text: /*	$OpenBSD: syslog.c,v 1.28 2005/08/08 08:05:34 espie Exp $ */
  /*
   * Copyright (c) 1983, 1988, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <sys/uio.h>
  #include <syslog.h>
  #include <sys/un.h>
  #include <netdb.h>
  
  #include <errno.h>
  #include <fcntl.h>
  #include <paths.h>
  #include <stdio.h>
  #include <string.h>
  #include <time.h>
  #include <unistd.h>
  #include <stdarg.h>
  
  static struct syslog_data sdata = SYSLOG_DATA_INIT;
  
  extern char	*__progname;		/* Program name, from crt0. */
  
  static void	disconnectlog_r(struct syslog_data *);	/* disconnect from syslogd */
  static void	connectlog_r(struct syslog_data *);	/* (re)connect to syslogd */
  
  /*
   * syslog, vsyslog --
   *	print message on log file; output is intended for syslogd(8).
   */
  void
  syslog(int pri, const char *fmt, ...)
  {
  	va_list ap;
  
  	va_start(ap, fmt);
  	vsyslog(pri, fmt, ap);
  	va_end(ap);
  }
  
  void
  vsyslog(int pri, const char *fmt, va_list ap)
  {
  	vsyslog_r(pri, &sdata, fmt, ap);
  }
  
  void
  openlog(const char *ident, int logstat, int logfac)
  {
  	openlog_r(ident, logstat, logfac, &sdata);
  }
  
  void
  closelog(void)
  {
  	closelog_r(&sdata);
  }
  
  /* setlogmask -- set the log mask level */
  int
  setlogmask(int pmask)
  {
  	return setlogmask_r(pmask, &sdata);
  }
  
  /* Reentrant version of syslog, i.e. syslog_r() */
  
  void
  syslog_r(int pri, struct syslog_data *data, const char *fmt, ...)
  {
  	va_list ap;
  
  	va_start(ap, fmt);
  	vsyslog_r(pri, data, fmt, ap);
  	va_end(ap);
  }
  
  void
  vsyslog_r(int pri, struct syslog_data *data, const char *fmt, va_list ap)
  {
  	int cnt;
  	char ch, *p, *t;
  	time_t now;
  	int fd, saved_errno, error;
  #define	TBUF_LEN	2048
  #define	FMT_LEN		1024
  	char *stdp = NULL, tbuf[TBUF_LEN], fmt_cpy[FMT_LEN];
  	int tbuf_left, fmt_left, prlen;
  
  #define	INTERNALLOG	LOG_ERR|LOG_CONS|LOG_PERROR|LOG_PID
  	/* Check for invalid bits. */
  	if (pri & ~(LOG_PRIMASK|LOG_FACMASK)) {
  		if (data == &sdata) {
  			syslog(INTERNALLOG,
  			    "syslog: unknown facility/priority: %x", pri);
  		} else {
  			syslog_r(INTERNALLOG, data,
  			    "syslog_r: unknown facility/priority: %x", pri);
  		}
  		pri &= LOG_PRIMASK|LOG_FACMASK;
  	}
  
  	/* Check priority against setlogmask values. */
  	if (!(LOG_MASK(LOG_PRI(pri)) & data->log_mask))
  		return;
  
  	saved_errno = errno;
  
  	/* Set default facility if none specified. */
  	if ((pri & LOG_FACMASK) == 0)
  		pri |= data->log_fac;
  
  	/* If we have been called through syslog(), no need for reentrancy. */
  	if (data == &sdata)
  		(void)time(&now);
  
  	p = tbuf;
  	tbuf_left = TBUF_LEN;
  
  #define	DEC()	\
  	do {					\
  		if (prlen < 0)			\
  			prlen = 0;		\
  		if (prlen >= tbuf_left)		\
  			prlen = tbuf_left - 1;	\
  		p += prlen;			\
  		tbuf_left -= prlen;		\
  	} while (0)
  
  	prlen = snprintf(p, tbuf_left, "<%d>", pri);
  	DEC();
  
  	/* 
  	 * syslogd will expand time automagically for reentrant case, and
  	 * for normal case, just do like before
  	 */
  	if (data == &sdata) {
  		prlen = strftime(p, tbuf_left, "%h %e %T ", localtime(&now));
  		DEC();
  	}
  
  	if (data->log_stat & LOG_PERROR)
  		stdp = p;
  	if (data->log_tag == NULL)
  		data->log_tag = __progname;
  	if (data->log_tag != NULL) {
  		prlen = snprintf(p, tbuf_left, "%s", data->log_tag);
  		DEC();
  	}
  	if (data->log_stat & LOG_PID) {
  		prlen = snprintf(p, tbuf_left, "[%ld]", (long)getpid());
  		DEC();
  	}
  	if (data->log_tag != NULL) {
  		if (tbuf_left > 1) {
  			*p++ = ':';
  			tbuf_left--;
  		}
  		if (tbuf_left > 1) {
  			*p++ = ' ';
  			tbuf_left--;
  		}
  	}
  
  	/* strerror() is not reentrant */
  
  	for (t = fmt_cpy, fmt_left = FMT_LEN; (ch = *fmt); ++fmt) {
  		if (ch == '%' && fmt[1] == 'm') {
  			++fmt;
  			if (data == &sdata) {
  				prlen = snprintf(t, fmt_left, "%s",
  				    strerror(saved_errno)); 
  			} else {
  				prlen = snprintf(t, fmt_left, "Error %d",
  				    saved_errno); 
  			}
  			if (prlen < 0)
  				prlen = 0;
  			if (prlen >= fmt_left)
  				prlen = fmt_left - 1;
  			t += prlen;
  			fmt_left -= prlen;
  		} else if (ch == '%' && fmt[1] == '%' && fmt_left > 2) {
  			*t++ = '%';
  			*t++ = '%';
  			fmt++;
  			fmt_left -= 2;
  		} else {
  			if (fmt_left > 1) {
  				*t++ = ch;
  				fmt_left--;
  			}
  		}
  	}
  	*t = '\0';
  
  	prlen = vsnprintf(p, tbuf_left, fmt_cpy, ap);
  	DEC();
  	cnt = p - tbuf;
  
  	/* Output to stderr if requested. */
  	if (data->log_stat & LOG_PERROR) {
  		struct iovec iov[2];
  
  		iov[0].iov_base = stdp;
  		iov[0].iov_len = cnt - (stdp - tbuf);
  		iov[1].iov_base = "\n";
  		iov[1].iov_len = 1;
  		(void)writev(STDERR_FILENO, iov, 2);
  	}
  
  	/* Get connected, output the message to the local logger. */
  	if (!data->opened)
  		openlog_r(data->log_tag, data->log_stat, 0, data);
  	connectlog_r(data);
  
  	/*
  	 * If the send() failed, there are two likely scenarios:
  	 *  1) syslogd was restarted
  	 *  2) /dev/log is out of socket buffer space
  	 * We attempt to reconnect to /dev/log to take care of
  	 * case #1 and keep send()ing data to cover case #2
  	 * to give syslogd a chance to empty its socket buffer.
  	 */
  	if ((error = send(data->log_file, tbuf, cnt, 0)) < 0) {
  		if (errno != ENOBUFS) {
  			disconnectlog_r(data);
  			connectlog_r(data);
  		}
  		do {
  			usleep(1);
  			if ((error = send(data->log_file, tbuf, cnt, 0)) >= 0)
  				break;
  		} while (errno == ENOBUFS);
  	}
  
  	/*
  	 * Output the message to the console; try not to block
  	 * as a blocking console should not stop other processes.
  	 * Make sure the error reported is the one from the syslogd failure.
  	 */
  	if (error == -1 && (data->log_stat & LOG_CONS) &&
  	    (fd = open(_PATH_CONSOLE, O_WRONLY|O_NONBLOCK, 0)) >= 0) {
  		struct iovec iov[2];
  		
  		p = strchr(tbuf, '>') + 1;
  		iov[0].iov_base = p;
  		iov[0].iov_len = cnt - (p - tbuf);
  		iov[1].iov_base = "\r\n";
  		iov[1].iov_len = 2;
  		(void)writev(fd, iov, 2);
  		(void)close(fd);
  	}
  
  	if (data != &sdata)
  		closelog_r(data);
  }
  
  static void
  disconnectlog_r(struct syslog_data *data)
  {
  	/*
  	 * If the user closed the FD and opened another in the same slot,
  	 * that's their problem.  They should close it before calling on
  	 * system services.
  	 */
  	if (data->log_file != -1) {
  		close(data->log_file);
  		data->log_file = -1;
  	}
  	data->connected = 0;		/* retry connect */
  }
  
  static void
  connectlog_r(struct syslog_data *data)
  {
      union {
          struct sockaddr     syslogAddr;
          struct sockaddr_un  syslogAddrUn;
      } u;
  
  #define SyslogAddr   u.syslogAddrUn
  
  	if (data->log_file == -1) {
  		if ((data->log_file = socket(AF_UNIX, SOCK_DGRAM, 0)) == -1)
  			return;
  		(void)fcntl(data->log_file, F_SETFD, 1);
  	}
  	if (data->log_file != -1 && !data->connected) {
  		memset(&SyslogAddr, '\0', sizeof(SyslogAddr));
  #if 0
                  /* BIONIC: no sun_len field to fill on Linux */
  		SyslogAddr.sun_len = sizeof(SyslogAddr);
  #endif
  		SyslogAddr.sun_family = AF_UNIX;
  		strlcpy(SyslogAddr.sun_path, _PATH_LOG,
  		    sizeof(SyslogAddr.sun_path));
  		if (connect(data->log_file, &u.syslogAddr,
  		    sizeof(SyslogAddr)) == -1) {
  			(void)close(data->log_file);
  			data->log_file = -1;
  		} else
  			data->connected = 1;
  	}
  }
  
  void
  openlog_r(const char *ident, int logstat, int logfac, struct syslog_data *data)
  {
  	if (ident != NULL)
  		data->log_tag = ident;
  	data->log_stat = logstat;
  	if (logfac != 0 && (logfac &~ LOG_FACMASK) == 0)
  		data->log_fac = logfac;
  
  	if (data->log_stat & LOG_NDELAY)	/* open immediately */
  		connectlog_r(data);
  
  	data->opened = 1;	/* ident and facility has been set */
  }
  
  void
  closelog_r(struct syslog_data *data)
  {
  	(void)close(data->log_file);
  	data->log_file = -1;
  	data->connected = 0;
  	data->log_tag = NULL;
  }
  
  /* setlogmask -- set the log mask level */
  int
  setlogmask_r(int pmask, struct syslog_data *data)
  {
  	int omask;
  
  	omask = data->log_mask;
  	if (pmask != 0)
  		data->log_mask = pmask;
  	return (omask);
  }
  