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ttymsg.c revision 1.2 
      1 /*
      2  * Copyright (c) 1989 The Regents of the University of California.
      3  * 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
     35 /*static char sccsid[] = "from: @(#)ttymsg.c	5.8 (Berkeley) 7/1/91";*/
     36 static char rcsid[] = "$Id: ttymsg.c,v 1.2 1993/08/01 18:03:09 mycroft Exp $";
     37 #endif /* not lint */
     38 
     39 #include <sys/types.h>
     40 #include <sys/uio.h>
     41 #include <signal.h>
     42 #include <fcntl.h>
     43 #include <dirent.h>
     44 #include <errno.h>
     45 #include <paths.h>
     46 #include <unistd.h>
     47 #include <stdio.h>
     48 #include <string.h>
     49 #include <stdlib.h>
     50 
     51 /*
     52  * Display the contents of a uio structure on a terminal.  Used by wall(1)
     53  * and syslogd(8).  Forks and finishes in child if write would block, waiting
     54  * at most five minutes.  Returns pointer to error string on unexpected error;
     55  * string is not newline-terminated.  Various "normal" errors are ignored
     56  * (exclusive-use, lack of permission, etc.).
     57  */
     58 char *
     59 ttymsg(iov, iovcnt, line)
     60 	struct iovec *iov;
     61 	int iovcnt;
     62 	char *line;
     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 > 6)
     71 		return ("too many iov's (change code in wall/ttymsg.c)");
     72 	/*
     73 	 * open will fail on slip lines or exclusive-use lines
     74 	 * if not running as root; not an error.
     75 	 */
     76 	(void) strcpy(device + sizeof(_PATH_DEV) - 1, line);
     77 	if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
     78 		if (errno == EBUSY || errno == EACCES)
     79 			return (NULL);
     80 		(void) snprintf(errbuf, sizeof(errbuf),
     81 		    "%s: %s", device, strerror(errno));
     82 		return (errbuf);
     83 	}
     84 
     85 	for (cnt = left = 0; cnt < iovcnt; ++cnt)
     86 		left += iov[cnt].iov_len;
     87 
     88 	for (;;) {
     89 		wret = writev(fd, iov, iovcnt);
     90 		if (wret >= left)
     91 			break;
     92 		if (wret >= 0) {
     93 			left -= wret;
     94 			if (iov != localiov) {
     95 				bcopy(iov, localiov,
     96 				    iovcnt * sizeof(struct iovec));
     97 				iov = localiov;
     98 			}
     99 			for (cnt = 0; wret >= iov->iov_len; ++cnt) {
    100 				wret -= iov->iov_len;
    101 				++iov;
    102 				--iovcnt;
    103 			}
    104 			if (wret) {
    105 				iov->iov_base += wret;
    106 				iov->iov_len -= wret;
    107 			}
    108 			continue;
    109 		}
    110 		if (errno == EWOULDBLOCK) {
    111 			int cpid, off = 0;
    112 
    113 			if (forked) {
    114 				(void) close(fd);
    115 				_exit(1);
    116 			}
    117 			cpid = fork();
    118 			if (cpid < 0) {
    119 				(void) snprintf(errbuf, sizeof(errbuf),
    120 				    "fork: %s", strerror(errno));
    121 				(void) close(fd);
    122 				return (errbuf);
    123 			}
    124 			if (cpid) {	/* parent */
    125 				(void) close(fd);
    126 				return (NULL);
    127 			}
    128 			forked++;
    129 			/* wait at most 5 minutes */
    130 			(void) signal(SIGALRM, SIG_DFL);
    131 			(void) signal(SIGTERM, SIG_DFL); /* XXX */
    132 			(void) sigsetmask(0);
    133 			(void) alarm((u_int)(60 * 5));
    134 			(void) fcntl(fd, O_NONBLOCK, &off);
    135 			continue;
    136 		}
    137 		/*
    138 		 * We get ENODEV on a slip line if we're running as root,
    139 		 * and EIO if the line just went away.
    140 		 */
    141 		if (errno == ENODEV || errno == EIO)
    142 			break;
    143 		(void) close(fd);
    144 		if (forked)
    145 			_exit(1);
    146 		(void) snprintf(errbuf, sizeof(errbuf),
    147 		    "%s: %s", device, strerror(errno));
    148 		return (errbuf);
    149 	}
    150 
    151 	(void) close(fd);
    152 	if (forked)
    153 		_exit(0);
    154 	return (NULL);
    155 }
    156