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 <arpa/inet.h>
 18#include <netinet/ether.h>
 19#include <unistd.h>
 20#include <time.h>
 21#include <bpf/bpf.h>
 22#include <bpf/libbpf.h>
 23
 24#define STATS_INTERVAL_S 2U
 25#define MAX_PCKT_SIZE 600
 26
 27static int ifindex = -1;
 28static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
 29static __u32 prog_id;
 30
 31static void int_exit(int sig)
 32{
 33	__u32 curr_prog_id = 0;
 34
 35	if (ifindex > -1) {
 36		if (bpf_xdp_query_id(ifindex, xdp_flags, &curr_prog_id)) {
 37			printf("bpf_xdp_query_id failed\n");
 38			exit(1);
 39		}
 40		if (prog_id == curr_prog_id)
 41			bpf_xdp_detach(ifindex, xdp_flags, NULL);
 42		else if (!curr_prog_id)
 43			printf("couldn't find a prog id on a given iface\n");
 44		else
 45			printf("program on interface changed, not removing\n");
 46	}
 47	exit(0);
 48}
 49
 50/* simple "icmp packet too big sent" counter
 51 */
 52static void poll_stats(unsigned int map_fd, unsigned int kill_after_s)
 53{
 54	time_t started_at = time(NULL);
 55	__u64 value = 0;
 56	int key = 0;
 57
 58
 59	while (!kill_after_s || time(NULL) - started_at <= kill_after_s) {
 60		sleep(STATS_INTERVAL_S);
 61
 62		assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
 63
 64		printf("icmp \"packet too big\" sent: %10llu pkts\n", value);
 65	}
 66}
 67
 68static void usage(const char *cmd)
 69{
 70	printf("Start a XDP prog which send ICMP \"packet too big\" \n"
 71		"messages if ingress packet is bigger then MAX_SIZE bytes\n");
 72	printf("Usage: %s [...]\n", cmd);
 73	printf("    -i <ifname|ifindex> Interface\n");
 74	printf("    -T <stop-after-X-seconds> Default: 0 (forever)\n");
 75	printf("    -P <MAX_PCKT_SIZE> Default: %u\n", MAX_PCKT_SIZE);
 76	printf("    -S use skb-mode\n");
 77	printf("    -N enforce native mode\n");
 78	printf("    -F force loading prog\n");
 79	printf("    -h Display this help\n");
 80}
 81
 82int main(int argc, char **argv)
 83{
 84	unsigned char opt_flags[256] = {};
 85	const char *optstr = "i:T:P:SNFh";
 86	struct bpf_prog_info info = {};
 87	__u32 info_len = sizeof(info);
 88	unsigned int kill_after_s = 0;
 89	int i, prog_fd, map_fd, opt;
 90	struct bpf_program *prog;
 91	struct bpf_object *obj;
 92	__u32 max_pckt_size = 0;
 93	__u32 key = 0;
 94	char filename[256];
 95	int err;
 96
 97	for (i = 0; i < strlen(optstr); i++)
 98		if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
 99			opt_flags[(unsigned char)optstr[i]] = 1;
100
101	while ((opt = getopt(argc, argv, optstr)) != -1) {
102
103		switch (opt) {
104		case 'i':
105			ifindex = if_nametoindex(optarg);
106			if (!ifindex)
107				ifindex = atoi(optarg);
108			break;
109		case 'T':
110			kill_after_s = atoi(optarg);
111			break;
112		case 'P':
113			max_pckt_size = atoi(optarg);
114			break;
115		case 'S':
116			xdp_flags |= XDP_FLAGS_SKB_MODE;
117			break;
118		case 'N':
119			/* default, set below */
120			break;
121		case 'F':
122			xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
123			break;
124		default:
125			usage(argv[0]);
126			return 1;
127		}
128		opt_flags[opt] = 0;
129	}
130
131	if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
132		xdp_flags |= XDP_FLAGS_DRV_MODE;
133
134	for (i = 0; i < strlen(optstr); i++) {
135		if (opt_flags[(unsigned int)optstr[i]]) {
136			fprintf(stderr, "Missing argument -%c\n", optstr[i]);
137			usage(argv[0]);
138			return 1;
139		}
140	}
141
142	if (!ifindex) {
143		fprintf(stderr, "Invalid ifname\n");
144		return 1;
145	}
146
147	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
148
149	obj = bpf_object__open_file(filename, NULL);
150	if (libbpf_get_error(obj))
151		return 1;
152
153	prog = bpf_object__next_program(obj, NULL);
154	bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);
155
156	err = bpf_object__load(obj);
157	if (err)
158		return 1;
159
160	prog_fd = bpf_program__fd(prog);
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_xdp_attach(ifindex, prog_fd, xdp_flags, NULL) < 0) {
183		printf("link set xdp fd failed\n");
184		return 1;
185	}
186
187	err = bpf_prog_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}