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ttymsg.c revision 1.1.1.1 
      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[] = "@(#)ttymsg.c	5.8 (Berkeley) 7/1/91";
     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  * and syslogd(8).  Forks and finishes in child if write would block, waiting
     53  * at most five minutes.  Returns pointer to error string on unexpected error;
     54  * string is not newline-terminated.  Various "normal" errors are ignored
     55  * (exclusive-use, lack of permission, etc.).
     56  */
     57 char *
     58 ttymsg(iov, iovcnt, line)
     59 	struct iovec *iov;
     60 	int iovcnt;
     61 	char *line;
     62 {
     63 	static char device[MAXNAMLEN] = _PATH_DEV;
     64 	static char errbuf[1024];
     65 	register int cnt, fd, left, wret;
     66 	struct iovec localiov[6];
     67 	int forked = 0;
     68 
     69 	if (iovcnt > 6)
     70 		return ("too many iov's (change code in wall/ttymsg.c)");
     71 	/*
     72 	 * open will fail on slip lines or exclusive-use lines
     73 	 * if not running as root; not an error.
     74 	 */
     75 	(void) strcpy(device + sizeof(_PATH_DEV) - 1, line);
     76 	if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
     77 		if (errno == EBUSY || errno == EACCES)
     78 			return (NULL);
     79 		(void) snprintf(errbuf, sizeof(errbuf),
     80 		    "%s: %s", device, strerror(errno));
     81 		return (errbuf);
     82 	}
     83 
     84 	for (cnt = left = 0; cnt < iovcnt; ++cnt)
     85 		left += iov[cnt].iov_len;
     86 
     87 	for (;;) {
     88 		wret = writev(fd, iov, iovcnt);
     89 		if (wret >= left)
     90 			break;
     91 		if (wret >= 0) {
     92 			left -= wret;
     93 			if (iov != localiov) {
     94 				bcopy(iov, localiov,
     95 				    iovcnt * sizeof(struct iovec));
     96 				iov = localiov;
     97 			}
     98 			for (cnt = 0; wret >= iov->iov_len; ++cnt) {
     99 				wret -= iov->iov_len;
    100 				++iov;
    101 				--iovcnt;
    102 			}
    103 			if (wret) {
    104 				iov->iov_base += wret;
    105 				iov->iov_len -= wret;
    106 			}
    107 			continue;
    108 		}
    109 		if (errno == EWOULDBLOCK) {
    110 			int cpid, off = 0;
    111 
    112 			if (forked) {
    113 				(void) close(fd);
    114 				_exit(1);
    115 			}
    116 			cpid = fork();
    117 			if (cpid < 0) {
    118 				(void) snprintf(errbuf, sizeof(errbuf),
    119 				    "fork: %s", strerror(errno));
    120 				(void) close(fd);
    121 				return (errbuf);
    122 			}
    123 			if (cpid) {	/* parent */
    124 				(void) close(fd);
    125 				return (NULL);
    126 			}
    127 			forked++;
    128 			/* wait at most 5 minutes */
    129 			(void) signal(SIGALRM, SIG_DFL);
    130 			(void) signal(SIGTERM, SIG_DFL); /* XXX */
    131 			(void) sigsetmask(0);
    132 			(void) alarm((u_int)(60 * 5));
    133 			(void) fcntl(fd, O_NONBLOCK, &off);
    134 			continue;
    135 		}
    136 		/*
    137 		 * We get ENODEV on a slip line if we're running as root,
    138 		 * and EIO if the line just went away.
    139 		 */
    140 		if (errno == ENODEV || errno == EIO)
    141 			break;
    142 		(void) close(fd);
    143 		if (forked)
    144 			_exit(1);
    145 		(void) snprintf(errbuf, sizeof(errbuf),
    146 		    "%s: %s", device, strerror(errno));
    147 		return (errbuf);
    148 	}
    149 
    150 	(void) close(fd);
    151 	if (forked)
    152 		_exit(0);
    153 	return (NULL);
    154 }
    155