text: /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
  /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of version 2 of the GNU General Public
   * License as published by the Free Software Foundation.
   */
  #ifndef _UAPI__LINUX_BPF_H__
  #define _UAPI__LINUX_BPF_H__
  
  #include <linux/types.h>
  #include <linux/bpf_common.h>
  
  /* Extended instruction set based on top of classic BPF */
  
  /* instruction classes */
  #define BPF_ALU64	0x07	/* alu mode in double word width */
  
  /* ld/ldx fields */
  #define BPF_DW		0x18	/* double word (64-bit) */
  #define BPF_XADD	0xc0	/* exclusive add */
  
  /* alu/jmp fields */
  #define BPF_MOV		0xb0	/* mov reg to reg */
  #define BPF_ARSH	0xc0	/* sign extending arithmetic shift right */
  
  /* change endianness of a register */
  #define BPF_END		0xd0	/* flags for endianness conversion: */
  #define BPF_TO_LE	0x00	/* convert to little-endian */
  #define BPF_TO_BE	0x08	/* convert to big-endian */
  #define BPF_FROM_LE	BPF_TO_LE
  #define BPF_FROM_BE	BPF_TO_BE
  
  /* jmp encodings */
  #define BPF_JNE		0x50	/* jump != */
  #define BPF_JLT		0xa0	/* LT is unsigned, '<' */
  #define BPF_JLE		0xb0	/* LE is unsigned, '<=' */
  #define BPF_JSGT	0x60	/* SGT is signed '>', GT in x86 */
  #define BPF_JSGE	0x70	/* SGE is signed '>=', GE in x86 */
  #define BPF_JSLT	0xc0	/* SLT is signed, '<' */
  #define BPF_JSLE	0xd0	/* SLE is signed, '<=' */
  #define BPF_CALL	0x80	/* function call */
  #define BPF_EXIT	0x90	/* function return */
  
  /* Register numbers */
  enum {
  	BPF_REG_0 = 0,
  	BPF_REG_1,
  	BPF_REG_2,
  	BPF_REG_3,
  	BPF_REG_4,
  	BPF_REG_5,
  	BPF_REG_6,
  	BPF_REG_7,
  	BPF_REG_8,
  	BPF_REG_9,
  	BPF_REG_10,
  	__MAX_BPF_REG,
  };
  
  /* BPF has 10 general purpose 64-bit registers and stack frame. */
  #define MAX_BPF_REG	__MAX_BPF_REG
  
  struct bpf_insn {
  	__u8	code;		/* opcode */
  	__u8	dst_reg:4;	/* dest register */
  	__u8	src_reg:4;	/* source register */
  	__s16	off;		/* signed offset */
  	__s32	imm;		/* signed immediate constant */
  };
  
  /* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */
  struct bpf_lpm_trie_key {
  	__u32	prefixlen;	/* up to 32 for AF_INET, 128 for AF_INET6 */
  	__u8	data[0];	/* Arbitrary size */
  };
  
  struct bpf_cgroup_storage_key {
  	__u64	cgroup_inode_id;	/* cgroup inode id */
  	__u32	attach_type;		/* program attach type */
  };
  
  /* BPF syscall commands, see bpf(2) man-page for details. */
  enum bpf_cmd {
  	BPF_MAP_CREATE,
  	BPF_MAP_LOOKUP_ELEM,
  	BPF_MAP_UPDATE_ELEM,
  	BPF_MAP_DELETE_ELEM,
  	BPF_MAP_GET_NEXT_KEY,
  	BPF_PROG_LOAD,
  	BPF_OBJ_PIN,
  	BPF_OBJ_GET,
  	BPF_PROG_ATTACH,
  	BPF_PROG_DETACH,
  	BPF_PROG_TEST_RUN,
  	BPF_PROG_GET_NEXT_ID,
  	BPF_MAP_GET_NEXT_ID,
  	BPF_PROG_GET_FD_BY_ID,
  	BPF_MAP_GET_FD_BY_ID,
  	BPF_OBJ_GET_INFO_BY_FD,
  	BPF_PROG_QUERY,
  	BPF_RAW_TRACEPOINT_OPEN,
  	BPF_BTF_LOAD,
  	BPF_BTF_GET_FD_BY_ID,
  	BPF_TASK_FD_QUERY,
  };
  
  enum bpf_map_type {
  	BPF_MAP_TYPE_UNSPEC,
  	BPF_MAP_TYPE_HASH,
  	BPF_MAP_TYPE_ARRAY,
  	BPF_MAP_TYPE_PROG_ARRAY,
  	BPF_MAP_TYPE_PERF_EVENT_ARRAY,
  	BPF_MAP_TYPE_PERCPU_HASH,
  	BPF_MAP_TYPE_PERCPU_ARRAY,
  	BPF_MAP_TYPE_STACK_TRACE,
  	BPF_MAP_TYPE_CGROUP_ARRAY,
  	BPF_MAP_TYPE_LRU_HASH,
  	BPF_MAP_TYPE_LRU_PERCPU_HASH,
  	BPF_MAP_TYPE_LPM_TRIE,
  	BPF_MAP_TYPE_ARRAY_OF_MAPS,
  	BPF_MAP_TYPE_HASH_OF_MAPS,
  	BPF_MAP_TYPE_DEVMAP,
  	BPF_MAP_TYPE_SOCKMAP,
  	BPF_MAP_TYPE_CPUMAP,
  	BPF_MAP_TYPE_XSKMAP,
  	BPF_MAP_TYPE_SOCKHASH,
  	BPF_MAP_TYPE_CGROUP_STORAGE,
  	BPF_MAP_TYPE_REUSEPORT_SOCKARRAY,
  };
  
  enum bpf_prog_type {
  	BPF_PROG_TYPE_UNSPEC,
  	BPF_PROG_TYPE_SOCKET_FILTER,
  	BPF_PROG_TYPE_KPROBE,
  	BPF_PROG_TYPE_SCHED_CLS,
  	BPF_PROG_TYPE_SCHED_ACT,
  	BPF_PROG_TYPE_TRACEPOINT,
  	BPF_PROG_TYPE_XDP,
  	BPF_PROG_TYPE_PERF_EVENT,
  	BPF_PROG_TYPE_CGROUP_SKB,
  	BPF_PROG_TYPE_CGROUP_SOCK,
  	BPF_PROG_TYPE_LWT_IN,
  	BPF_PROG_TYPE_LWT_OUT,
  	BPF_PROG_TYPE_LWT_XMIT,
  	BPF_PROG_TYPE_SOCK_OPS,
  	BPF_PROG_TYPE_SK_SKB,
  	BPF_PROG_TYPE_CGROUP_DEVICE,
  	BPF_PROG_TYPE_SK_MSG,
  	BPF_PROG_TYPE_RAW_TRACEPOINT,
  	BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
  	BPF_PROG_TYPE_LWT_SEG6LOCAL,
  	BPF_PROG_TYPE_LIRC_MODE2,
  	BPF_PROG_TYPE_SK_REUSEPORT,
  };
  
  enum bpf_attach_type {
  	BPF_CGROUP_INET_INGRESS,
  	BPF_CGROUP_INET_EGRESS,
  	BPF_CGROUP_INET_SOCK_CREATE,
  	BPF_CGROUP_SOCK_OPS,
  	BPF_SK_SKB_STREAM_PARSER,
  	BPF_SK_SKB_STREAM_VERDICT,
  	BPF_CGROUP_DEVICE,
  	BPF_SK_MSG_VERDICT,
  	BPF_CGROUP_INET4_BIND,
  	BPF_CGROUP_INET6_BIND,
  	BPF_CGROUP_INET4_CONNECT,
  	BPF_CGROUP_INET6_CONNECT,
  	BPF_CGROUP_INET4_POST_BIND,
  	BPF_CGROUP_INET6_POST_BIND,
  	BPF_CGROUP_UDP4_SENDMSG,
  	BPF_CGROUP_UDP6_SENDMSG,
  	BPF_LIRC_MODE2,
  	__MAX_BPF_ATTACH_TYPE
  };
  
  #define MAX_BPF_ATTACH_TYPE __MAX_BPF_ATTACH_TYPE
  
  /* cgroup-bpf attach flags used in BPF_PROG_ATTACH command
   *
   * NONE(default): No further bpf programs allowed in the subtree.
   *
   * BPF_F_ALLOW_OVERRIDE: If a sub-cgroup installs some bpf program,
   * the program in this cgroup yields to sub-cgroup program.
   *
   * BPF_F_ALLOW_MULTI: If a sub-cgroup installs some bpf program,
   * that cgroup program gets run in addition to the program in this cgroup.
   *
   * Only one program is allowed to be attached to a cgroup with
   * NONE or BPF_F_ALLOW_OVERRIDE flag.
   * Attaching another program on top of NONE or BPF_F_ALLOW_OVERRIDE will
   * release old program and attach the new one. Attach flags has to match.
   *
   * Multiple programs are allowed to be attached to a cgroup with
   * BPF_F_ALLOW_MULTI flag. They are executed in FIFO order
   * (those that were attached first, run first)
   * The programs of sub-cgroup are executed first, then programs of
   * this cgroup and then programs of parent cgroup.
   * When children program makes decision (like picking TCP CA or sock bind)
   * parent program has a chance to override it.
   *
   * A cgroup with MULTI or OVERRIDE flag allows any attach flags in sub-cgroups.
   * A cgroup with NONE doesn't allow any programs in sub-cgroups.
   * Ex1:
   * cgrp1 (MULTI progs A, B) ->
   *    cgrp2 (OVERRIDE prog C) ->
   *      cgrp3 (MULTI prog D) ->
   *        cgrp4 (OVERRIDE prog E) ->
   *          cgrp5 (NONE prog F)
   * the event in cgrp5 triggers execution of F,D,A,B in that order.
   * if prog F is detached, the execution is E,D,A,B
   * if prog F and D are detached, the execution is E,A,B
   * if prog F, E and D are detached, the execution is C,A,B
   *
   * All eligible programs are executed regardless of return code from
   * earlier programs.
   */
  #define BPF_F_ALLOW_OVERRIDE	(1U << 0)
  #define BPF_F_ALLOW_MULTI	(1U << 1)
  
  /* If BPF_F_STRICT_ALIGNMENT is used in BPF_PROG_LOAD command, the
   * verifier will perform strict alignment checking as if the kernel
   * has been built with CONFIG_EFFICIENT_UNALIGNED_ACCESS not set,
   * and NET_IP_ALIGN defined to 2.
   */
  #define BPF_F_STRICT_ALIGNMENT	(1U << 0)
  
  /* when bpf_ldimm64->src_reg == BPF_PSEUDO_MAP_FD, bpf_ldimm64->imm == fd */
  #define BPF_PSEUDO_MAP_FD	1
  
  /* when bpf_call->src_reg == BPF_PSEUDO_CALL, bpf_call->imm == pc-relative
   * offset to another bpf function
   */
  #define BPF_PSEUDO_CALL		1
  
  /* flags for BPF_MAP_UPDATE_ELEM command */
  #define BPF_ANY		0 /* create new element or update existing */
  #define BPF_NOEXIST	1 /* create new element if it didn't exist */
  #define BPF_EXIST	2 /* update existing element */
  
  /* flags for BPF_MAP_CREATE command */
  #define BPF_F_NO_PREALLOC	(1U << 0)
  /* Instead of having one common LRU list in the
   * BPF_MAP_TYPE_LRU_[PERCPU_]HASH map, use a percpu LRU list
   * which can scale and perform better.
   * Note, the LRU nodes (including free nodes) cannot be moved
   * across different LRU lists.
   */
  #define BPF_F_NO_COMMON_LRU	(1U << 1)
  /* Specify numa node during map creation */
  #define BPF_F_NUMA_NODE		(1U << 2)
  
  /* flags for BPF_PROG_QUERY */
  #define BPF_F_QUERY_EFFECTIVE	(1U << 0)
  
  #define BPF_OBJ_NAME_LEN 16U
  
  /* Flags for accessing BPF object */
  #define BPF_F_RDONLY		(1U << 3)
  #define BPF_F_WRONLY		(1U << 4)
  
  /* Flag for stack_map, store build_id+offset instead of pointer */
  #define BPF_F_STACK_BUILD_ID	(1U << 5)
  
  enum bpf_stack_build_id_status {
  	/* user space need an empty entry to identify end of a trace */
  	BPF_STACK_BUILD_ID_EMPTY = 0,
  	/* with valid build_id and offset */
  	BPF_STACK_BUILD_ID_VALID = 1,
  	/* couldn't get build_id, fallback to ip */
  	BPF_STACK_BUILD_ID_IP = 2,
  };
  
  #define BPF_BUILD_ID_SIZE 20
  struct bpf_stack_build_id {
  	__s32		status;
  	unsigned char	build_id[BPF_BUILD_ID_SIZE];
  	union {
  		__u64	offset;
  		__u64	ip;
  	};
  };
  
  union bpf_attr {
  	struct { /* anonymous struct used by BPF_MAP_CREATE command */
  		__u32	map_type;	/* one of enum bpf_map_type */
  		__u32	key_size;	/* size of key in bytes */
  		__u32	value_size;	/* size of value in bytes */
  		__u32	max_entries;	/* max number of entries in a map */
  		__u32	map_flags;	/* BPF_MAP_CREATE related
  					 * flags defined above.
  					 */
  		__u32	inner_map_fd;	/* fd pointing to the inner map */
  		__u32	numa_node;	/* numa node (effective only if
  					 * BPF_F_NUMA_NODE is set).
  					 */
  		char	map_name[BPF_OBJ_NAME_LEN];
  		__u32	map_ifindex;	/* ifindex of netdev to create on */
  		__u32	btf_fd;		/* fd pointing to a BTF type data */
  		__u32	btf_key_type_id;	/* BTF type_id of the key */
  		__u32	btf_value_type_id;	/* BTF type_id of the value */
  	};
  
  	struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
  		__u32		map_fd;
  		__aligned_u64	key;
  		union {
  			__aligned_u64 value;
  			__aligned_u64 next_key;
  		};
  		__u64		flags;
  	};
  
  	struct { /* anonymous struct used by BPF_PROG_LOAD command */
  		__u32		prog_type;	/* one of enum bpf_prog_type */
  		__u32		insn_cnt;
  		__aligned_u64	insns;
  		__aligned_u64	license;
  		__u32		log_level;	/* verbosity level of verifier */
  		__u32		log_size;	/* size of user buffer */
  		__aligned_u64	log_buf;	/* user supplied buffer */
  		__u32		kern_version;	/* checked when prog_type=kprobe */
  		__u32		prog_flags;
  		char		prog_name[BPF_OBJ_NAME_LEN];
  		__u32		prog_ifindex;	/* ifindex of netdev to prep for */
  		/* For some prog types expected attach type must be known at
  		 * load time to verify attach type specific parts of prog
  		 * (context accesses, allowed helpers, etc).
  		 */
  		__u32		expected_attach_type;
  	};
  
  	struct { /* anonymous struct used by BPF_OBJ_* commands */
  		__aligned_u64	pathname;
  		__u32		bpf_fd;
  		__u32		file_flags;
  	};
  
  	struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */
  		__u32		target_fd;	/* container object to attach to */
  		__u32		attach_bpf_fd;	/* eBPF program to attach */
  		__u32		attach_type;
  		__u32		attach_flags;
  	};
  
  	struct { /* anonymous struct used by BPF_PROG_TEST_RUN command */
  		__u32		prog_fd;
  		__u32		retval;
  		__u32		data_size_in;
  		__u32		data_size_out;
  		__aligned_u64	data_in;
  		__aligned_u64	data_out;
  		__u32		repeat;
  		__u32		duration;
  	} test;
  
  	struct { /* anonymous struct used by BPF_*_GET_*_ID */
  		union {
  			__u32		start_id;
  			__u32		prog_id;
  			__u32		map_id;
  			__u32		btf_id;
  		};
  		__u32		next_id;
  		__u32		open_flags;
  	};
  
  	struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */
  		__u32		bpf_fd;
  		__u32		info_len;
  		__aligned_u64	info;
  	} info;
  
  	struct { /* anonymous struct used by BPF_PROG_QUERY command */
  		__u32		target_fd;	/* container object to query */
  		__u32		attach_type;
  		__u32		query_flags;
  		__u32		attach_flags;
  		__aligned_u64	prog_ids;
  		__u32		prog_cnt;
  	} query;
  
  	struct {
  		__u64 name;
  		__u32 prog_fd;
  	} raw_tracepoint;
  
  	struct { /* anonymous struct for BPF_BTF_LOAD */
  		__aligned_u64	btf;
  		__aligned_u64	btf_log_buf;
  		__u32		btf_size;
  		__u32		btf_log_size;
  		__u32		btf_log_level;
  	};
  
  	struct {
  		__u32		pid;		/* input: pid */
  		__u32		fd;		/* input: fd */
  		__u32		flags;		/* input: flags */
  		__u32		buf_len;	/* input/output: buf len */
  		__aligned_u64	buf;		/* input/output:
  						 *   tp_name for tracepoint
  						 *   symbol for kprobe
  						 *   filename for uprobe
  						 */
  		__u32		prog_id;	/* output: prod_id */
  		__u32		fd_type;	/* output: BPF_FD_TYPE_* */
  		__u64		probe_offset;	/* output: probe_offset */
  		__u64		probe_addr;	/* output: probe_addr */
  	} task_fd_query;
  } __attribute__((aligned(8)));
  
  /* The description below is an attempt at providing documentation to eBPF
   * developers about the multiple available eBPF helper functions. It can be
   * parsed and used to produce a manual page. The workflow is the following,
   * and requires the rst2man utility:
   *
   *     $ ./scripts/bpf_helpers_doc.py \
   *             --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
   *     $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
   *     $ man /tmp/bpf-helpers.7
   *
   * Note that in order to produce this external documentation, some RST
   * formatting is used in the descriptions to get "bold" and "italics" in
   * manual pages. Also note that the few trailing white spaces are
   * intentional, removing them would break paragraphs for rst2man.
   *
   * Start of BPF helper function descriptions:
   *
   * void *bpf_map_lookup_elem(struct bpf_map *map, const void *key)
   * 	Description
   * 		Perform a lookup in *map* for an entry associated to *key*.
   * 	Return
   * 		Map value associated to *key*, or **NULL** if no entry was
   * 		found.
   *
   * int bpf_map_update_elem(struct bpf_map *map, const void *key, const void *value, u64 flags)
   * 	Description
   * 		Add or update the value of the entry associated to *key* in
   * 		*map* with *value*. *flags* is one of:
   *
   * 		**BPF_NOEXIST**
   * 			The entry for *key* must not exist in the map.
   * 		**BPF_EXIST**
   * 			The entry for *key* must already exist in the map.
   * 		**BPF_ANY**
   * 			No condition on the existence of the entry for *key*.
   *
   * 		Flag value **BPF_NOEXIST** cannot be used for maps of types
   * 		**BPF_MAP_TYPE_ARRAY** or **BPF_MAP_TYPE_PERCPU_ARRAY**  (all
   * 		elements always exist), the helper would return an error.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_map_delete_elem(struct bpf_map *map, const void *key)
   * 	Description
   * 		Delete entry with *key* from *map*.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_probe_read(void *dst, u32 size, const void *src)
   * 	Description
   * 		For tracing programs, safely attempt to read *size* bytes from
   * 		address *src* and store the data in *dst*.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * u64 bpf_ktime_get_ns(void)
   * 	Description
   * 		Return the time elapsed since system boot, in nanoseconds.
   * 	Return
   * 		Current *ktime*.
   *
   * int bpf_trace_printk(const char *fmt, u32 fmt_size, ...)
   * 	Description
   * 		This helper is a "printk()-like" facility for debugging. It
   * 		prints a message defined by format *fmt* (of size *fmt_size*)
   * 		to file *\/sys/kernel/debug/tracing/trace* from DebugFS, if
   * 		available. It can take up to three additional **u64**
   * 		arguments (as an eBPF helpers, the total number of arguments is
   * 		limited to five).
   *
   * 		Each time the helper is called, it appends a line to the trace.
   * 		The format of the trace is customizable, and the exact output
   * 		one will get depends on the options set in
   * 		*\/sys/kernel/debug/tracing/trace_options* (see also the
   * 		*README* file under the same directory). However, it usually
   * 		defaults to something like:
   *
   * 		::
   *
   * 			telnet-470   [001] .N.. 419421.045894: 0x00000001: <formatted msg>
   *
   * 		In the above:
   *
   * 			* ``telnet`` is the name of the current task.
   * 			* ``470`` is the PID of the current task.
   * 			* ``001`` is the CPU number on which the task is
   * 			  running.
   * 			* In ``.N..``, each character refers to a set of
   * 			  options (whether irqs are enabled, scheduling
   * 			  options, whether hard/softirqs are running, level of
   * 			  preempt_disabled respectively). **N** means that
   * 			  **TIF_NEED_RESCHED** and **PREEMPT_NEED_RESCHED**
   * 			  are set.
   * 			* ``419421.045894`` is a timestamp.
   * 			* ``0x00000001`` is a fake value used by BPF for the
   * 			  instruction pointer register.
   * 			* ``<formatted msg>`` is the message formatted with
   * 			  *fmt*.
   *
   * 		The conversion specifiers supported by *fmt* are similar, but
   * 		more limited than for printk(). They are **%d**, **%i**,
   * 		**%u**, **%x**, **%ld**, **%li**, **%lu**, **%lx**, **%lld**,
   * 		**%lli**, **%llu**, **%llx**, **%p**, **%s**. No modifier (size
   * 		of field, padding with zeroes, etc.) is available, and the
   * 		helper will return **-EINVAL** (but print nothing) if it
   * 		encounters an unknown specifier.
   *
   * 		Also, note that **bpf_trace_printk**\ () is slow, and should
   * 		only be used for debugging purposes. For this reason, a notice
   * 		bloc (spanning several lines) is printed to kernel logs and
   * 		states that the helper should not be used "for production use"
   * 		the first time this helper is used (or more precisely, when
   * 		**trace_printk**\ () buffers are allocated). For passing values
   * 		to user space, perf events should be preferred.
   * 	Return
   * 		The number of bytes written to the buffer, or a negative error
   * 		in case of failure.
   *
   * u32 bpf_get_prandom_u32(void)
   * 	Description
   * 		Get a pseudo-random number.
   *
   * 		From a security point of view, this helper uses its own
   * 		pseudo-random internal state, and cannot be used to infer the
   * 		seed of other random functions in the kernel. However, it is
   * 		essential to note that the generator used by the helper is not
   * 		cryptographically secure.
   * 	Return
   * 		A random 32-bit unsigned value.
   *
   * u32 bpf_get_smp_processor_id(void)
   * 	Description
   * 		Get the SMP (symmetric multiprocessing) processor id. Note that
   * 		all programs run with preemption disabled, which means that the
   * 		SMP processor id is stable during all the execution of the
   * 		program.
   * 	Return
   * 		The SMP id of the processor running the program.
   *
   * int bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len, u64 flags)
   * 	Description
   * 		Store *len* bytes from address *from* into the packet
   * 		associated to *skb*, at *offset*. *flags* are a combination of
   * 		**BPF_F_RECOMPUTE_CSUM** (automatically recompute the
   * 		checksum for the packet after storing the bytes) and
   * 		**BPF_F_INVALIDATE_HASH** (set *skb*\ **->hash**, *skb*\
   * 		**->swhash** and *skb*\ **->l4hash** to 0).
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_l3_csum_replace(struct sk_buff *skb, u32 offset, u64 from, u64 to, u64 size)
   * 	Description
   * 		Recompute the layer 3 (e.g. IP) checksum for the packet
   * 		associated to *skb*. Computation is incremental, so the helper
   * 		must know the former value of the header field that was
   * 		modified (*from*), the new value of this field (*to*), and the
   * 		number of bytes (2 or 4) for this field, stored in *size*.
   * 		Alternatively, it is possible to store the difference between
   * 		the previous and the new values of the header field in *to*, by
   * 		setting *from* and *size* to 0. For both methods, *offset*
   * 		indicates the location of the IP checksum within the packet.
   *
   * 		This helper works in combination with **bpf_csum_diff**\ (),
   * 		which does not update the checksum in-place, but offers more
   * 		flexibility and can handle sizes larger than 2 or 4 for the
   * 		checksum to update.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_l4_csum_replace(struct sk_buff *skb, u32 offset, u64 from, u64 to, u64 flags)
   * 	Description
   * 		Recompute the layer 4 (e.g. TCP, UDP or ICMP) checksum for the
   * 		packet associated to *skb*. Computation is incremental, so the
   * 		helper must know the former value of the header field that was
   * 		modified (*from*), the new value of this field (*to*), and the
   * 		number of bytes (2 or 4) for this field, stored on the lowest
   * 		four bits of *flags*. Alternatively, it is possible to store
   * 		the difference between the previous and the new values of the
   * 		header field in *to*, by setting *from* and the four lowest
   * 		bits of *flags* to 0. For both methods, *offset* indicates the
   * 		location of the IP checksum within the packet. In addition to
   * 		the size of the field, *flags* can be added (bitwise OR) actual
   * 		flags. With **BPF_F_MARK_MANGLED_0**, a null checksum is left
   * 		untouched (unless **BPF_F_MARK_ENFORCE** is added as well), and
   * 		for updates resulting in a null checksum the value is set to
   * 		**CSUM_MANGLED_0** instead. Flag **BPF_F_PSEUDO_HDR** indicates
   * 		the checksum is to be computed against a pseudo-header.
   *
   * 		This helper works in combination with **bpf_csum_diff**\ (),
   * 		which does not update the checksum in-place, but offers more
   * 		flexibility and can handle sizes larger than 2 or 4 for the
   * 		checksum to update.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_tail_call(void *ctx, struct bpf_map *prog_array_map, u32 index)
   * 	Description
   * 		This special helper is used to trigger a "tail call", or in
   * 		other words, to jump into another eBPF program. The same stack
   * 		frame is used (but values on stack and in registers for the
   * 		caller are not accessible to the callee). This mechanism allows
   * 		for program chaining, either for raising the maximum number of
   * 		available eBPF instructions, or to execute given programs in
   * 		conditional blocks. For security reasons, there is an upper
   * 		limit to the number of successive tail calls that can be
   * 		performed.
   *
   * 		Upon call of this helper, the program attempts to jump into a
   * 		program referenced at index *index* in *prog_array_map*, a
   * 		special map of type **BPF_MAP_TYPE_PROG_ARRAY**, and passes
   * 		*ctx*, a pointer to the context.
   *
   * 		If the call succeeds, the kernel immediately runs the first
   * 		instruction of the new program. This is not a function call,
   * 		and it never returns to the previous program. If the call
   * 		fails, then the helper has no effect, and the caller continues
   * 		to run its subsequent instructions. A call can fail if the
   * 		destination program for the jump does not exist (i.e. *index*
   * 		is superior to the number of entries in *prog_array_map*), or
   * 		if the maximum number of tail calls has been reached for this
   * 		chain of programs. This limit is defined in the kernel by the
   * 		macro **MAX_TAIL_CALL_CNT** (not accessible to user space),
   * 		which is currently set to 32.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_clone_redirect(struct sk_buff *skb, u32 ifindex, u64 flags)
   * 	Description
   * 		Clone and redirect the packet associated to *skb* to another
   * 		net device of index *ifindex*. Both ingress and egress
   * 		interfaces can be used for redirection. The **BPF_F_INGRESS**
   * 		value in *flags* is used to make the distinction (ingress path
   * 		is selected if the flag is present, egress path otherwise).
   * 		This is the only flag supported for now.
   *
   * 		In comparison with **bpf_redirect**\ () helper,
   * 		**bpf_clone_redirect**\ () has the associated cost of
   * 		duplicating the packet buffer, but this can be executed out of
   * 		the eBPF program. Conversely, **bpf_redirect**\ () is more
   * 		efficient, but it is handled through an action code where the
   * 		redirection happens only after the eBPF program has returned.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * u64 bpf_get_current_pid_tgid(void)
   * 	Return
   * 		A 64-bit integer containing the current tgid and pid, and
   * 		created as such:
   * 		*current_task*\ **->tgid << 32 \|**
   * 		*current_task*\ **->pid**.
   *
   * u64 bpf_get_current_uid_gid(void)
   * 	Return
   * 		A 64-bit integer containing the current GID and UID, and
   * 		created as such: *current_gid* **<< 32 \|** *current_uid*.
   *
   * int bpf_get_current_comm(char *buf, u32 size_of_buf)
   * 	Description
   * 		Copy the **comm** attribute of the current task into *buf* of
   * 		*size_of_buf*. The **comm** attribute contains the name of
   * 		the executable (excluding the path) for the current task. The
   * 		*size_of_buf* must be strictly positive. On success, the
   * 		helper makes sure that the *buf* is NUL-terminated. On failure,
   * 		it is filled with zeroes.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * u32 bpf_get_cgroup_classid(struct sk_buff *skb)
   * 	Description
   * 		Retrieve the classid for the current task, i.e. for the net_cls
   * 		cgroup to which *skb* belongs.
   *
   * 		This helper can be used on TC egress path, but not on ingress.
   *
   * 		The net_cls cgroup provides an interface to tag network packets
   * 		based on a user-provided identifier for all traffic coming from
   * 		the tasks belonging to the related cgroup. See also the related
   * 		kernel documentation, available from the Linux sources in file
   * 		*Documentation/cgroup-v1/net_cls.txt*.
   *
   * 		The Linux kernel has two versions for cgroups: there are
   * 		cgroups v1 and cgroups v2. Both are available to users, who can
   * 		use a mixture of them, but note that the net_cls cgroup is for
   * 		cgroup v1 only. This makes it incompatible with BPF programs
   * 		run on cgroups, which is a cgroup-v2-only feature (a socket can
   * 		only hold data for one version of cgroups at a time).
   *
   * 		This helper is only available is the kernel was compiled with
   * 		the **CONFIG_CGROUP_NET_CLASSID** configuration option set to
   * 		"**y**" or to "**m**".
   * 	Return
   * 		The classid, or 0 for the default unconfigured classid.
   *
   * int bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
   * 	Description
   * 		Push a *vlan_tci* (VLAN tag control information) of protocol
   * 		*vlan_proto* to the packet associated to *skb*, then update
   * 		the checksum. Note that if *vlan_proto* is different from
   * 		**ETH_P_8021Q** and **ETH_P_8021AD**, it is considered to
   * 		be **ETH_P_8021Q**.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_vlan_pop(struct sk_buff *skb)
   * 	Description
   * 		Pop a VLAN header from the packet associated to *skb*.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_get_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
   * 	Description
   * 		Get tunnel metadata. This helper takes a pointer *key* to an
   * 		empty **struct bpf_tunnel_key** of **size**, that will be
   * 		filled with tunnel metadata for the packet associated to *skb*.
   * 		The *flags* can be set to **BPF_F_TUNINFO_IPV6**, which
   * 		indicates that the tunnel is based on IPv6 protocol instead of
   * 		IPv4.
   *
   * 		The **struct bpf_tunnel_key** is an object that generalizes the
   * 		principal parameters used by various tunneling protocols into a
   * 		single struct. This way, it can be used to easily make a
   * 		decision based on the contents of the encapsulation header,
   * 		"summarized" in this struct. In particular, it holds the IP
   * 		address of the remote end (IPv4 or IPv6, depending on the case)
   * 		in *key*\ **->remote_ipv4** or *key*\ **->remote_ipv6**. Also,
   * 		this struct exposes the *key*\ **->tunnel_id**, which is
   * 		generally mapped to a VNI (Virtual Network Identifier), making
   * 		it programmable together with the **bpf_skb_set_tunnel_key**\
   * 		() helper.
   *
   * 		Let's imagine that the following code is part of a program
   * 		attached to the TC ingress interface, on one end of a GRE
   * 		tunnel, and is supposed to filter out all messages coming from
   * 		remote ends with IPv4 address other than 10.0.0.1:
   *
   * 		::
   *
   * 			int ret;
   * 			struct bpf_tunnel_key key = {};
   * 			
   * 			ret = bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
   * 			if (ret < 0)
   * 				return TC_ACT_SHOT;	// drop packet
   * 			
   * 			if (key.remote_ipv4 != 0x0a000001)
   * 				return TC_ACT_SHOT;	// drop packet
   * 			
   * 			return TC_ACT_OK;		// accept packet
   *
   * 		This interface can also be used with all encapsulation devices
   * 		that can operate in "collect metadata" mode: instead of having
   * 		one network device per specific configuration, the "collect
   * 		metadata" mode only requires a single device where the
   * 		configuration can be extracted from this helper.
   *
   * 		This can be used together with various tunnels such as VXLan,
   * 		Geneve, GRE or IP in IP (IPIP).
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_set_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
   * 	Description
   * 		Populate tunnel metadata for packet associated to *skb.* The
   * 		tunnel metadata is set to the contents of *key*, of *size*. The
   * 		*flags* can be set to a combination of the following values:
   *
   * 		**BPF_F_TUNINFO_IPV6**
   * 			Indicate that the tunnel is based on IPv6 protocol
   * 			instead of IPv4.
   * 		**BPF_F_ZERO_CSUM_TX**
   * 			For IPv4 packets, add a flag to tunnel metadata
   * 			indicating that checksum computation should be skipped
   * 			and checksum set to zeroes.
   * 		**BPF_F_DONT_FRAGMENT**
   * 			Add a flag to tunnel metadata indicating that the
   * 			packet should not be fragmented.
   * 		**BPF_F_SEQ_NUMBER**
   * 			Add a flag to tunnel metadata indicating that a
   * 			sequence number should be added to tunnel header before
   * 			sending the packet. This flag was added for GRE
   * 			encapsulation, but might be used with other protocols
   * 			as well in the future.
   *
   * 		Here is a typical usage on the transmit path:
   *
   * 		::
   *
   * 			struct bpf_tunnel_key key;
   * 			     populate key ...
   * 			bpf_skb_set_tunnel_key(skb, &key, sizeof(key), 0);
   * 			bpf_clone_redirect(skb, vxlan_dev_ifindex, 0);
   *
   * 		See also the description of the **bpf_skb_get_tunnel_key**\ ()
   * 		helper for additional information.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * u64 bpf_perf_event_read(struct bpf_map *map, u64 flags)
   * 	Description
   * 		Read the value of a perf event counter. This helper relies on a
   * 		*map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. The nature of
   * 		the perf event counter is selected when *map* is updated with
   * 		perf event file descriptors. The *map* is an array whose size
   * 		is the number of available CPUs, and each cell contains a value
   * 		relative to one CPU. The value to retrieve is indicated by
   * 		*flags*, that contains the index of the CPU to look up, masked
   * 		with **BPF_F_INDEX_MASK**. Alternatively, *flags* can be set to
   * 		**BPF_F_CURRENT_CPU** to indicate that the value for the
   * 		current CPU should be retrieved.
   *
   * 		Note that before Linux 4.13, only hardware perf event can be
   * 		retrieved.
   *
   * 		Also, be aware that the newer helper
   * 		**bpf_perf_event_read_value**\ () is recommended over
   * 		**bpf_perf_event_read**\ () in general. The latter has some ABI
   * 		quirks where error and counter value are used as a return code
   * 		(which is wrong to do since ranges may overlap). This issue is
   * 		fixed with **bpf_perf_event_read_value**\ (), which at the same
   * 		time provides more features over the **bpf_perf_event_read**\
   * 		() interface. Please refer to the description of
   * 		**bpf_perf_event_read_value**\ () for details.
   * 	Return
   * 		The value of the perf event counter read from the map, or a
   * 		negative error code in case of failure.
   *
   * int bpf_redirect(u32 ifindex, u64 flags)
   * 	Description
   * 		Redirect the packet to another net device of index *ifindex*.
   * 		This helper is somewhat similar to **bpf_clone_redirect**\
   * 		(), except that the packet is not cloned, which provides
   * 		increased performance.
   *
   * 		Except for XDP, both ingress and egress interfaces can be used
   * 		for redirection. The **BPF_F_INGRESS** value in *flags* is used
   * 		to make the distinction (ingress path is selected if the flag
   * 		is present, egress path otherwise). Currently, XDP only
   * 		supports redirection to the egress interface, and accepts no
   * 		flag at all.
   *
   * 		The same effect can be attained with the more generic
   * 		**bpf_redirect_map**\ (), which requires specific maps to be
   * 		used but offers better performance.
   * 	Return
   * 		For XDP, the helper returns **XDP_REDIRECT** on success or
   * 		**XDP_ABORTED** on error. For other program types, the values
   * 		are **TC_ACT_REDIRECT** on success or **TC_ACT_SHOT** on
   * 		error.
   *
   * u32 bpf_get_route_realm(struct sk_buff *skb)
   * 	Description
   * 		Retrieve the realm or the route, that is to say the
   * 		**tclassid** field of the destination for the *skb*. The
   * 		indentifier retrieved is a user-provided tag, similar to the
   * 		one used with the net_cls cgroup (see description for
   * 		**bpf_get_cgroup_classid**\ () helper), but here this tag is
   * 		held by a route (a destination entry), not by a task.
   *
   * 		Retrieving this identifier works with the clsact TC egress hook
   * 		(see also **tc-bpf(8)**), or alternatively on conventional
   * 		classful egress qdiscs, but not on TC ingress path. In case of
   * 		clsact TC egress hook, this has the advantage that, internally,
   * 		the destination entry has not been dropped yet in the transmit
   * 		path. Therefore, the destination entry does not need to be
   * 		artificially held via **netif_keep_dst**\ () for a classful
   * 		qdisc until the *skb* is freed.
   *
   * 		This helper is available only if the kernel was compiled with
   * 		**CONFIG_IP_ROUTE_CLASSID** configuration option.
   * 	Return
   * 		The realm of the route for the packet associated to *skb*, or 0
   * 		if none was found.
   *
   * int bpf_perf_event_output(struct pt_reg *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
   * 	Description
   * 		Write raw *data* blob into a special BPF perf event held by
   * 		*map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf
   * 		event must have the following attributes: **PERF_SAMPLE_RAW**
   * 		as **sample_type**, **PERF_TYPE_SOFTWARE** as **type**, and
   * 		**PERF_COUNT_SW_BPF_OUTPUT** as **config**.
   *
   * 		The *flags* are used to indicate the index in *map* for which
   * 		the value must be put, masked with **BPF_F_INDEX_MASK**.
   * 		Alternatively, *flags* can be set to **BPF_F_CURRENT_CPU**
   * 		to indicate that the index of the current CPU core should be
   * 		used.
   *
   * 		The value to write, of *size*, is passed through eBPF stack and
   * 		pointed by *data*.
   *
   * 		The context of the program *ctx* needs also be passed to the
   * 		helper.
   *
   * 		On user space, a program willing to read the values needs to
   * 		call **perf_event_open**\ () on the perf event (either for
   * 		one or for all CPUs) and to store the file descriptor into the
   * 		*map*. This must be done before the eBPF program can send data
   * 		into it. An example is available in file
   * 		*samples/bpf/trace_output_user.c* in the Linux kernel source
   * 		tree (the eBPF program counterpart is in
   * 		*samples/bpf/trace_output_kern.c*).
   *
   * 		**bpf_perf_event_output**\ () achieves better performance
   * 		than **bpf_trace_printk**\ () for sharing data with user
   * 		space, and is much better suitable for streaming data from eBPF
   * 		programs.
   *
   * 		Note that this helper is not restricted to tracing use cases
   * 		and can be used with programs attached to TC or XDP as well,
   * 		where it allows for passing data to user space listeners. Data
   * 		can be:
   *
   * 		* Only custom structs,
   * 		* Only the packet payload, or
   * 		* A combination of both.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void *to, u32 len)
   * 	Description
   * 		This helper was provided as an easy way to load data from a
   * 		packet. It can be used to load *len* bytes from *offset* from
   * 		the packet associated to *skb*, into the buffer pointed by
   * 		*to*.
   *
   * 		Since Linux 4.7, usage of this helper has mostly been replaced
   * 		by "direct packet access", enabling packet data to be
   * 		manipulated with *skb*\ **->data** and *skb*\ **->data_end**
   * 		pointing respectively to the first byte of packet data and to
   * 		the byte after the last byte of packet data. However, it
   * 		remains useful if one wishes to read large quantities of data
   * 		at once from a packet into the eBPF stack.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_get_stackid(struct pt_reg *ctx, struct bpf_map *map, u64 flags)
   * 	Description
   * 		Walk a user or a kernel stack and return its id. To achieve
   * 		this, the helper needs *ctx*, which is a pointer to the context
   * 		on which the tracing program is executed, and a pointer to a
   * 		*map* of type **BPF_MAP_TYPE_STACK_TRACE**.
   *
   * 		The last argument, *flags*, holds the number of stack frames to
   * 		skip (from 0 to 255), masked with
   * 		**BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
   * 		a combination of the following flags:
   *
   * 		**BPF_F_USER_STACK**
   * 			Collect a user space stack instead of a kernel stack.
   * 		**BPF_F_FAST_STACK_CMP**
   * 			Compare stacks by hash only.
   * 		**BPF_F_REUSE_STACKID**
   * 			If two different stacks hash into the same *stackid*,
   * 			discard the old one.
   *
   * 		The stack id retrieved is a 32 bit long integer handle which
   * 		can be further combined with other data (including other stack
   * 		ids) and used as a key into maps. This can be useful for
   * 		generating a variety of graphs (such as flame graphs or off-cpu
   * 		graphs).
   *
   * 		For walking a stack, this helper is an improvement over
   * 		**bpf_probe_read**\ (), which can be used with unrolled loops
   * 		but is not efficient and consumes a lot of eBPF instructions.
   * 		Instead, **bpf_get_stackid**\ () can collect up to
   * 		**PERF_MAX_STACK_DEPTH** both kernel and user frames. Note that
   * 		this limit can be controlled with the **sysctl** program, and
   * 		that it should be manually increased in order to profile long
   * 		user stacks (such as stacks for Java programs). To do so, use:
   *
   * 		::
   *
   * 			# sysctl kernel.perf_event_max_stack=<new value>
   * 	Return
   * 		The positive or null stack id on success, or a negative error
   * 		in case of failure.
   *
   * s64 bpf_csum_diff(__be32 *from, u32 from_size, __be32 *to, u32 to_size, __wsum seed)
   * 	Description
   * 		Compute a checksum difference, from the raw buffer pointed by
   * 		*from*, of length *from_size* (that must be a multiple of 4),
   * 		towards the raw buffer pointed by *to*, of size *to_size*
   * 		(same remark). An optional *seed* can be added to the value
   * 		(this can be cascaded, the seed may come from a previous call
   * 		to the helper).
   *
   * 		This is flexible enough to be used in several ways:
   *
   * 		* With *from_size* == 0, *to_size* > 0 and *seed* set to
   * 		  checksum, it can be used when pushing new data.
   * 		* With *from_size* > 0, *to_size* == 0 and *seed* set to
   * 		  checksum, it can be used when removing data from a packet.
   * 		* With *from_size* > 0, *to_size* > 0 and *seed* set to 0, it
   * 		  can be used to compute a diff. Note that *from_size* and
   * 		  *to_size* do not need to be equal.
   *
   * 		This helper can be used in combination with
   * 		**bpf_l3_csum_replace**\ () and **bpf_l4_csum_replace**\ (), to
   * 		which one can feed in the difference computed with
   * 		**bpf_csum_diff**\ ().
   * 	Return
   * 		The checksum result, or a negative error code in case of
   * 		failure.
   *
   * int bpf_skb_get_tunnel_opt(struct sk_buff *skb, u8 *opt, u32 size)
   * 	Description
   * 		Retrieve tunnel options metadata for the packet associated to
   * 		*skb*, and store the raw tunnel option data to the buffer *opt*
   * 		of *size*.
   *
   * 		This helper can be used with encapsulation devices that can
   * 		operate in "collect metadata" mode (please refer to the related
   * 		note in the description of **bpf_skb_get_tunnel_key**\ () for
   * 		more details). A particular example where this can be used is
   * 		in combination with the Geneve encapsulation protocol, where it
   * 		allows for pushing (with **bpf_skb_get_tunnel_opt**\ () helper)
   * 		and retrieving arbitrary TLVs (Type-Length-Value headers) from
   * 		the eBPF program. This allows for full customization of these
   * 		headers.
   * 	Return
   * 		The size of the option data retrieved.
   *
   * int bpf_skb_set_tunnel_opt(struct sk_buff *skb, u8 *opt, u32 size)
   * 	Description
   * 		Set tunnel options metadata for the packet associated to *skb*
   * 		to the option data contained in the raw buffer *opt* of *size*.
   *
   * 		See also the description of the **bpf_skb_get_tunnel_opt**\ ()
   * 		helper for additional information.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_change_proto(struct sk_buff *skb, __be16 proto, u64 flags)
   * 	Description
   * 		Change the protocol of the *skb* to *proto*. Currently
   * 		supported are transition from IPv4 to IPv6, and from IPv6 to
   * 		IPv4. The helper takes care of the groundwork for the
   * 		transition, including resizing the socket buffer. The eBPF
   * 		program is expected to fill the new headers, if any, via
   * 		**skb_store_bytes**\ () and to recompute the checksums with
   * 		**bpf_l3_csum_replace**\ () and **bpf_l4_csum_replace**\
   * 		(). The main case for this helper is to perform NAT64
   * 		operations out of an eBPF program.
   *
   * 		Internally, the GSO type is marked as dodgy so that headers are
   * 		checked and segments are recalculated by the GSO/GRO engine.
   * 		The size for GSO target is adapted as well.
   *
   * 		All values for *flags* are reserved for future usage, and must
   * 		be left at zero.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_change_type(struct sk_buff *skb, u32 type)
   * 	Description
   * 		Change the packet type for the packet associated to *skb*. This
   * 		comes down to setting *skb*\ **->pkt_type** to *type*, except
   * 		the eBPF program does not have a write access to *skb*\
   * 		**->pkt_type** beside this helper. Using a helper here allows
   * 		for graceful handling of errors.
   *
   * 		The major use case is to change incoming *skb*s to
   * 		**PACKET_HOST** in a programmatic way instead of having to
   * 		recirculate via **redirect**\ (..., **BPF_F_INGRESS**), for
   * 		example.
   *
   * 		Note that *type* only allows certain values. At this time, they
   * 		are:
   *
   * 		**PACKET_HOST**
   * 			Packet is for us.
   * 		**PACKET_BROADCAST**
   * 			Send packet to all.
   * 		**PACKET_MULTICAST**
   * 			Send packet to group.
   * 		**PACKET_OTHERHOST**
   * 			Send packet to someone else.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_under_cgroup(struct sk_buff *skb, struct bpf_map *map, u32 index)
   * 	Description
   * 		Check whether *skb* is a descendant of the cgroup2 held by
   * 		*map* of type **BPF_MAP_TYPE_CGROUP_ARRAY**, at *index*.
   * 	Return
   * 		The return value depends on the result of the test, and can be:
   *
   * 		* 0, if the *skb* failed the cgroup2 descendant test.
   * 		* 1, if the *skb* succeeded the cgroup2 descendant test.
   * 		* A negative error code, if an error occurred.
   *
   * u32 bpf_get_hash_recalc(struct sk_buff *skb)
   * 	Description
   * 		Retrieve the hash of the packet, *skb*\ **->hash**. If it is
   * 		not set, in particular if the hash was cleared due to mangling,
   * 		recompute this hash. Later accesses to the hash can be done
   * 		directly with *skb*\ **->hash**.
   *
   * 		Calling **bpf_set_hash_invalid**\ (), changing a packet
   * 		prototype with **bpf_skb_change_proto**\ (), or calling
   * 		**bpf_skb_store_bytes**\ () with the
   * 		**BPF_F_INVALIDATE_HASH** are actions susceptible to clear
   * 		the hash and to trigger a new computation for the next call to
   * 		**bpf_get_hash_recalc**\ ().
   * 	Return
   * 		The 32-bit hash.
   *
   * u64 bpf_get_current_task(void)
   * 	Return
   * 		A pointer to the current task struct.
   *
   * int bpf_probe_write_user(void *dst, const void *src, u32 len)
   * 	Description
   * 		Attempt in a safe way to write *len* bytes from the buffer
   * 		*src* to *dst* in memory. It only works for threads that are in
   * 		user context, and *dst* must be a valid user space address.
   *
   * 		This helper should not be used to implement any kind of
   * 		security mechanism because of TOC-TOU attacks, but rather to
   * 		debug, divert, and manipulate execution of semi-cooperative
   * 		processes.
   *
   * 		Keep in mind that this feature is meant for experiments, and it
   * 		has a risk of crashing the system and running programs.
   * 		Therefore, when an eBPF program using this helper is attached,
   * 		a warning including PID and process name is printed to kernel
   * 		logs.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_current_task_under_cgroup(struct bpf_map *map, u32 index)
   * 	Description
   * 		Check whether the probe is being run is the context of a given
   * 		subset of the cgroup2 hierarchy. The cgroup2 to test is held by
   * 		*map* of type **BPF_MAP_TYPE_CGROUP_ARRAY**, at *index*.
   * 	Return
   * 		The return value depends on the result of the test, and can be:
   *
   * 		* 0, if the *skb* task belongs to the cgroup2.
   * 		* 1, if the *skb* task does not belong to the cgroup2.
   * 		* A negative error code, if an error occurred.
   *
   * int bpf_skb_change_tail(struct sk_buff *skb, u32 len, u64 flags)
   * 	Description
   * 		Resize (trim or grow) the packet associated to *skb* to the
   * 		new *len*. The *flags* are reserved for future usage, and must
   * 		be left at zero.
   *
   * 		The basic idea is that the helper performs the needed work to
   * 		change the size of the packet, then the eBPF program rewrites
   * 		the rest via helpers like **bpf_skb_store_bytes**\ (),
   * 		**bpf_l3_csum_replace**\ (), **bpf_l3_csum_replace**\ ()
   * 		and others. This helper is a slow path utility intended for
   * 		replies with control messages. And because it is targeted for
   * 		slow path, the helper itself can afford to be slow: it
   * 		implicitly linearizes, unclones and drops offloads from the
   * 		*skb*.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_pull_data(struct sk_buff *skb, u32 len)
   * 	Description
   * 		Pull in non-linear data in case the *skb* is non-linear and not
   * 		all of *len* are part of the linear section. Make *len* bytes
   * 		from *skb* readable and writable. If a zero value is passed for
   * 		*len*, then the whole length of the *skb* is pulled.
   *
   * 		This helper is only needed for reading and writing with direct
   * 		packet access.
   *
   * 		For direct packet access, testing that offsets to access
   * 		are within packet boundaries (test on *skb*\ **->data_end**) is
   * 		susceptible to fail if offsets are invalid, or if the requested
   * 		data is in non-linear parts of the *skb*. On failure the
   * 		program can just bail out, or in the case of a non-linear
   * 		buffer, use a helper to make the data available. The
   * 		**bpf_skb_load_bytes**\ () helper is a first solution to access
   * 		the data. Another one consists in using **bpf_skb_pull_data**
   * 		to pull in once the non-linear parts, then retesting and
   * 		eventually access the data.
   *
   * 		At the same time, this also makes sure the *skb* is uncloned,
   * 		which is a necessary condition for direct write. As this needs
   * 		to be an invariant for the write part only, the verifier
   * 		detects writes and adds a prologue that is calling
   * 		**bpf_skb_pull_data()** to effectively unclone the *skb* from
   * 		the very beginning in case it is indeed cloned.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * s64 bpf_csum_update(struct sk_buff *skb, __wsum csum)
   * 	Description
   * 		Add the checksum *csum* into *skb*\ **->csum** in case the
   * 		driver has supplied a checksum for the entire packet into that
   * 		field. Return an error otherwise. This helper is intended to be
   * 		used in combination with **bpf_csum_diff**\ (), in particular
   * 		when the checksum needs to be updated after data has been
   * 		written into the packet through direct packet access.
   * 	Return
   * 		The checksum on success, or a negative error code in case of
   * 		failure.
   *
   * void bpf_set_hash_invalid(struct sk_buff *skb)
   * 	Description
   * 		Invalidate the current *skb*\ **->hash**. It can be used after
   * 		mangling on headers through direct packet access, in order to
   * 		indicate that the hash is outdated and to trigger a
   * 		recalculation the next time the kernel tries to access this
   * 		hash or when the **bpf_get_hash_recalc**\ () helper is called.
   *
   * int bpf_get_numa_node_id(void)
   * 	Description
   * 		Return the id of the current NUMA node. The primary use case
   * 		for this helper is the selection of sockets for the local NUMA
   * 		node, when the program is attached to sockets using the
   * 		**SO_ATTACH_REUSEPORT_EBPF** option (see also **socket(7)**),
   * 		but the helper is also available to other eBPF program types,
   * 		similarly to **bpf_get_smp_processor_id**\ ().
   * 	Return
   * 		The id of current NUMA node.
   *
   * int bpf_skb_change_head(struct sk_buff *skb, u32 len, u64 flags)
   * 	Description
   * 		Grows headroom of packet associated to *skb* and adjusts the
   * 		offset of the MAC header accordingly, adding *len* bytes of
   * 		space. It automatically extends and reallocates memory as
   * 		required.
   *
   * 		This helper can be used on a layer 3 *skb* to push a MAC header
   * 		for redirection into a layer 2 device.
   *
   * 		All values for *flags* are reserved for future usage, and must
   * 		be left at zero.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_xdp_adjust_head(struct xdp_buff *xdp_md, int delta)
   * 	Description
   * 		Adjust (move) *xdp_md*\ **->data** by *delta* bytes. Note that
   * 		it is possible to use a negative value for *delta*. This helper
   * 		can be used to prepare the packet for pushing or popping
   * 		headers.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_probe_read_str(void *dst, int size, const void *unsafe_ptr)
   * 	Description
   * 		Copy a NUL terminated string from an unsafe address
   * 		*unsafe_ptr* to *dst*. The *size* should include the
   * 		terminating NUL byte. In case the string length is smaller than
   * 		*size*, the target is not padded with further NUL bytes. If the
   * 		string length is larger than *size*, just *size*-1 bytes are
   * 		copied and the last byte is set to NUL.
   *
   * 		On success, the length of the copied string is returned. This
   * 		makes this helper useful in tracing programs for reading
   * 		strings, and more importantly to get its length at runtime. See
   * 		the following snippet:
   *
   * 		::
   *
   * 			SEC("kprobe/sys_open")
   * 			void bpf_sys_open(struct pt_regs *ctx)
   * 			{
   * 			        char buf[PATHLEN]; // PATHLEN is defined to 256
   * 			        int res = bpf_probe_read_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.
   * 			}
   *
   * 		In comparison, using **bpf_probe_read()** helper here instead
   * 		to read the string would require to estimate the length at
   * 		compile time, and would often result in copying more memory
   * 		than necessary.
   *
   * 		Another useful use case is when parsing individual process
   * 		arguments or individual environment variables navigating
   * 		*current*\ **->mm->arg_start** and *current*\
   * 		**->mm->env_start**: using this helper and the return value,
   * 		one can quickly iterate at the right offset of the memory area.
   * 	Return
   * 		On success, the strictly positive length of the string,
   * 		including the trailing NUL character. On error, a negative
   * 		value.
   *
   * u64 bpf_get_socket_cookie(struct sk_buff *skb)
   * 	Description
   * 		If the **struct sk_buff** pointed by *skb* has a known socket,
   * 		retrieve the cookie (generated by the kernel) of this socket.
   * 		If no cookie has been set yet, generate a new cookie. Once
   * 		generated, the socket cookie remains stable for the life of the
   * 		socket. This helper can be useful for monitoring per socket
   * 		networking traffic statistics as it provides a unique socket
   * 		identifier per namespace.
   * 	Return
   * 		A 8-byte long non-decreasing number on success, or 0 if the
   * 		socket field is missing inside *skb*.
   *
   * u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
   * 	Description
   * 		Equivalent to bpf_get_socket_cookie() helper that accepts
   * 		*skb*, but gets socket from **struct bpf_sock_addr** contex.
   * 	Return
   * 		A 8-byte long non-decreasing number.
   *
   * u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)
   * 	Description
   * 		Equivalent to bpf_get_socket_cookie() helper that accepts
   * 		*skb*, but gets socket from **struct bpf_sock_ops** contex.
   * 	Return
   * 		A 8-byte long non-decreasing number.
   *
   * u32 bpf_get_socket_uid(struct sk_buff *skb)
   * 	Return
   * 		The owner UID of the socket associated to *skb*. If the socket
   * 		is **NULL**, or if it is not a full socket (i.e. if it is a
   * 		time-wait or a request socket instead), **overflowuid** value
   * 		is returned (note that **overflowuid** might also be the actual
   * 		UID value for the socket).
   *
   * u32 bpf_set_hash(struct sk_buff *skb, u32 hash)
   * 	Description
   * 		Set the full hash for *skb* (set the field *skb*\ **->hash**)
   * 		to value *hash*.
   * 	Return
   * 		0
   *
   * int bpf_setsockopt(struct bpf_sock_ops *bpf_socket, int level, int optname, char *optval, int optlen)
   * 	Description
   * 		Emulate a call to **setsockopt()** on the socket associated to
   * 		*bpf_socket*, which must be a full socket. The *level* at
   * 		which the option resides and the name *optname* of the option
   * 		must be specified, see **setsockopt(2)** for more information.
   * 		The option value of length *optlen* is pointed by *optval*.
   *
   * 		This helper actually implements a subset of **setsockopt()**.
   * 		It supports the following *level*\ s:
   *
   * 		* **SOL_SOCKET**, which supports the following *optname*\ s:
   * 		  **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**,
   * 		  **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**.
   * 		* **IPPROTO_TCP**, which supports the following *optname*\ s:
   * 		  **TCP_CONGESTION**, **TCP_BPF_IW**,
   * 		  **TCP_BPF_SNDCWND_CLAMP**.
   * 		* **IPPROTO_IP**, which supports *optname* **IP_TOS**.
   * 		* **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_adjust_room(struct sk_buff *skb, u32 len_diff, u32 mode, u64 flags)
   * 	Description
   * 		Grow or shrink the room for data in the packet associated to
   * 		*skb* by *len_diff*, and according to the selected *mode*.
   *
   * 		There is a single supported mode at this time:
   *
   * 		* **BPF_ADJ_ROOM_NET**: Adjust room at the network layer
   * 		  (room space is added or removed below the layer 3 header).
   *
   * 		All values for *flags* are reserved for future usage, and must
   * 		be left at zero.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags)
   * 	Description
   * 		Redirect the packet to the endpoint referenced by *map* at
   * 		index *key*. Depending on its type, this *map* can contain
   * 		references to net devices (for forwarding packets through other
   * 		ports), or to CPUs (for redirecting XDP frames to another CPU;
   * 		but this is only implemented for native XDP (with driver
   * 		support) as of this writing).
   *
   * 		All values for *flags* are reserved for future usage, and must
   * 		be left at zero.
   *
   * 		When used to redirect packets to net devices, this helper
   * 		provides a high performance increase over **bpf_redirect**\ ().
   * 		This is due to various implementation details of the underlying
   * 		mechanisms, one of which is the fact that **bpf_redirect_map**\
   * 		() tries to send packet as a "bulk" to the device.
   * 	Return
   * 		**XDP_REDIRECT** on success, or **XDP_ABORTED** on error.
   *
   * int bpf_sk_redirect_map(struct bpf_map *map, u32 key, u64 flags)
   * 	Description
   * 		Redirect the packet to the socket referenced by *map* (of type
   * 		**BPF_MAP_TYPE_SOCKMAP**) at index *key*. Both ingress and
   * 		egress interfaces can be used for redirection. The
   * 		**BPF_F_INGRESS** value in *flags* is used to make the
   * 		distinction (ingress path is selected if the flag is present,
   * 		egress path otherwise). This is the only flag supported for now.
   * 	Return
   * 		**SK_PASS** on success, or **SK_DROP** on error.
   *
   * int bpf_sock_map_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags)
   * 	Description
   * 		Add an entry to, or update a *map* referencing sockets. The
   * 		*skops* is used as a new value for the entry associated to
   * 		*key*. *flags* is one of:
   *
   * 		**BPF_NOEXIST**
   * 			The entry for *key* must not exist in the map.
   * 		**BPF_EXIST**
   * 			The entry for *key* must already exist in the map.
   * 		**BPF_ANY**
   * 			No condition on the existence of the entry for *key*.
   *
   * 		If the *map* has eBPF programs (parser and verdict), those will
   * 		be inherited by the socket being added. If the socket is
   * 		already attached to eBPF programs, this results in an error.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_xdp_adjust_meta(struct xdp_buff *xdp_md, int delta)
   * 	Description
   * 		Adjust the address pointed by *xdp_md*\ **->data_meta** by
   * 		*delta* (which can be positive or negative). Note that this
   * 		operation modifies the address stored in *xdp_md*\ **->data**,
   * 		so the latter must be loaded only after the helper has been
   * 		called.
   *
   * 		The use of *xdp_md*\ **->data_meta** is optional and programs
   * 		are not required to use it. The rationale is that when the
   * 		packet is processed with XDP (e.g. as DoS filter), it is
   * 		possible to push further meta data along with it before passing
   * 		to the stack, and to give the guarantee that an ingress eBPF
   * 		program attached as a TC classifier on the same device can pick
   * 		this up for further post-processing. Since TC works with socket
   * 		buffers, it remains possible to set from XDP the **mark** or
   * 		**priority** pointers, or other pointers for the socket buffer.
   * 		Having this scratch space generic and programmable allows for
   * 		more flexibility as the user is free to store whatever meta
   * 		data they need.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_perf_event_read_value(struct bpf_map *map, u64 flags, struct bpf_perf_event_value *buf, u32 buf_size)
   * 	Description
   * 		Read the value of a perf event counter, and store it into *buf*
   * 		of size *buf_size*. This helper relies on a *map* of type
   * 		**BPF_MAP_TYPE_PERF_EVENT_ARRAY**. The nature of the perf event
   * 		counter is selected when *map* is updated with perf event file
   * 		descriptors. The *map* is an array whose size is the number of
   * 		available CPUs, and each cell contains a value relative to one
   * 		CPU. The value to retrieve is indicated by *flags*, that
   * 		contains the index of the CPU to look up, masked with
   * 		**BPF_F_INDEX_MASK**. Alternatively, *flags* can be set to
   * 		**BPF_F_CURRENT_CPU** to indicate that the value for the
   * 		current CPU should be retrieved.
   *
   * 		This helper behaves in a way close to
   * 		**bpf_perf_event_read**\ () helper, save that instead of
   * 		just returning the value observed, it fills the *buf*
   * 		structure. This allows for additional data to be retrieved: in
   * 		particular, the enabled and running times (in *buf*\
   * 		**->enabled** and *buf*\ **->running**, respectively) are
   * 		copied. In general, **bpf_perf_event_read_value**\ () is
   * 		recommended over **bpf_perf_event_read**\ (), which has some
   * 		ABI issues and provides fewer functionalities.
   *
   * 		These values are interesting, because hardware PMU (Performance
   * 		Monitoring Unit) counters are limited resources. When there are
   * 		more PMU based perf events opened than available counters,
   * 		kernel will multiplex these events so each event gets certain
   * 		percentage (but not all) of the PMU time. In case that
   * 		multiplexing happens, the number of samples or counter value
   * 		will not reflect the case compared to when no multiplexing
   * 		occurs. This makes comparison between different runs difficult.
   * 		Typically, the counter value should be normalized before
   * 		comparing to other experiments. The usual normalization is done
   * 		as follows.
   *
   * 		::
   *
   * 			normalized_counter = counter * t_enabled / t_running
   *
   * 		Where t_enabled is the time enabled for event and t_running is
   * 		the time running for event since last normalization. The
   * 		enabled and running times are accumulated since the perf event
   * 		open. To achieve scaling factor between two invocations of an
   * 		eBPF program, users can can use CPU id as the key (which is
   * 		typical for perf array usage model) to remember the previous
   * 		value and do the calculation inside the eBPF program.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_perf_prog_read_value(struct bpf_perf_event_data *ctx, struct bpf_perf_event_value *buf, u32 buf_size)
   * 	Description
   * 		For en eBPF program attached to a perf event, retrieve the
   * 		value of the event counter associated to *ctx* and store it in
   * 		the structure pointed by *buf* and of size *buf_size*. Enabled
   * 		and running times are also stored in the structure (see
   * 		description of helper **bpf_perf_event_read_value**\ () for
   * 		more details).
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_getsockopt(struct bpf_sock_ops *bpf_socket, int level, int optname, char *optval, int optlen)
   * 	Description
   * 		Emulate a call to **getsockopt()** on the socket associated to
   * 		*bpf_socket*, which must be a full socket. The *level* at
   * 		which the option resides and the name *optname* of the option
   * 		must be specified, see **getsockopt(2)** for more information.
   * 		The retrieved value is stored in the structure pointed by
   * 		*opval* and of length *optlen*.
   *
   * 		This helper actually implements a subset of **getsockopt()**.
   * 		It supports the following *level*\ s:
   *
   * 		* **IPPROTO_TCP**, which supports *optname*
   * 		  **TCP_CONGESTION**.
   * 		* **IPPROTO_IP**, which supports *optname* **IP_TOS**.
   * 		* **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_override_return(struct pt_reg *regs, u64 rc)
   * 	Description
   * 		Used for error injection, this helper uses kprobes to override
   * 		the return value of the probed function, and to set it to *rc*.
   * 		The first argument is the context *regs* on which the kprobe
   * 		works.
   *
   * 		This helper works by setting setting the PC (program counter)
   * 		to an override function which is run in place of the original
   * 		probed function. This means the probed function is not run at
   * 		all. The replacement function just returns with the required
   * 		value.
   *
   * 		This helper has security implications, and thus is subject to
   * 		restrictions. It is only available if the kernel was compiled
   * 		with the **CONFIG_BPF_KPROBE_OVERRIDE** configuration
   * 		option, and in this case it only works on functions tagged with
   * 		**ALLOW_ERROR_INJECTION** in the kernel code.
   *
   * 		Also, the helper is only available for the architectures having
   * 		the CONFIG_FUNCTION_ERROR_INJECTION option. As of this writing,
   * 		x86 architecture is the only one to support this feature.
   * 	Return
   * 		0
   *
   * int bpf_sock_ops_cb_flags_set(struct bpf_sock_ops *bpf_sock, int argval)
   * 	Description
   * 		Attempt to set the value of the **bpf_sock_ops_cb_flags** field
   * 		for the full TCP socket associated to *bpf_sock_ops* to
   * 		*argval*.
   *
   * 		The primary use of this field is to determine if there should
   * 		be calls to eBPF programs of type
   * 		**BPF_PROG_TYPE_SOCK_OPS** at various points in the TCP
   * 		code. A program of the same type can change its value, per
   * 		connection and as necessary, when the connection is
   * 		established. This field is directly accessible for reading, but
   * 		this helper must be used for updates in order to return an
   * 		error if an eBPF program tries to set a callback that is not
   * 		supported in the current kernel.
   *
   * 		The supported callback values that *argval* can combine are:
   *
   * 		* **BPF_SOCK_OPS_RTO_CB_FLAG** (retransmission time out)
   * 		* **BPF_SOCK_OPS_RETRANS_CB_FLAG** (retransmission)
   * 		* **BPF_SOCK_OPS_STATE_CB_FLAG** (TCP state change)
   *
   * 		Here are some examples of where one could call such eBPF
   * 		program:
   *
   * 		* When RTO fires.
   * 		* When a packet is retransmitted.
   * 		* When the connection terminates.
   * 		* When a packet is sent.
   * 		* When a packet is received.
   * 	Return
   * 		Code **-EINVAL** if the socket is not a full TCP socket;
   * 		otherwise, a positive number containing the bits that could not
   * 		be set is returned (which comes down to 0 if all bits were set
   * 		as required).
   *
   * int bpf_msg_redirect_map(struct sk_msg_buff *msg, struct bpf_map *map, u32 key, u64 flags)
   * 	Description
   * 		This helper is used in programs implementing policies at the
   * 		socket level. If the message *msg* is allowed to pass (i.e. if
   * 		the verdict eBPF program returns **SK_PASS**), redirect it to
   * 		the socket referenced by *map* (of type
   * 		**BPF_MAP_TYPE_SOCKMAP**) at index *key*. Both ingress and
   * 		egress interfaces can be used for redirection. The
   * 		**BPF_F_INGRESS** value in *flags* is used to make the
   * 		distinction (ingress path is selected if the flag is present,
   * 		egress path otherwise). This is the only flag supported for now.
   * 	Return
   * 		**SK_PASS** on success, or **SK_DROP** on error.
   *
   * int bpf_msg_apply_bytes(struct sk_msg_buff *msg, u32 bytes)
   * 	Description
   * 		For socket policies, apply the verdict of the eBPF program to
   * 		the next *bytes* (number of bytes) of message *msg*.
   *
   * 		For example, this helper can be used in the following cases:
   *
   * 		* A single **sendmsg**\ () or **sendfile**\ () system call
   * 		  contains multiple logical messages that the eBPF program is
   * 		  supposed to read and for which it should apply a verdict.
   * 		* An eBPF program only cares to read the first *bytes* of a
   * 		  *msg*. If the message has a large payload, then setting up
   * 		  and calling the eBPF program repeatedly for all bytes, even
   * 		  though the verdict is already known, would create unnecessary
   * 		  overhead.
   *
   * 		When called from within an eBPF program, the helper sets a
   * 		counter internal to the BPF infrastructure, that is used to
   * 		apply the last verdict to the next *bytes*. If *bytes* is
   * 		smaller than the current data being processed from a
   * 		**sendmsg**\ () or **sendfile**\ () system call, the first
   * 		*bytes* will be sent and the eBPF program will be re-run with
   * 		the pointer for start of data pointing to byte number *bytes*
   * 		**+ 1**. If *bytes* is larger than the current data being
   * 		processed, then the eBPF verdict will be applied to multiple
   * 		**sendmsg**\ () or **sendfile**\ () calls until *bytes* are
   * 		consumed.
   *
   * 		Note that if a socket closes with the internal counter holding
   * 		a non-zero value, this is not a problem because data is not
   * 		being buffered for *bytes* and is sent as it is received.
   * 	Return
   * 		0
   *
   * int bpf_msg_cork_bytes(struct sk_msg_buff *msg, u32 bytes)
   * 	Description
   * 		For socket policies, prevent the execution of the verdict eBPF
   * 		program for message *msg* until *bytes* (byte number) have been
   * 		accumulated.
   *
   * 		This can be used when one needs a specific number of bytes
   * 		before a verdict can be assigned, even if the data spans
   * 		multiple **sendmsg**\ () or **sendfile**\ () calls. The extreme
   * 		case would be a user calling **sendmsg**\ () repeatedly with
   * 		1-byte long message segments. Obviously, this is bad for
   * 		performance, but it is still valid. If the eBPF program needs
   * 		*bytes* bytes to validate a header, this helper can be used to
   * 		prevent the eBPF program to be called again until *bytes* have
   * 		been accumulated.
   * 	Return
   * 		0
   *
   * int bpf_msg_pull_data(struct sk_msg_buff *msg, u32 start, u32 end, u64 flags)
   * 	Description
   * 		For socket policies, pull in non-linear data from user space
   * 		for *msg* and set pointers *msg*\ **->data** and *msg*\
   * 		**->data_end** to *start* and *end* bytes offsets into *msg*,
   * 		respectively.
   *
   * 		If a program of type **BPF_PROG_TYPE_SK_MSG** is run on a
   * 		*msg* it can only parse data that the (**data**, **data_end**)
   * 		pointers have already consumed. For **sendmsg**\ () hooks this
   * 		is likely the first scatterlist element. But for calls relying
   * 		on the **sendpage** handler (e.g. **sendfile**\ ()) this will
   * 		be the range (**0**, **0**) because the data is shared with
   * 		user space and by default the objective is to avoid allowing
   * 		user space to modify data while (or after) eBPF verdict is
   * 		being decided. This helper can be used to pull in data and to
   * 		set the start and end pointer to given values. Data will be
   * 		copied if necessary (i.e. if data was not linear and if start
   * 		and end pointers do not point to the same chunk).
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   *
   * 		All values for *flags* are reserved for future usage, and must
   * 		be left at zero.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_bind(struct bpf_sock_addr *ctx, struct sockaddr *addr, int addr_len)
   * 	Description
   * 		Bind the socket associated to *ctx* to the address pointed by
   * 		*addr*, of length *addr_len*. This allows for making outgoing
   * 		connection from the desired IP address, which can be useful for
   * 		example when all processes inside a cgroup should use one
   * 		single IP address on a host that has multiple IP configured.
   *
   * 		This helper works for IPv4 and IPv6, TCP and UDP sockets. The
   * 		domain (*addr*\ **->sa_family**) must be **AF_INET** (or
   * 		**AF_INET6**). Looking for a free port to bind to can be
   * 		expensive, therefore binding to port is not permitted by the
   * 		helper: *addr*\ **->sin_port** (or **sin6_port**, respectively)
   * 		must be set to zero.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_xdp_adjust_tail(struct xdp_buff *xdp_md, int delta)
   * 	Description
   * 		Adjust (move) *xdp_md*\ **->data_end** by *delta* bytes. It is
   * 		only possible to shrink the packet as of this writing,
   * 		therefore *delta* must be a negative integer.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_skb_get_xfrm_state(struct sk_buff *skb, u32 index, struct bpf_xfrm_state *xfrm_state, u32 size, u64 flags)
   * 	Description
   * 		Retrieve the XFRM state (IP transform framework, see also
   * 		**ip-xfrm(8)**) at *index* in XFRM "security path" for *skb*.
   *
   * 		The retrieved value is stored in the **struct bpf_xfrm_state**
   * 		pointed by *xfrm_state* and of length *size*.
   *
   * 		All values for *flags* are reserved for future usage, and must
   * 		be left at zero.
   *
   * 		This helper is available only if the kernel was compiled with
   * 		**CONFIG_XFRM** configuration option.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_get_stack(struct pt_regs *regs, void *buf, u32 size, u64 flags)
   * 	Description
   * 		Return a user or a kernel stack in bpf program provided buffer.
   * 		To achieve this, the helper needs *ctx*, which is a pointer
   * 		to the context on which the tracing program is executed.
   * 		To store the stacktrace, the bpf program provides *buf* with
   * 		a nonnegative *size*.
   *
   * 		The last argument, *flags*, holds the number of stack frames to
   * 		skip (from 0 to 255), masked with
   * 		**BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
   * 		the following flags:
   *
   * 		**BPF_F_USER_STACK**
   * 			Collect a user space stack instead of a kernel stack.
   * 		**BPF_F_USER_BUILD_ID**
   * 			Collect buildid+offset instead of ips for user stack,
   * 			only valid if **BPF_F_USER_STACK** is also specified.
   *
   * 		**bpf_get_stack**\ () can collect up to
   * 		**PERF_MAX_STACK_DEPTH** both kernel and user frames, subject
   * 		to sufficient large buffer size. Note that
   * 		this limit can be controlled with the **sysctl** program, and
   * 		that it should be manually increased in order to profile long
   * 		user stacks (such as stacks for Java programs). To do so, use:
   *
   * 		::
   *
   * 			# sysctl kernel.perf_event_max_stack=<new value>
   * 	Return
   * 		A non-negative value equal to or less than *size* on success,
   * 		or a negative error in case of failure.
   *
   * int bpf_skb_load_bytes_relative(const struct sk_buff *skb, u32 offset, void *to, u32 len, u32 start_header)
   * 	Description
   * 		This helper is similar to **bpf_skb_load_bytes**\ () in that
   * 		it provides an easy way to load *len* bytes from *offset*
   * 		from the packet associated to *skb*, into the buffer pointed
   * 		by *to*. The difference to **bpf_skb_load_bytes**\ () is that
   * 		a fifth argument *start_header* exists in order to select a
   * 		base offset to start from. *start_header* can be one of:
   *
   * 		**BPF_HDR_START_MAC**
   * 			Base offset to load data from is *skb*'s mac header.
   * 		**BPF_HDR_START_NET**
   * 			Base offset to load data from is *skb*'s network header.
   *
   * 		In general, "direct packet access" is the preferred method to
   * 		access packet data, however, this helper is in particular useful
   * 		in socket filters where *skb*\ **->data** does not always point
   * 		to the start of the mac header and where "direct packet access"
   * 		is not available.
   * 	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_fib_lookup(void *ctx, struct bpf_fib_lookup *params, int plen, u32 flags)
   *	Description
   *		Do FIB lookup in kernel tables using parameters in *params*.
   *		If lookup is successful and result shows packet is to be
   *		forwarded, the neighbor tables are searched for the nexthop.
   *		If successful (ie., FIB lookup shows forwarding and nexthop
   *		is resolved), the nexthop address is returned in ipv4_dst
   *		or ipv6_dst based on family, smac is set to mac address of
   *		egress device, dmac is set to nexthop mac address, rt_metric
   *		is set to metric from route (IPv4/IPv6 only), and ifindex
   *		is set to the device index of the nexthop from the FIB lookup.
   *
   *             *plen* argument is the size of the passed in struct.
   *             *flags* argument can be a combination of one or more of the
   *             following values:
   *
   *		**BPF_FIB_LOOKUP_DIRECT**
   *			Do a direct table lookup vs full lookup using FIB
   *			rules.
   *		**BPF_FIB_LOOKUP_OUTPUT**
   *			Perform lookup from an egress perspective (default is
   *			ingress).
   *
   *             *ctx* is either **struct xdp_md** for XDP programs or
   *             **struct sk_buff** tc cls_act programs.
   *     Return
   *		* < 0 if any input argument is invalid
   *		*   0 on success (packet is forwarded, nexthop neighbor exists)
   *		* > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the
   *		  packet is not forwarded or needs assist from full stack
   *
   * int bpf_sock_hash_update(struct bpf_sock_ops_kern *skops, struct bpf_map *map, void *key, u64 flags)
   *	Description
   *		Add an entry to, or update a sockhash *map* referencing sockets.
   *		The *skops* is used as a new value for the entry associated to
   *		*key*. *flags* is one of:
   *
   *		**BPF_NOEXIST**
   *			The entry for *key* must not exist in the map.
   *		**BPF_EXIST**
   *			The entry for *key* must already exist in the map.
   *		**BPF_ANY**
   *			No condition on the existence of the entry for *key*.
   *
   *		If the *map* has eBPF programs (parser and verdict), those will
   *		be inherited by the socket being added. If the socket is
   *		already attached to eBPF programs, this results in an error.
   *	Return
   *		0 on success, or a negative error in case of failure.
   *
   * int bpf_msg_redirect_hash(struct sk_msg_buff *msg, struct bpf_map *map, void *key, u64 flags)
   *	Description
   *		This helper is used in programs implementing policies at the
   *		socket level. If the message *msg* is allowed to pass (i.e. if
   *		the verdict eBPF program returns **SK_PASS**), redirect it to
   *		the socket referenced by *map* (of type
   *		**BPF_MAP_TYPE_SOCKHASH**) using hash *key*. Both ingress and
   *		egress interfaces can be used for redirection. The
   *		**BPF_F_INGRESS** value in *flags* is used to make the
   *		distinction (ingress path is selected if the flag is present,
   *		egress path otherwise). This is the only flag supported for now.
   *	Return
   *		**SK_PASS** on success, or **SK_DROP** on error.
   *
   * int bpf_sk_redirect_hash(struct sk_buff *skb, struct bpf_map *map, void *key, u64 flags)
   *	Description
   *		This helper is used in programs implementing policies at the
   *		skb socket level. If the sk_buff *skb* is allowed to pass (i.e.
   *		if the verdeict eBPF program returns **SK_PASS**), redirect it
   *		to the socket referenced by *map* (of type
   *		**BPF_MAP_TYPE_SOCKHASH**) using hash *key*. Both ingress and
   *		egress interfaces can be used for redirection. The
   *		**BPF_F_INGRESS** value in *flags* is used to make the
   *		distinction (ingress path is selected if the flag is present,
   *		egress otherwise). This is the only flag supported for now.
   *	Return
   *		**SK_PASS** on success, or **SK_DROP** on error.
   *
   * int bpf_lwt_push_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len)
   *	Description
   *		Encapsulate the packet associated to *skb* within a Layer 3
   *		protocol header. This header is provided in the buffer at
   *		address *hdr*, with *len* its size in bytes. *type* indicates
   *		the protocol of the header and can be one of:
   *
   *		**BPF_LWT_ENCAP_SEG6**
   *			IPv6 encapsulation with Segment Routing Header
   *			(**struct ipv6_sr_hdr**). *hdr* only contains the SRH,
   *			the IPv6 header is computed by the kernel.
   *		**BPF_LWT_ENCAP_SEG6_INLINE**
   *			Only works if *skb* contains an IPv6 packet. Insert a
   *			Segment Routing Header (**struct ipv6_sr_hdr**) inside
   *			the IPv6 header.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   *	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_lwt_seg6_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len)
   *	Description
   *		Store *len* bytes from address *from* into the packet
   *		associated to *skb*, at *offset*. Only the flags, tag and TLVs
   *		inside the outermost IPv6 Segment Routing Header can be
   *		modified through this helper.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   *	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_lwt_seg6_adjust_srh(struct sk_buff *skb, u32 offset, s32 delta)
   *	Description
   *		Adjust the size allocated to TLVs in the outermost IPv6
   *		Segment Routing Header contained in the packet associated to
   *		*skb*, at position *offset* by *delta* bytes. Only offsets
   *		after the segments are accepted. *delta* can be as well
   *		positive (growing) as negative (shrinking).
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   *	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_lwt_seg6_action(struct sk_buff *skb, u32 action, void *param, u32 param_len)
   *	Description
   *		Apply an IPv6 Segment Routing action of type *action* to the
   *		packet associated to *skb*. Each action takes a parameter
   *		contained at address *param*, and of length *param_len* bytes.
   *		*action* can be one of:
   *
   *		**SEG6_LOCAL_ACTION_END_X**
   *			End.X action: Endpoint with Layer-3 cross-connect.
   *			Type of *param*: **struct in6_addr**.
   *		**SEG6_LOCAL_ACTION_END_T**
   *			End.T action: Endpoint with specific IPv6 table lookup.
   *			Type of *param*: **int**.
   *		**SEG6_LOCAL_ACTION_END_B6**
   *			End.B6 action: Endpoint bound to an SRv6 policy.
   *			Type of param: **struct ipv6_sr_hdr**.
   *		**SEG6_LOCAL_ACTION_END_B6_ENCAP**
   *			End.B6.Encap action: Endpoint bound to an SRv6
   *			encapsulation policy.
   *			Type of param: **struct ipv6_sr_hdr**.
   *
   * 		A call to this helper is susceptible to change the underlaying
   * 		packet buffer. Therefore, at load time, all checks on pointers
   * 		previously done by the verifier are invalidated and must be
   * 		performed again, if the helper is used in combination with
   * 		direct packet access.
   *	Return
   * 		0 on success, or a negative error in case of failure.
   *
   * int bpf_rc_keydown(void *ctx, u32 protocol, u64 scancode, u32 toggle)
   *	Description
   *		This helper is used in programs implementing IR decoding, to
   *		report a successfully decoded key press with *scancode*,
   *		*toggle* value in the given *protocol*. The scancode will be
   *		translated to a keycode using the rc keymap, and reported as
   *		an input key down event. After a period a key up event is
   *		generated. This period can be extended by calling either
   *		**bpf_rc_keydown** () again with the same values, or calling
   *		**bpf_rc_repeat** ().
   *
   *		Some protocols include a toggle bit, in case the button	was
   *		released and pressed again between consecutive scancodes.
   *
   *		The *ctx* should point to the lirc sample as passed into
   *		the program.
   *
   *		The *protocol* is the decoded protocol number (see
   *		**enum rc_proto** for some predefined values).
   *
   *		This helper is only available is the kernel was compiled with
   *		the **CONFIG_BPF_LIRC_MODE2** configuration option set to
   *		"**y**".
   *	Return
   *		0
   *
   * int bpf_rc_repeat(void *ctx)
   *	Description
   *		This helper is used in programs implementing IR decoding, to
   *		report a successfully decoded repeat key message. This delays
   *		the generation of a key up event for previously generated
   *		key down event.
   *
   *		Some IR protocols like NEC have a special IR message for
   *		repeating last button, for when a button is held down.
   *
   *		The *ctx* should point to the lirc sample as passed into
   *		the program.
   *
   *		This helper is only available is the kernel was compiled with
   *		the **CONFIG_BPF_LIRC_MODE2** configuration option set to
   *		"**y**".
   *	Return
   *		0
   *
   * uint64_t bpf_skb_cgroup_id(struct sk_buff *skb)
   * 	Description
   * 		Return the cgroup v2 id of the socket associated with the *skb*.
   * 		This is roughly similar to the **bpf_get_cgroup_classid**\ ()
   * 		helper for cgroup v1 by providing a tag resp. identifier that
   * 		can be matched on or used for map lookups e.g. to implement
   * 		policy. The cgroup v2 id of a given path in the hierarchy is
   * 		exposed in user space through the f_handle API in order to get
   * 		to the same 64-bit id.
   *
   * 		This helper can be used on TC egress path, but not on ingress,
   * 		and is available only if the kernel was compiled with the
   * 		**CONFIG_SOCK_CGROUP_DATA** configuration option.
   * 	Return
   * 		The id is returned or 0 in case the id could not be retrieved.
   *
   * u64 bpf_skb_ancestor_cgroup_id(struct sk_buff *skb, int ancestor_level)
   *	Description
   *		Return id of cgroup v2 that is ancestor of cgroup associated
   *		with the *skb* at the *ancestor_level*.  The root cgroup is at
   *		*ancestor_level* zero and each step down the hierarchy
   *		increments the level. If *ancestor_level* == level of cgroup
   *		associated with *skb*, then return value will be same as that
   *		of **bpf_skb_cgroup_id**\ ().
   *
   *		The helper is useful to implement policies based on cgroups
   *		that are upper in hierarchy than immediate cgroup associated
   *		with *skb*.
   *
   *		The format of returned id and helper limitations are same as in
   *		**bpf_skb_cgroup_id**\ ().
   *	Return
   *		The id is returned or 0 in case the id could not be retrieved.
   *
   * u64 bpf_get_current_cgroup_id(void)
   * 	Return
   * 		A 64-bit integer containing the current cgroup id based
   * 		on the cgroup within which the current task is running.
   *
   * void* get_local_storage(void *map, u64 flags)
   *	Description
   *		Get the pointer to the local storage area.
   *		The type and the size of the local storage is defined
   *		by the *map* argument.
   *		The *flags* meaning is specific for each map type,
   *		and has to be 0 for cgroup local storage.
   *
   *		Depending on the bpf program type, a local storage area
   *		can be shared between multiple instances of the bpf program,
   *		running simultaneously.
   *
   *		A user should care about the synchronization by himself.
   *		For example, by using the BPF_STX_XADD instruction to alter
   *		the shared data.
   *	Return
   *		Pointer to the local storage area.
   *
   * int bpf_sk_select_reuseport(struct sk_reuseport_md *reuse, struct bpf_map *map, void *key, u64 flags)
   *	Description
   *		Select a SO_REUSEPORT sk from a	BPF_MAP_TYPE_REUSEPORT_ARRAY map
   *		It checks the selected sk is matching the incoming
   *		request in the skb.
   *	Return
   *		0 on success, or a negative error in case of failure.
   */
  #define __BPF_FUNC_MAPPER(FN)		\
  	FN(unspec),			\
  	FN(map_lookup_elem),		\
  	FN(map_update_elem),		\
  	FN(map_delete_elem),		\
  	FN(probe_read),			\
  	FN(ktime_get_ns),		\
  	FN(trace_printk),		\
  	FN(get_prandom_u32),		\
  	FN(get_smp_processor_id),	\
  	FN(skb_store_bytes),		\
  	FN(l3_csum_replace),		\
  	FN(l4_csum_replace),		\
  	FN(tail_call),			\
  	FN(clone_redirect),		\
  	FN(get_current_pid_tgid),	\
  	FN(get_current_uid_gid),	\
  	FN(get_current_comm),		\
  	FN(get_cgroup_classid),		\
  	FN(skb_vlan_push),		\
  	FN(skb_vlan_pop),		\
  	FN(skb_get_tunnel_key),		\
  	FN(skb_set_tunnel_key),		\
  	FN(perf_event_read),		\
  	FN(redirect),			\
  	FN(get_route_realm),		\
  	FN(perf_event_output),		\
  	FN(skb_load_bytes),		\
  	FN(get_stackid),		\
  	FN(csum_diff),			\
  	FN(skb_get_tunnel_opt),		\
  	FN(skb_set_tunnel_opt),		\
  	FN(skb_change_proto),		\
  	FN(skb_change_type),		\
  	FN(skb_under_cgroup),		\
  	FN(get_hash_recalc),		\
  	FN(get_current_task),		\
  	FN(probe_write_user),		\
  	FN(current_task_under_cgroup),	\
  	FN(skb_change_tail),		\
  	FN(skb_pull_data),		\
  	FN(csum_update),		\
  	FN(set_hash_invalid),		\
  	FN(get_numa_node_id),		\
  	FN(skb_change_head),		\
  	FN(xdp_adjust_head),		\
  	FN(probe_read_str),		\
  	FN(get_socket_cookie),		\
  	FN(get_socket_uid),		\
  	FN(set_hash),			\
  	FN(setsockopt),			\
  	FN(skb_adjust_room),		\
  	FN(redirect_map),		\
  	FN(sk_redirect_map),		\
  	FN(sock_map_update),		\
  	FN(xdp_adjust_meta),		\
  	FN(perf_event_read_value),	\
  	FN(perf_prog_read_value),	\
  	FN(getsockopt),			\
  	FN(override_return),		\
  	FN(sock_ops_cb_flags_set),	\
  	FN(msg_redirect_map),		\
  	FN(msg_apply_bytes),		\
  	FN(msg_cork_bytes),		\
  	FN(msg_pull_data),		\
  	FN(bind),			\
  	FN(xdp_adjust_tail),		\
  	FN(skb_get_xfrm_state),		\
  	FN(get_stack),			\
  	FN(skb_load_bytes_relative),	\
  	FN(fib_lookup),			\
  	FN(sock_hash_update),		\
  	FN(msg_redirect_hash),		\
  	FN(sk_redirect_hash),		\
  	FN(lwt_push_encap),		\
  	FN(lwt_seg6_store_bytes),	\
  	FN(lwt_seg6_adjust_srh),	\
  	FN(lwt_seg6_action),		\
  	FN(rc_repeat),			\
  	FN(rc_keydown),			\
  	FN(skb_cgroup_id),		\
  	FN(get_current_cgroup_id),	\
  	FN(get_local_storage),		\
  	FN(sk_select_reuseport),	\
  	FN(skb_ancestor_cgroup_id),
  
  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
   * function eBPF program intends to call
   */
  #define __BPF_ENUM_FN(x) BPF_FUNC_ ## x
  enum bpf_func_id {
  	__BPF_FUNC_MAPPER(__BPF_ENUM_FN)
  	__BPF_FUNC_MAX_ID,
  };
  #undef __BPF_ENUM_FN
  
  /* All flags used by eBPF helper functions, placed here. */
  
  /* BPF_FUNC_skb_store_bytes flags. */
  #define BPF_F_RECOMPUTE_CSUM		(1ULL << 0)
  #define BPF_F_INVALIDATE_HASH		(1ULL << 1)
  
  /* BPF_FUNC_l3_csum_replace and BPF_FUNC_l4_csum_replace flags.
   * First 4 bits are for passing the header field size.
   */
  #define BPF_F_HDR_FIELD_MASK		0xfULL
  
  /* BPF_FUNC_l4_csum_replace flags. */
  #define BPF_F_PSEUDO_HDR		(1ULL << 4)
  #define BPF_F_MARK_MANGLED_0		(1ULL << 5)
  #define BPF_F_MARK_ENFORCE		(1ULL << 6)
  
  /* BPF_FUNC_clone_redirect and BPF_FUNC_redirect flags. */
  #define BPF_F_INGRESS			(1ULL << 0)
  
  /* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */
  #define BPF_F_TUNINFO_IPV6		(1ULL << 0)
  
  /* flags for both BPF_FUNC_get_stackid and BPF_FUNC_get_stack. */
  #define BPF_F_SKIP_FIELD_MASK		0xffULL
  #define BPF_F_USER_STACK		(1ULL << 8)
  /* flags used by BPF_FUNC_get_stackid only. */
  #define BPF_F_FAST_STACK_CMP		(1ULL << 9)
  #define BPF_F_REUSE_STACKID		(1ULL << 10)
  /* flags used by BPF_FUNC_get_stack only. */
  #define BPF_F_USER_BUILD_ID		(1ULL << 11)
  
  /* BPF_FUNC_skb_set_tunnel_key flags. */
  #define BPF_F_ZERO_CSUM_TX		(1ULL << 1)
  #define BPF_F_DONT_FRAGMENT		(1ULL << 2)
  #define BPF_F_SEQ_NUMBER		(1ULL << 3)
  
  /* BPF_FUNC_perf_event_output, BPF_FUNC_perf_event_read and
   * BPF_FUNC_perf_event_read_value flags.
   */
  #define BPF_F_INDEX_MASK		0xffffffffULL
  #define BPF_F_CURRENT_CPU		BPF_F_INDEX_MASK
  /* BPF_FUNC_perf_event_output for sk_buff input context. */
  #define BPF_F_CTXLEN_MASK		(0xfffffULL << 32)
  
  /* Mode for BPF_FUNC_skb_adjust_room helper. */
  enum bpf_adj_room_mode {
  	BPF_ADJ_ROOM_NET,
  };
  
  /* Mode for BPF_FUNC_skb_load_bytes_relative helper. */
  enum bpf_hdr_start_off {
  	BPF_HDR_START_MAC,
  	BPF_HDR_START_NET,
  };
  
  /* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */
  enum bpf_lwt_encap_mode {
  	BPF_LWT_ENCAP_SEG6,
  	BPF_LWT_ENCAP_SEG6_INLINE
  };
  
  /* user accessible mirror of in-kernel sk_buff.
   * new fields can only be added to the end of this structure
   */
  struct __sk_buff {
  	__u32 len;
  	__u32 pkt_type;
  	__u32 mark;
  	__u32 queue_mapping;
  	__u32 protocol;
  	__u32 vlan_present;
  	__u32 vlan_tci;
  	__u32 vlan_proto;
  	__u32 priority;
  	__u32 ingress_ifindex;
  	__u32 ifindex;
  	__u32 tc_index;
  	__u32 cb[5];
  	__u32 hash;
  	__u32 tc_classid;
  	__u32 data;
  	__u32 data_end;
  	__u32 napi_id;
  
  	/* Accessed by BPF_PROG_TYPE_sk_skb types from here to ... */
  	__u32 family;
  	__u32 remote_ip4;	/* Stored in network byte order */
  	__u32 local_ip4;	/* Stored in network byte order */
  	__u32 remote_ip6[4];	/* Stored in network byte order */
  	__u32 local_ip6[4];	/* Stored in network byte order */
  	__u32 remote_port;	/* Stored in network byte order */
  	__u32 local_port;	/* stored in host byte order */
  	/* ... here. */
  
  	__u32 data_meta;
  };
  
  struct bpf_tunnel_key {
  	__u32 tunnel_id;
  	union {
  		__u32 remote_ipv4;
  		__u32 remote_ipv6[4];
  	};
  	__u8 tunnel_tos;
  	__u8 tunnel_ttl;
  	__u16 tunnel_ext;	/* Padding, future use. */
  	__u32 tunnel_label;
  };
  
  /* user accessible mirror of in-kernel xfrm_state.
   * new fields can only be added to the end of this structure
   */
  struct bpf_xfrm_state {
  	__u32 reqid;
  	__u32 spi;	/* Stored in network byte order */
  	__u16 family;
  	__u16 ext;	/* Padding, future use. */
  	union {
  		__u32 remote_ipv4;	/* Stored in network byte order */
  		__u32 remote_ipv6[4];	/* Stored in network byte order */
  	};
  };
  
  /* Generic BPF return codes which all BPF program types may support.
   * The values are binary compatible with their TC_ACT_* counter-part to
   * provide backwards compatibility with existing SCHED_CLS and SCHED_ACT
   * programs.
   *
   * XDP is handled seprately, see XDP_*.
   */
  enum bpf_ret_code {
  	BPF_OK = 0,
  	/* 1 reserved */
  	BPF_DROP = 2,
  	/* 3-6 reserved */
  	BPF_REDIRECT = 7,
  	/* >127 are reserved for prog type specific return codes */
  };
  
  struct bpf_sock {
  	__u32 bound_dev_if;
  	__u32 family;
  	__u32 type;
  	__u32 protocol;
  	__u32 mark;
  	__u32 priority;
  	__u32 src_ip4;		/* Allows 1,2,4-byte read.
  				 * Stored in network byte order.
  				 */
  	__u32 src_ip6[4];	/* Allows 1,2,4-byte read.
  				 * Stored in network byte order.
  				 */
  	__u32 src_port;		/* Allows 4-byte read.
  				 * Stored in host byte order
  				 */
  };
  
  #define XDP_PACKET_HEADROOM 256
  
  /* User return codes for XDP prog type.
   * A valid XDP program must return one of these defined values. All other
   * return codes are reserved for future use. Unknown return codes will
   * result in packet drops and a warning via bpf_warn_invalid_xdp_action().
   */
  enum xdp_action {
  	XDP_ABORTED = 0,
  	XDP_DROP,
  	XDP_PASS,
  	XDP_TX,
  	XDP_REDIRECT,
  };
  
  /* user accessible metadata for XDP packet hook
   * new fields must be added to the end of this structure
   */
  struct xdp_md {
  	__u32 data;
  	__u32 data_end;
  	__u32 data_meta;
  	/* Below access go through struct xdp_rxq_info */
  	__u32 ingress_ifindex; /* rxq->dev->ifindex */
  	__u32 rx_queue_index;  /* rxq->queue_index  */
  };
  
  enum sk_action {
  	SK_DROP = 0,
  	SK_PASS,
  };
  
  /* user accessible metadata for SK_MSG packet hook, new fields must
   * be added to the end of this structure
   */
  struct sk_msg_md {
  	void *data;
  	void *data_end;
  
  	__u32 family;
  	__u32 remote_ip4;	/* Stored in network byte order */
  	__u32 local_ip4;	/* Stored in network byte order */
  	__u32 remote_ip6[4];	/* Stored in network byte order */
  	__u32 local_ip6[4];	/* Stored in network byte order */
  	__u32 remote_port;	/* Stored in network byte order */
  	__u32 local_port;	/* stored in host byte order */
  };
  
  struct sk_reuseport_md {
  	/*
  	 * Start of directly accessible data. It begins from
  	 * the tcp/udp header.
  	 */
  	void *data;
  	void *data_end;		/* End of directly accessible data */
  	/*
  	 * Total length of packet (starting from the tcp/udp header).
  	 * Note that the directly accessible bytes (data_end - data)
  	 * could be less than this "len".  Those bytes could be
  	 * indirectly read by a helper "bpf_skb_load_bytes()".
  	 */
  	__u32 len;
  	/*
  	 * Eth protocol in the mac header (network byte order). e.g.
  	 * ETH_P_IP(0x0800) and ETH_P_IPV6(0x86DD)
  	 */
  	__u32 eth_protocol;
  	__u32 ip_protocol;	/* IP protocol. e.g. IPPROTO_TCP, IPPROTO_UDP */
  	__u32 bind_inany;	/* Is sock bound to an INANY address? */
  	__u32 hash;		/* A hash of the packet 4 tuples */
  };
  
  #define BPF_TAG_SIZE	8
  
  struct bpf_prog_info {
  	__u32 type;
  	__u32 id;
  	__u8  tag[BPF_TAG_SIZE];
  	__u32 jited_prog_len;
  	__u32 xlated_prog_len;
  	__aligned_u64 jited_prog_insns;
  	__aligned_u64 xlated_prog_insns;
  	__u64 load_time;	/* ns since boottime */
  	__u32 created_by_uid;
  	__u32 nr_map_ids;
  	__aligned_u64 map_ids;
  	char name[BPF_OBJ_NAME_LEN];
  	__u32 ifindex;
  	__u32 gpl_compatible:1;
  	__u64 netns_dev;
  	__u64 netns_ino;
  	__u32 nr_jited_ksyms;
  	__u32 nr_jited_func_lens;
  	__aligned_u64 jited_ksyms;
  	__aligned_u64 jited_func_lens;
  } __attribute__((aligned(8)));
  
  struct bpf_map_info {
  	__u32 type;
  	__u32 id;
  	__u32 key_size;
  	__u32 value_size;
  	__u32 max_entries;
  	__u32 map_flags;
  	char  name[BPF_OBJ_NAME_LEN];
  	__u32 ifindex;
  	__u32 :32;
  	__u64 netns_dev;
  	__u64 netns_ino;
  	__u32 btf_id;
  	__u32 btf_key_type_id;
  	__u32 btf_value_type_id;
  } __attribute__((aligned(8)));
  
  struct bpf_btf_info {
  	__aligned_u64 btf;
  	__u32 btf_size;
  	__u32 id;
  } __attribute__((aligned(8)));
  
  /* User bpf_sock_addr struct to access socket fields and sockaddr struct passed
   * by user and intended to be used by socket (e.g. to bind to, depends on
   * attach attach type).
   */
  struct bpf_sock_addr {
  	__u32 user_family;	/* Allows 4-byte read, but no write. */
  	__u32 user_ip4;		/* Allows 1,2,4-byte read and 4-byte write.
  				 * Stored in network byte order.
  				 */
  	__u32 user_ip6[4];	/* Allows 1,2,4-byte read an 4-byte write.
  				 * Stored in network byte order.
  				 */
  	__u32 user_port;	/* Allows 4-byte read and write.
  				 * Stored in network byte order
  				 */
  	__u32 family;		/* Allows 4-byte read, but no write */
  	__u32 type;		/* Allows 4-byte read, but no write */
  	__u32 protocol;		/* Allows 4-byte read, but no write */
  	__u32 msg_src_ip4;	/* Allows 1,2,4-byte read an 4-byte write.
  				 * Stored in network byte order.
  				 */
  	__u32 msg_src_ip6[4];	/* Allows 1,2,4-byte read an 4-byte write.
  				 * Stored in network byte order.
  				 */
  };
  
  /* User bpf_sock_ops struct to access socket values and specify request ops
   * and their replies.
   * Some of this fields are in network (bigendian) byte order and may need
   * to be converted before use (bpf_ntohl() defined in samples/bpf/bpf_endian.h).
   * New fields can only be added at the end of this structure
   */
  struct bpf_sock_ops {
  	__u32 op;
  	union {
  		__u32 args[4];		/* Optionally passed to bpf program */
  		__u32 reply;		/* Returned by bpf program	    */
  		__u32 replylong[4];	/* Optionally returned by bpf prog  */
  	};
  	__u32 family;
  	__u32 remote_ip4;	/* Stored in network byte order */
  	__u32 local_ip4;	/* Stored in network byte order */
  	__u32 remote_ip6[4];	/* Stored in network byte order */
  	__u32 local_ip6[4];	/* Stored in network byte order */
  	__u32 remote_port;	/* Stored in network byte order */
  	__u32 local_port;	/* stored in host byte order */
  	__u32 is_fullsock;	/* Some TCP fields are only valid if
  				 * there is a full socket. If not, the
  				 * fields read as zero.
  				 */
  	__u32 snd_cwnd;
  	__u32 srtt_us;		/* Averaged RTT << 3 in usecs */
  	__u32 bpf_sock_ops_cb_flags; /* flags defined in uapi/linux/tcp.h */
  	__u32 state;
  	__u32 rtt_min;
  	__u32 snd_ssthresh;
  	__u32 rcv_nxt;
  	__u32 snd_nxt;
  	__u32 snd_una;
  	__u32 mss_cache;
  	__u32 ecn_flags;
  	__u32 rate_delivered;
  	__u32 rate_interval_us;
  	__u32 packets_out;
  	__u32 retrans_out;
  	__u32 total_retrans;
  	__u32 segs_in;
  	__u32 data_segs_in;
  	__u32 segs_out;
  	__u32 data_segs_out;
  	__u32 lost_out;
  	__u32 sacked_out;
  	__u32 sk_txhash;
  	__u64 bytes_received;
  	__u64 bytes_acked;
  };
  
  /* Definitions for bpf_sock_ops_cb_flags */
  #define BPF_SOCK_OPS_RTO_CB_FLAG	(1<<0)
  #define BPF_SOCK_OPS_RETRANS_CB_FLAG	(1<<1)
  #define BPF_SOCK_OPS_STATE_CB_FLAG	(1<<2)
  #define BPF_SOCK_OPS_ALL_CB_FLAGS       0x7		/* Mask of all currently
  							 * supported cb flags
  							 */
  
  /* List of known BPF sock_ops operators.
   * New entries can only be added at the end
   */
  enum {
  	BPF_SOCK_OPS_VOID,
  	BPF_SOCK_OPS_TIMEOUT_INIT,	/* Should return SYN-RTO value to use or
  					 * -1 if default value should be used
  					 */
  	BPF_SOCK_OPS_RWND_INIT,		/* Should return initial advertized
  					 * window (in packets) or -1 if default
  					 * value should be used
  					 */
  	BPF_SOCK_OPS_TCP_CONNECT_CB,	/* Calls BPF program right before an
  					 * active connection is initialized
  					 */
  	BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB,	/* Calls BPF program when an
  						 * active connection is
  						 * established
  						 */
  	BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB,	/* Calls BPF program when a
  						 * passive connection is
  						 * established
  						 */
  	BPF_SOCK_OPS_NEEDS_ECN,		/* If connection's congestion control
  					 * needs ECN
  					 */
  	BPF_SOCK_OPS_BASE_RTT,		/* Get base RTT. The correct value is
  					 * based on the path and may be
  					 * dependent on the congestion control
  					 * algorithm. In general it indicates
  					 * a congestion threshold. RTTs above
  					 * this indicate congestion
  					 */
  	BPF_SOCK_OPS_RTO_CB,		/* Called when an RTO has triggered.
  					 * Arg1: value of icsk_retransmits
  					 * Arg2: value of icsk_rto
  					 * Arg3: whether RTO has expired
  					 */
  	BPF_SOCK_OPS_RETRANS_CB,	/* Called when skb is retransmitted.
  					 * Arg1: sequence number of 1st byte
  					 * Arg2: # segments
  					 * Arg3: return value of
  					 *       tcp_transmit_skb (0 => success)
  					 */
  	BPF_SOCK_OPS_STATE_CB,		/* Called when TCP changes state.
  					 * Arg1: old_state
  					 * Arg2: new_state
  					 */
  	BPF_SOCK_OPS_TCP_LISTEN_CB,	/* Called on listen(2), right after
  					 * socket transition to LISTEN state.
  					 */
  };
  
  /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
   * changes between the TCP and BPF versions. Ideally this should never happen.
   * If it does, we need to add code to convert them before calling
   * the BPF sock_ops function.
   */
  enum {
  	BPF_TCP_ESTABLISHED = 1,
  	BPF_TCP_SYN_SENT,
  	BPF_TCP_SYN_RECV,
  	BPF_TCP_FIN_WAIT1,
  	BPF_TCP_FIN_WAIT2,
  	BPF_TCP_TIME_WAIT,
  	BPF_TCP_CLOSE,
  	BPF_TCP_CLOSE_WAIT,
  	BPF_TCP_LAST_ACK,
  	BPF_TCP_LISTEN,
  	BPF_TCP_CLOSING,	/* Now a valid state */
  	BPF_TCP_NEW_SYN_RECV,
  
  	BPF_TCP_MAX_STATES	/* Leave at the end! */
  };
  
  #define TCP_BPF_IW		1001	/* Set TCP initial congestion window */
  #define TCP_BPF_SNDCWND_CLAMP	1002	/* Set sndcwnd_clamp */
  
  struct bpf_perf_event_value {
  	__u64 counter;
  	__u64 enabled;
  	__u64 running;
  };
  
  #define BPF_DEVCG_ACC_MKNOD	(1ULL << 0)
  #define BPF_DEVCG_ACC_READ	(1ULL << 1)
  #define BPF_DEVCG_ACC_WRITE	(1ULL << 2)
  
  #define BPF_DEVCG_DEV_BLOCK	(1ULL << 0)
  #define BPF_DEVCG_DEV_CHAR	(1ULL << 1)
  
  struct bpf_cgroup_dev_ctx {
  	/* access_type encoded as (BPF_DEVCG_ACC_* << 16) | BPF_DEVCG_DEV_* */
  	__u32 access_type;
  	__u32 major;
  	__u32 minor;
  };
  
  struct bpf_raw_tracepoint_args {
  	__u64 args[0];
  };
  
  /* DIRECT:  Skip the FIB rules and go to FIB table associated with device
   * OUTPUT:  Do lookup from egress perspective; default is ingress
   */
  #define BPF_FIB_LOOKUP_DIRECT  BIT(0)
  #define BPF_FIB_LOOKUP_OUTPUT  BIT(1)
  
  enum {
  	BPF_FIB_LKUP_RET_SUCCESS,      /* lookup successful */
  	BPF_FIB_LKUP_RET_BLACKHOLE,    /* dest is blackholed; can be dropped */
  	BPF_FIB_LKUP_RET_UNREACHABLE,  /* dest is unreachable; can be dropped */
  	BPF_FIB_LKUP_RET_PROHIBIT,     /* dest not allowed; can be dropped */
  	BPF_FIB_LKUP_RET_NOT_FWDED,    /* packet is not forwarded */
  	BPF_FIB_LKUP_RET_FWD_DISABLED, /* fwding is not enabled on ingress */
  	BPF_FIB_LKUP_RET_UNSUPP_LWT,   /* fwd requires encapsulation */
  	BPF_FIB_LKUP_RET_NO_NEIGH,     /* no neighbor entry for nh */
  	BPF_FIB_LKUP_RET_FRAG_NEEDED,  /* fragmentation required to fwd */
  };
  
  struct bpf_fib_lookup {
  	/* input:  network family for lookup (AF_INET, AF_INET6)
  	 * output: network family of egress nexthop
  	 */
  	__u8	family;
  
  	/* set if lookup is to consider L4 data - e.g., FIB rules */
  	__u8	l4_protocol;
  	__be16	sport;
  	__be16	dport;
  
  	/* total length of packet from network header - used for MTU check */
  	__u16	tot_len;
  
  	/* input: L3 device index for lookup
  	 * output: device index from FIB lookup
  	 */
  	__u32	ifindex;
  
  	union {
  		/* inputs to lookup */
  		__u8	tos;		/* AF_INET  */
  		__be32	flowinfo;	/* AF_INET6, flow_label + priority */
  
  		/* output: metric of fib result (IPv4/IPv6 only) */
  		__u32	rt_metric;
  	};
  
  	union {
  		__be32		ipv4_src;
  		__u32		ipv6_src[4];  /* in6_addr; network order */
  	};
  
  	/* input to bpf_fib_lookup, ipv{4,6}_dst is destination address in
  	 * network header. output: bpf_fib_lookup sets to gateway address
  	 * if FIB lookup returns gateway route
  	 */
  	union {
  		__be32		ipv4_dst;
  		__u32		ipv6_dst[4];  /* in6_addr; network order */
  	};
  
  	/* output */
  	__be16	h_vlan_proto;
  	__be16	h_vlan_TCI;
  	__u8	smac[6];     /* ETH_ALEN */
  	__u8	dmac[6];     /* ETH_ALEN */
  };
  
  enum bpf_task_fd_type {
  	BPF_FD_TYPE_RAW_TRACEPOINT,	/* tp name */
  	BPF_FD_TYPE_TRACEPOINT,		/* tp name */
  	BPF_FD_TYPE_KPROBE,		/* (symbol + offset) or addr */
  	BPF_FD_TYPE_KRETPROBE,		/* (symbol + offset) or addr */
  	BPF_FD_TYPE_UPROBE,		/* filename + offset */
  	BPF_FD_TYPE_URETPROBE,		/* filename + offset */
  };
  
  #endif /* _UAPI__LINUX_BPF_H__ */
  