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 32 #include "libbpf.h" 33 34 enum { 35 MAP_KEY_PACKETS, 36 MAP_KEY_BYTES, 37 }; 38 39 char bpf_log_buf[BPF_LOG_BUF_SIZE]; 40 41 static int prog_load(int map_fd, int verdict) 42 { 43 struct bpf_insn prog[] = { 44 BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */ 45 46 /* Count packets */ 47 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */ 48 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ 49 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), 50 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ 51 BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */ 52 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 53 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), 54 BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */ 55 BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ 56 57 /* Count bytes */ 58 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */ 59 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ 60 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), 61 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ 62 BPF_LD_MAP_FD(BPF_REG_1, map_fd), 63 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 64 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), 65 BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */ 66 BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ 67 68 BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */ 69 BPF_EXIT_INSN(), 70 }; 71 size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn); 72 73 return bpf_load_program(BPF_PROG_TYPE_CGROUP_SKB, 74 prog, insns_cnt, "GPL", 0, 75 bpf_log_buf, BPF_LOG_BUF_SIZE); 76 } 77 78 static int usage(const char *argv0) 79 { 80 printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0); 81 printf(" -d Drop Traffic\n"); 82 printf(" -D Detach filter, and exit\n"); 83 return EXIT_FAILURE; 84 } 85 86 static int attach_filter(int cg_fd, int type, int verdict) 87 { 88 int prog_fd, map_fd, ret, key; 89 long long pkt_cnt, byte_cnt; 90 91 map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, 92 sizeof(key), sizeof(byte_cnt), 93 256, 0); 94 if (map_fd < 0) { 95 printf("Failed to create map: '%s'\n", strerror(errno)); 96 return EXIT_FAILURE; 97 } 98 99 prog_fd = prog_load(map_fd, verdict); 100 printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf); 101 102 if (prog_fd < 0) { 103 printf("Failed to load prog: '%s'\n", strerror(errno)); 104 return EXIT_FAILURE; 105 } 106 107 ret = bpf_prog_attach(prog_fd, cg_fd, type, 0); 108 if (ret < 0) { 109 printf("Failed to attach prog to cgroup: '%s'\n", 110 strerror(errno)); 111 return EXIT_FAILURE; 112 } 113 while (1) { 114 key = MAP_KEY_PACKETS; 115 assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0); 116 117 key = MAP_KEY_BYTES; 118 assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0); 119 120 printf("cgroup received %lld packets, %lld bytes\n", 121 pkt_cnt, byte_cnt); 122 sleep(1); 123 } 124 125 return EXIT_SUCCESS; 126 } 127 128 int main(int argc, char **argv) 129 { 130 int detach_only = 0, verdict = 1; 131 enum bpf_attach_type type; 132 int opt, cg_fd, ret; 133 134 while ((opt = getopt(argc, argv, "Dd")) != -1) { 135 switch (opt) { 136 case 'd': 137 verdict = 0; 138 break; 139 case 'D': 140 detach_only = 1; 141 break; 142 default: 143 return usage(argv[0]); 144 } 145 } 146 147 if (argc - optind < 2) 148 return usage(argv[0]); 149 150 if (strcmp(argv[optind + 1], "ingress") == 0) 151 type = BPF_CGROUP_INET_INGRESS; 152 else if (strcmp(argv[optind + 1], "egress") == 0) 153 type = BPF_CGROUP_INET_EGRESS; 154 else 155 return usage(argv[0]); 156 157 cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY); 158 if (cg_fd < 0) { 159 printf("Failed to open cgroup path: '%s'\n", strerror(errno)); 160 return EXIT_FAILURE; 161 } 162 163 if (detach_only) { 164 ret = bpf_prog_detach(cg_fd, type); 165 printf("bpf_prog_detach() returned '%s' (%d)\n", 166 strerror(errno), errno); 167 } else 168 ret = attach_filter(cg_fd, type, verdict); 169 170 return ret; 171 } 172