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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 
 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 

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