netcat.c revision 205561 
1/* $OpenBSD: netcat.c,v 1.95 2010/02/27 00:58:56 nicm 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 * $FreeBSD: head/contrib/netcat/netcat.c 205561 2010-03-23 23:00:35Z delphij $
29 */
30
31/*
32 * Re-written nc(1) for OpenBSD. Original implementation by
33 * *Hobbit* <hobbit@avian.org>.
34 */
35
36#include <sys/limits.h>
37#include <sys/types.h>
38#include <sys/socket.h>
39#include <sys/sysctl.h>
40#include <sys/time.h>
41#include <sys/un.h>
42
43#include <netinet/in.h>
44#include <netinet/in_systm.h>
45#ifdef IPSEC
46#include <netipsec/ipsec.h>
47#endif
48#include <netinet/tcp.h>
49#include <netinet/ip.h>
50#include <arpa/telnet.h>
51
52#include <err.h>
53#include <errno.h>
54#include <getopt.h>
55#include <netdb.h>
56#include <poll.h>
57#include <stdarg.h>
58#include <stdio.h>
59#include <stdlib.h>
60#include <string.h>
61#include <unistd.h>
62#include <fcntl.h>
63#include <limits.h>
64#include "atomicio.h"
65
66#ifndef SUN_LEN
67#define SUN_LEN(su) \
68	(sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path))
69#endif
70
71#define PORT_MAX	65535
72#define PORT_MAX_LEN	6
73
74/* Command Line Options */
75int	Eflag;					/* Use IPsec ESP */
76int	dflag;					/* detached, no stdin */
77unsigned int iflag;				/* Interval Flag */
78int	jflag;					/* use jumbo frames if we can */
79int	kflag;					/* More than one connect */
80int	lflag;					/* Bind to local port */
81int	nflag;					/* Don't do name look up */
82int	oflag;					/* Once only: stop on EOF */
83int	FreeBSD_Oflag;				/* Do not use TCP options */
84char   *Pflag;					/* Proxy username */
85char   *pflag;					/* Localport flag */
86int	rflag;					/* Random ports flag */
87char   *sflag;					/* Source Address */
88int	tflag;					/* Telnet Emulation */
89int	uflag;					/* UDP - Default to TCP */
90int	vflag;					/* Verbosity */
91int	xflag;					/* Socks proxy */
92int	zflag;					/* Port Scan Flag */
93int	Dflag;					/* sodebug */
94int	Iflag;					/* TCP receive buffer size */
95int	Oflag;					/* TCP send buffer size */
96int	Sflag;					/* TCP MD5 signature option */
97int	Tflag = -1;				/* IP Type of Service */
98u_int	rdomain;
99
100int timeout = -1;
101int family = AF_UNSPEC;
102char *portlist[PORT_MAX+1];
103
104void	atelnet(int, unsigned char *, unsigned int);
105void	build_ports(char *);
106void	help(void);
107int	local_listen(char *, char *, struct addrinfo);
108void	readwrite(int);
109int	remote_connect(const char *, const char *, struct addrinfo);
110int	socks_connect(const char *, const char *, struct addrinfo,
111	    const char *, const char *, struct addrinfo, int, const char *);
112int	udptest(int);
113int	unix_connect(char *);
114int	unix_listen(char *);
115void	set_common_sockopts(int);
116int	parse_iptos(char *);
117void	usage(int);
118
119#ifdef IPSEC
120void	add_ipsec_policy(int, char *);
121
122char	*ipsec_policy[2];
123#endif
124
125int
126main(int argc, char *argv[])
127{
128	int ch, s, ret, socksv, ipsec_count;
129	int numfibs;
130	size_t intsize = sizeof(int);
131	char *host, *uport;
132	struct addrinfo hints;
133	struct servent *sv;
134	socklen_t len;
135	struct sockaddr_storage cliaddr;
136	char *proxy;
137	const char *errstr, *proxyhost = "", *proxyport = NULL;
138	struct addrinfo proxyhints;
139	struct option longopts[] = {
140		{ "no-tcpopt",	no_argument,	&FreeBSD_Oflag,	1 },
141		{ NULL,		0,		NULL,		0 }
142	};
143
144	rdomain = 0;
145	ret = 1;
146	ipsec_count = 0;
147	s = 0;
148	socksv = 5;
149	host = NULL;
150	uport = NULL;
151	sv = NULL;
152
153	while ((ch = getopt_long(argc, argv,
154	    "46DdEe:hI:i:jklnO:oP:p:rSs:tT:UuV:vw:X:x:z",
155	    longopts, NULL)) != -1) {
156		switch (ch) {
157		case '4':
158			family = AF_INET;
159			break;
160		case '6':
161			family = AF_INET6;
162			break;
163		case 'U':
164			family = AF_UNIX;
165			break;
166		case 'X':
167			if (strcasecmp(optarg, "connect") == 0)
168				socksv = -1; /* HTTP proxy CONNECT */
169			else if (strcmp(optarg, "4") == 0)
170				socksv = 4; /* SOCKS v.4 */
171			else if (strcmp(optarg, "5") == 0)
172				socksv = 5; /* SOCKS v.5 */
173			else
174				errx(1, "unsupported proxy protocol");
175			break;
176		case 'd':
177			dflag = 1;
178			break;
179		case 'e':
180#ifdef IPSEC
181			ipsec_policy[ipsec_count++ % 2] = optarg;
182#else
183			errx(1, "IPsec support unavailable.");
184#endif
185			break;
186		case 'E':
187#ifdef IPSEC
188			ipsec_policy[0] = "in  ipsec esp/transport//require";
189			ipsec_policy[1] = "out ipsec esp/transport//require";
190#else
191			errx(1, "IPsec support unavailable.");
192#endif
193			break;
194		case 'h':
195			help();
196			break;
197		case 'i':
198			iflag = strtonum(optarg, 0, UINT_MAX, &errstr);
199			if (errstr)
200				errx(1, "interval %s: %s", errstr, optarg);
201			break;
202#ifdef SO_JUMBO
203		case 'j':
204			jflag = 1;
205			break;
206#endif
207		case 'k':
208			kflag = 1;
209			break;
210		case 'l':
211			lflag = 1;
212			break;
213		case 'n':
214			nflag = 1;
215			break;
216		case 'o':
217			oflag = 1;
218			break;
219		case 'P':
220			Pflag = optarg;
221			break;
222		case 'p':
223			pflag = optarg;
224			break;
225		case 'r':
226			rflag = 1;
227			break;
228		case 's':
229			sflag = optarg;
230			break;
231		case 't':
232			tflag = 1;
233			break;
234		case 'u':
235			uflag = 1;
236			break;
237		case 'V':
238			if (sysctlbyname("net.fibs", &numfibs, &intsize, NULL, 0) == -1)
239				errx(1, "Multiple FIBS not supported");
240			rdomain = (unsigned int)strtonum(optarg, 0,
241			    numfibs - 1, &errstr);
242			if (errstr)
243				errx(1, "FIB %s: %s", errstr, optarg);
244			break;
245		case 'v':
246			vflag = 1;
247			break;
248		case 'w':
249			timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
250			if (errstr)
251				errx(1, "timeout %s: %s", errstr, optarg);
252			timeout *= 1000;
253			break;
254		case 'x':
255			xflag = 1;
256			if ((proxy = strdup(optarg)) == NULL)
257				err(1, NULL);
258			break;
259		case 'z':
260			zflag = 1;
261			break;
262		case 'D':
263			Dflag = 1;
264			break;
265		case 'I':
266			Iflag = strtonum(optarg, 1, 65536 << 14, &errstr);
267			if (errstr != NULL)
268				errx(1, "TCP receive window %s: %s",
269				    errstr, optarg);
270			break;
271		case 'O':
272			Oflag = strtonum(optarg, 1, 65536 << 14, &errstr);
273			if (errstr != NULL) {
274			    if (strcmp(errstr, "invalid") != 0)
275				errx(1, "TCP send window %s: %s",
276				    errstr, optarg);
277			}
278			break;
279		case 'S':
280			Sflag = 1;
281			break;
282		case 'T':
283			Tflag = parse_iptos(optarg);
284			break;
285		case 0:
286			break;
287		default:
288			usage(1);
289		}
290	}
291	argc -= optind;
292	argv += optind;
293
294	/* Cruft to make sure options are clean, and used properly. */
295	if (argv[0] && !argv[1] && family == AF_UNIX) {
296		if (uflag)
297			errx(1, "cannot use -u and -U");
298		host = argv[0];
299		uport = NULL;
300	} else if (argv[0] && !argv[1]) {
301		if  (!lflag)
302			usage(1);
303		uport = argv[0];
304		host = NULL;
305	} else if (argv[0] && argv[1]) {
306		host = argv[0];
307		uport = argv[1];
308	} else
309		usage(1);
310
311	if (lflag && sflag)
312		errx(1, "cannot use -s and -l");
313	if (lflag && pflag)
314		errx(1, "cannot use -p and -l");
315	if (lflag && zflag)
316		errx(1, "cannot use -z and -l");
317	if (!lflag && kflag)
318		errx(1, "must use -l with -k");
319
320	/* Initialize addrinfo structure. */
321	if (family != AF_UNIX) {
322		memset(&hints, 0, sizeof(struct addrinfo));
323		hints.ai_family = family;
324		hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
325		hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
326		if (nflag)
327			hints.ai_flags |= AI_NUMERICHOST;
328	}
329
330	if (xflag) {
331		if (uflag)
332			errx(1, "no proxy support for UDP mode");
333
334		if (lflag)
335			errx(1, "no proxy support for listen");
336
337		if (family == AF_UNIX)
338			errx(1, "no proxy support for unix sockets");
339
340		/* XXX IPv6 transport to proxy would probably work */
341		if (family == AF_INET6)
342			errx(1, "no proxy support for IPv6");
343
344		if (sflag)
345			errx(1, "no proxy support for local source address");
346
347		proxyhost = strsep(&proxy, ":");
348		proxyport = proxy;
349
350		memset(&proxyhints, 0, sizeof(struct addrinfo));
351		proxyhints.ai_family = family;
352		proxyhints.ai_socktype = SOCK_STREAM;
353		proxyhints.ai_protocol = IPPROTO_TCP;
354		if (nflag)
355			proxyhints.ai_flags |= AI_NUMERICHOST;
356	}
357
358	if (lflag) {
359		int connfd;
360		ret = 0;
361
362		if (family == AF_UNIX)
363			s = unix_listen(host);
364
365		/* Allow only one connection at a time, but stay alive. */
366		for (;;) {
367			if (family != AF_UNIX)
368				s = local_listen(host, uport, hints);
369			if (s < 0)
370				err(1, NULL);
371			/*
372			 * For UDP, we will use recvfrom() initially
373			 * to wait for a caller, then use the regular
374			 * functions to talk to the caller.
375			 */
376			if (uflag) {
377				int rv, plen;
378				char buf[8192];
379				struct sockaddr_storage z;
380
381				len = sizeof(z);
382				plen = jflag ? 8192 : 1024;
383				rv = recvfrom(s, buf, plen, MSG_PEEK,
384				    (struct sockaddr *)&z, &len);
385				if (rv < 0)
386					err(1, "recvfrom");
387
388				rv = connect(s, (struct sockaddr *)&z, len);
389				if (rv < 0)
390					err(1, "connect");
391
392				connfd = s;
393			} else {
394				len = sizeof(cliaddr);
395				connfd = accept(s, (struct sockaddr *)&cliaddr,
396				    &len);
397			}
398
399			readwrite(connfd);
400			close(connfd);
401			if (family != AF_UNIX)
402				close(s);
403
404			if (!kflag)
405				break;
406		}
407	} else if (family == AF_UNIX) {
408		ret = 0;
409
410		if ((s = unix_connect(host)) > 0 && !zflag) {
411			readwrite(s);
412			close(s);
413		} else
414			ret = 1;
415
416		exit(ret);
417
418	} else {
419		int i = 0;
420
421		/* Construct the portlist[] array. */
422		build_ports(uport);
423
424		/* Cycle through portlist, connecting to each port. */
425		for (i = 0; portlist[i] != NULL; i++) {
426			if (s)
427				close(s);
428
429			if (xflag)
430				s = socks_connect(host, portlist[i], hints,
431				    proxyhost, proxyport, proxyhints, socksv,
432				    Pflag);
433			else
434				s = remote_connect(host, portlist[i], hints);
435
436			if (s < 0)
437				continue;
438
439			ret = 0;
440			if (vflag || zflag) {
441				/* For UDP, make sure we are connected. */
442				if (uflag) {
443					if (udptest(s) == -1) {
444						ret = 1;
445						continue;
446					}
447				}
448
449				/* Don't look up port if -n. */
450				if (nflag)
451					sv = NULL;
452				else {
453					sv = getservbyport(
454					    ntohs(atoi(portlist[i])),
455					    uflag ? "udp" : "tcp");
456				}
457
458				fprintf(stderr,
459				    "Connection to %s %s port [%s/%s] "
460				    "succeeded!\n", host, portlist[i],
461				    uflag ? "udp" : "tcp",
462				    sv ? sv->s_name : "*");
463			}
464			if (!zflag)
465				readwrite(s);
466		}
467	}
468
469	if (s)
470		close(s);
471
472	exit(ret);
473}
474
475/*
476 * unix_connect()
477 * Returns a socket connected to a local unix socket. Returns -1 on failure.
478 */
479int
480unix_connect(char *path)
481{
482	struct sockaddr_un sun;
483	int s;
484
485	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
486		return (-1);
487	(void)fcntl(s, F_SETFD, 1);
488
489	memset(&sun, 0, sizeof(struct sockaddr_un));
490	sun.sun_family = AF_UNIX;
491
492	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
493	    sizeof(sun.sun_path)) {
494		close(s);
495		errno = ENAMETOOLONG;
496		return (-1);
497	}
498	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
499		close(s);
500		return (-1);
501	}
502	return (s);
503
504}
505
506/*
507 * unix_listen()
508 * Create a unix domain socket, and listen on it.
509 */
510int
511unix_listen(char *path)
512{
513	struct sockaddr_un sun;
514	int s;
515
516	/* Create unix domain socket. */
517	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
518		return (-1);
519
520	memset(&sun, 0, sizeof(struct sockaddr_un));
521	sun.sun_family = AF_UNIX;
522
523	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
524	    sizeof(sun.sun_path)) {
525		close(s);
526		errno = ENAMETOOLONG;
527		return (-1);
528	}
529
530	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
531		close(s);
532		return (-1);
533	}
534
535	if (listen(s, 5) < 0) {
536		close(s);
537		return (-1);
538	}
539	return (s);
540}
541
542/*
543 * remote_connect()
544 * Returns a socket connected to a remote host. Properly binds to a local
545 * port or source address if needed. Returns -1 on failure.
546 */
547int
548remote_connect(const char *host, const char *port, struct addrinfo hints)
549{
550	struct addrinfo *res, *res0;
551	int s, error, on = 1;
552
553	if ((error = getaddrinfo(host, port, &hints, &res)))
554		errx(1, "getaddrinfo: %s", gai_strerror(error));
555
556	res0 = res;
557	do {
558		if ((s = socket(res0->ai_family, res0->ai_socktype,
559		    res0->ai_protocol)) < 0)
560			continue;
561#ifdef IPSEC
562		if (ipsec_policy[0] != NULL)
563			add_ipsec_policy(s, ipsec_policy[0]);
564		if (ipsec_policy[1] != NULL)
565			add_ipsec_policy(s, ipsec_policy[1]);
566#endif
567
568		if (rdomain) {
569			if (setfib(rdomain) == -1)
570				err(1, "setfib");
571		}
572
573		/* Bind to a local port or source address if specified. */
574		if (sflag || pflag) {
575			struct addrinfo ahints, *ares;
576
577#ifdef SO_BINDANY
578			/* try SO_BINDANY, but don't insist */
579			setsockopt(s, SOL_SOCKET, SO_BINDANY, &on, sizeof(on));
580#endif
581			memset(&ahints, 0, sizeof(struct addrinfo));
582			ahints.ai_family = res0->ai_family;
583			ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
584			ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
585			ahints.ai_flags = AI_PASSIVE;
586			if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
587				errx(1, "getaddrinfo: %s", gai_strerror(error));
588
589			if (bind(s, (struct sockaddr *)ares->ai_addr,
590			    ares->ai_addrlen) < 0)
591				errx(1, "bind failed: %s", strerror(errno));
592			freeaddrinfo(ares);
593		}
594
595		set_common_sockopts(s);
596
597		if (connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
598			break;
599		else if (vflag)
600			warn("connect to %s port %s (%s) failed", host, port,
601			    uflag ? "udp" : "tcp");
602
603		close(s);
604		s = -1;
605	} while ((res0 = res0->ai_next) != NULL);
606
607	freeaddrinfo(res);
608
609	return (s);
610}
611
612/*
613 * local_listen()
614 * Returns a socket listening on a local port, binds to specified source
615 * address. Returns -1 on failure.
616 */
617int
618local_listen(char *host, char *port, struct addrinfo hints)
619{
620	struct addrinfo *res, *res0;
621	int s, ret, x = 1;
622	int error;
623
624	/* Allow nodename to be null. */
625	hints.ai_flags |= AI_PASSIVE;
626
627	/*
628	 * In the case of binding to a wildcard address
629	 * default to binding to an ipv4 address.
630	 */
631	if (host == NULL && hints.ai_family == AF_UNSPEC)
632		hints.ai_family = AF_INET;
633
634	if ((error = getaddrinfo(host, port, &hints, &res)))
635		errx(1, "getaddrinfo: %s", gai_strerror(error));
636
637	res0 = res;
638	do {
639		if ((s = socket(res0->ai_family, res0->ai_socktype,
640		    res0->ai_protocol)) < 0)
641			continue;
642
643		if (rdomain) {
644			if (setfib(rdomain) == -1)
645				err(1, "setfib");
646		}
647
648		ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
649		if (ret == -1)
650			err(1, NULL);
651#ifdef IPSEC
652		if (ipsec_policy[0] != NULL)
653			add_ipsec_policy(s, ipsec_policy[0]);
654		if (ipsec_policy[1] != NULL)
655			add_ipsec_policy(s, ipsec_policy[1]);
656#endif
657		if (FreeBSD_Oflag) {
658			if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
659			    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
660				err(1, "disable TCP options");
661		}
662
663		if (bind(s, (struct sockaddr *)res0->ai_addr,
664		    res0->ai_addrlen) == 0)
665			break;
666
667		close(s);
668		s = -1;
669	} while ((res0 = res0->ai_next) != NULL);
670
671	if (!uflag && s != -1) {
672		if (listen(s, 1) < 0)
673			err(1, "listen");
674	}
675
676	freeaddrinfo(res);
677
678	return (s);
679}
680
681/*
682 * readwrite()
683 * Loop that polls on the network file descriptor and stdin.
684 */
685void
686readwrite(int nfd)
687{
688	struct pollfd pfd[2];
689	unsigned char buf[8192];
690	int n, wfd = fileno(stdin);
691	int lfd = fileno(stdout);
692	int plen;
693
694	plen = jflag ? 8192 : 1024;
695
696	/* Setup Network FD */
697	pfd[0].fd = nfd;
698	pfd[0].events = POLLIN;
699
700	/* Set up STDIN FD. */
701	pfd[1].fd = wfd;
702	pfd[1].events = POLLIN;
703
704	while (pfd[0].fd != -1) {
705		if (iflag)
706			sleep(iflag);
707
708		if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
709			close(nfd);
710			err(1, "Polling Error");
711		}
712
713		if (n == 0)
714			return;
715
716		if (pfd[0].revents & POLLIN) {
717			if ((n = read(nfd, buf, plen)) < 0)
718				return;
719			else if (n == 0) {
720				shutdown(nfd, SHUT_RD);
721				pfd[0].fd = -1;
722				pfd[0].events = 0;
723			} else {
724				if (tflag)
725					atelnet(nfd, buf, n);
726				if (atomicio(vwrite, lfd, buf, n) != n)
727					return;
728			}
729		}
730
731		if (!dflag && pfd[1].revents & POLLIN) {
732			if ((n = read(wfd, buf, plen)) < 0 ||
733			    (oflag && n == 0)) {
734				return;
735			} else if (n == 0) {
736				shutdown(nfd, SHUT_WR);
737				pfd[1].fd = -1;
738				pfd[1].events = 0;
739			} else {
740				if (atomicio(vwrite, nfd, buf, n) != n)
741					return;
742			}
743		}
744	}
745}
746
747/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
748void
749atelnet(int nfd, unsigned char *buf, unsigned int size)
750{
751	unsigned char *p, *end;
752	unsigned char obuf[4];
753
754	if (size < 3)
755		return;
756	end = buf + size - 2;
757
758	for (p = buf; p < end; p++) {
759		if (*p != IAC)
760			continue;
761
762		obuf[0] = IAC;
763		p++;
764		if ((*p == WILL) || (*p == WONT))
765			obuf[1] = DONT;
766		else if ((*p == DO) || (*p == DONT))
767			obuf[1] = WONT;
768		else
769			continue;
770
771		p++;
772		obuf[2] = *p;
773		if (atomicio(vwrite, nfd, obuf, 3) != 3)
774			warn("Write Error!");
775	}
776}
777
778/*
779 * build_ports()
780 * Build an array or ports in portlist[], listing each port
781 * that we should try to connect to.
782 */
783void
784build_ports(char *p)
785{
786	const char *errstr;
787	char *n;
788	int hi, lo, cp;
789	int x = 0;
790
791	if ((n = strchr(p, '-')) != NULL) {
792		if (lflag)
793			errx(1, "Cannot use -l with multiple ports!");
794
795		*n = '\0';
796		n++;
797
798		/* Make sure the ports are in order: lowest->highest. */
799		hi = strtonum(n, 1, PORT_MAX, &errstr);
800		if (errstr)
801			errx(1, "port number %s: %s", errstr, n);
802		lo = strtonum(p, 1, PORT_MAX, &errstr);
803		if (errstr)
804			errx(1, "port number %s: %s", errstr, p);
805
806		if (lo > hi) {
807			cp = hi;
808			hi = lo;
809			lo = cp;
810		}
811
812		/* Load ports sequentially. */
813		for (cp = lo; cp <= hi; cp++) {
814			portlist[x] = calloc(1, PORT_MAX_LEN);
815			if (portlist[x] == NULL)
816				err(1, NULL);
817			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
818			x++;
819		}
820
821		/* Randomly swap ports. */
822		if (rflag) {
823			int y;
824			char *c;
825
826			for (x = 0; x <= (hi - lo); x++) {
827				y = (arc4random() & 0xFFFF) % (hi - lo);
828				c = portlist[x];
829				portlist[x] = portlist[y];
830				portlist[y] = c;
831			}
832		}
833	} else {
834		hi = strtonum(p, 1, PORT_MAX, &errstr);
835		if (errstr)
836			errx(1, "port number %s: %s", errstr, p);
837		portlist[0] = calloc(1, PORT_MAX_LEN);
838		if (portlist[0] == NULL)
839			err(1, NULL);
840		portlist[0] = p;
841	}
842}
843
844/*
845 * udptest()
846 * Do a few writes to see if the UDP port is there.
847 * XXX - Better way of doing this? Doesn't work for IPv6.
848 * Also fails after around 100 ports checked.
849 */
850int
851udptest(int s)
852{
853	int i, ret;
854
855	for (i = 0; i <= 3; i++) {
856		if (write(s, "X", 1) == 1)
857			ret = 1;
858		else
859			ret = -1;
860	}
861	return (ret);
862}
863
864void
865set_common_sockopts(int s)
866{
867	int x = 1;
868
869	if (Sflag) {
870		if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
871			&x, sizeof(x)) == -1)
872			err(1, NULL);
873	}
874	if (Dflag) {
875		if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
876			&x, sizeof(x)) == -1)
877			err(1, NULL);
878	}
879#ifdef SO_JUMBO
880	if (jflag) {
881		if (setsockopt(s, SOL_SOCKET, SO_JUMBO,
882			&x, sizeof(x)) == -1)
883			err(1, NULL);
884	}
885#endif
886	if (Tflag != -1) {
887		if (setsockopt(s, IPPROTO_IP, IP_TOS,
888		    &Tflag, sizeof(Tflag)) == -1)
889			err(1, "set IP ToS");
890	}
891	if (Iflag) {
892		if (setsockopt(s, SOL_SOCKET, SO_RCVBUF,
893		    &Iflag, sizeof(Iflag)) == -1)
894			err(1, "set TCP receive buffer size");
895	}
896	if (Oflag) {
897		if (setsockopt(s, SOL_SOCKET, SO_SNDBUF,
898		    &Oflag, sizeof(Oflag)) == -1)
899			err(1, "set TCP send buffer size");
900	}
901	if (FreeBSD_Oflag) {
902		if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
903		    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
904			err(1, "disable TCP options");
905	}
906}
907
908int
909parse_iptos(char *s)
910{
911	int tos = -1;
912
913	if (strcmp(s, "lowdelay") == 0)
914		return (IPTOS_LOWDELAY);
915	if (strcmp(s, "throughput") == 0)
916		return (IPTOS_THROUGHPUT);
917	if (strcmp(s, "reliability") == 0)
918		return (IPTOS_RELIABILITY);
919
920	if (sscanf(s, "0x%x", &tos) != 1 || tos < 0 || tos > 0xff)
921		errx(1, "invalid IP Type of Service");
922	return (tos);
923}
924
925void
926help(void)
927{
928	usage(0);
929	fprintf(stderr, "\tCommand Summary:\n\
930	\t-4		Use IPv4\n\
931	\t-6		Use IPv6\n\
932	\t-D		Enable the debug socket option\n\
933	\t-d		Detach from stdin\n");
934#ifdef IPSEC
935	fprintf(stderr, "\
936	\t-E		Use IPsec ESP\n\
937	\t-e policy	Use specified IPsec policy\n");
938#endif
939	fprintf(stderr, "\
940	\t-h		This help text\n\
941	\t-I length	TCP receive buffer length\n\
942	\t-i secs\t	Delay interval for lines sent, ports scanned\n\
943	\t-k		Keep inbound sockets open for multiple connects\n\
944	\t-l		Listen mode, for inbound connects\n\
945	\t-n		Suppress name/port resolutions\n\
946	\t--no-tcpopt	Disable TCP options\n\
947	\t-O length	TCP send buffer length\n\
948	\t-o		Terminate on EOF on input\n\
949	\t-P proxyuser\tUsername for proxy authentication\n\
950	\t-p port\t	Specify local port for remote connects\n\
951	\t-r		Randomize remote ports\n\
952	\t-S		Enable the TCP MD5 signature option\n\
953	\t-s addr\t	Local source address\n\
954	\t-T ToS\t	Set IP Type of Service\n\
955	\t-t		Answer TELNET negotiation\n\
956	\t-U		Use UNIX domain socket\n\
957	\t-u		UDP mode\n\
958	\t-V fib	Specify alternate routing table (FIB)\n\
959	\t-v		Verbose\n\
960	\t-w secs\t	Timeout for connects and final net reads\n\
961	\t-X proto	Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
962	\t-x addr[:port]\tSpecify proxy address and port\n\
963	\t-z		Zero-I/O mode [used for scanning]\n\
964	Port numbers can be individual or ranges: lo-hi [inclusive]\n");
965#ifdef IPSEC
966	fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n");
967#endif
968	exit(1);
969}
970
971#ifdef IPSEC
972void
973add_ipsec_policy(int s, char *policy)
974{
975	char *raw;
976	int e;
977
978	raw = ipsec_set_policy(policy, strlen(policy));
979	if (raw == NULL)
980		errx(1, "ipsec_set_policy `%s': %s", policy,
981		     ipsec_strerror());
982	e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw,
983			ipsec_get_policylen(raw));
984	if (e < 0)
985		err(1, "ipsec policy cannot be configured");
986	free(raw);
987	if (vflag)
988		fprintf(stderr, "ipsec policy configured: `%s'\n", policy);
989	return;
990}
991#endif /* IPSEC */
992
993void
994usage(int ret)
995{
996	fprintf(stderr,
997#ifdef IPSEC
998	    "usage: nc [-46DdEhklnorStUuvz] [-e policy] [-I length] [-i interval] [-O length]\n"
999#else
1000	    "usage: nc [-46DdhklnorStUuvz] [-I length] [-i interval] [-O length]\n"
1001#endif
1002	    "\t  [-P proxy_username] [-p source_port] [-s source_ip_address] [-T ToS]\n"
1003	    "\t  [-V fib] [-w timeout] [-X proxy_protocol]\n"
1004	    "\t  [-x proxy_address[:port]] [hostname] [port]\n");
1005	if (ret)
1006		exit(1);
1007}
1008