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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 rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
86 struct bpf_prog_load_attr prog_load_attr = {
87 .prog_type = BPF_PROG_TYPE_XDP,
88 };
89 unsigned char opt_flags[256] = {};
90 const char *optstr = "i:T:P:SNFh";
91 struct bpf_prog_info info = {};
92 __u32 info_len = sizeof(info);
93 unsigned int kill_after_s = 0;
94 int i, prog_fd, map_fd, opt;
95 struct bpf_object *obj;
96 __u32 max_pckt_size = 0;
97 __u32 key = 0;
98 char filename[256];
99 int err;
100
101 for (i = 0; i < strlen(optstr); i++)
102 if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
103 opt_flags[(unsigned char)optstr[i]] = 1;
104
105 while ((opt = getopt(argc, argv, optstr)) != -1) {
106
107 switch (opt) {
108 case 'i':
109 ifindex = if_nametoindex(optarg);
110 if (!ifindex)
111 ifindex = atoi(optarg);
112 break;
113 case 'T':
114 kill_after_s = atoi(optarg);
115 break;
116 case 'P':
117 max_pckt_size = atoi(optarg);
118 break;
119 case 'S':
120 xdp_flags |= XDP_FLAGS_SKB_MODE;
121 break;
122 case 'N':
123
124 break;
125 case 'F':
126 xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
127 break;
128 default:
129 usage(argv[0]);
130 return 1;
131 }
132 opt_flags[opt] = 0;
133 }
134
135 if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
136 xdp_flags |= XDP_FLAGS_DRV_MODE;
137
138 for (i = 0; i < strlen(optstr); i++) {
139 if (opt_flags[(unsigned int)optstr[i]]) {
140 fprintf(stderr, "Missing argument -%c\n", optstr[i]);
141 usage(argv[0]);
142 return 1;
143 }
144 }
145
146 if (setrlimit(RLIMIT_MEMLOCK, &r)) {
147 perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
148 return 1;
149 }
150
151 if (!ifindex) {
152 fprintf(stderr, "Invalid ifname\n");
153 return 1;
154 }
155
156 snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
157 prog_load_attr.file = filename;
158
159 if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
160 return 1;
161
162
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
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_set_link_xdp_fd(ifindex, prog_fd, xdp_flags) < 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
