IO::Socket::SSL + fork problem

[mrhyde]

I am writing a network client application which simply receives some signals from the server and returns responses.

The problem is when a forked child process is trying to write to the socket on the second call, IO::Socket::SSL simply closes the connection. Though, the first time it's called ( tick() ), it doesn't break the connection and returns a healthy response.

The problem exists:
1) only on Linux, it works fine on Windows.
2) only with IO::Socket::SSL, it works fine with IO::Socket::INET

minimized code to reproduce the problem:

use strict;
use warnings;
use IO::Socket::SSL qw(debug4);

my $_pid;
my $connection = IO::Socket::SSL->new(
        PeerHost => 'local.btc-node',
        PeerPort => 7566,
        Proto=> 'tcp',
        Timeout => 8,
        SSL_verify_mode => 0x00
    ) or die($!);

    while(<$connection>)
    {
        if(/action1/)
         {
            # do something, no problem
         }
        elsif(/tick\s+([^\d\s\t]+)/)
         {
            my $currency = $1;
            tick ($connection, $currency);
         }
    }

    
    
sub tick {
my $socket = shift;
my $currency = shift;


    if ($_pid = fork)
    {
        waitpid($_pid, 0);
    } 
    else 
    {
      if (fork)
       {
            exit;
       } 
       else 
       {
            my $response =`tick $currency 2>&1 3>&1`;
            $socket->print($response . "\n"); # without this line $con
+nection doesn't break on the second call
            exit;
       }
  }
}

I suppose there is a socket reference being missed, or something similar. What am I doing wrong?

[Anonymous Monk]

Well, you cannot fork an SSL socket. It's a protocol layer with internal state. The first write would modify the state but that isn't reflected in your main process. You're going to need some event-driven framework.

[mrhyde]

Is it possible to realize with standard IO modules?

[BrowserUk]

The probable reason it works on windows and not linux is that fork under windows is really just a thread, so the "forked child" is actually still a part of the same process, (which according to anonymonk above is important to ssl connections?).

That suggests a possible way forward would be to use threads rather than fork, which would (might) get around the problem on both platforms. Of course, it might create others.

[mrhyde]

use strict;
use warnings;
use IO::Select;
use IO::Socket::SSL;
use threads;
use threads::shared;
my %misc :shared;
my @dout :shared;
my %outputs :shared;
threads->create('pool');

my $connection = IO::Socket::SSL->new(PeerHost => 'local.btc-node', 
                                      PeerPort => 7566, Proto=> 'tcp')
+ or die($!);

my $_sel = IO::Select->new;
$_sel->add($connection);
$connection->blocking(0);

while(1)
 {
  my ($readable, undef, undef) = IO::Select->select($_sel, undef, $_se
+l, 0.21);
       if(scalar keys %outputs > 0)
       {
              foreach my $__a (keys %outputs){
                foreach my $_line (@dout){
                     $_line =~ s/[\r\n]+//g;
                     next if $_line eq '';
                     $connection->print("$_line\n");
                }
                delete $outputs{$__a};
        }
     }
  foreach my $socket (@$readable)
   {
    my $n = sysread($socket,my $msg,4096);
    if(defined $n)
     {
        if($msg =~ /tick\s+([^\d\s\t]+)/)
         {
            my $currency = $1;
            tick ($currency);
         }
     }
    }
 }



    
sub tick {
my $currency = shift;
$misc{arg} = $currency;
}

sub pool {
 while(1){
    my $thread = threads->create(t) if defined $misc{arg};
    select(undef, undef, undef, 0.52);
    foreach(threads->list){ undef $misc{arg}; $_->detach(); }
 }
}

sub t{
 @dout="hi $misc{arg}";
 $outputs{int(rand 500)}=1;
}

[noxxi]

Since the issue was also reported as a bug for IO::Socket::SSL: You can find a detailed explanation what the reason for the behavior is and why this is not a bug in IO::Socket::SSL but a bug in the application at the github repository for IO::Socket::SSL.