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-rw-r--r--src/usr.bin/nc/netcat.c843
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diff --git a/src/usr.bin/nc/netcat.c b/src/usr.bin/nc/netcat.c
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1/* $OpenBSD: netcat.c,v 1.88 2006/06/02 03:46:38 ray Exp $ */
2/*
3 * Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 * derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/*
30 * Re-written nc(1) for OpenBSD. Original implementation by
31 * *Hobbit* <hobbit@avian.org>.
32 */
33
34#include <sys/types.h>
35#include <sys/socket.h>
36#include <sys/time.h>
37#include <sys/un.h>
38
39#include <netinet/in.h>
40#include <netinet/in_systm.h>
41#include <netinet/tcp.h>
42#include <netinet/ip.h>
43#include <arpa/telnet.h>
44
45#include <err.h>
46#include <errno.h>
47#include <netdb.h>
48#include <poll.h>
49#include <stdarg.h>
50#include <stdio.h>
51#include <stdlib.h>
52#include <string.h>
53#include <unistd.h>
54#include <fcntl.h>
55#include <limits.h>
56#include "atomicio.h"
57
58#ifndef SUN_LEN
59#define SUN_LEN(su) \
60 (sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path))
61#endif
62
63#define PORT_MAX 65535
64#define PORT_MAX_LEN 6
65
66/* Command Line Options */
67int dflag; /* detached, no stdin */
68unsigned int iflag; /* Interval Flag */
69int jflag; /* use jumbo frames if we can */
70int kflag; /* More than one connect */
71int lflag; /* Bind to local port */
72int nflag; /* Don't do name look up */
73char *Pflag; /* Proxy username */
74char *pflag; /* Localport flag */
75int rflag; /* Random ports flag */
76char *sflag; /* Source Address */
77int tflag; /* Telnet Emulation */
78int uflag; /* UDP - Default to TCP */
79int vflag; /* Verbosity */
80int xflag; /* Socks proxy */
81int zflag; /* Port Scan Flag */
82int Dflag; /* sodebug */
83int Sflag; /* TCP MD5 signature option */
84int Tflag = -1; /* IP Type of Service */
85
86int timeout = -1;
87int family = AF_UNSPEC;
88char *portlist[PORT_MAX+1];
89
90void atelnet(int, unsigned char *, unsigned int);
91void build_ports(char *);
92void help(void);
93int local_listen(char *, char *, struct addrinfo);
94void readwrite(int);
95int remote_connect(const char *, const char *, struct addrinfo);
96int socks_connect(const char *, const char *, struct addrinfo,
97 const char *, const char *, struct addrinfo, int, const char *);
98int udptest(int);
99int unix_connect(char *);
100int unix_listen(char *);
101void set_common_sockopts(int);
102int parse_iptos(char *);
103void usage(int);
104
105int
106main(int argc, char *argv[])
107{
108 int ch, s, ret, socksv;
109 char *host, *uport;
110 struct addrinfo hints;
111 struct servent *sv;
112 socklen_t len;
113 struct sockaddr_storage cliaddr;
114 char *proxy;
115 const char *errstr, *proxyhost = "", *proxyport = NULL;
116 struct addrinfo proxyhints;
117
118 ret = 1;
119 s = 0;
120 socksv = 5;
121 host = NULL;
122 uport = NULL;
123 sv = NULL;
124
125 while ((ch = getopt(argc, argv,
126 "46Ddhi:jklnP:p:rSs:tT:Uuvw:X:x:z")) != -1) {
127 switch (ch) {
128 case '4':
129 family = AF_INET;
130 break;
131 case '6':
132 family = AF_INET6;
133 break;
134 case 'U':
135 family = AF_UNIX;
136 break;
137 case 'X':
138 if (strcasecmp(optarg, "connect") == 0)
139 socksv = -1; /* HTTP proxy CONNECT */
140 else if (strcmp(optarg, "4") == 0)
141 socksv = 4; /* SOCKS v.4 */
142 else if (strcmp(optarg, "5") == 0)
143 socksv = 5; /* SOCKS v.5 */
144 else
145 errx(1, "unsupported proxy protocol");
146 break;
147 case 'd':
148 dflag = 1;
149 break;
150 case 'h':
151 help();
152 break;
153 case 'i':
154 iflag = strtonum(optarg, 0, UINT_MAX, &errstr);
155 if (errstr)
156 errx(1, "interval %s: %s", errstr, optarg);
157 break;
158 case 'j':
159 jflag = 1;
160 break;
161 case 'k':
162 kflag = 1;
163 break;
164 case 'l':
165 lflag = 1;
166 break;
167 case 'n':
168 nflag = 1;
169 break;
170 case 'P':
171 Pflag = optarg;
172 break;
173 case 'p':
174 pflag = optarg;
175 break;
176 case 'r':
177 rflag = 1;
178 break;
179 case 's':
180 sflag = optarg;
181 break;
182 case 't':
183 tflag = 1;
184 break;
185 case 'u':
186 uflag = 1;
187 break;
188 case 'v':
189 vflag = 1;
190 break;
191 case 'w':
192 timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
193 if (errstr)
194 errx(1, "timeout %s: %s", errstr, optarg);
195 timeout *= 1000;
196 break;
197 case 'x':
198 xflag = 1;
199 if ((proxy = strdup(optarg)) == NULL)
200 err(1, NULL);
201 break;
202 case 'z':
203 zflag = 1;
204 break;
205 case 'D':
206 Dflag = 1;
207 break;
208 case 'S':
209 Sflag = 1;
210 break;
211 case 'T':
212 Tflag = parse_iptos(optarg);
213 break;
214 default:
215 usage(1);
216 }
217 }
218 argc -= optind;
219 argv += optind;
220
221 /* Cruft to make sure options are clean, and used properly. */
222 if (argv[0] && !argv[1] && family == AF_UNIX) {
223 if (uflag)
224 errx(1, "cannot use -u and -U");
225 host = argv[0];
226 uport = NULL;
227 } else if (argv[0] && !argv[1]) {
228 if (!lflag)
229 usage(1);
230 uport = argv[0];
231 host = NULL;
232 } else if (argv[0] && argv[1]) {
233 host = argv[0];
234 uport = argv[1];
235 } else
236 usage(1);
237
238 if (lflag && sflag)
239 errx(1, "cannot use -s and -l");
240 if (lflag && pflag)
241 errx(1, "cannot use -p and -l");
242 if (lflag && zflag)
243 errx(1, "cannot use -z and -l");
244 if (!lflag && kflag)
245 errx(1, "must use -l with -k");
246
247 /* Initialize addrinfo structure. */
248 if (family != AF_UNIX) {
249 memset(&hints, 0, sizeof(struct addrinfo));
250 hints.ai_family = family;
251 hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
252 hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
253 if (nflag)
254 hints.ai_flags |= AI_NUMERICHOST;
255 }
256
257 if (xflag) {
258 if (uflag)
259 errx(1, "no proxy support for UDP mode");
260
261 if (lflag)
262 errx(1, "no proxy support for listen");
263
264 if (family == AF_UNIX)
265 errx(1, "no proxy support for unix sockets");
266
267 /* XXX IPv6 transport to proxy would probably work */
268 if (family == AF_INET6)
269 errx(1, "no proxy support for IPv6");
270
271 if (sflag)
272 errx(1, "no proxy support for local source address");
273
274 proxyhost = strsep(&proxy, ":");
275 proxyport = proxy;
276
277 memset(&proxyhints, 0, sizeof(struct addrinfo));
278 proxyhints.ai_family = family;
279 proxyhints.ai_socktype = SOCK_STREAM;
280 proxyhints.ai_protocol = IPPROTO_TCP;
281 if (nflag)
282 proxyhints.ai_flags |= AI_NUMERICHOST;
283 }
284
285 if (lflag) {
286 int connfd;
287 ret = 0;
288
289 if (family == AF_UNIX)
290 s = unix_listen(host);
291
292 /* Allow only one connection at a time, but stay alive. */
293 for (;;) {
294 if (family != AF_UNIX)
295 s = local_listen(host, uport, hints);
296 if (s < 0)
297 err(1, NULL);
298 /*
299 * For UDP, we will use recvfrom() initially
300 * to wait for a caller, then use the regular
301 * functions to talk to the caller.
302 */
303 if (uflag) {
304 int rv, plen;
305 char buf[8192];
306 struct sockaddr_storage z;
307
308 len = sizeof(z);
309 plen = jflag ? 8192 : 1024;
310 rv = recvfrom(s, buf, plen, MSG_PEEK,
311 (struct sockaddr *)&z, &len);
312 if (rv < 0)
313 err(1, "recvfrom");
314
315 rv = connect(s, (struct sockaddr *)&z, len);
316 if (rv < 0)
317 err(1, "connect");
318
319 connfd = s;
320 } else {
321 len = sizeof(cliaddr);
322 connfd = accept(s, (struct sockaddr *)&cliaddr,
323 &len);
324 }
325
326 readwrite(connfd);
327 close(connfd);
328 if (family != AF_UNIX)
329 close(s);
330
331 if (!kflag)
332 break;
333 }
334 } else if (family == AF_UNIX) {
335 ret = 0;
336
337 if ((s = unix_connect(host)) > 0 && !zflag) {
338 readwrite(s);
339 close(s);
340 } else
341 ret = 1;
342
343 exit(ret);
344
345 } else {
346 int i = 0;
347
348 /* Construct the portlist[] array. */
349 build_ports(uport);
350
351 /* Cycle through portlist, connecting to each port. */
352 for (i = 0; portlist[i] != NULL; i++) {
353 if (s)
354 close(s);
355
356 if (xflag)
357 s = socks_connect(host, portlist[i], hints,
358 proxyhost, proxyport, proxyhints, socksv,
359 Pflag);
360 else
361 s = remote_connect(host, portlist[i], hints);
362
363 if (s < 0)
364 continue;
365
366 ret = 0;
367 if (vflag || zflag) {
368 /* For UDP, make sure we are connected. */
369 if (uflag) {
370 if (udptest(s) == -1) {
371 ret = 1;
372 continue;
373 }
374 }
375
376 /* Don't look up port if -n. */
377 if (nflag)
378 sv = NULL;
379 else {
380 sv = getservbyport(
381 ntohs(atoi(portlist[i])),
382 uflag ? "udp" : "tcp");
383 }
384
385 printf("Connection to %s %s port [%s/%s] succeeded!\n",
386 host, portlist[i], uflag ? "udp" : "tcp",
387 sv ? sv->s_name : "*");
388 }
389 if (!zflag)
390 readwrite(s);
391 }
392 }
393
394 if (s)
395 close(s);
396
397 exit(ret);
398}
399
400/*
401 * unix_connect()
402 * Returns a socket connected to a local unix socket. Returns -1 on failure.
403 */
404int
405unix_connect(char *path)
406{
407 struct sockaddr_un sun;
408 int s;
409
410 if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
411 return (-1);
412 (void)fcntl(s, F_SETFD, 1);
413
414 memset(&sun, 0, sizeof(struct sockaddr_un));
415 sun.sun_family = AF_UNIX;
416
417 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
418 sizeof(sun.sun_path)) {
419 close(s);
420 errno = ENAMETOOLONG;
421 return (-1);
422 }
423 if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
424 close(s);
425 return (-1);
426 }
427 return (s);
428
429}
430
431/*
432 * unix_listen()
433 * Create a unix domain socket, and listen on it.
434 */
435int
436unix_listen(char *path)
437{
438 struct sockaddr_un sun;
439 int s;
440
441 /* Create unix domain socket. */
442 if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
443 return (-1);
444
445 memset(&sun, 0, sizeof(struct sockaddr_un));
446 sun.sun_family = AF_UNIX;
447
448 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
449 sizeof(sun.sun_path)) {
450 close(s);
451 errno = ENAMETOOLONG;
452 return (-1);
453 }
454
455 if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
456 close(s);
457 return (-1);
458 }
459
460 if (listen(s, 5) < 0) {
461 close(s);
462 return (-1);
463 }
464 return (s);
465}
466
467/*
468 * remote_connect()
469 * Returns a socket connected to a remote host. Properly binds to a local
470 * port or source address if needed. Returns -1 on failure.
471 */
472int
473remote_connect(const char *host, const char *port, struct addrinfo hints)
474{
475 struct addrinfo *res, *res0;
476 int s, error;
477
478 if ((error = getaddrinfo(host, port, &hints, &res)))
479 errx(1, "getaddrinfo: %s", gai_strerror(error));
480
481 res0 = res;
482 do {
483 if ((s = socket(res0->ai_family, res0->ai_socktype,
484 res0->ai_protocol)) < 0)
485 continue;
486
487 /* Bind to a local port or source address if specified. */
488 if (sflag || pflag) {
489 struct addrinfo ahints, *ares;
490
491 memset(&ahints, 0, sizeof(struct addrinfo));
492 ahints.ai_family = res0->ai_family;
493 ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
494 ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
495 ahints.ai_flags = AI_PASSIVE;
496 if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
497 errx(1, "getaddrinfo: %s", gai_strerror(error));
498
499 if (bind(s, (struct sockaddr *)ares->ai_addr,
500 ares->ai_addrlen) < 0)
501 errx(1, "bind failed: %s", strerror(errno));
502 freeaddrinfo(ares);
503 }
504
505 set_common_sockopts(s);
506
507 if (connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
508 break;
509 else if (vflag)
510 warn("connect to %s port %s (%s) failed", host, port,
511 uflag ? "udp" : "tcp");
512
513 close(s);
514 s = -1;
515 } while ((res0 = res0->ai_next) != NULL);
516
517 freeaddrinfo(res);
518
519 return (s);
520}
521
522/*
523 * local_listen()
524 * Returns a socket listening on a local port, binds to specified source
525 * address. Returns -1 on failure.
526 */
527int
528local_listen(char *host, char *port, struct addrinfo hints)
529{
530 struct addrinfo *res, *res0;
531 int s, ret, x = 1;
532 int error;
533
534 /* Allow nodename to be null. */
535 hints.ai_flags |= AI_PASSIVE;
536
537 /*
538 * In the case of binding to a wildcard address
539 * default to binding to an ipv4 address.
540 */
541 if (host == NULL && hints.ai_family == AF_UNSPEC)
542 hints.ai_family = AF_INET;
543
544 if ((error = getaddrinfo(host, port, &hints, &res)))
545 errx(1, "getaddrinfo: %s", gai_strerror(error));
546
547 res0 = res;
548 do {
549 if ((s = socket(res0->ai_family, res0->ai_socktype,
550 res0->ai_protocol)) < 0)
551 continue;
552
553 ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
554 if (ret == -1)
555 err(1, NULL);
556
557 set_common_sockopts(s);
558
559 if (bind(s, (struct sockaddr *)res0->ai_addr,
560 res0->ai_addrlen) == 0)
561 break;
562
563 close(s);
564 s = -1;
565 } while ((res0 = res0->ai_next) != NULL);
566
567 if (!uflag && s != -1) {
568 if (listen(s, 1) < 0)
569 err(1, "listen");
570 }
571
572 freeaddrinfo(res);
573
574 return (s);
575}
576
577/*
578 * readwrite()
579 * Loop that polls on the network file descriptor and stdin.
580 */
581void
582readwrite(int nfd)
583{
584 struct pollfd pfd[2];
585 unsigned char buf[8192];
586 int n, wfd = fileno(stdin);
587 int lfd = fileno(stdout);
588 int plen;
589
590 plen = jflag ? 8192 : 1024;
591
592 /* Setup Network FD */
593 pfd[0].fd = nfd;
594 pfd[0].events = POLLIN;
595
596 /* Set up STDIN FD. */
597 pfd[1].fd = wfd;
598 pfd[1].events = POLLIN;
599
600 while (pfd[0].fd != -1) {
601 if (iflag)
602 sleep(iflag);
603
604 if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
605 close(nfd);
606 err(1, "Polling Error");
607 }
608
609 if (n == 0)
610 return;
611
612 if (pfd[0].revents & POLLIN) {
613 if ((n = read(nfd, buf, plen)) < 0)
614 return;
615 else if (n == 0) {
616 shutdown(nfd, SHUT_RD);
617 pfd[0].fd = -1;
618 pfd[0].events = 0;
619 } else {
620 if (tflag)
621 atelnet(nfd, buf, n);
622 if (atomicio(vwrite, lfd, buf, n) != n)
623 return;
624 }
625 }
626
627 if (!dflag && pfd[1].revents & POLLIN) {
628 if ((n = read(wfd, buf, plen)) < 0)
629 return;
630 else if (n == 0) {
631 shutdown(nfd, SHUT_WR);
632 pfd[1].fd = -1;
633 pfd[1].events = 0;
634 } else {
635 if (atomicio(vwrite, nfd, buf, n) != n)
636 return;
637 }
638 }
639 }
640}
641
642/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
643void
644atelnet(int nfd, unsigned char *buf, unsigned int size)
645{
646 unsigned char *p, *end;
647 unsigned char obuf[4];
648
649 end = buf + size;
650 obuf[0] = '\0';
651
652 for (p = buf; p < end; p++) {
653 if (*p != IAC)
654 break;
655
656 obuf[0] = IAC;
657 p++;
658 if ((*p == WILL) || (*p == WONT))
659 obuf[1] = DONT;
660 if ((*p == DO) || (*p == DONT))
661 obuf[1] = WONT;
662 if (obuf) {
663 p++;
664 obuf[2] = *p;
665 obuf[3] = '\0';
666 if (atomicio(vwrite, nfd, obuf, 3) != 3)
667 warn("Write Error!");
668 obuf[0] = '\0';
669 }
670 }
671}
672
673/*
674 * build_ports()
675 * Build an array or ports in portlist[], listing each port
676 * that we should try to connect to.
677 */
678void
679build_ports(char *p)
680{
681 const char *errstr;
682 char *n;
683 int hi, lo, cp;
684 int x = 0;
685
686 if ((n = strchr(p, '-')) != NULL) {
687 if (lflag)
688 errx(1, "Cannot use -l with multiple ports!");
689
690 *n = '\0';
691 n++;
692
693 /* Make sure the ports are in order: lowest->highest. */
694 hi = strtonum(n, 1, PORT_MAX, &errstr);
695 if (errstr)
696 errx(1, "port number %s: %s", errstr, n);
697 lo = strtonum(p, 1, PORT_MAX, &errstr);
698 if (errstr)
699 errx(1, "port number %s: %s", errstr, p);
700
701 if (lo > hi) {
702 cp = hi;
703 hi = lo;
704 lo = cp;
705 }
706
707 /* Load ports sequentially. */
708 for (cp = lo; cp <= hi; cp++) {
709 portlist[x] = calloc(1, PORT_MAX_LEN);
710 if (portlist[x] == NULL)
711 err(1, NULL);
712 snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
713 x++;
714 }
715
716 /* Randomly swap ports. */
717 if (rflag) {
718 int y;
719 char *c;
720
721 for (x = 0; x <= (hi - lo); x++) {
722 y = (arc4random() & 0xFFFF) % (hi - lo);
723 c = portlist[x];
724 portlist[x] = portlist[y];
725 portlist[y] = c;
726 }
727 }
728 } else {
729 hi = strtonum(p, 1, PORT_MAX, &errstr);
730 if (errstr)
731 errx(1, "port number %s: %s", errstr, p);
732 portlist[0] = calloc(1, PORT_MAX_LEN);
733 if (portlist[0] == NULL)
734 err(1, NULL);
735 portlist[0] = p;
736 }
737}
738
739/*
740 * udptest()
741 * Do a few writes to see if the UDP port is there.
742 * XXX - Better way of doing this? Doesn't work for IPv6.
743 * Also fails after around 100 ports checked.
744 */
745int
746udptest(int s)
747{
748 int i, ret;
749
750 for (i = 0; i <= 3; i++) {
751 if (write(s, "X", 1) == 1)
752 ret = 1;
753 else
754 ret = -1;
755 }
756 return (ret);
757}
758
759void
760set_common_sockopts(int s)
761{
762 int x = 1;
763
764 if (Sflag) {
765 if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
766 &x, sizeof(x)) == -1)
767 err(1, NULL);
768 }
769 if (Dflag) {
770 if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
771 &x, sizeof(x)) == -1)
772 err(1, NULL);
773 }
774 if (jflag) {
775 if (setsockopt(s, SOL_SOCKET, SO_JUMBO,
776 &x, sizeof(x)) == -1)
777 err(1, NULL);
778 }
779 if (Tflag != -1) {
780 if (setsockopt(s, IPPROTO_IP, IP_TOS,
781 &Tflag, sizeof(Tflag)) == -1)
782 err(1, "set IP ToS");
783 }
784}
785
786int
787parse_iptos(char *s)
788{
789 int tos = -1;
790
791 if (strcmp(s, "lowdelay") == 0)
792 return (IPTOS_LOWDELAY);
793 if (strcmp(s, "throughput") == 0)
794 return (IPTOS_THROUGHPUT);
795 if (strcmp(s, "reliability") == 0)
796 return (IPTOS_RELIABILITY);
797
798 if (sscanf(s, "0x%x", &tos) != 1 || tos < 0 || tos > 0xff)
799 errx(1, "invalid IP Type of Service");
800 return (tos);
801}
802
803void
804help(void)
805{
806 usage(0);
807 fprintf(stderr, "\tCommand Summary:\n\
808 \t-4 Use IPv4\n\
809 \t-6 Use IPv6\n\
810 \t-D Enable the debug socket option\n\
811 \t-d Detach from stdin\n\
812 \t-h This help text\n\
813 \t-i secs\t Delay interval for lines sent, ports scanned\n\
814 \t-k Keep inbound sockets open for multiple connects\n\
815 \t-l Listen mode, for inbound connects\n\
816 \t-n Suppress name/port resolutions\n\
817 \t-P proxyuser\tUsername for proxy authentication\n\
818 \t-p port\t Specify local port for remote connects\n\
819 \t-r Randomize remote ports\n\
820 \t-S Enable the TCP MD5 signature option\n\
821 \t-s addr\t Local source address\n\
822 \t-T ToS\t Set IP Type of Service\n\
823 \t-t Answer TELNET negotiation\n\
824 \t-U Use UNIX domain socket\n\
825 \t-u UDP mode\n\
826 \t-v Verbose\n\
827 \t-w secs\t Timeout for connects and final net reads\n\
828 \t-X proto Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
829 \t-x addr[:port]\tSpecify proxy address and port\n\
830 \t-z Zero-I/O mode [used for scanning]\n\
831 Port numbers can be individual or ranges: lo-hi [inclusive]\n");
832 exit(1);
833}
834
835void
836usage(int ret)
837{
838 fprintf(stderr, "usage: nc [-46DdhklnrStUuvz] [-i interval] [-p source_port]\n");
839 fprintf(stderr, "\t [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_version]\n");
840 fprintf(stderr, "\t [-x proxy_address[:port]] [hostname] [port[s]]\n");
841 if (ret)
842 exit(1);
843}
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-05-08 09:03:54 +0000