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/* 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 rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
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 (setrlimit(RLIMIT_MEMLOCK, &r)) {
perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
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;
}
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