1 // SPDX-License-Identifier: LGPL-2.1 OR BSD-2-Clause
2 /* Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */
3 
4 #include <stdnoreturn.h>
5 #include <stdlib.h>
6 #include <stdio.h>
7 #include <string.h>
8 #include <errno.h>
9 #include <unistd.h>
10 #include <getopt.h>
11 #include <signal.h>
12 #include <sys/types.h>
13 #include <bpf/bpf.h>
14 #include <bpf/libbpf.h>
15 #include <net/if.h>
16 #include <linux/if_link.h>
17 #include <linux/limits.h>
18 
19 static unsigned int ifindex;
20 static __u32 attached_prog_id;
21 static bool attached_tc;
22 
23 static void noreturn cleanup(int sig)
24 {
25 	LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
26 	int prog_fd;
27 	int err;
28 
29 	if (attached_prog_id == 0)
30 		exit(0);
31 
32 	if (attached_tc) {
33 		LIBBPF_OPTS(bpf_tc_hook, hook,
34 			    .ifindex = ifindex,
35 			    .attach_point = BPF_TC_INGRESS);
36 
37 		err = bpf_tc_hook_destroy(&hook);
38 		if (err < 0) {
39 			fprintf(stderr, "Error: bpf_tc_hook_destroy: %s\n", strerror(-err));
40 			fprintf(stderr, "Failed to destroy the TC hook\n");
41 			exit(1);
42 		}
43 		exit(0);
44 	}
45 
46 	prog_fd = bpf_prog_get_fd_by_id(attached_prog_id);
47 	if (prog_fd < 0) {
48 		fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
49 		err = bpf_xdp_attach(ifindex, -1, 0, NULL);
50 		if (err < 0) {
51 			fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n", strerror(-err));
52 			fprintf(stderr, "Failed to detach XDP program\n");
53 			exit(1);
54 		}
55 	} else {
56 		opts.old_prog_fd = prog_fd;
57 		err = bpf_xdp_attach(ifindex, -1, XDP_FLAGS_REPLACE, &opts);
58 		close(prog_fd);
59 		if (err < 0) {
60 			fprintf(stderr, "Error: bpf_set_link_xdp_fd_opts: %s\n", strerror(-err));
61 			/* Not an error if already replaced by someone else. */
62 			if (err != -EEXIST) {
63 				fprintf(stderr, "Failed to detach XDP program\n");
64 				exit(1);
65 			}
66 		}
67 	}
68 	exit(0);
69 }
70 
71 static noreturn void usage(const char *progname)
72 {
73 	fprintf(stderr, "Usage: %s [--iface <iface>|--prog <prog_id>] [--mss4 <mss ipv4> --mss6 <mss ipv6> --wscale <wscale> --ttl <ttl>] [--ports <port1>,<port2>,...] [--single] [--tc]\n",
74 		progname);
75 	exit(1);
76 }
77 
78 static unsigned long parse_arg_ul(const char *progname, const char *arg, unsigned long limit)
79 {
80 	unsigned long res;
81 	char *endptr;
82 
83 	errno = 0;
84 	res = strtoul(arg, &endptr, 10);
85 	if (errno != 0 || *endptr != '\0' || arg[0] == '\0' || res > limit)
86 		usage(progname);
87 
88 	return res;
89 }
90 
91 static void parse_options(int argc, char *argv[], unsigned int *ifindex, __u32 *prog_id,
92 			  __u64 *tcpipopts, char **ports, bool *single, bool *tc)
93 {
94 	static struct option long_options[] = {
95 		{ "help", no_argument, NULL, 'h' },
96 		{ "iface", required_argument, NULL, 'i' },
97 		{ "prog", required_argument, NULL, 'x' },
98 		{ "mss4", required_argument, NULL, 4 },
99 		{ "mss6", required_argument, NULL, 6 },
100 		{ "wscale", required_argument, NULL, 'w' },
101 		{ "ttl", required_argument, NULL, 't' },
102 		{ "ports", required_argument, NULL, 'p' },
103 		{ "single", no_argument, NULL, 's' },
104 		{ "tc", no_argument, NULL, 'c' },
105 		{ NULL, 0, NULL, 0 },
106 	};
107 	unsigned long mss4, wscale, ttl;
108 	unsigned long long mss6;
109 	unsigned int tcpipopts_mask = 0;
110 
111 	if (argc < 2)
112 		usage(argv[0]);
113 
114 	*ifindex = 0;
115 	*prog_id = 0;
116 	*tcpipopts = 0;
117 	*ports = NULL;
118 	*single = false;
119 	*tc = false;
120 
121 	while (true) {
122 		int opt;
123 
124 		opt = getopt_long(argc, argv, "", long_options, NULL);
125 		if (opt == -1)
126 			break;
127 
128 		switch (opt) {
129 		case 'h':
130 			usage(argv[0]);
131 			break;
132 		case 'i':
133 			*ifindex = if_nametoindex(optarg);
134 			if (*ifindex == 0)
135 				usage(argv[0]);
136 			break;
137 		case 'x':
138 			*prog_id = parse_arg_ul(argv[0], optarg, UINT32_MAX);
139 			if (*prog_id == 0)
140 				usage(argv[0]);
141 			break;
142 		case 4:
143 			mss4 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
144 			tcpipopts_mask |= 1 << 0;
145 			break;
146 		case 6:
147 			mss6 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
148 			tcpipopts_mask |= 1 << 1;
149 			break;
150 		case 'w':
151 			wscale = parse_arg_ul(argv[0], optarg, 14);
152 			tcpipopts_mask |= 1 << 2;
153 			break;
154 		case 't':
155 			ttl = parse_arg_ul(argv[0], optarg, UINT8_MAX);
156 			tcpipopts_mask |= 1 << 3;
157 			break;
158 		case 'p':
159 			*ports = optarg;
160 			break;
161 		case 's':
162 			*single = true;
163 			break;
164 		case 'c':
165 			*tc = true;
166 			break;
167 		default:
168 			usage(argv[0]);
169 		}
170 	}
171 	if (optind < argc)
172 		usage(argv[0]);
173 
174 	if (tcpipopts_mask == 0xf) {
175 		if (mss4 == 0 || mss6 == 0 || wscale == 0 || ttl == 0)
176 			usage(argv[0]);
177 		*tcpipopts = (mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;
178 	} else if (tcpipopts_mask != 0) {
179 		usage(argv[0]);
180 	}
181 
182 	if (*ifindex != 0 && *prog_id != 0)
183 		usage(argv[0]);
184 	if (*ifindex == 0 && *prog_id == 0)
185 		usage(argv[0]);
186 }
187 
188 static int syncookie_attach(const char *argv0, unsigned int ifindex, bool tc)
189 {
190 	struct bpf_prog_info info = {};
191 	__u32 info_len = sizeof(info);
192 	char xdp_filename[PATH_MAX];
193 	struct bpf_program *prog;
194 	struct bpf_object *obj;
195 	int prog_fd;
196 	int err;
197 
198 	snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.bpf.o", argv0);
199 	obj = bpf_object__open_file(xdp_filename, NULL);
200 	err = libbpf_get_error(obj);
201 	if (err < 0) {
202 		fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
203 		return err;
204 	}
205 
206 	err = bpf_object__load(obj);
207 	if (err < 0) {
208 		fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
209 		return err;
210 	}
211 
212 	prog = bpf_object__find_program_by_name(obj, tc ? "syncookie_tc" : "syncookie_xdp");
213 	if (!prog) {
214 		fprintf(stderr, "Error: bpf_object__find_program_by_name: program was not found\n");
215 		return -ENOENT;
216 	}
217 
218 	prog_fd = bpf_program__fd(prog);
219 
220 	err = bpf_prog_get_info_by_fd(prog_fd, &info, &info_len);
221 	if (err < 0) {
222 		fprintf(stderr, "Error: bpf_prog_get_info_by_fd: %s\n",
223 			strerror(-err));
224 		goto out;
225 	}
226 	attached_tc = tc;
227 	attached_prog_id = info.id;
228 	signal(SIGINT, cleanup);
229 	signal(SIGTERM, cleanup);
230 	if (tc) {
231 		LIBBPF_OPTS(bpf_tc_hook, hook,
232 			    .ifindex = ifindex,
233 			    .attach_point = BPF_TC_INGRESS);
234 		LIBBPF_OPTS(bpf_tc_opts, opts,
235 			    .handle = 1,
236 			    .priority = 1,
237 			    .prog_fd = prog_fd);
238 
239 		err = bpf_tc_hook_create(&hook);
240 		if (err < 0) {
241 			fprintf(stderr, "Error: bpf_tc_hook_create: %s\n",
242 				strerror(-err));
243 			goto fail;
244 		}
245 		err = bpf_tc_attach(&hook, &opts);
246 		if (err < 0) {
247 			fprintf(stderr, "Error: bpf_tc_attach: %s\n",
248 				strerror(-err));
249 			goto fail;
250 		}
251 
252 	} else {
253 		err = bpf_xdp_attach(ifindex, prog_fd,
254 				     XDP_FLAGS_UPDATE_IF_NOEXIST, NULL);
255 		if (err < 0) {
256 			fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n",
257 				strerror(-err));
258 			goto fail;
259 		}
260 	}
261 	err = 0;
262 out:
263 	bpf_object__close(obj);
264 	return err;
265 fail:
266 	signal(SIGINT, SIG_DFL);
267 	signal(SIGTERM, SIG_DFL);
268 	attached_prog_id = 0;
269 	goto out;
270 }
271 
272 static int syncookie_open_bpf_maps(__u32 prog_id, int *values_map_fd, int *ports_map_fd)
273 {
274 	struct bpf_prog_info prog_info;
275 	__u32 map_ids[8];
276 	__u32 info_len;
277 	int prog_fd;
278 	int err;
279 	int i;
280 
281 	*values_map_fd = -1;
282 	*ports_map_fd = -1;
283 
284 	prog_fd = bpf_prog_get_fd_by_id(prog_id);
285 	if (prog_fd < 0) {
286 		fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
287 		return prog_fd;
288 	}
289 
290 	prog_info = (struct bpf_prog_info) {
291 		.nr_map_ids = 8,
292 		.map_ids = (__u64)(unsigned long)map_ids,
293 	};
294 	info_len = sizeof(prog_info);
295 
296 	err = bpf_prog_get_info_by_fd(prog_fd, &prog_info, &info_len);
297 	if (err != 0) {
298 		fprintf(stderr, "Error: bpf_prog_get_info_by_fd: %s\n",
299 			strerror(-err));
300 		goto out;
301 	}
302 
303 	if (prog_info.nr_map_ids < 2) {
304 		fprintf(stderr, "Error: Found %u BPF maps, expected at least 2\n",
305 			prog_info.nr_map_ids);
306 		err = -ENOENT;
307 		goto out;
308 	}
309 
310 	for (i = 0; i < prog_info.nr_map_ids; i++) {
311 		struct bpf_map_info map_info = {};
312 		int map_fd;
313 
314 		err = bpf_map_get_fd_by_id(map_ids[i]);
315 		if (err < 0) {
316 			fprintf(stderr, "Error: bpf_map_get_fd_by_id: %s\n", strerror(-err));
317 			goto err_close_map_fds;
318 		}
319 		map_fd = err;
320 
321 		info_len = sizeof(map_info);
322 		err = bpf_map_get_info_by_fd(map_fd, &map_info, &info_len);
323 		if (err != 0) {
324 			fprintf(stderr, "Error: bpf_map_get_info_by_fd: %s\n",
325 				strerror(-err));
326 			close(map_fd);
327 			goto err_close_map_fds;
328 		}
329 		if (strcmp(map_info.name, "values") == 0) {
330 			*values_map_fd = map_fd;
331 			continue;
332 		}
333 		if (strcmp(map_info.name, "allowed_ports") == 0) {
334 			*ports_map_fd = map_fd;
335 			continue;
336 		}
337 		close(map_fd);
338 	}
339 
340 	if (*values_map_fd != -1 && *ports_map_fd != -1) {
341 		err = 0;
342 		goto out;
343 	}
344 
345 	err = -ENOENT;
346 
347 err_close_map_fds:
348 	if (*values_map_fd != -1)
349 		close(*values_map_fd);
350 	if (*ports_map_fd != -1)
351 		close(*ports_map_fd);
352 	*values_map_fd = -1;
353 	*ports_map_fd = -1;
354 
355 out:
356 	close(prog_fd);
357 	return err;
358 }
359 
360 int main(int argc, char *argv[])
361 {
362 	int values_map_fd, ports_map_fd;
363 	__u64 tcpipopts;
364 	bool firstiter;
365 	__u64 prevcnt;
366 	__u32 prog_id;
367 	char *ports;
368 	bool single;
369 	int err = 0;
370 	bool tc;
371 
372 	parse_options(argc, argv, &ifindex, &prog_id, &tcpipopts, &ports,
373 		      &single, &tc);
374 
375 	if (prog_id == 0) {
376 		if (!tc) {
377 			err = bpf_xdp_query_id(ifindex, 0, &prog_id);
378 			if (err < 0) {
379 				fprintf(stderr, "Error: bpf_get_link_xdp_id: %s\n",
380 					strerror(-err));
381 				goto out;
382 			}
383 		}
384 		if (prog_id == 0) {
385 			err = syncookie_attach(argv[0], ifindex, tc);
386 			if (err < 0)
387 				goto out;
388 			prog_id = attached_prog_id;
389 		}
390 	}
391 
392 	err = syncookie_open_bpf_maps(prog_id, &values_map_fd, &ports_map_fd);
393 	if (err < 0)
394 		goto out;
395 
396 	if (ports) {
397 		__u16 port_last = 0;
398 		__u32 port_idx = 0;
399 		char *p = ports;
400 
401 		fprintf(stderr, "Replacing allowed ports\n");
402 
403 		while (p && *p != '\0') {
404 			char *token = strsep(&p, ",");
405 			__u16 port;
406 
407 			port = parse_arg_ul(argv[0], token, UINT16_MAX);
408 			err = bpf_map_update_elem(ports_map_fd, &port_idx, &port, BPF_ANY);
409 			if (err != 0) {
410 				fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
411 				fprintf(stderr, "Failed to add port %u (index %u)\n",
412 					port, port_idx);
413 				goto out_close_maps;
414 			}
415 			fprintf(stderr, "Added port %u\n", port);
416 			port_idx++;
417 		}
418 		err = bpf_map_update_elem(ports_map_fd, &port_idx, &port_last, BPF_ANY);
419 		if (err != 0) {
420 			fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
421 			fprintf(stderr, "Failed to add the terminator value 0 (index %u)\n",
422 				port_idx);
423 			goto out_close_maps;
424 		}
425 	}
426 
427 	if (tcpipopts) {
428 		__u32 key = 0;
429 
430 		fprintf(stderr, "Replacing TCP/IP options\n");
431 
432 		err = bpf_map_update_elem(values_map_fd, &key, &tcpipopts, BPF_ANY);
433 		if (err != 0) {
434 			fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
435 			goto out_close_maps;
436 		}
437 	}
438 
439 	if ((ports || tcpipopts) && attached_prog_id == 0 && !single)
440 		goto out_close_maps;
441 
442 	prevcnt = 0;
443 	firstiter = true;
444 	while (true) {
445 		__u32 key = 1;
446 		__u64 value;
447 
448 		err = bpf_map_lookup_elem(values_map_fd, &key, &value);
449 		if (err != 0) {
450 			fprintf(stderr, "Error: bpf_map_lookup_elem: %s\n", strerror(-err));
451 			goto out_close_maps;
452 		}
453 		if (firstiter) {
454 			prevcnt = value;
455 			firstiter = false;
456 		}
457 		if (single) {
458 			printf("Total SYNACKs generated: %llu\n", value);
459 			break;
460 		}
461 		printf("SYNACKs generated: %llu (total %llu)\n", value - prevcnt, value);
462 		prevcnt = value;
463 		sleep(1);
464 	}
465 
466 out_close_maps:
467 	close(values_map_fd);
468 	close(ports_map_fd);
469 out:
470 	return err == 0 ? 0 : 1;
471 }
472