netcat.c revision 214047 
1/* $OpenBSD: netcat.c,v 1.98 2010/07/03 04:44:51 guenther 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 214047 2010-10-19 00:01:53Z 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	dflag;					/* detached, no stdin */
76unsigned int iflag;				/* Interval Flag */
77int	jflag;					/* use jumbo frames if we can */
78int	kflag;					/* More than one connect */
79int	lflag;					/* Bind to local port */
80int	nflag;					/* Don't do name look up */
81int	FreeBSD_Oflag;				/* Do not use TCP options */
82char   *Pflag;					/* Proxy username */
83char   *pflag;					/* Localport flag */
84int	rflag;					/* Random ports flag */
85char   *sflag;					/* Source Address */
86int	tflag;					/* Telnet Emulation */
87int	uflag;					/* UDP - Default to TCP */
88int	vflag;					/* Verbosity */
89int	xflag;					/* Socks proxy */
90int	zflag;					/* Port Scan Flag */
91int	Dflag;					/* sodebug */
92int	Iflag;					/* TCP receive buffer size */
93int	Oflag;					/* TCP send buffer size */
94int	Sflag;					/* TCP MD5 signature option */
95int	Tflag = -1;				/* IP Type of Service */
96u_int	rtableid;
97
98int timeout = -1;
99int family = AF_UNSPEC;
100char *portlist[PORT_MAX+1];
101
102void	atelnet(int, unsigned char *, unsigned int);
103void	build_ports(char *);
104void	help(void);
105int	local_listen(char *, char *, struct addrinfo);
106void	readwrite(int);
107int	remote_connect(const char *, const char *, struct addrinfo);
108int	socks_connect(const char *, const char *, struct addrinfo,
109	    const char *, const char *, struct addrinfo, int, const char *);
110int	udptest(int);
111int	unix_connect(char *);
112int	unix_listen(char *);
113void	set_common_sockopts(int);
114int	parse_iptos(char *);
115void	usage(int);
116
117#ifdef IPSEC
118void	add_ipsec_policy(int, char *);
119
120char	*ipsec_policy[2];
121#endif
122
123int
124main(int argc, char *argv[])
125{
126	int ch, s, ret, socksv, ipsec_count;
127	int numfibs;
128	size_t intsize = sizeof(int);
129	char *host, *uport;
130	struct addrinfo hints;
131	struct servent *sv;
132	socklen_t len;
133	struct sockaddr_storage cliaddr;
134	char *proxy;
135	const char *errstr, *proxyhost = "", *proxyport = NULL;
136	struct addrinfo proxyhints;
137	struct option longopts[] = {
138		{ "no-tcpopt",	no_argument,	&FreeBSD_Oflag,	1 },
139		{ NULL,		0,		NULL,		0 }
140	};
141
142	ret = 1;
143	ipsec_count = 0;
144	s = 0;
145	socksv = 5;
146	host = NULL;
147	uport = NULL;
148	sv = NULL;
149
150	while ((ch = getopt_long(argc, argv,
151	    "46DdEe:hI:i:jklnoO:P:p:rSs:tT:UuV:vw:X:x:z",
152	    longopts, NULL)) != -1) {
153		switch (ch) {
154		case '4':
155			family = AF_INET;
156			break;
157		case '6':
158			family = AF_INET6;
159			break;
160		case 'U':
161			family = AF_UNIX;
162			break;
163		case 'X':
164			if (strcasecmp(optarg, "connect") == 0)
165				socksv = -1; /* HTTP proxy CONNECT */
166			else if (strcmp(optarg, "4") == 0)
167				socksv = 4; /* SOCKS v.4 */
168			else if (strcmp(optarg, "5") == 0)
169				socksv = 5; /* SOCKS v.5 */
170			else
171				errx(1, "unsupported proxy protocol");
172			break;
173		case 'd':
174			dflag = 1;
175			break;
176		case 'e':
177#ifdef IPSEC
178			ipsec_policy[ipsec_count++ % 2] = optarg;
179#else
180			errx(1, "IPsec support unavailable.");
181#endif
182			break;
183		case 'E':
184#ifdef IPSEC
185			ipsec_policy[0] = "in  ipsec esp/transport//require";
186			ipsec_policy[1] = "out ipsec esp/transport//require";
187#else
188			errx(1, "IPsec support unavailable.");
189#endif
190			break;
191		case 'h':
192			help();
193			break;
194		case 'i':
195			iflag = strtonum(optarg, 0, UINT_MAX, &errstr);
196			if (errstr)
197				errx(1, "interval %s: %s", errstr, optarg);
198			break;
199#ifdef SO_JUMBO
200		case 'j':
201			jflag = 1;
202			break;
203#endif
204		case 'k':
205			kflag = 1;
206			break;
207		case 'l':
208			lflag = 1;
209			break;
210		case 'n':
211			nflag = 1;
212			break;
213		case 'o':
214			fprintf(stderr, "option -o is deprecated.\n");
215			break;
216		case 'P':
217			Pflag = optarg;
218			break;
219		case 'p':
220			pflag = optarg;
221			break;
222		case 'r':
223			rflag = 1;
224			break;
225		case 's':
226			sflag = optarg;
227			break;
228		case 't':
229			tflag = 1;
230			break;
231		case 'u':
232			uflag = 1;
233			break;
234		case 'V':
235			if (sysctlbyname("net.fibs", &numfibs, &intsize, NULL, 0) == -1)
236				errx(1, "Multiple FIBS not supported");
237			rtableid = (unsigned int)strtonum(optarg, 0,
238			    numfibs - 1, &errstr);
239			if (errstr)
240				errx(1, "rtable %s: %s", errstr, optarg);
241			break;
242		case 'v':
243			vflag = 1;
244			break;
245		case 'w':
246			timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
247			if (errstr)
248				errx(1, "timeout %s: %s", errstr, optarg);
249			timeout *= 1000;
250			break;
251		case 'x':
252			xflag = 1;
253			if ((proxy = strdup(optarg)) == NULL)
254				err(1, NULL);
255			break;
256		case 'z':
257			zflag = 1;
258			break;
259		case 'D':
260			Dflag = 1;
261			break;
262		case 'I':
263			Iflag = strtonum(optarg, 1, 65536 << 14, &errstr);
264			if (errstr != NULL)
265				errx(1, "TCP receive window %s: %s",
266				    errstr, optarg);
267			break;
268		case 'O':
269			Oflag = strtonum(optarg, 1, 65536 << 14, &errstr);
270			if (errstr != NULL) {
271			    if (strcmp(errstr, "invalid") != 0)
272				errx(1, "TCP send window %s: %s",
273				    errstr, optarg);
274			}
275			break;
276		case 'S':
277			Sflag = 1;
278			break;
279		case 'T':
280			Tflag = parse_iptos(optarg);
281			break;
282		default:
283			usage(1);
284		}
285	}
286	argc -= optind;
287	argv += optind;
288
289	/* Cruft to make sure options are clean, and used properly. */
290	if (argv[0] && !argv[1] && family == AF_UNIX) {
291		if (uflag)
292			errx(1, "cannot use -u and -U");
293		host = argv[0];
294		uport = NULL;
295	} else if (argv[0] && !argv[1]) {
296		if  (!lflag)
297			usage(1);
298		uport = argv[0];
299		host = NULL;
300	} else if (argv[0] && argv[1]) {
301		host = argv[0];
302		uport = argv[1];
303	} else
304		usage(1);
305
306	if (lflag && sflag)
307		errx(1, "cannot use -s and -l");
308	if (lflag && pflag)
309		errx(1, "cannot use -p and -l");
310	if (lflag && zflag)
311		errx(1, "cannot use -z and -l");
312	if (!lflag && kflag)
313		errx(1, "must use -l with -k");
314
315	/* Initialize addrinfo structure. */
316	if (family != AF_UNIX) {
317		memset(&hints, 0, sizeof(struct addrinfo));
318		hints.ai_family = family;
319		hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
320		hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
321		if (nflag)
322			hints.ai_flags |= AI_NUMERICHOST;
323	}
324
325	if (xflag) {
326		if (uflag)
327			errx(1, "no proxy support for UDP mode");
328
329		if (lflag)
330			errx(1, "no proxy support for listen");
331
332		if (family == AF_UNIX)
333			errx(1, "no proxy support for unix sockets");
334
335		/* XXX IPv6 transport to proxy would probably work */
336		if (family == AF_INET6)
337			errx(1, "no proxy support for IPv6");
338
339		if (sflag)
340			errx(1, "no proxy support for local source address");
341
342		proxyhost = strsep(&proxy, ":");
343		proxyport = proxy;
344
345		memset(&proxyhints, 0, sizeof(struct addrinfo));
346		proxyhints.ai_family = family;
347		proxyhints.ai_socktype = SOCK_STREAM;
348		proxyhints.ai_protocol = IPPROTO_TCP;
349		if (nflag)
350			proxyhints.ai_flags |= AI_NUMERICHOST;
351	}
352
353	if (lflag) {
354		int connfd;
355		ret = 0;
356
357		if (family == AF_UNIX)
358			s = unix_listen(host);
359
360		/* Allow only one connection at a time, but stay alive. */
361		for (;;) {
362			if (family != AF_UNIX)
363				s = local_listen(host, uport, hints);
364			if (s < 0)
365				err(1, NULL);
366			/*
367			 * For UDP, we will use recvfrom() initially
368			 * to wait for a caller, then use the regular
369			 * functions to talk to the caller.
370			 */
371			if (uflag) {
372				int rv, plen;
373				char buf[16384];
374				struct sockaddr_storage z;
375
376				len = sizeof(z);
377				plen = jflag ? 16384 : 2048;
378				rv = recvfrom(s, buf, plen, MSG_PEEK,
379				    (struct sockaddr *)&z, &len);
380				if (rv < 0)
381					err(1, "recvfrom");
382
383				rv = connect(s, (struct sockaddr *)&z, len);
384				if (rv < 0)
385					err(1, "connect");
386
387				connfd = s;
388			} else {
389				len = sizeof(cliaddr);
390				connfd = accept(s, (struct sockaddr *)&cliaddr,
391				    &len);
392			}
393
394			readwrite(connfd);
395			close(connfd);
396			if (family != AF_UNIX)
397				close(s);
398
399			if (!kflag)
400				break;
401		}
402	} else if (family == AF_UNIX) {
403		ret = 0;
404
405		if ((s = unix_connect(host)) > 0 && !zflag) {
406			readwrite(s);
407			close(s);
408		} else
409			ret = 1;
410
411		exit(ret);
412
413	} else {
414		int i = 0;
415
416		/* Construct the portlist[] array. */
417		build_ports(uport);
418
419		/* Cycle through portlist, connecting to each port. */
420		for (i = 0; portlist[i] != NULL; i++) {
421			if (s)
422				close(s);
423
424			if (xflag)
425				s = socks_connect(host, portlist[i], hints,
426				    proxyhost, proxyport, proxyhints, socksv,
427				    Pflag);
428			else
429				s = remote_connect(host, portlist[i], hints);
430
431			if (s < 0)
432				continue;
433
434			ret = 0;
435			if (vflag || zflag) {
436				/* For UDP, make sure we are connected. */
437				if (uflag) {
438					if (udptest(s) == -1) {
439						ret = 1;
440						continue;
441					}
442				}
443
444				/* Don't look up port if -n. */
445				if (nflag)
446					sv = NULL;
447				else {
448					sv = getservbyport(
449					    ntohs(atoi(portlist[i])),
450					    uflag ? "udp" : "tcp");
451				}
452
453				fprintf(stderr,
454				    "Connection to %s %s port [%s/%s] "
455				    "succeeded!\n", host, portlist[i],
456				    uflag ? "udp" : "tcp",
457				    sv ? sv->s_name : "*");
458			}
459			if (!zflag)
460				readwrite(s);
461		}
462	}
463
464	if (s)
465		close(s);
466
467	exit(ret);
468}
469
470/*
471 * unix_connect()
472 * Returns a socket connected to a local unix socket. Returns -1 on failure.
473 */
474int
475unix_connect(char *path)
476{
477	struct sockaddr_un sun;
478	int s;
479
480	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
481		return (-1);
482	(void)fcntl(s, F_SETFD, 1);
483
484	memset(&sun, 0, sizeof(struct sockaddr_un));
485	sun.sun_family = AF_UNIX;
486
487	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
488	    sizeof(sun.sun_path)) {
489		close(s);
490		errno = ENAMETOOLONG;
491		return (-1);
492	}
493	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
494		close(s);
495		return (-1);
496	}
497	return (s);
498
499}
500
501/*
502 * unix_listen()
503 * Create a unix domain socket, and listen on it.
504 */
505int
506unix_listen(char *path)
507{
508	struct sockaddr_un sun;
509	int s;
510
511	/* Create unix domain socket. */
512	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
513		return (-1);
514
515	memset(&sun, 0, sizeof(struct sockaddr_un));
516	sun.sun_family = AF_UNIX;
517
518	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
519	    sizeof(sun.sun_path)) {
520		close(s);
521		errno = ENAMETOOLONG;
522		return (-1);
523	}
524
525	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
526		close(s);
527		return (-1);
528	}
529
530	if (listen(s, 5) < 0) {
531		close(s);
532		return (-1);
533	}
534	return (s);
535}
536
537/*
538 * remote_connect()
539 * Returns a socket connected to a remote host. Properly binds to a local
540 * port or source address if needed. Returns -1 on failure.
541 */
542int
543remote_connect(const char *host, const char *port, struct addrinfo hints)
544{
545	struct addrinfo *res, *res0;
546	int s, error, on = 1;
547
548	if ((error = getaddrinfo(host, port, &hints, &res)))
549		errx(1, "getaddrinfo: %s", gai_strerror(error));
550
551	res0 = res;
552	do {
553		if ((s = socket(res0->ai_family, res0->ai_socktype,
554		    res0->ai_protocol)) < 0)
555			continue;
556#ifdef IPSEC
557		if (ipsec_policy[0] != NULL)
558			add_ipsec_policy(s, ipsec_policy[0]);
559		if (ipsec_policy[1] != NULL)
560			add_ipsec_policy(s, ipsec_policy[1]);
561#endif
562
563		if (rtableid) {
564			if (setfib(rtableid) == -1)
565				err(1, "setfib");
566		}
567
568		/* Bind to a local port or source address if specified. */
569		if (sflag || pflag) {
570			struct addrinfo ahints, *ares;
571
572			/* try IP_BINDANY, but don't insist */
573			setsockopt(s, IPPROTO_IP, IP_BINDANY, &on, sizeof(on));
574			memset(&ahints, 0, sizeof(struct addrinfo));
575			ahints.ai_family = res0->ai_family;
576			ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
577			ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
578			ahints.ai_flags = AI_PASSIVE;
579			if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
580				errx(1, "getaddrinfo: %s", gai_strerror(error));
581
582			if (bind(s, (struct sockaddr *)ares->ai_addr,
583			    ares->ai_addrlen) < 0)
584				errx(1, "bind failed: %s", strerror(errno));
585			freeaddrinfo(ares);
586		}
587
588		set_common_sockopts(s);
589
590		if (connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
591			break;
592		else if (vflag)
593			warn("connect to %s port %s (%s) failed", host, port,
594			    uflag ? "udp" : "tcp");
595
596		close(s);
597		s = -1;
598	} while ((res0 = res0->ai_next) != NULL);
599
600	freeaddrinfo(res);
601
602	return (s);
603}
604
605/*
606 * local_listen()
607 * Returns a socket listening on a local port, binds to specified source
608 * address. Returns -1 on failure.
609 */
610int
611local_listen(char *host, char *port, struct addrinfo hints)
612{
613	struct addrinfo *res, *res0;
614	int s, ret, x = 1;
615	int error;
616
617	/* Allow nodename to be null. */
618	hints.ai_flags |= AI_PASSIVE;
619
620	/*
621	 * In the case of binding to a wildcard address
622	 * default to binding to an ipv4 address.
623	 */
624	if (host == NULL && hints.ai_family == AF_UNSPEC)
625		hints.ai_family = AF_INET;
626
627	if ((error = getaddrinfo(host, port, &hints, &res)))
628		errx(1, "getaddrinfo: %s", gai_strerror(error));
629
630	res0 = res;
631	do {
632		if ((s = socket(res0->ai_family, res0->ai_socktype,
633		    res0->ai_protocol)) < 0)
634			continue;
635
636		if (rtableid) {
637			if (setfib(rtableid) == -1)
638				err(1, "setfib");
639		}
640
641		ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
642		if (ret == -1)
643			err(1, NULL);
644#ifdef IPSEC
645		if (ipsec_policy[0] != NULL)
646			add_ipsec_policy(s, ipsec_policy[0]);
647		if (ipsec_policy[1] != NULL)
648			add_ipsec_policy(s, ipsec_policy[1]);
649#endif
650		if (FreeBSD_Oflag) {
651			if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
652			    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
653				err(1, "disable TCP options");
654		}
655
656		if (bind(s, (struct sockaddr *)res0->ai_addr,
657		    res0->ai_addrlen) == 0)
658			break;
659
660		close(s);
661		s = -1;
662	} while ((res0 = res0->ai_next) != NULL);
663
664	if (!uflag && s != -1) {
665		if (listen(s, 1) < 0)
666			err(1, "listen");
667	}
668
669	freeaddrinfo(res);
670
671	return (s);
672}
673
674/*
675 * readwrite()
676 * Loop that polls on the network file descriptor and stdin.
677 */
678void
679readwrite(int nfd)
680{
681	struct pollfd pfd[2];
682	unsigned char buf[16384];
683	int n, wfd = fileno(stdin);
684	int lfd = fileno(stdout);
685	int plen;
686
687	plen = jflag ? 16384 : 2048;
688
689	/* Setup Network FD */
690	pfd[0].fd = nfd;
691	pfd[0].events = POLLIN;
692
693	/* Set up STDIN FD. */
694	pfd[1].fd = wfd;
695	pfd[1].events = POLLIN;
696
697	while (pfd[0].fd != -1) {
698		if (iflag)
699			sleep(iflag);
700
701		if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
702			close(nfd);
703			err(1, "Polling Error");
704		}
705
706		if (n == 0)
707			return;
708
709		if (pfd[0].revents & POLLIN) {
710			if ((n = read(nfd, buf, plen)) < 0)
711				return;
712			else if (n == 0) {
713				shutdown(nfd, SHUT_RD);
714				pfd[0].fd = -1;
715				pfd[0].events = 0;
716			} else {
717				if (tflag)
718					atelnet(nfd, buf, n);
719				if (atomicio(vwrite, lfd, buf, n) != n)
720					return;
721			}
722		}
723
724		if (!dflag && pfd[1].revents & POLLIN) {
725			if ((n = read(wfd, buf, plen)) < 0)
726				return;
727			else if (n == 0) {
728				shutdown(nfd, SHUT_WR);
729				pfd[1].fd = -1;
730				pfd[1].events = 0;
731			} else {
732				if (atomicio(vwrite, nfd, buf, n) != n)
733					return;
734			}
735		}
736	}
737}
738
739/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
740void
741atelnet(int nfd, unsigned char *buf, unsigned int size)
742{
743	unsigned char *p, *end;
744	unsigned char obuf[4];
745
746	if (size < 3)
747		return;
748	end = buf + size - 2;
749
750	for (p = buf; p < end; p++) {
751		if (*p != IAC)
752			continue;
753
754		obuf[0] = IAC;
755		p++;
756		if ((*p == WILL) || (*p == WONT))
757			obuf[1] = DONT;
758		else if ((*p == DO) || (*p == DONT))
759			obuf[1] = WONT;
760		else
761			continue;
762
763		p++;
764		obuf[2] = *p;
765		if (atomicio(vwrite, nfd, obuf, 3) != 3)
766			warn("Write Error!");
767	}
768}
769
770/*
771 * build_ports()
772 * Build an array or ports in portlist[], listing each port
773 * that we should try to connect to.
774 */
775void
776build_ports(char *p)
777{
778	const char *errstr;
779	char *n;
780	int hi, lo, cp;
781	int x = 0;
782
783	if ((n = strchr(p, '-')) != NULL) {
784		if (lflag)
785			errx(1, "Cannot use -l with multiple ports!");
786
787		*n = '\0';
788		n++;
789
790		/* Make sure the ports are in order: lowest->highest. */
791		hi = strtonum(n, 1, PORT_MAX, &errstr);
792		if (errstr)
793			errx(1, "port number %s: %s", errstr, n);
794		lo = strtonum(p, 1, PORT_MAX, &errstr);
795		if (errstr)
796			errx(1, "port number %s: %s", errstr, p);
797
798		if (lo > hi) {
799			cp = hi;
800			hi = lo;
801			lo = cp;
802		}
803
804		/* Load ports sequentially. */
805		for (cp = lo; cp <= hi; cp++) {
806			portlist[x] = calloc(1, PORT_MAX_LEN);
807			if (portlist[x] == NULL)
808				err(1, NULL);
809			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
810			x++;
811		}
812
813		/* Randomly swap ports. */
814		if (rflag) {
815			int y;
816			char *c;
817
818			for (x = 0; x <= (hi - lo); x++) {
819				y = (arc4random() & 0xFFFF) % (hi - lo);
820				c = portlist[x];
821				portlist[x] = portlist[y];
822				portlist[y] = c;
823			}
824		}
825	} else {
826		hi = strtonum(p, 1, PORT_MAX, &errstr);
827		if (errstr)
828			errx(1, "port number %s: %s", errstr, p);
829		portlist[0] = strdup(p);
830		if (portlist[0] == NULL)
831			err(1, NULL);
832	}
833}
834
835/*
836 * udptest()
837 * Do a few writes to see if the UDP port is there.
838 * XXX - Better way of doing this? Doesn't work for IPv6.
839 * Also fails after around 100 ports checked.
840 */
841int
842udptest(int s)
843{
844	int i, ret;
845
846	for (i = 0; i <= 3; i++) {
847		if (write(s, "X", 1) == 1)
848			ret = 1;
849		else
850			ret = -1;
851	}
852	return (ret);
853}
854
855void
856set_common_sockopts(int s)
857{
858	int x = 1;
859
860	if (Sflag) {
861		if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
862			&x, sizeof(x)) == -1)
863			err(1, NULL);
864	}
865	if (Dflag) {
866		if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
867			&x, sizeof(x)) == -1)
868			err(1, NULL);
869	}
870#ifdef SO_JUMBO
871	if (jflag) {
872		if (setsockopt(s, SOL_SOCKET, SO_JUMBO,
873			&x, sizeof(x)) == -1)
874			err(1, NULL);
875	}
876#endif
877	if (Tflag != -1) {
878		if (setsockopt(s, IPPROTO_IP, IP_TOS,
879		    &Tflag, sizeof(Tflag)) == -1)
880			err(1, "set IP ToS");
881	}
882	if (Iflag) {
883		if (setsockopt(s, SOL_SOCKET, SO_RCVBUF,
884		    &Iflag, sizeof(Iflag)) == -1)
885			err(1, "set TCP receive buffer size");
886	}
887	if (Oflag) {
888		if (setsockopt(s, SOL_SOCKET, SO_SNDBUF,
889		    &Oflag, sizeof(Oflag)) == -1)
890			err(1, "set TCP send buffer size");
891	}
892	if (FreeBSD_Oflag) {
893		if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
894		    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
895			err(1, "disable TCP options");
896	}
897}
898
899int
900parse_iptos(char *s)
901{
902	int tos = -1;
903
904	if (strcmp(s, "lowdelay") == 0)
905		return (IPTOS_LOWDELAY);
906	if (strcmp(s, "throughput") == 0)
907		return (IPTOS_THROUGHPUT);
908	if (strcmp(s, "reliability") == 0)
909		return (IPTOS_RELIABILITY);
910
911	if (sscanf(s, "0x%x", &tos) != 1 || tos < 0 || tos > 0xff)
912		errx(1, "invalid IP Type of Service");
913	return (tos);
914}
915
916void
917help(void)
918{
919	usage(0);
920	fprintf(stderr, "\tCommand Summary:\n\
921	\t-4		Use IPv4\n\
922	\t-6		Use IPv6\n\
923	\t-D		Enable the debug socket option\n\
924	\t-d		Detach from stdin\n");
925#ifdef IPSEC
926	fprintf(stderr, "\
927	\t-E		Use IPsec ESP\n\
928	\t-e policy	Use specified IPsec policy\n");
929#endif
930	fprintf(stderr, "\
931	\t-h		This help text\n\
932	\t-I length	TCP receive buffer length\n\
933	\t-i secs\t	Delay interval for lines sent, ports scanned\n\
934	\t-k		Keep inbound sockets open for multiple connects\n\
935	\t-l		Listen mode, for inbound connects\n\
936	\t-n		Suppress name/port resolutions\n\
937	\t--no-tcpopt	Disable TCP options\n\
938	\t-O length	TCP send buffer length\n\
939	\t-P proxyuser\tUsername for proxy authentication\n\
940	\t-p port\t	Specify local port for remote connects\n\
941	\t-r		Randomize remote ports\n\
942	\t-S		Enable the TCP MD5 signature option\n\
943	\t-s addr\t	Local source address\n\
944	\t-T ToS\t	Set IP Type of Service\n\
945	\t-t		Answer TELNET negotiation\n\
946	\t-U		Use UNIX domain socket\n\
947	\t-u		UDP mode\n\
948	\t-V rtable	Specify alternate routing table\n\
949	\t-v		Verbose\n\
950	\t-w secs\t	Timeout for connects and final net reads\n\
951	\t-X proto	Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
952	\t-x addr[:port]\tSpecify proxy address and port\n\
953	\t-z		Zero-I/O mode [used for scanning]\n\
954	Port numbers can be individual or ranges: lo-hi [inclusive]\n");
955#ifdef IPSEC
956	fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n");
957#endif
958	exit(1);
959}
960
961#ifdef IPSEC
962void
963add_ipsec_policy(int s, char *policy)
964{
965	char *raw;
966	int e;
967
968	raw = ipsec_set_policy(policy, strlen(policy));
969	if (raw == NULL)
970		errx(1, "ipsec_set_policy `%s': %s", policy,
971		     ipsec_strerror());
972	e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw,
973			ipsec_get_policylen(raw));
974	if (e < 0)
975		err(1, "ipsec policy cannot be configured");
976	free(raw);
977	if (vflag)
978		fprintf(stderr, "ipsec policy configured: `%s'\n", policy);
979	return;
980}
981#endif /* IPSEC */
982
983void
984usage(int ret)
985{
986	fprintf(stderr,
987#ifdef IPSEC
988	    "usage: nc [-46DdEhklnrStUuvz] [-e policy] [-I length] [-i interval] [-O length]\n"
989#else
990	    "usage: nc [-46DdhklnrStUuvz] [-I length] [-i interval] [-O length]\n"
991#endif
992	    "\t  [-P proxy_username] [-p source_port] [-s source_ip_address] [-T ToS]\n"
993	    "\t  [-V rtable] [-w timeout] [-X proxy_protocol]\n"
994	    "\t  [-x proxy_address[:port]] [hostname] [port]\n");
995	if (ret)
996		exit(1);
997}
998