[exim.git] / src / src / log.c

/* $Cambridge: exim/src/src/log.c,v 1.2 2005/01/04 10:00:42 ph10 Exp $ */

/*************************************************
*     Exim - an Internet mail transport agent    *
*************************************************/

/* Copyright (c) University of Cambridge 1995 - 2005 */
/* See the file NOTICE for conditions of use and distribution. */

/* Functions for writing log files. The code for maintaining datestamped
log files was originally contributed by Tony Sheen. */


#include "exim.h"

#define LOG_NAME_SIZE 256
#define MAX_SYSLOG_LEN 870

#define LOG_MODE_FILE   1
#define LOG_MODE_SYSLOG 2

enum { lt_main, lt_reject, lt_panic, lt_process };

static uschar *log_names[] = { US"main", US"reject", US"panic", US"process" };



/*************************************************
*           Local static variables               *
*************************************************/

static uschar mainlog_name[LOG_NAME_SIZE];
static uschar rejectlog_name[LOG_NAME_SIZE];

static uschar *mainlog_datestamp = NULL;
static uschar *rejectlog_datestamp = NULL;

static int    mainlogfd = -1;
static int    rejectlogfd = -1;
static ino_t  mainlog_inode = 0;
static ino_t  rejectlog_inode = 0;

static uschar *panic_save_buffer = NULL;
static BOOL   panic_recurseflag = FALSE;

static BOOL   syslog_open = FALSE;
static BOOL   path_inspected = FALSE;
static int    logging_mode = LOG_MODE_FILE;
static uschar *file_path = US"";




/*************************************************
*              Write to syslog                   *
*************************************************/

/* The given string is split into sections according to length, or at embedded
newlines, and syslogged as a numbered sequence if it is overlong or if there is
more than one line.

Arguments:
  priority       syslog priority
  s              the string to be written

Returns:         nothing
*/

static void
write_syslog(int priority, uschar *s)
{
int len, pass;
int linecount = 0;

if (!syslog_timestamp) s += log_timezone? 26 : 20;

len = Ustrlen(s);

#ifndef NO_OPENLOG
if (!syslog_open)
  {
  #ifdef SYSLOG_LOG_PID
  openlog(CS syslog_processname, LOG_PID|LOG_CONS, syslog_facility);
  #else
  openlog(CS syslog_processname, LOG_CONS, syslog_facility);
  #endif
  syslog_open = TRUE;
  }
#endif

/* First do a scan through the message in order to determine how many lines
it is going to end up as. Then rescan to output it. */

for (pass = 0; pass < 2; pass++)
  {
  int i;
  int tlen;
  uschar *ss = s;
  for (i = 1, tlen = len; tlen > 0; i++)
    {
    int plen = tlen;
    uschar *nlptr = Ustrchr(ss, '\n');
    if (nlptr != NULL) plen = nlptr - ss;
    #ifndef SYSLOG_LONG_LINES
    if (plen > MAX_SYSLOG_LEN) plen = MAX_SYSLOG_LEN;
    #endif
    tlen -= plen;
    if (ss[plen] == '\n') tlen--;    /* chars left */

    if (pass == 0) linecount++; else
      {
      if (linecount == 1)
        syslog(priority, "%.*s", plen, ss);
      else
        syslog(priority, "[%d%c%d] %.*s", i,
          (ss[plen] == '\n' && tlen != 0)? '\\' : '/',
          linecount, plen, ss);
      }
    ss += plen;
    if (*ss == '\n') ss++;
    }
  }
}



/*************************************************
*             Die tidily                         *
*************************************************/

/* This is called when Exim is dying as a result of something going wrong in
the logging, or after a log call with LOG_PANIC_DIE set. Optionally write a
message to debug_file or a stderr file, if they exist. Then, if in the middle
of accepting a message, throw it away tidily; this will attempt to send an SMTP
response if appropriate. Otherwise, try to close down an outstanding SMTP call
tidily.

Arguments:
  s1         Error message to write to debug_file and/or stderr and syslog
  s2         Error message for any SMTP call that is in progress
Returns:     The function does not return
*/

static void
die(uschar *s1, uschar *s2)
{
if (s1 != NULL)
  {
  write_syslog(LOG_CRIT, s1);
  if (debug_file != NULL) debug_printf("%s\n", s1);
  if (log_stderr != NULL && log_stderr != debug_file)
    fprintf(log_stderr, "%s\n", s1);
  }
if (receive_call_bombout) receive_bomb_out(s2);  /* does not return */
if (smtp_input) smtp_closedown(s2);
exim_exit(EXIT_FAILURE);
}



/*************************************************
*             Create a log file                  *
*************************************************/

/* This function is called to create and open a log file. It may be called in a
subprocess when the original process is root.

Arguments:
  name         the file name

The file name has been build in a working buffer, so it is permissible to
overwrite it temporarily if it is necessary to create the directory.

Returns:       a file descriptor, or < 0 on failure (errno set)
*/

static int
create_log(uschar *name)
{
int fd = Uopen(name, O_CREAT|O_APPEND|O_WRONLY, LOG_MODE);

/* If creation failed, attempt to build a log directory in case that is the
problem. */

if (fd < 0 && errno == ENOENT)
  {
  BOOL created;
  uschar *lastslash = Ustrrchr(name, '/');
  *lastslash = 0;
  created = directory_make(NULL, name, LOG_DIRECTORY_MODE, FALSE);
  DEBUG(D_any) debug_printf("%s log directory %s\n",
    created? "created" : "failed to create", name);
  *lastslash = '/';
  if (created) fd = Uopen(name, O_CREAT|O_APPEND|O_WRONLY, LOG_MODE);
  }

return fd;
}




/*************************************************
*                Open a log file                 *
*************************************************/

/* This function opens one of a number of logs, which all (except for the
"process log") reside in the same directory, creating the directory if it does
not exist. This may be called recursively on failure, in order to open the
panic log.

The directory is in the static variable file_path. This is static so that it
the work of sorting out the path is done just once per Exim process.

Exim is normally configured to avoid running as root wherever possible, the log
files must be owned by the non-privileged exim user. To ensure this, first try
an open without O_CREAT - most of the time this will succeed. If it fails, try
to create the file; if running as root, this must be done in a subprocess to
avoid races.

Arguments:
  fd         where to return the resulting file descriptor
  type       lt_main, lt_reject, lt_panic, or lt_process

Returns:   nothing
*/

static void
open_log(int *fd, int type)
{
uid_t euid;
BOOL ok;
uschar buffer[LOG_NAME_SIZE];

/* Sort out the file name. This depends on the type of log we are opening. The
process "log" is written in the spool directory by default, but a path name can
be specified in the configuration. */

if (type == lt_process)
  {
  if (process_log_path == NULL)
    ok = string_format(buffer, sizeof(buffer), "%s/exim-process.info",
      spool_directory);
  else
    ok = string_format(buffer, sizeof(buffer), "%s", process_log_path);
  }

/* The names of the other three logs are controlled by file_path. The panic log
is written to the same directory as the main and reject logs, but its name does
not have a datestamp. The use of datestamps is indicated by %D in file_path.
When opening the panic log, if %D is present, we remove the datestamp from the
generated name; if it is at the start, remove a following non-alphameric
character as well; otherwise, remove a preceding non-alphameric character. This
is definitely kludgy, but it sort of does what people want, I hope. */

else
  {
  ok = string_format(buffer, sizeof(buffer), CS file_path, log_names[type]);

  /* Save the name of the mainlog for rollover processing. Without a datestamp,
  it gets statted to see if it has been cycled. With a datestamp, the datestamp
  will be compared. The static slot for saving it is the same size as buffer,
  and the text has been checked above to fit, so this use of strcpy() is OK. */

  if (type == lt_main)
    {
    Ustrcpy(mainlog_name, buffer);
    mainlog_datestamp = mainlog_name + string_datestamp_offset;
    }

  /* Ditto for the reject log */

  else if (type == lt_reject)
    {
    Ustrcpy(rejectlog_name, buffer);
    rejectlog_datestamp = rejectlog_name + string_datestamp_offset;
    }

  /* Remove any datestamp if this is the panic log. This is rare, so there's no
  need to optimize getting the datestamp length. We remove one non-alphanumeric
  char afterwards if at the start, otherwise one before. */

  else if (string_datestamp_offset >= 0)
    {
    uschar *from = buffer + string_datestamp_offset;
    uschar *to = from + Ustrlen(tod_stamp(tod_log_datestamp));
    if (from == buffer || from[-1] == '/')
      {
      if (!isalnum(*to)) to++;
      }
    else
      {
      if (!isalnum(from[-1])) from--;
      }

    /* This strcpy is ok, because we know that to is a substring of from. */

    Ustrcpy(from, to);
    }
  }

/* If the file name is too long, it is an unrecoverable disaster */

if (!ok)
  {
  die(US"exim: log file path too long: aborting",
      US"Logging failure; please try later");
  }

/* We now have the file name. Try to open an existing file. After a successful
open, arrange for automatic closure on exec(), and then return. */

*fd = Uopen(buffer, O_APPEND|O_WRONLY, LOG_MODE);

if (*fd >= 0)
  {
  fcntl(*fd, F_SETFD, fcntl(*fd, F_GETFD) | FD_CLOEXEC);
  return;
  }

/* Open was not successful: try creating the file. If this is a root process,
we must do the creating in a subprocess set to exim:exim in order to ensure
that the file is created with the right ownership. Otherwise, there can be a
race if an exim process is trying to write to the log at the same time. The use
of SIGUSR1 by the exiwhat utility can provoke a lot of simultaneous writing. */

euid = geteuid();

/* If we are already running as the Exim user (even if that user is root),
we can go ahead and create in the current process. */

if (euid == exim_uid) *fd = create_log(buffer);

/* Otherwise, if we are root, do the creation in an exim:exim subprocess. If we
are neither exim nor root, creation is not attempted. */

else if (euid == root_uid)
  {
  int status;
  pid_t pid = fork();

  /* In the subprocess, change uid/gid and do the creation. Return 0 from the
  subprocess on success. There doesn't seem much point in testing for setgid
  and setuid errors. */

  if (pid == 0)
    {
    (void)setgid(exim_gid);
    (void)setuid(exim_uid);
    _exit((create_log(buffer) < 0)? 1 : 0);
    }

  /* Wait for the subprocess. If it succeeded retry the open. */

  while (waitpid(pid, &status, 0) != pid);
  if (status == 0) *fd = Uopen(buffer, O_APPEND|O_WRONLY, LOG_MODE);
  }

/* If we now have an open file, set the close-on-exec flag and return. */

if (*fd >= 0)
  {
  fcntl(*fd, F_SETFD, fcntl(*fd, F_GETFD) | FD_CLOEXEC);
  return;
  }

/* Creation failed. There are some circumstances in which we get here when
the effective uid is not root or exim, which is the problem. (For example, a
non-setuid binary with log_arguments set, called in certain ways.) Rather than
just bombing out, force the log to stderr and carry on if stderr is available.
*/

if (euid != root_uid && euid != exim_uid && log_stderr != NULL)
  {
  *fd = fileno(log_stderr);
  return;
  }

/* Otherwise this is a disaster. This call is deliberately ONLY to the panic
log. If possible, save a copy of the original line that was being logged. If we
are recursing (can't open the panic log either), the pointer will already be
set. */

if (panic_save_buffer == NULL)
  {
  panic_save_buffer = (uschar *)malloc(LOG_BUFFER_SIZE);
  if (panic_save_buffer != NULL)
    memcpy(panic_save_buffer, log_buffer, LOG_BUFFER_SIZE);
  }

log_write(0, LOG_PANIC_DIE, "Cannot open %s log file \"%s\": %s: "
  "euid=%d egid=%d", log_names[type], buffer, strerror(errno), euid, getegid());
/* Never returns */
}



/*************************************************
*     Add configuration file info to log line    *
*************************************************/

/* This is put in a function because it's needed twice (once for debugging,
once for real).

Arguments:
  ptr         pointer to the end of the line we are building
  flags       log flags

Returns:      updated pointer
*/

static uschar *
log_config_info(uschar *ptr, int flags)
{
Ustrcpy(ptr, "Exim configuration error");
ptr += 24;

if ((flags & (LOG_CONFIG_FOR & ~LOG_CONFIG)) != 0)
  {
  Ustrcpy(ptr, " for ");
  return ptr + 5;
  }

if ((flags & (LOG_CONFIG_IN & ~LOG_CONFIG)) != 0)
  {
  sprintf(CS ptr, " in line %d of %s", config_lineno, config_filename);
  while (*ptr) ptr++;
  }

Ustrcpy(ptr, ":\n  ");
return ptr + 4;
}


/*************************************************
*           A write() operation failed           *
*************************************************/

/* This function is called when write() fails on anything other than the panic
log, which can happen if a disk gets full or a file gets too large or whatever.
We try to save the relevant message in the panic_save buffer before crashing
out.

Arguments:
  name      the name of the log being written
  length    the string length being written
  rc        the return value from write()

Returns:    does not return
*/

static void
log_write_failed(uschar *name, int length, int rc)
{
int save_errno = errno;

if (panic_save_buffer == NULL)
  {
  panic_save_buffer = (uschar *)malloc(LOG_BUFFER_SIZE);
  if (panic_save_buffer != NULL)
    memcpy(panic_save_buffer, log_buffer, LOG_BUFFER_SIZE);
  }

log_write(0, LOG_PANIC_DIE, "failed to write to %s: length=%d result=%d "
  "errno=%d (%s)", name, length, rc, save_errno,
  (save_errno == 0)? "write incomplete" : strerror(save_errno));
/* Never returns */
}



/*************************************************
*            Write message to log file           *
*************************************************/

/* Exim can be configured to log to local files, or use syslog, or both. This
is controlled by the setting of log_file_path. The following cases are
recognized:

  log_file_path = ""               write files in the spool/log directory
  log_file_path = "xxx"            write files in the xxx directory
  log_file_path = "syslog"         write to syslog
  log_file_path = "syslog : xxx"   write to syslog and to files (any order)

The one exception to this is messages containing LOG_PROCESS. These are always
written to exim-process.info in the spool directory. They aren't really log
messages in the same sense as the others.

The message always gets '\n' added on the end of it, since more than one
process may be writing to the log at once and we don't want intermingling to
happen in the middle of lines. To be absolutely sure of this we write the data
into a private buffer and then put it out in a single write() call.

The flags determine which log(s) the message is written to, or for syslogging,
which priority to use, and in the case of the panic log, whether the process
should die afterwards.

The variable really_exim is TRUE only when exim is running in privileged state
(i.e. not with a changed configuration or with testing options such as -brw).
If it is not, don't try to write to the log because permission will probably be
denied.

Avoid actually writing to the logs when exim is called with -bv or -bt to
test an address, but take other actions, such as panicing.

In Exim proper, the buffer for building the message is got at start-up, so that
nothing gets done if it can't be got. However, some functions that are also
used in utilities occasionally obey log_write calls in error situations, and it
is simplest to put a single malloc() here rather than put one in each utility.
Malloc is used directly because the store functions may call log_write().

If a message_id exists, we include it after the timestamp.

Arguments:
  selector  write to main log or LOG_INFO only if this value is zero, or if
              its bit is set in log_write_selector
  flags     each bit indicates some independent action:
              LOG_SENDER      add raw sender to the message
              LOG_RECIPIENTS  add raw recipients list to message
              LOG_CONFIG      add "Exim configuration error"
              LOG_CONFIG_FOR  add " for " instead of ":\n  "
              LOG_CONFIG_IN   add " in line x[ of file y]"
              LOG_MAIN        write to main log or syslog LOG_INFO
              LOG_REJECT      write to reject log or syslog LOG_NOTICE
              LOG_PANIC       write to panic log or syslog LOG_ALERT
              LOG_PANIC_DIE   write to panic log or LOG_ALERT and then crash
              LOG_PROCESS     write to process log (always a file)
  format    a printf() format
  ...       arguments for format

Returns:    nothing
*/

void
log_write(unsigned int selector, int flags, char *format, ...)
{
uschar *ptr;
int length, rc;
int paniclogfd;
va_list ap;

/* If panic_recurseflag is set, we have failed to open the panic log. This is
the ultimate disaster. First try to write the message to a debug file and/or
stderr and also to syslog. If panic_save_buffer is not NULL, it contains the
original log line that caused the problem. Afterwards, expire. */

if (panic_recurseflag)
  {
  uschar *extra = (panic_save_buffer == NULL)? US"" : panic_save_buffer;
  if (debug_file != NULL) debug_printf("%s%s", extra, log_buffer);
  if (log_stderr != NULL && log_stderr != debug_file)
    fprintf(log_stderr, "%s%s", extra, log_buffer);
  if (*extra != 0) write_syslog(LOG_CRIT, extra);
  write_syslog(LOG_CRIT, log_buffer);
  die(US"exim: could not open panic log - aborting: see message(s) above",
    US"Unexpected log failure, please try later");
  }

/* Ensure we have a buffer (see comment above); this should never be obeyed
when running Exim proper, only when running utilities. */

if (log_buffer == NULL)
  {
  log_buffer = (uschar *)malloc(LOG_BUFFER_SIZE);
  if (log_buffer == NULL)
    {
    fprintf(stderr, "exim: failed to get store for log buffer\n");
    exim_exit(EXIT_FAILURE);
    }
  }

/* If we haven't already done so, inspect the setting of log_file_path to
determine whether to log to files and/or to syslog. Bits in logging_mode
control this, and for file logging, the path must end up in file_path. This
variable must be in permanent store because it may be required again later in
the process. */

if (!path_inspected)
  {
  BOOL multiple = FALSE;
  int old_pool = store_pool;

  store_pool = POOL_PERM;

  /* If nothing has been set, don't waste effort... the default values for the
  statics are file_path="" and logging_mode = LOG_MODE_FILE. */

  if (log_file_path[0] != 0)
    {
    int sep = ':';              /* Fixed separator - outside use */
    uschar *s;
    uschar *ss = log_file_path;
    logging_mode = 0;
    while ((s = string_nextinlist(&ss,&sep,log_buffer,LOG_BUFFER_SIZE)) != NULL)
      {
      if (Ustrcmp(s, "syslog") == 0)
        logging_mode |= LOG_MODE_SYSLOG;
      else if ((logging_mode & LOG_MODE_FILE) != 0) multiple = TRUE;
      else
        {
        logging_mode |= LOG_MODE_FILE;

        /* If a non-empty path is given, use it */

        if (s[0] != 0)
          {
          file_path = string_copy(s);
          }

        /* If the path is empty, we want to use the first non-empty, non-
        syslog item in LOG_FILE_PATH, if there is one, since the value of
        log_file_path may have been set at runtime. If there is no such item,
        use the ultimate default in the spool directory. */

        else
          {
          uschar *t;
          uschar *tt = US LOG_FILE_PATH;
          while ((t = string_nextinlist(&tt,&sep,log_buffer,LOG_BUFFER_SIZE))
                != NULL)
            {
            if (Ustrcmp(t, "syslog") == 0 || t[0] == 0) continue;
            file_path = string_copy(t);
            break;
            }
          }  /* Empty item in log_file_path */
        }    /* First non-syslog item in log_file_path */
      }      /* Scan of log_file_path */
    }

  /* If no modes have been selected, it is a major disaster */

  if (logging_mode == 0)
    die(US"Neither syslog nor file logging set in log_file_path",
        US"Unexpected logging failure");

  /* Set up the ultimate default if necessary. Then revert to the old store
  pool, and record that we've sorted out the path. */

  if ((logging_mode & LOG_MODE_FILE) != 0 && file_path[0] == 0)
    file_path = string_sprintf("%s/log/%%slog", spool_directory);
  store_pool = old_pool;
  path_inspected = TRUE;

  /* If more than one file path was given, log a complaint. This recursive call
  should work since we have now set up the routing. */

  if (multiple)
    {
    log_write(0, LOG_MAIN|LOG_PANIC,
      "More than one path given in log_file_path: using %s", file_path);
    }
  }

/* If debugging, show all log entries, but don't show headers. Do it all
in one go so that it doesn't get split when multi-processing. */

DEBUG(D_any|D_v)
  {
  int i;
  ptr = log_buffer;

  Ustrcpy(ptr, "LOG:");
  ptr += 4;

  /* Show the options that were passed into the call. These are those whose
  flag values do not have the 0x80000000 bit in them. Note that this
  automatically exclude the "all" setting. */

  for (i = 0; i < log_options_count; i++)
    {
    unsigned int bit = log_options[i].bit;
    if ((bit & 0x80000000) != 0) continue;
    if ((selector & bit) != 0)
      {
      *ptr++ = ' ';
      Ustrcpy(ptr, log_options[i].name);
      while (*ptr) ptr++;
      }
    }

  sprintf(CS ptr, "%s%s%s%s%s\n  ",
    ((flags & LOG_MAIN) != 0)?    " MAIN"   : "",
    ((flags & LOG_PANIC) != 0)?   " PANIC"  : "",
    ((flags & LOG_PANIC_DIE) == LOG_PANIC_DIE)? " DIE" : "",
    ((flags & LOG_PROCESS) != 0)? " PROCESS": "",
    ((flags & LOG_REJECT) != 0)?  " REJECT" : "");

  while(*ptr) ptr++;
  if ((flags & LOG_CONFIG) != 0) ptr = log_config_info(ptr, flags);

  va_start(ap, format);
  if (!string_vformat(ptr, LOG_BUFFER_SIZE - (ptr-log_buffer)-1, format, ap))
    Ustrcpy(ptr, "**** log string overflowed log buffer ****");
  va_end(ap);

  while(*ptr) ptr++;
  Ustrcat(ptr, "\n");
  debug_printf("%s", log_buffer);
  }

/* If no log file is specified, we are in a mess. */

if ((flags & (LOG_MAIN|LOG_PANIC|LOG_REJECT|LOG_PROCESS)) == 0)
  log_write(0, LOG_MAIN|LOG_PANIC_DIE, "log_write called with no log "
    "flags set");

/* There are some weird circumstances in which logging is disabled. */

if (disable_logging)
  {
  DEBUG(D_any) debug_printf("log writing disabled\n");
  return;
  }

/* Create the main message in the log buffer, including the message
id except for the process log and when called by a utility. */

ptr = log_buffer;
if (really_exim && (flags & LOG_PROCESS) == 0 && message_id[0] != 0)
  sprintf(CS ptr, "%s %s ", tod_stamp(tod_log), message_id);
else sprintf(CS ptr, "%s ", tod_stamp(tod_log));

while(*ptr) ptr++;
if ((flags & LOG_CONFIG) != 0) ptr = log_config_info(ptr, flags);

va_start(ap, format);
if (!string_vformat(ptr, LOG_BUFFER_SIZE - (ptr-log_buffer)-1, format, ap))
  Ustrcpy(ptr, "**** log string overflowed log buffer ****\n");
while(*ptr) ptr++;
va_end(ap);

/* Add the raw, unrewritten, sender to the message if required. This is done
this way because it kind of fits with LOG_RECIPIENTS. */

if ((flags & LOG_SENDER) != 0 &&
    ptr < log_buffer + LOG_BUFFER_SIZE - 8 - Ustrlen(raw_sender))
  {
  sprintf(CS ptr, " from <%s>", raw_sender);
  while (*ptr) ptr++;
  }

/* Add list of recipients to the message if required; the raw list,
before rewriting, was saved in raw_recipients. There may be none, if an ACL
discarded them all. */

if ((flags & LOG_RECIPIENTS) != 0 && ptr < log_buffer + LOG_BUFFER_SIZE - 6 &&
     raw_recipients_count > 0)
  {
  int i;
  sprintf(CS ptr, " for");
  while (*ptr) ptr++;
  for (i = 0; i < raw_recipients_count; i++)
    {
    uschar *s = raw_recipients[i];
    if (log_buffer + LOG_BUFFER_SIZE - ptr < Ustrlen(s) + 3) break;
    sprintf(CS ptr, " %s", s);
    while (*ptr) ptr++;
    }
  }

sprintf(CS  ptr, "\n");
while(*ptr) ptr++;
length = ptr - log_buffer;

/* Handle loggable errors when running a utility, or when address testing.
Write to log_stderr unless debugging (when it will already have been written),
or unless there is no log_stderr (expn called from daemon, for example). */

if (!really_exim || log_testing_mode)
  {
  if (debug_selector == 0 && log_stderr != NULL &&
      (selector == 0 || (selector & log_write_selector) != 0))
    {
    if (host_checking)
      fprintf(log_stderr, "LOG: %s", CS(log_buffer + 20));  /* no timestamp */
    else
      fprintf(log_stderr, "%s", CS log_buffer);
    }
  if ((flags & LOG_PANIC_DIE) == LOG_PANIC_DIE) exim_exit(EXIT_FAILURE);
  return;
  }

/* Handle the main log. We know that either syslog or file logging (or both) is
set up. A real file gets left open during reception or delivery once it has
been opened, but we don't want to keep on writing to it for too long after it
has been renamed. Therefore, do a stat() and see if the inode has changed, and
if so, re-open. */

if ((flags & LOG_MAIN) != 0 &&
    (selector == 0 || (selector & log_write_selector) != 0))
  {
  if ((logging_mode & LOG_MODE_SYSLOG) != 0 &&
      (syslog_duplication || (flags & (LOG_REJECT|LOG_PANIC)) == 0))
    write_syslog(LOG_INFO, log_buffer);

  if ((logging_mode & LOG_MODE_FILE) != 0)
    {
    struct stat statbuf;

    /* Check for a change to the mainlog file name when datestamping is in
    operation. This happens at midnight, at which point we want to roll over
    the file. Closing it has the desired effect. */

    if (mainlog_datestamp != NULL)
      {
      uschar *nowstamp = tod_stamp(tod_log_datestamp);
      if (Ustrncmp (mainlog_datestamp, nowstamp, Ustrlen(nowstamp)) != 0)
        {
        close(mainlogfd);             /* Close the file */
        mainlogfd = -1;               /* Clear the file descriptor */
        mainlog_inode = 0;            /* Unset the inode */
        mainlog_datestamp = NULL;     /* Clear the datestamp */
        }
      }

    /* Otherwise, we want to check whether the file has been renamed by a
    cycling script. This could be "if else", but for safety's sake, leave it as
    "if" so that renaming the log starts a new file even when datestamping is
    happening. */

    if (mainlogfd >= 0)
      {
      if (Ustat(mainlog_name, &statbuf) < 0 || statbuf.st_ino != mainlog_inode)
        {
        close(mainlogfd);
        mainlogfd = -1;
        mainlog_inode = 0;
        }
      }

    /* If the log is closed, open it. Then write the line. */

    if (mainlogfd < 0)
      {
      open_log(&mainlogfd, lt_main);     /* No return on error */
      if (fstat(mainlogfd, &statbuf) >= 0) mainlog_inode = statbuf.st_ino;
      }

    /* Failing to write to the log is disastrous */

    if ((rc = write(mainlogfd, log_buffer, length)) != length)
      {
      log_write_failed(US"main log", length, rc);
      /* That function does not return */
      }
    }
  }

/* Handle the log for rejected messages. This can be globally disabled. If
there are any header lines (i.e. if the rejection is happening after the DATA
phase), log the recipients and the headers. */

if (write_rejectlog && (flags & LOG_REJECT) != 0)
  {
  header_line *h;

  if (header_list != NULL && (log_extra_selector & LX_rejected_header) != 0)
    {
    if (recipients_count > 0)
      {
      int i;

      /* List the sender */

      string_format(ptr, LOG_BUFFER_SIZE - (ptr-log_buffer),
        "Envelope-from: <%s>\n", sender_address);
      while (*ptr) ptr++;

      /* List up to 5 recipients */

      string_format(ptr, LOG_BUFFER_SIZE - (ptr-log_buffer),
        "Envelope-to: <%s>\n", recipients_list[0].address);
      while (*ptr) ptr++;

      for (i = 1; i < recipients_count && i < 5; i++)
        {
        string_format(ptr, LOG_BUFFER_SIZE - (ptr-log_buffer), "    <%s>\n",
          recipients_list[i].address);
        while (*ptr) ptr++;
        }

      if (i < recipients_count)
        {
        (void)string_format(ptr, LOG_BUFFER_SIZE - (ptr-log_buffer),
          "    ...\n");
        while (*ptr) ptr++;
        }
      }

    /* A header with a NULL text is an unfilled in Received: header */

    for (h = header_list; h != NULL; h = h->next)
      {
      BOOL fitted;
      if (h->text == NULL) continue;
      fitted = string_format(ptr, LOG_BUFFER_SIZE - (ptr-log_buffer),
        "%c %s", h->type, h->text);
      while(*ptr) ptr++;
      if (!fitted)         /* Buffer is full; truncate */
        {
        ptr -= 100;        /* For message and separator */
        if (ptr[-1] == '\n') ptr--;
        Ustrcpy(ptr, "\n*** truncated ***\n");
        while (*ptr) ptr++;
        break;
        }
      }

    length = ptr - log_buffer;
    }

  /* Write to syslog or to a log file */

  if ((logging_mode & LOG_MODE_SYSLOG) != 0 &&
      (syslog_duplication || (flags & LOG_PANIC) == 0))
    write_syslog(LOG_NOTICE, log_buffer);

  /* Check for a change to the rejectlog file name when datestamping is in
  operation. This happens at midnight, at which point we want to roll over
  the file. Closing it has the desired effect. */

  if ((logging_mode & LOG_MODE_FILE) != 0)
    {
    struct stat statbuf;

    if (rejectlog_datestamp != NULL)
      {
      uschar *nowstamp = tod_stamp(tod_log_datestamp);
      if (Ustrncmp (rejectlog_datestamp, nowstamp, Ustrlen(nowstamp)) != 0)
        {
        close(rejectlogfd);             /* Close the file */
        rejectlogfd = -1;               /* Clear the file descriptor */
        rejectlog_inode = 0;            /* Unset the inode */
        rejectlog_datestamp = NULL;     /* Clear the datestamp */
        }
      }

    /* Otherwise, we want to check whether the file has been renamed by a
    cycling script. This could be "if else", but for safety's sake, leave it as
    "if" so that renaming the log starts a new file even when datestamping is
    happening. */

    if (rejectlogfd >= 0)
      {
      if (Ustat(rejectlog_name, &statbuf) < 0 ||
           statbuf.st_ino != rejectlog_inode)
        {
        close(rejectlogfd);
        rejectlogfd = -1;
        rejectlog_inode = 0;
        }
      }

    /* Open the file if necessary, and write the data */

    if (rejectlogfd < 0)
      {
      open_log(&rejectlogfd, lt_reject); /* No return on error */
      if (fstat(rejectlogfd, &statbuf) >= 0) rejectlog_inode = statbuf.st_ino;
      }

    if ((rc = write(rejectlogfd, log_buffer, length)) != length)
      {
      log_write_failed(US"reject log", length, rc);
      /* That function does not return */
      }
    }
  }


/* Handle the process log file, where exim processes can be made to dump
details of what they are doing by sending them a USR1 signal. Note that
a message id is not automatically added above. This information is always
written to a file - never to syslog. */

if ((flags & LOG_PROCESS) != 0)
  {
  int processlogfd;
  open_log(&processlogfd, lt_process);  /* No return on error */
  if ((rc = write(processlogfd, log_buffer, length)) != length)
    {
    log_write_failed(US"process log", length, rc);
    /* That function does not return */
    }
  (void)close(processlogfd);
  }


/* Handle the panic log, which is not kept open like the others. If it fails to
open, there will be a recursive call to log_write(). We detect this above and
attempt to write to the system log as a last-ditch try at telling somebody. In
all cases, try to write to log_stderr. */

if ((flags & LOG_PANIC) != 0)
  {
  if (log_stderr != NULL && log_stderr != debug_file)
    fprintf(log_stderr, "%s", CS log_buffer);

  if ((logging_mode & LOG_MODE_SYSLOG) != 0)
    {
    write_syslog(LOG_ALERT, log_buffer);
    }

  /* If this panic logging was caused by a failure to open the main log,
  the original log line is in panic_save_buffer. Make an attempt to write it. */

  if ((logging_mode & LOG_MODE_FILE) != 0)
    {
    panic_recurseflag = TRUE;
    open_log(&paniclogfd, lt_panic);  /* Won't return on failure */
    panic_recurseflag = FALSE;

    if (panic_save_buffer != NULL)
      (void) write(paniclogfd, panic_save_buffer, Ustrlen(panic_save_buffer));

    if ((rc = write(paniclogfd, log_buffer, length)) != length)
      {
      int save_errno = errno;
      write_syslog(LOG_CRIT, log_buffer);
      sprintf(CS log_buffer, "write failed on panic log: length=%d result=%d "
        "errno=%d (%s)", length, rc, save_errno, strerror(save_errno));
      write_syslog(LOG_CRIT, log_buffer);
      flags |= LOG_PANIC_DIE;
      }

    close(paniclogfd);
    }

  /* Give up if the DIE flag is set */

  if ((flags & LOG_PANIC_DIE) != LOG_PANIC)
    die(NULL, US"Unexpected failure, please try later");
  }
}



/*************************************************
*            Close any open log files            *
*************************************************/

void
log_close_all(void)
{
if (mainlogfd >= 0)
  { close(mainlogfd); mainlogfd = -1; }
if (rejectlogfd >= 0)
  { close(rejectlogfd); rejectlogfd = -1; }
closelog();
syslog_open = FALSE;
}

/* End of log.c */