP FIB lookup XDP Direct lookup
IPv4 1,947,969 7,074,156 7,415,333
IPv6 1,728,000 6,165,504 7,262,720
These number are single CPU core forwarding on a Broadwell
E5-1650 v4 @ 3.60GHz.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
During BPF_OBJ_GET_INFO_BY_FD on a btf_fd, the current bpf_attr's
info.info is directly filled with the BTF binary data. It is
not extensible. In this case, we want to add BTF ID.
This patch adds "struct bpf_btf_info" which has the BTF ID as
one of its member. The BTF binary data itself is exposed through
the "btf" and "btf_size" members.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This patch gives an ID to each loaded BTF. The ID is allocated by
the idr like the existing prog-id and map-id.
The bpf_put(map->btf) is moved to __bpf_map_put() so that the
userspace can stop seeing the BTF ID ASAP when the last BTF
refcnt is gone.
It also makes BTF accessible from userspace through the
1. new BPF_BTF_GET_FD_BY_ID command. It is limited to CAP_SYS_ADMIN
which is inline with the BPF_BTF_LOAD cmd and the existing
BPF_[MAP|PROG]_GET_FD_BY_ID cmd.
2. new btf_id (and btf_key_id + btf_value_id) in "struct bpf_map_info"
Once the BTF ID handler is accessible from userspace, freeing a BTF
object has to go through a rcu period. The BPF_BTF_GET_FD_BY_ID cmd
can then be done under a rcu_read_lock() instead of taking
spin_lock.
[Note: A similar rcu usage can be done to the existing
bpf_prog_get_fd_by_id() in a follow up patch]
When processing the BPF_BTF_GET_FD_BY_ID cmd,
refcount_inc_not_zero() is needed because the BTF object
could be already in the rcu dead row . btf_get() is
removed since its usage is currently limited to btf.c
alone. refcount_inc() is used directly instead.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This adds a small BPF helper similar to bpf_skb_load_bytes() that
is able to load relative to mac/net header offset from the skb's
linear data. Compared to bpf_skb_load_bytes(), it takes a fifth
argument namely start_header, which is either BPF_HDR_START_MAC
or BPF_HDR_START_NET. This allows for a more flexible alternative
compared to LD_ABS/LD_IND with negative offset. It's enabled for
tc BPF programs as well as sock filter program types where it's
mainly useful in reuseport programs to ease access to lower header
data.
Reference: https://lists.iovisor.org/pipermail/iovisor-dev/2017-March/000698.html
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The xskmap is yet another BPF map, very much inspired by
dev/cpu/sockmap, and is a holder of AF_XDP sockets. A user application
adds AF_XDP sockets into the map, and by using the bpf_redirect_map
helper, an XDP program can redirect XDP frames to an AF_XDP socket.
Note that a socket that is bound to certain ifindex/queue index will
*only* accept XDP frames from that netdev/queue index. If an XDP
program tries to redirect from a netdev/queue index other than what
the socket is bound to, the frame will not be received on the socket.
A socket can reside in multiple maps.
v3: Fixed race and simplified code.
v2: Removed one indirection in map lookup.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Fix formatting (indent) for bpf_get_stack() helper documentation, so
that the doc is rendered correctly with the Python script.
Fixes: c195651e56 ("bpf: add bpf_get_stack helper")
Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Some edits brought to the last iteration of BPF helper functions
documentation introduced an error with RST formatting. As a result, most
of one paragraph is rendered in bold text when only the name of a helper
should be. Fix it, and fix formatting of another function name in the
same paragraph.
Fixes: c6b5fb8690 ("bpf: add documentation for eBPF helpers (42-50)")
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Helpers may operate on two types of ctx structures: user visible ones
(e.g. `struct bpf_sock_ops`) when used in user programs, and kernel ones
(e.g. `struct bpf_sock_ops_kern`) in kernel implementation.
UAPI documentation must refer to only user visible structures.
The patch replaces references to `_kern` structures in BPF helpers
description by corresponding user visible structures.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Currently, stackmap and bpf_get_stackid helper are provided
for bpf program to get the stack trace. This approach has
a limitation though. If two stack traces have the same hash,
only one will get stored in the stackmap table,
so some stack traces are missing from user perspective.
This patch implements a new helper, bpf_get_stack, will
send stack traces directly to bpf program. The bpf program
is able to see all stack traces, and then can do in-kernel
processing or send stack traces to user space through
shared map or bpf_perf_event_output.
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions:
Helper from Nikita:
- bpf_xdp_adjust_tail()
Helper from Eyal:
- bpf_skb_get_xfrm_state()
v4:
- New patch (helpers did not exist yet for previous versions).
Cc: Nikita V. Shirokov <tehnerd@tehnerd.com>
Cc: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by John:
- bpf_redirect_map()
- bpf_sk_redirect_map()
- bpf_sock_map_update()
- bpf_msg_redirect_map()
- bpf_msg_apply_bytes()
- bpf_msg_cork_bytes()
- bpf_msg_pull_data()
v4:
- bpf_redirect_map(): Fix typos: "XDP_ABORT" changed to "XDP_ABORTED",
"his" to "this". Also add a paragraph on performance improvement over
bpf_redirect() helper.
v3:
- bpf_sk_redirect_map(): Improve description of BPF_F_INGRESS flag.
- bpf_msg_redirect_map(): Improve description of BPF_F_INGRESS flag.
- bpf_redirect_map(): Fix note on CPU redirection, not fully implemented
for generic XDP but supported on native XDP.
- bpf_msg_pull_data(): Clarify comment about invalidated verifier
checks.
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions:
Helpers from Lawrence:
- bpf_setsockopt()
- bpf_getsockopt()
- bpf_sock_ops_cb_flags_set()
Helpers from Yonghong:
- bpf_perf_event_read_value()
- bpf_perf_prog_read_value()
Helper from Josef:
- bpf_override_return()
Helper from Andrey:
- bpf_bind()
v4:
- bpf_perf_event_read_value(): State that this helper should be
preferred over bpf_perf_event_read().
v3:
- bpf_perf_event_read_value(): Fix time of selection for perf event type
in description. Remove occurences of "cores" to avoid confusion with
"CPU".
- bpf_bind(): Remove last paragraph of description, which was off topic.
Cc: Lawrence Brakmo <brakmo@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Yonghong Song <yhs@fb.com>
[for bpf_perf_event_read_value(), bpf_perf_prog_read_value()]
Acked-by: Andrey Ignatov <rdna@fb.com>
[for bpf_bind()]
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions:
Helper from Kaixu:
- bpf_perf_event_read()
Helpers from Martin:
- bpf_skb_under_cgroup()
- bpf_xdp_adjust_head()
Helpers from Sargun:
- bpf_probe_write_user()
- bpf_current_task_under_cgroup()
Helper from Thomas:
- bpf_skb_change_head()
Helper from Gianluca:
- bpf_probe_read_str()
Helpers from Chenbo:
- bpf_get_socket_cookie()
- bpf_get_socket_uid()
v4:
- bpf_perf_event_read(): State that bpf_perf_event_read_value() should
be preferred over this helper.
- bpf_skb_change_head(): Clarify comment about invalidated verifier
checks.
- bpf_xdp_adjust_head(): Clarify comment about invalidated verifier
checks.
- bpf_probe_write_user(): Add that dst must be a valid user space
address.
- bpf_get_socket_cookie(): Improve description by making clearer that
the cockie belongs to the socket, and state that it remains stable for
the life of the socket.
v3:
- bpf_perf_event_read(): Fix time of selection for perf event type in
description. Remove occurences of "cores" to avoid confusion with
"CPU".
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Gianluca Borello <g.borello@gmail.com>
Cc: Chenbo Feng <fengc@google.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
[for bpf_skb_under_cgroup(), bpf_xdp_adjust_head()]
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by Daniel:
- bpf_get_hash_recalc()
- bpf_skb_change_tail()
- bpf_skb_pull_data()
- bpf_csum_update()
- bpf_set_hash_invalid()
- bpf_get_numa_node_id()
- bpf_set_hash()
- bpf_skb_adjust_room()
- bpf_xdp_adjust_meta()
v4:
- bpf_skb_change_tail(): Clarify comment about invalidated verifier
checks.
- bpf_skb_pull_data(): Clarify the motivation for using this helper or
bpf_skb_load_bytes(), on non-linear buffers. Fix RST formatting for
*skb*. Clarify comment about invalidated verifier checks.
- bpf_csum_update(): Fix description of checksum (entire packet, not IP
checksum). Fix a typo: "header" instead of "helper".
- bpf_set_hash_invalid(): Mention bpf_get_hash_recalc().
- bpf_get_numa_node_id(): State that the helper is not restricted to
programs attached to sockets.
- bpf_skb_adjust_room(): Clarify comment about invalidated verifier
checks.
- bpf_xdp_adjust_meta(): Clarify comment about invalidated verifier
checks.
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by Daniel:
- bpf_get_prandom_u32()
- bpf_get_smp_processor_id()
- bpf_get_cgroup_classid()
- bpf_get_route_realm()
- bpf_skb_load_bytes()
- bpf_csum_diff()
- bpf_skb_get_tunnel_opt()
- bpf_skb_set_tunnel_opt()
- bpf_skb_change_proto()
- bpf_skb_change_type()
v4:
- bpf_get_prandom_u32(): Warn that the prng is not cryptographically
secure.
- bpf_get_smp_processor_id(): Fix a typo (case).
- bpf_get_cgroup_classid(): Clarify description. Add notes on the helper
being limited to cgroup v1, and to egress path.
- bpf_get_route_realm(): Add comparison with bpf_get_cgroup_classid().
Add a note about usage with TC and advantage of clsact. Fix a typo in
return value ("sdb" instead of "skb").
- bpf_skb_load_bytes(): Make explicit loading large data loads it to the
eBPF stack.
- bpf_csum_diff(): Add a note on seed that can be cascaded. Link to
bpf_l3|l4_csum_replace().
- bpf_skb_get_tunnel_opt(): Add a note about usage with "collect
metadata" mode, and example of this with Geneve.
- bpf_skb_set_tunnel_opt(): Add a link to bpf_skb_get_tunnel_opt()
description.
- bpf_skb_change_proto(): Mention that the main use case is NAT64.
Clarify comment about invalidated verifier checks.
v3:
- bpf_get_prandom_u32(): Fix helper name :(. Add description, including
a note on the internal random state.
- bpf_get_smp_processor_id(): Add description, including a note on the
processor id remaining stable during program run.
- bpf_get_cgroup_classid(): State that CONFIG_CGROUP_NET_CLASSID is
required to use the helper. Add a reference to related documentation.
State that placing a task in net_cls controller disables cgroup-bpf.
- bpf_get_route_realm(): State that CONFIG_CGROUP_NET_CLASSID is
required to use this helper.
- bpf_skb_load_bytes(): Fix comment on current use cases for the helper.
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by Alexei:
- bpf_get_current_pid_tgid()
- bpf_get_current_uid_gid()
- bpf_get_current_comm()
- bpf_skb_vlan_push()
- bpf_skb_vlan_pop()
- bpf_skb_get_tunnel_key()
- bpf_skb_set_tunnel_key()
- bpf_redirect()
- bpf_perf_event_output()
- bpf_get_stackid()
- bpf_get_current_task()
v4:
- bpf_redirect(): Fix typo: "XDP_ABORT" changed to "XDP_ABORTED". Add
note on bpf_redirect_map() providing better performance. Replace "Save
for" with "Except for".
- bpf_skb_vlan_push(): Clarify comment about invalidated verifier
checks.
- bpf_skb_vlan_pop(): Clarify comment about invalidated verifier
checks.
- bpf_skb_get_tunnel_key(): Add notes on tunnel_id, "collect metadata"
mode, and example tunneling protocols with which it can be used.
- bpf_skb_set_tunnel_key(): Add a reference to the description of
bpf_skb_get_tunnel_key().
- bpf_perf_event_output(): Specify that, and for what purpose, the
helper can be used with programs attached to TC and XDP.
v3:
- bpf_skb_get_tunnel_key(): Change and improve description and example.
- bpf_redirect(): Improve description of BPF_F_INGRESS flag.
- bpf_perf_event_output(): Fix first sentence of description. Delete
wrong statement on context being evaluated as a struct pt_reg. Remove
the long yet incomplete example.
- bpf_get_stackid(): Add a note about PERF_MAX_STACK_DEPTH being
configurable.
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by Alexei:
- bpf_map_lookup_elem()
- bpf_map_update_elem()
- bpf_map_delete_elem()
- bpf_probe_read()
- bpf_ktime_get_ns()
- bpf_trace_printk()
- bpf_skb_store_bytes()
- bpf_l3_csum_replace()
- bpf_l4_csum_replace()
- bpf_tail_call()
- bpf_clone_redirect()
v4:
- bpf_map_lookup_elem(): Add "const" qualifier for key.
- bpf_map_update_elem(): Add "const" qualifier for key and value.
- bpf_map_lookup_elem(): Add "const" qualifier for key.
- bpf_skb_store_bytes(): Clarify comment about invalidated verifier
checks.
- bpf_l3_csum_replace(): Mention L3 instead of just IP, and add a note
about bpf_csum_diff().
- bpf_l4_csum_replace(): Mention L4 instead of just TCP/UDP, and add a
note about bpf_csum_diff().
- bpf_tail_call(): Bring minor edits to description.
- bpf_clone_redirect(): Add a note about the relation with
bpf_redirect(). Also clarify comment about invalidated verifier
checks.
v3:
- bpf_map_lookup_elem(): Fix description of restrictions for flags
related to the existence of the entry.
- bpf_trace_printk(): State that trace_pipe can be configured. Fix
return value in case an unknown format specifier is met. Add a note on
kernel log notice when the helper is used. Edit example.
- bpf_tail_call(): Improve comment on stack inheritance.
- bpf_clone_redirect(): Improve description of BPF_F_INGRESS flag.
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Remove previous "overview" of eBPF helpers from user bpf.h header.
Replace it by a comment explaining how to process the new documentation
(to come in following patches) with a Python script to produce RST, then
man page documentation.
Also add the aforementioned Python script under scripts/. It is used to
process include/uapi/linux/bpf.h and to extract helper descriptions, to
turn it into a RST document that can further be processed with rst2man
to produce a man page. The script takes one "--filename <path/to/file>"
option. If the script is launched from scripts/ in the kernel root
directory, it should be able to find the location of the header to
parse, and "--filename <path/to/file>" is then optional. If it cannot
find the file, then the option becomes mandatory. RST-formatted
documentation is printed to standard output.
Typical workflow for producing the final man page would be:
$ ./scripts/bpf_helpers_doc.py \
--filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
$ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
$ man /tmp/bpf-helpers.7
Note that the tool kernel-doc cannot be used to document eBPF helpers,
whose signatures are not available directly in the header files
(pre-processor directives are used to produce them at the beginning of
the compilation process).
v4:
- Also remove overviews for newly added bpf_xdp_adjust_tail() and
bpf_skb_get_xfrm_state().
- Remove vague statement about what helpers are restricted to GPL
programs in "LICENSE" section for man page footer.
- Replace license boilerplate with SPDX tag for Python script.
v3:
- Change license for man page.
- Remove "for safety reasons" from man page header text.
- Change "packets metadata" to "packets" in man page header text.
- Move and fix comment on helpers introducing no overhead.
- Remove "NOTES" section from man page footer.
- Add "LICENSE" section to man page footer.
- Edit description of file include/uapi/linux/bpf.h in man page footer.
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Adding gpl_compatible flag to struct bpf_prog_info
so it can be dumped via bpf_prog_get_info_by_fd and
displayed via bpftool progs dump.
Alexei noticed 4-byte hole in struct bpf_prog_info,
so we put the u32 flags field in there, and we can
keep adding bit fields in there without breaking
user space.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit introduces a helper which allows fetching xfrm state
parameters by eBPF programs attached to TC.
Prototype:
bpf_skb_get_xfrm_state(skb, index, xfrm_state, size, flags)
skb: pointer to skb
index: the index in the skb xfrm_state secpath array
xfrm_state: pointer to 'struct bpf_xfrm_state'
size: size of 'struct bpf_xfrm_state'
flags: reserved for future extensions
The helper returns 0 on success. Non zero if no xfrm state at the index
is found - or non exists at all.
struct bpf_xfrm_state currently includes the SPI, peer IPv4/IPv6
address and the reqid; it can be further extended by adding elements to
its end - indicating the populated fields by the 'size' argument -
keeping backwards compatibility.
Typical usage:
struct bpf_xfrm_state x = {};
bpf_skb_get_xfrm_state(skb, 0, &x, sizeof(x), 0);
...
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This patch adds pretty print support to the basic arraymap.
Support for other bpf maps can be added later.
This patch adds new attrs to the BPF_MAP_CREATE command to allow
specifying the btf_fd, btf_key_id and btf_value_id. The
BPF_MAP_CREATE can then associate the btf to the map if
the creating map supports BTF.
A BTF supported map needs to implement two new map ops,
map_seq_show_elem() and map_check_btf(). This patch has
implemented these new map ops for the basic arraymap.
It also adds file_operations, bpffs_map_fops, to the pinned
map such that the pinned map can be opened and read.
After that, the user has an intuitive way to do
"cat bpffs/pathto/a-pinned-map" instead of getting
an error.
bpffs_map_fops should not be extended further to support
other operations. Other operations (e.g. write/key-lookup...)
should be realized by the userspace tools (e.g. bpftool) through
the BPF_OBJ_GET_INFO_BY_FD, map's lookup/update interface...etc.
Follow up patches will allow the userspace to obtain
the BTF from a map-fd.
Here is a sample output when reading a pinned arraymap
with the following map's value:
struct map_value {
int count_a;
int count_b;
};
cat /sys/fs/bpf/pinned_array_map:
0: {1,2}
1: {3,4}
2: {5,6}
...
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This patch adds a BPF_BTF_LOAD command which
1) loads and verifies the BTF (implemented in earlier patches)
2) returns a BTF fd to userspace. In the next patch, the
BTF fd can be specified during BPF_MAP_CREATE.
It currently limits to CAP_SYS_ADMIN.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Adding new bpf helper which would allow us to manipulate
xdp's data_end pointer, and allow us to reduce packet's size
indended use case: to generate ICMP messages from XDP context,
where such message would contain truncated original packet.
Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
"Post-hooks" are hooks that are called right before returning from
sys_bind. At this time IP and port are already allocated and no further
changes to `struct sock` can happen before returning from sys_bind but
BPF program has a chance to inspect the socket and change sys_bind
result.
Specifically it can e.g. inspect what port was allocated and if it
doesn't satisfy some policy, BPF program can force sys_bind to fail and
return EPERM to user.
Another example of usage is recording the IP:port pair to some map to
use it in later calls to sys_connect. E.g. if some TCP server inside
cgroup was bound to some IP:port_n, it can be recorded to a map. And
later when some TCP client inside same cgroup is trying to connect to
127.0.0.1:port_n, BPF hook for sys_connect can override the destination
and connect application to IP:port_n instead of 127.0.0.1:port_n. That
helps forcing all applications inside a cgroup to use desired IP and not
break those applications if they e.g. use localhost to communicate
between each other.
== Implementation details ==
Post-hooks are implemented as two new attach types
`BPF_CGROUP_INET4_POST_BIND` and `BPF_CGROUP_INET6_POST_BIND` for
existing prog type `BPF_PROG_TYPE_CGROUP_SOCK`.
Separate attach types for IPv4 and IPv6 are introduced to avoid access
to IPv6 field in `struct sock` from `inet_bind()` and to IPv4 field from
`inet6_bind()` since those fields might not make sense in such cases.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
== The problem ==
See description of the problem in the initial patch of this patch set.
== The solution ==
The patch provides much more reliable in-kernel solution for the 2nd
part of the problem: making outgoing connecttion from desired IP.
It adds new attach types `BPF_CGROUP_INET4_CONNECT` and
`BPF_CGROUP_INET6_CONNECT` for program type
`BPF_PROG_TYPE_CGROUP_SOCK_ADDR` that can be used to override both
source and destination of a connection at connect(2) time.
Local end of connection can be bound to desired IP using newly
introduced BPF-helper `bpf_bind()`. It allows to bind to only IP though,
and doesn't support binding to port, i.e. leverages
`IP_BIND_ADDRESS_NO_PORT` socket option. There are two reasons for this:
* looking for a free port is expensive and can affect performance
significantly;
* there is no use-case for port.
As for remote end (`struct sockaddr *` passed by user), both parts of it
can be overridden, remote IP and remote port. It's useful if an
application inside cgroup wants to connect to another application inside
same cgroup or to itself, but knows nothing about IP assigned to the
cgroup.
Support is added for IPv4 and IPv6, for TCP and UDP.
IPv4 and IPv6 have separate attach types for same reason as sys_bind
hooks, i.e. to prevent reading from / writing to e.g. user_ip6 fields
when user passes sockaddr_in since it'd be out-of-bound.
== Implementation notes ==
The patch introduces new field in `struct proto`: `pre_connect` that is
a pointer to a function with same signature as `connect` but is called
before it. The reason is in some cases BPF hooks should be called way
before control is passed to `sk->sk_prot->connect`. Specifically
`inet_dgram_connect` autobinds socket before calling
`sk->sk_prot->connect` and there is no way to call `bpf_bind()` from
hooks from e.g. `ip4_datagram_connect` or `ip6_datagram_connect` since
it'd cause double-bind. On the other hand `proto.pre_connect` provides a
flexible way to add BPF hooks for connect only for necessary `proto` and
call them at desired time before `connect`. Since `bpf_bind()` is
allowed to bind only to IP and autobind in `inet_dgram_connect` binds
only port there is no chance of double-bind.
bpf_bind() sets `force_bind_address_no_port` to bind to only IP despite
of value of `bind_address_no_port` socket field.
bpf_bind() sets `with_lock` to `false` when calling to __inet_bind()
and __inet6_bind() since all call-sites, where bpf_bind() is called,
already hold socket lock.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
== The problem ==
There is a use-case when all processes inside a cgroup should use one
single IP address on a host that has multiple IP configured. Those
processes should use the IP for both ingress and egress, for TCP and UDP
traffic. So TCP/UDP servers should be bound to that IP to accept
incoming connections on it, and TCP/UDP clients should make outgoing
connections from that IP. It should not require changing application
code since it's often not possible.
Currently it's solved by intercepting glibc wrappers around syscalls
such as `bind(2)` and `connect(2)`. It's done by a shared library that
is preloaded for every process in a cgroup so that whenever TCP/UDP
server calls `bind(2)`, the library replaces IP in sockaddr before
passing arguments to syscall. When application calls `connect(2)` the
library transparently binds the local end of connection to that IP
(`bind(2)` with `IP_BIND_ADDRESS_NO_PORT` to avoid performance penalty).
Shared library approach is fragile though, e.g.:
* some applications clear env vars (incl. `LD_PRELOAD`);
* `/etc/ld.so.preload` doesn't help since some applications are linked
with option `-z nodefaultlib`;
* other applications don't use glibc and there is nothing to intercept.
== The solution ==
The patch provides much more reliable in-kernel solution for the 1st
part of the problem: binding TCP/UDP servers on desired IP. It does not
depend on application environment and implementation details (whether
glibc is used or not).
It adds new eBPF program type `BPF_PROG_TYPE_CGROUP_SOCK_ADDR` and
attach types `BPF_CGROUP_INET4_BIND` and `BPF_CGROUP_INET6_BIND`
(similar to already existing `BPF_CGROUP_INET_SOCK_CREATE`).
The new program type is intended to be used with sockets (`struct sock`)
in a cgroup and provided by user `struct sockaddr`. Pointers to both of
them are parts of the context passed to programs of newly added types.
The new attach types provides hooks in `bind(2)` system call for both
IPv4 and IPv6 so that one can write a program to override IP addresses
and ports user program tries to bind to and apply such a program for
whole cgroup.
== Implementation notes ==
[1]
Separate attach types for `AF_INET` and `AF_INET6` are added
intentionally to prevent reading/writing to offsets that don't make
sense for corresponding socket family. E.g. if user passes `sockaddr_in`
it doesn't make sense to read from / write to `user_ip6[]` context
fields.
[2]
The write access to `struct bpf_sock_addr_kern` is implemented using
special field as an additional "register".
There are just two registers in `sock_addr_convert_ctx_access`: `src`
with value to write and `dst` with pointer to context that can't be
changed not to break later instructions. But the fields, allowed to
write to, are not available directly and to access them address of
corresponding pointer has to be loaded first. To get additional register
the 1st not used by `src` and `dst` one is taken, its content is saved
to `bpf_sock_addr_kern.tmp_reg`, then the register is used to load
address of pointer field, and finally the register's content is restored
from the temporary field after writing `src` value.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
== The problem ==
There are use-cases when a program of some type can be attached to
multiple attach points and those attach points must have different
permissions to access context or to call helpers.
E.g. context structure may have fields for both IPv4 and IPv6 but it
doesn't make sense to read from / write to IPv6 field when attach point
is somewhere in IPv4 stack.
Same applies to BPF-helpers: it may make sense to call some helper from
some attach point, but not from other for same prog type.
== The solution ==
Introduce `expected_attach_type` field in in `struct bpf_attr` for
`BPF_PROG_LOAD` command. If scenario described in "The problem" section
is the case for some prog type, the field will be checked twice:
1) At load time prog type is checked to see if attach type for it must
be known to validate program permissions correctly. Prog will be
rejected with EINVAL if it's the case and `expected_attach_type` is
not specified or has invalid value.
2) At attach time `attach_type` is compared with `expected_attach_type`,
if prog type requires to have one, and, if they differ, attach will
be rejected with EINVAL.
The `expected_attach_type` is now available as part of `struct bpf_prog`
in both `bpf_verifier_ops->is_valid_access()` and
`bpf_verifier_ops->get_func_proto()` () and can be used to check context
accesses and calls to helpers correspondingly.
Initially the idea was discussed by Alexei Starovoitov <ast@fb.com> and
Daniel Borkmann <daniel@iogearbox.net> here:
https://marc.info/?l=linux-netdev&m=152107378717201&w=2
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Introduce BPF_PROG_TYPE_RAW_TRACEPOINT bpf program type to access
kernel internal arguments of the tracepoints in their raw form.
>From bpf program point of view the access to the arguments look like:
struct bpf_raw_tracepoint_args {
__u64 args[0];
};
int bpf_prog(struct bpf_raw_tracepoint_args *ctx)
{
// program can read args[N] where N depends on tracepoint
// and statically verified at program load+attach time
}
kprobe+bpf infrastructure allows programs access function arguments.
This feature allows programs access raw tracepoint arguments.
Similar to proposed 'dynamic ftrace events' there are no abi guarantees
to what the tracepoints arguments are and what their meaning is.
The program needs to type cast args properly and use bpf_probe_read()
helper to access struct fields when argument is a pointer.
For every tracepoint __bpf_trace_##call function is prepared.
In assembler it looks like:
(gdb) disassemble __bpf_trace_xdp_exception
Dump of assembler code for function __bpf_trace_xdp_exception:
0xffffffff81132080 <+0>: mov %ecx,%ecx
0xffffffff81132082 <+2>: jmpq 0xffffffff811231f0 <bpf_trace_run3>
where
TRACE_EVENT(xdp_exception,
TP_PROTO(const struct net_device *dev,
const struct bpf_prog *xdp, u32 act),
The above assembler snippet is casting 32-bit 'act' field into 'u64'
to pass into bpf_trace_run3(), while 'dev' and 'xdp' args are passed as-is.
All of ~500 of __bpf_trace_*() functions are only 5-10 byte long
and in total this approach adds 7k bytes to .text.
This approach gives the lowest possible overhead
while calling trace_xdp_exception() from kernel C code and
transitioning into bpf land.
Since tracepoint+bpf are used at speeds of 1M+ events per second
this is valuable optimization.
The new BPF_RAW_TRACEPOINT_OPEN sys_bpf command is introduced
that returns anon_inode FD of 'bpf-raw-tracepoint' object.
The user space looks like:
// load bpf prog with BPF_PROG_TYPE_RAW_TRACEPOINT type
prog_fd = bpf_prog_load(...);
// receive anon_inode fd for given bpf_raw_tracepoint with prog attached
raw_tp_fd = bpf_raw_tracepoint_open("xdp_exception", prog_fd);
Ctrl-C of tracing daemon or cmdline tool that uses this feature
will automatically detach bpf program, unload it and
unregister tracepoint probe.
On the kernel side the __bpf_raw_tp_map section of pointers to
tracepoint definition and to __bpf_trace_*() probe function is used
to find a tracepoint with "xdp_exception" name and
corresponding __bpf_trace_xdp_exception() probe function
which are passed to tracepoint_probe_register() to connect probe
with tracepoint.
Addition of bpf_raw_tracepoint doesn't interfere with ftrace and perf
tracepoint mechanisms. perf_event_open() can be used in parallel
on the same tracepoint.
Multiple bpf_raw_tracepoint_open("xdp_exception", prog_fd) are permitted.
Each with its own bpf program. The kernel will execute
all tracepoint probes and all attached bpf programs.
In the future bpf_raw_tracepoints can be extended with
query/introspection logic.
__bpf_raw_tp_map section logic was contributed by Steven Rostedt
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Currently, if a bpf sk msg program is run the program
can only parse data that the (start,end) pointers already
consumed. For sendmsg hooks this is likely the first
scatterlist element. For sendpage this will be the range
(0,0) because the data is shared with userspace and by
default we want to avoid allowing userspace to modify
data while (or after) BPF verdict is being decided.
To support pulling in additional bytes for parsing use
a new helper bpf_sk_msg_pull(start, end, flags) which
works similar to cls tc logic. This helper will attempt
to point the data start pointer at 'start' bytes offest
into msg and data end pointer at 'end' bytes offset into
message.
After basic sanity checks to ensure 'start' <= 'end' and
'end' <= msg_length there are a few cases we need to
handle.
First the sendmsg hook has already copied the data from
userspace and has exclusive access to it. Therefor, it
is not necessesary to copy the data. However, it may
be required. After finding the scatterlist element with
'start' offset byte in it there are two cases. One the
range (start,end) is entirely contained in the sg element
and is already linear. All that is needed is to update the
data pointers, no allocate/copy is needed. The other case
is (start, end) crosses sg element boundaries. In this
case we allocate a block of size 'end - start' and copy
the data to linearize it.
Next sendpage hook has not copied any data in initial
state so that data pointers are (0,0). In this case we
handle it similar to the above sendmsg case except the
allocation/copy must always happen. Then when sending
the data we have possibly three memory regions that
need to be sent, (0, start - 1), (start, end), and
(end + 1, msg_length). This is required to ensure any
writes by the BPF program are correctly transmitted.
Lastly this operation will invalidate any previous
data checks so BPF programs will have to revalidate
pointers after making this BPF call.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
In the case where we need a specific number of bytes before a
verdict can be assigned, even if the data spans multiple sendmsg
or sendfile calls. The BPF program may use msg_cork_bytes().
The extreme case is a user can call sendmsg repeatedly with
1-byte msg segments. Obviously, this is bad for performance but
is still valid. If the BPF program needs N bytes to validate
a header it can use msg_cork_bytes to specify N bytes and the
BPF program will not be called again until N bytes have been
accumulated. The infrastructure will attempt to coalesce data
if possible so in many cases (most my use cases at least) the
data will be in a single scatterlist element with data pointers
pointing to start/end of the element. However, this is dependent
on available memory so is not guaranteed. So BPF programs must
validate data pointer ranges, but this is the case anyways to
convince the verifier the accesses are valid.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
A single sendmsg or sendfile system call can contain multiple logical
messages that a BPF program may want to read and apply a verdict. But,
without an apply_bytes helper any verdict on the data applies to all
bytes in the sendmsg/sendfile. Alternatively, a BPF program may only
care to read the first N bytes of a msg. If the payload is large say
MB or even GB setting up and calling the BPF program repeatedly for
all bytes, even though the verdict is already known, creates
unnecessary overhead.
To allow BPF programs to control how many bytes a given verdict
applies to we implement a bpf_msg_apply_bytes() helper. When called
from within a BPF program this sets a counter, internal to the
BPF infrastructure, that applies the last verdict to the next N
bytes. If the N is smaller than the current data being processed
from a sendmsg/sendfile call, the first N bytes will be sent and
the BPF program will be re-run with start_data pointing to the N+1
byte. If N is larger than the current data being processed the
BPF verdict will be applied to multiple sendmsg/sendfile calls
until N bytes are consumed.
Note1 if a socket closes with apply_bytes counter non-zero this
is not a problem because data is not being buffered for N bytes
and is sent as its received.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This implements a BPF ULP layer to allow policy enforcement and
monitoring at the socket layer. In order to support this a new
program type BPF_PROG_TYPE_SK_MSG is used to run the policy at
the sendmsg/sendpage hook. To attach the policy to sockets a
sockmap is used with a new program attach type BPF_SK_MSG_VERDICT.
Similar to previous sockmap usages when a sock is added to a
sockmap, via a map update, if the map contains a BPF_SK_MSG_VERDICT
program type attached then the BPF ULP layer is created on the
socket and the attached BPF_PROG_TYPE_SK_MSG program is run for
every msg in sendmsg case and page/offset in sendpage case.
BPF_PROG_TYPE_SK_MSG Semantics/API:
BPF_PROG_TYPE_SK_MSG supports only two return codes SK_PASS and
SK_DROP. Returning SK_DROP free's the copied data in the sendmsg
case and in the sendpage case leaves the data untouched. Both cases
return -EACESS to the user. Returning SK_PASS will allow the msg to
be sent.
In the sendmsg case data is copied into kernel space buffers before
running the BPF program. The kernel space buffers are stored in a
scatterlist object where each element is a kernel memory buffer.
Some effort is made to coalesce data from the sendmsg call here.
For example a sendmsg call with many one byte iov entries will
likely be pushed into a single entry. The BPF program is run with
data pointers (start/end) pointing to the first sg element.
In the sendpage case data is not copied. We opt not to copy the
data by default here, because the BPF infrastructure does not
know what bytes will be needed nor when they will be needed. So
copying all bytes may be wasteful. Because of this the initial
start/end data pointers are (0,0). Meaning no data can be read or
written. This avoids reading data that may be modified by the
user. A new helper is added later in this series if reading and
writing the data is needed. The helper call will do a copy by
default so that the page is exclusively owned by the BPF call.
The verdict from the BPF_PROG_TYPE_SK_MSG applies to the entire msg
in the sendmsg() case and the entire page/offset in the sendpage case.
This avoids ambiguity on how to handle mixed return codes in the
sendmsg case. Again a helper is added later in the series if
a verdict needs to apply to multiple system calls and/or only
a subpart of the currently being processed message.
The helper msg_redirect_map() can be used to select the socket to
send the data on. This is used similar to existing redirect use
cases. This allows policy to redirect msgs.
Pseudo code simple example:
The basic logic to attach a program to a socket is as follows,
// load the programs
bpf_prog_load(SOCKMAP_TCP_MSG_PROG, BPF_PROG_TYPE_SK_MSG,
&obj, &msg_prog);
// lookup the sockmap
bpf_map_msg = bpf_object__find_map_by_name(obj, "my_sock_map");
// get fd for sockmap
map_fd_msg = bpf_map__fd(bpf_map_msg);
// attach program to sockmap
bpf_prog_attach(msg_prog, map_fd_msg, BPF_SK_MSG_VERDICT, 0);
Adding sockets to the map is done in the normal way,
// Add a socket 'fd' to sockmap at location 'i'
bpf_map_update_elem(map_fd_msg, &i, fd, BPF_ANY);
After the above any socket attached to "my_sock_map", in this case
'fd', will run the BPF msg verdict program (msg_prog) on every
sendmsg and sendpage system call.
For a complete example see BPF selftests or sockmap samples.
Implementation notes:
It seemed the simplest, to me at least, to use a refcnt to ensure
psock is not lost across the sendmsg copy into the sg, the bpf program
running on the data in sg_data, and the final pass to the TCP stack.
Some performance testing may show a better method to do this and avoid
the refcnt cost, but for now use the simpler method.
Another item that will come after basic support is in place is
supporting MSG_MORE flag. At the moment we call sendpages even if
the MSG_MORE flag is set. An enhancement would be to collect the
pages into a larger scatterlist and pass down the stack. Notice that
bpf_tcp_sendmsg() could support this with some additional state saved
across sendmsg calls. I built the code to support this without having
to do refactoring work. Other features TBD include ZEROCOPY and the
TCP_RECV_QUEUE/TCP_NO_QUEUE support. This will follow initial series
shortly.
Future work could improve size limits on the scatterlist rings used
here. Currently, we use MAX_SKB_FRAGS simply because this was being
used already in the TLS case. Future work could extend the kernel sk
APIs to tune this depending on workload. This is a trade-off
between memory usage and throughput performance.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Currently, bpf stackmap store address for each entry in the call trace.
To map these addresses to user space files, it is necessary to maintain
the mapping from these virtual address to symbols in the binary. Usually,
the user space profiler (such as perf) has to scan /proc/pid/maps at the
beginning of profiling, and monitor mmap2() calls afterwards. Given the
cost of maintaining the address map, this solution is not practical for
system wide profiling that is always on.
This patch tries to solve this problem with a variation of stackmap. This
variation is enabled by flag BPF_F_STACK_BUILD_ID. Instead of storing
addresses, the variation stores ELF file build_id + offset.
Build ID is a 20-byte unique identifier for ELF files. The following
command shows the Build ID of /bin/bash:
[user@]$ readelf -n /bin/bash
...
Build ID: XXXXXXXXXX
...
With BPF_F_STACK_BUILD_ID, bpf_get_stackid() tries to parse Build ID
for each entry in the call trace, and translate it into the following
struct:
struct bpf_stack_build_id_offset {
__s32 status;
unsigned char build_id[BPF_BUILD_ID_SIZE];
union {
__u64 offset;
__u64 ip;
};
};
The search of build_id is limited to the first page of the file, and this
page should be in page cache. Otherwise, we fallback to store ip for this
entry (ip field in struct bpf_stack_build_id_offset). This requires the
build_id to be stored in the first page. A quick survey of binary and
dynamic library files in a few different systems shows that almost all
binary and dynamic library files have build_id in the first page.
Build_id is only meaningful for user stack. If a kernel stack is added to
a stackmap with BPF_F_STACK_BUILD_ID, it will automatically fallback to
only store ip (status == BPF_STACK_BUILD_ID_IP). Similarly, if build_id
lookup failed for some reason, it will also fallback to store ip.
User space can access struct bpf_stack_build_id_offset with bpf
syscall BPF_MAP_LOOKUP_ELEM. It is necessary for user space to
maintain mapping from build id to binary files. This mostly static
mapping is much easier to maintain than per process address maps.
Note: Stackmap with build_id only works in non-nmi context at this time.
This is because we need to take mm->mmap_sem for find_vma(). If this
changes, we would like to allow build_id lookup in nmi context.
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Currently GRE sequence number can only be used in native
tunnel mode. This patch adds sequence number support for
gre collect metadata mode. RFC2890 defines GRE sequence
number to be specific to the traffic flow identified by the
key. However, this patch does not implement per-key seqno.
The sequence number is shared in the same tunnel device.
That is, different tunnel keys using the same collect_md
tunnel share single sequence number.
Signed-off-by: William Tu <u9012063@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Adds support for calling sock_ops BPF program when there is a TCP state
change. Two arguments are used; one for the old state and another for
the new state.
There is a new enum in include/uapi/linux/bpf.h that exports the TCP
states that prepends BPF_ to the current TCP state names. If it is ever
necessary to change the internal TCP state values (other than adding
more to the end), then it will become necessary to convert from the
internal TCP state value to the BPF value before calling the BPF
sock_ops function. There are a set of compile checks added in tcp.c
to detect if the internal and BPF values differ so we can make the
necessary fixes.
New op: BPF_SOCK_OPS_STATE_CB.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adds support for calling sock_ops BPF program when there is a
retransmission. Three arguments are used; one for the sequence number,
another for the number of segments retransmitted, and the last one for
the return value of tcp_transmit_skb (0 => success).
Does not include syn-ack retransmissions.
New op: BPF_SOCK_OPS_RETRANS_CB.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adds an optional call to sock_ops BPF program based on whether the
BPF_SOCK_OPS_RTO_CB_FLAG is set in bpf_sock_ops_flags.
The BPF program is passed 2 arguments: icsk_retransmits and whether the
RTO has expired.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adds field bpf_sock_ops_cb_flags to tcp_sock and bpf_sock_ops. Its primary
use is to determine if there should be calls to sock_ops bpf program at
various points in the TCP code. The field is initialized to zero,
disabling the calls. A sock_ops BPF program can set it, per connection and
as necessary, when the connection is established.
It also adds support for reading and writting the field within a
sock_ops BPF program. Reading is done by accessing the field directly.
However, writing is done through the helper function
bpf_sock_ops_cb_flags_set, in order to return an error if a BPF program
is trying to set a callback that is not supported in the current kernel
(i.e. running an older kernel). The helper function returns 0 if it was
able to set all of the bits set in the argument, a positive number
containing the bits that could not be set, or -EINVAL if the socket is
not a full TCP socket.
Examples of where one could call the bpf program:
1) When RTO fires
2) When a packet is retransmitted
3) When the connection terminates
4) When a packet is sent
5) When a packet is received
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adds support for passing up to 4 arguments to sock_ops bpf functions. It
reusues the reply union, so the bpf_sock_ops structures are not
increased in size.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tell user space about device on which the map was created.
Unfortunate reality of user ABI makes sharing this code
with program offload difficult but the information is the
same.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Doc BPF ld/ldx size defines as comments in code, as it makes in
faster to lookup in a programming/review setting, than looking up
the sizes in Documentation/networking/filter.txt.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Yonghong Song