Monks,

This one is doing my head in. The program below is a reduced testcase of something bigger and even uglier, but it exhibits the same baffling behaviour as this one.

I posted a rather badly prepared question along the same lines about a week ago and, shortly after I found a workaround that I can't live with any more. And I'm back looking for a solution.

There is a call to a forking sub 'fork_one' that can be placed in one of two positions in the program. In either position, the 'fork_one' routine behaves exactly as expected. However, when the call is made in the second position, weird stuff happens later on.

In the first position, the 'fork_one' ends up running in an orphaned process, nothing to do with the main daemon. In the second position, it is a child of the main daemon.

Regardless of the positioning of the call to 'fork_one', when the accept receives a connection it calls the forking sub 'fork_three' which does its business and dies.

Depending on the position of the 'fork_one' routine, the accept subsequently either works perfectly normally or just blocks/hangs. The connection is made by the client, but no SSL negotiation happens.

If you don't exit in fork_three, but allow it to return to the main loop and the 'accept', it will correctly accept the next connection. I only say this to say that the socket isn't fundamentally broken, not because I think this is a rational thing to do.

By now I've pretty much forgotten what it was I was actually trying to communicate and in place of a real client, I've been hitting it with:

openssl s_client -cert certs/capsclscert.pem -key certs/capscls_pk.pem
+ -CAfile certs/cacert.pem -connect 10.250.3.242:6023

[download]
The test program is:
#!/usr/bin/perl
 
use strict;
use warnings;
use IO::Socket::SSL;
use POSIX ":sys_wait_h";
 
 
my $pidfilename = 'sftest';
 
# try monitor fork here:
#fork_one();
# ... and everything is ok
 
# become a daemon
my $pid;
if (!defined($pid = fork)) {
        die "Cannot daemonize myself: $! \n";
}elsif ($pid) {
        # I am the parent and the fork suceeded.  Duck out now
        print "created daemon in $pid.  I ($$) am ducking out\n";
        exit;
}
 
 
# Try the monitor fork here:
fork_one();
#... and the second call to accept hangs
 
print "I'm daemonized on $$ \n";
 
sub REAPER {
  {} until ( waitpid(-1, WNOHANG) == -1)
}
$SIG{CHLD} =\&REAPER;
 
my $sock;
 
if(!($sock = IO::Socket::SSL->new( Listen => 5,
                                   LocalAddr => '10.250.3.242',
                                   LocalPort => '6023',
                                   Proto     => 'tcp',
                                   SSL_verify_mode => 0x01,
                                   SSL_cert_file => 'certs/capssvcert.
+pem',
                                   SSL_key_file  => 'certs/capssv_pk.p
+em',
                                   Reuse     => 1,
                                 )) ) {
  die "unable to create socket: ", &IO::Socket::SSL::errstr, "\n";
}
 
while (1 ) {
    my $s;
    print "$$ is listening...\n";
    if ( $s = $sock->accept() ) {
       fork_three($s);
    }
}
 
####################
 
 
sub fork_one {
 
  my $pid;
  if (!defined($pid = fork)) {
        die "Cannot make monitor process: $! \n";
  }elsif ($pid) {
        # I am the parent and the fork suceeded.  Duck out now
        print "created monitor process in $pid.  I ($$) am resuming \n
+";
        return;
  }
 
  print "I ($$) am going to loop around doing some fatuous monitoring 
+process\n";
 
  while (1) {
      sleep 30;
      print "$$ is still monitoring\n";
  }
 
}
 
sub fork_three {
   
  my $s = shift;
  my $pid;
  if (!defined($pid = fork)) {
        die "Cannot make dummy event processor: $! \n";
  }elsif ($pid) {
        # I am the parent and the fork suceeded.  Duck out now
        print "created dummy event processor in $pid.  I ($$) am resum
+ing \n";
        return;
  }
 
 
  print "I ($$) am going to do some dummy event  process\n";
  $s->close(SSL_no_shutdown => 1);
  # my work is done...
  exit;
 
}

[download]

In reply to Socket Hangs Revisited by mungohill

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