#!/usr/bin/perl
#
# Open an SSH tunnel using the Net::OpenSSH module and keep it opened with an infinite loop.
#

use strict;
use warnings;
use Anvil::Tools;
use File::Basename;
use Net::OpenSSH;

$| = 1;

my $THIS_FILE           =  ($0 =~ /^.*\/(.*)$/)[0];
my $running_directory   =  ($0 =~ /^(.*?)\/$THIS_FILE$/)[0];
if (($running_directory =~ /^\./) && ($ENV{PWD}))
{
	$running_directory =~ s/^\./$ENV{PWD}/;
}

my $anvil = Anvil::Tools->new({ on_sig_int => \&close_connection, on_sig_term => \&close_connection });

my $echo = $anvil->data->{path}{exe}{'echo'};
my $rm   = $anvil->data->{path}{exe}{'rm'};
my $sed  = $anvil->data->{path}{exe}{'sed'};

$anvil->Get->switches;

my $connect_child        = $anvil->data->{switches}{'child'};
my $switch_debug         = $anvil->data->{switches}{'debug'} || 3;
my $ssh_ctl_cmd          = $anvil->data->{switches}{'ctl-cmd'};
my $ssh_ctl_path         = $anvil->data->{switches}{'ctl-path'};
my $ssh_forward          = $anvil->data->{switches}{'forward'};
my $ssh_forward_lport    = $anvil->data->{switches}{'forward-lport'};
my $ssh_forward_rport    = $anvil->data->{switches}{'forward-rport'};
my $ssh_port             = $anvil->data->{switches}{'port'};
my $ssh_target           = $anvil->data->{switches}{'target'};
my $ssh_test_interval    = $anvil->data->{switches}{'test-interval'};
my $ssh_tunnel_ls_path   = $anvil->data->{switches}{'tunnel-ls-path'};
my $ssh_tunnel_ls_prefix = $anvil->data->{switches}{'tunnel-ls-prefix'};
my $ssh_user             = $anvil->data->{switches}{'user'};

if ( (defined $ssh_ctl_path) && (not $ssh_ctl_path =~ /^(?:#!SET!#|)$/) )
{
	my ($ssh_ctl_name) = fileparse($ssh_ctl_path);

	$ssh_tunnel_ls_path //= $anvil->data->{path}{'directories'}{'tmp'}."/$ssh_ctl_name";
}

# Global for holding the SSH file handle; needed because it's hard to pass
# params to signal handlers.
my $ssh;

if ($connect_child)
{
	(my $open_rcode, $ssh) = open_connection({
		ctl_path        => $ssh_ctl_path,
		debug           => $switch_debug,
		external_parent => 1,
		port            => $ssh_port,
		target          => $ssh_target,
		user            => $ssh_user,
	});

	$anvil->nice_exit({ exit_code => $open_rcode }) if ($open_rcode);

	my ($manage_rcode) = manage_tunnel({
		ctl_cmd       => $ssh_ctl_cmd,
		debug         => $switch_debug,
		forward       => $ssh_forward,
		forward_lport => $ssh_forward_lport,
		forward_rport => $ssh_forward_rport,
		ls_path       => $ssh_tunnel_ls_path,
		ls_prefix     => $ssh_tunnel_ls_prefix,
		ssh_fh        => $ssh,
	});

	$anvil->nice_exit({ exit_code => $manage_rcode }) if ($manage_rcode);
}
else
{
	$ssh_test_interval = 60 if (not is_int($ssh_test_interval));

	(my $open_rcode, $ssh) = open_connection({
		ctl_path => $ssh_ctl_path,
		debug    => $switch_debug,
		port     => $ssh_port,
		target   => $ssh_target,
		user     => $ssh_user,
	});

	$anvil->nice_exit({ exit_code => $open_rcode }) if ($open_rcode);

	if (not defined $ssh_ctl_path)
	{
		# Not making an external parent connection; forward using
		# internal parent connection.
		my ($manage_rcode) = manage_tunnel({
			ctl_cmd       => $ssh_ctl_cmd,
			debug         => $switch_debug,
			forward       => $ssh_forward,
			forward_lport => $ssh_forward_lport,
			forward_rport => $ssh_forward_rport,
			ls_path       => $ssh_tunnel_ls_path,
			ls_prefix     => $ssh_tunnel_ls_prefix,
			ssh_fh        => $ssh,
		});

		$anvil->nice_exit({ exit_code => $manage_rcode }) if ($manage_rcode);
	}

	my $is_ssh_tunnel_alive = 1;

	while ($is_ssh_tunnel_alive)
	{
		$is_ssh_tunnel_alive = $ssh->test($echo);

		sleep($ssh_test_interval);
	}

	close_connection({ debug => $switch_debug });
}

$anvil->nice_exit({ exit_code => 0 });

#
# Functions
#

sub build_ssh_fh_key
{
	my ($user, $target, $port) = @_;

	return "${user}\@${target}:${port}";
}

sub close_connection
{
	my $parameters     = shift;
	my $debug          = $parameters->{debug} || 3;
	my $ssh_fh         = $parameters->{ssh_fh} // $ssh;
	my $tunnel_ls_path = $parameters->{tunnel_ls_path} // $ssh_tunnel_ls_path;

	return (1) if ( (not defined $ssh_fh) || (not $ssh_fh->can("disconnect")) );

	my $ctl_path = $ssh_fh->get_ctl_path();
	my $pid      = $ssh_fh->get_master_pid();

	$ssh_fh->disconnect();

	$anvil->Log->variables({ source => $THIS_FILE, line => __LINE__, level => $debug, list => {
		message => "Parent connection [$pid] using [$ctl_path] disconnected."
	} });

	if ( (defined $tunnel_ls_path) && (-e $tunnel_ls_path) )
	{
		$anvil->System->call({ shell_call => "$rm -f '$tunnel_ls_path'" });
	}

	return (0);
}

sub is_valid_tunnel_ctl_command
{
	return defined $_[0] && $_[0] =~ /^(?:cancel|forward)$/;
}

sub is_valid_forward
{
	return defined $_[0] && $_[0] =~ /^(?:L|R)$/;
}

sub is_int
{
	return defined $_[0] && $_[0] =~ /^\d+$/;
}

sub is_ssh_fh_defined
{
	return defined $_[0] ? 1 : 0;
}

sub manage_tunnel
{
	my $parameters    = shift;
	my $ctl_cmd       = $parameters->{ctl_cmd} // "forward";
	my $debug         = $parameters->{debug} || 3;
	my $forward       = $parameters->{forward} // "R";
	my $forward_laddr = $parameters->{forward_laddr} // "0.0.0.0";
	my $forward_lport = $parameters->{forward_lport};
	my $forward_raddr = $parameters->{forward_raddr} // "0.0.0.0";
	my $forward_rport = $parameters->{forward_rport};
	my $ls_path       = $parameters->{ls_path};
	my $ls_prefix     = $parameters->{ls_prefix} // "";
	my $ssh_fh        = $parameters->{ssh_fh};

	$anvil->Log->variables({ source => $THIS_FILE, line => __LINE__, level => $debug, list => $parameters, prefix => "manage_tunnel" });

	return (1) if ( (not is_ssh_fh_defined($ssh_fh))
		|| (not is_valid_tunnel_ctl_command($ctl_cmd))
		|| (not is_valid_forward($forward))
		|| (not is_int($forward_lport))
		|| (not is_int($forward_rport)) );

	my $addr_a = $forward_laddr;
	my $addr_b = $forward_raddr;
	my $port_a = $forward_lport;
	my $port_b = $forward_rport;

	# When remote forward, change the option and reverse the addresses and ports.
	if ($forward eq "R")
	{
		$addr_a = $forward_raddr;
		$addr_b = $forward_laddr;
		$port_a = $forward_rport;
		$port_b = $forward_lport;
	}

	my $forward_opt = "-${forward}${addr_a}:${port_a}:${addr_b}:${port_b}";

	$anvil->Log->variables({ source => $THIS_FILE, line => __LINE__, level => $debug, list => { forward_opt => $forward_opt } });

	$ssh_fh->system({ ssh_opts => [ "-O", $ctl_cmd, $forward_opt ] }) or return (1);

	if (defined $ls_path)
	{
		my $write_call = $ctl_cmd eq "forward"
			? "$echo '${ls_prefix}${forward_opt}' >>'$ls_path'"
			: "$sed -i '/$forward_opt/d' '$ls_path'";

		$anvil->System->call({ shell_call => $write_call });
	}

	return (0);
}

sub open_connection
{
	my $parameters      = shift;
	my $ctl_path        = $parameters->{ctl_path};
	my $debug           = $parameters->{debug} || 3;
	my $external_parent = $parameters->{external_parent} ? 1 : 0;
	my $port            = $parameters->{port} || 22;
	my $target          = $parameters->{target};
	my $user            = $parameters->{user} // "root";

	$anvil->Log->variables({ source => $THIS_FILE, line => __LINE__, level => $debug, list => $parameters, prefix => "open_connection" });

	if ($external_parent)
	{
		# Control socket path must exist if we want to use an
		# external parent connection.
		return (1) if ( (not defined $ctl_path) || (not -e $ctl_path) );

		$target //= "0.0.0.0";
	}
	else
	{
		return (1) if ( (not defined $target) || ($target eq "") );

		if (defined $ctl_path)
		{
			# Control socket path mustn't exist if we want to
			# establish a new parent connection with it.
			return (1) if ( ($ctl_path eq "") || (-e $ctl_path) );
		}
	}

	my ($output, $error, $rcode) = $anvil->Remote->call({
		# Start new connection; doesn't mean "don't cache the created connection".
		no_cache    => 1,
		ossh_opts   => [ ctl_path => $ctl_path, external_master => $external_parent ],
		port        => $port,
		remote_user => $user,
		shell_call  => "$echo 1",
		target      => $target,
	});

	$anvil->Log->variables({ source => $THIS_FILE, line => __LINE__, level => $debug, list => {
		error  => $error,
		output => $output,
		rcode  => $rcode,
	} });

	return (1) if ( $rcode || ($output ne "1") );

	my $ssh_fh_key = build_ssh_fh_key($user, $target, $port);

	$anvil->Log->variables({ source => $THIS_FILE, line => __LINE__, level => $debug, list => { ssh_fh_key => $ssh_fh_key } });

	my $ssh_fh = $anvil->data->{cache}{ssh_fh}{$ssh_fh_key};

	return (1) if (not is_ssh_fh_defined($ssh_fh));

	delete $anvil->data->{cache}{ssh_fh}{$ssh_fh_key};

	$anvil->Log->variables({ source => $THIS_FILE, line => __LINE__, level => $debug, list => {
		ctl_path => $ssh_fh->get_ctl_path(),
		pid      => $ssh_fh->get_master_pid(),
	} });

	return (0, $ssh_fh);
}