tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/* SPDX-License-Identifier: GPL-2.0
2 * Copyright (c) 2018 Facebook
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of version 2 of the GNU General Public
6 * License as published by the Free Software Foundation.
7 */
8#include <linux/bpf.h>
9#include <linux/if_link.h>
10#include <assert.h>
11#include <errno.h>
12#include <signal.h>
13#include <stdio.h>
14#include <stdlib.h>
15#include <string.h>
16#include <net/if.h>
17#include <sys/resource.h>
18#include <arpa/inet.h>
19#include <netinet/ether.h>
20#include <unistd.h>
21#include <time.h>
22#include <bpf/bpf.h>
23#include <bpf/libbpf.h>
24
25#define STATS_INTERVAL_S 2U
26#define MAX_PCKT_SIZE 600
27
28static int ifindex = -1;
29static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
30static __u32 prog_id;
31
32static void int_exit(int sig)
33{
34 __u32 curr_prog_id = 0;
35
36 if (ifindex > -1) {
37 if (bpf_xdp_query_id(ifindex, xdp_flags, &curr_prog_id)) {
38 printf("bpf_xdp_query_id failed\n");
39 exit(1);
40 }
41 if (prog_id == curr_prog_id)
42 bpf_xdp_detach(ifindex, xdp_flags, NULL);
43 else if (!curr_prog_id)
44 printf("couldn't find a prog id on a given iface\n");
45 else
46 printf("program on interface changed, not removing\n");
47 }
48 exit(0);
49}
50
51/* simple "icmp packet too big sent" counter
52 */
53static void poll_stats(unsigned int map_fd, unsigned int kill_after_s)
54{
55 time_t started_at = time(NULL);
56 __u64 value = 0;
57 int key = 0;
58
59
60 while (!kill_after_s || time(NULL) - started_at <= kill_after_s) {
61 sleep(STATS_INTERVAL_S);
62
63 assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
64
65 printf("icmp \"packet too big\" sent: %10llu pkts\n", value);
66 }
67}
68
69static void usage(const char *cmd)
70{
71 printf("Start a XDP prog which send ICMP \"packet too big\" \n"
72 "messages if ingress packet is bigger then MAX_SIZE bytes\n");
73 printf("Usage: %s [...]\n", cmd);
74 printf(" -i <ifname|ifindex> Interface\n");
75 printf(" -T <stop-after-X-seconds> Default: 0 (forever)\n");
76 printf(" -P <MAX_PCKT_SIZE> Default: %u\n", MAX_PCKT_SIZE);
77 printf(" -S use skb-mode\n");
78 printf(" -N enforce native mode\n");
79 printf(" -F force loading prog\n");
80 printf(" -h Display this help\n");
81}
82
83int main(int argc, char **argv)
84{
85 unsigned char opt_flags[256] = {};
86 const char *optstr = "i:T:P:SNFh";
87 struct bpf_prog_info info = {};
88 __u32 info_len = sizeof(info);
89 unsigned int kill_after_s = 0;
90 int i, prog_fd, map_fd, opt;
91 struct bpf_program *prog;
92 struct bpf_object *obj;
93 __u32 max_pckt_size = 0;
94 __u32 key = 0;
95 char filename[256];
96 int err;
97
98 for (i = 0; i < strlen(optstr); i++)
99 if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
100 opt_flags[(unsigned char)optstr[i]] = 1;
101
102 while ((opt = getopt(argc, argv, optstr)) != -1) {
103
104 switch (opt) {
105 case 'i':
106 ifindex = if_nametoindex(optarg);
107 if (!ifindex)
108 ifindex = atoi(optarg);
109 break;
110 case 'T':
111 kill_after_s = atoi(optarg);
112 break;
113 case 'P':
114 max_pckt_size = atoi(optarg);
115 break;
116 case 'S':
117 xdp_flags |= XDP_FLAGS_SKB_MODE;
118 break;
119 case 'N':
120 /* default, set below */
121 break;
122 case 'F':
123 xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
124 break;
125 default:
126 usage(argv[0]);
127 return 1;
128 }
129 opt_flags[opt] = 0;
130 }
131
132 if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
133 xdp_flags |= XDP_FLAGS_DRV_MODE;
134
135 for (i = 0; i < strlen(optstr); i++) {
136 if (opt_flags[(unsigned int)optstr[i]]) {
137 fprintf(stderr, "Missing argument -%c\n", optstr[i]);
138 usage(argv[0]);
139 return 1;
140 }
141 }
142
143 if (!ifindex) {
144 fprintf(stderr, "Invalid ifname\n");
145 return 1;
146 }
147
148 snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
149
150 obj = bpf_object__open_file(filename, NULL);
151 if (libbpf_get_error(obj))
152 return 1;
153
154 prog = bpf_object__next_program(obj, NULL);
155 bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);
156
157 err = bpf_object__load(obj);
158 if (err)
159 return 1;
160
161 prog_fd = bpf_program__fd(prog);
162
163 /* static global var 'max_pcktsz' is accessible from .data section */
164 if (max_pckt_size) {
165 map_fd = bpf_object__find_map_fd_by_name(obj, "xdp_adju.data");
166 if (map_fd < 0) {
167 printf("finding a max_pcktsz map in obj file failed\n");
168 return 1;
169 }
170 bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY);
171 }
172
173 /* fetch icmpcnt map */
174 map_fd = bpf_object__find_map_fd_by_name(obj, "icmpcnt");
175 if (map_fd < 0) {
176 printf("finding a icmpcnt map in obj file failed\n");
177 return 1;
178 }
179
180 signal(SIGINT, int_exit);
181 signal(SIGTERM, int_exit);
182
183 if (bpf_xdp_attach(ifindex, prog_fd, xdp_flags, NULL) < 0) {
184 printf("link set xdp fd failed\n");
185 return 1;
186 }
187
188 err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
189 if (err) {
190 printf("can't get prog info - %s\n", strerror(errno));
191 return 1;
192 }
193 prog_id = info.id;
194
195 poll_stats(map_fd, kill_after_s);
196 int_exit(0);
197
198 return 0;
199}