ttymsg.c revision 1590 
1/*
2 * Copyright (c) 1989, 1993
3 *	The Regents of the University of California.  All rights reserved.
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 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#ifndef lint
35static char sccsid[] = "@(#)ttymsg.c	8.2 (Berkeley) 11/16/93";
36#endif /* not lint */
37
38#include <sys/types.h>
39#include <sys/uio.h>
40#include <signal.h>
41#include <fcntl.h>
42#include <dirent.h>
43#include <errno.h>
44#include <paths.h>
45#include <unistd.h>
46#include <stdio.h>
47#include <string.h>
48#include <stdlib.h>
49
50/*
51 * Display the contents of a uio structure on a terminal.  Used by wall(1),
52 * syslogd(8), and talkd(8).  Forks and finishes in child if write would block,
53 * waiting up to tmout seconds.  Returns pointer to error string on unexpected
54 * error; string is not newline-terminated.  Various "normal" errors are
55 * ignored (exclusive-use, lack of permission, etc.).
56 */
57char *
58ttymsg(iov, iovcnt, line, tmout)
59	struct iovec *iov;
60	int iovcnt;
61	char *line;
62	int tmout;
63{
64	static char device[MAXNAMLEN] = _PATH_DEV;
65	static char errbuf[1024];
66	register int cnt, fd, left, wret;
67	struct iovec localiov[6];
68	int forked = 0;
69
70	if (iovcnt > sizeof(localiov) / sizeof(localiov[0]))
71		return ("too many iov's (change code in wall/ttymsg.c)");
72
73	(void) strcpy(device + sizeof(_PATH_DEV) - 1, line);
74	if (strchr(device + sizeof(_PATH_DEV) - 1, '/')) {
75		/* A slash is an attempt to break security... */
76		(void) snprintf(errbuf, sizeof(errbuf), "'/' in \"%s\"",
77		    device);
78		return (errbuf);
79	}
80
81	/*
82	 * open will fail on slip lines or exclusive-use lines
83	 * if not running as root; not an error.
84	 */
85	if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
86		if (errno == EBUSY || errno == EACCES)
87			return (NULL);
88		(void) snprintf(errbuf, sizeof(errbuf),
89		    "%s: %s", device, strerror(errno));
90		return (errbuf);
91	}
92
93	for (cnt = left = 0; cnt < iovcnt; ++cnt)
94		left += iov[cnt].iov_len;
95
96	for (;;) {
97		wret = writev(fd, iov, iovcnt);
98		if (wret >= left)
99			break;
100		if (wret >= 0) {
101			left -= wret;
102			if (iov != localiov) {
103				bcopy(iov, localiov,
104				    iovcnt * sizeof(struct iovec));
105				iov = localiov;
106			}
107			for (cnt = 0; wret >= iov->iov_len; ++cnt) {
108				wret -= iov->iov_len;
109				++iov;
110				--iovcnt;
111			}
112			if (wret) {
113				iov->iov_base += wret;
114				iov->iov_len -= wret;
115			}
116			continue;
117		}
118		if (errno == EWOULDBLOCK) {
119			int cpid, off = 0;
120
121			if (forked) {
122				(void) close(fd);
123				_exit(1);
124			}
125			cpid = fork();
126			if (cpid < 0) {
127				(void) snprintf(errbuf, sizeof(errbuf),
128				    "fork: %s", strerror(errno));
129				(void) close(fd);
130				return (errbuf);
131			}
132			if (cpid) {	/* parent */
133				(void) close(fd);
134				return (NULL);
135			}
136			forked++;
137			/* wait at most tmout seconds */
138			(void) signal(SIGALRM, SIG_DFL);
139			(void) signal(SIGTERM, SIG_DFL); /* XXX */
140			(void) sigsetmask(0);
141			(void) alarm((u_int)tmout);
142			(void) fcntl(fd, O_NONBLOCK, &off);
143			continue;
144		}
145		/*
146		 * We get ENODEV on a slip line if we're running as root,
147		 * and EIO if the line just went away.
148		 */
149		if (errno == ENODEV || errno == EIO)
150			break;
151		(void) close(fd);
152		if (forked)
153			_exit(1);
154		(void) snprintf(errbuf, sizeof(errbuf),
155		    "%s: %s", device, strerror(errno));
156		return (errbuf);
157	}
158
159	(void) close(fd);
160	if (forked)
161		_exit(0);
162	return (NULL);
163}
164