netcat.c revision 202640 
1/* $OpenBSD: netcat.c,v 1.93 2009/06/05 00:18:10 claudio 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 202640 2010-01-19 18:45:29Z 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				printf("Connection to %s %s port [%s/%s] succeeded!\n",
459				    host, portlist[i], uflag ? "udp" : "tcp",
460				    sv ? sv->s_name : "*");
461			}
462			if (!zflag)
463				readwrite(s);
464		}
465	}
466
467	if (s)
468		close(s);
469
470	exit(ret);
471}
472
473/*
474 * unix_connect()
475 * Returns a socket connected to a local unix socket. Returns -1 on failure.
476 */
477int
478unix_connect(char *path)
479{
480	struct sockaddr_un sun;
481	int s;
482
483	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
484		return (-1);
485	(void)fcntl(s, F_SETFD, 1);
486
487	memset(&sun, 0, sizeof(struct sockaddr_un));
488	sun.sun_family = AF_UNIX;
489
490	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
491	    sizeof(sun.sun_path)) {
492		close(s);
493		errno = ENAMETOOLONG;
494		return (-1);
495	}
496	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
497		close(s);
498		return (-1);
499	}
500	return (s);
501
502}
503
504/*
505 * unix_listen()
506 * Create a unix domain socket, and listen on it.
507 */
508int
509unix_listen(char *path)
510{
511	struct sockaddr_un sun;
512	int s;
513
514	/* Create unix domain socket. */
515	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
516		return (-1);
517
518	memset(&sun, 0, sizeof(struct sockaddr_un));
519	sun.sun_family = AF_UNIX;
520
521	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
522	    sizeof(sun.sun_path)) {
523		close(s);
524		errno = ENAMETOOLONG;
525		return (-1);
526	}
527
528	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
529		close(s);
530		return (-1);
531	}
532
533	if (listen(s, 5) < 0) {
534		close(s);
535		return (-1);
536	}
537	return (s);
538}
539
540/*
541 * remote_connect()
542 * Returns a socket connected to a remote host. Properly binds to a local
543 * port or source address if needed. Returns -1 on failure.
544 */
545int
546remote_connect(const char *host, const char *port, struct addrinfo hints)
547{
548	struct addrinfo *res, *res0;
549	int s, error, on = 1;
550
551	if ((error = getaddrinfo(host, port, &hints, &res)))
552		errx(1, "getaddrinfo: %s", gai_strerror(error));
553
554	res0 = res;
555	do {
556		if ((s = socket(res0->ai_family, res0->ai_socktype,
557		    res0->ai_protocol)) < 0)
558			continue;
559#ifdef IPSEC
560		if (ipsec_policy[0] != NULL)
561			add_ipsec_policy(s, ipsec_policy[0]);
562		if (ipsec_policy[1] != NULL)
563			add_ipsec_policy(s, ipsec_policy[1]);
564#endif
565
566		if (rdomain) {
567			if (setfib(rdomain) == -1)
568				err(1, "setfib");
569		}
570
571		/* Bind to a local port or source address if specified. */
572		if (sflag || pflag) {
573			struct addrinfo ahints, *ares;
574
575#ifdef SO_BINDANY
576			/* try SO_BINDANY, but don't insist */
577			setsockopt(s, SOL_SOCKET, SO_BINDANY, &on, sizeof(on));
578#endif
579			memset(&ahints, 0, sizeof(struct addrinfo));
580			ahints.ai_family = res0->ai_family;
581			ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
582			ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
583			ahints.ai_flags = AI_PASSIVE;
584			if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
585				errx(1, "getaddrinfo: %s", gai_strerror(error));
586
587			if (bind(s, (struct sockaddr *)ares->ai_addr,
588			    ares->ai_addrlen) < 0)
589				errx(1, "bind failed: %s", strerror(errno));
590			freeaddrinfo(ares);
591		}
592
593		set_common_sockopts(s);
594
595		if (connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
596			break;
597		else if (vflag)
598			warn("connect to %s port %s (%s) failed", host, port,
599			    uflag ? "udp" : "tcp");
600
601		close(s);
602		s = -1;
603	} while ((res0 = res0->ai_next) != NULL);
604
605	freeaddrinfo(res);
606
607	return (s);
608}
609
610/*
611 * local_listen()
612 * Returns a socket listening on a local port, binds to specified source
613 * address. Returns -1 on failure.
614 */
615int
616local_listen(char *host, char *port, struct addrinfo hints)
617{
618	struct addrinfo *res, *res0;
619	int s, ret, x = 1;
620	int error;
621
622	/* Allow nodename to be null. */
623	hints.ai_flags |= AI_PASSIVE;
624
625	/*
626	 * In the case of binding to a wildcard address
627	 * default to binding to an ipv4 address.
628	 */
629	if (host == NULL && hints.ai_family == AF_UNSPEC)
630		hints.ai_family = AF_INET;
631
632	if ((error = getaddrinfo(host, port, &hints, &res)))
633		errx(1, "getaddrinfo: %s", gai_strerror(error));
634
635	res0 = res;
636	do {
637		if ((s = socket(res0->ai_family, res0->ai_socktype,
638		    res0->ai_protocol)) < 0)
639			continue;
640
641		if (rdomain) {
642			if (setfib(rdomain) == -1)
643				err(1, "setfib");
644		}
645
646		ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
647		if (ret == -1)
648			err(1, NULL);
649#ifdef IPSEC
650		if (ipsec_policy[0] != NULL)
651			add_ipsec_policy(s, ipsec_policy[0]);
652		if (ipsec_policy[1] != NULL)
653			add_ipsec_policy(s, ipsec_policy[1]);
654#endif
655		if (FreeBSD_Oflag) {
656			if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
657			    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
658				err(1, "disable TCP options");
659		}
660
661		if (bind(s, (struct sockaddr *)res0->ai_addr,
662		    res0->ai_addrlen) == 0)
663			break;
664
665		close(s);
666		s = -1;
667	} while ((res0 = res0->ai_next) != NULL);
668
669	if (!uflag && s != -1) {
670		if (listen(s, 1) < 0)
671			err(1, "listen");
672	}
673
674	freeaddrinfo(res);
675
676	return (s);
677}
678
679/*
680 * readwrite()
681 * Loop that polls on the network file descriptor and stdin.
682 */
683void
684readwrite(int nfd)
685{
686	struct pollfd pfd[2];
687	unsigned char buf[8192];
688	int n, wfd = fileno(stdin);
689	int lfd = fileno(stdout);
690	int plen;
691
692	plen = jflag ? 8192 : 1024;
693
694	/* Setup Network FD */
695	pfd[0].fd = nfd;
696	pfd[0].events = POLLIN;
697
698	/* Set up STDIN FD. */
699	pfd[1].fd = wfd;
700	pfd[1].events = POLLIN;
701
702	while (pfd[0].fd != -1) {
703		if (iflag)
704			sleep(iflag);
705
706		if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
707			close(nfd);
708			err(1, "Polling Error");
709		}
710
711		if (n == 0)
712			return;
713
714		if (pfd[0].revents & POLLIN) {
715			if ((n = read(nfd, buf, plen)) < 0)
716				return;
717			else if (n == 0) {
718				shutdown(nfd, SHUT_RD);
719				pfd[0].fd = -1;
720				pfd[0].events = 0;
721			} else {
722				if (tflag)
723					atelnet(nfd, buf, n);
724				if (atomicio(vwrite, lfd, buf, n) != n)
725					return;
726			}
727		}
728
729		if (!dflag && pfd[1].revents & POLLIN) {
730			if ((n = read(wfd, buf, plen)) < 0 ||
731			    (oflag && n == 0)) {
732				return;
733			} else if (n == 0) {
734				shutdown(nfd, SHUT_WR);
735				pfd[1].fd = -1;
736				pfd[1].events = 0;
737			} else {
738				if (atomicio(vwrite, nfd, buf, n) != n)
739					return;
740			}
741		}
742	}
743}
744
745/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
746void
747atelnet(int nfd, unsigned char *buf, unsigned int size)
748{
749	unsigned char *p, *end;
750	unsigned char obuf[4];
751
752	end = buf + size;
753	obuf[0] = '\0';
754
755	for (p = buf; p < end; p++) {
756		if (*p != IAC)
757			break;
758
759		obuf[0] = IAC;
760		p++;
761		if ((*p == WILL) || (*p == WONT))
762			obuf[1] = DONT;
763		if ((*p == DO) || (*p == DONT))
764			obuf[1] = WONT;
765		if (obuf) {
766			p++;
767			obuf[2] = *p;
768			obuf[3] = '\0';
769			if (atomicio(vwrite, nfd, obuf, 3) != 3)
770				warn("Write Error!");
771			obuf[0] = '\0';
772		}
773	}
774}
775
776/*
777 * build_ports()
778 * Build an array or ports in portlist[], listing each port
779 * that we should try to connect to.
780 */
781void
782build_ports(char *p)
783{
784	const char *errstr;
785	char *n;
786	int hi, lo, cp;
787	int x = 0;
788
789	if ((n = strchr(p, '-')) != NULL) {
790		if (lflag)
791			errx(1, "Cannot use -l with multiple ports!");
792
793		*n = '\0';
794		n++;
795
796		/* Make sure the ports are in order: lowest->highest. */
797		hi = strtonum(n, 1, PORT_MAX, &errstr);
798		if (errstr)
799			errx(1, "port number %s: %s", errstr, n);
800		lo = strtonum(p, 1, PORT_MAX, &errstr);
801		if (errstr)
802			errx(1, "port number %s: %s", errstr, p);
803
804		if (lo > hi) {
805			cp = hi;
806			hi = lo;
807			lo = cp;
808		}
809
810		/* Load ports sequentially. */
811		for (cp = lo; cp <= hi; cp++) {
812			portlist[x] = calloc(1, PORT_MAX_LEN);
813			if (portlist[x] == NULL)
814				err(1, NULL);
815			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
816			x++;
817		}
818
819		/* Randomly swap ports. */
820		if (rflag) {
821			int y;
822			char *c;
823
824			for (x = 0; x <= (hi - lo); x++) {
825				y = (arc4random() & 0xFFFF) % (hi - lo);
826				c = portlist[x];
827				portlist[x] = portlist[y];
828				portlist[y] = c;
829			}
830		}
831	} else {
832		hi = strtonum(p, 1, PORT_MAX, &errstr);
833		if (errstr)
834			errx(1, "port number %s: %s", errstr, p);
835		portlist[0] = calloc(1, PORT_MAX_LEN);
836		if (portlist[0] == NULL)
837			err(1, NULL);
838		portlist[0] = p;
839	}
840}
841
842/*
843 * udptest()
844 * Do a few writes to see if the UDP port is there.
845 * XXX - Better way of doing this? Doesn't work for IPv6.
846 * Also fails after around 100 ports checked.
847 */
848int
849udptest(int s)
850{
851	int i, ret;
852
853	for (i = 0; i <= 3; i++) {
854		if (write(s, "X", 1) == 1)
855			ret = 1;
856		else
857			ret = -1;
858	}
859	return (ret);
860}
861
862void
863set_common_sockopts(int s)
864{
865	int x = 1;
866
867	if (Sflag) {
868		if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
869			&x, sizeof(x)) == -1)
870			err(1, NULL);
871	}
872	if (Dflag) {
873		if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
874			&x, sizeof(x)) == -1)
875			err(1, NULL);
876	}
877#ifdef SO_JUMBO
878	if (jflag) {
879		if (setsockopt(s, SOL_SOCKET, SO_JUMBO,
880			&x, sizeof(x)) == -1)
881			err(1, NULL);
882	}
883#endif
884	if (Tflag != -1) {
885		if (setsockopt(s, IPPROTO_IP, IP_TOS,
886		    &Tflag, sizeof(Tflag)) == -1)
887			err(1, "set IP ToS");
888	}
889	if (Iflag) {
890		if (setsockopt(s, SOL_SOCKET, SO_RCVBUF,
891		    &Iflag, sizeof(Iflag)) == -1)
892			err(1, "set TCP receive buffer size");
893	}
894	if (Oflag) {
895		if (setsockopt(s, SOL_SOCKET, SO_SNDBUF,
896		    &Oflag, sizeof(Oflag)) == -1)
897			err(1, "set TCP send buffer size");
898	}
899	if (FreeBSD_Oflag) {
900		if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
901		    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
902			err(1, "disable TCP options");
903	}
904}
905
906int
907parse_iptos(char *s)
908{
909	int tos = -1;
910
911	if (strcmp(s, "lowdelay") == 0)
912		return (IPTOS_LOWDELAY);
913	if (strcmp(s, "throughput") == 0)
914		return (IPTOS_THROUGHPUT);
915	if (strcmp(s, "reliability") == 0)
916		return (IPTOS_RELIABILITY);
917
918	if (sscanf(s, "0x%x", &tos) != 1 || tos < 0 || tos > 0xff)
919		errx(1, "invalid IP Type of Service");
920	return (tos);
921}
922
923void
924help(void)
925{
926	usage(0);
927	fprintf(stderr, "\tCommand Summary:\n\
928	\t-4		Use IPv4\n\
929	\t-6		Use IPv6\n\
930	\t-D		Enable the debug socket option\n\
931	\t-d		Detach from stdin\n");
932#ifdef IPSEC
933	fprintf(stderr, "\
934	\t-E		Use IPsec ESP\n\
935	\t-e policy	Use specified IPsec policy\n");
936#endif
937	fprintf(stderr, "\
938	\t-h		This help text\n\
939	\t-I length	TCP receive buffer length\n\
940	\t-i secs\t	Delay interval for lines sent, ports scanned\n\
941	\t-k		Keep inbound sockets open for multiple connects\n\
942	\t-l		Listen mode, for inbound connects\n\
943	\t-n		Suppress name/port resolutions\n\
944	\t--no-tcpopt	Disable TCP options\n\
945	\t-O length	TCP send buffer length\n\
946	\t-o		Terminate on EOF on input\n\
947	\t-P proxyuser\tUsername for proxy authentication\n\
948	\t-p port\t	Specify local port for remote connects\n\
949	\t-r		Randomize remote ports\n\
950	\t-S		Enable the TCP MD5 signature option\n\
951	\t-s addr\t	Local source address\n\
952	\t-T ToS\t	Set IP Type of Service\n\
953	\t-t		Answer TELNET negotiation\n\
954	\t-U		Use UNIX domain socket\n\
955	\t-u		UDP mode\n\
956	\t-V fib	Specify alternate routing table (FIB)\n\
957	\t-v		Verbose\n\
958	\t-w secs\t	Timeout for connects and final net reads\n\
959	\t-X proto	Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
960	\t-x addr[:port]\tSpecify proxy address and port\n\
961	\t-z		Zero-I/O mode [used for scanning]\n\
962	Port numbers can be individual or ranges: lo-hi [inclusive]\n");
963#ifdef IPSEC
964	fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n");
965#endif
966	exit(1);
967}
968
969#ifdef IPSEC
970void
971add_ipsec_policy(int s, char *policy)
972{
973	char *raw;
974	int e;
975
976	raw = ipsec_set_policy(policy, strlen(policy));
977	if (raw == NULL)
978		errx(1, "ipsec_set_policy `%s': %s", policy,
979		     ipsec_strerror());
980	e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw,
981			ipsec_get_policylen(raw));
982	if (e < 0)
983		err(1, "ipsec policy cannot be configured");
984	free(raw);
985	if (vflag)
986		fprintf(stderr, "ipsec policy configured: `%s'\n", policy);
987	return;
988}
989#endif /* IPSEC */
990
991void
992usage(int ret)
993{
994	fprintf(stderr,
995#ifdef IPSEC
996	    "usage: nc [-46DdEhklnorStUuvz] [-e policy] [-I length] [-i interval] [-O length]\n"
997#else
998	    "usage: nc [-46DdhklnorStUuvz] [-I length] [-i interval] [-O length]\n"
999#endif
1000	    "\t  [-P proxy_username] [-p source_port] [-s source_ip_address] [-T ToS]\n"
1001	    "\t  [-V fib] [-w timeout] [-X proxy_protocol]\n"
1002	    "\t  [-x proxy_address[:port]] [hostname] [port]\n");
1003	if (ret)
1004		exit(1);
1005}
1006