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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_get_link_xdp_id(ifindex, &curr_prog_id, xdp_flags)) {
38 printf("bpf_get_link_xdp_id failed\n");
39 exit(1);
40 }
41 if (prog_id == curr_prog_id)
42 bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
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
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 struct bpf_prog_load_attr prog_load_attr = {
86 .prog_type = BPF_PROG_TYPE_XDP,
87 };
88 unsigned char opt_flags[256] = {};
89 const char *optstr = "i:T:P:SNFh";
90 struct bpf_prog_info info = {};
91 __u32 info_len = sizeof(info);
92 unsigned int kill_after_s = 0;
93 int i, prog_fd, map_fd, opt;
94 struct bpf_object *obj;
95 __u32 max_pckt_size = 0;
96 __u32 key = 0;
97 char filename[256];
98 int err;
99
100 for (i = 0; i < strlen(optstr); i++)
101 if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
102 opt_flags[(unsigned char)optstr[i]] = 1;
103
104 while ((opt = getopt(argc, argv, optstr)) != -1) {
105
106 switch (opt) {
107 case 'i':
108 ifindex = if_nametoindex(optarg);
109 if (!ifindex)
110 ifindex = atoi(optarg);
111 break;
112 case 'T':
113 kill_after_s = atoi(optarg);
114 break;
115 case 'P':
116 max_pckt_size = atoi(optarg);
117 break;
118 case 'S':
119 xdp_flags |= XDP_FLAGS_SKB_MODE;
120 break;
121 case 'N':
122
123 break;
124 case 'F':
125 xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
126 break;
127 default:
128 usage(argv[0]);
129 return 1;
130 }
131 opt_flags[opt] = 0;
132 }
133
134 if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
135 xdp_flags |= XDP_FLAGS_DRV_MODE;
136
137 for (i = 0; i < strlen(optstr); i++) {
138 if (opt_flags[(unsigned int)optstr[i]]) {
139 fprintf(stderr, "Missing argument -%c\n", optstr[i]);
140 usage(argv[0]);
141 return 1;
142 }
143 }
144
145 if (!ifindex) {
146 fprintf(stderr, "Invalid ifname\n");
147 return 1;
148 }
149
150 snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
151 prog_load_attr.file = filename;
152
153 if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
154 return 1;
155
156
157 if (max_pckt_size) {
158 map_fd = bpf_object__find_map_fd_by_name(obj, "xdp_adju.data");
159 if (map_fd < 0) {
160 printf("finding a max_pcktsz map in obj file failed\n");
161 return 1;
162 }
163 bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY);
164 }
165
166
167 map_fd = bpf_object__find_map_fd_by_name(obj, "icmpcnt");
168 if (map_fd < 0) {
169 printf("finding a icmpcnt map in obj file failed\n");
170 return 1;
171 }
172
173 signal(SIGINT, int_exit);
174 signal(SIGTERM, int_exit);
175
176 if (bpf_set_link_xdp_fd(ifindex, prog_fd, xdp_flags) < 0) {
177 printf("link set xdp fd failed\n");
178 return 1;
179 }
180
181 err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
182 if (err) {
183 printf("can't get prog info - %s\n", strerror(errno));
184 return 1;
185 }
186 prog_id = info.id;
187
188 poll_stats(map_fd, kill_after_s);
189 int_exit(0);
190
191 return 0;
192}
193
