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 <sys/resource.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 
26 static int ifindex = -1;
27 static __u32 xdp_flags;
28 
29 static void int_exit(int sig)
30 {
31 	if (ifindex > -1)
32 		bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
33 	exit(0);
34 }
35 
36 /* simple "icmp packet too big sent" counter
37  */
38 static void poll_stats(unsigned int map_fd, unsigned int kill_after_s)
39 {
40 	time_t started_at = time(NULL);
41 	__u64 value = 0;
42 	int key = 0;
43 
44 
45 	while (!kill_after_s || time(NULL) - started_at <= kill_after_s) {
46 		sleep(STATS_INTERVAL_S);
47 
48 		assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
49 
50 		printf("icmp \"packet too big\" sent: %10llu pkts\n", value);
51 	}
52 }
53 
54 static void usage(const char *cmd)
55 {
56 	printf("Start a XDP prog which send ICMP \"packet too big\" \n"
57 		"messages if ingress packet is bigger then MAX_SIZE bytes\n");
58 	printf("Usage: %s [...]\n", cmd);
59 	printf("    -i <ifindex> Interface Index\n");
60 	printf("    -T <stop-after-X-seconds> Default: 0 (forever)\n");
61 	printf("    -S use skb-mode\n");
62 	printf("    -N enforce native mode\n");
63 	printf("    -h Display this help\n");
64 }
65 
66 int main(int argc, char **argv)
67 {
68 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
69 	struct bpf_prog_load_attr prog_load_attr = {
70 		.prog_type	= BPF_PROG_TYPE_XDP,
71 	};
72 	unsigned char opt_flags[256] = {};
73 	unsigned int kill_after_s = 0;
74 	const char *optstr = "i:T:SNh";
75 	int i, prog_fd, map_fd, opt;
76 	struct bpf_object *obj;
77 	struct bpf_map *map;
78 	char filename[256];
79 
80 	for (i = 0; i < strlen(optstr); i++)
81 		if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
82 			opt_flags[(unsigned char)optstr[i]] = 1;
83 
84 	while ((opt = getopt(argc, argv, optstr)) != -1) {
85 
86 		switch (opt) {
87 		case 'i':
88 			ifindex = atoi(optarg);
89 			break;
90 		case 'T':
91 			kill_after_s = atoi(optarg);
92 			break;
93 		case 'S':
94 			xdp_flags |= XDP_FLAGS_SKB_MODE;
95 			break;
96 		case 'N':
97 			xdp_flags |= XDP_FLAGS_DRV_MODE;
98 			break;
99 		default:
100 			usage(argv[0]);
101 			return 1;
102 		}
103 		opt_flags[opt] = 0;
104 	}
105 
106 	for (i = 0; i < strlen(optstr); i++) {
107 		if (opt_flags[(unsigned int)optstr[i]]) {
108 			fprintf(stderr, "Missing argument -%c\n", optstr[i]);
109 			usage(argv[0]);
110 			return 1;
111 		}
112 	}
113 
114 	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
115 		perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
116 		return 1;
117 	}
118 
119 	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
120 	prog_load_attr.file = filename;
121 
122 	if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
123 		return 1;
124 
125 	map = bpf_map__next(NULL, obj);
126 	if (!map) {
127 		printf("finding a map in obj file failed\n");
128 		return 1;
129 	}
130 	map_fd = bpf_map__fd(map);
131 
132 	if (!prog_fd) {
133 		printf("load_bpf_file: %s\n", strerror(errno));
134 		return 1;
135 	}
136 
137 	signal(SIGINT, int_exit);
138 	signal(SIGTERM, int_exit);
139 
140 	if (bpf_set_link_xdp_fd(ifindex, prog_fd, xdp_flags) < 0) {
141 		printf("link set xdp fd failed\n");
142 		return 1;
143 	}
144 
145 	poll_stats(map_fd, kill_after_s);
146 
147 	bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
148 
149 	return 0;
150 }
151