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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 | /* eBPF example program: * * - Creates arraymap in kernel with 4 bytes keys and 8 byte values * * - Loads eBPF program * * The eBPF program accesses the map passed in to store two pieces of * information. The number of invocations of the program, which maps * to the number of packets received, is stored to key 0. Key 1 is * incremented on each iteration by the number of bytes stored in * the skb. * * - Attaches the new program to a cgroup using BPF_PROG_ATTACH * * - Every second, reads map[0] and map[1] to see how many bytes and * packets were seen on any socket of tasks in the given cgroup. */ #define _GNU_SOURCE #include <stdio.h> #include <stdlib.h> #include <stddef.h> #include <string.h> #include <unistd.h> #include <assert.h> #include <errno.h> #include <fcntl.h> #include <linux/bpf.h> #include <bpf/bpf.h> #include "bpf_insn.h" enum { MAP_KEY_PACKETS, MAP_KEY_BYTES, }; char bpf_log_buf[BPF_LOG_BUF_SIZE]; static int prog_load(int map_fd, int verdict) { struct bpf_insn prog[] = { BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */ /* Count packets */ BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */ BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */ BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0), /* Count bytes */ BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */ BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ BPF_LD_MAP_FD(BPF_REG_1, map_fd), BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */ BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0), BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */ BPF_EXIT_INSN(), }; size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn); LIBBPF_OPTS(bpf_prog_load_opts, opts, .log_buf = bpf_log_buf, .log_size = BPF_LOG_BUF_SIZE, ); return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB, NULL, "GPL", prog, insns_cnt, &opts); } static int usage(const char *argv0) { printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0); printf(" -d Drop Traffic\n"); printf(" -D Detach filter, and exit\n"); return EXIT_FAILURE; } static int attach_filter(int cg_fd, int type, int verdict) { int prog_fd, map_fd, ret, key; long long pkt_cnt, byte_cnt; map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(key), sizeof(byte_cnt), 256, NULL); if (map_fd < 0) { printf("Failed to create map: '%s'\n", strerror(errno)); return EXIT_FAILURE; } prog_fd = prog_load(map_fd, verdict); printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf); if (prog_fd < 0) { printf("Failed to load prog: '%s'\n", strerror(errno)); return EXIT_FAILURE; } ret = bpf_prog_attach(prog_fd, cg_fd, type, 0); if (ret < 0) { printf("Failed to attach prog to cgroup: '%s'\n", strerror(errno)); return EXIT_FAILURE; } while (1) { key = MAP_KEY_PACKETS; assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0); key = MAP_KEY_BYTES; assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0); printf("cgroup received %lld packets, %lld bytes\n", pkt_cnt, byte_cnt); sleep(1); } return EXIT_SUCCESS; } int main(int argc, char **argv) { int detach_only = 0, verdict = 1; enum bpf_attach_type type; int opt, cg_fd, ret; while ((opt = getopt(argc, argv, "Dd")) != -1) { switch (opt) { case 'd': verdict = 0; break; case 'D': detach_only = 1; break; default: return usage(argv[0]); } } if (argc - optind < 2) return usage(argv[0]); if (strcmp(argv[optind + 1], "ingress") == 0) type = BPF_CGROUP_INET_INGRESS; else if (strcmp(argv[optind + 1], "egress") == 0) type = BPF_CGROUP_INET_EGRESS; else return usage(argv[0]); cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY); if (cg_fd < 0) { printf("Failed to open cgroup path: '%s'\n", strerror(errno)); return EXIT_FAILURE; } if (detach_only) { ret = bpf_prog_detach(cg_fd, type); printf("bpf_prog_detach() returned '%s' (%d)\n", strerror(errno), errno); } else ret = attach_filter(cg_fd, type, verdict); return ret; } |