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