1 /* eBPF example program: 2 * 3 * - Creates arraymap in kernel with 4 bytes keys and 8 byte values 4 * 5 * - Loads eBPF program 6 * 7 * The eBPF program accesses the map passed in to store two pieces of 8 * information. The number of invocations of the program, which maps 9 * to the number of packets received, is stored to key 0. Key 1 is 10 * incremented on each iteration by the number of bytes stored in 11 * the skb. 12 * 13 * - Attaches the new program to a cgroup using BPF_PROG_ATTACH 14 * 15 * - Every second, reads map[0] and map[1] to see how many bytes and 16 * packets were seen on any socket of tasks in the given cgroup. 17 */ 18 19 #define _GNU_SOURCE 20 21 #include <stdio.h> 22 #include <stdlib.h> 23 #include <stddef.h> 24 #include <string.h> 25 #include <unistd.h> 26 #include <assert.h> 27 #include <errno.h> 28 #include <fcntl.h> 29 30 #include <linux/bpf.h> 31 #include <bpf/bpf.h> 32 33 #include "bpf_insn.h" 34 35 enum { 36 MAP_KEY_PACKETS, 37 MAP_KEY_BYTES, 38 }; 39 40 char bpf_log_buf[BPF_LOG_BUF_SIZE]; 41 42 static int prog_load(int map_fd, int verdict) 43 { 44 struct bpf_insn prog[] = { 45 BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */ 46 47 /* Count packets */ 48 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */ 49 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ 50 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), 51 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ 52 BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */ 53 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 54 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), 55 BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */ 56 BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0), 57 58 /* Count bytes */ 59 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */ 60 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ 61 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), 62 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ 63 BPF_LD_MAP_FD(BPF_REG_1, map_fd), 64 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 65 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), 66 BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */ 67 68 BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0), 69 70 BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */ 71 BPF_EXIT_INSN(), 72 }; 73 size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn); 74 LIBBPF_OPTS(bpf_prog_load_opts, opts, 75 .log_buf = bpf_log_buf, 76 .log_size = BPF_LOG_BUF_SIZE, 77 ); 78 79 return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB, NULL, "GPL", 80 prog, insns_cnt, &opts); 81 } 82 83 static int usage(const char *argv0) 84 { 85 printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0); 86 printf(" -d Drop Traffic\n"); 87 printf(" -D Detach filter, and exit\n"); 88 return EXIT_FAILURE; 89 } 90 91 static int attach_filter(int cg_fd, int type, int verdict) 92 { 93 int prog_fd, map_fd, ret, key; 94 long long pkt_cnt, byte_cnt; 95 96 map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, 97 sizeof(key), sizeof(byte_cnt), 98 256, NULL); 99 if (map_fd < 0) { 100 printf("Failed to create map: '%s'\n", strerror(errno)); 101 return EXIT_FAILURE; 102 } 103 104 prog_fd = prog_load(map_fd, verdict); 105 printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf); 106 107 if (prog_fd < 0) { 108 printf("Failed to load prog: '%s'\n", strerror(errno)); 109 return EXIT_FAILURE; 110 } 111 112 ret = bpf_prog_attach(prog_fd, cg_fd, type, 0); 113 if (ret < 0) { 114 printf("Failed to attach prog to cgroup: '%s'\n", 115 strerror(errno)); 116 return EXIT_FAILURE; 117 } 118 while (1) { 119 key = MAP_KEY_PACKETS; 120 assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0); 121 122 key = MAP_KEY_BYTES; 123 assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0); 124 125 printf("cgroup received %lld packets, %lld bytes\n", 126 pkt_cnt, byte_cnt); 127 sleep(1); 128 } 129 130 return EXIT_SUCCESS; 131 } 132 133 int main(int argc, char **argv) 134 { 135 int detach_only = 0, verdict = 1; 136 enum bpf_attach_type type; 137 int opt, cg_fd, ret; 138 139 while ((opt = getopt(argc, argv, "Dd")) != -1) { 140 switch (opt) { 141 case 'd': 142 verdict = 0; 143 break; 144 case 'D': 145 detach_only = 1; 146 break; 147 default: 148 return usage(argv[0]); 149 } 150 } 151 152 if (argc - optind < 2) 153 return usage(argv[0]); 154 155 if (strcmp(argv[optind + 1], "ingress") == 0) 156 type = BPF_CGROUP_INET_INGRESS; 157 else if (strcmp(argv[optind + 1], "egress") == 0) 158 type = BPF_CGROUP_INET_EGRESS; 159 else 160 return usage(argv[0]); 161 162 cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY); 163 if (cg_fd < 0) { 164 printf("Failed to open cgroup path: '%s'\n", strerror(errno)); 165 return EXIT_FAILURE; 166 } 167 168 if (detach_only) { 169 ret = bpf_prog_detach(cg_fd, type); 170 printf("bpf_prog_detach() returned '%s' (%d)\n", 171 strerror(errno), errno); 172 } else 173 ret = attach_filter(cg_fd, type, verdict); 174 175 return ret; 176 } 177