# <@LICENSE>
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to you under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at:
# 
#     http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# </@LICENSE>

=head1 NAME

Mail::SpamAssassin::Logger::Syslog - log to syslog

=head1 SYNOPSIS

  loadplugin     Mail::SpamAssassin::Logger::Syslog

=head1 DESCRIPTION

=cut

package Mail::SpamAssassin::Logger::Syslog;

use strict;
use warnings;
use bytes;
use re 'taint';
use Mail::SpamAssassin::Logger;
use Sys::Syslog qw(:DEFAULT setlogsock);
use POSIX qw(:sys_wait_h);
use POSIX qw(setsid sigprocmask);

use vars qw(@ISA);
@ISA = ();

sub new {
  my $class = shift;

  $class = ref($class) || $class;
  my $self = { };
  bless ($self, $class);

  # initialization
  $self->{already_done_failure_warning} = 0;
  $self->{disabled} = 0;
  $self->{consecutive_failures} = 0;
  $self->{failure_threshold} = 10;

  # parameters
  my %params = @_;
  $self->{ident} = $params{ident} || 'spamassassin';
  $self->{log_socket} = $params{socket};
  $self->{log_facility} = $params{facility};

  if (! $self->init()) {
    die "logger: syslog initialization failed\n";
  }

  return($self);
}

# logging via syslog is requested
sub init {
  my ($self) = @_;

  my $log_socket = $self->{log_socket};

  dbg("logger: trying to connect to syslog/$log_socket ...\n");
  my $eval_stat;
  eval {
    defined(setlogsock($log_socket))
      or die "setlogsock($log_socket) failed: $!";
    dbg("logger: opening syslog with $log_socket socket");
    # the next call is required to actually open the socket
    openlog($self->{ident}, 'cons,pid,ndelay', $self->{log_facility});
    1;
  } or do {
    $eval_stat = $@ ne '' ? $@ : "errno=$!";  chomp $eval_stat;
    dbg("logger: connection to syslog/$log_socket failed: $eval_stat");
  };

  # Solaris sometimes doesn't support UNIX-domain syslog sockets apparently;
  # the same is true for perl 5.6.0 build on an early version of Red Hat 7!
  # In these cases we try it with INET instead.
  if (defined($eval_stat) && $log_socket ne 'inet') {
    dbg("logger: trying to connect to syslog/inet...");
    undef $eval_stat;
    eval {
      defined(setlogsock('inet')) or die "setlogsock('inet') failed: $!";
      dbg("logger: opening syslog using inet socket");
      openlog($self->{ident}, 'cons,pid,ndelay', $self->{log_facility});
      1;
    } or do {
      $eval_stat = $@ ne '' ? $@ : "errno=$!";  chomp $eval_stat;
      dbg("logger: connection to syslog/inet failed: $eval_stat");
    };
  }

  # we failed!
  if (defined $eval_stat) {
    return 0;
  }
  else {
    dbg("logger: successfully connected to syslog/$log_socket");
    return 1;
  }
}

sub log_message {
  my ($self, $level, $msg) = @_;

  return if $self->{disabled};

  # map level names
  # info is already info
  $level = 'debug' if $level eq 'dbg';
  $level = 'warning' if $level eq 'warn';
  $level = 'err' if $level eq 'error';

  # install a new handler for SIGPIPE -- this signal has been
  # found to occur with syslog-ng after syslog-ng restarts.
  local $SIG{'PIPE'} = sub {
    $self->{SIGPIPE_RECEIVED}++;
    # force a log-close.   trap possible die() calls
    eval { closelog(); };
  };

  # important: do not call syslog() from the SIGCHLD handler
  # child_handler().   otherwise we can get into a loop if syslog()
  # forks a process -- as it does in syslog-ng apparently! (bug 3625)
  $Mail::SpamAssassin::Logger::LOG_SA{INHIBIT_LOGGING_IN_SIGCHLD_HANDLER} = 1;
  my $eval_stat;
  eval {
    syslog($level, "%s", $msg); 1;
  } or do {
    $eval_stat = $@ ne '' ? $@ : "errno=$!";  chomp $eval_stat;
  };
  $Mail::SpamAssassin::Logger::LOG_SA{INHIBIT_LOGGING_IN_SIGCHLD_HANDLER} = 0;

  if (defined $eval_stat) {
    if ($self->check_syslog_sigpipe($msg)) {
      # dealt with
    }
    else {
      warn "logger: syslog failed: $eval_stat\n";

      # only write this warning once, it gets annoying fast
      if (!$self->{already_done_failure_warning}) {
        warn "logger: try using --syslog-socket={unix,inet} or --syslog=file\n";
        $self->{already_done_failure_warning} = 1;
      }
    }
    $self->syslog_incr_failure_counter();
  }
  else {
    $self->{consecutive_failures} = 0;
    $self->check_syslog_sigpipe($msg); # check for SIGPIPE anyway (bug 3625)
  }

  $SIG{PIPE} = 'IGNORE';	# this may have been reset (bug 4026)
}

sub check_syslog_sigpipe {
  my ($self, $msg) = @_;

  if (!$self->{SIGPIPE_RECEIVED}) {
    return 0;     # didn't have a SIGPIPE
  }

  eval {
    # SIGPIPE received when writing to syslog -- close and reopen
    # the log handle, then try again.
    closelog();
    openlog($self->{ident}, 'cons,pid,ndelay', $self->{log_facility});
    syslog('debug', "%s", "syslog reopened");
    syslog('info', "%s", $msg);

    # now report what happend
    $msg = "SIGPIPE received, reopening log socket";
    dbg("log: $msg");
    syslog('info', "%s", $msg);

    # if we've received multiple sigpipes, logging is probably still broken.
    if ($self->{SIGPIPE_RECEIVED} > 1) {
      warn "logger: syslog failure: multiple SIGPIPEs received\n";
      $self->{disabled} = 1;
    }

    $self->{SIGPIPE_RECEIVED} = 0;
    return 1;
    1;  # just to not forget a good habit
  } or do {  # something died?  that's not good.
    my $eval_stat = $@ ne '' ? $@ : "errno=$!";  chomp $eval_stat;
    dbg("log: failure in check_syslog_sigpipe: $eval_stat");
    $self->syslog_incr_failure_counter();
  }
}

sub syslog_incr_failure_counter {
  my ($self) = @_;

  $self->{consecutive_failures}++;
  if ($self->{consecutive_failures}++ > $self->{failure_threshold}) {
    warn("logger: syslog() failed " . $self->{consecutive_failures} .
	 " times in a row, disabled\n");
    $self->{disabled} = 1;
    return 1;
  }
  return 0;
}

sub close_log {
  my ($self) = @_;

  closelog();
}

1;
