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1// SPDX-License-Identifier: GPL-2.0
2
3#define _GNU_SOURCE
4
5#include <arpa/inet.h>
6#include <errno.h>
7#include <error.h>
8#include <linux/in.h>
9#include <netinet/ip.h>
10#include <netinet/ip6.h>
11#include <netinet/udp.h>
12#include <stdbool.h>
13#include <stdio.h>
14#include <stdlib.h>
15#include <string.h>
16#include <time.h>
17#include <unistd.h>
18
19static bool cfg_do_ipv4;
20static bool cfg_do_ipv6;
21static bool cfg_verbose;
22static bool cfg_overlap;
23static bool cfg_permissive;
24static unsigned short cfg_port = 9000;
25
26const struct in_addr addr4 = { .s_addr = __constant_htonl(INADDR_LOOPBACK + 2) };
27const struct in6_addr addr6 = IN6ADDR_LOOPBACK_INIT;
28
29#define IP4_HLEN (sizeof(struct iphdr))
30#define IP6_HLEN (sizeof(struct ip6_hdr))
31#define UDP_HLEN (sizeof(struct udphdr))
32
33/* IPv6 fragment header lenth. */
34#define FRAG_HLEN 8
35
36static int payload_len;
37static int max_frag_len;
38
39#define MSG_LEN_MAX 10000 /* Max UDP payload length. */
40
41#define IP4_MF (1u << 13) /* IPv4 MF flag. */
42#define IP6_MF (1) /* IPv6 MF flag. */
43
44#define CSUM_MANGLED_0 (0xffff)
45
46static uint8_t udp_payload[MSG_LEN_MAX];
47static uint8_t ip_frame[IP_MAXPACKET];
48static uint32_t ip_id = 0xabcd;
49static int msg_counter;
50static int frag_counter;
51static unsigned int seed;
52
53/* Receive a UDP packet. Validate it matches udp_payload. */
54static void recv_validate_udp(int fd_udp)
55{
56 ssize_t ret;
57 static uint8_t recv_buff[MSG_LEN_MAX];
58
59 ret = recv(fd_udp, recv_buff, payload_len, 0);
60 msg_counter++;
61
62 if (cfg_overlap) {
63 if (ret == -1 && (errno == ETIMEDOUT || errno == EAGAIN))
64 return; /* OK */
65 if (!cfg_permissive) {
66 if (ret != -1)
67 error(1, 0, "recv: expected timeout; got %d",
68 (int)ret);
69 error(1, errno, "recv: expected timeout: %d", errno);
70 }
71 }
72
73 if (ret == -1)
74 error(1, errno, "recv: payload_len = %d max_frag_len = %d",
75 payload_len, max_frag_len);
76 if (ret != payload_len)
77 error(1, 0, "recv: wrong size: %d vs %d", (int)ret, payload_len);
78 if (memcmp(udp_payload, recv_buff, payload_len))
79 error(1, 0, "recv: wrong data");
80}
81
82static uint32_t raw_checksum(uint8_t *buf, int len, uint32_t sum)
83{
84 int i;
85
86 for (i = 0; i < (len & ~1U); i += 2) {
87 sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
88 if (sum > 0xffff)
89 sum -= 0xffff;
90 }
91
92 if (i < len) {
93 sum += buf[i] << 8;
94 if (sum > 0xffff)
95 sum -= 0xffff;
96 }
97
98 return sum;
99}
100
101static uint16_t udp_checksum(struct ip *iphdr, struct udphdr *udphdr)
102{
103 uint32_t sum = 0;
104 uint16_t res;
105
106 sum = raw_checksum((uint8_t *)&iphdr->ip_src, 2 * sizeof(iphdr->ip_src),
107 IPPROTO_UDP + (uint32_t)(UDP_HLEN + payload_len));
108 sum = raw_checksum((uint8_t *)udphdr, UDP_HLEN, sum);
109 sum = raw_checksum((uint8_t *)udp_payload, payload_len, sum);
110 res = 0xffff & ~sum;
111 if (res)
112 return htons(res);
113 else
114 return CSUM_MANGLED_0;
115}
116
117static uint16_t udp6_checksum(struct ip6_hdr *iphdr, struct udphdr *udphdr)
118{
119 uint32_t sum = 0;
120 uint16_t res;
121
122 sum = raw_checksum((uint8_t *)&iphdr->ip6_src, 2 * sizeof(iphdr->ip6_src),
123 IPPROTO_UDP);
124 sum = raw_checksum((uint8_t *)&udphdr->len, sizeof(udphdr->len), sum);
125 sum = raw_checksum((uint8_t *)udphdr, UDP_HLEN, sum);
126 sum = raw_checksum((uint8_t *)udp_payload, payload_len, sum);
127 res = 0xffff & ~sum;
128 if (res)
129 return htons(res);
130 else
131 return CSUM_MANGLED_0;
132}
133
134static void send_fragment(int fd_raw, struct sockaddr *addr, socklen_t alen,
135 int offset, bool ipv6)
136{
137 int frag_len;
138 int res;
139 int payload_offset = offset > 0 ? offset - UDP_HLEN : 0;
140 uint8_t *frag_start = ipv6 ? ip_frame + IP6_HLEN + FRAG_HLEN :
141 ip_frame + IP4_HLEN;
142
143 if (offset == 0) {
144 struct udphdr udphdr;
145 udphdr.source = htons(cfg_port + 1);
146 udphdr.dest = htons(cfg_port);
147 udphdr.len = htons(UDP_HLEN + payload_len);
148 udphdr.check = 0;
149 if (ipv6)
150 udphdr.check = udp6_checksum((struct ip6_hdr *)ip_frame, &udphdr);
151 else
152 udphdr.check = udp_checksum((struct ip *)ip_frame, &udphdr);
153 memcpy(frag_start, &udphdr, UDP_HLEN);
154 }
155
156 if (ipv6) {
157 struct ip6_hdr *ip6hdr = (struct ip6_hdr *)ip_frame;
158 struct ip6_frag *fraghdr = (struct ip6_frag *)(ip_frame + IP6_HLEN);
159 if (payload_len - payload_offset <= max_frag_len && offset > 0) {
160 /* This is the last fragment. */
161 frag_len = FRAG_HLEN + payload_len - payload_offset;
162 fraghdr->ip6f_offlg = htons(offset);
163 } else {
164 frag_len = FRAG_HLEN + max_frag_len;
165 fraghdr->ip6f_offlg = htons(offset | IP6_MF);
166 }
167 ip6hdr->ip6_plen = htons(frag_len);
168 if (offset == 0)
169 memcpy(frag_start + UDP_HLEN, udp_payload,
170 frag_len - FRAG_HLEN - UDP_HLEN);
171 else
172 memcpy(frag_start, udp_payload + payload_offset,
173 frag_len - FRAG_HLEN);
174 frag_len += IP6_HLEN;
175 } else {
176 struct ip *iphdr = (struct ip *)ip_frame;
177 if (payload_len - payload_offset <= max_frag_len && offset > 0) {
178 /* This is the last fragment. */
179 frag_len = IP4_HLEN + payload_len - payload_offset;
180 iphdr->ip_off = htons(offset / 8);
181 } else {
182 frag_len = IP4_HLEN + max_frag_len;
183 iphdr->ip_off = htons(offset / 8 | IP4_MF);
184 }
185 iphdr->ip_len = htons(frag_len);
186 if (offset == 0)
187 memcpy(frag_start + UDP_HLEN, udp_payload,
188 frag_len - IP4_HLEN - UDP_HLEN);
189 else
190 memcpy(frag_start, udp_payload + payload_offset,
191 frag_len - IP4_HLEN);
192 }
193
194 res = sendto(fd_raw, ip_frame, frag_len, 0, addr, alen);
195 if (res < 0 && errno != EPERM)
196 error(1, errno, "send_fragment");
197 if (res >= 0 && res != frag_len)
198 error(1, 0, "send_fragment: %d vs %d", res, frag_len);
199
200 frag_counter++;
201}
202
203static void send_udp_frags(int fd_raw, struct sockaddr *addr,
204 socklen_t alen, bool ipv6)
205{
206 struct ip *iphdr = (struct ip *)ip_frame;
207 struct ip6_hdr *ip6hdr = (struct ip6_hdr *)ip_frame;
208 int res;
209 int offset;
210 int frag_len;
211
212 /* Send the UDP datagram using raw IP fragments: the 0th fragment
213 * has the UDP header; other fragments are pieces of udp_payload
214 * split in chunks of frag_len size.
215 *
216 * Odd fragments (1st, 3rd, 5th, etc.) are sent out first, then
217 * even fragments (0th, 2nd, etc.) are sent out.
218 */
219 if (ipv6) {
220 struct ip6_frag *fraghdr = (struct ip6_frag *)(ip_frame + IP6_HLEN);
221 ((struct sockaddr_in6 *)addr)->sin6_port = 0;
222 memset(ip6hdr, 0, sizeof(*ip6hdr));
223 ip6hdr->ip6_flow = htonl(6<<28); /* Version. */
224 ip6hdr->ip6_nxt = IPPROTO_FRAGMENT;
225 ip6hdr->ip6_hops = 255;
226 ip6hdr->ip6_src = addr6;
227 ip6hdr->ip6_dst = addr6;
228 fraghdr->ip6f_nxt = IPPROTO_UDP;
229 fraghdr->ip6f_reserved = 0;
230 fraghdr->ip6f_ident = htonl(ip_id++);
231 } else {
232 memset(iphdr, 0, sizeof(*iphdr));
233 iphdr->ip_hl = 5;
234 iphdr->ip_v = 4;
235 iphdr->ip_tos = 0;
236 iphdr->ip_id = htons(ip_id++);
237 iphdr->ip_ttl = 0x40;
238 iphdr->ip_p = IPPROTO_UDP;
239 iphdr->ip_src.s_addr = htonl(INADDR_LOOPBACK);
240 iphdr->ip_dst = addr4;
241 iphdr->ip_sum = 0;
242 }
243
244 /* Occasionally test in-order fragments. */
245 if (!cfg_overlap && (rand() % 100 < 15)) {
246 offset = 0;
247 while (offset < (UDP_HLEN + payload_len)) {
248 send_fragment(fd_raw, addr, alen, offset, ipv6);
249 offset += max_frag_len;
250 }
251 return;
252 }
253
254 /* Occasionally test IPv4 "runs" (see net/ipv4/ip_fragment.c) */
255 if (!cfg_overlap && (rand() % 100 < 20) &&
256 (payload_len > 9 * max_frag_len)) {
257 offset = 6 * max_frag_len;
258 while (offset < (UDP_HLEN + payload_len)) {
259 send_fragment(fd_raw, addr, alen, offset, ipv6);
260 offset += max_frag_len;
261 }
262 offset = 3 * max_frag_len;
263 while (offset < 6 * max_frag_len) {
264 send_fragment(fd_raw, addr, alen, offset, ipv6);
265 offset += max_frag_len;
266 }
267 offset = 0;
268 while (offset < 3 * max_frag_len) {
269 send_fragment(fd_raw, addr, alen, offset, ipv6);
270 offset += max_frag_len;
271 }
272 return;
273 }
274
275 /* Odd fragments. */
276 offset = max_frag_len;
277 while (offset < (UDP_HLEN + payload_len)) {
278 send_fragment(fd_raw, addr, alen, offset, ipv6);
279 /* IPv4 ignores duplicates, so randomly send a duplicate. */
280 if (rand() % 100 == 1)
281 send_fragment(fd_raw, addr, alen, offset, ipv6);
282 offset += 2 * max_frag_len;
283 }
284
285 if (cfg_overlap) {
286 /* Send an extra random fragment.
287 *
288 * Duplicates and some fragments completely inside
289 * previously sent fragments are dropped/ignored. So
290 * random offset and frag_len can result in a dropped
291 * fragment instead of a dropped queue/packet. Thus we
292 * hard-code offset and frag_len.
293 */
294 if (max_frag_len * 4 < payload_len || max_frag_len < 16) {
295 /* not enough payload for random offset and frag_len. */
296 offset = 8;
297 frag_len = UDP_HLEN + max_frag_len;
298 } else {
299 offset = rand() % (payload_len / 2);
300 frag_len = 2 * max_frag_len + 1 + rand() % 256;
301 }
302 if (ipv6) {
303 struct ip6_frag *fraghdr = (struct ip6_frag *)(ip_frame + IP6_HLEN);
304 /* sendto() returns EINVAL if offset + frag_len is too small. */
305 /* In IPv6 if !!(frag_len % 8), the fragment is dropped. */
306 frag_len &= ~0x7;
307 fraghdr->ip6f_offlg = htons(offset / 8 | IP6_MF);
308 ip6hdr->ip6_plen = htons(frag_len);
309 frag_len += IP6_HLEN;
310 } else {
311 frag_len += IP4_HLEN;
312 iphdr->ip_off = htons(offset / 8 | IP4_MF);
313 iphdr->ip_len = htons(frag_len);
314 }
315 res = sendto(fd_raw, ip_frame, frag_len, 0, addr, alen);
316 if (res < 0 && errno != EPERM)
317 error(1, errno, "sendto overlap: %d", frag_len);
318 if (res >= 0 && res != frag_len)
319 error(1, 0, "sendto overlap: %d vs %d", (int)res, frag_len);
320 frag_counter++;
321 }
322
323 /* Event fragments. */
324 offset = 0;
325 while (offset < (UDP_HLEN + payload_len)) {
326 send_fragment(fd_raw, addr, alen, offset, ipv6);
327 /* IPv4 ignores duplicates, so randomly send a duplicate. */
328 if (rand() % 100 == 1)
329 send_fragment(fd_raw, addr, alen, offset, ipv6);
330 offset += 2 * max_frag_len;
331 }
332}
333
334static void run_test(struct sockaddr *addr, socklen_t alen, bool ipv6)
335{
336 int fd_tx_raw, fd_rx_udp;
337 /* Frag queue timeout is set to one second in the calling script;
338 * socket timeout should be just a bit longer to avoid tests interfering
339 * with each other.
340 */
341 struct timeval tv = { .tv_sec = 1, .tv_usec = 10 };
342 int idx;
343 int min_frag_len = 8;
344
345 /* Initialize the payload. */
346 for (idx = 0; idx < MSG_LEN_MAX; ++idx)
347 udp_payload[idx] = idx % 256;
348
349 /* Open sockets. */
350 fd_tx_raw = socket(addr->sa_family, SOCK_RAW, IPPROTO_RAW);
351 if (fd_tx_raw == -1)
352 error(1, errno, "socket tx_raw");
353
354 fd_rx_udp = socket(addr->sa_family, SOCK_DGRAM, 0);
355 if (fd_rx_udp == -1)
356 error(1, errno, "socket rx_udp");
357 if (bind(fd_rx_udp, addr, alen))
358 error(1, errno, "bind");
359 /* Fail fast. */
360 if (setsockopt(fd_rx_udp, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)))
361 error(1, errno, "setsockopt rcv timeout");
362
363 for (payload_len = min_frag_len; payload_len < MSG_LEN_MAX;
364 payload_len += (rand() % 4096)) {
365 if (cfg_verbose)
366 printf("payload_len: %d\n", payload_len);
367
368 if (cfg_overlap) {
369 /* With overlaps, one send/receive pair below takes
370 * at least one second (== timeout) to run, so there
371 * is not enough test time to run a nested loop:
372 * the full overlap test takes 20-30 seconds.
373 */
374 max_frag_len = min_frag_len +
375 rand() % (1500 - FRAG_HLEN - min_frag_len);
376 send_udp_frags(fd_tx_raw, addr, alen, ipv6);
377 recv_validate_udp(fd_rx_udp);
378 } else {
379 /* Without overlaps, each packet reassembly (== one
380 * send/receive pair below) takes very little time to
381 * run, so we can easily afford more thourough testing
382 * with a nested loop: the full non-overlap test takes
383 * less than one second).
384 */
385 max_frag_len = min_frag_len;
386 do {
387 send_udp_frags(fd_tx_raw, addr, alen, ipv6);
388 recv_validate_udp(fd_rx_udp);
389 max_frag_len += 8 * (rand() % 8);
390 } while (max_frag_len < (1500 - FRAG_HLEN) &&
391 max_frag_len <= payload_len);
392 }
393 }
394
395 /* Cleanup. */
396 if (close(fd_tx_raw))
397 error(1, errno, "close tx_raw");
398 if (close(fd_rx_udp))
399 error(1, errno, "close rx_udp");
400
401 if (cfg_verbose)
402 printf("processed %d messages, %d fragments\n",
403 msg_counter, frag_counter);
404
405 fprintf(stderr, "PASS\n");
406}
407
408
409static void run_test_v4(void)
410{
411 struct sockaddr_in addr = {0};
412
413 addr.sin_family = AF_INET;
414 addr.sin_port = htons(cfg_port);
415 addr.sin_addr = addr4;
416
417 run_test((void *)&addr, sizeof(addr), false /* !ipv6 */);
418}
419
420static void run_test_v6(void)
421{
422 struct sockaddr_in6 addr = {0};
423
424 addr.sin6_family = AF_INET6;
425 addr.sin6_port = htons(cfg_port);
426 addr.sin6_addr = addr6;
427
428 run_test((void *)&addr, sizeof(addr), true /* ipv6 */);
429}
430
431static void parse_opts(int argc, char **argv)
432{
433 int c;
434
435 while ((c = getopt(argc, argv, "46opv")) != -1) {
436 switch (c) {
437 case '4':
438 cfg_do_ipv4 = true;
439 break;
440 case '6':
441 cfg_do_ipv6 = true;
442 break;
443 case 'o':
444 cfg_overlap = true;
445 break;
446 case 'p':
447 cfg_permissive = true;
448 break;
449 case 'v':
450 cfg_verbose = true;
451 break;
452 default:
453 error(1, 0, "%s: parse error", argv[0]);
454 }
455 }
456}
457
458int main(int argc, char **argv)
459{
460 parse_opts(argc, argv);
461 seed = time(NULL);
462 srand(seed);
463 /* Print the seed to track/reproduce potential failures. */
464 printf("seed = %d\n", seed);
465
466 if (cfg_do_ipv4)
467 run_test_v4();
468 if (cfg_do_ipv6)
469 run_test_v6();
470
471 return 0;
472}