Adding upstream version 6.05.01.upstream/6.05.01

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.\" Man page generated from reStructuredText.
+.
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+.de1 INDENT
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+.\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
+.in \\n[rst2man-indent\\n[rst2man-indent-level]]u
+..
+.TH "BPF-HELPERS" 7 "2023-04-11" "Linux v6.2"
+.SH NAME
+BPF-HELPERS \- list of eBPF helper functions
+.\" Copyright (C) All BPF authors and contributors from 2014 to present.
+.
+.\" See git log include/uapi/linux/bpf.h in kernel tree for details.
+.
+.\"
+.
+.\" SPDX-License-Identifier:  Linux-man-pages-copyleft
+.
+.\"
+.
+.\" Please do not edit this file. It was generated from the documentation
+.
+.\" located in file include/uapi/linux/bpf.h of the Linux kernel sources
+.
+.\" (helpers description), and from scripts/bpf_doc.py in the same
+.
+.\" repository (header and footer).
+.
+.SH DESCRIPTION
+.sp
+The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
+written in a pseudo\-assembly language, then attached to one of the several
+kernel hooks and run in reaction of specific events. This framework differs
+from the older, \(dqclassic\(dq BPF (or \(dqcBPF\(dq) in several aspects, one of them being
+the ability to call special functions (or \(dqhelpers\(dq) from within a program.
+These functions are restricted to a white\-list of helpers defined in the
+kernel.
+.sp
+These helpers are used by eBPF programs to interact with the system, or with
+the context in which they work. For instance, they can be used to print
+debugging messages, to get the time since the system was booted, to interact
+with eBPF maps, or to manipulate network packets. Since there are several eBPF
+program types, and that they do not run in the same context, each program type
+can only call a subset of those helpers.
+.sp
+Due to eBPF conventions, a helper can not have more than five arguments.
+.sp
+Internally, eBPF programs call directly into the compiled helper functions
+without requiring any foreign\-function interface. As a result, calling helpers
+introduces no overhead, thus offering excellent performance.
+.sp
+This document is an attempt to list and document the helpers available to eBPF
+developers. They are sorted by chronological order (the oldest helpers in the
+kernel at the top).
+.SH HELPERS
+.INDENT 0.0
+.TP
+.B \fBvoid *bpf_map_lookup_elem(struct bpf_map *\fP\fImap\fP\fB, const void *\fP\fIkey\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Perform a lookup in \fImap\fP for an entry associated to \fIkey\fP\&.
+.TP
+.B Return
+Map value associated to \fIkey\fP, or \fBNULL\fP if no entry was
+found.
+.UNINDENT
+.TP
+.B \fBlong bpf_map_update_elem(struct bpf_map *\fP\fImap\fP\fB, const void *\fP\fIkey\fP\fB, const void *\fP\fIvalue\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Add or update the value of the entry associated to \fIkey\fP in
+\fImap\fP with \fIvalue\fP\&. \fIflags\fP is one of:
+.INDENT 7.0
+.TP
+.B \fBBPF_NOEXIST\fP
+The entry for \fIkey\fP must not exist in the map.
+.TP
+.B \fBBPF_EXIST\fP
+The entry for \fIkey\fP must already exist in the map.
+.TP
+.B \fBBPF_ANY\fP
+No condition on the existence of the entry for \fIkey\fP\&.
+.UNINDENT
+.sp
+Flag value \fBBPF_NOEXIST\fP cannot be used for maps of types
+\fBBPF_MAP_TYPE_ARRAY\fP or \fBBPF_MAP_TYPE_PERCPU_ARRAY\fP  (all
+elements always exist), the helper would return an error.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_map_delete_elem(struct bpf_map *\fP\fImap\fP\fB, const void *\fP\fIkey\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Delete entry with \fIkey\fP from \fImap\fP\&.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_probe_read(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIunsafe_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For tracing programs, safely attempt to read \fIsize\fP bytes from
+kernel space address \fIunsafe_ptr\fP and store the data in \fIdst\fP\&.
+.sp
+Generally, use \fBbpf_probe_read_user\fP() or
+\fBbpf_probe_read_kernel\fP() instead.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu64 bpf_ktime_get_ns(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return the time elapsed since system boot, in nanoseconds.
+Does not include time the system was suspended.
+See: \fBclock_gettime\fP(\fBCLOCK_MONOTONIC\fP)
+.TP
+.B Return
+Current \fIktime\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_trace_printk(const char *\fP\fIfmt\fP\fB, u32\fP \fIfmt_size\fP\fB, ...)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is a \(dqprintk()\-like\(dq facility for debugging. It
+prints a message defined by format \fIfmt\fP (of size \fIfmt_size\fP)
+to file \fI/sys/kernel/debug/tracing/trace\fP from DebugFS, if
+available. It can take up to three additional \fBu64\fP
+arguments (as an eBPF helpers, the total number of arguments is
+limited to five).
+.sp
+Each time the helper is called, it appends a line to the trace.
+Lines are discarded while \fI/sys/kernel/debug/tracing/trace\fP is
+open, use \fI/sys/kernel/debug/tracing/trace_pipe\fP to avoid this.
+The format of the trace is customizable, and the exact output
+one will get depends on the options set in
+\fI/sys/kernel/debug/tracing/trace_options\fP (see also the
+\fIREADME\fP file under the same directory). However, it usually
+defaults to something like:
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+telnet\-470   [001] .N.. 419421.045894: 0x00000001: <fmt>
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.sp
+In the above:
+.INDENT 7.0
+.INDENT 3.5
+.INDENT 0.0
+.IP \(bu 2
+\fBtelnet\fP is the name of the current task.
+.IP \(bu 2
+\fB470\fP is the PID of the current task.
+.IP \(bu 2
+\fB001\fP is the CPU number on which the task is
+running.
+.IP \(bu 2
+In \fB\&.N..\fP, each character refers to a set of
+options (whether irqs are enabled, scheduling
+options, whether hard/softirqs are running, level of
+preempt_disabled respectively). \fBN\fP means that
+\fBTIF_NEED_RESCHED\fP and \fBPREEMPT_NEED_RESCHED\fP
+are set.
+.IP \(bu 2
+\fB419421.045894\fP is a timestamp.
+.IP \(bu 2
+\fB0x00000001\fP is a fake value used by BPF for the
+instruction pointer register.
+.IP \(bu 2
+\fB<fmt>\fP is the message formatted with \fIfmt\fP\&.
+.UNINDENT
+.UNINDENT
+.UNINDENT
+.sp
+The conversion specifiers supported by \fIfmt\fP are similar, but
+more limited than for printk(). They are \fB%d\fP, \fB%i\fP,
+\fB%u\fP, \fB%x\fP, \fB%ld\fP, \fB%li\fP, \fB%lu\fP, \fB%lx\fP, \fB%lld\fP,
+\fB%lli\fP, \fB%llu\fP, \fB%llx\fP, \fB%p\fP, \fB%s\fP\&. No modifier (size
+of field, padding with zeroes, etc.) is available, and the
+helper will return \fB\-EINVAL\fP (but print nothing) if it
+encounters an unknown specifier.
+.sp
+Also, note that \fBbpf_trace_printk\fP() 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 \(dqfor production use\(dq
+the first time this helper is used (or more precisely, when
+\fBtrace_printk\fP() buffers are allocated). For passing values
+to user space, perf events should be preferred.
+.TP
+.B Return
+The number of bytes written to the buffer, or a negative error
+in case of failure.
+.UNINDENT
+.TP
+.B \fBu32 bpf_get_prandom_u32(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get a pseudo\-random number.
+.sp
+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.
+.TP
+.B Return
+A random 32\-bit unsigned value.
+.UNINDENT
+.TP
+.B \fBu32 bpf_get_smp_processor_id(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the SMP (symmetric multiprocessing) processor id. Note that
+all programs run with migration disabled, which means that the
+SMP processor id is stable during all the execution of the
+program.
+.TP
+.B Return
+The SMP id of the processor running the program.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_store_bytes(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIoffset\fP\fB, const void *\fP\fIfrom\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Store \fIlen\fP bytes from address \fIfrom\fP into the packet
+associated to \fIskb\fP, at \fIoffset\fP\&. \fIflags\fP are a combination of
+\fBBPF_F_RECOMPUTE_CSUM\fP (automatically recompute the
+checksum for the packet after storing the bytes) and
+\fBBPF_F_INVALIDATE_HASH\fP (set \fIskb\fP\fB\->hash\fP, \fIskb\fP\fB\->swhash\fP and \fIskb\fP\fB\->l4hash\fP to 0).
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_l3_csum_replace(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIoffset\fP\fB, u64\fP \fIfrom\fP\fB, u64\fP \fIto\fP\fB, u64\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Recompute the layer 3 (e.g. IP) checksum for the packet
+associated to \fIskb\fP\&. Computation is incremental, so the helper
+must know the former value of the header field that was
+modified (\fIfrom\fP), the new value of this field (\fIto\fP), and the
+number of bytes (2 or 4) for this field, stored in \fIsize\fP\&.
+Alternatively, it is possible to store the difference between
+the previous and the new values of the header field in \fIto\fP, by
+setting \fIfrom\fP and \fIsize\fP to 0. For both methods, \fIoffset\fP
+indicates the location of the IP checksum within the packet.
+.sp
+This helper works in combination with \fBbpf_csum_diff\fP(),
+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.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_l4_csum_replace(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIoffset\fP\fB, u64\fP \fIfrom\fP\fB, u64\fP \fIto\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Recompute the layer 4 (e.g. TCP, UDP or ICMP) checksum for the
+packet associated to \fIskb\fP\&. Computation is incremental, so the
+helper must know the former value of the header field that was
+modified (\fIfrom\fP), the new value of this field (\fIto\fP), and the
+number of bytes (2 or 4) for this field, stored on the lowest
+four bits of \fIflags\fP\&. Alternatively, it is possible to store
+the difference between the previous and the new values of the
+header field in \fIto\fP, by setting \fIfrom\fP and the four lowest
+bits of \fIflags\fP to 0. For both methods, \fIoffset\fP indicates the
+location of the IP checksum within the packet. In addition to
+the size of the field, \fIflags\fP can be added (bitwise OR) actual
+flags. With \fBBPF_F_MARK_MANGLED_0\fP, a null checksum is left
+untouched (unless \fBBPF_F_MARK_ENFORCE\fP is added as well), and
+for updates resulting in a null checksum the value is set to
+\fBCSUM_MANGLED_0\fP instead. Flag \fBBPF_F_PSEUDO_HDR\fP indicates
+the checksum is to be computed against a pseudo\-header.
+.sp
+This helper works in combination with \fBbpf_csum_diff\fP(),
+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.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_tail_call(void *\fP\fIctx\fP\fB, struct bpf_map *\fP\fIprog_array_map\fP\fB, u32\fP \fIindex\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This special helper is used to trigger a \(dqtail call\(dq, 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.
+.sp
+Upon call of this helper, the program attempts to jump into a
+program referenced at index \fIindex\fP in \fIprog_array_map\fP, a
+special map of type \fBBPF_MAP_TYPE_PROG_ARRAY\fP, and passes
+\fIctx\fP, a pointer to the context.
+.sp
+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. \fIindex\fP
+is superior to the number of entries in \fIprog_array_map\fP), 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 \fBMAX_TAIL_CALL_CNT\fP (not accessible to user space),
+which is currently set to 33.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_clone_redirect(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIifindex\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Clone and redirect the packet associated to \fIskb\fP to another
+net device of index \fIifindex\fP\&. Both ingress and egress
+interfaces can be used for redirection. The \fBBPF_F_INGRESS\fP
+value in \fIflags\fP 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.
+.sp
+In comparison with \fBbpf_redirect\fP() helper,
+\fBbpf_clone_redirect\fP() has the associated cost of
+duplicating the packet buffer, but this can be executed out of
+the eBPF program. Conversely, \fBbpf_redirect\fP() is more
+efficient, but it is handled through an action code where the
+redirection happens only after the eBPF program has returned.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_current_pid_tgid(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the current pid and tgid.
+.TP
+.B Return
+A 64\-bit integer containing the current tgid and pid, and
+created as such:
+\fIcurrent_task\fP\fB\->tgid << 32 |\fP
+\fIcurrent_task\fP\fB\->pid\fP\&.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_current_uid_gid(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the current uid and gid.
+.TP
+.B Return
+A 64\-bit integer containing the current GID and UID, and
+created as such: \fIcurrent_gid\fP \fB<< 32 |\fP \fIcurrent_uid\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_current_comm(void *\fP\fIbuf\fP\fB, u32\fP \fIsize_of_buf\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Copy the \fBcomm\fP attribute of the current task into \fIbuf\fP of
+\fIsize_of_buf\fP\&. The \fBcomm\fP attribute contains the name of
+the executable (excluding the path) for the current task. The
+\fIsize_of_buf\fP must be strictly positive. On success, the
+helper makes sure that the \fIbuf\fP is NUL\-terminated. On failure,
+it is filled with zeroes.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu32 bpf_get_cgroup_classid(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Retrieve the classid for the current task, i.e. for the net_cls
+cgroup to which \fIskb\fP belongs.
+.sp
+This helper can be used on TC egress path, but not on ingress.
+.sp
+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
+\fIDocumentation/admin\-guide/cgroup\-v1/net_cls.rst\fP\&.
+.sp
+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).
+.sp
+This helper is only available is the kernel was compiled with
+the \fBCONFIG_CGROUP_NET_CLASSID\fP configuration option set to
+\(dq\fBy\fP\(dq or to \(dq\fBm\fP\(dq.
+.TP
+.B Return
+The classid, or 0 for the default unconfigured classid.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_vlan_push(struct sk_buff *\fP\fIskb\fP\fB, __be16\fP \fIvlan_proto\fP\fB, u16\fP \fIvlan_tci\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Push a \fIvlan_tci\fP (VLAN tag control information) of protocol
+\fIvlan_proto\fP to the packet associated to \fIskb\fP, then update
+the checksum. Note that if \fIvlan_proto\fP is different from
+\fBETH_P_8021Q\fP and \fBETH_P_8021AD\fP, it is considered to
+be \fBETH_P_8021Q\fP\&.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_vlan_pop(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Pop a VLAN header from the packet associated to \fIskb\fP\&.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_get_tunnel_key(struct sk_buff *\fP\fIskb\fP\fB, struct bpf_tunnel_key *\fP\fIkey\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get tunnel metadata. This helper takes a pointer \fIkey\fP to an
+empty \fBstruct bpf_tunnel_key\fP of \fBsize\fP, that will be
+filled with tunnel metadata for the packet associated to \fIskb\fP\&.
+The \fIflags\fP can be set to \fBBPF_F_TUNINFO_IPV6\fP, which
+indicates that the tunnel is based on IPv6 protocol instead of
+IPv4.
+.sp
+The \fBstruct bpf_tunnel_key\fP 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,
+\(dqsummarized\(dq in this struct. In particular, it holds the IP
+address of the remote end (IPv4 or IPv6, depending on the case)
+in \fIkey\fP\fB\->remote_ipv4\fP or \fIkey\fP\fB\->remote_ipv6\fP\&. Also,
+this struct exposes the \fIkey\fP\fB\->tunnel_id\fP, which is
+generally mapped to a VNI (Virtual Network Identifier), making
+it programmable together with the \fBbpf_skb_set_tunnel_key\fP() helper.
+.sp
+Let\(aqs 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:
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+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
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.sp
+This interface can also be used with all encapsulation devices
+that can operate in \(dqcollect metadata\(dq mode: instead of having
+one network device per specific configuration, the \(dqcollect
+metadata\(dq mode only requires a single device where the
+configuration can be extracted from this helper.
+.sp
+This can be used together with various tunnels such as VXLan,
+Geneve, GRE or IP in IP (IPIP).
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_set_tunnel_key(struct sk_buff *\fP\fIskb\fP\fB, struct bpf_tunnel_key *\fP\fIkey\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Populate tunnel metadata for packet associated to \fIskb.\fP The
+tunnel metadata is set to the contents of \fIkey\fP, of \fIsize\fP\&. The
+\fIflags\fP can be set to a combination of the following values:
+.INDENT 7.0
+.TP
+.B \fBBPF_F_TUNINFO_IPV6\fP
+Indicate that the tunnel is based on IPv6 protocol
+instead of IPv4.
+.TP
+.B \fBBPF_F_ZERO_CSUM_TX\fP
+For IPv4 packets, add a flag to tunnel metadata
+indicating that checksum computation should be skipped
+and checksum set to zeroes.
+.TP
+.B \fBBPF_F_DONT_FRAGMENT\fP
+Add a flag to tunnel metadata indicating that the
+packet should not be fragmented.
+.TP
+.B \fBBPF_F_SEQ_NUMBER\fP
+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.
+.UNINDENT
+.sp
+Here is a typical usage on the transmit path:
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+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);
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.sp
+See also the description of the \fBbpf_skb_get_tunnel_key\fP()
+helper for additional information.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu64 bpf_perf_event_read(struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Read the value of a perf event counter. This helper relies on a
+\fImap\fP of type \fBBPF_MAP_TYPE_PERF_EVENT_ARRAY\fP\&. The nature of
+the perf event counter is selected when \fImap\fP is updated with
+perf event file descriptors. The \fImap\fP 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
+\fIflags\fP, that contains the index of the CPU to look up, masked
+with \fBBPF_F_INDEX_MASK\fP\&. Alternatively, \fIflags\fP can be set to
+\fBBPF_F_CURRENT_CPU\fP to indicate that the value for the
+current CPU should be retrieved.
+.sp
+Note that before Linux 4.13, only hardware perf event can be
+retrieved.
+.sp
+Also, be aware that the newer helper
+\fBbpf_perf_event_read_value\fP() is recommended over
+\fBbpf_perf_event_read\fP() 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 \fBbpf_perf_event_read_value\fP(), which at the same
+time provides more features over the \fBbpf_perf_event_read\fP() interface. Please refer to the description of
+\fBbpf_perf_event_read_value\fP() for details.
+.TP
+.B Return
+The value of the perf event counter read from the map, or a
+negative error code in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_redirect(u32\fP \fIifindex\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Redirect the packet to another net device of index \fIifindex\fP\&.
+This helper is somewhat similar to \fBbpf_clone_redirect\fP(), except that the packet is not cloned, which provides
+increased performance.
+.sp
+Except for XDP, both ingress and egress interfaces can be used
+for redirection. The \fBBPF_F_INGRESS\fP value in \fIflags\fP 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.
+.sp
+The same effect can also be attained with the more generic
+\fBbpf_redirect_map\fP(), which uses a BPF map to store the
+redirect target instead of providing it directly to the helper.
+.TP
+.B Return
+For XDP, the helper returns \fBXDP_REDIRECT\fP on success or
+\fBXDP_ABORTED\fP on error. For other program types, the values
+are \fBTC_ACT_REDIRECT\fP on success or \fBTC_ACT_SHOT\fP on
+error.
+.UNINDENT
+.TP
+.B \fBu32 bpf_get_route_realm(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Retrieve the realm or the route, that is to say the
+\fBtclassid\fP field of the destination for the \fIskb\fP\&. The
+identifier retrieved is a user\-provided tag, similar to the
+one used with the net_cls cgroup (see description for
+\fBbpf_get_cgroup_classid\fP() helper), but here this tag is
+held by a route (a destination entry), not by a task.
+.sp
+Retrieving this identifier works with the clsact TC egress hook
+(see also \fBtc\-bpf(8)\fP), 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 \fBnetif_keep_dst\fP() for a classful
+qdisc until the \fIskb\fP is freed.
+.sp
+This helper is available only if the kernel was compiled with
+\fBCONFIG_IP_ROUTE_CLASSID\fP configuration option.
+.TP
+.B Return
+The realm of the route for the packet associated to \fIskb\fP, or 0
+if none was found.
+.UNINDENT
+.TP
+.B \fBlong bpf_perf_event_output(void *\fP\fIctx\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB, void *\fP\fIdata\fP\fB, u64\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Write raw \fIdata\fP blob into a special BPF perf event held by
+\fImap\fP of type \fBBPF_MAP_TYPE_PERF_EVENT_ARRAY\fP\&. This perf
+event must have the following attributes: \fBPERF_SAMPLE_RAW\fP
+as \fBsample_type\fP, \fBPERF_TYPE_SOFTWARE\fP as \fBtype\fP, and
+\fBPERF_COUNT_SW_BPF_OUTPUT\fP as \fBconfig\fP\&.
+.sp
+The \fIflags\fP are used to indicate the index in \fImap\fP for which
+the value must be put, masked with \fBBPF_F_INDEX_MASK\fP\&.
+Alternatively, \fIflags\fP can be set to \fBBPF_F_CURRENT_CPU\fP
+to indicate that the index of the current CPU core should be
+used.
+.sp
+The value to write, of \fIsize\fP, is passed through eBPF stack and
+pointed by \fIdata\fP\&.
+.sp
+The context of the program \fIctx\fP needs also be passed to the
+helper.
+.sp
+On user space, a program willing to read the values needs to
+call \fBperf_event_open\fP() on the perf event (either for
+one or for all CPUs) and to store the file descriptor into the
+\fImap\fP\&. This must be done before the eBPF program can send data
+into it. An example is available in file
+\fIsamples/bpf/trace_output_user.c\fP in the Linux kernel source
+tree (the eBPF program counterpart is in
+\fIsamples/bpf/trace_output_kern.c\fP).
+.sp
+\fBbpf_perf_event_output\fP() achieves better performance
+than \fBbpf_trace_printk\fP() for sharing data with user
+space, and is much better suitable for streaming data from eBPF
+programs.
+.sp
+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:
+.INDENT 7.0
+.IP \(bu 2
+Only custom structs,
+.IP \(bu 2
+Only the packet payload, or
+.IP \(bu 2
+A combination of both.
+.UNINDENT
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_load_bytes(const void *\fP\fIskb\fP\fB, u32\fP \fIoffset\fP\fB, void *\fP\fIto\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper was provided as an easy way to load data from a
+packet. It can be used to load \fIlen\fP bytes from \fIoffset\fP from
+the packet associated to \fIskb\fP, into the buffer pointed by
+\fIto\fP\&.
+.sp
+Since Linux 4.7, usage of this helper has mostly been replaced
+by \(dqdirect packet access\(dq, enabling packet data to be
+manipulated with \fIskb\fP\fB\->data\fP and \fIskb\fP\fB\->data_end\fP
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_stackid(void *\fP\fIctx\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Walk a user or a kernel stack and return its id. To achieve
+this, the helper needs \fIctx\fP, which is a pointer to the context
+on which the tracing program is executed, and a pointer to a
+\fImap\fP of type \fBBPF_MAP_TYPE_STACK_TRACE\fP\&.
+.sp
+The last argument, \fIflags\fP, holds the number of stack frames to
+skip (from 0 to 255), masked with
+\fBBPF_F_SKIP_FIELD_MASK\fP\&. The next bits can be used to set
+a combination of the following flags:
+.INDENT 7.0
+.TP
+.B \fBBPF_F_USER_STACK\fP
+Collect a user space stack instead of a kernel stack.
+.TP
+.B \fBBPF_F_FAST_STACK_CMP\fP
+Compare stacks by hash only.
+.TP
+.B \fBBPF_F_REUSE_STACKID\fP
+If two different stacks hash into the same \fIstackid\fP,
+discard the old one.
+.UNINDENT
+.sp
+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).
+.sp
+For walking a stack, this helper is an improvement over
+\fBbpf_probe_read\fP(), which can be used with unrolled loops
+but is not efficient and consumes a lot of eBPF instructions.
+Instead, \fBbpf_get_stackid\fP() can collect up to
+\fBPERF_MAX_STACK_DEPTH\fP both kernel and user frames. Note that
+this limit can be controlled with the \fBsysctl\fP 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:
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+# sysctl kernel.perf_event_max_stack=<new value>
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.TP
+.B Return
+The positive or null stack id on success, or a negative error
+in case of failure.
+.UNINDENT
+.TP
+.B \fBs64 bpf_csum_diff(__be32 *\fP\fIfrom\fP\fB, u32\fP \fIfrom_size\fP\fB, __be32 *\fP\fIto\fP\fB, u32\fP \fIto_size\fP\fB, __wsum\fP \fIseed\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Compute a checksum difference, from the raw buffer pointed by
+\fIfrom\fP, of length \fIfrom_size\fP (that must be a multiple of 4),
+towards the raw buffer pointed by \fIto\fP, of size \fIto_size\fP
+(same remark). An optional \fIseed\fP can be added to the value
+(this can be cascaded, the seed may come from a previous call
+to the helper).
+.sp
+This is flexible enough to be used in several ways:
+.INDENT 7.0
+.IP \(bu 2
+With \fIfrom_size\fP == 0, \fIto_size\fP > 0 and \fIseed\fP set to
+checksum, it can be used when pushing new data.
+.IP \(bu 2
+With \fIfrom_size\fP > 0, \fIto_size\fP == 0 and \fIseed\fP set to
+checksum, it can be used when removing data from a packet.
+.IP \(bu 2
+With \fIfrom_size\fP > 0, \fIto_size\fP > 0 and \fIseed\fP set to 0, it
+can be used to compute a diff. Note that \fIfrom_size\fP and
+\fIto_size\fP do not need to be equal.
+.UNINDENT
+.sp
+This helper can be used in combination with
+\fBbpf_l3_csum_replace\fP() and \fBbpf_l4_csum_replace\fP(), to
+which one can feed in the difference computed with
+\fBbpf_csum_diff\fP().
+.TP
+.B Return
+The checksum result, or a negative error code in case of
+failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_get_tunnel_opt(struct sk_buff *\fP\fIskb\fP\fB, void *\fP\fIopt\fP\fB, u32\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Retrieve tunnel options metadata for the packet associated to
+\fIskb\fP, and store the raw tunnel option data to the buffer \fIopt\fP
+of \fIsize\fP\&.
+.sp
+This helper can be used with encapsulation devices that can
+operate in \(dqcollect metadata\(dq mode (please refer to the related
+note in the description of \fBbpf_skb_get_tunnel_key\fP() 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 \fBbpf_skb_get_tunnel_opt\fP() helper)
+and retrieving arbitrary TLVs (Type\-Length\-Value headers) from
+the eBPF program. This allows for full customization of these
+headers.
+.TP
+.B Return
+The size of the option data retrieved.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_set_tunnel_opt(struct sk_buff *\fP\fIskb\fP\fB, void *\fP\fIopt\fP\fB, u32\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Set tunnel options metadata for the packet associated to \fIskb\fP
+to the option data contained in the raw buffer \fIopt\fP of \fIsize\fP\&.
+.sp
+See also the description of the \fBbpf_skb_get_tunnel_opt\fP()
+helper for additional information.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_change_proto(struct sk_buff *\fP\fIskb\fP\fB, __be16\fP \fIproto\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Change the protocol of the \fIskb\fP to \fIproto\fP\&. 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
+\fBskb_store_bytes\fP() and to recompute the checksums with
+\fBbpf_l3_csum_replace\fP() and \fBbpf_l4_csum_replace\fP(). The main case for this helper is to perform NAT64
+operations out of an eBPF program.
+.sp
+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.
+.sp
+All values for \fIflags\fP are reserved for future usage, and must
+be left at zero.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_change_type(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fItype\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Change the packet type for the packet associated to \fIskb\fP\&. This
+comes down to setting \fIskb\fP\fB\->pkt_type\fP to \fItype\fP, except
+the eBPF program does not have a write access to \fIskb\fP\fB\->pkt_type\fP beside this helper. Using a helper here allows
+for graceful handling of errors.
+.sp
+The major use case is to change incoming \fIskb*s to
+**PACKET_HOST*\fP in a programmatic way instead of having to
+recirculate via \fBredirect\fP(..., \fBBPF_F_INGRESS\fP), for
+example.
+.sp
+Note that \fItype\fP only allows certain values. At this time, they
+are:
+.INDENT 7.0
+.TP
+.B \fBPACKET_HOST\fP
+Packet is for us.
+.TP
+.B \fBPACKET_BROADCAST\fP
+Send packet to all.
+.TP
+.B \fBPACKET_MULTICAST\fP
+Send packet to group.
+.TP
+.B \fBPACKET_OTHERHOST\fP
+Send packet to someone else.
+.UNINDENT
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_under_cgroup(struct sk_buff *\fP\fIskb\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u32\fP \fIindex\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Check whether \fIskb\fP is a descendant of the cgroup2 held by
+\fImap\fP of type \fBBPF_MAP_TYPE_CGROUP_ARRAY\fP, at \fIindex\fP\&.
+.TP
+.B Return
+The return value depends on the result of the test, and can be:
+.INDENT 7.0
+.IP \(bu 2
+0, if the \fIskb\fP failed the cgroup2 descendant test.
+.IP \(bu 2
+1, if the \fIskb\fP succeeded the cgroup2 descendant test.
+.IP \(bu 2
+A negative error code, if an error occurred.
+.UNINDENT
+.UNINDENT
+.TP
+.B \fBu32 bpf_get_hash_recalc(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Retrieve the hash of the packet, \fIskb\fP\fB\->hash\fP\&. 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 \fIskb\fP\fB\->hash\fP\&.
+.sp
+Calling \fBbpf_set_hash_invalid\fP(), changing a packet
+prototype with \fBbpf_skb_change_proto\fP(), or calling
+\fBbpf_skb_store_bytes\fP() with the
+\fBBPF_F_INVALIDATE_HASH\fP are actions susceptible to clear
+the hash and to trigger a new computation for the next call to
+\fBbpf_get_hash_recalc\fP().
+.TP
+.B Return
+The 32\-bit hash.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_current_task(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the current task.
+.TP
+.B Return
+A pointer to the current task struct.
+.UNINDENT
+.TP
+.B \fBlong bpf_probe_write_user(void *\fP\fIdst\fP\fB, const void *\fP\fIsrc\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Attempt in a safe way to write \fIlen\fP bytes from the buffer
+\fIsrc\fP to \fIdst\fP in memory. It only works for threads that are in
+user context, and \fIdst\fP must be a valid user space address.
+.sp
+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.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_current_task_under_cgroup(struct bpf_map *\fP\fImap\fP\fB, u32\fP \fIindex\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B 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
+\fImap\fP of type \fBBPF_MAP_TYPE_CGROUP_ARRAY\fP, at \fIindex\fP\&.
+.TP
+.B Return
+The return value depends on the result of the test, and can be:
+.INDENT 7.0
+.IP \(bu 2
+1, if current task belongs to the cgroup2.
+.IP \(bu 2
+0, if current task does not belong to the cgroup2.
+.IP \(bu 2
+A negative error code, if an error occurred.
+.UNINDENT
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_change_tail(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Resize (trim or grow) the packet associated to \fIskb\fP to the
+new \fIlen\fP\&. The \fIflags\fP are reserved for future usage, and must
+be left at zero.
+.sp
+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 \fBbpf_skb_store_bytes\fP(),
+\fBbpf_l3_csum_replace\fP(), \fBbpf_l3_csum_replace\fP()
+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
+\fIskb\fP\&.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_pull_data(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Pull in non\-linear data in case the \fIskb\fP is non\-linear and not
+all of \fIlen\fP are part of the linear section. Make \fIlen\fP bytes
+from \fIskb\fP readable and writable. If a zero value is passed for
+\fIlen\fP, then all bytes in the linear part of \fIskb\fP will be made
+readable and writable.
+.sp
+This helper is only needed for reading and writing with direct
+packet access.
+.sp
+For direct packet access, testing that offsets to access
+are within packet boundaries (test on \fIskb\fP\fB\->data_end\fP) is
+susceptible to fail if offsets are invalid, or if the requested
+data is in non\-linear parts of the \fIskb\fP\&. 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
+\fBbpf_skb_load_bytes\fP() helper is a first solution to access
+the data. Another one consists in using \fBbpf_skb_pull_data\fP
+to pull in once the non\-linear parts, then retesting and
+eventually access the data.
+.sp
+At the same time, this also makes sure the \fIskb\fP 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
+\fBbpf_skb_pull_data()\fP to effectively unclone the \fIskb\fP from
+the very beginning in case it is indeed cloned.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBs64 bpf_csum_update(struct sk_buff *\fP\fIskb\fP\fB, __wsum\fP \fIcsum\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Add the checksum \fIcsum\fP into \fIskb\fP\fB\->csum\fP 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 \fBbpf_csum_diff\fP(), in particular
+when the checksum needs to be updated after data has been
+written into the packet through direct packet access.
+.TP
+.B Return
+The checksum on success, or a negative error code in case of
+failure.
+.UNINDENT
+.TP
+.B \fBvoid bpf_set_hash_invalid(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Invalidate the current \fIskb\fP\fB\->hash\fP\&. 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 \fBbpf_get_hash_recalc\fP() helper is called.
+.TP
+.B Return
+void.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_numa_node_id(void)\fP
+.INDENT 7.0
+.TP
+.B 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
+\fBSO_ATTACH_REUSEPORT_EBPF\fP option (see also \fBsocket(7)\fP),
+but the helper is also available to other eBPF program types,
+similarly to \fBbpf_get_smp_processor_id\fP().
+.TP
+.B Return
+The id of current NUMA node.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_change_head(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Grows headroom of packet associated to \fIskb\fP and adjusts the
+offset of the MAC header accordingly, adding \fIlen\fP bytes of
+space. It automatically extends and reallocates memory as
+required.
+.sp
+This helper can be used on a layer 3 \fIskb\fP to push a MAC header
+for redirection into a layer 2 device.
+.sp
+All values for \fIflags\fP are reserved for future usage, and must
+be left at zero.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_xdp_adjust_head(struct xdp_buff *\fP\fIxdp_md\fP\fB, int\fP \fIdelta\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Adjust (move) \fIxdp_md\fP\fB\->data\fP by \fIdelta\fP bytes. Note that
+it is possible to use a negative value for \fIdelta\fP\&. This helper
+can be used to prepare the packet for pushing or popping
+headers.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_probe_read_str(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIunsafe_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Copy a NUL terminated string from an unsafe kernel address
+\fIunsafe_ptr\fP to \fIdst\fP\&. See \fBbpf_probe_read_kernel_str\fP() for
+more details.
+.sp
+Generally, use \fBbpf_probe_read_user_str\fP() or
+\fBbpf_probe_read_kernel_str\fP() instead.
+.TP
+.B Return
+On success, the strictly positive length of the string,
+including the trailing NUL character. On error, a negative
+value.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_socket_cookie(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+If the \fBstruct sk_buff\fP pointed by \fIskb\fP 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.
+.TP
+.B Return
+A 8\-byte long unique number on success, or 0 if the socket
+field is missing inside \fIskb\fP\&.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_socket_cookie(struct bpf_sock_addr *\fP\fIctx\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Equivalent to bpf_get_socket_cookie() helper that accepts
+\fIskb\fP, but gets socket from \fBstruct bpf_sock_addr\fP context.
+.TP
+.B Return
+A 8\-byte long unique number.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_socket_cookie(struct bpf_sock_ops *\fP\fIctx\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Equivalent to \fBbpf_get_socket_cookie\fP() helper that accepts
+\fIskb\fP, but gets socket from \fBstruct bpf_sock_ops\fP context.
+.TP
+.B Return
+A 8\-byte long unique number.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_socket_cookie(struct sock *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Equivalent to \fBbpf_get_socket_cookie\fP() helper that accepts
+\fIsk\fP, but gets socket from a BTF \fBstruct sock\fP\&. This helper
+also works for sleepable programs.
+.TP
+.B Return
+A 8\-byte long unique number or 0 if \fIsk\fP is NULL.
+.UNINDENT
+.TP
+.B \fBu32 bpf_get_socket_uid(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the owner UID of the socked associated to \fIskb\fP\&.
+.TP
+.B Return
+The owner UID of the socket associated to \fIskb\fP\&. If the socket
+is \fBNULL\fP, or if it is not a full socket (i.e. if it is a
+time\-wait or a request socket instead), \fBoverflowuid\fP value
+is returned (note that \fBoverflowuid\fP might also be the actual
+UID value for the socket).
+.UNINDENT
+.TP
+.B \fBlong bpf_set_hash(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIhash\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Set the full hash for \fIskb\fP (set the field \fIskb\fP\fB\->hash\fP)
+to value \fIhash\fP\&.
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBlong bpf_setsockopt(void *\fP\fIbpf_socket\fP\fB, int\fP \fIlevel\fP\fB, int\fP \fIoptname\fP\fB, void *\fP\fIoptval\fP\fB, int\fP \fIoptlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Emulate a call to \fBsetsockopt()\fP on the socket associated to
+\fIbpf_socket\fP, which must be a full socket. The \fIlevel\fP at
+which the option resides and the name \fIoptname\fP of the option
+must be specified, see \fBsetsockopt(2)\fP for more information.
+The option value of length \fIoptlen\fP is pointed by \fIoptval\fP\&.
+.sp
+\fIbpf_socket\fP should be one of the following:
+.INDENT 7.0
+.IP \(bu 2
+\fBstruct bpf_sock_ops\fP for \fBBPF_PROG_TYPE_SOCK_OPS\fP\&.
+.IP \(bu 2
+\fBstruct bpf_sock_addr\fP for \fBBPF_CGROUP_INET4_CONNECT\fP
+and \fBBPF_CGROUP_INET6_CONNECT\fP\&.
+.UNINDENT
+.sp
+This helper actually implements a subset of \fBsetsockopt()\fP\&.
+It supports the following \fIlevel\fPs:
+.INDENT 7.0
+.IP \(bu 2
+\fBSOL_SOCKET\fP, which supports the following \fIoptname\fPs:
+\fBSO_RCVBUF\fP, \fBSO_SNDBUF\fP, \fBSO_MAX_PACING_RATE\fP,
+\fBSO_PRIORITY\fP, \fBSO_RCVLOWAT\fP, \fBSO_MARK\fP,
+\fBSO_BINDTODEVICE\fP, \fBSO_KEEPALIVE\fP, \fBSO_REUSEADDR\fP,
+\fBSO_REUSEPORT\fP, \fBSO_BINDTOIFINDEX\fP, \fBSO_TXREHASH\fP\&.
+.IP \(bu 2
+\fBIPPROTO_TCP\fP, which supports the following \fIoptname\fPs:
+\fBTCP_CONGESTION\fP, \fBTCP_BPF_IW\fP,
+\fBTCP_BPF_SNDCWND_CLAMP\fP, \fBTCP_SAVE_SYN\fP,
+\fBTCP_KEEPIDLE\fP, \fBTCP_KEEPINTVL\fP, \fBTCP_KEEPCNT\fP,
+\fBTCP_SYNCNT\fP, \fBTCP_USER_TIMEOUT\fP, \fBTCP_NOTSENT_LOWAT\fP,
+\fBTCP_NODELAY\fP, \fBTCP_MAXSEG\fP, \fBTCP_WINDOW_CLAMP\fP,
+\fBTCP_THIN_LINEAR_TIMEOUTS\fP, \fBTCP_BPF_DELACK_MAX\fP,
+\fBTCP_BPF_RTO_MIN\fP\&.
+.IP \(bu 2
+\fBIPPROTO_IP\fP, which supports \fIoptname\fP \fBIP_TOS\fP\&.
+.IP \(bu 2
+\fBIPPROTO_IPV6\fP, which supports the following \fIoptname\fPs:
+\fBIPV6_TCLASS\fP, \fBIPV6_AUTOFLOWLABEL\fP\&.
+.UNINDENT
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_adjust_room(struct sk_buff *\fP\fIskb\fP\fB, s32\fP \fIlen_diff\fP\fB, u32\fP \fImode\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Grow or shrink the room for data in the packet associated to
+\fIskb\fP by \fIlen_diff\fP, and according to the selected \fImode\fP\&.
+.sp
+By default, the helper will reset any offloaded checksum
+indicator of the skb to CHECKSUM_NONE. This can be avoided
+by the following flag:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_F_ADJ_ROOM_NO_CSUM_RESET\fP: Do not reset offloaded
+checksum data of the skb to CHECKSUM_NONE.
+.UNINDENT
+.sp
+There are two supported modes at this time:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_ADJ_ROOM_MAC\fP: Adjust room at the mac layer
+(room space is added or removed between the layer 2 and
+layer 3 headers).
+.IP \(bu 2
+\fBBPF_ADJ_ROOM_NET\fP: Adjust room at the network layer
+(room space is added or removed between the layer 3 and
+layer 4 headers).
+.UNINDENT
+.sp
+The following flags are supported at this time:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_F_ADJ_ROOM_FIXED_GSO\fP: Do not adjust gso_size.
+Adjusting mss in this way is not allowed for datagrams.
+.IP \(bu 2
+\fBBPF_F_ADJ_ROOM_ENCAP_L3_IPV4\fP,
+\fBBPF_F_ADJ_ROOM_ENCAP_L3_IPV6\fP:
+Any new space is reserved to hold a tunnel header.
+Configure skb offsets and other fields accordingly.
+.IP \(bu 2
+\fBBPF_F_ADJ_ROOM_ENCAP_L4_GRE\fP,
+\fBBPF_F_ADJ_ROOM_ENCAP_L4_UDP\fP:
+Use with ENCAP_L3 flags to further specify the tunnel type.
+.IP \(bu 2
+\fBBPF_F_ADJ_ROOM_ENCAP_L2\fP(\fIlen\fP):
+Use with ENCAP_L3/L4 flags to further specify the tunnel
+type; \fIlen\fP is the length of the inner MAC header.
+.IP \(bu 2
+\fBBPF_F_ADJ_ROOM_ENCAP_L2_ETH\fP:
+Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
+L2 type as Ethernet.
+.UNINDENT
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_redirect_map(struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Redirect the packet to the endpoint referenced by \fImap\fP at
+index \fIkey\fP\&. Depending on its type, this \fImap\fP 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).
+.sp
+The lower two bits of \fIflags\fP 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 \fBXDP_TX\fP, as chosen
+by the caller. The higher bits of \fIflags\fP can be set to
+BPF_F_BROADCAST or BPF_F_EXCLUDE_INGRESS as defined below.
+.sp
+With BPF_F_BROADCAST the packet will be broadcasted to all the
+interfaces in the map, with BPF_F_EXCLUDE_INGRESS the ingress
+interface will be excluded when do broadcasting.
+.sp
+See also \fBbpf_redirect\fP(), which only supports redirecting
+to an ifindex, but doesn\(aqt require a map to do so.
+.TP
+.B Return
+\fBXDP_REDIRECT\fP on success, or the value of the two lower bits
+of the \fIflags\fP argument on error.
+.UNINDENT
+.TP
+.B \fBlong bpf_sk_redirect_map(struct sk_buff *\fP\fIskb\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u32\fP \fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Redirect the packet to the socket referenced by \fImap\fP (of type
+\fBBPF_MAP_TYPE_SOCKMAP\fP) at index \fIkey\fP\&. Both ingress and
+egress interfaces can be used for redirection. The
+\fBBPF_F_INGRESS\fP value in \fIflags\fP 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.
+.TP
+.B Return
+\fBSK_PASS\fP on success, or \fBSK_DROP\fP on error.
+.UNINDENT
+.TP
+.B \fBlong bpf_sock_map_update(struct bpf_sock_ops *\fP\fIskops\fP\fB, struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Add an entry to, or update a \fImap\fP referencing sockets. The
+\fIskops\fP is used as a new value for the entry associated to
+\fIkey\fP\&. \fIflags\fP is one of:
+.INDENT 7.0
+.TP
+.B \fBBPF_NOEXIST\fP
+The entry for \fIkey\fP must not exist in the map.
+.TP
+.B \fBBPF_EXIST\fP
+The entry for \fIkey\fP must already exist in the map.
+.TP
+.B \fBBPF_ANY\fP
+No condition on the existence of the entry for \fIkey\fP\&.
+.UNINDENT
+.sp
+If the \fImap\fP 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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_xdp_adjust_meta(struct xdp_buff *\fP\fIxdp_md\fP\fB, int\fP \fIdelta\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Adjust the address pointed by \fIxdp_md\fP\fB\->data_meta\fP by
+\fIdelta\fP (which can be positive or negative). Note that this
+operation modifies the address stored in \fIxdp_md\fP\fB\->data\fP,
+so the latter must be loaded only after the helper has been
+called.
+.sp
+The use of \fIxdp_md\fP\fB\->data_meta\fP 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 \fBmark\fP or
+\fBpriority\fP 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.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_perf_event_read_value(struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB, struct bpf_perf_event_value *\fP\fIbuf\fP\fB, u32\fP \fIbuf_size\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Read the value of a perf event counter, and store it into \fIbuf\fP
+of size \fIbuf_size\fP\&. This helper relies on a \fImap\fP of type
+\fBBPF_MAP_TYPE_PERF_EVENT_ARRAY\fP\&. The nature of the perf event
+counter is selected when \fImap\fP is updated with perf event file
+descriptors. The \fImap\fP 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 \fIflags\fP, that
+contains the index of the CPU to look up, masked with
+\fBBPF_F_INDEX_MASK\fP\&. Alternatively, \fIflags\fP can be set to
+\fBBPF_F_CURRENT_CPU\fP to indicate that the value for the
+current CPU should be retrieved.
+.sp
+This helper behaves in a way close to
+\fBbpf_perf_event_read\fP() helper, save that instead of
+just returning the value observed, it fills the \fIbuf\fP
+structure. This allows for additional data to be retrieved: in
+particular, the enabled and running times (in \fIbuf\fP\fB\->enabled\fP and \fIbuf\fP\fB\->running\fP, respectively) are
+copied. In general, \fBbpf_perf_event_read_value\fP() is
+recommended over \fBbpf_perf_event_read\fP(), which has some
+ABI issues and provides fewer functionalities.
+.sp
+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.
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+normalized_counter = counter * t_enabled / t_running
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_perf_prog_read_value(struct bpf_perf_event_data *\fP\fIctx\fP\fB, struct bpf_perf_event_value *\fP\fIbuf\fP\fB, u32\fP \fIbuf_size\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For en eBPF program attached to a perf event, retrieve the
+value of the event counter associated to \fIctx\fP and store it in
+the structure pointed by \fIbuf\fP and of size \fIbuf_size\fP\&. Enabled
+and running times are also stored in the structure (see
+description of helper \fBbpf_perf_event_read_value\fP() for
+more details).
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_getsockopt(void *\fP\fIbpf_socket\fP\fB, int\fP \fIlevel\fP\fB, int\fP \fIoptname\fP\fB, void *\fP\fIoptval\fP\fB, int\fP \fIoptlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Emulate a call to \fBgetsockopt()\fP on the socket associated to
+\fIbpf_socket\fP, which must be a full socket. The \fIlevel\fP at
+which the option resides and the name \fIoptname\fP of the option
+must be specified, see \fBgetsockopt(2)\fP for more information.
+The retrieved value is stored in the structure pointed by
+\fIopval\fP and of length \fIoptlen\fP\&.
+.sp
+\fIbpf_socket\fP should be one of the following:
+.INDENT 7.0
+.IP \(bu 2
+\fBstruct bpf_sock_ops\fP for \fBBPF_PROG_TYPE_SOCK_OPS\fP\&.
+.IP \(bu 2
+\fBstruct bpf_sock_addr\fP for \fBBPF_CGROUP_INET4_CONNECT\fP
+and \fBBPF_CGROUP_INET6_CONNECT\fP\&.
+.UNINDENT
+.sp
+This helper actually implements a subset of \fBgetsockopt()\fP\&.
+It supports the same set of \fIoptname\fPs that is supported by
+the \fBbpf_setsockopt\fP() helper.  The exceptions are
+\fBTCP_BPF_*\fP is \fBbpf_setsockopt\fP() only and
+\fBTCP_SAVED_SYN\fP is \fBbpf_getsockopt\fP() only.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_override_return(struct pt_regs *\fP\fIregs\fP\fB, u64\fP \fIrc\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Used for error injection, this helper uses kprobes to override
+the return value of the probed function, and to set it to \fIrc\fP\&.
+The first argument is the context \fIregs\fP on which the kprobe
+works.
+.sp
+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.
+.sp
+This helper has security implications, and thus is subject to
+restrictions. It is only available if the kernel was compiled
+with the \fBCONFIG_BPF_KPROBE_OVERRIDE\fP configuration
+option, and in this case it only works on functions tagged with
+\fBALLOW_ERROR_INJECTION\fP in the kernel code.
+.sp
+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.
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBlong bpf_sock_ops_cb_flags_set(struct bpf_sock_ops *\fP\fIbpf_sock\fP\fB, int\fP \fIargval\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Attempt to set the value of the \fBbpf_sock_ops_cb_flags\fP field
+for the full TCP socket associated to \fIbpf_sock_ops\fP to
+\fIargval\fP\&.
+.sp
+The primary use of this field is to determine if there should
+be calls to eBPF programs of type
+\fBBPF_PROG_TYPE_SOCK_OPS\fP 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.
+.sp
+\fIargval\fP is a flag array which can combine these flags:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_SOCK_OPS_RTO_CB_FLAG\fP (retransmission time out)
+.IP \(bu 2
+\fBBPF_SOCK_OPS_RETRANS_CB_FLAG\fP (retransmission)
+.IP \(bu 2
+\fBBPF_SOCK_OPS_STATE_CB_FLAG\fP (TCP state change)
+.IP \(bu 2
+\fBBPF_SOCK_OPS_RTT_CB_FLAG\fP (every RTT)
+.UNINDENT
+.sp
+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:
+.INDENT 7.0
+.TP
+.B \fBbpf_sock_ops_cb_flags_set(bpf_sock,\fP
+\fBbpf_sock\->bpf_sock_ops_cb_flags & ~BPF_SOCK_OPS_RTO_CB_FLAG)\fP
+.UNINDENT
+.sp
+Here are some examples of where one could call such eBPF
+program:
+.INDENT 7.0
+.IP \(bu 2
+When RTO fires.
+.IP \(bu 2
+When a packet is retransmitted.
+.IP \(bu 2
+When the connection terminates.
+.IP \(bu 2
+When a packet is sent.
+.IP \(bu 2
+When a packet is received.
+.UNINDENT
+.TP
+.B Return
+Code \fB\-EINVAL\fP 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).
+.UNINDENT
+.TP
+.B \fBlong bpf_msg_redirect_map(struct sk_msg_buff *\fP\fImsg\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u32\fP \fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is used in programs implementing policies at the
+socket level. If the message \fImsg\fP is allowed to pass (i.e. if
+the verdict eBPF program returns \fBSK_PASS\fP), redirect it to
+the socket referenced by \fImap\fP (of type
+\fBBPF_MAP_TYPE_SOCKMAP\fP) at index \fIkey\fP\&. Both ingress and
+egress interfaces can be used for redirection. The
+\fBBPF_F_INGRESS\fP value in \fIflags\fP 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.
+.TP
+.B Return
+\fBSK_PASS\fP on success, or \fBSK_DROP\fP on error.
+.UNINDENT
+.TP
+.B \fBlong bpf_msg_apply_bytes(struct sk_msg_buff *\fP\fImsg\fP\fB, u32\fP \fIbytes\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For socket policies, apply the verdict of the eBPF program to
+the next \fIbytes\fP (number of bytes) of message \fImsg\fP\&.
+.sp
+For example, this helper can be used in the following cases:
+.INDENT 7.0
+.IP \(bu 2
+A single \fBsendmsg\fP() or \fBsendfile\fP() system call
+contains multiple logical messages that the eBPF program is
+supposed to read and for which it should apply a verdict.
+.IP \(bu 2
+An eBPF program only cares to read the first \fIbytes\fP of a
+\fImsg\fP\&. 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.
+.UNINDENT
+.sp
+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 \fIbytes\fP\&. If \fIbytes\fP is
+smaller than the current data being processed from a
+\fBsendmsg\fP() or \fBsendfile\fP() system call, the first
+\fIbytes\fP will be sent and the eBPF program will be re\-run with
+the pointer for start of data pointing to byte number \fIbytes\fP
+\fB+ 1\fP\&. If \fIbytes\fP is larger than the current data being
+processed, then the eBPF verdict will be applied to multiple
+\fBsendmsg\fP() or \fBsendfile\fP() calls until \fIbytes\fP are
+consumed.
+.sp
+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 \fIbytes\fP and is sent as it is received.
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBlong bpf_msg_cork_bytes(struct sk_msg_buff *\fP\fImsg\fP\fB, u32\fP \fIbytes\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For socket policies, prevent the execution of the verdict eBPF
+program for message \fImsg\fP until \fIbytes\fP (byte number) have been
+accumulated.
+.sp
+This can be used when one needs a specific number of bytes
+before a verdict can be assigned, even if the data spans
+multiple \fBsendmsg\fP() or \fBsendfile\fP() calls. The extreme
+case would be a user calling \fBsendmsg\fP() repeatedly with
+1\-byte long message segments. Obviously, this is bad for
+performance, but it is still valid. If the eBPF program needs
+\fIbytes\fP bytes to validate a header, this helper can be used to
+prevent the eBPF program to be called again until \fIbytes\fP have
+been accumulated.
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBlong bpf_msg_pull_data(struct sk_msg_buff *\fP\fImsg\fP\fB, u32\fP \fIstart\fP\fB, u32\fP \fIend\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For socket policies, pull in non\-linear data from user space
+for \fImsg\fP and set pointers \fImsg\fP\fB\->data\fP and \fImsg\fP\fB\->data_end\fP to \fIstart\fP and \fIend\fP bytes offsets into \fImsg\fP,
+respectively.
+.sp
+If a program of type \fBBPF_PROG_TYPE_SK_MSG\fP is run on a
+\fImsg\fP it can only parse data that the (\fBdata\fP, \fBdata_end\fP)
+pointers have already consumed. For \fBsendmsg\fP() hooks this
+is likely the first scatterlist element. But for calls relying
+on the \fBsendpage\fP handler (e.g. \fBsendfile\fP()) this will
+be the range (\fB0\fP, \fB0\fP) 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).
+.sp
+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.
+.sp
+All values for \fIflags\fP are reserved for future usage, and must
+be left at zero.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_bind(struct bpf_sock_addr *\fP\fIctx\fP\fB, struct sockaddr *\fP\fIaddr\fP\fB, int\fP \fIaddr_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Bind the socket associated to \fIctx\fP to the address pointed by
+\fIaddr\fP, of length \fIaddr_len\fP\&. 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.
+.sp
+This helper works for IPv4 and IPv6, TCP and UDP sockets. The
+domain (\fIaddr\fP\fB\->sa_family\fP) must be \fBAF_INET\fP (or
+\fBAF_INET6\fP). It\(aqs advised to pass zero port (\fBsin_port\fP
+or \fBsin6_port\fP) 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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_xdp_adjust_tail(struct xdp_buff *\fP\fIxdp_md\fP\fB, int\fP \fIdelta\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Adjust (move) \fIxdp_md\fP\fB\->data_end\fP by \fIdelta\fP bytes. It is
+possible to both shrink and grow the packet tail.
+Shrink done via \fIdelta\fP being a negative integer.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_get_xfrm_state(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIindex\fP\fB, struct bpf_xfrm_state *\fP\fIxfrm_state\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Retrieve the XFRM state (IP transform framework, see also
+\fBip\-xfrm(8)\fP) at \fIindex\fP in XFRM \(dqsecurity path\(dq for \fIskb\fP\&.
+.sp
+The retrieved value is stored in the \fBstruct bpf_xfrm_state\fP
+pointed by \fIxfrm_state\fP and of length \fIsize\fP\&.
+.sp
+All values for \fIflags\fP are reserved for future usage, and must
+be left at zero.
+.sp
+This helper is available only if the kernel was compiled with
+\fBCONFIG_XFRM\fP configuration option.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_stack(void *\fP\fIctx\fP\fB, void *\fP\fIbuf\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return a user or a kernel stack in bpf program provided buffer.
+To achieve this, the helper needs \fIctx\fP, which is a pointer
+to the context on which the tracing program is executed.
+To store the stacktrace, the bpf program provides \fIbuf\fP with
+a nonnegative \fIsize\fP\&.
+.sp
+The last argument, \fIflags\fP, holds the number of stack frames to
+skip (from 0 to 255), masked with
+\fBBPF_F_SKIP_FIELD_MASK\fP\&. The next bits can be used to set
+the following flags:
+.INDENT 7.0
+.TP
+.B \fBBPF_F_USER_STACK\fP
+Collect a user space stack instead of a kernel stack.
+.TP
+.B \fBBPF_F_USER_BUILD_ID\fP
+Collect (build_id, file_offset) instead of ips for user
+stack, only valid if \fBBPF_F_USER_STACK\fP is also
+specified.
+.sp
+\fIfile_offset\fP is an offset relative to the beginning
+of the executable or shared object file backing the vma
+which the \fIip\fP falls in. It is \fInot\fP an offset relative
+to that object\(aqs base address. Accordingly, it must be
+adjusted by adding (sh_addr \- sh_offset), where
+sh_{addr,offset} correspond to the executable section
+containing \fIfile_offset\fP in the object, for comparisons
+to symbols\(aq st_value to be valid.
+.UNINDENT
+.sp
+\fBbpf_get_stack\fP() can collect up to
+\fBPERF_MAX_STACK_DEPTH\fP both kernel and user frames, subject
+to sufficient large buffer size. Note that
+this limit can be controlled with the \fBsysctl\fP 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:
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+# sysctl kernel.perf_event_max_stack=<new value>
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.TP
+.B Return
+The non\-negative copied \fIbuf\fP length equal to or less than
+\fIsize\fP on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_load_bytes_relative(const void *\fP\fIskb\fP\fB, u32\fP \fIoffset\fP\fB, void *\fP\fIto\fP\fB, u32\fP \fIlen\fP\fB, u32\fP \fIstart_header\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is similar to \fBbpf_skb_load_bytes\fP() in that
+it provides an easy way to load \fIlen\fP bytes from \fIoffset\fP
+from the packet associated to \fIskb\fP, into the buffer pointed
+by \fIto\fP\&. The difference to \fBbpf_skb_load_bytes\fP() is that
+a fifth argument \fIstart_header\fP exists in order to select a
+base offset to start from. \fIstart_header\fP can be one of:
+.INDENT 7.0
+.TP
+.B \fBBPF_HDR_START_MAC\fP
+Base offset to load data from is \fIskb\fP\(aqs mac header.
+.TP
+.B \fBBPF_HDR_START_NET\fP
+Base offset to load data from is \fIskb\fP\(aqs network header.
+.UNINDENT
+.sp
+In general, \(dqdirect packet access\(dq is the preferred method to
+access packet data, however, this helper is in particular useful
+in socket filters where \fIskb\fP\fB\->data\fP does not always point
+to the start of the mac header and where \(dqdirect packet access\(dq
+is not available.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_fib_lookup(void *\fP\fIctx\fP\fB, struct bpf_fib_lookup *\fP\fIparams\fP\fB, int\fP \fIplen\fP\fB, u32\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Do FIB lookup in kernel tables using parameters in \fIparams\fP\&.
+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.
+.sp
+\fIplen\fP argument is the size of the passed in struct.
+\fIflags\fP argument can be a combination of one or more of the
+following values:
+.INDENT 7.0
+.TP
+.B \fBBPF_FIB_LOOKUP_DIRECT\fP
+Do a direct table lookup vs full lookup using FIB
+rules.
+.TP
+.B \fBBPF_FIB_LOOKUP_OUTPUT\fP
+Perform lookup from an egress perspective (default is
+ingress).
+.UNINDENT
+.sp
+\fIctx\fP is either \fBstruct xdp_md\fP for XDP programs or
+\fBstruct sk_buff\fP tc cls_act programs.
+.TP
+.B Return
+.INDENT 7.0
+.IP \(bu 2
+< 0 if any input argument is invalid
+.IP \(bu 2
+0 on success (packet is forwarded, nexthop neighbor exists)
+.IP \(bu 2
+> 0 one of \fBBPF_FIB_LKUP_RET_\fP codes explaining why the
+packet is not forwarded or needs assist from full stack
+.UNINDENT
+.sp
+If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU
+was exceeded and output params\->mtu_result contains the MTU.
+.UNINDENT
+.TP
+.B \fBlong bpf_sock_hash_update(struct bpf_sock_ops *\fP\fIskops\fP\fB, struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Add an entry to, or update a sockhash \fImap\fP referencing sockets.
+The \fIskops\fP is used as a new value for the entry associated to
+\fIkey\fP\&. \fIflags\fP is one of:
+.INDENT 7.0
+.TP
+.B \fBBPF_NOEXIST\fP
+The entry for \fIkey\fP must not exist in the map.
+.TP
+.B \fBBPF_EXIST\fP
+The entry for \fIkey\fP must already exist in the map.
+.TP
+.B \fBBPF_ANY\fP
+No condition on the existence of the entry for \fIkey\fP\&.
+.UNINDENT
+.sp
+If the \fImap\fP 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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_msg_redirect_hash(struct sk_msg_buff *\fP\fImsg\fP\fB, struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is used in programs implementing policies at the
+socket level. If the message \fImsg\fP is allowed to pass (i.e. if
+the verdict eBPF program returns \fBSK_PASS\fP), redirect it to
+the socket referenced by \fImap\fP (of type
+\fBBPF_MAP_TYPE_SOCKHASH\fP) using hash \fIkey\fP\&. Both ingress and
+egress interfaces can be used for redirection. The
+\fBBPF_F_INGRESS\fP value in \fIflags\fP 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.
+.TP
+.B Return
+\fBSK_PASS\fP on success, or \fBSK_DROP\fP on error.
+.UNINDENT
+.TP
+.B \fBlong bpf_sk_redirect_hash(struct sk_buff *\fP\fIskb\fP\fB, struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is used in programs implementing policies at the
+skb socket level. If the sk_buff \fIskb\fP is allowed to pass (i.e.
+if the verdict eBPF program returns \fBSK_PASS\fP), redirect it
+to the socket referenced by \fImap\fP (of type
+\fBBPF_MAP_TYPE_SOCKHASH\fP) using hash \fIkey\fP\&. Both ingress and
+egress interfaces can be used for redirection. The
+\fBBPF_F_INGRESS\fP value in \fIflags\fP 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.
+.TP
+.B Return
+\fBSK_PASS\fP on success, or \fBSK_DROP\fP on error.
+.UNINDENT
+.TP
+.B \fBlong bpf_lwt_push_encap(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fItype\fP\fB, void *\fP\fIhdr\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Encapsulate the packet associated to \fIskb\fP within a Layer 3
+protocol header. This header is provided in the buffer at
+address \fIhdr\fP, with \fIlen\fP its size in bytes. \fItype\fP indicates
+the protocol of the header and can be one of:
+.INDENT 7.0
+.TP
+.B \fBBPF_LWT_ENCAP_SEG6\fP
+IPv6 encapsulation with Segment Routing Header
+(\fBstruct ipv6_sr_hdr\fP). \fIhdr\fP only contains the SRH,
+the IPv6 header is computed by the kernel.
+.TP
+.B \fBBPF_LWT_ENCAP_SEG6_INLINE\fP
+Only works if \fIskb\fP contains an IPv6 packet. Insert a
+Segment Routing Header (\fBstruct ipv6_sr_hdr\fP) inside
+the IPv6 header.
+.TP
+.B \fBBPF_LWT_ENCAP_IP\fP
+IP encapsulation (GRE/GUE/IPIP/etc). The outer header
+must be IPv4 or IPv6, followed by zero or more
+additional headers, up to \fBLWT_BPF_MAX_HEADROOM\fP
+total bytes in all prepended headers. Please note that
+if \fBskb_is_gso\fP(\fIskb\fP) is true, no more than two
+headers can be prepended, and the inner header, if
+present, should be either GRE or UDP/GUE.
+.UNINDENT
+.sp
+\fBBPF_LWT_ENCAP_SEG6\fP* types can be called by BPF programs
+of type \fBBPF_PROG_TYPE_LWT_IN\fP; \fBBPF_LWT_ENCAP_IP\fP type can
+be called by bpf programs of types \fBBPF_PROG_TYPE_LWT_IN\fP and
+\fBBPF_PROG_TYPE_LWT_XMIT\fP\&.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_lwt_seg6_store_bytes(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIoffset\fP\fB, const void *\fP\fIfrom\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Store \fIlen\fP bytes from address \fIfrom\fP into the packet
+associated to \fIskb\fP, at \fIoffset\fP\&. Only the flags, tag and TLVs
+inside the outermost IPv6 Segment Routing Header can be
+modified through this helper.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_lwt_seg6_adjust_srh(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIoffset\fP\fB, s32\fP \fIdelta\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Adjust the size allocated to TLVs in the outermost IPv6
+Segment Routing Header contained in the packet associated to
+\fIskb\fP, at position \fIoffset\fP by \fIdelta\fP bytes. Only offsets
+after the segments are accepted. \fIdelta\fP can be as well
+positive (growing) as negative (shrinking).
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_lwt_seg6_action(struct sk_buff *\fP\fIskb\fP\fB, u32\fP \fIaction\fP\fB, void *\fP\fIparam\fP\fB, u32\fP \fIparam_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Apply an IPv6 Segment Routing action of type \fIaction\fP to the
+packet associated to \fIskb\fP\&. Each action takes a parameter
+contained at address \fIparam\fP, and of length \fIparam_len\fP bytes.
+\fIaction\fP can be one of:
+.INDENT 7.0
+.TP
+.B \fBSEG6_LOCAL_ACTION_END_X\fP
+End.X action: Endpoint with Layer\-3 cross\-connect.
+Type of \fIparam\fP: \fBstruct in6_addr\fP\&.
+.TP
+.B \fBSEG6_LOCAL_ACTION_END_T\fP
+End.T action: Endpoint with specific IPv6 table lookup.
+Type of \fIparam\fP: \fBint\fP\&.
+.TP
+.B \fBSEG6_LOCAL_ACTION_END_B6\fP
+End.B6 action: Endpoint bound to an SRv6 policy.
+Type of \fIparam\fP: \fBstruct ipv6_sr_hdr\fP\&.
+.TP
+.B \fBSEG6_LOCAL_ACTION_END_B6_ENCAP\fP
+End.B6.Encap action: Endpoint bound to an SRv6
+encapsulation policy.
+Type of \fIparam\fP: \fBstruct ipv6_sr_hdr\fP\&.
+.UNINDENT
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_rc_repeat(void *\fP\fIctx\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B 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.
+.sp
+Some IR protocols like NEC have a special IR message for
+repeating last button, for when a button is held down.
+.sp
+The \fIctx\fP should point to the lirc sample as passed into
+the program.
+.sp
+This helper is only available is the kernel was compiled with
+the \fBCONFIG_BPF_LIRC_MODE2\fP configuration option set to
+\(dq\fBy\fP\(dq.
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBlong bpf_rc_keydown(void *\fP\fIctx\fP\fB, u32\fP \fIprotocol\fP\fB, u64\fP \fIscancode\fP\fB, u32\fP \fItoggle\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is used in programs implementing IR decoding, to
+report a successfully decoded key press with \fIscancode\fP,
+\fItoggle\fP value in the given \fIprotocol\fP\&. 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
+\fBbpf_rc_keydown\fP() again with the same values, or calling
+\fBbpf_rc_repeat\fP().
+.sp
+Some protocols include a toggle bit, in case the button was
+released and pressed again between consecutive scancodes.
+.sp
+The \fIctx\fP should point to the lirc sample as passed into
+the program.
+.sp
+The \fIprotocol\fP is the decoded protocol number (see
+\fBenum rc_proto\fP for some predefined values).
+.sp
+This helper is only available is the kernel was compiled with
+the \fBCONFIG_BPF_LIRC_MODE2\fP configuration option set to
+\(dq\fBy\fP\(dq.
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBu64 bpf_skb_cgroup_id(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return the cgroup v2 id of the socket associated with the \fIskb\fP\&.
+This is roughly similar to the \fBbpf_get_cgroup_classid\fP()
+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.
+.sp
+This helper can be used on TC egress path, but not on ingress,
+and is available only if the kernel was compiled with the
+\fBCONFIG_SOCK_CGROUP_DATA\fP configuration option.
+.TP
+.B Return
+The id is returned or 0 in case the id could not be retrieved.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_current_cgroup_id(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the current cgroup id based on the cgroup within which
+the current task is running.
+.TP
+.B Return
+A 64\-bit integer containing the current cgroup id based
+on the cgroup within which the current task is running.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_get_local_storage(void *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the pointer to the local storage area.
+The type and the size of the local storage is defined
+by the \fImap\fP argument.
+The \fIflags\fP meaning is specific for each map type,
+and has to be 0 for cgroup local storage.
+.sp
+Depending on the BPF program type, a local storage area
+can be shared between multiple instances of the BPF program,
+running simultaneously.
+.sp
+A user should care about the synchronization by himself.
+For example, by using the \fBBPF_ATOMIC\fP instructions to alter
+the shared data.
+.TP
+.B Return
+A pointer to the local storage area.
+.UNINDENT
+.TP
+.B \fBlong bpf_sk_select_reuseport(struct sk_reuseport_md *\fP\fIreuse\fP\fB, struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIkey\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Select a \fBSO_REUSEPORT\fP socket from a
+\fBBPF_MAP_TYPE_REUSEPORT_SOCKARRAY\fP \fImap\fP\&.
+It checks the selected socket is matching the incoming
+request in the socket buffer.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu64 bpf_skb_ancestor_cgroup_id(struct sk_buff *\fP\fIskb\fP\fB, int\fP \fIancestor_level\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return id of cgroup v2 that is ancestor of cgroup associated
+with the \fIskb\fP at the \fIancestor_level\fP\&.  The root cgroup is at
+\fIancestor_level\fP zero and each step down the hierarchy
+increments the level. If \fIancestor_level\fP == level of cgroup
+associated with \fIskb\fP, then return value will be same as that
+of \fBbpf_skb_cgroup_id\fP().
+.sp
+The helper is useful to implement policies based on cgroups
+that are upper in hierarchy than immediate cgroup associated
+with \fIskb\fP\&.
+.sp
+The format of returned id and helper limitations are same as in
+\fBbpf_skb_cgroup_id\fP().
+.TP
+.B Return
+The id is returned or 0 in case the id could not be retrieved.
+.UNINDENT
+.TP
+.B \fBstruct bpf_sock *bpf_sk_lookup_tcp(void *\fP\fIctx\fP\fB, struct bpf_sock_tuple *\fP\fItuple\fP\fB, u32\fP \fItuple_size\fP\fB, u64\fP \fInetns\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Look for TCP socket matching \fItuple\fP, optionally in a child
+network namespace \fInetns\fP\&. The return value must be checked,
+and if non\-\fBNULL\fP, released via \fBbpf_sk_release\fP().
+.sp
+The \fIctx\fP 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.
+.sp
+\fItuple_size\fP must be one of:
+.INDENT 7.0
+.TP
+.B \fBsizeof\fP(\fItuple\fP\fB\->ipv4\fP)
+Look for an IPv4 socket.
+.TP
+.B \fBsizeof\fP(\fItuple\fP\fB\->ipv6\fP)
+Look for an IPv6 socket.
+.UNINDENT
+.sp
+If the \fInetns\fP is a negative signed 32\-bit integer, then the
+socket lookup table in the netns associated with the \fIctx\fP
+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 \fInetns\fP 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 \fIctx\fP\&. \fInetns\fP values beyond the
+range of 32\-bit integers are reserved for future use.
+.sp
+All values for \fIflags\fP are reserved for future usage, and must
+be left at zero.
+.sp
+This helper is available only if the kernel was compiled with
+\fBCONFIG_NET\fP configuration option.
+.TP
+.B Return
+Pointer to \fBstruct bpf_sock\fP, or \fBNULL\fP in case of failure.
+For sockets with reuseport option, the \fBstruct bpf_sock\fP
+result is from \fIreuse\fP\fB\->socks\fP[] using the hash of the
+tuple.
+.UNINDENT
+.TP
+.B \fBstruct bpf_sock *bpf_sk_lookup_udp(void *\fP\fIctx\fP\fB, struct bpf_sock_tuple *\fP\fItuple\fP\fB, u32\fP \fItuple_size\fP\fB, u64\fP \fInetns\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Look for UDP socket matching \fItuple\fP, optionally in a child
+network namespace \fInetns\fP\&. The return value must be checked,
+and if non\-\fBNULL\fP, released via \fBbpf_sk_release\fP().
+.sp
+The \fIctx\fP 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.
+.sp
+\fItuple_size\fP must be one of:
+.INDENT 7.0
+.TP
+.B \fBsizeof\fP(\fItuple\fP\fB\->ipv4\fP)
+Look for an IPv4 socket.
+.TP
+.B \fBsizeof\fP(\fItuple\fP\fB\->ipv6\fP)
+Look for an IPv6 socket.
+.UNINDENT
+.sp
+If the \fInetns\fP is a negative signed 32\-bit integer, then the
+socket lookup table in the netns associated with the \fIctx\fP
+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 \fInetns\fP 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 \fIctx\fP\&. \fInetns\fP values beyond the
+range of 32\-bit integers are reserved for future use.
+.sp
+All values for \fIflags\fP are reserved for future usage, and must
+be left at zero.
+.sp
+This helper is available only if the kernel was compiled with
+\fBCONFIG_NET\fP configuration option.
+.TP
+.B Return
+Pointer to \fBstruct bpf_sock\fP, or \fBNULL\fP in case of failure.
+For sockets with reuseport option, the \fBstruct bpf_sock\fP
+result is from \fIreuse\fP\fB\->socks\fP[] using the hash of the
+tuple.
+.UNINDENT
+.TP
+.B \fBlong bpf_sk_release(void *\fP\fIsock\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Release the reference held by \fIsock\fP\&. \fIsock\fP must be a
+non\-\fBNULL\fP pointer that was returned from
+\fBbpf_sk_lookup_xxx\fP().
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_map_push_elem(struct bpf_map *\fP\fImap\fP\fB, const void *\fP\fIvalue\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Push an element \fIvalue\fP in \fImap\fP\&. \fIflags\fP is one of:
+.INDENT 7.0
+.TP
+.B \fBBPF_EXIST\fP
+If the queue/stack is full, the oldest element is
+removed to make room for this.
+.UNINDENT
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_map_pop_elem(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIvalue\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Pop an element from \fImap\fP\&.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_map_peek_elem(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIvalue\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get an element from \fImap\fP without removing it.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_msg_push_data(struct sk_msg_buff *\fP\fImsg\fP\fB, u32\fP \fIstart\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For socket policies, insert \fIlen\fP bytes into \fImsg\fP at offset
+\fIstart\fP\&.
+.sp
+If a program of type \fBBPF_PROG_TYPE_SK_MSG\fP is run on a
+\fImsg\fP it may want to insert metadata or options into the \fImsg\fP\&.
+This can later be read and used by any of the lower layer BPF
+hooks.
+.sp
+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.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_msg_pop_data(struct sk_msg_buff *\fP\fImsg\fP\fB, u32\fP \fIstart\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Will remove \fIlen\fP bytes from a \fImsg\fP starting at byte \fIstart\fP\&.
+This may result in \fBENOMEM\fP 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 \fIstart\fP byte not being valid part of \fImsg\fP
+payload and/or \fIpop\fP value being to large.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_rc_pointer_rel(void *\fP\fIctx\fP\fB, s32\fP \fIrel_x\fP\fB, s32\fP \fIrel_y\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is used in programs implementing IR decoding, to
+report a successfully decoded pointer movement.
+.sp
+The \fIctx\fP should point to the lirc sample as passed into
+the program.
+.sp
+This helper is only available is the kernel was compiled with
+the \fBCONFIG_BPF_LIRC_MODE2\fP configuration option set to
+\(dq\fBy\fP\(dq.
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBlong bpf_spin_lock(struct bpf_spin_lock *\fP\fIlock\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Acquire a spinlock represented by the pointer \fIlock\fP, 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
+\fBbpf_spin_unlock\fP(\fIlock\fP).
+.sp
+Spinlocks in BPF programs come with a number of restrictions
+and constraints:
+.INDENT 7.0
+.IP \(bu 2
+\fBbpf_spin_lock\fP objects are only allowed inside maps of
+types \fBBPF_MAP_TYPE_HASH\fP and \fBBPF_MAP_TYPE_ARRAY\fP (this
+list could be extended in the future).
+.IP \(bu 2
+BTF description of the map is mandatory.
+.IP \(bu 2
+The BPF program can take ONE lock at a time, since taking two
+or more could cause dead locks.
+.IP \(bu 2
+Only one \fBstruct bpf_spin_lock\fP is allowed per map element.
+.IP \(bu 2
+When the lock is taken, calls (either BPF to BPF or helpers)
+are not allowed.
+.IP \(bu 2
+The \fBBPF_LD_ABS\fP and \fBBPF_LD_IND\fP instructions are not
+allowed inside a spinlock\-ed region.
+.IP \(bu 2
+The BPF program MUST call \fBbpf_spin_unlock\fP() to release
+the lock, on all execution paths, before it returns.
+.IP \(bu 2
+The BPF program can access \fBstruct bpf_spin_lock\fP only via
+the \fBbpf_spin_lock\fP() and \fBbpf_spin_unlock\fP()
+helpers. Loading or storing data into the \fBstruct
+bpf_spin_lock\fP \fIlock\fP\fB;\fP field of a map is not allowed.
+.IP \(bu 2
+To use the \fBbpf_spin_lock\fP() helper, the BTF description
+of the map value must be a struct and have \fBstruct
+bpf_spin_lock\fP \fIanyname\fP\fB;\fP field at the top level.
+Nested lock inside another struct is not allowed.
+.IP \(bu 2
+The \fBstruct bpf_spin_lock\fP \fIlock\fP field in a map value must
+be aligned on a multiple of 4 bytes in that value.
+.IP \(bu 2
+Syscall with command \fBBPF_MAP_LOOKUP_ELEM\fP does not copy
+the \fBbpf_spin_lock\fP field to user space.
+.IP \(bu 2
+Syscall with command \fBBPF_MAP_UPDATE_ELEM\fP, or update from
+a BPF program, do not update the \fBbpf_spin_lock\fP field.
+.IP \(bu 2
+\fBbpf_spin_lock\fP cannot be on the stack or inside a
+networking packet (it can only be inside of a map values).
+.IP \(bu 2
+\fBbpf_spin_lock\fP is available to root only.
+.IP \(bu 2
+Tracing programs and socket filter programs cannot use
+\fBbpf_spin_lock\fP() due to insufficient preemption checks
+(but this may change in the future).
+.IP \(bu 2
+\fBbpf_spin_lock\fP is not allowed in inner maps of map\-in\-map.
+.UNINDENT
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBlong bpf_spin_unlock(struct bpf_spin_lock *\fP\fIlock\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Release the \fIlock\fP previously locked by a call to
+\fBbpf_spin_lock\fP(\fIlock\fP).
+.TP
+.B Return
+0
+.UNINDENT
+.TP
+.B \fBstruct bpf_sock *bpf_sk_fullsock(struct bpf_sock *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper gets a \fBstruct bpf_sock\fP pointer such
+that all the fields in this \fBbpf_sock\fP can be accessed.
+.TP
+.B Return
+A \fBstruct bpf_sock\fP pointer on success, or \fBNULL\fP in
+case of failure.
+.UNINDENT
+.TP
+.B \fBstruct bpf_tcp_sock *bpf_tcp_sock(struct bpf_sock *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper gets a \fBstruct bpf_tcp_sock\fP pointer from a
+\fBstruct bpf_sock\fP pointer.
+.TP
+.B Return
+A \fBstruct bpf_tcp_sock\fP pointer on success, or \fBNULL\fP in
+case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_ecn_set_ce(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Set ECN (Explicit Congestion Notification) field of IP header
+to \fBCE\fP (Congestion Encountered) if current value is \fBECT\fP
+(ECN Capable Transport). Otherwise, do nothing. Works with IPv6
+and IPv4.
+.TP
+.B Return
+1 if the \fBCE\fP flag is set (either by the current helper call
+or because it was already present), 0 if it is not set.
+.UNINDENT
+.TP
+.B \fBstruct bpf_sock *bpf_get_listener_sock(struct bpf_sock *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return a \fBstruct bpf_sock\fP pointer in \fBTCP_LISTEN\fP state.
+\fBbpf_sk_release\fP() is unnecessary and not allowed.
+.TP
+.B Return
+A \fBstruct bpf_sock\fP pointer on success, or \fBNULL\fP in
+case of failure.
+.UNINDENT
+.TP
+.B \fBstruct bpf_sock *bpf_skc_lookup_tcp(void *\fP\fIctx\fP\fB, struct bpf_sock_tuple *\fP\fItuple\fP\fB, u32\fP \fItuple_size\fP\fB, u64\fP \fInetns\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Look for TCP socket matching \fItuple\fP, optionally in a child
+network namespace \fInetns\fP\&. The return value must be checked,
+and if non\-\fBNULL\fP, released via \fBbpf_sk_release\fP().
+.sp
+This function is identical to \fBbpf_sk_lookup_tcp\fP(), except
+that it also returns timewait or request sockets. Use
+\fBbpf_sk_fullsock\fP() or \fBbpf_tcp_sock\fP() to access the
+full structure.
+.sp
+This helper is available only if the kernel was compiled with
+\fBCONFIG_NET\fP configuration option.
+.TP
+.B Return
+Pointer to \fBstruct bpf_sock\fP, or \fBNULL\fP in case of failure.
+For sockets with reuseport option, the \fBstruct bpf_sock\fP
+result is from \fIreuse\fP\fB\->socks\fP[] using the hash of the
+tuple.
+.UNINDENT
+.TP
+.B \fBlong bpf_tcp_check_syncookie(void *\fP\fIsk\fP\fB, void *\fP\fIiph\fP\fB, u32\fP \fIiph_len\fP\fB, struct tcphdr *\fP\fIth\fP\fB, u32\fP \fIth_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Check whether \fIiph\fP and \fIth\fP contain a valid SYN cookie ACK for
+the listening socket in \fIsk\fP\&.
+.sp
+\fIiph\fP points to the start of the IPv4 or IPv6 header, while
+\fIiph_len\fP contains \fBsizeof\fP(\fBstruct iphdr\fP) or
+\fBsizeof\fP(\fBstruct ipv6hdr\fP).
+.sp
+\fIth\fP points to the start of the TCP header, while \fIth_len\fP
+contains the length of the TCP header (at least
+\fBsizeof\fP(\fBstruct tcphdr\fP)).
+.TP
+.B Return
+0 if \fIiph\fP and \fIth\fP are a valid SYN cookie ACK, or a negative
+error otherwise.
+.UNINDENT
+.TP
+.B \fBlong bpf_sysctl_get_name(struct bpf_sysctl *\fP\fIctx\fP\fB, char *\fP\fIbuf\fP\fB, size_t\fP \fIbuf_len\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get name of sysctl in /proc/sys/ and copy it into provided by
+program buffer \fIbuf\fP of size \fIbuf_len\fP\&.
+.sp
+The buffer is always NUL terminated, unless it\(aqs zero\-sized.
+.sp
+If \fIflags\fP is zero, full name (e.g. \(dqnet/ipv4/tcp_mem\(dq) is
+copied. Use \fBBPF_F_SYSCTL_BASE_NAME\fP flag to copy base name
+only (e.g. \(dqtcp_mem\(dq).
+.TP
+.B Return
+Number of character copied (not including the trailing NUL).
+.sp
+\fB\-E2BIG\fP if the buffer wasn\(aqt big enough (\fIbuf\fP will contain
+truncated name in this case).
+.UNINDENT
+.TP
+.B \fBlong bpf_sysctl_get_current_value(struct bpf_sysctl *\fP\fIctx\fP\fB, char *\fP\fIbuf\fP\fB, size_t\fP \fIbuf_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B 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 \fIbuf\fP of size \fIbuf_len\fP\&.
+.sp
+The whole value is copied, no matter what file position user
+space issued e.g. sys_read at.
+.sp
+The buffer is always NUL terminated, unless it\(aqs zero\-sized.
+.TP
+.B Return
+Number of character copied (not including the trailing NUL).
+.sp
+\fB\-E2BIG\fP if the buffer wasn\(aqt big enough (\fIbuf\fP will contain
+truncated name in this case).
+.sp
+\fB\-EINVAL\fP if current value was unavailable, e.g. because
+sysctl is uninitialized and read returns \-EIO for it.
+.UNINDENT
+.TP
+.B \fBlong bpf_sysctl_get_new_value(struct bpf_sysctl *\fP\fIctx\fP\fB, char *\fP\fIbuf\fP\fB, size_t\fP \fIbuf_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B 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 \fIbuf\fP of size \fIbuf_len\fP\&.
+.sp
+User space may write new value at file position > 0.
+.sp
+The buffer is always NUL terminated, unless it\(aqs zero\-sized.
+.TP
+.B Return
+Number of character copied (not including the trailing NUL).
+.sp
+\fB\-E2BIG\fP if the buffer wasn\(aqt big enough (\fIbuf\fP will contain
+truncated name in this case).
+.sp
+\fB\-EINVAL\fP if sysctl is being read.
+.UNINDENT
+.TP
+.B \fBlong bpf_sysctl_set_new_value(struct bpf_sysctl *\fP\fIctx\fP\fB, const char *\fP\fIbuf\fP\fB, size_t\fP \fIbuf_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Override new value being written by user space to sysctl with
+value provided by program in buffer \fIbuf\fP of size \fIbuf_len\fP\&.
+.sp
+\fIbuf\fP should contain a string in same form as provided by user
+space on sysctl write.
+.sp
+User space may write new value at file position > 0. To override
+the whole sysctl value file position should be set to zero.
+.TP
+.B Return
+0 on success.
+.sp
+\fB\-E2BIG\fP if the \fIbuf_len\fP is too big.
+.sp
+\fB\-EINVAL\fP if sysctl is being read.
+.UNINDENT
+.TP
+.B \fBlong bpf_strtol(const char *\fP\fIbuf\fP\fB, size_t\fP \fIbuf_len\fP\fB, u64\fP \fIflags\fP\fB, long *\fP\fIres\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Convert the initial part of the string from buffer \fIbuf\fP of
+size \fIbuf_len\fP to a long integer according to the given base
+and save the result in \fIres\fP\&.
+.sp
+The string may begin with an arbitrary amount of white space
+(as determined by \fBisspace\fP(3)) followed by a single
+optional \(aq\fB\-\fP\(aq sign.
+.sp
+Five least significant bits of \fIflags\fP encode base, other bits
+are currently unused.
+.sp
+Base must be either 8, 10, 16 or 0 to detect it automatically
+similar to user space \fBstrtol\fP(3).
+.TP
+.B Return
+Number of characters consumed on success. Must be positive but
+no more than \fIbuf_len\fP\&.
+.sp
+\fB\-EINVAL\fP if no valid digits were found or unsupported base
+was provided.
+.sp
+\fB\-ERANGE\fP if resulting value was out of range.
+.UNINDENT
+.TP
+.B \fBlong bpf_strtoul(const char *\fP\fIbuf\fP\fB, size_t\fP \fIbuf_len\fP\fB, u64\fP \fIflags\fP\fB, unsigned long *\fP\fIres\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Convert the initial part of the string from buffer \fIbuf\fP of
+size \fIbuf_len\fP to an unsigned long integer according to the
+given base and save the result in \fIres\fP\&.
+.sp
+The string may begin with an arbitrary amount of white space
+(as determined by \fBisspace\fP(3)).
+.sp
+Five least significant bits of \fIflags\fP encode base, other bits
+are currently unused.
+.sp
+Base must be either 8, 10, 16 or 0 to detect it automatically
+similar to user space \fBstrtoul\fP(3).
+.TP
+.B Return
+Number of characters consumed on success. Must be positive but
+no more than \fIbuf_len\fP\&.
+.sp
+\fB\-EINVAL\fP if no valid digits were found or unsupported base
+was provided.
+.sp
+\fB\-ERANGE\fP if resulting value was out of range.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_sk_storage_get(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIsk\fP\fB, void *\fP\fIvalue\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get a bpf\-local\-storage from a \fIsk\fP\&.
+.sp
+Logically, it could be thought of getting the value from
+a \fImap\fP with \fIsk\fP as the \fBkey\fP\&.  From this
+perspective,  the usage is not much different from
+\fBbpf_map_lookup_elem\fP(\fImap\fP, \fB&\fP\fIsk\fP) except this
+helper enforces the key must be a full socket and the map must
+be a \fBBPF_MAP_TYPE_SK_STORAGE\fP also.
+.sp
+Underneath, the value is stored locally at \fIsk\fP instead of
+the \fImap\fP\&.  The \fImap\fP is used as the bpf\-local\-storage
+\(dqtype\(dq. The bpf\-local\-storage \(dqtype\(dq (i.e. the \fImap\fP) is
+searched against all bpf\-local\-storages residing at \fIsk\fP\&.
+.sp
+\fIsk\fP is a kernel \fBstruct sock\fP pointer for LSM program.
+\fIsk\fP is a \fBstruct bpf_sock\fP pointer for other program types.
+.sp
+An optional \fIflags\fP (\fBBPF_SK_STORAGE_GET_F_CREATE\fP) can be
+used such that a new bpf\-local\-storage will be
+created if one does not exist.  \fIvalue\fP can be used
+together with \fBBPF_SK_STORAGE_GET_F_CREATE\fP to specify
+the initial value of a bpf\-local\-storage.  If \fIvalue\fP is
+\fBNULL\fP, the new bpf\-local\-storage will be zero initialized.
+.TP
+.B Return
+A bpf\-local\-storage pointer is returned on success.
+.sp
+\fBNULL\fP if not found or there was an error in adding
+a new bpf\-local\-storage.
+.UNINDENT
+.TP
+.B \fBlong bpf_sk_storage_delete(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Delete a bpf\-local\-storage from a \fIsk\fP\&.
+.TP
+.B Return
+0 on success.
+.sp
+\fB\-ENOENT\fP if the bpf\-local\-storage cannot be found.
+\fB\-EINVAL\fP if sk is not a fullsock (e.g. a request_sock).
+.UNINDENT
+.TP
+.B \fBlong bpf_send_signal(u32\fP \fIsig\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Send signal \fIsig\fP to the process of the current task.
+The signal may be delivered to any of this process\(aqs threads.
+.TP
+.B Return
+0 on success or successfully queued.
+.sp
+\fB\-EBUSY\fP if work queue under nmi is full.
+.sp
+\fB\-EINVAL\fP if \fIsig\fP is invalid.
+.sp
+\fB\-EPERM\fP if no permission to send the \fIsig\fP\&.
+.sp
+\fB\-EAGAIN\fP if bpf program can try again.
+.UNINDENT
+.TP
+.B \fBs64 bpf_tcp_gen_syncookie(void *\fP\fIsk\fP\fB, void *\fP\fIiph\fP\fB, u32\fP \fIiph_len\fP\fB, struct tcphdr *\fP\fIth\fP\fB, u32\fP \fIth_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Try to issue a SYN cookie for the packet with corresponding
+IP/TCP headers, \fIiph\fP and \fIth\fP, on the listening socket in \fIsk\fP\&.
+.sp
+\fIiph\fP points to the start of the IPv4 or IPv6 header, while
+\fIiph_len\fP contains \fBsizeof\fP(\fBstruct iphdr\fP) or
+\fBsizeof\fP(\fBstruct ipv6hdr\fP).
+.sp
+\fIth\fP points to the start of the TCP header, while \fIth_len\fP
+contains the length of the TCP header with options (at least
+\fBsizeof\fP(\fBstruct tcphdr\fP)).
+.TP
+.B 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.
+.sp
+On failure, the returned value is one of the following:
+.sp
+\fB\-EINVAL\fP SYN cookie cannot be issued due to error
+.sp
+\fB\-ENOENT\fP SYN cookie should not be issued (no SYN flood)
+.sp
+\fB\-EOPNOTSUPP\fP kernel configuration does not enable SYN cookies
+.sp
+\fB\-EPROTONOSUPPORT\fP IP packet version is not 4 or 6
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_output(void *\fP\fIctx\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB, void *\fP\fIdata\fP\fB, u64\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Write raw \fIdata\fP blob into a special BPF perf event held by
+\fImap\fP of type \fBBPF_MAP_TYPE_PERF_EVENT_ARRAY\fP\&. This perf
+event must have the following attributes: \fBPERF_SAMPLE_RAW\fP
+as \fBsample_type\fP, \fBPERF_TYPE_SOFTWARE\fP as \fBtype\fP, and
+\fBPERF_COUNT_SW_BPF_OUTPUT\fP as \fBconfig\fP\&.
+.sp
+The \fIflags\fP are used to indicate the index in \fImap\fP for which
+the value must be put, masked with \fBBPF_F_INDEX_MASK\fP\&.
+Alternatively, \fIflags\fP can be set to \fBBPF_F_CURRENT_CPU\fP
+to indicate that the index of the current CPU core should be
+used.
+.sp
+The value to write, of \fIsize\fP, is passed through eBPF stack and
+pointed by \fIdata\fP\&.
+.sp
+\fIctx\fP is a pointer to in\-kernel struct sk_buff.
+.sp
+This helper is similar to \fBbpf_perf_event_output\fP() but
+restricted to raw_tracepoint bpf programs.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_probe_read_user(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIunsafe_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Safely attempt to read \fIsize\fP bytes from user space address
+\fIunsafe_ptr\fP and store the data in \fIdst\fP\&.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_probe_read_kernel(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIunsafe_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Safely attempt to read \fIsize\fP bytes from kernel space address
+\fIunsafe_ptr\fP and store the data in \fIdst\fP\&.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_probe_read_user_str(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIunsafe_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Copy a NUL terminated string from an unsafe user address
+\fIunsafe_ptr\fP to \fIdst\fP\&. The \fIsize\fP should include the
+terminating NUL byte. In case the string length is smaller than
+\fIsize\fP, the target is not padded with further NUL bytes. If the
+string length is larger than \fIsize\fP, just \fIsize\fP\-1 bytes are
+copied and the last byte is set to NUL.
+.sp
+On success, returns the number of bytes that were written,
+including the terminal NUL. This makes this helper useful in
+tracing programs for reading strings, and more importantly to
+get its length at runtime. See the following snippet:
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+SEC(\(dqkprobe/sys_open\(dq)
+void bpf_sys_open(struct pt_regs *ctx)
+{
+        char buf[PATHLEN]; // PATHLEN is defined to 256
+        int res;
+
+        res = bpf_probe_read_user_str(buf, sizeof(buf),
+                                      ctx\->di);
+
+        // Consume buf, for example push it to
+        // userspace via bpf_perf_event_output(); we
+        // can use res (the string length) as event
+        // size, after checking its boundaries.
+}
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.sp
+In comparison, using \fBbpf_probe_read_user\fP() 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.
+.sp
+Another useful use case is when parsing individual process
+arguments or individual environment variables navigating
+\fIcurrent\fP\fB\->mm\->arg_start\fP and \fIcurrent\fP\fB\->mm\->env_start\fP: using this helper and the return value,
+one can quickly iterate at the right offset of the memory area.
+.TP
+.B Return
+On success, the strictly positive length of the output string,
+including the trailing NUL character. On error, a negative
+value.
+.UNINDENT
+.TP
+.B \fBlong bpf_probe_read_kernel_str(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIunsafe_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Copy a NUL terminated string from an unsafe kernel address \fIunsafe_ptr\fP
+to \fIdst\fP\&. Same semantics as with \fBbpf_probe_read_user_str\fP() apply.
+.TP
+.B Return
+On success, the strictly positive length of the string, including
+the trailing NUL character. On error, a negative value.
+.UNINDENT
+.TP
+.B \fBlong bpf_tcp_send_ack(void *\fP\fItp\fP\fB, u32\fP \fIrcv_nxt\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Send out a tcp\-ack. \fItp\fP is the in\-kernel struct \fBtcp_sock\fP\&.
+\fIrcv_nxt\fP is the ack_seq to be sent out.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_send_signal_thread(u32\fP \fIsig\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Send signal \fIsig\fP to the thread corresponding to the current task.
+.TP
+.B Return
+0 on success or successfully queued.
+.sp
+\fB\-EBUSY\fP if work queue under nmi is full.
+.sp
+\fB\-EINVAL\fP if \fIsig\fP is invalid.
+.sp
+\fB\-EPERM\fP if no permission to send the \fIsig\fP\&.
+.sp
+\fB\-EAGAIN\fP if bpf program can try again.
+.UNINDENT
+.TP
+.B \fBu64 bpf_jiffies64(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Obtain the 64bit jiffies
+.TP
+.B Return
+The 64 bit jiffies
+.UNINDENT
+.TP
+.B \fBlong bpf_read_branch_records(struct bpf_perf_event_data *\fP\fIctx\fP\fB, void *\fP\fIbuf\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For an eBPF program attached to a perf event, retrieve the
+branch records (\fBstruct perf_branch_entry\fP) associated to \fIctx\fP
+and store it in the buffer pointed by \fIbuf\fP up to size
+\fIsize\fP bytes.
+.TP
+.B Return
+On success, number of bytes written to \fIbuf\fP\&. On error, a
+negative value.
+.sp
+The \fIflags\fP can be set to \fBBPF_F_GET_BRANCH_RECORDS_SIZE\fP to
+instead return the number of bytes required to store all the
+branch entries. If this flag is set, \fIbuf\fP may be NULL.
+.sp
+\fB\-EINVAL\fP if arguments invalid or \fBsize\fP not a multiple
+of \fBsizeof\fP(\fBstruct perf_branch_entry\fP).
+.sp
+\fB\-ENOENT\fP if architecture does not support branch records.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_ns_current_pid_tgid(u64\fP \fIdev\fP\fB, u64\fP \fIino\fP\fB, struct bpf_pidns_info *\fP\fInsdata\fP\fB, u32\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Returns 0 on success, values for \fIpid\fP and \fItgid\fP as seen from the current
+\fInamespace\fP will be returned in \fInsdata\fP\&.
+.TP
+.B Return
+0 on success, or one of the following in case of failure:
+.sp
+\fB\-EINVAL\fP if dev and inum supplied don\(aqt match dev_t and inode number
+with nsfs of current task, or if dev conversion to dev_t lost high bits.
+.sp
+\fB\-ENOENT\fP if pidns does not exists for the current task.
+.UNINDENT
+.TP
+.B \fBlong bpf_xdp_output(void *\fP\fIctx\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB, void *\fP\fIdata\fP\fB, u64\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Write raw \fIdata\fP blob into a special BPF perf event held by
+\fImap\fP of type \fBBPF_MAP_TYPE_PERF_EVENT_ARRAY\fP\&. This perf
+event must have the following attributes: \fBPERF_SAMPLE_RAW\fP
+as \fBsample_type\fP, \fBPERF_TYPE_SOFTWARE\fP as \fBtype\fP, and
+\fBPERF_COUNT_SW_BPF_OUTPUT\fP as \fBconfig\fP\&.
+.sp
+The \fIflags\fP are used to indicate the index in \fImap\fP for which
+the value must be put, masked with \fBBPF_F_INDEX_MASK\fP\&.
+Alternatively, \fIflags\fP can be set to \fBBPF_F_CURRENT_CPU\fP
+to indicate that the index of the current CPU core should be
+used.
+.sp
+The value to write, of \fIsize\fP, is passed through eBPF stack and
+pointed by \fIdata\fP\&.
+.sp
+\fIctx\fP is a pointer to in\-kernel struct xdp_buff.
+.sp
+This helper is similar to \fBbpf_perf_eventoutput\fP() but
+restricted to raw_tracepoint bpf programs.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_netns_cookie(void *\fP\fIctx\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Retrieve the cookie (generated by the kernel) of the network
+namespace the input \fIctx\fP is associated with. The network
+namespace cookie remains stable for its lifetime and provides
+a global identifier that can be assumed unique. If \fIctx\fP is
+NULL, then the helper returns the cookie for the initial
+network namespace. The cookie itself is very similar to that
+of \fBbpf_get_socket_cookie\fP() helper, but for network
+namespaces instead of sockets.
+.TP
+.B Return
+A 8\-byte long opaque number.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_current_ancestor_cgroup_id(int\fP \fIancestor_level\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return id of cgroup v2 that is ancestor of the cgroup associated
+with the current task at the \fIancestor_level\fP\&. The root cgroup
+is at \fIancestor_level\fP zero and each step down the hierarchy
+increments the level. If \fIancestor_level\fP == level of cgroup
+associated with the current task, then return value will be the
+same as that of \fBbpf_get_current_cgroup_id\fP().
+.sp
+The helper is useful to implement policies based on cgroups
+that are upper in hierarchy than immediate cgroup associated
+with the current task.
+.sp
+The format of returned id and helper limitations are same as in
+\fBbpf_get_current_cgroup_id\fP().
+.TP
+.B Return
+The id is returned or 0 in case the id could not be retrieved.
+.UNINDENT
+.TP
+.B \fBlong bpf_sk_assign(struct sk_buff *\fP\fIskb\fP\fB, void *\fP\fIsk\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Helper is overloaded depending on BPF program type. This
+description applies to \fBBPF_PROG_TYPE_SCHED_CLS\fP and
+\fBBPF_PROG_TYPE_SCHED_ACT\fP programs.
+.sp
+Assign the \fIsk\fP to the \fIskb\fP\&. When combined with appropriate
+routing configuration to receive the packet towards the socket,
+will cause \fIskb\fP to be delivered to the specified socket.
+Subsequent redirection of \fIskb\fP via  \fBbpf_redirect\fP(),
+\fBbpf_clone_redirect\fP() or other methods outside of BPF may
+interfere with successful delivery to the socket.
+.sp
+This operation is only valid from TC ingress path.
+.sp
+The \fIflags\fP argument must be zero.
+.TP
+.B Return
+0 on success, or a negative error in case of failure:
+.sp
+\fB\-EINVAL\fP if specified \fIflags\fP are not supported.
+.sp
+\fB\-ENOENT\fP if the socket is unavailable for assignment.
+.sp
+\fB\-ENETUNREACH\fP if the socket is unreachable (wrong netns).
+.sp
+\fB\-EOPNOTSUPP\fP if the operation is not supported, for example
+a call from outside of TC ingress.
+.sp
+\fB\-ESOCKTNOSUPPORT\fP if the socket type is not supported
+(reuseport).
+.UNINDENT
+.TP
+.B \fBlong bpf_sk_assign(struct bpf_sk_lookup *\fP\fIctx\fP\fB, struct bpf_sock *\fP\fIsk\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Helper is overloaded depending on BPF program type. This
+description applies to \fBBPF_PROG_TYPE_SK_LOOKUP\fP programs.
+.sp
+Select the \fIsk\fP as a result of a socket lookup.
+.sp
+For the operation to succeed passed socket must be compatible
+with the packet description provided by the \fIctx\fP object.
+.sp
+L4 protocol (\fBIPPROTO_TCP\fP or \fBIPPROTO_UDP\fP) must
+be an exact match. While IP family (\fBAF_INET\fP or
+\fBAF_INET6\fP) must be compatible, that is IPv6 sockets
+that are not v6\-only can be selected for IPv4 packets.
+.sp
+Only TCP listeners and UDP unconnected sockets can be
+selected. \fIsk\fP can also be NULL to reset any previous
+selection.
+.sp
+\fIflags\fP argument can combination of following values:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_SK_LOOKUP_F_REPLACE\fP to override the previous
+socket selection, potentially done by a BPF program
+that ran before us.
+.IP \(bu 2
+\fBBPF_SK_LOOKUP_F_NO_REUSEPORT\fP to skip
+load\-balancing within reuseport group for the socket
+being selected.
+.UNINDENT
+.sp
+On success \fIctx\->sk\fP will point to the selected socket.
+.TP
+.B Return
+0 on success, or a negative errno in case of failure.
+.INDENT 7.0
+.IP \(bu 2
+\fB\-EAFNOSUPPORT\fP if socket family (\fIsk\->family\fP) is
+not compatible with packet family (\fIctx\->family\fP).
+.IP \(bu 2
+\fB\-EEXIST\fP if socket has been already selected,
+potentially by another program, and
+\fBBPF_SK_LOOKUP_F_REPLACE\fP flag was not specified.
+.IP \(bu 2
+\fB\-EINVAL\fP if unsupported flags were specified.
+.IP \(bu 2
+\fB\-EPROTOTYPE\fP if socket L4 protocol
+(\fIsk\->protocol\fP) doesn\(aqt match packet protocol
+(\fIctx\->protocol\fP).
+.IP \(bu 2
+\fB\-ESOCKTNOSUPPORT\fP if socket is not in allowed
+state (TCP listening or UDP unconnected).
+.UNINDENT
+.UNINDENT
+.TP
+.B \fBu64 bpf_ktime_get_boot_ns(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return the time elapsed since system boot, in nanoseconds.
+Does include the time the system was suspended.
+See: \fBclock_gettime\fP(\fBCLOCK_BOOTTIME\fP)
+.TP
+.B Return
+Current \fIktime\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_seq_printf(struct seq_file *\fP\fIm\fP\fB, const char *\fP\fIfmt\fP\fB, u32\fP \fIfmt_size\fP\fB, const void *\fP\fIdata\fP\fB, u32\fP \fIdata_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+\fBbpf_seq_printf\fP() uses seq_file \fBseq_printf\fP() to print
+out the format string.
+The \fIm\fP represents the seq_file. The \fIfmt\fP and \fIfmt_size\fP are for
+the format string itself. The \fIdata\fP and \fIdata_len\fP are format string
+arguments. The \fIdata\fP are a \fBu64\fP 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 \fIdata\fP array.
+The \fIdata_len\fP is the size of \fIdata\fP in bytes \- must be a multiple of 8.
+.sp
+Formats \fB%s\fP, \fB%p{i,I}{4,6}\fP 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 \fB%s\fP will be an empty string, and the ip
+address for \fB%p{i,I}{4,6}\fP will be 0. Not returning error to
+bpf program is consistent with what \fBbpf_trace_printk\fP() does for now.
+.TP
+.B Return
+0 on success, or a negative error in case of failure:
+.sp
+\fB\-EBUSY\fP if per\-CPU memory copy buffer is busy, can try again
+by returning 1 from bpf program.
+.sp
+\fB\-EINVAL\fP if arguments are invalid, or if \fIfmt\fP is invalid/unsupported.
+.sp
+\fB\-E2BIG\fP if \fIfmt\fP contains too many format specifiers.
+.sp
+\fB\-EOVERFLOW\fP if an overflow happened: The same object will be tried again.
+.UNINDENT
+.TP
+.B \fBlong bpf_seq_write(struct seq_file *\fP\fIm\fP\fB, const void *\fP\fIdata\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+\fBbpf_seq_write\fP() uses seq_file \fBseq_write\fP() to write the data.
+The \fIm\fP represents the seq_file. The \fIdata\fP and \fIlen\fP represent the
+data to write in bytes.
+.TP
+.B Return
+0 on success, or a negative error in case of failure:
+.sp
+\fB\-EOVERFLOW\fP if an overflow happened: The same object will be tried again.
+.UNINDENT
+.TP
+.B \fBu64 bpf_sk_cgroup_id(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return the cgroup v2 id of the socket \fIsk\fP\&.
+.sp
+\fIsk\fP must be a non\-\fBNULL\fP pointer to a socket, e.g. one
+returned from \fBbpf_sk_lookup_xxx\fP(),
+\fBbpf_sk_fullsock\fP(), etc. The format of returned id is
+same as in \fBbpf_skb_cgroup_id\fP().
+.sp
+This helper is available only if the kernel was compiled with
+the \fBCONFIG_SOCK_CGROUP_DATA\fP configuration option.
+.TP
+.B Return
+The id is returned or 0 in case the id could not be retrieved.
+.UNINDENT
+.TP
+.B \fBu64 bpf_sk_ancestor_cgroup_id(void *\fP\fIsk\fP\fB, int\fP \fIancestor_level\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return id of cgroup v2 that is ancestor of cgroup associated
+with the \fIsk\fP at the \fIancestor_level\fP\&.  The root cgroup is at
+\fIancestor_level\fP zero and each step down the hierarchy
+increments the level. If \fIancestor_level\fP == level of cgroup
+associated with \fIsk\fP, then return value will be same as that
+of \fBbpf_sk_cgroup_id\fP().
+.sp
+The helper is useful to implement policies based on cgroups
+that are upper in hierarchy than immediate cgroup associated
+with \fIsk\fP\&.
+.sp
+The format of returned id and helper limitations are same as in
+\fBbpf_sk_cgroup_id\fP().
+.TP
+.B Return
+The id is returned or 0 in case the id could not be retrieved.
+.UNINDENT
+.TP
+.B \fBlong bpf_ringbuf_output(void *\fP\fIringbuf\fP\fB, void *\fP\fIdata\fP\fB, u64\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Copy \fIsize\fP bytes from \fIdata\fP into a ring buffer \fIringbuf\fP\&.
+If \fBBPF_RB_NO_WAKEUP\fP is specified in \fIflags\fP, no notification
+of new data availability is sent.
+If \fBBPF_RB_FORCE_WAKEUP\fP is specified in \fIflags\fP, notification
+of new data availability is sent unconditionally.
+If \fB0\fP is specified in \fIflags\fP, an adaptive notification
+of new data availability is sent.
+.sp
+An adaptive notification is a notification sent whenever the user\-space
+process has caught up and consumed all available payloads. In case the user\-space
+process is still processing a previous payload, then no notification is needed
+as it will process the newly added payload automatically.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_ringbuf_reserve(void *\fP\fIringbuf\fP\fB, u64\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Reserve \fIsize\fP bytes of payload in a ring buffer \fIringbuf\fP\&.
+\fIflags\fP must be 0.
+.TP
+.B Return
+Valid pointer with \fIsize\fP bytes of memory available; NULL,
+otherwise.
+.UNINDENT
+.TP
+.B \fBvoid bpf_ringbuf_submit(void *\fP\fIdata\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Submit reserved ring buffer sample, pointed to by \fIdata\fP\&.
+If \fBBPF_RB_NO_WAKEUP\fP is specified in \fIflags\fP, no notification
+of new data availability is sent.
+If \fBBPF_RB_FORCE_WAKEUP\fP is specified in \fIflags\fP, notification
+of new data availability is sent unconditionally.
+If \fB0\fP is specified in \fIflags\fP, an adaptive notification
+of new data availability is sent.
+.sp
+See \(aqbpf_ringbuf_output()\(aq for the definition of adaptive notification.
+.TP
+.B Return
+Nothing. Always succeeds.
+.UNINDENT
+.TP
+.B \fBvoid bpf_ringbuf_discard(void *\fP\fIdata\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Discard reserved ring buffer sample, pointed to by \fIdata\fP\&.
+If \fBBPF_RB_NO_WAKEUP\fP is specified in \fIflags\fP, no notification
+of new data availability is sent.
+If \fBBPF_RB_FORCE_WAKEUP\fP is specified in \fIflags\fP, notification
+of new data availability is sent unconditionally.
+If \fB0\fP is specified in \fIflags\fP, an adaptive notification
+of new data availability is sent.
+.sp
+See \(aqbpf_ringbuf_output()\(aq for the definition of adaptive notification.
+.TP
+.B Return
+Nothing. Always succeeds.
+.UNINDENT
+.TP
+.B \fBu64 bpf_ringbuf_query(void *\fP\fIringbuf\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Query various characteristics of provided ring buffer. What
+exactly is queries is determined by \fIflags\fP:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_RB_AVAIL_DATA\fP: Amount of data not yet consumed.
+.IP \(bu 2
+\fBBPF_RB_RING_SIZE\fP: The size of ring buffer.
+.IP \(bu 2
+\fBBPF_RB_CONS_POS\fP: Consumer position (can wrap around).
+.IP \(bu 2
+\fBBPF_RB_PROD_POS\fP: Producer(s) position (can wrap around).
+.UNINDENT
+.sp
+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.
+.TP
+.B Return
+Requested value, or 0, if \fIflags\fP are not recognized.
+.UNINDENT
+.TP
+.B \fBlong bpf_csum_level(struct sk_buff *\fP\fIskb\fP\fB, u64\fP \fIlevel\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B 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 \fBbpf_skb_adjust_room\fP() helper with passing in
+\fBBPF_F_ADJ_ROOM_NO_CSUM_RESET\fP flag would require one call
+to \fBbpf_csum_level\fP() with \fBBPF_CSUM_LEVEL_DEC\fP since
+the UDP header is removed. Similarly, an encap of the latter
+into the former could be accompanied by a helper call to
+\fBbpf_csum_level\fP() with \fBBPF_CSUM_LEVEL_INC\fP if the
+skb is still intended to be processed in higher layers of the
+stack instead of just egressing at tc.
+.sp
+There are three supported level settings at this time:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_CSUM_LEVEL_INC\fP: Increases skb\->csum_level for skbs
+with CHECKSUM_UNNECESSARY.
+.IP \(bu 2
+\fBBPF_CSUM_LEVEL_DEC\fP: Decreases skb\->csum_level for skbs
+with CHECKSUM_UNNECESSARY.
+.IP \(bu 2
+\fBBPF_CSUM_LEVEL_RESET\fP: Resets skb\->csum_level to 0 and
+sets CHECKSUM_NONE to force checksum validation by the stack.
+.IP \(bu 2
+\fBBPF_CSUM_LEVEL_QUERY\fP: No\-op, returns the current
+skb\->csum_level.
+.UNINDENT
+.TP
+.B Return
+0 on success, or a negative error in case of failure. In the
+case of \fBBPF_CSUM_LEVEL_QUERY\fP, the current skb\->csum_level
+is returned or the error code \-EACCES in case the skb is not
+subject to CHECKSUM_UNNECESSARY.
+.UNINDENT
+.TP
+.B \fBstruct tcp6_sock *bpf_skc_to_tcp6_sock(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Dynamically cast a \fIsk\fP pointer to a \fItcp6_sock\fP pointer.
+.TP
+.B Return
+\fIsk\fP if casting is valid, or \fBNULL\fP otherwise.
+.UNINDENT
+.TP
+.B \fBstruct tcp_sock *bpf_skc_to_tcp_sock(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Dynamically cast a \fIsk\fP pointer to a \fItcp_sock\fP pointer.
+.TP
+.B Return
+\fIsk\fP if casting is valid, or \fBNULL\fP otherwise.
+.UNINDENT
+.TP
+.B \fBstruct tcp_timewait_sock *bpf_skc_to_tcp_timewait_sock(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Dynamically cast a \fIsk\fP pointer to a \fItcp_timewait_sock\fP pointer.
+.TP
+.B Return
+\fIsk\fP if casting is valid, or \fBNULL\fP otherwise.
+.UNINDENT
+.TP
+.B \fBstruct tcp_request_sock *bpf_skc_to_tcp_request_sock(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Dynamically cast a \fIsk\fP pointer to a \fItcp_request_sock\fP pointer.
+.TP
+.B Return
+\fIsk\fP if casting is valid, or \fBNULL\fP otherwise.
+.UNINDENT
+.TP
+.B \fBstruct udp6_sock *bpf_skc_to_udp6_sock(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Dynamically cast a \fIsk\fP pointer to a \fIudp6_sock\fP pointer.
+.TP
+.B Return
+\fIsk\fP if casting is valid, or \fBNULL\fP otherwise.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_task_stack(struct task_struct *\fP\fItask\fP\fB, void *\fP\fIbuf\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return a user or a kernel stack in bpf program provided buffer.
+To achieve this, the helper needs \fItask\fP, which is a valid
+pointer to \fBstruct task_struct\fP\&. To store the stacktrace, the
+bpf program provides \fIbuf\fP with a nonnegative \fIsize\fP\&.
+.sp
+The last argument, \fIflags\fP, holds the number of stack frames to
+skip (from 0 to 255), masked with
+\fBBPF_F_SKIP_FIELD_MASK\fP\&. The next bits can be used to set
+the following flags:
+.INDENT 7.0
+.TP
+.B \fBBPF_F_USER_STACK\fP
+Collect a user space stack instead of a kernel stack.
+.TP
+.B \fBBPF_F_USER_BUILD_ID\fP
+Collect buildid+offset instead of ips for user stack,
+only valid if \fBBPF_F_USER_STACK\fP is also specified.
+.UNINDENT
+.sp
+\fBbpf_get_task_stack\fP() can collect up to
+\fBPERF_MAX_STACK_DEPTH\fP both kernel and user frames, subject
+to sufficient large buffer size. Note that
+this limit can be controlled with the \fBsysctl\fP 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:
+.INDENT 7.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+# sysctl kernel.perf_event_max_stack=<new value>
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.TP
+.B Return
+The non\-negative copied \fIbuf\fP length equal to or less than
+\fIsize\fP on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_load_hdr_opt(struct bpf_sock_ops *\fP\fIskops\fP\fB, void *\fP\fIsearchby_res\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Load header option.  Support reading a particular TCP header
+option for bpf program (\fBBPF_PROG_TYPE_SOCK_OPS\fP).
+.sp
+If \fIflags\fP is 0, it will search the option from the
+\fIskops\fP\fB\->skb_data\fP\&.  The comment in \fBstruct bpf_sock_ops\fP
+has details on what skb_data contains under different
+\fIskops\fP\fB\->op\fP\&.
+.sp
+The first byte of the \fIsearchby_res\fP specifies the
+kind that it wants to search.
+.sp
+If the searching kind is an experimental kind
+(i.e. 253 or 254 according to RFC6994).  It also
+needs to specify the \(dqmagic\(dq which is either
+2 bytes or 4 bytes.  It then also needs to
+specify the size of the magic by using
+the 2nd byte which is \(dqkind\-length\(dq of a TCP
+header option and the \(dqkind\-length\(dq also
+includes the first 2 bytes \(dqkind\(dq and \(dqkind\-length\(dq
+itself as a normal TCP header option also does.
+.sp
+For example, to search experimental kind 254 with
+2 byte magic 0xeB9F, the searchby_res should be
+[ 254, 4, 0xeB, 0x9F, 0, 0, .... 0 ].
+.sp
+To search for the standard window scale option (3),
+the \fIsearchby_res\fP should be [ 3, 0, 0, .... 0 ].
+Note, kind\-length must be 0 for regular option.
+.sp
+Searching for No\-Op (0) and End\-of\-Option\-List (1) are
+not supported.
+.sp
+\fIlen\fP must be at least 2 bytes which is the minimal size
+of a header option.
+.sp
+Supported flags:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_LOAD_HDR_OPT_TCP_SYN\fP to search from the
+saved_syn packet or the just\-received syn packet.
+.UNINDENT
+.TP
+.B Return
+> 0 when found, the header option is copied to \fIsearchby_res\fP\&.
+The return value is the total length copied. On failure, a
+negative error code is returned:
+.sp
+\fB\-EINVAL\fP if a parameter is invalid.
+.sp
+\fB\-ENOMSG\fP if the option is not found.
+.sp
+\fB\-ENOENT\fP if no syn packet is available when
+\fBBPF_LOAD_HDR_OPT_TCP_SYN\fP is used.
+.sp
+\fB\-ENOSPC\fP if there is not enough space.  Only \fIlen\fP number of
+bytes are copied.
+.sp
+\fB\-EFAULT\fP on failure to parse the header options in the
+packet.
+.sp
+\fB\-EPERM\fP if the helper cannot be used under the current
+\fIskops\fP\fB\->op\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_store_hdr_opt(struct bpf_sock_ops *\fP\fIskops\fP\fB, const void *\fP\fIfrom\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Store header option.  The data will be copied
+from buffer \fIfrom\fP with length \fIlen\fP to the TCP header.
+.sp
+The buffer \fIfrom\fP should have the whole option that
+includes the kind, kind\-length, and the actual
+option data.  The \fIlen\fP must be at least kind\-length
+long.  The kind\-length does not have to be 4 byte
+aligned.  The kernel will take care of the padding
+and setting the 4 bytes aligned value to th\->doff.
+.sp
+This helper will check for duplicated option
+by searching the same option in the outgoing skb.
+.sp
+This helper can only be called during
+\fBBPF_SOCK_OPS_WRITE_HDR_OPT_CB\fP\&.
+.TP
+.B Return
+0 on success, or negative error in case of failure:
+.sp
+\fB\-EINVAL\fP If param is invalid.
+.sp
+\fB\-ENOSPC\fP if there is not enough space in the header.
+Nothing has been written
+.sp
+\fB\-EEXIST\fP if the option already exists.
+.sp
+\fB\-EFAULT\fP on failure to parse the existing header options.
+.sp
+\fB\-EPERM\fP if the helper cannot be used under the current
+\fIskops\fP\fB\->op\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_reserve_hdr_opt(struct bpf_sock_ops *\fP\fIskops\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Reserve \fIlen\fP bytes for the bpf header option.  The
+space will be used by \fBbpf_store_hdr_opt\fP() later in
+\fBBPF_SOCK_OPS_WRITE_HDR_OPT_CB\fP\&.
+.sp
+If \fBbpf_reserve_hdr_opt\fP() is called multiple times,
+the total number of bytes will be reserved.
+.sp
+This helper can only be called during
+\fBBPF_SOCK_OPS_HDR_OPT_LEN_CB\fP\&.
+.TP
+.B Return
+0 on success, or negative error in case of failure:
+.sp
+\fB\-EINVAL\fP if a parameter is invalid.
+.sp
+\fB\-ENOSPC\fP if there is not enough space in the header.
+.sp
+\fB\-EPERM\fP if the helper cannot be used under the current
+\fIskops\fP\fB\->op\fP\&.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_inode_storage_get(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIinode\fP\fB, void *\fP\fIvalue\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get a bpf_local_storage from an \fIinode\fP\&.
+.sp
+Logically, it could be thought of as getting the value from
+a \fImap\fP with \fIinode\fP as the \fBkey\fP\&.  From this
+perspective,  the usage is not much different from
+\fBbpf_map_lookup_elem\fP(\fImap\fP, \fB&\fP\fIinode\fP) except this
+helper enforces the key must be an inode and the map must also
+be a \fBBPF_MAP_TYPE_INODE_STORAGE\fP\&.
+.sp
+Underneath, the value is stored locally at \fIinode\fP instead of
+the \fImap\fP\&.  The \fImap\fP is used as the bpf\-local\-storage
+\(dqtype\(dq. The bpf\-local\-storage \(dqtype\(dq (i.e. the \fImap\fP) is
+searched against all bpf_local_storage residing at \fIinode\fP\&.
+.sp
+An optional \fIflags\fP (\fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP) can be
+used such that a new bpf_local_storage will be
+created if one does not exist.  \fIvalue\fP can be used
+together with \fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP to specify
+the initial value of a bpf_local_storage.  If \fIvalue\fP is
+\fBNULL\fP, the new bpf_local_storage will be zero initialized.
+.TP
+.B Return
+A bpf_local_storage pointer is returned on success.
+.sp
+\fBNULL\fP if not found or there was an error in adding
+a new bpf_local_storage.
+.UNINDENT
+.TP
+.B \fBint bpf_inode_storage_delete(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIinode\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Delete a bpf_local_storage from an \fIinode\fP\&.
+.TP
+.B Return
+0 on success.
+.sp
+\fB\-ENOENT\fP if the bpf_local_storage cannot be found.
+.UNINDENT
+.TP
+.B \fBlong bpf_d_path(struct path *\fP\fIpath\fP\fB, char *\fP\fIbuf\fP\fB, u32\fP \fIsz\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return full path for given \fBstruct path\fP object, which
+needs to be the kernel BTF \fIpath\fP object. The path is
+returned in the provided buffer \fIbuf\fP of size \fIsz\fP and
+is zero terminated.
+.TP
+.B Return
+On success, the strictly positive length of the string,
+including the trailing NUL character. On error, a negative
+value.
+.UNINDENT
+.TP
+.B \fBlong bpf_copy_from_user(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIuser_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Read \fIsize\fP bytes from user space address \fIuser_ptr\fP and store
+the data in \fIdst\fP\&. This is a wrapper of \fBcopy_from_user\fP().
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_snprintf_btf(char *\fP\fIstr\fP\fB, u32\fP \fIstr_size\fP\fB, struct btf_ptr *\fP\fIptr\fP\fB, u32\fP \fIbtf_ptr_size\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Use BTF to store a string representation of \fIptr\fP\->ptr in \fIstr\fP,
+using \fIptr\fP\->type_id.  This value should specify the type
+that \fIptr\fP\->ptr points to. LLVM __builtin_btf_type_id(type, 1)
+can be used to look up vmlinux BTF type ids. Traversing the
+data structure using BTF, the type information and values are
+stored in the first \fIstr_size\fP \- 1 bytes of \fIstr\fP\&.  Safe copy of
+the pointer data is carried out to avoid kernel crashes during
+operation.  Smaller types can use string space on the stack;
+larger programs can use map data to store the string
+representation.
+.sp
+The string can be subsequently shared with userspace via
+bpf_perf_event_output() or ring buffer interfaces.
+bpf_trace_printk() is to be avoided as it places too small
+a limit on string size to be useful.
+.sp
+\fIflags\fP is a combination of
+.INDENT 7.0
+.TP
+.B \fBBTF_F_COMPACT\fP
+no formatting around type information
+.TP
+.B \fBBTF_F_NONAME\fP
+no struct/union member names/types
+.TP
+.B \fBBTF_F_PTR_RAW\fP
+show raw (unobfuscated) pointer values;
+equivalent to printk specifier %px.
+.TP
+.B \fBBTF_F_ZERO\fP
+show zero\-valued struct/union members; they
+are not displayed by default
+.UNINDENT
+.TP
+.B Return
+The number of bytes that were written (or would have been
+written if output had to be truncated due to string size),
+or a negative error in cases of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_seq_printf_btf(struct seq_file *\fP\fIm\fP\fB, struct btf_ptr *\fP\fIptr\fP\fB, u32\fP \fIptr_size\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Use BTF to write to seq_write a string representation of
+\fIptr\fP\->ptr, using \fIptr\fP\->type_id as per bpf_snprintf_btf().
+\fIflags\fP are identical to those used for bpf_snprintf_btf.
+.TP
+.B Return
+0 on success or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu64 bpf_skb_cgroup_classid(struct sk_buff *\fP\fIskb\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+See \fBbpf_get_cgroup_classid\fP() for the main description.
+This helper differs from \fBbpf_get_cgroup_classid\fP() in that
+the cgroup v1 net_cls class is retrieved only from the \fIskb\fP\(aqs
+associated socket instead of the current process.
+.TP
+.B Return
+The id is returned or 0 in case the id could not be retrieved.
+.UNINDENT
+.TP
+.B \fBlong bpf_redirect_neigh(u32\fP \fIifindex\fP\fB, struct bpf_redir_neigh *\fP\fIparams\fP\fB, int\fP \fIplen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Redirect the packet to another net device of index \fIifindex\fP
+and fill in L2 addresses from neighboring subsystem. This helper
+is somewhat similar to \fBbpf_redirect\fP(), except that it
+populates L2 addresses as well, meaning, internally, the helper
+relies on the neighbor lookup for the L2 address of the nexthop.
+.sp
+The helper will perform a FIB lookup based on the skb\(aqs
+networking header to get the address of the next hop, unless
+this is supplied by the caller in the \fIparams\fP argument. The
+\fIplen\fP argument indicates the len of \fIparams\fP and should be set
+to 0 if \fIparams\fP is NULL.
+.sp
+The \fIflags\fP argument is reserved and must be 0. The helper is
+currently only supported for tc BPF program types, and enabled
+for IPv4 and IPv6 protocols.
+.TP
+.B Return
+The helper returns \fBTC_ACT_REDIRECT\fP on success or
+\fBTC_ACT_SHOT\fP on error.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_per_cpu_ptr(const void *\fP\fIpercpu_ptr\fP\fB, u32\fP \fIcpu\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Take a pointer to a percpu ksym, \fIpercpu_ptr\fP, and return a
+pointer to the percpu kernel variable on \fIcpu\fP\&. A ksym is an
+extern variable decorated with \(aq__ksym\(aq. For ksym, there is a
+global var (either static or global) defined of the same name
+in the kernel. The ksym is percpu if the global var is percpu.
+The returned pointer points to the global percpu var on \fIcpu\fP\&.
+.sp
+bpf_per_cpu_ptr() has the same semantic as per_cpu_ptr() in the
+kernel, except that bpf_per_cpu_ptr() may return NULL. This
+happens if \fIcpu\fP is larger than nr_cpu_ids. The caller of
+bpf_per_cpu_ptr() must check the returned value.
+.TP
+.B Return
+A pointer pointing to the kernel percpu variable on \fIcpu\fP, or
+NULL, if \fIcpu\fP is invalid.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_this_cpu_ptr(const void *\fP\fIpercpu_ptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Take a pointer to a percpu ksym, \fIpercpu_ptr\fP, and return a
+pointer to the percpu kernel variable on this cpu. See the
+description of \(aqksym\(aq in \fBbpf_per_cpu_ptr\fP().
+.sp
+bpf_this_cpu_ptr() has the same semantic as this_cpu_ptr() in
+the kernel. Different from \fBbpf_per_cpu_ptr\fP(), it would
+never return NULL.
+.TP
+.B Return
+A pointer pointing to the kernel percpu variable on this cpu.
+.UNINDENT
+.TP
+.B \fBlong bpf_redirect_peer(u32\fP \fIifindex\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Redirect the packet to another net device of index \fIifindex\fP\&.
+This helper is somewhat similar to \fBbpf_redirect\fP(), except
+that the redirection happens to the \fIifindex\fP\(aq peer device and
+the netns switch takes place from ingress to ingress without
+going through the CPU\(aqs backlog queue.
+.sp
+The \fIflags\fP argument is reserved and must be 0. The helper is
+currently only supported for tc BPF program types at the ingress
+hook and for veth device types. The peer device must reside in a
+different network namespace.
+.TP
+.B Return
+The helper returns \fBTC_ACT_REDIRECT\fP on success or
+\fBTC_ACT_SHOT\fP on error.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_task_storage_get(struct bpf_map *\fP\fImap\fP\fB, struct task_struct *\fP\fItask\fP\fB, void *\fP\fIvalue\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get a bpf_local_storage from the \fItask\fP\&.
+.sp
+Logically, it could be thought of as getting the value from
+a \fImap\fP with \fItask\fP as the \fBkey\fP\&.  From this
+perspective,  the usage is not much different from
+\fBbpf_map_lookup_elem\fP(\fImap\fP, \fB&\fP\fItask\fP) except this
+helper enforces the key must be a task_struct and the map must also
+be a \fBBPF_MAP_TYPE_TASK_STORAGE\fP\&.
+.sp
+Underneath, the value is stored locally at \fItask\fP instead of
+the \fImap\fP\&.  The \fImap\fP is used as the bpf\-local\-storage
+\(dqtype\(dq. The bpf\-local\-storage \(dqtype\(dq (i.e. the \fImap\fP) is
+searched against all bpf_local_storage residing at \fItask\fP\&.
+.sp
+An optional \fIflags\fP (\fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP) can be
+used such that a new bpf_local_storage will be
+created if one does not exist.  \fIvalue\fP can be used
+together with \fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP to specify
+the initial value of a bpf_local_storage.  If \fIvalue\fP is
+\fBNULL\fP, the new bpf_local_storage will be zero initialized.
+.TP
+.B Return
+A bpf_local_storage pointer is returned on success.
+.sp
+\fBNULL\fP if not found or there was an error in adding
+a new bpf_local_storage.
+.UNINDENT
+.TP
+.B \fBlong bpf_task_storage_delete(struct bpf_map *\fP\fImap\fP\fB, struct task_struct *\fP\fItask\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Delete a bpf_local_storage from a \fItask\fP\&.
+.TP
+.B Return
+0 on success.
+.sp
+\fB\-ENOENT\fP if the bpf_local_storage cannot be found.
+.UNINDENT
+.TP
+.B \fBstruct task_struct *bpf_get_current_task_btf(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return a BTF pointer to the \(dqcurrent\(dq task.
+This pointer can also be used in helpers that accept an
+\fIARG_PTR_TO_BTF_ID\fP of type \fItask_struct\fP\&.
+.TP
+.B Return
+Pointer to the current task.
+.UNINDENT
+.TP
+.B \fBlong bpf_bprm_opts_set(struct linux_binprm *\fP\fIbprm\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Set or clear certain options on \fIbprm\fP:
+.sp
+\fBBPF_F_BPRM_SECUREEXEC\fP Set the secureexec bit
+which sets the \fBAT_SECURE\fP auxv for glibc. The bit
+is cleared if the flag is not specified.
+.TP
+.B Return
+\fB\-EINVAL\fP if invalid \fIflags\fP are passed, zero otherwise.
+.UNINDENT
+.TP
+.B \fBu64 bpf_ktime_get_coarse_ns(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Return a coarse\-grained version of the time elapsed since
+system boot, in nanoseconds. Does not include time the system
+was suspended.
+.sp
+See: \fBclock_gettime\fP(\fBCLOCK_MONOTONIC_COARSE\fP)
+.TP
+.B Return
+Current \fIktime\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_ima_inode_hash(struct inode *\fP\fIinode\fP\fB, void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Returns the stored IMA hash of the \fIinode\fP (if it\(aqs available).
+If the hash is larger than \fIsize\fP, then only \fIsize\fP
+bytes will be copied to \fIdst\fP
+.TP
+.B Return
+The \fBhash_algo\fP is returned on success,
+\fB\-EOPNOTSUP\fP if IMA is disabled or \fB\-EINVAL\fP if
+invalid arguments are passed.
+.UNINDENT
+.TP
+.B \fBstruct socket *bpf_sock_from_file(struct file *\fP\fIfile\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+If the given file represents a socket, returns the associated
+socket.
+.TP
+.B Return
+A pointer to a struct socket on success or NULL if the file is
+not a socket.
+.UNINDENT
+.TP
+.B \fBlong bpf_check_mtu(void *\fP\fIctx\fP\fB, u32\fP \fIifindex\fP\fB, u32 *\fP\fImtu_len\fP\fB, s32\fP \fIlen_diff\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Check packet size against exceeding MTU of net device (based
+on \fIifindex\fP).  This helper will likely be used in combination
+with helpers that adjust/change the packet size.
+.sp
+The argument \fIlen_diff\fP can be used for querying with a planned
+size change. This allows to check MTU prior to changing packet
+ctx. Providing a \fIlen_diff\fP adjustment that is larger than the
+actual packet size (resulting in negative packet size) will in
+principle not exceed the MTU, which is why it is not considered
+a failure.  Other BPF helpers are needed for performing the
+planned size change; therefore the responsibility for catching
+a negative packet size belongs in those helpers.
+.sp
+Specifying \fIifindex\fP zero means the MTU check is performed
+against the current net device.  This is practical if this isn\(aqt
+used prior to redirect.
+.sp
+On input \fImtu_len\fP must be a valid pointer, else verifier will
+reject BPF program.  If the value \fImtu_len\fP is initialized to
+zero then the ctx packet size is use.  When value \fImtu_len\fP is
+provided as input this specify the L3 length that the MTU check
+is done against. Remember XDP and TC length operate at L2, but
+this value is L3 as this correlate to MTU and IP\-header tot_len
+values which are L3 (similar behavior as bpf_fib_lookup).
+.sp
+The Linux kernel route table can configure MTUs on a more
+specific per route level, which is not provided by this helper.
+For route level MTU checks use the \fBbpf_fib_lookup\fP()
+helper.
+.sp
+\fIctx\fP is either \fBstruct xdp_md\fP for XDP programs or
+\fBstruct sk_buff\fP for tc cls_act programs.
+.sp
+The \fIflags\fP argument can be a combination of one or more of the
+following values:
+.INDENT 7.0
+.TP
+.B \fBBPF_MTU_CHK_SEGS\fP
+This flag will only works for \fIctx\fP \fBstruct sk_buff\fP\&.
+If packet context contains extra packet segment buffers
+(often knows as GSO skb), then MTU check is harder to
+check at this point, because in transmit path it is
+possible for the skb packet to get re\-segmented
+(depending on net device features).  This could still be
+a MTU violation, so this flag enables performing MTU
+check against segments, with a different violation
+return code to tell it apart. Check cannot use len_diff.
+.UNINDENT
+.sp
+On return \fImtu_len\fP pointer contains the MTU value of the net
+device.  Remember the net device configured MTU is the L3 size,
+which is returned here and XDP and TC length operate at L2.
+Helper take this into account for you, but remember when using
+MTU value in your BPF\-code.
+.TP
+.B Return
+.INDENT 7.0
+.IP \(bu 2
+0 on success, and populate MTU value in \fImtu_len\fP pointer.
+.IP \(bu 2
+< 0 if any input argument is invalid (\fImtu_len\fP not updated)
+.UNINDENT
+.sp
+MTU violations return positive values, but also populate MTU
+value in \fImtu_len\fP pointer, as this can be needed for
+implementing PMTU handing:
+.INDENT 7.0
+.IP \(bu 2
+\fBBPF_MTU_CHK_RET_FRAG_NEEDED\fP
+.IP \(bu 2
+\fBBPF_MTU_CHK_RET_SEGS_TOOBIG\fP
+.UNINDENT
+.UNINDENT
+.TP
+.B \fBlong bpf_for_each_map_elem(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIcallback_fn\fP\fB, void *\fP\fIcallback_ctx\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For each element in \fBmap\fP, call \fBcallback_fn\fP function with
+\fBmap\fP, \fBcallback_ctx\fP and other map\-specific parameters.
+The \fBcallback_fn\fP should be a static function and
+the \fBcallback_ctx\fP should be a pointer to the stack.
+The \fBflags\fP is used to control certain aspects of the helper.
+Currently, the \fBflags\fP must be 0.
+.sp
+The following are a list of supported map types and their
+respective expected callback signatures:
+.sp
+BPF_MAP_TYPE_HASH, BPF_MAP_TYPE_PERCPU_HASH,
+BPF_MAP_TYPE_LRU_HASH, BPF_MAP_TYPE_LRU_PERCPU_HASH,
+BPF_MAP_TYPE_ARRAY, BPF_MAP_TYPE_PERCPU_ARRAY
+.sp
+long (*callback_fn)(struct bpf_map *map, const void *key, void *value, void *ctx);
+.sp
+For per_cpu maps, the map_value is the value on the cpu where the
+bpf_prog is running.
+.sp
+If \fBcallback_fn\fP return 0, the helper will continue to the next
+element. If return value is 1, the helper will skip the rest of
+elements and return. Other return values are not used now.
+.TP
+.B Return
+The number of traversed map elements for success, \fB\-EINVAL\fP for
+invalid \fBflags\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_snprintf(char *\fP\fIstr\fP\fB, u32\fP \fIstr_size\fP\fB, const char *\fP\fIfmt\fP\fB, u64 *\fP\fIdata\fP\fB, u32\fP \fIdata_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Outputs a string into the \fBstr\fP buffer of size \fBstr_size\fP
+based on a format string stored in a read\-only map pointed by
+\fBfmt\fP\&.
+.sp
+Each format specifier in \fBfmt\fP corresponds to one u64 element
+in the \fBdata\fP array. For strings and pointers where pointees
+are accessed, only the pointer values are stored in the \fIdata\fP
+array. The \fIdata_len\fP is the size of \fIdata\fP in bytes \- must be
+a multiple of 8.
+.sp
+Formats \fB%s\fP and \fB%p{i,I}{4,6}\fP require 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 \fB%s\fP will be an
+empty string, and the ip address for \fB%p{i,I}{4,6}\fP will be 0.
+Not returning error to bpf program is consistent with what
+\fBbpf_trace_printk\fP() does for now.
+.TP
+.B Return
+The strictly positive length of the formatted string, including
+the trailing zero character. If the return value is greater than
+\fBstr_size\fP, \fBstr\fP contains a truncated string, guaranteed to
+be zero\-terminated except when \fBstr_size\fP is 0.
+.sp
+Or \fB\-EBUSY\fP if the per\-CPU memory copy buffer is busy.
+.UNINDENT
+.TP
+.B \fBlong bpf_sys_bpf(u32\fP \fIcmd\fP\fB, void *\fP\fIattr\fP\fB, u32\fP \fIattr_size\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Execute bpf syscall with given arguments.
+.TP
+.B Return
+A syscall result.
+.UNINDENT
+.TP
+.B \fBlong bpf_btf_find_by_name_kind(char *\fP\fIname\fP\fB, int\fP \fIname_sz\fP\fB, u32\fP \fIkind\fP\fB, int\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Find BTF type with given name and kind in vmlinux BTF or in module\(aqs BTFs.
+.TP
+.B Return
+Returns btf_id and btf_obj_fd in lower and upper 32 bits.
+.UNINDENT
+.TP
+.B \fBlong bpf_sys_close(u32\fP \fIfd\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Execute close syscall for given FD.
+.TP
+.B Return
+A syscall result.
+.UNINDENT
+.TP
+.B \fBlong bpf_timer_init(struct bpf_timer *\fP\fItimer\fP\fB, struct bpf_map *\fP\fImap\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Initialize the timer.
+First 4 bits of \fIflags\fP specify clockid.
+Only CLOCK_MONOTONIC, CLOCK_REALTIME, CLOCK_BOOTTIME are allowed.
+All other bits of \fIflags\fP are reserved.
+The verifier will reject the program if \fItimer\fP is not from
+the same \fImap\fP\&.
+.TP
+.B Return
+0 on success.
+\fB\-EBUSY\fP if \fItimer\fP is already initialized.
+\fB\-EINVAL\fP if invalid \fIflags\fP are passed.
+\fB\-EPERM\fP if \fItimer\fP is in a map that doesn\(aqt have any user references.
+The user space should either hold a file descriptor to a map with timers
+or pin such map in bpffs. When map is unpinned or file descriptor is
+closed all timers in the map will be cancelled and freed.
+.UNINDENT
+.TP
+.B \fBlong bpf_timer_set_callback(struct bpf_timer *\fP\fItimer\fP\fB, void *\fP\fIcallback_fn\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Configure the timer to call \fIcallback_fn\fP static function.
+.TP
+.B Return
+0 on success.
+\fB\-EINVAL\fP if \fItimer\fP was not initialized with bpf_timer_init() earlier.
+\fB\-EPERM\fP if \fItimer\fP is in a map that doesn\(aqt have any user references.
+The user space should either hold a file descriptor to a map with timers
+or pin such map in bpffs. When map is unpinned or file descriptor is
+closed all timers in the map will be cancelled and freed.
+.UNINDENT
+.TP
+.B \fBlong bpf_timer_start(struct bpf_timer *\fP\fItimer\fP\fB, u64\fP \fInsecs\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Set timer expiration N nanoseconds from the current time. The
+configured callback will be invoked in soft irq context on some cpu
+and will not repeat unless another bpf_timer_start() is made.
+In such case the next invocation can migrate to a different cpu.
+Since struct bpf_timer is a field inside map element the map
+owns the timer. The bpf_timer_set_callback() will increment refcnt
+of BPF program to make sure that callback_fn code stays valid.
+When user space reference to a map reaches zero all timers
+in a map are cancelled and corresponding program\(aqs refcnts are
+decremented. This is done to make sure that Ctrl\-C of a user
+process doesn\(aqt leave any timers running. If map is pinned in
+bpffs the callback_fn can re\-arm itself indefinitely.
+bpf_map_update/delete_elem() helpers and user space sys_bpf commands
+cancel and free the timer in the given map element.
+The map can contain timers that invoke callback_fn\-s from different
+programs. The same callback_fn can serve different timers from
+different maps if key/value layout matches across maps.
+Every bpf_timer_set_callback() can have different callback_fn.
+.TP
+.B Return
+0 on success.
+\fB\-EINVAL\fP if \fItimer\fP was not initialized with bpf_timer_init() earlier
+or invalid \fIflags\fP are passed.
+.UNINDENT
+.TP
+.B \fBlong bpf_timer_cancel(struct bpf_timer *\fP\fItimer\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Cancel the timer and wait for callback_fn to finish if it was running.
+.TP
+.B Return
+0 if the timer was not active.
+1 if the timer was active.
+\fB\-EINVAL\fP if \fItimer\fP was not initialized with bpf_timer_init() earlier.
+\fB\-EDEADLK\fP if callback_fn tried to call bpf_timer_cancel() on its
+own timer which would have led to a deadlock otherwise.
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_func_ip(void *\fP\fIctx\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get address of the traced function (for tracing and kprobe programs).
+.TP
+.B Return
+Address of the traced function.
+0 for kprobes placed within the function (not at the entry).
+.UNINDENT
+.TP
+.B \fBu64 bpf_get_attach_cookie(void *\fP\fIctx\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get bpf_cookie value provided (optionally) during the program
+attachment. It might be different for each individual
+attachment, even if BPF program itself is the same.
+Expects BPF program context \fIctx\fP as a first argument.
+.INDENT 7.0
+.TP
+.B Supported for the following program types:
+.INDENT 7.0
+.IP \(bu 2
+kprobe/uprobe;
+.IP \(bu 2
+tracepoint;
+.IP \(bu 2
+perf_event.
+.UNINDENT
+.UNINDENT
+.TP
+.B Return
+Value specified by user at BPF link creation/attachment time
+or 0, if it was not specified.
+.UNINDENT
+.TP
+.B \fBlong bpf_task_pt_regs(struct task_struct *\fP\fItask\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the struct pt_regs associated with \fBtask\fP\&.
+.TP
+.B Return
+A pointer to struct pt_regs.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_branch_snapshot(void *\fP\fIentries\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get branch trace from hardware engines like Intel LBR. The
+hardware engine is stopped shortly after the helper is
+called. Therefore, the user need to filter branch entries
+based on the actual use case. To capture branch trace
+before the trigger point of the BPF program, the helper
+should be called at the beginning of the BPF program.
+.sp
+The data is stored as struct perf_branch_entry into output
+buffer \fIentries\fP\&. \fIsize\fP is the size of \fIentries\fP in bytes.
+\fIflags\fP is reserved for now and must be zero.
+.TP
+.B Return
+On success, number of bytes written to \fIbuf\fP\&. On error, a
+negative value.
+.sp
+\fB\-EINVAL\fP if \fIflags\fP is not zero.
+.sp
+\fB\-ENOENT\fP if architecture does not support branch records.
+.UNINDENT
+.TP
+.B \fBlong bpf_trace_vprintk(const char *\fP\fIfmt\fP\fB, u32\fP \fIfmt_size\fP\fB, const void *\fP\fIdata\fP\fB, u32\fP \fIdata_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Behaves like \fBbpf_trace_printk\fP() helper, but takes an array of u64
+to format and can handle more format args as a result.
+.sp
+Arguments are to be used as in \fBbpf_seq_printf\fP() helper.
+.TP
+.B Return
+The number of bytes written to the buffer, or a negative error
+in case of failure.
+.UNINDENT
+.TP
+.B \fBstruct unix_sock *bpf_skc_to_unix_sock(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Dynamically cast a \fIsk\fP pointer to a \fIunix_sock\fP pointer.
+.TP
+.B Return
+\fIsk\fP if casting is valid, or \fBNULL\fP otherwise.
+.UNINDENT
+.TP
+.B \fBlong bpf_kallsyms_lookup_name(const char *\fP\fIname\fP\fB, int\fP \fIname_sz\fP\fB, int\fP \fIflags\fP\fB, u64 *\fP\fIres\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the address of a kernel symbol, returned in \fIres\fP\&. \fIres\fP is
+set to 0 if the symbol is not found.
+.TP
+.B Return
+On success, zero. On error, a negative value.
+.sp
+\fB\-EINVAL\fP if \fIflags\fP is not zero.
+.sp
+\fB\-EINVAL\fP if string \fIname\fP is not the same size as \fIname_sz\fP\&.
+.sp
+\fB\-ENOENT\fP if symbol is not found.
+.sp
+\fB\-EPERM\fP if caller does not have permission to obtain kernel address.
+.UNINDENT
+.TP
+.B \fBlong bpf_find_vma(struct task_struct *\fP\fItask\fP\fB, u64\fP \fIaddr\fP\fB, void *\fP\fIcallback_fn\fP\fB, void *\fP\fIcallback_ctx\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Find vma of \fItask\fP that contains \fIaddr\fP, call \fIcallback_fn\fP
+function with \fItask\fP, \fIvma\fP, and \fIcallback_ctx\fP\&.
+The \fIcallback_fn\fP should be a static function and
+the \fIcallback_ctx\fP should be a pointer to the stack.
+The \fIflags\fP is used to control certain aspects of the helper.
+Currently, the \fIflags\fP must be 0.
+.sp
+The expected callback signature is
+.sp
+long (*callback_fn)(struct task_struct *task, struct vm_area_struct *vma, void *callback_ctx);
+.TP
+.B Return
+0 on success.
+\fB\-ENOENT\fP if \fItask\->mm\fP is NULL, or no vma contains \fIaddr\fP\&.
+\fB\-EBUSY\fP if failed to try lock mmap_lock.
+\fB\-EINVAL\fP for invalid \fBflags\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_loop(u32\fP \fInr_loops\fP\fB, void *\fP\fIcallback_fn\fP\fB, void *\fP\fIcallback_ctx\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+For \fBnr_loops\fP, call \fBcallback_fn\fP function
+with \fBcallback_ctx\fP as the context parameter.
+The \fBcallback_fn\fP should be a static function and
+the \fBcallback_ctx\fP should be a pointer to the stack.
+The \fBflags\fP is used to control certain aspects of the helper.
+Currently, the \fBflags\fP must be 0. Currently, nr_loops is
+limited to 1 << 23 (~8 million) loops.
+.sp
+long (*callback_fn)(u32 index, void *ctx);
+.sp
+where \fBindex\fP is the current index in the loop. The index
+is zero\-indexed.
+.sp
+If \fBcallback_fn\fP returns 0, the helper will continue to the next
+loop. If return value is 1, the helper will skip the rest of
+the loops and return. Other return values are not used now,
+and will be rejected by the verifier.
+.TP
+.B Return
+The number of loops performed, \fB\-EINVAL\fP for invalid \fBflags\fP,
+\fB\-E2BIG\fP if \fBnr_loops\fP exceeds the maximum number of loops.
+.UNINDENT
+.TP
+.B \fBlong bpf_strncmp(const char *\fP\fIs1\fP\fB, u32\fP \fIs1_sz\fP\fB, const char *\fP\fIs2\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Do strncmp() between \fBs1\fP and \fBs2\fP\&. \fBs1\fP doesn\(aqt need
+to be null\-terminated and \fBs1_sz\fP is the maximum storage
+size of \fBs1\fP\&. \fBs2\fP must be a read\-only string.
+.TP
+.B Return
+An integer less than, equal to, or greater than zero
+if the first \fBs1_sz\fP bytes of \fBs1\fP is found to be
+less than, to match, or be greater than \fBs2\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_func_arg(void *\fP\fIctx\fP\fB, u32\fP \fIn\fP\fB, u64 *\fP\fIvalue\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get \fBn\fP\-th argument register (zero based) of the traced function (for tracing programs)
+returned in \fBvalue\fP\&.
+.TP
+.B Return
+0 on success.
+\fB\-EINVAL\fP if n >= argument register count of traced function.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_func_ret(void *\fP\fIctx\fP\fB, u64 *\fP\fIvalue\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get return value of the traced function (for tracing programs)
+in \fBvalue\fP\&.
+.TP
+.B Return
+0 on success.
+\fB\-EOPNOTSUPP\fP for tracing programs other than BPF_TRACE_FEXIT or BPF_MODIFY_RETURN.
+.UNINDENT
+.TP
+.B \fBlong bpf_get_func_arg_cnt(void *\fP\fIctx\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get number of registers of the traced function (for tracing programs) where
+function arguments are stored in these registers.
+.TP
+.B Return
+The number of argument registers of the traced function.
+.UNINDENT
+.TP
+.B \fBint bpf_get_retval(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the BPF program\(aqs return value that will be returned to the upper layers.
+.sp
+This helper is currently supported by cgroup programs and only by the hooks
+where BPF program\(aqs return value is returned to the userspace via errno.
+.TP
+.B Return
+The BPF program\(aqs return value.
+.UNINDENT
+.TP
+.B \fBint bpf_set_retval(int\fP \fIretval\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Set the BPF program\(aqs return value that will be returned to the upper layers.
+.sp
+This helper is currently supported by cgroup programs and only by the hooks
+where BPF program\(aqs return value is returned to the userspace via errno.
+.sp
+Note that there is the following corner case where the program exports an error
+via bpf_set_retval but signals success via \(aqreturn 1\(aq:
+.INDENT 7.0
+.INDENT 3.5
+bpf_set_retval(\-EPERM);
+return 1;
+.UNINDENT
+.UNINDENT
+.sp
+In this case, the BPF program\(aqs return value will use helper\(aqs \-EPERM. This
+still holds true for cgroup/bind{4,6} which supports extra \(aqreturn 3\(aq success case.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBu64 bpf_xdp_get_buff_len(struct xdp_buff *\fP\fIxdp_md\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get the total size of a given xdp buff (linear and paged area)
+.TP
+.B Return
+The total size of a given xdp buffer.
+.UNINDENT
+.TP
+.B \fBlong bpf_xdp_load_bytes(struct xdp_buff *\fP\fIxdp_md\fP\fB, u32\fP \fIoffset\fP\fB, void *\fP\fIbuf\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+This helper is provided as an easy way to load data from a
+xdp buffer. It can be used to load \fIlen\fP bytes from \fIoffset\fP from
+the frame associated to \fIxdp_md\fP, into the buffer pointed by
+\fIbuf\fP\&.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_xdp_store_bytes(struct xdp_buff *\fP\fIxdp_md\fP\fB, u32\fP \fIoffset\fP\fB, void *\fP\fIbuf\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Store \fIlen\fP bytes from buffer \fIbuf\fP into the frame
+associated to \fIxdp_md\fP, at \fIoffset\fP\&.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBlong bpf_copy_from_user_task(void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB, const void *\fP\fIuser_ptr\fP\fB, struct task_struct *\fP\fItsk\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Read \fIsize\fP bytes from user space address \fIuser_ptr\fP in \fItsk\fP\(aqs
+address space, and stores the data in \fIdst\fP\&. \fIflags\fP is not
+used yet and is provided for future extensibility. This helper
+can only be used by sleepable programs.
+.TP
+.B Return
+0 on success, or a negative error in case of failure. On error
+\fIdst\fP buffer is zeroed out.
+.UNINDENT
+.TP
+.B \fBlong bpf_skb_set_tstamp(struct sk_buff *\fP\fIskb\fP\fB, u64\fP \fItstamp\fP\fB, u32\fP \fItstamp_type\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Change the __sk_buff\->tstamp_type to \fItstamp_type\fP
+and set \fItstamp\fP to the __sk_buff\->tstamp together.
+.sp
+If there is no need to change the __sk_buff\->tstamp_type,
+the tstamp value can be directly written to __sk_buff\->tstamp
+instead.
+.sp
+BPF_SKB_TSTAMP_DELIVERY_MONO is the only tstamp that
+will be kept during bpf_redirect_*().  A non zero
+\fItstamp\fP must be used with the BPF_SKB_TSTAMP_DELIVERY_MONO
+\fItstamp_type\fP\&.
+.sp
+A BPF_SKB_TSTAMP_UNSPEC \fItstamp_type\fP can only be used
+with a zero \fItstamp\fP\&.
+.sp
+Only IPv4 and IPv6 skb\->protocol are supported.
+.sp
+This function is most useful when it needs to set a
+mono delivery time to __sk_buff\->tstamp and then
+bpf_redirect_*() to the egress of an iface.  For example,
+changing the (rcv) timestamp in __sk_buff\->tstamp at
+ingress to a mono delivery time and then bpf_redirect_*()
+to \fI\%sch_fq@phy\-dev\fP\&.
+.TP
+.B Return
+0 on success.
+\fB\-EINVAL\fP for invalid input
+\fB\-EOPNOTSUPP\fP for unsupported protocol
+.UNINDENT
+.TP
+.B \fBlong bpf_ima_file_hash(struct file *\fP\fIfile\fP\fB, void *\fP\fIdst\fP\fB, u32\fP \fIsize\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Returns a calculated IMA hash of the \fIfile\fP\&.
+If the hash is larger than \fIsize\fP, then only \fIsize\fP
+bytes will be copied to \fIdst\fP
+.TP
+.B Return
+The \fBhash_algo\fP is returned on success,
+\fB\-EOPNOTSUP\fP if the hash calculation failed or \fB\-EINVAL\fP if
+invalid arguments are passed.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_kptr_xchg(void *\fP\fImap_value\fP\fB, void *\fP\fIptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Exchange kptr at pointer \fImap_value\fP with \fIptr\fP, and return the
+old value. \fIptr\fP can be NULL, otherwise it must be a referenced
+pointer which will be released when this helper is called.
+.TP
+.B Return
+The old value of kptr (which can be NULL). The returned pointer
+if not NULL, is a reference which must be released using its
+corresponding release function, or moved into a BPF map before
+program exit.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_map_lookup_percpu_elem(struct bpf_map *\fP\fImap\fP\fB, const void *\fP\fIkey\fP\fB, u32\fP \fIcpu\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Perform a lookup in \fIpercpu map\fP for an entry associated to
+\fIkey\fP on \fIcpu\fP\&.
+.TP
+.B Return
+Map value associated to \fIkey\fP on \fIcpu\fP, or \fBNULL\fP if no entry
+was found or \fIcpu\fP is invalid.
+.UNINDENT
+.TP
+.B \fBstruct mptcp_sock *bpf_skc_to_mptcp_sock(void *\fP\fIsk\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Dynamically cast a \fIsk\fP pointer to a \fImptcp_sock\fP pointer.
+.TP
+.B Return
+\fIsk\fP if casting is valid, or \fBNULL\fP otherwise.
+.UNINDENT
+.TP
+.B \fBlong bpf_dynptr_from_mem(void *\fP\fIdata\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB, struct bpf_dynptr *\fP\fIptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get a dynptr to local memory \fIdata\fP\&.
+.sp
+\fIdata\fP must be a ptr to a map value.
+The maximum \fIsize\fP supported is DYNPTR_MAX_SIZE.
+\fIflags\fP is currently unused.
+.TP
+.B Return
+0 on success, \-E2BIG if the size exceeds DYNPTR_MAX_SIZE,
+\-EINVAL if flags is not 0.
+.UNINDENT
+.TP
+.B \fBlong bpf_ringbuf_reserve_dynptr(void *\fP\fIringbuf\fP\fB, u32\fP \fIsize\fP\fB, u64\fP \fIflags\fP\fB, struct bpf_dynptr *\fP\fIptr\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Reserve \fIsize\fP bytes of payload in a ring buffer \fIringbuf\fP
+through the dynptr interface. \fIflags\fP must be 0.
+.sp
+Please note that a corresponding bpf_ringbuf_submit_dynptr or
+bpf_ringbuf_discard_dynptr must be called on \fIptr\fP, even if the
+reservation fails. This is enforced by the verifier.
+.TP
+.B Return
+0 on success, or a negative error in case of failure.
+.UNINDENT
+.TP
+.B \fBvoid bpf_ringbuf_submit_dynptr(struct bpf_dynptr *\fP\fIptr\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Submit reserved ring buffer sample, pointed to by \fIdata\fP,
+through the dynptr interface. This is a no\-op if the dynptr is
+invalid/null.
+.sp
+For more information on \fIflags\fP, please see
+\(aqbpf_ringbuf_submit\(aq.
+.TP
+.B Return
+Nothing. Always succeeds.
+.UNINDENT
+.TP
+.B \fBvoid bpf_ringbuf_discard_dynptr(struct bpf_dynptr *\fP\fIptr\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Discard reserved ring buffer sample through the dynptr
+interface. This is a no\-op if the dynptr is invalid/null.
+.sp
+For more information on \fIflags\fP, please see
+\(aqbpf_ringbuf_discard\(aq.
+.TP
+.B Return
+Nothing. Always succeeds.
+.UNINDENT
+.TP
+.B \fBlong bpf_dynptr_read(void *\fP\fIdst\fP\fB, u32\fP \fIlen\fP\fB, const struct bpf_dynptr *\fP\fIsrc\fP\fB, u32\fP \fIoffset\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Read \fIlen\fP bytes from \fIsrc\fP into \fIdst\fP, starting from \fIoffset\fP
+into \fIsrc\fP\&.
+\fIflags\fP is currently unused.
+.TP
+.B Return
+0 on success, \-E2BIG if \fIoffset\fP + \fIlen\fP exceeds the length
+of \fIsrc\fP\(aqs data, \-EINVAL if \fIsrc\fP is an invalid dynptr or if
+\fIflags\fP is not 0.
+.UNINDENT
+.TP
+.B \fBlong bpf_dynptr_write(const struct bpf_dynptr *\fP\fIdst\fP\fB, u32\fP \fIoffset\fP\fB, void *\fP\fIsrc\fP\fB, u32\fP \fIlen\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Write \fIlen\fP bytes from \fIsrc\fP into \fIdst\fP, starting from \fIoffset\fP
+into \fIdst\fP\&.
+\fIflags\fP is currently unused.
+.TP
+.B Return
+0 on success, \-E2BIG if \fIoffset\fP + \fIlen\fP exceeds the length
+of \fIdst\fP\(aqs data, \-EINVAL if \fIdst\fP is an invalid dynptr or if \fIdst\fP
+is a read\-only dynptr or if \fIflags\fP is not 0.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_dynptr_data(const struct bpf_dynptr *\fP\fIptr\fP\fB, u32\fP \fIoffset\fP\fB, u32\fP \fIlen\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get a pointer to the underlying dynptr data.
+.sp
+\fIlen\fP must be a statically known value. The returned data slice
+is invalidated whenever the dynptr is invalidated.
+.TP
+.B Return
+Pointer to the underlying dynptr data, NULL if the dynptr is
+read\-only, if the dynptr is invalid, or if the offset and length
+is out of bounds.
+.UNINDENT
+.TP
+.B \fBs64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *\fP\fIiph\fP\fB, struct tcphdr *\fP\fIth\fP\fB, u32\fP \fIth_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Try to issue a SYN cookie for the packet with corresponding
+IPv4/TCP headers, \fIiph\fP and \fIth\fP, without depending on a
+listening socket.
+.sp
+\fIiph\fP points to the IPv4 header.
+.sp
+\fIth\fP points to the start of the TCP header, while \fIth_len\fP
+contains the length of the TCP header (at least
+\fBsizeof\fP(\fBstruct tcphdr\fP)).
+.TP
+.B 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.
+.sp
+On failure, the returned value is one of the following:
+.sp
+\fB\-EINVAL\fP if \fIth_len\fP is invalid.
+.UNINDENT
+.TP
+.B \fBs64 bpf_tcp_raw_gen_syncookie_ipv6(struct ipv6hdr *\fP\fIiph\fP\fB, struct tcphdr *\fP\fIth\fP\fB, u32\fP \fIth_len\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Try to issue a SYN cookie for the packet with corresponding
+IPv6/TCP headers, \fIiph\fP and \fIth\fP, without depending on a
+listening socket.
+.sp
+\fIiph\fP points to the IPv6 header.
+.sp
+\fIth\fP points to the start of the TCP header, while \fIth_len\fP
+contains the length of the TCP header (at least
+\fBsizeof\fP(\fBstruct tcphdr\fP)).
+.TP
+.B 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.
+.sp
+On failure, the returned value is one of the following:
+.sp
+\fB\-EINVAL\fP if \fIth_len\fP is invalid.
+.sp
+\fB\-EPROTONOSUPPORT\fP if CONFIG_IPV6 is not builtin.
+.UNINDENT
+.TP
+.B \fBlong bpf_tcp_raw_check_syncookie_ipv4(struct iphdr *\fP\fIiph\fP\fB, struct tcphdr *\fP\fIth\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Check whether \fIiph\fP and \fIth\fP contain a valid SYN cookie ACK
+without depending on a listening socket.
+.sp
+\fIiph\fP points to the IPv4 header.
+.sp
+\fIth\fP points to the TCP header.
+.TP
+.B Return
+0 if \fIiph\fP and \fIth\fP are a valid SYN cookie ACK.
+.sp
+On failure, the returned value is one of the following:
+.sp
+\fB\-EACCES\fP if the SYN cookie is not valid.
+.UNINDENT
+.TP
+.B \fBlong bpf_tcp_raw_check_syncookie_ipv6(struct ipv6hdr *\fP\fIiph\fP\fB, struct tcphdr *\fP\fIth\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Check whether \fIiph\fP and \fIth\fP contain a valid SYN cookie ACK
+without depending on a listening socket.
+.sp
+\fIiph\fP points to the IPv6 header.
+.sp
+\fIth\fP points to the TCP header.
+.TP
+.B Return
+0 if \fIiph\fP and \fIth\fP are a valid SYN cookie ACK.
+.sp
+On failure, the returned value is one of the following:
+.sp
+\fB\-EACCES\fP if the SYN cookie is not valid.
+.sp
+\fB\-EPROTONOSUPPORT\fP if CONFIG_IPV6 is not builtin.
+.UNINDENT
+.TP
+.B \fBu64 bpf_ktime_get_tai_ns(void)\fP
+.INDENT 7.0
+.TP
+.B Description
+A nonsettable system\-wide clock derived from wall\-clock time but
+ignoring leap seconds.  This clock does not experience
+discontinuities and backwards jumps caused by NTP inserting leap
+seconds as CLOCK_REALTIME does.
+.sp
+See: \fBclock_gettime\fP(\fBCLOCK_TAI\fP)
+.TP
+.B Return
+Current \fIktime\fP\&.
+.UNINDENT
+.TP
+.B \fBlong bpf_user_ringbuf_drain(struct bpf_map *\fP\fImap\fP\fB, void *\fP\fIcallback_fn\fP\fB, void *\fP\fIctx\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Drain samples from the specified user ring buffer, and invoke
+the provided callback for each such sample:
+.sp
+long (*callback_fn)(const struct bpf_dynptr *dynptr, void *ctx);
+.sp
+If \fBcallback_fn\fP returns 0, the helper will continue to try
+and drain the next sample, up to a maximum of
+BPF_MAX_USER_RINGBUF_SAMPLES samples. If the return value is 1,
+the helper will skip the rest of the samples and return. Other
+return values are not used now, and will be rejected by the
+verifier.
+.TP
+.B Return
+The number of drained samples if no error was encountered while
+draining samples, or 0 if no samples were present in the ring
+buffer. If a user\-space producer was epoll\-waiting on this map,
+and at least one sample was drained, they will receive an event
+notification notifying them of available space in the ring
+buffer. If the BPF_RB_NO_WAKEUP flag is passed to this
+function, no wakeup notification will be sent. If the
+BPF_RB_FORCE_WAKEUP flag is passed, a wakeup notification will
+be sent even if no sample was drained.
+.sp
+On failure, the returned value is one of the following:
+.sp
+\fB\-EBUSY\fP if the ring buffer is contended, and another calling
+context was concurrently draining the ring buffer.
+.sp
+\fB\-EINVAL\fP if user\-space is not properly tracking the ring
+buffer due to the producer position not being aligned to 8
+bytes, a sample not being aligned to 8 bytes, or the producer
+position not matching the advertised length of a sample.
+.sp
+\fB\-E2BIG\fP if user\-space has tried to publish a sample which is
+larger than the size of the ring buffer, or which cannot fit
+within a struct bpf_dynptr.
+.UNINDENT
+.TP
+.B \fBvoid *bpf_cgrp_storage_get(struct bpf_map *\fP\fImap\fP\fB, struct cgroup *\fP\fIcgroup\fP\fB, void *\fP\fIvalue\fP\fB, u64\fP \fIflags\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Get a bpf_local_storage from the \fIcgroup\fP\&.
+.sp
+Logically, it could be thought of as getting the value from
+a \fImap\fP with \fIcgroup\fP as the \fBkey\fP\&.  From this
+perspective,  the usage is not much different from
+\fBbpf_map_lookup_elem\fP(\fImap\fP, \fB&\fP\fIcgroup\fP) except this
+helper enforces the key must be a cgroup struct and the map must also
+be a \fBBPF_MAP_TYPE_CGRP_STORAGE\fP\&.
+.sp
+In reality, the local\-storage value is embedded directly inside of the
+\fIcgroup\fP object itself, rather than being located in the
+\fBBPF_MAP_TYPE_CGRP_STORAGE\fP map. When the local\-storage value is
+queried for some \fImap\fP on a \fIcgroup\fP object, the kernel will perform an
+O(n) iteration over all of the live local\-storage values for that
+\fIcgroup\fP object until the local\-storage value for the \fImap\fP is found.
+.sp
+An optional \fIflags\fP (\fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP) can be
+used such that a new bpf_local_storage will be
+created if one does not exist.  \fIvalue\fP can be used
+together with \fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP to specify
+the initial value of a bpf_local_storage.  If \fIvalue\fP is
+\fBNULL\fP, the new bpf_local_storage will be zero initialized.
+.TP
+.B Return
+A bpf_local_storage pointer is returned on success.
+.sp
+\fBNULL\fP if not found or there was an error in adding
+a new bpf_local_storage.
+.UNINDENT
+.TP
+.B \fBlong bpf_cgrp_storage_delete(struct bpf_map *\fP\fImap\fP\fB, struct cgroup *\fP\fIcgroup\fP\fB)\fP
+.INDENT 7.0
+.TP
+.B Description
+Delete a bpf_local_storage from a \fIcgroup\fP\&.
+.TP
+.B Return
+0 on success.
+.sp
+\fB\-ENOENT\fP if the bpf_local_storage cannot be found.
+.UNINDENT
+.UNINDENT
+.SH EXAMPLES
+.sp
+Example usage for most of the eBPF helpers listed in this manual page are
+available within the Linux kernel sources, at the following locations:
+.INDENT 0.0
+.IP \(bu 2
+\fIsamples/bpf/\fP
+.IP \(bu 2
+\fItools/testing/selftests/bpf/\fP
+.UNINDENT
+.SH LICENSE
+.sp
+eBPF programs can have an associated license, passed along with the bytecode
+instructions to the kernel when the programs are loaded. The format for that
+string is identical to the one in use for kernel modules (Dual licenses, such
+as \(dqDual BSD/GPL\(dq, may be used). Some helper functions are only accessible to
+programs that are compatible with the GNU Privacy License (GPL).
+.sp
+In order to use such helpers, the eBPF program must be loaded with the correct
+license string passed (via \fBattr\fP) to the \fBbpf\fP() system call, and this
+generally translates into the C source code of the program containing a line
+similar to the following:
+.INDENT 0.0
+.INDENT 3.5
+.sp
+.nf
+.ft C
+char ____license[] __attribute__((section(\(dqlicense\(dq), used)) = \(dqGPL\(dq;
+.ft P
+.fi
+.UNINDENT
+.UNINDENT
+.SH IMPLEMENTATION
+.sp
+This manual page is an effort to document the existing eBPF helper functions.
+But as of this writing, the BPF sub\-system is under heavy development. New eBPF
+program or map types are added, along with new helper functions. Some helpers
+are occasionally made available for additional program types. So in spite of
+the efforts of the community, this page might not be up\-to\-date. If you want to
+check by yourself what helper functions exist in your kernel, or what types of
+programs they can support, here are some files among the kernel tree that you
+may be interested in:
+.INDENT 0.0
+.IP \(bu 2
+\fIinclude/uapi/linux/bpf.h\fP is the main BPF header. It contains the full list
+of all helper functions, as well as many other BPF definitions including most
+of the flags, structs or constants used by the helpers.
+.IP \(bu 2
+\fInet/core/filter.c\fP contains the definition of most network\-related helper
+functions, and the list of program types from which they can be used.
+.IP \(bu 2
+\fIkernel/trace/bpf_trace.c\fP is the equivalent for most tracing program\-related
+helpers.
+.IP \(bu 2
+\fIkernel/bpf/verifier.c\fP contains the functions used to check that valid types
+of eBPF maps are used with a given helper function.
+.IP \(bu 2
+\fIkernel/bpf/\fP directory contains other files in which additional helpers are
+defined (for cgroups, sockmaps, etc.).
+.IP \(bu 2
+The bpftool utility can be used to probe the availability of helper functions
+on the system (as well as supported program and map types, and a number of
+other parameters). To do so, run \fBbpftool feature probe\fP (see
+\fBbpftool\-feature\fP(8) for details). Add the \fBunprivileged\fP keyword to
+list features available to unprivileged users.
+.UNINDENT
+.sp
+Compatibility between helper functions and program types can generally be found
+in the files where helper functions are defined. Look for the \fBstruct
+bpf_func_proto\fP objects and for functions returning them: these functions
+contain a list of helpers that a given program type can call. Note that the
+\fBdefault:\fP label of the \fBswitch ... case\fP used to filter helpers can call
+other functions, themselves allowing access to additional helpers. The
+requirement for GPL license is also in those \fBstruct bpf_func_proto\fP\&.
+.sp
+Compatibility between helper functions and map types can be found in the
+\fBcheck_map_func_compatibility\fP() function in file \fIkernel/bpf/verifier.c\fP\&.
+.sp
+Helper functions that invalidate the checks on \fBdata\fP and \fBdata_end\fP
+pointers for network processing are listed in function
+\fBbpf_helper_changes_pkt_data\fP() in file \fInet/core/filter.c\fP\&.
+.SH SEE ALSO
+.sp
+\fBbpf\fP(2),
+\fBbpftool\fP(8),
+\fBcgroups\fP(7),
+\fBip\fP(8),
+\fBperf_event_open\fP(2),
+\fBsendmsg\fP(2),
+\fBsocket\fP(7),
+\fBtc\-bpf\fP(8)
+.\" Generated by docutils manpage writer.
+.