void *bpf_map_lookup_elem(struct bpf_map *map, const void *key)
Description
Perform a lookup in map for an entry associated to
key.
Return Map value associated to key, or NULL if no entry
was found.
long bpf_map_update_elem(struct bpf_map *map, const void *key,
const void *value, u64 flags)
Description
Add or update the value of the entry associated to
key in map with value. flags is one of:
BPF_NOEXIST
The entry for key must not exist in the map.
BPF_EXIST
The entry for key must already exist in the
map.
BPF_ANY
No condition on the existence of the entry
for key.
Flag value BPF_NOEXIST cannot be used for maps of
types BPF_MAP_TYPE_ARRAY or
BPF_MAP_TYPE_PERCPU_ARRAY (all elements always
exist), the helper would return an error.
Return 0 on success, or a negative error in case of
failure.
long bpf_map_delete_elem(struct bpf_map *map, const void *key)
Description
Delete entry with key from map.
Return 0 on success, or a negative error in case of
failure.
long bpf_probe_read(void *dst, u32 size, const void *unsafe_ptr)
Description
For tracing programs, safely attempt to read size
bytes from kernel space address unsafe_ptr and
store the data in dst.
Generally, use bpf_probe_read_user() or
bpf_probe_read_kernel() instead.
Return 0 on success, or a negative error in case of
failure.
u64 bpf_ktime_get_ns(void)
Description
Return the time elapsed since system boot, in
nanoseconds. Does not include time the system was
suspended. See: clock_gettime(CLOCK_MONOTONIC)
Return Current ktime.
long bpf_trace_printk(const char *fmt, u32 fmt_size, ...)
Description
This helper is a "printk()-like" facility for
debugging. It prints a message defined by format
fmt (of size fmt_size) to file
/sys/kernel/debug/tracing/trace from DebugFS, if
available. It can take up to three additional u64
arguments (as an eBPF helpers, the total number of
arguments is limited to five).
Each time the helper is called, it appends a line
to the trace. Lines are discarded while
/sys/kernel/debug/tracing/trace is open, use
/sys/kernel/debug/tracing/trace_pipe to avoid this.
The format of the trace is customizable, and the
exact output one will get depends on the options
set in /sys/kernel/debug/tracing/trace_options (see
also the README file under the same directory).
However, it usually defaults to something like:
telnet-470 [001] .N.. 419421.045894: 0x00000001: <formatted msg>
In the above:
• telnet is the name of the current task.
• 470 is the PID of the current task.
• 001 is the CPU number on which the task is
running.
• In .N.., each character refers to a set of
options (whether irqs are enabled, scheduling
options, whether hard/softirqs are running,
level of preempt_disabled respectively). N
means that TIF_NEED_RESCHED and
PREEMPT_NEED_RESCHED are set.
• 419421.045894 is a timestamp.
• 0x00000001 is a fake value used by BPF for the
instruction pointer register.
• <formatted msg> is the message formatted with
fmt.
The conversion specifiers supported by fmt are
similar, but more limited than for printk(). They
are %d, %i, %u, %x, %ld, %li, %lu, %lx, %lld, %lli,
%llu, %llx, %p, %s. No modifier (size of field,
padding with zeroes, etc.) is available, and the
helper will return -EINVAL (but print nothing) if
it encounters an unknown specifier.
Also, note that bpf_trace_printk() is slow, and
should only be used for debugging purposes. For
this reason, a notice block (spanning several
lines) is printed to kernel logs and states that
the helper should not be used "for production use"
the first time this helper is used (or more
precisely, when trace_printk() buffers are
allocated). For passing values to user space, perf
events should be preferred.
Return The number of bytes written to the buffer, or a
negative error in case of failure.
u32 bpf_get_prandom_u32(void)
Description
Get a pseudo-random number.
From a security point of view, this helper uses its
own pseudo-random internal state, and cannot be
used to infer the seed of other random functions in
the kernel. However, it is essential to note that
the generator used by the helper is not
cryptographically secure.
Return A random 32-bit unsigned value.
u32 bpf_get_smp_processor_id(void)
Description
Get the SMP (symmetric multiprocessing) processor
id. Note that all programs run with preemption
disabled, which means that the SMP processor id is
stable during all the execution of the program.
Return The SMP id of the processor running the program.
long bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const
void *from, u32 len, u64 flags)
Description
Store len bytes from address from into the packet
associated to skb, at offset. flags are a
combination of BPF_F_RECOMPUTE_CSUM (automatically
recompute the checksum for the packet after storing
the bytes) and BPF_F_INVALIDATE_HASH (set
skb->hash, skb->swhash and skb->l4hash to 0).
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_l3_csum_replace(struct sk_buff *skb, u32 offset, u64
from, u64 to, u64 size)
Description
Recompute the layer 3 (e.g. IP) checksum for the
packet associated to skb. Computation is
incremental, so the helper must know the former
value of the header field that was modified (from),
the new value of this field (to), and the number of
bytes (2 or 4) for this field, stored in size.
Alternatively, it is possible to store the
difference between the previous and the new values
of the header field in to, by setting from and size
to 0. For both methods, offset indicates the
location of the IP checksum within the packet.
This helper works in combination with
bpf_csum_diff(), which does not update the checksum
in-place, but offers more flexibility and can
handle sizes larger than 2 or 4 for the checksum to
update.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_l4_csum_replace(struct sk_buff *skb, u32 offset, u64
from, u64 to, u64 flags)
Description
Recompute the layer 4 (e.g. TCP, UDP, or ICMP)
checksum for the packet associated to skb.
Computation is incremental, so the helper must know
the former value of the header field that was
modified (from), the new value of this field (to),
and the number of bytes (2 or 4) for this field,
stored on the lowest four bits of flags.
Alternatively, it is possible to store the
difference between the previous and the new values
of the header field in to, by setting from and the
four lowest bits of flags to 0. For both methods,
offset indicates the location of the IP checksum
within the packet. In addition to the size of the
field, flags can be added (bitwise OR) actual
flags. With BPF_F_MARK_MANGLED_0, a null checksum
is left untouched (unless BPF_F_MARK_ENFORCE is
added as well), and for updates resulting in a null
checksum the value is set to CSUM_MANGLED_0
instead. Flag BPF_F_PSEUDO_HDR indicates the
checksum is to be computed against a pseudo-header.
This helper works in combination with
bpf_csum_diff(), which does not update the checksum
in-place, but offers more flexibility and can
handle sizes larger than 2 or 4 for the checksum to
update.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_tail_call(void *ctx, struct bpf_map *prog_array_map, u32
index)
Description
This special helper is used to trigger a "tail
call", or in other words, to jump into another eBPF
program. The same stack frame is used (but values
on stack and in registers for the caller are not
accessible to the callee). This mechanism allows
for program chaining, either for raising the
maximum number of available eBPF instructions, or
to execute given programs in conditional blocks.
For security reasons, there is an upper limit to
the number of successive tail calls that can be
performed.
Upon call of this helper, the program attempts to
jump into a program referenced at index index in
prog_array_map, a special map of type
BPF_MAP_TYPE_PROG_ARRAY, and passes ctx, a pointer
to the context.
If the call succeeds, the kernel immediately runs
the first instruction of the new program. This is
not a function call, and it never returns to the
previous program. If the call fails, then the
helper has no effect, and the caller continues to
run its subsequent instructions. A call can fail if
the destination program for the jump does not exist
(i.e. index is superior to the number of entries in
prog_array_map), or if the maximum number of tail
calls has been reached for this chain of programs.
This limit is defined in the kernel by the macro
MAX_TAIL_CALL_CNT (not accessible to user space),
which is currently set to 32.
Return 0 on success, or a negative error in case of
failure.
long bpf_clone_redirect(struct sk_buff *skb, u32 ifindex, u64
flags)
Description
Clone and redirect the packet associated to skb to
another net device of index ifindex. Both ingress
and egress interfaces can be used for redirection.
The BPF_F_INGRESS value in flags is used to make
the distinction (ingress path is selected if the
flag is present, egress path otherwise). This is
the only flag supported for now.
In comparison with bpf_redirect() helper,
bpf_clone_redirect() has the associated cost of
duplicating the packet buffer, but this can be
executed out of the eBPF program. Conversely,
bpf_redirect() is more efficient, but it is handled
through an action code where the redirection
happens only after the eBPF program has returned.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
u64 bpf_get_current_pid_tgid(void)
Return A 64-bit integer containing the current tgid and
pid, and created as such: current_task->tgid << 32
| current_task->pid.
u64 bpf_get_current_uid_gid(void)
Return A 64-bit integer containing the current GID and
UID, and created as such: current_gid << 32 |
current_uid.
long bpf_get_current_comm(void *buf, u32 size_of_buf)
Description
Copy the comm attribute of the current task into
buf of size_of_buf. The comm attribute contains the
name of the executable (excluding the path) for the
current task. The size_of_buf must be strictly
positive. On success, the helper makes sure that
the buf is NUL-terminated. On failure, it is filled
with zeroes.
Return 0 on success, or a negative error in case of
failure.
u32 bpf_get_cgroup_classid(struct sk_buff *skb)
Description
Retrieve the classid for the current task, i.e. for
the net_cls cgroup to which skb belongs.
This helper can be used on TC egress path, but not
on ingress.
The net_cls cgroup provides an interface to tag
network packets based on a user-provided identifier
for all traffic coming from the tasks belonging to
the related cgroup. See also the related kernel
documentation, available from the Linux sources in
file
Documentation/admin-guide/cgroup-v1/net_cls.rst.
The Linux kernel has two versions for cgroups:
there are cgroups v1 and cgroups v2. Both are
available to users, who can use a mixture of them,
but note that the net_cls cgroup is for cgroup v1
only. This makes it incompatible with BPF programs
run on cgroups, which is a cgroup-v2-only feature
(a socket can only hold data for one version of
cgroups at a time).
This helper is only available is the kernel was
compiled with the CONFIG_CGROUP_NET_CLASSID
configuration option set to "y" or to "m".
Return The classid, or 0 for the default unconfigured
classid.
long bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto,
u16 vlan_tci)
Description
Push a vlan_tci (VLAN tag control information) of
protocol vlan_proto to the packet associated to
skb, then update the checksum. Note that if
vlan_proto is different from ETH_P_8021Q and
ETH_P_8021AD, it is considered to be ETH_P_8021Q.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_vlan_pop(struct sk_buff *skb)
Description
Pop a VLAN header from the packet associated to
skb.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_get_tunnel_key(struct sk_buff *skb, struct
bpf_tunnel_key *key, u32 size, u64 flags)
Description
Get tunnel metadata. This helper takes a pointer
key to an empty struct bpf_tunnel_key of size, that
will be filled with tunnel metadata for the packet
associated to skb. The flags can be set to
BPF_F_TUNINFO_IPV6, which indicates that the tunnel
is based on IPv6 protocol instead of IPv4.
The struct bpf_tunnel_key is an object that
generalizes the principal parameters used by
various tunneling protocols into a single struct.
This way, it can be used to easily make a decision
based on the contents of the encapsulation header,
"summarized" in this struct. In particular, it
holds the IP address of the remote end (IPv4 or
IPv6, depending on the case) in key->remote_ipv4 or
key->remote_ipv6. Also, this struct exposes the
key->tunnel_id, which is generally mapped to a VNI
(Virtual Network Identifier), making it
programmable together with the
bpf_skb_set_tunnel_key() helper.
Let's imagine that the following code is part of a
program attached to the TC ingress interface, on
one end of a GRE tunnel, and is supposed to filter
out all messages coming from remote ends with IPv4
address other than 10.0.0.1:
int ret;
struct bpf_tunnel_key key = {};
ret = bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
if (ret < 0)
return TC_ACT_SHOT; // drop packet
if (key.remote_ipv4 != 0x0a000001)
return TC_ACT_SHOT; // drop packet
return TC_ACT_OK; // accept packet
This interface can also be used with all
encapsulation devices that can operate in "collect
metadata" mode: instead of having one network
device per specific configuration, the "collect
metadata" mode only requires a single device where
the configuration can be extracted from this
helper.
This can be used together with various tunnels such
as VXLan, Geneve, GRE, or IP in IP (IPIP).
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_set_tunnel_key(struct sk_buff *skb, struct
bpf_tunnel_key *key, u32 size, u64 flags)
Description
Populate tunnel metadata for packet associated to
skb. The tunnel metadata is set to the contents of
key, of size. The flags can be set to a combination
of the following values:
BPF_F_TUNINFO_IPV6
Indicate that the tunnel is based on IPv6
protocol instead of IPv4.
BPF_F_ZERO_CSUM_TX
For IPv4 packets, add a flag to tunnel
metadata indicating that checksum
computation should be skipped and checksum
set to zeroes.
BPF_F_DONT_FRAGMENT
Add a flag to tunnel metadata indicating
that the packet should not be fragmented.
BPF_F_SEQ_NUMBER
Add a flag to tunnel metadata indicating
that a sequence number should be added to
tunnel header before sending the packet.
This flag was added for GRE encapsulation,
but might be used with other protocols as
well in the future.
Here is a typical usage on the transmit path:
struct bpf_tunnel_key key;
populate key ...
bpf_skb_set_tunnel_key(skb, &key, sizeof(key), 0);
bpf_clone_redirect(skb, vxlan_dev_ifindex, 0);
See also the description of the
bpf_skb_get_tunnel_key() helper for additional
information.
Return 0 on success, or a negative error in case of
failure.
u64 bpf_perf_event_read(struct bpf_map *map, u64 flags)
Description
Read the value of a perf event counter. This helper
relies on a map of type
BPF_MAP_TYPE_PERF_EVENT_ARRAY. The nature of the
perf event counter is selected when map is updated
with perf event file descriptors. The map is an
array whose size is the number of available CPUs,
and each cell contains a value relative to one CPU.
The value to retrieve is indicated by flags, that
contains the index of the CPU to look up, masked
with BPF_F_INDEX_MASK. Alternatively, flags can be
set to BPF_F_CURRENT_CPU to indicate that the value
for the current CPU should be retrieved.
Note that before Linux 4.13, only hardware perf
event can be retrieved.
Also, be aware that the newer helper
bpf_perf_event_read_value() is recommended over
bpf_perf_event_read() in general. The latter has
some ABI quirks where error and counter value are
used as a return code (which is wrong to do since
ranges may overlap). This issue is fixed with
bpf_perf_event_read_value(), which at the same time
provides more features over the
bpf_perf_event_read() interface. Please refer to
the description of bpf_perf_event_read_value() for
details.
Return The value of the perf event counter read from the
map, or a negative error code in case of failure.
long bpf_redirect(u32 ifindex, u64 flags)
Description
Redirect the packet to another net device of index
ifindex. This helper is somewhat similar to
bpf_clone_redirect(), except that the packet is not
cloned, which provides increased performance.
Except for XDP, both ingress and egress interfaces
can be used for redirection. The BPF_F_INGRESS
value in flags is used to make the distinction
(ingress path is selected if the flag is present,
egress path otherwise). Currently, XDP only
supports redirection to the egress interface, and
accepts no flag at all.
The same effect can also be attained with the more
generic bpf_redirect_map(), which uses a BPF map to
store the redirect target instead of providing it
directly to the helper.
Return For XDP, the helper returns XDP_REDIRECT on success
or XDP_ABORTED on error. For other program types,
the values are TC_ACT_REDIRECT on success or
TC_ACT_SHOT on error.
u32 bpf_get_route_realm(struct sk_buff *skb)
Description
Retrieve the realm or the route, that is to say the
tclassid field of the destination for the skb. The
identifier retrieved is a user-provided tag,
similar to the one used with the net_cls cgroup
(see description for bpf_get_cgroup_classid()
helper), but here this tag is held by a route (a
destination entry), not by a task.
Retrieving this identifier works with the clsact TC
egress hook (see also tc-bpf(8)), or alternatively
on conventional classful egress qdiscs, but not on
TC ingress path. In case of clsact TC egress hook,
this has the advantage that, internally, the
destination entry has not been dropped yet in the
transmit path. Therefore, the destination entry
does not need to be artificially held via
netif_keep_dst() for a classful qdisc until the skb
is freed.
This helper is available only if the kernel was
compiled with CONFIG_IP_ROUTE_CLASSID configuration
option.
Return The realm of the route for the packet associated to
skb, or 0 if none was found.
long bpf_perf_event_output(void *ctx, struct bpf_map *map, u64
flags, void *data, u64 size)
Description
Write raw data blob into a special BPF perf event
held by map of type BPF_MAP_TYPE_PERF_EVENT_ARRAY.
This perf event must have the following attributes:
PERF_SAMPLE_RAW as sample_type, PERF_TYPE_SOFTWARE
as type, and PERF_COUNT_SW_BPF_OUTPUT as config.
The flags are used to indicate the index in map for
which the value must be put, masked with
BPF_F_INDEX_MASK. Alternatively, flags can be set
to BPF_F_CURRENT_CPU to indicate that the index of
the current CPU core should be used.
The value to write, of size, is passed through eBPF
stack and pointed by data.
The context of the program ctx needs also be passed
to the helper.
On user space, a program willing to read the values
needs to call perf_event_open() on the perf event
(either for one or for all CPUs) and to store the
file descriptor into the map. This must be done
before the eBPF program can send data into it. An
example is available in file
samples/bpf/trace_output_user.c in the Linux kernel
source tree (the eBPF program counterpart is in
samples/bpf/trace_output_kern.c).
bpf_perf_event_output() achieves better performance
than bpf_trace_printk() for sharing data with user
space, and is much better suitable for streaming
data from eBPF programs.
Note that this helper is not restricted to tracing
use cases and can be used with programs attached to
TC or XDP as well, where it allows for passing data
to user space listeners. Data can be:
• Only custom structs,
• Only the packet payload, or
• A combination of both.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_load_bytes(const void *skb, u32 offset, void *to,
u32 len)
Description
This helper was provided as an easy way to load
data from a packet. It can be used to load len
bytes from offset from the packet associated to
skb, into the buffer pointed by to.
Since Linux 4.7, usage of this helper has mostly
been replaced by "direct packet access", enabling
packet data to be manipulated with skb->data and
skb->data_end pointing respectively to the first
byte of packet data and to the byte after the last
byte of packet data. However, it remains useful if
one wishes to read large quantities of data at once
from a packet into the eBPF stack.
Return 0 on success, or a negative error in case of
failure.
long bpf_get_stackid(void *ctx, struct bpf_map *map, u64 flags)
Description
Walk a user or a kernel stack and return its id. To
achieve this, the helper needs ctx, which is a
pointer to the context on which the tracing program
is executed, and a pointer to a map of type
BPF_MAP_TYPE_STACK_TRACE.
The last argument, flags, holds the number of stack
frames to skip (from 0 to 255), masked with
BPF_F_SKIP_FIELD_MASK. The next bits can be used to
set a combination of the following flags:
BPF_F_USER_STACK
Collect a user space stack instead of a
kernel stack.
BPF_F_FAST_STACK_CMP
Compare stacks by hash only.
BPF_F_REUSE_STACKID
If two different stacks hash into the same
stackid, discard the old one.
The stack id retrieved is a 32 bit long integer
handle which can be further combined with other
data (including other stack ids) and used as a key
into maps. This can be useful for generating a
variety of graphs (such as flame graphs or off-cpu
graphs).
For walking a stack, this helper is an improvement
over bpf_probe_read(), which can be used with
unrolled loops but is not efficient and consumes a
lot of eBPF instructions. Instead,
bpf_get_stackid() can collect up to
PERF_MAX_STACK_DEPTH both kernel and user frames.
Note that this limit can be controlled with the
sysctl program, and that it should be manually
increased in order to profile long user stacks
(such as stacks for Java programs). To do so, use:
# sysctl kernel.perf_event_max_stack=<new value>
Return The positive or null stack id on success, or a
negative error in case of failure.
s64 bpf_csum_diff(__be32 *from, u32 from_size, __be32 *to, u32
to_size, __wsum seed)
Description
Compute a checksum difference, from the raw buffer
pointed by from, of length from_size (that must be
a multiple of 4), towards the raw buffer pointed by
to, of size to_size (same remark). An optional seed
can be added to the value (this can be cascaded,
the seed may come from a previous call to the
helper).
This is flexible enough to be used in several ways:
• With from_size == 0, to_size > 0 and seed set to
checksum, it can be used when pushing new data.
• With from_size > 0, to_size == 0 and seed set to
checksum, it can be used when removing data from
a packet.
• With from_size > 0, to_size > 0 and seed set to
0, it can be used to compute a diff. Note that
from_size and to_size do not need to be equal.
This helper can be used in combination with
bpf_l3_csum_replace() and bpf_l4_csum_replace(), to
which one can feed in the difference computed with
bpf_csum_diff().
Return The checksum result, or a negative error code in
case of failure.
long bpf_skb_get_tunnel_opt(struct sk_buff *skb, void *opt, u32
size)
Description
Retrieve tunnel options metadata for the packet
associated to skb, and store the raw tunnel option
data to the buffer opt of size.
This helper can be used with encapsulation devices
that can operate in "collect metadata" mode (please
refer to the related note in the description of
bpf_skb_get_tunnel_key() for more details). A
particular example where this can be used is in
combination with the Geneve encapsulation protocol,
where it allows for pushing (with
bpf_skb_get_tunnel_opt() helper) and retrieving
arbitrary TLVs (Type-Length-Value headers) from the
eBPF program. This allows for full customization of
these headers.
Return The size of the option data retrieved.
long bpf_skb_set_tunnel_opt(struct sk_buff *skb, void *opt, u32
size)
Description
Set tunnel options metadata for the packet
associated to skb to the option data contained in
the raw buffer opt of size.
See also the description of the
bpf_skb_get_tunnel_opt() helper for additional
information.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_change_proto(struct sk_buff *skb, __be16 proto, u64
flags)
Description
Change the protocol of the skb to proto. Currently
supported are transition from IPv4 to IPv6, and
from IPv6 to IPv4. The helper takes care of the
groundwork for the transition, including resizing
the socket buffer. The eBPF program is expected to
fill the new headers, if any, via skb_store_bytes()
and to recompute the checksums with
bpf_l3_csum_replace() and bpf_l4_csum_replace().
The main case for this helper is to perform NAT64
operations out of an eBPF program.
Internally, the GSO type is marked as dodgy so that
headers are checked and segments are recalculated
by the GSO/GRO engine. The size for GSO target is
adapted as well.
All values for flags are reserved for future usage,
and must be left at zero.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_change_type(struct sk_buff *skb, u32 type)
Description
Change the packet type for the packet associated to
skb. This comes down to setting skb->pkt_type to
type, except the eBPF program does not have a write
access to skb->pkt_type beside this helper. Using a
helper here allows for graceful handling of errors.
The major use case is to change incoming skb*s to
**PACKET_HOST* in a programmatic way instead of
having to recirculate via redirect(...,
BPF_F_INGRESS), for example.
Note that type only allows certain values. At this
time, they are:
PACKET_HOST
Packet is for us.
PACKET_BROADCAST
Send packet to all.
PACKET_MULTICAST
Send packet to group.
PACKET_OTHERHOST
Send packet to someone else.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_under_cgroup(struct sk_buff *skb, struct bpf_map
*map, u32 index)
Description
Check whether skb is a descendant of the cgroup2
held by map of type BPF_MAP_TYPE_CGROUP_ARRAY, at
index.
Return The return value depends on the result of the test,
and can be:
• 0, if the skb failed the cgroup2 descendant test.
• 1, if the skb succeeded the cgroup2 descendant
test.
• A negative error code, if an error occurred.
u32 bpf_get_hash_recalc(struct sk_buff *skb)
Description
Retrieve the hash of the packet, skb->hash. If it
is not set, in particular if the hash was cleared
due to mangling, recompute this hash. Later
accesses to the hash can be done directly with
skb->hash.
Calling bpf_set_hash_invalid(), changing a packet
prototype with bpf_skb_change_proto(), or calling
bpf_skb_store_bytes() with the
BPF_F_INVALIDATE_HASH are actions susceptible to
clear the hash and to trigger a new computation for
the next call to bpf_get_hash_recalc().
Return The 32-bit hash.
u64 bpf_get_current_task(void)
Return A pointer to the current task struct.
long bpf_probe_write_user(void *dst, const void *src, u32 len)
Description
Attempt in a safe way to write len bytes from the
buffer src to dst in memory. It only works for
threads that are in user context, and dst must be a
valid user space address.
This helper should not be used to implement any
kind of security mechanism because of TOC-TOU
attacks, but rather to debug, divert, and
manipulate execution of semi-cooperative processes.
Keep in mind that this feature is meant for
experiments, and it has a risk of crashing the
system and running programs. Therefore, when an
eBPF program using this helper is attached, a
warning including PID and process name is printed
to kernel logs.
Return 0 on success, or a negative error in case of
failure.
long bpf_current_task_under_cgroup(struct bpf_map *map, u32
index)
Description
Check whether the probe is being run is the context
of a given subset of the cgroup2 hierarchy. The
cgroup2 to test is held by map of type
BPF_MAP_TYPE_CGROUP_ARRAY, at index.
Return The return value depends on the result of the test,
and can be:
• 0, if the skb task belongs to the cgroup2.
• 1, if the skb task does not belong to the
cgroup2.
• A negative error code, if an error occurred.
long bpf_skb_change_tail(struct sk_buff *skb, u32 len, u64 flags)
Description
Resize (trim or grow) the packet associated to skb
to the new len. The flags are reserved for future
usage, and must be left at zero.
The basic idea is that the helper performs the
needed work to change the size of the packet, then
the eBPF program rewrites the rest via helpers like
bpf_skb_store_bytes(), bpf_l3_csum_replace(),
bpf_l3_csum_replace() and others. This helper is a
slow path utility intended for replies with control
messages. And because it is targeted for slow path,
the helper itself can afford to be slow: it
implicitly linearizes, unclones and drops offloads
from the skb.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_pull_data(struct sk_buff *skb, u32 len)
Description
Pull in non-linear data in case the skb is
non-linear and not all of len are part of the
linear section. Make len bytes from skb readable
and writable. If a zero value is passed for len,
then the whole length of the skb is pulled.
This helper is only needed for reading and writing
with direct packet access.
For direct packet access, testing that offsets to
access are within packet boundaries (test on
skb->data_end) is susceptible to fail if offsets
are invalid, or if the requested data is in
non-linear parts of the skb. On failure the program
can just bail out, or in the case of a non-linear
buffer, use a helper to make the data available.
The bpf_skb_load_bytes() helper is a first solution
to access the data. Another one consists in using
bpf_skb_pull_data to pull in once the non-linear
parts, then retesting and eventually access the
data.
At the same time, this also makes sure the skb is
uncloned, which is a necessary condition for direct
write. As this needs to be an invariant for the
write part only, the verifier detects writes and
adds a prologue that is calling bpf_skb_pull_data()
to effectively unclone the skb from the very
beginning in case it is indeed cloned.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
s64 bpf_csum_update(struct sk_buff *skb, __wsum csum)
Description
Add the checksum csum into skb->csum in case the
driver has supplied a checksum for the entire
packet into that field. Return an error otherwise.
This helper is intended to be used in combination
with bpf_csum_diff(), in particular when the
checksum needs to be updated after data has been
written into the packet through direct packet
access.
Return The checksum on success, or a negative error code
in case of failure.
void bpf_set_hash_invalid(struct sk_buff *skb)
Description
Invalidate the current skb->hash. It can be used
after mangling on headers through direct packet
access, in order to indicate that the hash is
outdated and to trigger a recalculation the next
time the kernel tries to access this hash or when
the bpf_get_hash_recalc() helper is called.
long bpf_get_numa_node_id(void)
Description
Return the id of the current NUMA node. The primary
use case for this helper is the selection of
sockets for the local NUMA node, when the program
is attached to sockets using the
SO_ATTACH_REUSEPORT_EBPF option (see also
socket(7)), but the helper is also available to
other eBPF program types, similarly to
bpf_get_smp_processor_id().
Return The id of current NUMA node.
long bpf_skb_change_head(struct sk_buff *skb, u32 len, u64 flags)
Description
Grows headroom of packet associated to skb and
adjusts the offset of the MAC header accordingly,
adding len bytes of space. It automatically extends
and reallocates memory as required.
This helper can be used on a layer 3 skb to push a
MAC header for redirection into a layer 2 device.
All values for flags are reserved for future usage,
and must be left at zero.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_xdp_adjust_head(struct xdp_buff *xdp_md, int delta)
Description
Adjust (move) xdp_md->data by delta bytes. Note
that it is possible to use a negative value for
delta. This helper can be used to prepare the
packet for pushing or popping headers.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_probe_read_str(void *dst, u32 size, const void
*unsafe_ptr)
Description
Copy a NUL terminated string from an unsafe kernel
address unsafe_ptr to dst. See
bpf_probe_read_kernel_str() for more details.
Generally, use bpf_probe_read_user_str() or
bpf_probe_read_kernel_str() instead.
Return On success, the strictly positive length of the
string, including the trailing NUL character. On
error, a negative value.
u64 bpf_get_socket_cookie(struct sk_buff *skb)
Description
If the struct sk_buff pointed by skb has a known
socket, retrieve the cookie (generated by the
kernel) of this socket. If no cookie has been set
yet, generate a new cookie. Once generated, the
socket cookie remains stable for the life of the
socket. This helper can be useful for monitoring
per socket networking traffic statistics as it
provides a global socket identifier that can be
assumed unique.
Return A 8-byte long non-decreasing number on success, or
0 if the socket field is missing inside skb.
u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
Description
Equivalent to bpf_get_socket_cookie() helper that
accepts skb, but gets socket from struct
bpf_sock_addr context.
Return A 8-byte long non-decreasing number.
u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)
Description
Equivalent to bpf_get_socket_cookie() helper that
accepts skb, but gets socket from struct
bpf_sock_ops context.
Return A 8-byte long non-decreasing number.
u32 bpf_get_socket_uid(struct sk_buff *skb)
Return The owner UID of the socket associated to skb. If
the socket is NULL, or if it is not a full socket
(i.e. if it is a time-wait or a request socket
instead), overflowuid value is returned (note that
overflowuid might also be the actual UID value for
the socket).
long bpf_set_hash(struct sk_buff *skb, u32 hash)
Description
Set the full hash for skb (set the field skb->hash)
to value hash.
Return 0
long bpf_setsockopt(void *bpf_socket, int level, int optname,
void *optval, int optlen)
Description
Emulate a call to setsockopt() on the socket
associated to bpf_socket, which must be a full
socket. The level at which the option resides and
the name optname of the option must be specified,
see setsockopt(2) for more information. The option
value of length optlen is pointed by optval.
bpf_socket should be one of the following:
• struct bpf_sock_ops for BPF_PROG_TYPE_SOCK_OPS.
• struct bpf_sock_addr for BPF_CGROUP_INET4_CONNECT
and BPF_CGROUP_INET6_CONNECT.
This helper actually implements a subset of
setsockopt(). It supports the following levels:
• SOL_SOCKET, which supports the following
optnames: SO_RCVBUF, SO_SNDBUF,
SO_MAX_PACING_RATE, SO_PRIORITY, SO_RCVLOWAT,
SO_MARK, SO_BINDTODEVICE, SO_KEEPALIVE.
• IPPROTO_TCP, which supports the following
optnames: TCP_CONGESTION, TCP_BPF_IW,
TCP_BPF_SNDCWND_CLAMP, TCP_SAVE_SYN,
TCP_KEEPIDLE, TCP_KEEPINTVL, TCP_KEEPCNT,
TCP_SYNCNT, TCP_USER_TIMEOUT.
• IPPROTO_IP, which supports optname IP_TOS.
• IPPROTO_IPV6, which supports optname IPV6_TCLASS.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_adjust_room(struct sk_buff *skb, s32 len_diff, u32
mode, u64 flags)
Description
Grow or shrink the room for data in the packet
associated to skb by len_diff, and according to the
selected mode.
By default, the helper will reset any offloaded
checksum indicator of the skb to CHECKSUM_NONE.
This can be avoided by the following flag:
• BPF_F_ADJ_ROOM_NO_CSUM_RESET: Do not reset
offloaded checksum data of the skb to
CHECKSUM_NONE.
There are two supported modes at this time:
• BPF_ADJ_ROOM_MAC: Adjust room at the mac layer
(room space is added or removed below the layer 2
header).
• BPF_ADJ_ROOM_NET: Adjust room at the network
layer (room space is added or removed below the
layer 3 header).
The following flags are supported at this time:
• BPF_F_ADJ_ROOM_FIXED_GSO: Do not adjust gso_size.
Adjusting mss in this way is not allowed for
datagrams.
• BPF_F_ADJ_ROOM_ENCAP_L3_IPV4,
BPF_F_ADJ_ROOM_ENCAP_L3_IPV6: Any new space is
reserved to hold a tunnel header. Configure skb
offsets and other fields accordingly.
• BPF_F_ADJ_ROOM_ENCAP_L4_GRE,
BPF_F_ADJ_ROOM_ENCAP_L4_UDP: Use with ENCAP_L3
flags to further specify the tunnel type.
• BPF_F_ADJ_ROOM_ENCAP_L2(len): Use with
ENCAP_L3/L4 flags to further specify the tunnel
type; len is the length of the inner MAC header.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags)
Description
Redirect the packet to the endpoint referenced by
map at index key. Depending on its type, this map
can contain references to net devices (for
forwarding packets through other ports), or to CPUs
(for redirecting XDP frames to another CPU; but
this is only implemented for native XDP (with
driver support) as of this writing).
The lower two bits of flags are used as the return
code if the map lookup fails. This is so that the
return value can be one of the XDP program return
codes up to XDP_TX, as chosen by the caller. Any
higher bits in the flags argument must be unset.
See also bpf_redirect(), which only supports
redirecting to an ifindex, but doesn't require a
map to do so.
Return XDP_REDIRECT on success, or the value of the two
lower bits of the flags argument on error.
long bpf_sk_redirect_map(struct sk_buff *skb, struct bpf_map
*map, u32 key, u64 flags)
Description
Redirect the packet to the socket referenced by map
(of type BPF_MAP_TYPE_SOCKMAP) at index key. Both
ingress and egress interfaces can be used for
redirection. The BPF_F_INGRESS value in flags is
used to make the distinction (ingress path is
selected if the flag is present, egress path
otherwise). This is the only flag supported for
now.
Return SK_PASS on success, or SK_DROP on error.
long bpf_sock_map_update(struct bpf_sock_ops *skops, struct
bpf_map *map, void *key, u64 flags)
Description
Add an entry to, or update a map referencing
sockets. The skops is used as a new value for the
entry associated to key. flags is one of:
BPF_NOEXIST
The entry for key must not exist in the map.
BPF_EXIST
The entry for key must already exist in the
map.
BPF_ANY
No condition on the existence of the entry
for key.
If the map has eBPF programs (parser and verdict),
those will be inherited by the socket being added.
If the socket is already attached to eBPF programs,
this results in an error.
Return 0 on success, or a negative error in case of
failure.
long bpf_xdp_adjust_meta(struct xdp_buff *xdp_md, int delta)
Description
Adjust the address pointed by xdp_md->data_meta by
delta (which can be positive or negative). Note
that this operation modifies the address stored in
xdp_md->data, so the latter must be loaded only
after the helper has been called.
The use of xdp_md->data_meta is optional and
programs are not required to use it. The rationale
is that when the packet is processed with XDP (e.g.
as DoS filter), it is possible to push further meta
data along with it before passing to the stack, and
to give the guarantee that an ingress eBPF program
attached as a TC classifier on the same device can
pick this up for further post-processing. Since TC
works with socket buffers, it remains possible to
set from XDP the mark or priority pointers, or
other pointers for the socket buffer. Having this
scratch space generic and programmable allows for
more flexibility as the user is free to store
whatever meta data they need.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_perf_event_read_value(struct bpf_map *map, u64 flags,
struct bpf_perf_event_value *buf, u32 buf_size)
Description
Read the value of a perf event counter, and store
it into buf of size buf_size. This helper relies on
a map of type BPF_MAP_TYPE_PERF_EVENT_ARRAY. The
nature of the perf event counter is selected when
map is updated with perf event file descriptors.
The map is an array whose size is the number of
available CPUs, and each cell contains a value
relative to one CPU. The value to retrieve is
indicated by flags, that contains the index of the
CPU to look up, masked with BPF_F_INDEX_MASK.
Alternatively, flags can be set to
BPF_F_CURRENT_CPU to indicate that the value for
the current CPU should be retrieved.
This helper behaves in a way close to
bpf_perf_event_read() helper, save that instead of
just returning the value observed, it fills the buf
structure. This allows for additional data to be
retrieved: in particular, the enabled and running
times (in buf->enabled and buf->running,
respectively) are copied. In general,
bpf_perf_event_read_value() is recommended over
bpf_perf_event_read(), which has some ABI issues
and provides fewer functionalities.
These values are interesting, because hardware PMU
(Performance Monitoring Unit) counters are limited
resources. When there are more PMU based perf
events opened than available counters, kernel will
multiplex these events so each event gets certain
percentage (but not all) of the PMU time. In case
that multiplexing happens, the number of samples or
counter value will not reflect the case compared to
when no multiplexing occurs. This makes comparison
between different runs difficult. Typically, the
counter value should be normalized before comparing
to other experiments. The usual normalization is
done as follows.
normalized_counter = counter * t_enabled / t_running
Where t_enabled is the time enabled for event and
t_running is the time running for event since last
normalization. The enabled and running times are
accumulated since the perf event open. To achieve
scaling factor between two invocations of an eBPF
program, users can use CPU id as the key (which is
typical for perf array usage model) to remember the
previous value and do the calculation inside the
eBPF program.
Return 0 on success, or a negative error in case of
failure.
long bpf_perf_prog_read_value(struct bpf_perf_event_data *ctx,
struct bpf_perf_event_value *buf, u32 buf_size)
Description
For en eBPF program attached to a perf event,
retrieve the value of the event counter associated
to ctx and store it in the structure pointed by buf
and of size buf_size. Enabled and running times are
also stored in the structure (see description of
helper bpf_perf_event_read_value() for more
details).
Return 0 on success, or a negative error in case of
failure.
long bpf_getsockopt(void *bpf_socket, int level, int optname,
void *optval, int optlen)
Description
Emulate a call to getsockopt() on the socket
associated to bpf_socket, which must be a full
socket. The level at which the option resides and
the name optname of the option must be specified,
see getsockopt(2) for more information. The
retrieved value is stored in the structure pointed
by opval and of length optlen.
bpf_socket should be one of the following:
• struct bpf_sock_ops for BPF_PROG_TYPE_SOCK_OPS.
• struct bpf_sock_addr for BPF_CGROUP_INET4_CONNECT
and BPF_CGROUP_INET6_CONNECT.
This helper actually implements a subset of
getsockopt(). It supports the following levels:
• IPPROTO_TCP, which supports optname
TCP_CONGESTION.
• IPPROTO_IP, which supports optname IP_TOS.
• IPPROTO_IPV6, which supports optname IPV6_TCLASS.
Return 0 on success, or a negative error in case of
failure.
long bpf_override_return(struct pt_regs *regs, u64 rc)
Description
Used for error injection, this helper uses kprobes
to override the return value of the probed
function, and to set it to rc. The first argument
is the context regs on which the kprobe works.
This helper works by setting the PC (program
counter) to an override function which is run in
place of the original probed function. This means
the probed function is not run at all. The
replacement function just returns with the required
value.
This helper has security implications, and thus is
subject to restrictions. It is only available if
the kernel was compiled with the
CONFIG_BPF_KPROBE_OVERRIDE configuration option,
and in this case it only works on functions tagged
with ALLOW_ERROR_INJECTION in the kernel code.
Also, the helper is only available for the
architectures having the
CONFIG_FUNCTION_ERROR_INJECTION option. As of this
writing, x86 architecture is the only one to
support this feature.
Return 0
long bpf_sock_ops_cb_flags_set(struct bpf_sock_ops *bpf_sock, int
argval)
Description
Attempt to set the value of the
bpf_sock_ops_cb_flags field for the full TCP socket
associated to bpf_sock_ops to argval.
The primary use of this field is to determine if
there should be calls to eBPF programs of type
BPF_PROG_TYPE_SOCK_OPS at various points in the TCP
code. A program of the same type can change its
value, per connection and as necessary, when the
connection is established. This field is directly
accessible for reading, but this helper must be
used for updates in order to return an error if an
eBPF program tries to set a callback that is not
supported in the current kernel.
argval is a flag array which can combine these
flags:
• BPF_SOCK_OPS_RTO_CB_FLAG (retransmission time
out)
• BPF_SOCK_OPS_RETRANS_CB_FLAG (retransmission)
• BPF_SOCK_OPS_STATE_CB_FLAG (TCP state change)
• BPF_SOCK_OPS_RTT_CB_FLAG (every RTT)
Therefore, this function can be used to clear a
callback flag by setting the appropriate bit to
zero. e.g. to disable the RTO callback:
bpf_sock_ops_cb_flags_set(bpf_sock,
bpf_sock->bpf_sock_ops_cb_flags &
~BPF_SOCK_OPS_RTO_CB_FLAG)
Here are some examples of where one could call such
eBPF program:
• When RTO fires.
• When a packet is retransmitted.
• When the connection terminates.
• When a packet is sent.
• When a packet is received.
Return Code -EINVAL if the socket is not a full TCP
socket; otherwise, a positive number containing the
bits that could not be set is returned (which comes
down to 0 if all bits were set as required).
long bpf_msg_redirect_map(struct sk_msg_buff *msg, struct bpf_map
*map, u32 key, u64 flags)
Description
This helper is used in programs implementing
policies at the socket level. If the message msg is
allowed to pass (i.e. if the verdict eBPF program
returns SK_PASS), redirect it to the socket
referenced by map (of type BPF_MAP_TYPE_SOCKMAP) at
index key. Both ingress and egress interfaces can
be used for redirection. The BPF_F_INGRESS value in
flags is used to make the distinction (ingress path
is selected if the flag is present, egress path
otherwise). This is the only flag supported for
now.
Return SK_PASS on success, or SK_DROP on error.
long bpf_msg_apply_bytes(struct sk_msg_buff *msg, u32 bytes)
Description
For socket policies, apply the verdict of the eBPF
program to the next bytes (number of bytes) of
message msg.
For example, this helper can be used in the
following cases:
• A single sendmsg() or sendfile() system call
contains multiple logical messages that the eBPF
program is supposed to read and for which it
should apply a verdict.
• An eBPF program only cares to read the first
bytes of a msg. If the message has a large
payload, then setting up and calling the eBPF
program repeatedly for all bytes, even though the
verdict is already known, would create
unnecessary overhead.
When called from within an eBPF program, the helper
sets a counter internal to the BPF infrastructure,
that is used to apply the last verdict to the next
bytes. If bytes is smaller than the current data
being processed from a sendmsg() or sendfile()
system call, the first bytes will be sent and the
eBPF program will be re-run with the pointer for
start of data pointing to byte number bytes + 1. If
bytes is larger than the current data being
processed, then the eBPF verdict will be applied to
multiple sendmsg() or sendfile() calls until bytes
are consumed.
Note that if a socket closes with the internal
counter holding a non-zero value, this is not a
problem because data is not being buffered for
bytes and is sent as it is received.
Return 0
long bpf_msg_cork_bytes(struct sk_msg_buff *msg, u32 bytes)
Description
For socket policies, prevent the execution of the
verdict eBPF program for message msg until bytes
(byte number) have been accumulated.
This can be used when one needs a specific number
of bytes before a verdict can be assigned, even if
the data spans multiple sendmsg() or sendfile()
calls. The extreme case would be a user calling
sendmsg() repeatedly with 1-byte long message
segments. Obviously, this is bad for performance,
but it is still valid. If the eBPF program needs
bytes bytes to validate a header, this helper can
be used to prevent the eBPF program to be called
again until bytes have been accumulated.
Return 0
long bpf_msg_pull_data(struct sk_msg_buff *msg, u32 start, u32
end, u64 flags)
Description
For socket policies, pull in non-linear data from
user space for msg and set pointers msg->data and
msg->data_end to start and end bytes offsets into
msg, respectively.
If a program of type BPF_PROG_TYPE_SK_MSG is run on
a msg it can only parse data that the (data,
data_end) pointers have already consumed. For
sendmsg() hooks this is likely the first
scatterlist element. But for calls relying on the
sendpage handler (e.g. sendfile()) this will be the
range (0, 0) because the data is shared with user
space and by default the objective is to avoid
allowing user space to modify data while (or after)
eBPF verdict is being decided. This helper can be
used to pull in data and to set the start and end
pointer to given values. Data will be copied if
necessary (i.e. if data was not linear and if start
and end pointers do not point to the same chunk).
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
All values for flags are reserved for future usage,
and must be left at zero.
Return 0 on success, or a negative error in case of
failure.
long bpf_bind(struct bpf_sock_addr *ctx, struct sockaddr *addr,
int addr_len)
Description
Bind the socket associated to ctx to the address
pointed by addr, of length addr_len. This allows
for making outgoing connection from the desired IP
address, which can be useful for example when all
processes inside a cgroup should use one single IP
address on a host that has multiple IP configured.
This helper works for IPv4 and IPv6, TCP and UDP
sockets. The domain (addr->sa_family) must be
AF_INET (or AF_INET6). It's advised to pass zero
port (sin_port or sin6_port) which triggers
IP_BIND_ADDRESS_NO_PORT-like behavior and lets the
kernel efficiently pick up an unused port as long
as 4-tuple is unique. Passing non-zero port might
lead to degraded performance.
Return 0 on success, or a negative error in case of
failure.
long bpf_xdp_adjust_tail(struct xdp_buff *xdp_md, int delta)
Description
Adjust (move) xdp_md->data_end by delta bytes. It
is possible to both shrink and grow the packet
tail. Shrink done via delta being a negative
integer.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_skb_get_xfrm_state(struct sk_buff *skb, u32 index,
struct bpf_xfrm_state *xfrm_state, u32 size, u64 flags)
Description
Retrieve the XFRM state (IP transform framework,
see also ip-xfrm(8)) at index in XFRM "security
path" for skb.
The retrieved value is stored in the struct
bpf_xfrm_state pointed by xfrm_state and of length
size.
All values for flags are reserved for future usage,
and must be left at zero.
This helper is available only if the kernel was
compiled with CONFIG_XFRM configuration option.
Return 0 on success, or a negative error in case of
failure.
long bpf_get_stack(void *ctx, void *buf, u32 size, u64 flags)
Description
Return a user or a kernel stack in bpf program
provided buffer. To achieve this, the helper needs
ctx, which is a pointer to the context on which the
tracing program is executed. To store the
stacktrace, the bpf program provides buf with a
nonnegative size.
The last argument, flags, holds the number of stack
frames to skip (from 0 to 255), masked with
BPF_F_SKIP_FIELD_MASK. The next bits can be used to
set the following flags:
BPF_F_USER_STACK
Collect a user space stack instead of a
kernel stack.
BPF_F_USER_BUILD_ID
Collect buildid+offset instead of ips for
user stack, only valid if BPF_F_USER_STACK
is also specified.
bpf_get_stack() can collect up to
PERF_MAX_STACK_DEPTH both kernel and user frames,
subject to sufficient large buffer size. Note that
this limit can be controlled with the sysctl
program, and that it should be manually increased
in order to profile long user stacks (such as
stacks for Java programs). To do so, use:
# sysctl kernel.perf_event_max_stack=<new value>
Return A non-negative value equal to or less than size on
success, or a negative error in case of failure.
long bpf_skb_load_bytes_relative(const void *skb, u32 offset,
void *to, u32 len, u32 start_header)
Description
This helper is similar to bpf_skb_load_bytes() in
that it provides an easy way to load len bytes from
offset from the packet associated to skb, into the
buffer pointed by to. The difference to
bpf_skb_load_bytes() is that a fifth argument
start_header exists in order to select a base
offset to start from. start_header can be one of:
BPF_HDR_START_MAC
Base offset to load data from is skb's mac
header.
BPF_HDR_START_NET
Base offset to load data from is skb's
network header.
In general, "direct packet access" is the preferred
method to access packet data, however, this helper
is in particular useful in socket filters where
skb->data does not always point to the start of the
mac header and where "direct packet access" is not
available.
Return 0 on success, or a negative error in case of
failure.
long bpf_fib_lookup(void *ctx, struct bpf_fib_lookup *params, int
plen, u32 flags)
Description
Do FIB lookup in kernel tables using parameters in
params. If lookup is successful and result shows
packet is to be forwarded, the neighbor tables are
searched for the nexthop. If successful (ie., FIB
lookup shows forwarding and nexthop is resolved),
the nexthop address is returned in ipv4_dst or
ipv6_dst based on family, smac is set to mac
address of egress device, dmac is set to nexthop
mac address, rt_metric is set to metric from route
(IPv4/IPv6 only), and ifindex is set to the device
index of the nexthop from the FIB lookup.
plen argument is the size of the passed in struct.
flags argument can be a combination of one or more
of the following values:
BPF_FIB_LOOKUP_DIRECT
Do a direct table lookup vs full lookup
using FIB rules.
BPF_FIB_LOOKUP_OUTPUT
Perform lookup from an egress perspective
(default is ingress).
ctx is either struct xdp_md for XDP programs or
struct sk_buff tc cls_act programs.
Return
• < 0 if any input argument is invalid
• 0 on success (packet is forwarded, nexthop
neighbor exists)
• > 0 one of BPF_FIB_LKUP_RET_ codes explaining why
the packet is not forwarded or needs assist from
full stack
long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct
bpf_map *map, void *key, u64 flags)
Description
Add an entry to, or update a sockhash map
referencing sockets. The skops is used as a new
value for the entry associated to key. flags is one
of:
BPF_NOEXIST
The entry for key must not exist in the map.
BPF_EXIST
The entry for key must already exist in the
map.
BPF_ANY
No condition on the existence of the entry
for key.
If the map has eBPF programs (parser and verdict),
those will be inherited by the socket being added.
If the socket is already attached to eBPF programs,
this results in an error.
Return 0 on success, or a negative error in case of
failure.
long bpf_msg_redirect_hash(struct sk_msg_buff *msg, struct
bpf_map *map, void *key, u64 flags)
Description
This helper is used in programs implementing
policies at the socket level. If the message msg is
allowed to pass (i.e. if the verdict eBPF program
returns SK_PASS), redirect it to the socket
referenced by map (of type BPF_MAP_TYPE_SOCKHASH)
using hash key. Both ingress and egress interfaces
can be used for redirection. The BPF_F_INGRESS
value in flags is used to make the distinction
(ingress path is selected if the flag is present,
egress path otherwise). This is the only flag
supported for now.
Return SK_PASS on success, or SK_DROP on error.
long bpf_sk_redirect_hash(struct sk_buff *skb, struct bpf_map
*map, void *key, u64 flags)
Description
This helper is used in programs implementing
policies at the skb socket level. If the sk_buff
skb is allowed to pass (i.e. if the verdict eBPF
program returns SK_PASS), redirect it to the socket
referenced by map (of type BPF_MAP_TYPE_SOCKHASH)
using hash key. Both ingress and egress interfaces
can be used for redirection. The BPF_F_INGRESS
value in flags is used to make the distinction
(ingress path is selected if the flag is present,
egress otherwise). This is the only flag supported
for now.
Return SK_PASS on success, or SK_DROP on error.
long bpf_lwt_push_encap(struct sk_buff *skb, u32 type, void *hdr,
u32 len)
Description
Encapsulate the packet associated to skb within a
Layer 3 protocol header. This header is provided in
the buffer at address hdr, with len its size in
bytes. type indicates the protocol of the header
and can be one of:
BPF_LWT_ENCAP_SEG6
IPv6 encapsulation with Segment Routing
Header (struct ipv6_sr_hdr). hdr only
contains the SRH, the IPv6 header is
computed by the kernel.
BPF_LWT_ENCAP_SEG6_INLINE
Only works if skb contains an IPv6 packet.
Insert a Segment Routing Header (struct
ipv6_sr_hdr) inside the IPv6 header.
BPF_LWT_ENCAP_IP
IP encapsulation (GRE/GUE/IPIP/etc). The
outer header must be IPv4 or IPv6, followed
by zero or more additional headers, up to
LWT_BPF_MAX_HEADROOM total bytes in all
prepended headers. Please note that if
skb_is_gso(skb) is true, no more than two
headers can be prepended, and the inner
header, if present, should be either GRE or
UDP/GUE.
BPF_LWT_ENCAP_SEG6* types can be called by BPF
programs of type BPF_PROG_TYPE_LWT_IN;
BPF_LWT_ENCAP_IP type can be called by bpf programs
of types BPF_PROG_TYPE_LWT_IN and
BPF_PROG_TYPE_LWT_XMIT.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_lwt_seg6_store_bytes(struct sk_buff *skb, u32 offset,
const void *from, u32 len)
Description
Store len bytes from address from into the packet
associated to skb, at offset. Only the flags, tag
and TLVs inside the outermost IPv6 Segment Routing
Header can be modified through this helper.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_lwt_seg6_adjust_srh(struct sk_buff *skb, u32 offset, s32
delta)
Description
Adjust the size allocated to TLVs in the outermost
IPv6 Segment Routing Header contained in the packet
associated to skb, at position offset by delta
bytes. Only offsets after the segments are
accepted. delta can be as well positive (growing)
as negative (shrinking).
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_lwt_seg6_action(struct sk_buff *skb, u32 action, void
*param, u32 param_len)
Description
Apply an IPv6 Segment Routing action of type action
to the packet associated to skb. Each action takes
a parameter contained at address param, and of
length param_len bytes. action can be one of:
SEG6_LOCAL_ACTION_END_X
End.X action: Endpoint with Layer-3
cross-connect. Type of param: struct
in6_addr.
SEG6_LOCAL_ACTION_END_T
End.T action: Endpoint with specific IPv6
table lookup. Type of param: int.
SEG6_LOCAL_ACTION_END_B6
End.B6 action: Endpoint bound to an SRv6
policy. Type of param: struct ipv6_sr_hdr.
SEG6_LOCAL_ACTION_END_B6_ENCAP
End.B6.Encap action: Endpoint bound to an
SRv6 encapsulation policy. Type of param:
struct ipv6_sr_hdr.
A call to this helper is susceptible to change the
underlying packet buffer. Therefore, at load time,
all checks on pointers previously done by the
verifier are invalidated and must be performed
again, if the helper is used in combination with
direct packet access.
Return 0 on success, or a negative error in case of
failure.
long bpf_rc_repeat(void *ctx)
Description
This helper is used in programs implementing IR
decoding, to report a successfully decoded repeat
key message. This delays the generation of a key up
event for previously generated key down event.
Some IR protocols like NEC have a special IR
message for repeating last button, for when a
button is held down.
The ctx should point to the lirc sample as passed
into the program.
This helper is only available is the kernel was
compiled with the CONFIG_BPF_LIRC_MODE2
configuration option set to "y".
Return 0
long bpf_rc_keydown(void *ctx, u32 protocol, u64 scancode, u32
toggle)
Description
This helper is used in programs implementing IR
decoding, to report a successfully decoded key
press with scancode, toggle value in the given
protocol. The scancode will be translated to a
keycode using the rc keymap, and reported as an
input key down event. After a period a key up event
is generated. This period can be extended by
calling either bpf_rc_keydown() again with the same
values, or calling bpf_rc_repeat().
Some protocols include a toggle bit, in case the
button was released and pressed again between
consecutive scancodes.
The ctx should point to the lirc sample as passed
into the program.
The protocol is the decoded protocol number (see
enum rc_proto for some predefined values).
This helper is only available is the kernel was
compiled with the CONFIG_BPF_LIRC_MODE2
configuration option set to "y".
Return 0
u64 bpf_skb_cgroup_id(struct sk_buff *skb)
Description
Return the cgroup v2 id of the socket associated
with the skb. This is roughly similar to the
bpf_get_cgroup_classid() helper for cgroup v1 by
providing a tag resp. identifier that can be
matched on or used for map lookups e.g. to
implement policy. The cgroup v2 id of a given path
in the hierarchy is exposed in user space through
the f_handle API in order to get to the same 64-bit
id.
This helper can be used on TC egress path, but not
on ingress, and is available only if the kernel was
compiled with the CONFIG_SOCK_CGROUP_DATA
configuration option.
Return The id is returned or 0 in case the id could not be
retrieved.
u64 bpf_get_current_cgroup_id(void)
Return A 64-bit integer containing the current cgroup id
based on the cgroup within which the current task
is running.
void *bpf_get_local_storage(void *map, u64 flags)
Description
Get the pointer to the local storage area. The
type and the size of the local storage is defined
by the map argument. The flags meaning is specific
for each map type, and has to be 0 for cgroup local
storage.
Depending on the BPF program type, a local storage
area can be shared between multiple instances of
the BPF program, running simultaneously.
A user should care about the synchronization by
himself. For example, by using the BPF_STX_XADD
instruction to alter the shared data.
Return A pointer to the local storage area.
long bpf_sk_select_reuseport(struct sk_reuseport_md *reuse,
struct bpf_map *map, void *key, u64 flags)
Description
Select a SO_REUSEPORT socket from a
BPF_MAP_TYPE_REUSEPORT_ARRAY map. It checks the
selected socket is matching the incoming request in
the socket buffer.
Return 0 on success, or a negative error in case of
failure.
u64 bpf_skb_ancestor_cgroup_id(struct sk_buff *skb, int
ancestor_level)
Description
Return id of cgroup v2 that is ancestor of cgroup
associated with the skb at the ancestor_level. The
root cgroup is at ancestor_level zero and each step
down the hierarchy increments the level. If
ancestor_level == level of cgroup associated with
skb, then return value will be same as that of
bpf_skb_cgroup_id().
The helper is useful to implement policies based on
cgroups that are upper in hierarchy than immediate
cgroup associated with skb.
The format of returned id and helper limitations
are same as in bpf_skb_cgroup_id().
Return The id is returned or 0 in case the id could not be
retrieved.
struct bpf_sock *bpf_sk_lookup_tcp(void *ctx, struct
bpf_sock_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
Description
Look for TCP socket matching tuple, optionally in a
child network namespace netns. The return value
must be checked, and if non-NULL, released via
bpf_sk_release().
The ctx should point to the context of the program,
such as the skb or socket (depending on the hook in
use). This is used to determine the base network
namespace for the lookup.
tuple_size must be one of:
sizeof(tuple->ipv4)
Look for an IPv4 socket.
sizeof(tuple->ipv6)
Look for an IPv6 socket.
If the netns is a negative signed 32-bit integer,
then the socket lookup table in the netns
associated with the ctx will be used. For the TC
hooks, this is the netns of the device in the skb.
For socket hooks, this is the netns of the socket.
If netns is any other signed 32-bit value greater
than or equal to zero then it specifies the ID of
the netns relative to the netns associated with the
ctx. netns values beyond the range of 32-bit
integers are reserved for future use.
All values for flags are reserved for future usage,
and must be left at zero.
This helper is available only if the kernel was
compiled with CONFIG_NET configuration option.
Return Pointer to struct bpf_sock, or NULL in case of
failure. For sockets with reuseport option, the
struct bpf_sock result is from reuse->socks[] using
the hash of the tuple.
struct bpf_sock *bpf_sk_lookup_udp(void *ctx, struct
bpf_sock_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
Description
Look for UDP socket matching tuple, optionally in a
child network namespace netns. The return value
must be checked, and if non-NULL, released via
bpf_sk_release().
The ctx should point to the context of the program,
such as the skb or socket (depending on the hook in
use). This is used to determine the base network
namespace for the lookup.
tuple_size must be one of:
sizeof(tuple->ipv4)
Look for an IPv4 socket.
sizeof(tuple->ipv6)
Look for an IPv6 socket.
If the netns is a negative signed 32-bit integer,
then the socket lookup table in the netns
associated with the ctx will be used. For the TC
hooks, this is the netns of the device in the skb.
For socket hooks, this is the netns of the socket.
If netns is any other signed 32-bit value greater
than or equal to zero then it specifies the ID of
the netns relative to the netns associated with the
ctx. netns values beyond the range of 32-bit
integers are reserved for future use.
All values for flags are reserved for future usage,
and must be left at zero.
This helper is available only if the kernel was
compiled with CONFIG_NET configuration option.
Return Pointer to struct bpf_sock, or NULL in case of
failure. For sockets with reuseport option, the
struct bpf_sock result is from reuse->socks[] using
the hash of the tuple.
long bpf_sk_release(struct bpf_sock *sock)
Description
Release the reference held by sock. sock must be a
non-NULL pointer that was returned from
bpf_sk_lookup_xxx().
Return 0 on success, or a negative error in case of
failure.
long bpf_map_push_elem(struct bpf_map *map, const void *value,
u64 flags)
Description
Push an element value in map. flags is one of:
BPF_EXIST
If the queue/stack is full, the oldest
element is removed to make room for this.
Return 0 on success, or a negative error in case of
failure.
long bpf_map_pop_elem(struct bpf_map *map, void *value)
Description
Pop an element from map.
Return 0 on success, or a negative error in case of
failure.
long bpf_map_peek_elem(struct bpf_map *map, void *value)
Description
Get an element from map without removing it.
Return 0 on success, or a negative error in case of
failure.
long bpf_msg_push_data(struct sk_msg_buff *msg, u32 start, u32
len, u64 flags)
Description
For socket policies, insert len bytes into msg at
offset start.
If a program of type BPF_PROG_TYPE_SK_MSG is run on
a msg it may want to insert metadata or options
into the msg. This can later be read and used by
any of the lower layer BPF hooks.
This helper may fail if under memory pressure (a
malloc fails) in these cases BPF programs will get
an appropriate error and BPF programs will need to
handle them.
Return 0 on success, or a negative error in case of
failure.
long bpf_msg_pop_data(struct sk_msg_buff *msg, u32 start, u32
len, u64 flags)
Description
Will remove len bytes from a msg starting at byte
start. This may result in ENOMEM errors under
certain situations if an allocation and copy are
required due to a full ring buffer. However, the
helper will try to avoid doing the allocation if
possible. Other errors can occur if input
parameters are invalid either due to start byte not
being valid part of msg payload and/or pop value
being to large.
Return 0 on success, or a negative error in case of
failure.
long bpf_rc_pointer_rel(void *ctx, s32 rel_x, s32 rel_y)
Description
This helper is used in programs implementing IR
decoding, to report a successfully decoded pointer
movement.
The ctx should point to the lirc sample as passed
into the program.
This helper is only available is the kernel was
compiled with the CONFIG_BPF_LIRC_MODE2
configuration option set to "y".
Return 0
long bpf_spin_lock(struct bpf_spin_lock *lock)
Description
Acquire a spinlock represented by the pointer lock,
which is stored as part of a value of a map. Taking
the lock allows to safely update the rest of the
fields in that value. The spinlock can (and must)
later be released with a call to
bpf_spin_unlock(lock).
Spinlocks in BPF programs come with a number of
restrictions and constraints:
• bpf_spin_lock objects are only allowed inside
maps of types BPF_MAP_TYPE_HASH and
BPF_MAP_TYPE_ARRAY (this list could be extended
in the future).
• BTF description of the map is mandatory.
• The BPF program can take ONE lock at a time,
since taking two or more could cause dead locks.
• Only one struct bpf_spin_lock is allowed per map
element.
• When the lock is taken, calls (either BPF to BPF
or helpers) are not allowed.
• The BPF_LD_ABS and BPF_LD_IND instructions are
not allowed inside a spinlock-ed region.
• The BPF program MUST call bpf_spin_unlock() to
release the lock, on all execution paths, before
it returns.
• The BPF program can access struct bpf_spin_lock
only via the bpf_spin_lock() and
bpf_spin_unlock() helpers. Loading or storing
data into the struct bpf_spin_lock lock; field of
a map is not allowed.
• To use the bpf_spin_lock() helper, the BTF
description of the map value must be a struct and
have struct bpf_spin_lock anyname; field at the
top level. Nested lock inside another struct is
not allowed.
• The struct bpf_spin_lock lock field in a map
value must be aligned on a multiple of 4 bytes in
that value.
• Syscall with command BPF_MAP_LOOKUP_ELEM does not
copy the bpf_spin_lock field to user space.
• Syscall with command BPF_MAP_UPDATE_ELEM, or
update from a BPF program, do not update the
bpf_spin_lock field.
• bpf_spin_lock cannot be on the stack or inside a
networking packet (it can only be inside of a map
values).
• bpf_spin_lock is available to root only.
• Tracing programs and socket filter programs
cannot use bpf_spin_lock() due to insufficient
preemption checks (but this may change in the
future).
• bpf_spin_lock is not allowed in inner maps of
map-in-map.
Return 0
long bpf_spin_unlock(struct bpf_spin_lock *lock)
Description
Release the lock previously locked by a call to
bpf_spin_lock(lock).
Return 0
struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)
Description
This helper gets a struct bpf_sock pointer such
that all the fields in this bpf_sock can be
accessed.
Return A struct bpf_sock pointer on success, or NULL in
case of failure.
struct bpf_tcp_sock *bpf_tcp_sock(struct bpf_sock *sk)
Description
This helper gets a struct bpf_tcp_sock pointer from
a struct bpf_sock pointer.
Return A struct bpf_tcp_sock pointer on success, or NULL
in case of failure.
long bpf_skb_ecn_set_ce(struct sk_buff *skb)
Description
Set ECN (Explicit Congestion Notification) field of
IP header to CE (Congestion Encountered) if current
value is ECT (ECN Capable Transport). Otherwise, do
nothing. Works with IPv6 and IPv4.
Return 1 if the CE flag is set (either by the current
helper call or because it was already present), 0
if it is not set.
struct bpf_sock *bpf_get_listener_sock(struct bpf_sock *sk)
Description
Return a struct bpf_sock pointer in TCP_LISTEN
state. bpf_sk_release() is unnecessary and not
allowed.
Return A struct bpf_sock pointer on success, or NULL in
case of failure.
struct bpf_sock *bpf_skc_lookup_tcp(void *ctx, struct
bpf_sock_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
Description
Look for TCP socket matching tuple, optionally in a
child network namespace netns. The return value
must be checked, and if non-NULL, released via
bpf_sk_release().
This function is identical to bpf_sk_lookup_tcp(),
except that it also returns timewait or request
sockets. Use bpf_sk_fullsock() or bpf_tcp_sock() to
access the full structure.
This helper is available only if the kernel was
compiled with CONFIG_NET configuration option.
Return Pointer to struct bpf_sock, or NULL in case of
failure. For sockets with reuseport option, the
struct bpf_sock result is from reuse->socks[] using
the hash of the tuple.
long bpf_tcp_check_syncookie(struct bpf_sock *sk, void *iph, u32
iph_len, struct tcphdr *th, u32 th_len)
Description
Check whether iph and th contain a valid SYN cookie
ACK for the listening socket in sk.
iph points to the start of the IPv4 or IPv6 header,
while iph_len contains sizeof(struct iphdr) or
sizeof(struct ip6hdr).
th points to the start of the TCP header, while
th_len contains sizeof(struct tcphdr).
Return 0 if iph and th are a valid SYN cookie ACK, or a
negative error otherwise.
long bpf_sysctl_get_name(struct bpf_sysctl *ctx, char *buf,
size_t buf_len, u64 flags)
Description
Get name of sysctl in /proc/sys/ and copy it into
provided by program buffer buf of size buf_len.
The buffer is always NUL terminated, unless it's
zero-sized.
If flags is zero, full name (e.g.
"net/ipv4/tcp_mem") is copied. Use
BPF_F_SYSCTL_BASE_NAME flag to copy base name only
(e.g. "tcp_mem").
Return Number of character copied (not including the
trailing NUL).
-E2BIG if the buffer wasn't big enough (buf will
contain truncated name in this case).
long bpf_sysctl_get_current_value(struct bpf_sysctl *ctx, char
*buf, size_t buf_len)
Description
Get current value of sysctl as it is presented in
/proc/sys (incl. newline, etc), and copy it as a
string into provided by program buffer buf of size
buf_len.
The whole value is copied, no matter what file
position user space issued e.g. sys_read at.
The buffer is always NUL terminated, unless it's
zero-sized.
Return Number of character copied (not including the
trailing NUL).
-E2BIG if the buffer wasn't big enough (buf will
contain truncated name in this case).
-EINVAL if current value was unavailable, e.g.
because sysctl is uninitialized and read returns
-EIO for it.
long bpf_sysctl_get_new_value(struct bpf_sysctl *ctx, char *buf,
size_t buf_len)
Description
Get new value being written by user space to sysctl
(before the actual write happens) and copy it as a
string into provided by program buffer buf of size
buf_len.
User space may write new value at file position >
0.
The buffer is always NUL terminated, unless it's
zero-sized.
Return Number of character copied (not including the
trailing NUL).
-E2BIG if the buffer wasn't big enough (buf will
contain truncated name in this case).
-EINVAL if sysctl is being read.
long bpf_sysctl_set_new_value(struct bpf_sysctl *ctx, const char
*buf, size_t buf_len)
Description
Override new value being written by user space to
sysctl with value provided by program in buffer buf
of size buf_len.
buf should contain a string in same form as
provided by user space on sysctl write.
User space may write new value at file position >
0. To override the whole sysctl value file position
should be set to zero.
Return 0 on success.
-E2BIG if the buf_len is too big.
-EINVAL if sysctl is being read.
long bpf_strtol(const char *buf, size_t buf_len, u64 flags, long
*res)
Description
Convert the initial part of the string from buffer
buf of size buf_len to a long integer according to
the given base and save the result in res.
The string may begin with an arbitrary amount of
white space (as determined by isspace(3)) followed
by a single optional '-' sign.
Five least significant bits of flags encode base,
other bits are currently unused.
Base must be either 8, 10, 16, or 0 to detect it
automatically similar to user space strtol(3).
Return Number of characters consumed on success. Must be
positive but no more than buf_len.
-EINVAL if no valid digits were found or
unsupported base was provided.
-ERANGE if resulting value was out of range.
long bpf_strtoul(const char *buf, size_t buf_len, u64 flags,
unsigned long *res)
Description
Convert the initial part of the string from buffer
buf of size buf_len to an unsigned long integer
according to the given base and save the result in
res.
The string may begin with an arbitrary amount of
white space (as determined by isspace(3)).
Five least significant bits of flags encode base,
other bits are currently unused.
Base must be either 8, 10, 16, or 0 to detect it
automatically similar to user space strtoul(3).
Return Number of characters consumed on success. Must be
positive but no more than buf_len.
-EINVAL if no valid digits were found or
unsupported base was provided.
-ERANGE if resulting value was out of range.
void *bpf_sk_storage_get(struct bpf_map *map, struct bpf_sock
*sk, void *value, u64 flags)
Description
Get a bpf-local-storage from a sk.
Logically, it could be thought of getting the value
from a map with sk as the key. From this
perspective, the usage is not much different from
bpf_map_lookup_elem(map, &sk) except this helper
enforces the key must be a full socket and the map
must be a BPF_MAP_TYPE_SK_STORAGE also.
Underneath, the value is stored locally at sk
instead of the map. The map is used as the
bpf-local-storage "type". The bpf-local-storage
"type" (i.e. the map) is searched against all
bpf-local-storages residing at sk.
An optional flags (BPF_SK_STORAGE_GET_F_CREATE) can
be used such that a new bpf-local-storage will be
created if one does not exist. value can be used
together with BPF_SK_STORAGE_GET_F_CREATE to
specify the initial value of a bpf-local-storage.
If value is NULL, the new bpf-local-storage will be
zero initialized.
Return A bpf-local-storage pointer is returned on success.
NULL if not found or there was an error in adding a
new bpf-local-storage.
long bpf_sk_storage_delete(struct bpf_map *map, struct bpf_sock
*sk)
Description
Delete a bpf-local-storage from a sk.
Return 0 on success.
-ENOENT if the bpf-local-storage cannot be found.
long bpf_send_signal(u32 sig)
Description
Send signal sig to the process of the current task.
The signal may be delivered to any of this
process's threads.
Return 0 on success or successfully queued.
-EBUSY if work queue under nmi is full.
-EINVAL if sig is invalid.
-EPERM if no permission to send the sig.
-EAGAIN if bpf program can try again.
s64 bpf_tcp_gen_syncookie(struct bpf_sock *sk, void *iph, u32
iph_len, struct tcphdr *th, u32 th_len)
Description
Try to issue a SYN cookie for the packet with
corresponding IP/TCP headers, iph and th, on the
listening socket in sk.
iph points to the start of the IPv4 or IPv6 header,
while iph_len contains sizeof(struct iphdr) or
sizeof(struct ip6hdr).
th points to the start of the TCP header, while
th_len contains the length of the TCP header.
Return On success, lower 32 bits hold the generated SYN
cookie in followed by 16 bits which hold the MSS
value for that cookie, and the top 16 bits are
unused.
On failure, the returned value is one of the
following:
-EINVAL SYN cookie cannot be issued due to error
-ENOENT SYN cookie should not be issued (no SYN
flood)
-EOPNOTSUPP kernel configuration does not enable
SYN cookies
-EPROTONOSUPPORT IP packet version is not 4 or 6
long bpf_skb_output(void *ctx, struct bpf_map *map, u64 flags,
void *data, u64 size)
Description
Write raw data blob into a special BPF perf event
held by map of type BPF_MAP_TYPE_PERF_EVENT_ARRAY.
This perf event must have the following attributes:
PERF_SAMPLE_RAW as sample_type, PERF_TYPE_SOFTWARE
as type, and PERF_COUNT_SW_BPF_OUTPUT as config.
The flags are used to indicate the index in map for
which the value must be put, masked with
BPF_F_INDEX_MASK. Alternatively, flags can be set
to BPF_F_CURRENT_CPU to indicate that the index of
the current CPU core should be used.
The value to write, of size, is passed through eBPF
stack and pointed by data.
ctx is a pointer to in-kernel struct sk_buff.
This helper is similar to bpf_perf_event_output()
but restricted to raw_tracepoint bpf programs.
Return 0 on success, or a negative error in case of
failure.
long bpf_probe_read_user(void *dst, u32 size, const void
*unsafe_ptr)
Description
Safely attempt to read size bytes from user space
address unsafe_ptr and store the data in dst.
Return 0 on success, or a negative error in case of
failure.
long bpf_probe_read_kernel(void *dst, u32 size, const void
*unsafe_ptr)
Description
Safely attempt to read size bytes from kernel space
address unsafe_ptr and store the data in dst.
Return 0 on success, or a negative error in case of
failure.
long bpf_probe_read_user_str(void *dst, u32 size, const void
*unsafe_ptr)
Description
Copy a NUL terminated string from an unsafe user
address unsafe_ptr to dst. The size should include
the terminating NUL byte. In case the string length
is smaller than size, the target is not padded with
further NUL bytes. If the string length is larger
than size, just size-1 bytes are copied and the
last byte is set to NUL.
On success, the length of the copied string is
returned. This makes this helper useful in tracing
programs for reading strings, and more importantly
to get its length at runtime. See the following
snippet:
SEC("kprobe/sys_open")
void bpf_sys_open(struct pt_regs *ctx)
{
char buf[PATHLEN]; // PATHLEN is defined to 256
int res = bpf_probe_read_user_str(buf, sizeof(buf),
ctx->di);
// Consume buf, for example push it to
// user space via bpf_perf_event_output(); we
// can use res (the string length) as event
// size, after checking its boundaries.
}
In comparison, using bpf_probe_read_user() helper
here instead to read the string would require to
estimate the length at compile time, and would
often result in copying more memory than necessary.
Another useful use case is when parsing individual
process arguments or individual environment
variables navigating current->mm->arg_start and
current->mm->env_start: using this helper and the
return value, one can quickly iterate at the right
offset of the memory area.
Return On success, the strictly positive length of the
string, including the trailing NUL character. On
error, a negative value.
long bpf_probe_read_kernel_str(void *dst, u32 size, const void
*unsafe_ptr)
Description
Copy a NUL terminated string from an unsafe kernel
address unsafe_ptr to dst. Same semantics as with
bpf_probe_read_user_str() apply.
Return On success, the strictly positive length of the
string, including the trailing NUL character. On
error, a negative value.
long bpf_tcp_send_ack(void *tp, u32 rcv_nxt)
Description
Send out a tcp-ack. tp is the in-kernel struct
tcp_sock. rcv_nxt is the ack_seq to be sent out.
Return 0 on success, or a negative error in case of
failure.
long bpf_send_signal_thread(u32 sig)
Description
Send signal sig to the thread corresponding to the
current task.
Return 0 on success or successfully queued.
-EBUSY if work queue under nmi is full.
-EINVAL if sig is invalid.
-EPERM if no permission to send the sig.
-EAGAIN if bpf program can try again.
u64 bpf_jiffies64(void)
Description
Obtain the 64bit jiffies
Return The 64 bit jiffies
long bpf_read_branch_records(struct bpf_perf_event_data *ctx,
void *buf, u32 size, u64 flags)
Description
For an eBPF program attached to a perf event,
retrieve the branch records (struct
perf_branch_entry) associated to ctx and store it
in the buffer pointed by buf up to size size bytes.
Return On success, number of bytes written to buf. On
error, a negative value.
The flags can be set to
BPF_F_GET_BRANCH_RECORDS_SIZE to instead return the
number of bytes required to store all the branch
entries. If this flag is set, buf may be NULL.
-EINVAL if arguments invalid or size not a multiple
of sizeof(struct perf_branch_entry).
-ENOENT if architecture does not support branch
records.
long bpf_get_ns_current_pid_tgid(u64 dev, u64 ino, struct
bpf_pidns_info *nsdata, u32 size)
Description
Returns 0 on success, values for pid and tgid as
seen from the current namespace will be returned in
nsdata.
Return 0 on success, or one of the following in case of
failure:
-EINVAL if dev and inum supplied don't match dev_t
and inode number with nsfs of current task, or if
dev conversion to dev_t lost high bits.
-ENOENT if pidns does not exists for the current
task.
long bpf_xdp_output(void *ctx, struct bpf_map *map, u64 flags,
void *data, u64 size)
Description
Write raw data blob into a special BPF perf event
held by map of type BPF_MAP_TYPE_PERF_EVENT_ARRAY.
This perf event must have the following attributes:
PERF_SAMPLE_RAW as sample_type, PERF_TYPE_SOFTWARE
as type, and PERF_COUNT_SW_BPF_OUTPUT as config.
The flags are used to indicate the index in map for
which the value must be put, masked with
BPF_F_INDEX_MASK. Alternatively, flags can be set
to BPF_F_CURRENT_CPU to indicate that the index of
the current CPU core should be used.
The value to write, of size, is passed through eBPF
stack and pointed by data.
ctx is a pointer to in-kernel struct xdp_buff.
This helper is similar to bpf_perf_eventoutput()
but restricted to raw_tracepoint bpf programs.
Return 0 on success, or a negative error in case of
failure.
u64 bpf_get_netns_cookie(void *ctx)
Description
Retrieve the cookie (generated by the kernel) of
the network namespace the input ctx is associated
with. The network namespace cookie remains stable
for its lifetime and provides a global identifier
that can be assumed unique. If ctx is NULL, then
the helper returns the cookie for the initial
network namespace. The cookie itself is very
similar to that of bpf_get_socket_cookie() helper,
but for network namespaces instead of sockets.
Return A 8-byte long opaque number.
u64 bpf_get_current_ancestor_cgroup_id(int ancestor_level)
Description
Return id of cgroup v2 that is ancestor of the
cgroup associated with the current task at the
ancestor_level. The root cgroup is at
ancestor_level zero and each step down the
hierarchy increments the level. If ancestor_level
== level of cgroup associated with the current
task, then return value will be the same as that of
bpf_get_current_cgroup_id().
The helper is useful to implement policies based on
cgroups that are upper in hierarchy than immediate
cgroup associated with the current task.
The format of returned id and helper limitations
are same as in bpf_get_current_cgroup_id().
Return The id is returned or 0 in case the id could not be
retrieved.
long bpf_sk_assign(struct sk_buff *skb, struct bpf_sock *sk, u64
flags)
Description
Helper is overloaded depending on BPF program type.
This description applies to BPF_PROG_TYPE_SCHED_CLS
and BPF_PROG_TYPE_SCHED_ACT programs.
Assign the sk to the skb. When combined with
appropriate routing configuration to receive the
packet towards the socket, will cause skb to be
delivered to the specified socket. Subsequent
redirection of skb via bpf_redirect(),
bpf_clone_redirect() or other methods outside of
BPF may interfere with successful delivery to the
socket.
This operation is only valid from TC ingress path.
The flags argument must be zero.
Return 0 on success, or a negative error in case of
failure:
-EINVAL if specified flags are not supported.
-ENOENT if the socket is unavailable for
assignment.
-ENETUNREACH if the socket is unreachable (wrong
netns).
-EOPNOTSUPP if the operation is not supported, for
example a call from outside of TC ingress.
-ESOCKTNOSUPPORT if the socket type is not
supported (reuseport).
long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock
*sk, u64 flags)
Description
Helper is overloaded depending on BPF program type.
This description applies to BPF_PROG_TYPE_SK_LOOKUP
programs.
Select the sk as a result of a socket lookup.
For the operation to succeed passed socket must be
compatible with the packet description provided by
the ctx object.
L4 protocol (IPPROTO_TCP or IPPROTO_UDP) must be an
exact match. While IP family (AF_INET or AF_INET6)
must be compatible, that is IPv6 sockets that are
not v6-only can be selected for IPv4 packets.
Only TCP listeners and UDP unconnected sockets can
be selected. sk can also be NULL to reset any
previous selection.
flags argument can combination of following values:
• BPF_SK_LOOKUP_F_REPLACE to override the previous
socket selection, potentially done by a BPF
program that ran before us.
• BPF_SK_LOOKUP_F_NO_REUSEPORT to skip
load-balancing within reuseport group for the
socket being selected.
On success ctx->sk will point to the selected
socket.
Return 0 on success, or a negative errno in case of
failure.
• -EAFNOSUPPORT if socket family (sk->family) is
not compatible with packet family (ctx->family).
• -EEXIST if socket has been already selected,
potentially by another program, and
BPF_SK_LOOKUP_F_REPLACE flag was not specified.
• -EINVAL if unsupported flags were specified.
• -EPROTOTYPE if socket L4 protocol (sk->protocol)
doesn't match packet protocol (ctx->protocol).
• -ESOCKTNOSUPPORT if socket is not in allowed
state (TCP listening or UDP unconnected).
u64 bpf_ktime_get_boot_ns(void)
Description
Return the time elapsed since system boot, in
nanoseconds. Does include the time the system was
suspended. See: clock_gettime(CLOCK_BOOTTIME)
Return Current ktime.
long bpf_seq_printf(struct seq_file *m, const char *fmt, u32
fmt_size, const void *data, u32 data_len)
Description
bpf_seq_printf() uses seq_file seq_printf() to
print out the format string. The m represents the
seq_file. The fmt and fmt_size are for the format
string itself. The data and data_len are format
string arguments. The data are a u64 array and
corresponding format string values are stored in
the array. For strings and pointers where pointees
are accessed, only the pointer values are stored in
the data array. The data_len is the size of data
in bytes.
Formats %s, %p{i,I}{4,6} requires to read kernel
memory. Reading kernel memory may fail due to
either invalid address or valid address but
requiring a major memory fault. If reading kernel
memory fails, the string for %s will be an empty
string, and the ip address for %p{i,I}{4,6} will be
0. Not returning error to bpf program is consistent
with what bpf_trace_printk() does for now.
Return 0 on success, or a negative error in case of
failure:
-EBUSY if per-CPU memory copy buffer is busy, can
try again by returning 1 from bpf program.
-EINVAL if arguments are invalid, or if fmt is
invalid/unsupported.
-E2BIG if fmt contains too many format specifiers.
-EOVERFLOW if an overflow happened: The same object
will be tried again.
long bpf_seq_write(struct seq_file *m, const void *data, u32 len)
Description
bpf_seq_write() uses seq_file seq_write() to write
the data. The m represents the seq_file. The data
and len represent the data to write in bytes.
Return 0 on success, or a negative error in case of
failure:
-EOVERFLOW if an overflow happened: The same object
will be tried again.
u64 bpf_sk_cgroup_id(struct bpf_sock *sk)
Description
Return the cgroup v2 id of the socket sk.
sk must be a non-NULL pointer to a full socket,
e.g. one returned from bpf_sk_lookup_xxx(),
bpf_sk_fullsock(), etc. The format of returned id
is same as in bpf_skb_cgroup_id().
This helper is available only if the kernel was
compiled with the CONFIG_SOCK_CGROUP_DATA
configuration option.
Return The id is returned or 0 in case the id could not be
retrieved.
u64 bpf_sk_ancestor_cgroup_id(struct bpf_sock *sk, int
ancestor_level)
Description
Return id of cgroup v2 that is ancestor of cgroup
associated with the sk at the ancestor_level. The
root cgroup is at ancestor_level zero and each step
down the hierarchy increments the level. If
ancestor_level == level of cgroup associated with
sk, then return value will be same as that of
bpf_sk_cgroup_id().
The helper is useful to implement policies based on
cgroups that are upper in hierarchy than immediate
cgroup associated with sk.
The format of returned id and helper limitations
are same as in bpf_sk_cgroup_id().
Return The id is returned or 0 in case the id could not be
retrieved.
long bpf_ringbuf_output(void *ringbuf, void *data, u64 size, u64
flags)
Description
Copy size bytes from data into a ring buffer
ringbuf. If BPF_RB_NO_WAKEUP is specified in
flags, no notification of new data availability is
sent. If BPF_RB_FORCE_WAKEUP is specified in
flags, notification of new data availability is
sent unconditionally.
Return 0 on success, or a negative error in case of
failure.
void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
Description
Reserve size bytes of payload in a ring buffer
ringbuf.
Return Valid pointer with size bytes of memory available;
NULL, otherwise.
void bpf_ringbuf_submit(void *data, u64 flags)
Description
Submit reserved ring buffer sample, pointed to by
data. If BPF_RB_NO_WAKEUP is specified in flags,
no notification of new data availability is sent.
If BPF_RB_FORCE_WAKEUP is specified in flags,
notification of new data availability is sent
unconditionally.
Return Nothing. Always succeeds.
void bpf_ringbuf_discard(void *data, u64 flags)
Description
Discard reserved ring buffer sample, pointed to by
data. If BPF_RB_NO_WAKEUP is specified in flags,
no notification of new data availability is sent.
If BPF_RB_FORCE_WAKEUP is specified in flags,
notification of new data availability is sent
unconditionally.
Return Nothing. Always succeeds.
u64 bpf_ringbuf_query(void *ringbuf, u64 flags)
Description
Query various characteristics of provided ring
buffer. What exactly is queries is determined by
flags:
• BPF_RB_AVAIL_DATA: Amount of data not yet
consumed.
• BPF_RB_RING_SIZE: The size of ring buffer.
• BPF_RB_CONS_POS: Consumer position (can wrap
around).
• BPF_RB_PROD_POS: Producer(s) position (can wrap
around).
Data returned is just a momentary snapshot of
actual values and could be inaccurate, so this
facility should be used to power heuristics and for
reporting, not to make 100% correct calculation.
Return Requested value, or 0, if flags are not recognized.
long bpf_csum_level(struct sk_buff *skb, u64 level)
Description
Change the skbs checksum level by one layer up or
down, or reset it entirely to none in order to have
the stack perform checksum validation. The level is
applicable to the following protocols: TCP, UDP,
GRE, SCTP, FCOE. For example, a decap of | ETH | IP
| UDP | GUE | IP | TCP | into | ETH | IP | TCP |
through bpf_skb_adjust_room() helper with passing
in BPF_F_ADJ_ROOM_NO_CSUM_RESET flag would require
one call to bpf_csum_level() with
BPF_CSUM_LEVEL_DEC since the UDP header is removed.
Similarly, an encap of the latter into the former
could be accompanied by a helper call to
bpf_csum_level() with BPF_CSUM_LEVEL_INC if the skb
is still intended to be processed in higher layers
of the stack instead of just egressing at tc.
There are three supported level settings at this
time:
• BPF_CSUM_LEVEL_INC: Increases skb->csum_level for
skbs with CHECKSUM_UNNECESSARY.
• BPF_CSUM_LEVEL_DEC: Decreases skb->csum_level for
skbs with CHECKSUM_UNNECESSARY.
• BPF_CSUM_LEVEL_RESET: Resets skb->csum_level to 0
and sets CHECKSUM_NONE to force checksum
validation by the stack.
• BPF_CSUM_LEVEL_QUERY: No-op, returns the current
skb->csum_level.
Return 0 on success, or a negative error in case of
failure. In the case of BPF_CSUM_LEVEL_QUERY, the
current skb->csum_level is returned or the error
code -EACCES in case the skb is not subject to
CHECKSUM_UNNECESSARY.
struct tcp6_sock *bpf_skc_to_tcp6_sock(void *sk)
Description
Dynamically cast a sk pointer to a tcp6_sock
pointer.
Return sk if casting is valid, or NULL otherwise.
struct tcp_sock *bpf_skc_to_tcp_sock(void *sk)
Description
Dynamically cast a sk pointer to a tcp_sock
pointer.
Return sk if casting is valid, or NULL otherwise.
struct tcp_timewait_sock *bpf_skc_to_tcp_timewait_sock(void *sk)
Description
Dynamically cast a sk pointer to a
tcp_timewait_sock pointer.
Return sk if casting is valid, or NULL otherwise.
struct tcp_request_sock *bpf_skc_to_tcp_request_sock(void *sk)
Description
Dynamically cast a sk pointer to a tcp_request_sock
pointer.
Return sk if casting is valid, or NULL otherwise.
struct udp6_sock *bpf_skc_to_udp6_sock(void *sk)
Description
Dynamically cast a sk pointer to a udp6_sock
pointer.
Return sk if casting is valid, or NULL otherwise.
long bpf_get_task_stack(struct task_struct *task, void *buf, u32
size, u64 flags)
Description
Return a user or a kernel stack in bpf program
provided buffer. To achieve this, the helper needs
task, which is a valid pointer to struct
task_struct. To store the stacktrace, the bpf
program provides buf with a nonnegative size.
The last argument, flags, holds the number of stack
frames to skip (from 0 to 255), masked with
BPF_F_SKIP_FIELD_MASK. The next bits can be used to
set the following flags:
BPF_F_USER_STACK
Collect a user space stack instead of a
kernel stack.
BPF_F_USER_BUILD_ID
Collect buildid+offset instead of ips for
user stack, only valid if BPF_F_USER_STACK
is also specified.
bpf_get_task_stack() can collect up to
PERF_MAX_STACK_DEPTH both kernel and user frames,
subject to sufficient large buffer size. Note that
this limit can be controlled with the sysctl
program, and that it should be manually increased
in order to profile long user stacks (such as
stacks for Java programs). To do so, use:
# sysctl kernel.perf_event_max_stack=<new value>
Return A non-negative value equal to or less than size on
success, or a negative error in case of failure.
