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TOMOYO Linux Cross Reference
Linux/samples/bpf/test_cgrp2_attach.c

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  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 

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