295 lines
6.3 KiB
C
295 lines
6.3 KiB
C
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/* eBPF example program:
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*
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* - Loads eBPF program
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*
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* The eBPF program sets the sk_bound_dev_if index in new AF_INET{6}
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* sockets opened by processes in the cgroup.
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*
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* - Attaches the new program to a cgroup using BPF_PROG_ATTACH
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include <string.h>
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#include <unistd.h>
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <net/if.h>
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#include <inttypes.h>
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#include <linux/bpf.h>
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#include <bpf/bpf.h>
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#include "bpf_insn.h"
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char bpf_log_buf[BPF_LOG_BUF_SIZE];
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static int prog_load(__u32 idx, __u32 mark, __u32 prio)
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{
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/* save pointer to context */
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struct bpf_insn prog_start[] = {
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BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
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};
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struct bpf_insn prog_end[] = {
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BPF_MOV64_IMM(BPF_REG_0, 1), /* r0 = verdict */
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BPF_EXIT_INSN(),
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};
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/* set sk_bound_dev_if on socket */
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struct bpf_insn prog_dev[] = {
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BPF_MOV64_IMM(BPF_REG_3, idx),
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BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, bound_dev_if)),
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BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, bound_dev_if)),
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};
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/* set mark on socket */
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struct bpf_insn prog_mark[] = {
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/* get uid of process */
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BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
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BPF_FUNC_get_current_uid_gid),
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BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xffffffff),
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/* if uid is 0, use given mark, else use the uid as the mark */
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BPF_MOV64_REG(BPF_REG_3, BPF_REG_0),
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BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
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BPF_MOV64_IMM(BPF_REG_3, mark),
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/* set the mark on the new socket */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, mark)),
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BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, mark)),
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};
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/* set priority on socket */
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struct bpf_insn prog_prio[] = {
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_MOV64_IMM(BPF_REG_3, prio),
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BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, priority)),
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BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, priority)),
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};
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LIBBPF_OPTS(bpf_prog_load_opts, opts,
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.log_buf = bpf_log_buf,
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.log_size = BPF_LOG_BUF_SIZE,
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);
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struct bpf_insn *prog;
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size_t insns_cnt;
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void *p;
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int ret;
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insns_cnt = sizeof(prog_start) + sizeof(prog_end);
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if (idx)
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insns_cnt += sizeof(prog_dev);
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if (mark)
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insns_cnt += sizeof(prog_mark);
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if (prio)
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insns_cnt += sizeof(prog_prio);
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p = prog = malloc(insns_cnt);
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if (!prog) {
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fprintf(stderr, "Failed to allocate memory for instructions\n");
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return EXIT_FAILURE;
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}
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memcpy(p, prog_start, sizeof(prog_start));
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p += sizeof(prog_start);
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if (idx) {
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memcpy(p, prog_dev, sizeof(prog_dev));
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p += sizeof(prog_dev);
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}
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if (mark) {
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memcpy(p, prog_mark, sizeof(prog_mark));
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p += sizeof(prog_mark);
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}
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if (prio) {
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memcpy(p, prog_prio, sizeof(prog_prio));
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p += sizeof(prog_prio);
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}
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memcpy(p, prog_end, sizeof(prog_end));
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p += sizeof(prog_end);
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insns_cnt /= sizeof(struct bpf_insn);
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ret = bpf_prog_load(BPF_PROG_TYPE_CGROUP_SOCK, NULL, "GPL",
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prog, insns_cnt, &opts);
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free(prog);
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return ret;
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}
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static int get_bind_to_device(int sd, char *name, size_t len)
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{
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socklen_t optlen = len;
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int rc;
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name[0] = '\0';
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rc = getsockopt(sd, SOL_SOCKET, SO_BINDTODEVICE, name, &optlen);
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if (rc < 0)
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perror("setsockopt(SO_BINDTODEVICE)");
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return rc;
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}
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static unsigned int get_somark(int sd)
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{
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unsigned int mark = 0;
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socklen_t optlen = sizeof(mark);
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int rc;
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rc = getsockopt(sd, SOL_SOCKET, SO_MARK, &mark, &optlen);
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if (rc < 0)
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perror("getsockopt(SO_MARK)");
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return mark;
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}
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static unsigned int get_priority(int sd)
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{
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unsigned int prio = 0;
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socklen_t optlen = sizeof(prio);
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int rc;
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rc = getsockopt(sd, SOL_SOCKET, SO_PRIORITY, &prio, &optlen);
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if (rc < 0)
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perror("getsockopt(SO_PRIORITY)");
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return prio;
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}
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static int show_sockopts(int family)
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{
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unsigned int mark, prio;
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char name[16];
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int sd;
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sd = socket(family, SOCK_DGRAM, 17);
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if (sd < 0) {
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perror("socket");
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return 1;
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}
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if (get_bind_to_device(sd, name, sizeof(name)) < 0)
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return 1;
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mark = get_somark(sd);
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prio = get_priority(sd);
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close(sd);
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printf("sd %d: dev %s, mark %u, priority %u\n", sd, name, mark, prio);
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return 0;
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}
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static int usage(const char *argv0)
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{
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printf("Usage:\n");
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printf(" Attach a program\n");
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printf(" %s -b bind-to-dev -m mark -p prio cg-path\n", argv0);
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printf("\n");
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printf(" Detach a program\n");
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printf(" %s -d cg-path\n", argv0);
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printf("\n");
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printf(" Show inherited socket settings (mark, priority, and device)\n");
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printf(" %s [-6]\n", argv0);
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return EXIT_FAILURE;
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}
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int main(int argc, char **argv)
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{
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__u32 idx = 0, mark = 0, prio = 0;
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const char *cgrp_path = NULL;
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int cg_fd, prog_fd, ret;
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int family = PF_INET;
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int do_attach = 1;
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int rc;
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while ((rc = getopt(argc, argv, "db:m:p:6")) != -1) {
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switch (rc) {
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case 'd':
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do_attach = 0;
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break;
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case 'b':
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idx = if_nametoindex(optarg);
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if (!idx) {
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idx = strtoumax(optarg, NULL, 0);
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if (!idx) {
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printf("Invalid device name\n");
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return EXIT_FAILURE;
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}
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}
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break;
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case 'm':
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mark = strtoumax(optarg, NULL, 0);
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break;
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case 'p':
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prio = strtoumax(optarg, NULL, 0);
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break;
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case '6':
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family = PF_INET6;
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break;
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default:
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return usage(argv[0]);
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}
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}
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if (optind == argc)
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return show_sockopts(family);
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cgrp_path = argv[optind];
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if (!cgrp_path) {
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fprintf(stderr, "cgroup path not given\n");
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return EXIT_FAILURE;
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}
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if (do_attach && !idx && !mark && !prio) {
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fprintf(stderr,
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"One of device, mark or priority must be given\n");
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return EXIT_FAILURE;
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}
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cg_fd = open(cgrp_path, O_DIRECTORY | O_RDONLY);
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if (cg_fd < 0) {
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printf("Failed to open cgroup path: '%s'\n", strerror(errno));
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return EXIT_FAILURE;
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}
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if (do_attach) {
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prog_fd = prog_load(idx, mark, prio);
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if (prog_fd < 0) {
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printf("Failed to load prog: '%s'\n", strerror(errno));
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printf("Output from kernel verifier:\n%s\n-------\n",
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bpf_log_buf);
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return EXIT_FAILURE;
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}
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ret = bpf_prog_attach(prog_fd, cg_fd,
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BPF_CGROUP_INET_SOCK_CREATE, 0);
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if (ret < 0) {
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printf("Failed to attach prog to cgroup: '%s'\n",
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strerror(errno));
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return EXIT_FAILURE;
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}
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} else {
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ret = bpf_prog_detach(cg_fd, BPF_CGROUP_INET_SOCK_CREATE);
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if (ret < 0) {
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printf("Failed to detach prog from cgroup: '%s'\n",
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strerror(errno));
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return EXIT_FAILURE;
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}
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}
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close(cg_fd);
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return EXIT_SUCCESS;
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}
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