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