mirror of https://github.com/mkerrisk/man-pages
bpf.2: Place EXAMPLES section in correct location
As per section ordering rules given in man-pages(7). Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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Michael Kerrisk
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138
man2/bpf.2
138
man2/bpf.2
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@ -971,75 +971,6 @@ ioctl(event_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
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.in
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.\"
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.\"
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.SH EXAMPLES
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.EX
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/* bpf+sockets example:
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* 1. create array map of 256 elements
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* 2. load program that counts number of packets received
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* r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)]
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* map[r0]++
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* 3. attach prog_fd to raw socket via setsockopt()
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* 4. print number of received TCP/UDP packets every second
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*/
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int
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main(int argc, char **argv)
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{
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int sock, map_fd, prog_fd, key;
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long long value = 0, tcp_cnt, udp_cnt;
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map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key),
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sizeof(value), 256);
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if (map_fd < 0) {
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printf("failed to create map \(aq%s\(aq\en", strerror(errno));
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/* likely not run as root */
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return 1;
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}
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struct bpf_insn prog[] = {
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BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* r6 = r1 */
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BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol)),
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/* r0 = ip->proto */
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BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4),
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/* *(u32 *)(fp - 4) = r0 */
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), /* r2 = fp */
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = r2 - 4 */
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BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* r1 = map_fd */
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BPF_CALL_FUNC(BPF_FUNC_map_lookup_elem),
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/* r0 = map_lookup(r1, r2) */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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/* if (r0 == 0) goto pc+2 */
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BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
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BPF_XADD(BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0),
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/* lock *(u64 *) r0 += r1 */
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.\" == atomic64_add
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BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
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BPF_EXIT_INSN(), /* return r0 */
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};
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prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, prog,
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sizeof(prog) / sizeof(prog[0]), "GPL");
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sock = open_raw_sock("lo");
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assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
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sizeof(prog_fd)) == 0);
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for (;;) {
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key = IPPROTO_TCP;
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assert(bpf_lookup_elem(map_fd, &key, &tcp_cnt) == 0);
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key = IPPROTO_UDP;
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assert(bpf_lookup_elem(map_fd, &key, &udp_cnt) == 0);
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printf("TCP %lld UDP %lld packets\en", tcp_cnt, udp_cnt);
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sleep(1);
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}
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return 0;
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}
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.EE
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.PP
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Some complete working code can be found in the
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.I samples/bpf
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directory in the kernel source tree.
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.SH RETURN VALUE
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For a successful call, the return value depends on the operation:
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.TP
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@ -1270,6 +1201,75 @@ MIPS 64 (since Linux 4.18; cBPF since Linux 3.16);
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riscv (since Linux 5.1).
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.\" commit 2353ecc6f91fd15b893fa01bf85a1c7a823ee4f2
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.PD
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.SH EXAMPLES
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.EX
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/* bpf+sockets example:
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* 1. create array map of 256 elements
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* 2. load program that counts number of packets received
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* r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)]
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* map[r0]++
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* 3. attach prog_fd to raw socket via setsockopt()
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* 4. print number of received TCP/UDP packets every second
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*/
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int
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main(int argc, char **argv)
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{
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int sock, map_fd, prog_fd, key;
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long long value = 0, tcp_cnt, udp_cnt;
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map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key),
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sizeof(value), 256);
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if (map_fd < 0) {
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printf("failed to create map \(aq%s\(aq\en", strerror(errno));
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/* likely not run as root */
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return 1;
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}
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struct bpf_insn prog[] = {
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BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* r6 = r1 */
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BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol)),
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/* r0 = ip->proto */
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BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4),
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/* *(u32 *)(fp - 4) = r0 */
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), /* r2 = fp */
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = r2 - 4 */
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BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* r1 = map_fd */
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BPF_CALL_FUNC(BPF_FUNC_map_lookup_elem),
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/* r0 = map_lookup(r1, r2) */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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/* if (r0 == 0) goto pc+2 */
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BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
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BPF_XADD(BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0),
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/* lock *(u64 *) r0 += r1 */
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.\" == atomic64_add
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BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
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BPF_EXIT_INSN(), /* return r0 */
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};
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prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, prog,
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sizeof(prog) / sizeof(prog[0]), "GPL");
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sock = open_raw_sock("lo");
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assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
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sizeof(prog_fd)) == 0);
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for (;;) {
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key = IPPROTO_TCP;
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assert(bpf_lookup_elem(map_fd, &key, &tcp_cnt) == 0);
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key = IPPROTO_UDP;
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assert(bpf_lookup_elem(map_fd, &key, &udp_cnt) == 0);
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printf("TCP %lld UDP %lld packets\en", tcp_cnt, udp_cnt);
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sleep(1);
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}
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return 0;
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}
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.EE
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.PP
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Some complete working code can be found in the
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.I samples/bpf
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directory in the kernel source tree.
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.SH SEE ALSO
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.BR seccomp (2),
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.BR bpf\-helpers (7),
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