netcat.c revision 167964 
1/* $OpenBSD: netcat.c,v 1.89 2007/02/20 14:11:17 jmc 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 167964 2007-03-28 01:57:03Z 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/time.h>
40#include <sys/un.h>
41
42#include <netinet/in.h>
43#include <netinet/in_systm.h>
44#ifdef IPSEC
45#include <netinet6/ipsec.h>
46#endif
47#include <netinet/tcp.h>
48#include <netinet/ip.h>
49#include <arpa/telnet.h>
50
51#include <err.h>
52#include <errno.h>
53#include <netdb.h>
54#include <poll.h>
55#include <stdarg.h>
56#include <stdio.h>
57#include <stdlib.h>
58#include <string.h>
59#include <unistd.h>
60#include <fcntl.h>
61#include <limits.h>
62#include "atomicio.h"
63
64#ifndef SUN_LEN
65#define SUN_LEN(su) \
66	(sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path))
67#endif
68
69#define PORT_MAX	65535
70#define PORT_MAX_LEN	6
71
72/* Command Line Options */
73int	Eflag;					/* Use IPsec ESP */
74int	dflag;					/* detached, no stdin */
75unsigned int iflag;				/* Interval Flag */
76int	jflag;					/* use jumbo frames if we can */
77int	kflag;					/* More than one connect */
78int	lflag;					/* Bind to local port */
79int	nflag;					/* Don't do name look up */
80int	oflag;					/* Once only: stop on EOF */
81char   *Pflag;					/* Proxy username */
82char   *pflag;					/* Localport flag */
83int	rflag;					/* Random ports flag */
84char   *sflag;					/* Source Address */
85int	tflag;					/* Telnet Emulation */
86int	uflag;					/* UDP - Default to TCP */
87int	vflag;					/* Verbosity */
88int	xflag;					/* Socks proxy */
89int	zflag;					/* Port Scan Flag */
90int	Dflag;					/* sodebug */
91int	Sflag;					/* TCP MD5 signature option */
92int	Tflag = -1;				/* IP Type of Service */
93
94int timeout = -1;
95int family = AF_UNSPEC;
96char *portlist[PORT_MAX+1];
97
98void	atelnet(int, unsigned char *, unsigned int);
99void	build_ports(char *);
100void	help(void);
101int	local_listen(char *, char *, struct addrinfo);
102void	readwrite(int);
103int	remote_connect(const char *, const char *, struct addrinfo);
104int	socks_connect(const char *, const char *, struct addrinfo,
105	    const char *, const char *, struct addrinfo, int, const char *);
106int	udptest(int);
107int	unix_connect(char *);
108int	unix_listen(char *);
109void	set_common_sockopts(int);
110int	parse_iptos(char *);
111void	usage(int);
112
113#ifdef IPSEC
114void	add_ipsec_policy(int, char *);
115
116char	*ipsec_policy[2];
117#endif
118
119int
120main(int argc, char *argv[])
121{
122	int ch, s, ret, socksv, ipsec_count;
123	char *host, *uport;
124	struct addrinfo hints;
125	struct servent *sv;
126	socklen_t len;
127	struct sockaddr_storage cliaddr;
128	char *proxy;
129	const char *errstr, *proxyhost = "", *proxyport = NULL;
130	struct addrinfo proxyhints;
131
132	ret = 1;
133	ipsec_count = 0;
134	s = 0;
135	socksv = 5;
136	host = NULL;
137	uport = NULL;
138	sv = NULL;
139
140	while ((ch = getopt(argc, argv,
141	    "46e:DEdhi:jklnoP:p:rSs:tT:Uuvw:X:x:z")) != -1) {
142		switch (ch) {
143		case '4':
144			family = AF_INET;
145			break;
146		case '6':
147			family = AF_INET6;
148			break;
149		case 'U':
150			family = AF_UNIX;
151			break;
152		case 'X':
153			if (strcasecmp(optarg, "connect") == 0)
154				socksv = -1; /* HTTP proxy CONNECT */
155			else if (strcmp(optarg, "4") == 0)
156				socksv = 4; /* SOCKS v.4 */
157			else if (strcmp(optarg, "5") == 0)
158				socksv = 5; /* SOCKS v.5 */
159			else
160				errx(1, "unsupported proxy protocol");
161			break;
162		case 'd':
163			dflag = 1;
164			break;
165		case 'e':
166#ifdef IPSEC
167			ipsec_policy[ipsec_count++ % 2] = optarg;
168#else
169			errx(1, "IPsec support unavailable.");
170#endif
171			break;
172		case 'E':
173#ifdef IPSEC
174			ipsec_policy[0] = "in  ipsec esp/transport//require";
175			ipsec_policy[1] = "out ipsec esp/transport//require";
176#else
177			errx(1, "IPsec support unavailable.");
178#endif
179			break;
180		case 'h':
181			help();
182			break;
183		case 'i':
184			iflag = strtonum(optarg, 0, UINT_MAX, &errstr);
185			if (errstr)
186				errx(1, "interval %s: %s", errstr, optarg);
187			break;
188#ifdef SO_JUMBO
189		case 'j':
190			jflag = 1;
191			break;
192#endif
193		case 'k':
194			kflag = 1;
195			break;
196		case 'l':
197			lflag = 1;
198			break;
199		case 'n':
200			nflag = 1;
201			break;
202		case 'o':
203			oflag = 1;
204			break;
205		case 'P':
206			Pflag = optarg;
207			break;
208		case 'p':
209			pflag = optarg;
210			break;
211		case 'r':
212			rflag = 1;
213			break;
214		case 's':
215			sflag = optarg;
216			break;
217		case 't':
218			tflag = 1;
219			break;
220		case 'u':
221			uflag = 1;
222			break;
223		case 'v':
224			vflag = 1;
225			break;
226		case 'w':
227			timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
228			if (errstr)
229				errx(1, "timeout %s: %s", errstr, optarg);
230			timeout *= 1000;
231			break;
232		case 'x':
233			xflag = 1;
234			if ((proxy = strdup(optarg)) == NULL)
235				err(1, NULL);
236			break;
237		case 'z':
238			zflag = 1;
239			break;
240		case 'D':
241			Dflag = 1;
242			break;
243		case 'S':
244			Sflag = 1;
245			break;
246		case 'T':
247			Tflag = parse_iptos(optarg);
248			break;
249		default:
250			usage(1);
251		}
252	}
253	argc -= optind;
254	argv += optind;
255
256	/* Cruft to make sure options are clean, and used properly. */
257	if (argv[0] && !argv[1] && family == AF_UNIX) {
258		if (uflag)
259			errx(1, "cannot use -u and -U");
260		host = argv[0];
261		uport = NULL;
262	} else if (argv[0] && !argv[1]) {
263		if  (!lflag)
264			usage(1);
265		uport = argv[0];
266		host = NULL;
267	} else if (argv[0] && argv[1]) {
268		host = argv[0];
269		uport = argv[1];
270	} else
271		usage(1);
272
273	if (lflag && sflag)
274		errx(1, "cannot use -s and -l");
275	if (lflag && pflag)
276		errx(1, "cannot use -p and -l");
277	if (lflag && zflag)
278		errx(1, "cannot use -z and -l");
279	if (!lflag && kflag)
280		errx(1, "must use -l with -k");
281
282	/* Initialize addrinfo structure. */
283	if (family != AF_UNIX) {
284		memset(&hints, 0, sizeof(struct addrinfo));
285		hints.ai_family = family;
286		hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
287		hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
288		if (nflag)
289			hints.ai_flags |= AI_NUMERICHOST;
290	}
291
292	if (xflag) {
293		if (uflag)
294			errx(1, "no proxy support for UDP mode");
295
296		if (lflag)
297			errx(1, "no proxy support for listen");
298
299		if (family == AF_UNIX)
300			errx(1, "no proxy support for unix sockets");
301
302		/* XXX IPv6 transport to proxy would probably work */
303		if (family == AF_INET6)
304			errx(1, "no proxy support for IPv6");
305
306		if (sflag)
307			errx(1, "no proxy support for local source address");
308
309		proxyhost = strsep(&proxy, ":");
310		proxyport = proxy;
311
312		memset(&proxyhints, 0, sizeof(struct addrinfo));
313		proxyhints.ai_family = family;
314		proxyhints.ai_socktype = SOCK_STREAM;
315		proxyhints.ai_protocol = IPPROTO_TCP;
316		if (nflag)
317			proxyhints.ai_flags |= AI_NUMERICHOST;
318	}
319
320	if (lflag) {
321		int connfd;
322		ret = 0;
323
324		if (family == AF_UNIX)
325			s = unix_listen(host);
326
327		/* Allow only one connection at a time, but stay alive. */
328		for (;;) {
329			if (family != AF_UNIX)
330				s = local_listen(host, uport, hints);
331			if (s < 0)
332				err(1, NULL);
333			/*
334			 * For UDP, we will use recvfrom() initially
335			 * to wait for a caller, then use the regular
336			 * functions to talk to the caller.
337			 */
338			if (uflag) {
339				int rv, plen;
340				char buf[8192];
341				struct sockaddr_storage z;
342
343				len = sizeof(z);
344				plen = jflag ? 8192 : 1024;
345				rv = recvfrom(s, buf, plen, MSG_PEEK,
346				    (struct sockaddr *)&z, &len);
347				if (rv < 0)
348					err(1, "recvfrom");
349
350				rv = connect(s, (struct sockaddr *)&z, len);
351				if (rv < 0)
352					err(1, "connect");
353
354				connfd = s;
355			} else {
356				len = sizeof(cliaddr);
357				connfd = accept(s, (struct sockaddr *)&cliaddr,
358				    &len);
359			}
360
361			readwrite(connfd);
362			close(connfd);
363			if (family != AF_UNIX)
364				close(s);
365
366			if (!kflag)
367				break;
368		}
369	} else if (family == AF_UNIX) {
370		ret = 0;
371
372		if ((s = unix_connect(host)) > 0 && !zflag) {
373			readwrite(s);
374			close(s);
375		} else
376			ret = 1;
377
378		exit(ret);
379
380	} else {
381		int i = 0;
382
383		/* Construct the portlist[] array. */
384		build_ports(uport);
385
386		/* Cycle through portlist, connecting to each port. */
387		for (i = 0; portlist[i] != NULL; i++) {
388			if (s)
389				close(s);
390
391			if (xflag)
392				s = socks_connect(host, portlist[i], hints,
393				    proxyhost, proxyport, proxyhints, socksv,
394				    Pflag);
395			else
396				s = remote_connect(host, portlist[i], hints);
397
398			if (s < 0)
399				continue;
400
401			ret = 0;
402			if (vflag || zflag) {
403				/* For UDP, make sure we are connected. */
404				if (uflag) {
405					if (udptest(s) == -1) {
406						ret = 1;
407						continue;
408					}
409				}
410
411				/* Don't look up port if -n. */
412				if (nflag)
413					sv = NULL;
414				else {
415					sv = getservbyport(
416					    ntohs(atoi(portlist[i])),
417					    uflag ? "udp" : "tcp");
418				}
419
420				printf("Connection to %s %s port [%s/%s] succeeded!\n",
421				    host, portlist[i], uflag ? "udp" : "tcp",
422				    sv ? sv->s_name : "*");
423			}
424			if (!zflag)
425				readwrite(s);
426		}
427	}
428
429	if (s)
430		close(s);
431
432	exit(ret);
433}
434
435/*
436 * unix_connect()
437 * Returns a socket connected to a local unix socket. Returns -1 on failure.
438 */
439int
440unix_connect(char *path)
441{
442	struct sockaddr_un sun;
443	int s;
444
445	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
446		return (-1);
447	(void)fcntl(s, F_SETFD, 1);
448
449	memset(&sun, 0, sizeof(struct sockaddr_un));
450	sun.sun_family = AF_UNIX;
451
452	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
453	    sizeof(sun.sun_path)) {
454		close(s);
455		errno = ENAMETOOLONG;
456		return (-1);
457	}
458	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
459		close(s);
460		return (-1);
461	}
462	return (s);
463
464}
465
466/*
467 * unix_listen()
468 * Create a unix domain socket, and listen on it.
469 */
470int
471unix_listen(char *path)
472{
473	struct sockaddr_un sun;
474	int s;
475
476	/* Create unix domain socket. */
477	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
478		return (-1);
479
480	memset(&sun, 0, sizeof(struct sockaddr_un));
481	sun.sun_family = AF_UNIX;
482
483	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
484	    sizeof(sun.sun_path)) {
485		close(s);
486		errno = ENAMETOOLONG;
487		return (-1);
488	}
489
490	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
491		close(s);
492		return (-1);
493	}
494
495	if (listen(s, 5) < 0) {
496		close(s);
497		return (-1);
498	}
499	return (s);
500}
501
502/*
503 * remote_connect()
504 * Returns a socket connected to a remote host. Properly binds to a local
505 * port or source address if needed. Returns -1 on failure.
506 */
507int
508remote_connect(const char *host, const char *port, struct addrinfo hints)
509{
510	struct addrinfo *res, *res0;
511	int s, error;
512
513	if ((error = getaddrinfo(host, port, &hints, &res)))
514		errx(1, "getaddrinfo: %s", gai_strerror(error));
515
516	res0 = res;
517	do {
518		if ((s = socket(res0->ai_family, res0->ai_socktype,
519		    res0->ai_protocol)) < 0)
520			continue;
521#ifdef IPSEC
522		if (ipsec_policy[0] != NULL)
523			add_ipsec_policy(s, ipsec_policy[0]);
524		if (ipsec_policy[1] != NULL)
525			add_ipsec_policy(s, ipsec_policy[1]);
526#endif
527
528		/* Bind to a local port or source address if specified. */
529		if (sflag || pflag) {
530			struct addrinfo ahints, *ares;
531
532			memset(&ahints, 0, sizeof(struct addrinfo));
533			ahints.ai_family = res0->ai_family;
534			ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
535			ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
536			ahints.ai_flags = AI_PASSIVE;
537			if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
538				errx(1, "getaddrinfo: %s", gai_strerror(error));
539
540			if (bind(s, (struct sockaddr *)ares->ai_addr,
541			    ares->ai_addrlen) < 0)
542				errx(1, "bind failed: %s", strerror(errno));
543			freeaddrinfo(ares);
544		}
545
546		set_common_sockopts(s);
547
548		if (connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
549			break;
550		else if (vflag)
551			warn("connect to %s port %s (%s) failed", host, port,
552			    uflag ? "udp" : "tcp");
553
554		close(s);
555		s = -1;
556	} while ((res0 = res0->ai_next) != NULL);
557
558	freeaddrinfo(res);
559
560	return (s);
561}
562
563/*
564 * local_listen()
565 * Returns a socket listening on a local port, binds to specified source
566 * address. Returns -1 on failure.
567 */
568int
569local_listen(char *host, char *port, struct addrinfo hints)
570{
571	struct addrinfo *res, *res0;
572	int s, ret, x = 1;
573	int error;
574
575	/* Allow nodename to be null. */
576	hints.ai_flags |= AI_PASSIVE;
577
578	/*
579	 * In the case of binding to a wildcard address
580	 * default to binding to an ipv4 address.
581	 */
582	if (host == NULL && hints.ai_family == AF_UNSPEC)
583		hints.ai_family = AF_INET;
584
585	if ((error = getaddrinfo(host, port, &hints, &res)))
586		errx(1, "getaddrinfo: %s", gai_strerror(error));
587
588	res0 = res;
589	do {
590		if ((s = socket(res0->ai_family, res0->ai_socktype,
591		    res0->ai_protocol)) < 0)
592			continue;
593
594		ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
595		if (ret == -1)
596			err(1, NULL);
597#ifdef IPSEC
598		if (ipsec_policy[0] != NULL)
599			add_ipsec_policy(s, ipsec_policy[0]);
600		if (ipsec_policy[1] != NULL)
601			add_ipsec_policy(s, ipsec_policy[1]);
602#endif
603
604		if (bind(s, (struct sockaddr *)res0->ai_addr,
605		    res0->ai_addrlen) == 0)
606			break;
607
608		close(s);
609		s = -1;
610	} while ((res0 = res0->ai_next) != NULL);
611
612	if (!uflag && s != -1) {
613		if (listen(s, 1) < 0)
614			err(1, "listen");
615	}
616
617	freeaddrinfo(res);
618
619	return (s);
620}
621
622/*
623 * readwrite()
624 * Loop that polls on the network file descriptor and stdin.
625 */
626void
627readwrite(int nfd)
628{
629	struct pollfd pfd[2];
630	unsigned char buf[8192];
631	int n, wfd = fileno(stdin);
632	int lfd = fileno(stdout);
633	int plen;
634
635	plen = jflag ? 8192 : 1024;
636
637	/* Setup Network FD */
638	pfd[0].fd = nfd;
639	pfd[0].events = POLLIN;
640
641	/* Set up STDIN FD. */
642	pfd[1].fd = wfd;
643	pfd[1].events = POLLIN;
644
645	while (pfd[0].fd != -1) {
646		if (iflag)
647			sleep(iflag);
648
649		if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
650			close(nfd);
651			err(1, "Polling Error");
652		}
653
654		if (n == 0)
655			return;
656
657		if (pfd[0].revents & POLLIN) {
658			if ((n = read(nfd, buf, plen)) < 0)
659				return;
660			else if (n == 0) {
661				shutdown(nfd, SHUT_RD);
662				pfd[0].fd = -1;
663				pfd[0].events = 0;
664			} else {
665				if (tflag)
666					atelnet(nfd, buf, n);
667				if (atomicio(vwrite, lfd, buf, n) != n)
668					return;
669			}
670		}
671
672		if (!dflag && pfd[1].revents & POLLIN) {
673			if ((n = read(wfd, buf, plen)) < 0 ||
674			    (oflag && n == 0)) {
675				return;
676			} else if (n == 0) {
677				shutdown(nfd, SHUT_WR);
678				pfd[1].fd = -1;
679				pfd[1].events = 0;
680			} else {
681				if (atomicio(vwrite, nfd, buf, n) != n)
682					return;
683			}
684		}
685	}
686}
687
688/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
689void
690atelnet(int nfd, unsigned char *buf, unsigned int size)
691{
692	unsigned char *p, *end;
693	unsigned char obuf[4];
694
695	end = buf + size;
696	obuf[0] = '\0';
697
698	for (p = buf; p < end; p++) {
699		if (*p != IAC)
700			break;
701
702		obuf[0] = IAC;
703		p++;
704		if ((*p == WILL) || (*p == WONT))
705			obuf[1] = DONT;
706		if ((*p == DO) || (*p == DONT))
707			obuf[1] = WONT;
708		if (obuf) {
709			p++;
710			obuf[2] = *p;
711			obuf[3] = '\0';
712			if (atomicio(vwrite, nfd, obuf, 3) != 3)
713				warn("Write Error!");
714			obuf[0] = '\0';
715		}
716	}
717}
718
719/*
720 * build_ports()
721 * Build an array or ports in portlist[], listing each port
722 * that we should try to connect to.
723 */
724void
725build_ports(char *p)
726{
727	const char *errstr;
728	char *n;
729	int hi, lo, cp;
730	int x = 0;
731
732	if ((n = strchr(p, '-')) != NULL) {
733		if (lflag)
734			errx(1, "Cannot use -l with multiple ports!");
735
736		*n = '\0';
737		n++;
738
739		/* Make sure the ports are in order: lowest->highest. */
740		hi = strtonum(n, 1, PORT_MAX, &errstr);
741		if (errstr)
742			errx(1, "port number %s: %s", errstr, n);
743		lo = strtonum(p, 1, PORT_MAX, &errstr);
744		if (errstr)
745			errx(1, "port number %s: %s", errstr, p);
746
747		if (lo > hi) {
748			cp = hi;
749			hi = lo;
750			lo = cp;
751		}
752
753		/* Load ports sequentially. */
754		for (cp = lo; cp <= hi; cp++) {
755			portlist[x] = calloc(1, PORT_MAX_LEN);
756			if (portlist[x] == NULL)
757				err(1, NULL);
758			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
759			x++;
760		}
761
762		/* Randomly swap ports. */
763		if (rflag) {
764			int y;
765			char *c;
766
767			for (x = 0; x <= (hi - lo); x++) {
768				y = (arc4random() & 0xFFFF) % (hi - lo);
769				c = portlist[x];
770				portlist[x] = portlist[y];
771				portlist[y] = c;
772			}
773		}
774	} else {
775		hi = strtonum(p, 1, PORT_MAX, &errstr);
776		if (errstr)
777			errx(1, "port number %s: %s", errstr, p);
778		portlist[0] = calloc(1, PORT_MAX_LEN);
779		if (portlist[0] == NULL)
780			err(1, NULL);
781		portlist[0] = p;
782	}
783}
784
785/*
786 * udptest()
787 * Do a few writes to see if the UDP port is there.
788 * XXX - Better way of doing this? Doesn't work for IPv6.
789 * Also fails after around 100 ports checked.
790 */
791int
792udptest(int s)
793{
794	int i, ret;
795
796	for (i = 0; i <= 3; i++) {
797		if (write(s, "X", 1) == 1)
798			ret = 1;
799		else
800			ret = -1;
801	}
802	return (ret);
803}
804
805void
806set_common_sockopts(int s)
807{
808	int x = 1;
809
810	if (Sflag) {
811		if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
812			&x, sizeof(x)) == -1)
813			err(1, NULL);
814	}
815	if (Dflag) {
816		if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
817			&x, sizeof(x)) == -1)
818			err(1, NULL);
819	}
820#ifdef SO_JUMBO
821	if (jflag) {
822		if (setsockopt(s, SOL_SOCKET, SO_JUMBO,
823			&x, sizeof(x)) == -1)
824			err(1, NULL);
825	}
826#endif
827	if (Tflag != -1) {
828		if (setsockopt(s, IPPROTO_IP, IP_TOS,
829		    &Tflag, sizeof(Tflag)) == -1)
830			err(1, "set IP ToS");
831	}
832}
833
834int
835parse_iptos(char *s)
836{
837	int tos = -1;
838
839	if (strcmp(s, "lowdelay") == 0)
840		return (IPTOS_LOWDELAY);
841	if (strcmp(s, "throughput") == 0)
842		return (IPTOS_THROUGHPUT);
843	if (strcmp(s, "reliability") == 0)
844		return (IPTOS_RELIABILITY);
845
846	if (sscanf(s, "0x%x", &tos) != 1 || tos < 0 || tos > 0xff)
847		errx(1, "invalid IP Type of Service");
848	return (tos);
849}
850
851void
852help(void)
853{
854	usage(0);
855	fprintf(stderr, "\tCommand Summary:\n\
856	\t-4		Use IPv4\n\
857	\t-6            Use IPv6\n");
858#ifdef IPSEC
859	fprintf(stderr, "\
860	\t-e policy     Use specified IPsec policy\n\
861	\t-E            Use IPsec ESP\n");
862#endif
863	fprintf(stderr, "\
864	\t-D		Enable the debug socket option\n\
865	\t-d		Detach from stdin\n\
866	\t-h		This help text\n\
867	\t-i secs\t	Delay interval for lines sent, ports scanned\n\
868	\t-k		Keep inbound sockets open for multiple connects\n\
869	\t-l		Listen mode, for inbound connects\n\
870	\t-n		Suppress name/port resolutions\n\
871	\t-P proxyuser\tUsername for proxy authentication\n\
872	\t-p port\t	Specify local port for remote connects\n\
873	\t-r		Randomize remote ports\n\
874	\t-S		Enable the TCP MD5 signature option\n\
875	\t-s addr\t	Local source address\n\
876	\t-T ToS\t	Set IP Type of Service\n\
877	\t-t		Answer TELNET negotiation\n\
878	\t-U		Use UNIX domain socket\n\
879	\t-u		UDP mode\n\
880	\t-v		Verbose\n\
881	\t-w secs\t	Timeout for connects and final net reads\n\
882	\t-X proto	Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
883	\t-x addr[:port]\tSpecify proxy address and port\n\
884	\t-z		Zero-I/O mode [used for scanning]\n\
885	Port numbers can be individual or ranges: lo-hi [inclusive]\n");
886#ifdef IPSEC
887	fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n");
888#endif
889	exit(1);
890}
891
892#ifdef IPSEC
893void
894add_ipsec_policy(int s, char *policy)
895{
896	char *raw;
897	int e;
898
899	raw = ipsec_set_policy(policy, strlen(policy));
900	if (raw == NULL)
901		errx(1, "ipsec_set_policy `%s': %s", policy,
902		     ipsec_strerror());
903	e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw,
904			ipsec_get_policylen(raw));
905	if (e < 0)
906		err(1, "ipsec policy cannot be configured");
907	free(raw);
908	if (vflag)
909		fprintf(stderr, "ipsec policy configured: `%s'\n", policy);
910	return;
911}
912#endif /* IPSEC */
913
914void
915usage(int ret)
916{
917#ifdef IPSEC
918	fprintf(stderr, "usage: nc [-46DEdhklnrStUuvz] [-e policy] [-i interval] [-P proxy_username] [-p source_port]\n");
919#else
920	fprintf(stderr, "usage: nc [-46DdhklnrStUuvz] [-i interval] [-P proxy_username] [-p source_port]\n");
921#endif
922	fprintf(stderr, "\t  [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_protocol]\n");
923	fprintf(stderr, "\t  [-x proxy_address[:port]] [hostname] [port[s]]\n");
924	if (ret)
925		exit(1);
926}
927