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_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ 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 BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ 68 69 BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */ 70 BPF_EXIT_INSN(), 71 }; 72 size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn); 73 74 return bpf_load_program(BPF_PROG_TYPE_CGROUP_SKB, 75 prog, insns_cnt, "GPL", 0, 76 bpf_log_buf, BPF_LOG_BUF_SIZE); 77 } 78 79 static int usage(const char *argv0) 80 { 81 printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0); 82 printf(" -d Drop Traffic\n"); 83 printf(" -D Detach filter, and exit\n"); 84 return EXIT_FAILURE; 85 } 86 87 static int attach_filter(int cg_fd, int type, int verdict) 88 { 89 int prog_fd, map_fd, ret, key; 90 long long pkt_cnt, byte_cnt; 91 92 map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, 93 sizeof(key), sizeof(byte_cnt), 94 256, 0); 95 if (map_fd < 0) { 96 printf("Failed to create map: '%s'\n", strerror(errno)); 97 return EXIT_FAILURE; 98 } 99 100 prog_fd = prog_load(map_fd, verdict); 101 printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf); 102 103 if (prog_fd < 0) { 104 printf("Failed to load prog: '%s'\n", strerror(errno)); 105 return EXIT_FAILURE; 106 } 107 108 ret = bpf_prog_attach(prog_fd, cg_fd, type, 0); 109 if (ret < 0) { 110 printf("Failed to attach prog to cgroup: '%s'\n", 111 strerror(errno)); 112 return EXIT_FAILURE; 113 } 114 while (1) { 115 key = MAP_KEY_PACKETS; 116 assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0); 117 118 key = MAP_KEY_BYTES; 119 assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0); 120 121 printf("cgroup received %lld packets, %lld bytes\n", 122 pkt_cnt, byte_cnt); 123 sleep(1); 124 } 125 126 return EXIT_SUCCESS; 127 } 128 129 int main(int argc, char **argv) 130 { 131 int detach_only = 0, verdict = 1; 132 enum bpf_attach_type type; 133 int opt, cg_fd, ret; 134 135 while ((opt = getopt(argc, argv, "Dd")) != -1) { 136 switch (opt) { 137 case 'd': 138 verdict = 0; 139 break; 140 case 'D': 141 detach_only = 1; 142 break; 143 default: 144 return usage(argv[0]); 145 } 146 } 147 148 if (argc - optind < 2) 149 return usage(argv[0]); 150 151 if (strcmp(argv[optind + 1], "ingress") == 0) 152 type = BPF_CGROUP_INET_INGRESS; 153 else if (strcmp(argv[optind + 1], "egress") == 0) 154 type = BPF_CGROUP_INET_EGRESS; 155 else 156 return usage(argv[0]); 157 158 cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY); 159 if (cg_fd < 0) { 160 printf("Failed to open cgroup path: '%s'\n", strerror(errno)); 161 return EXIT_FAILURE; 162 } 163 164 if (detach_only) { 165 ret = bpf_prog_detach(cg_fd, type); 166 printf("bpf_prog_detach() returned '%s' (%d)\n", 167 strerror(errno), errno); 168 } else 169 ret = attach_filter(cg_fd, type, verdict); 170 171 return ret; 172 } 173