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 <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/* simple "icmp packet too big sent" counter
 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			/* default, set below */
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	/* static global var 'max_pcktsz' is accessible from .data section */
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	/* fetch icmpcnt map */
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}