#!/usr/bin/perl

use strict;

$|=1;

my $slicename;
my $xid;
my $portnumber;
my $fuser_cmd;
my $pid;
my @vinfo;
my $foo;
my $real_xid;

$slicename = $ARGV[0];
$xid = int(`id -u $slicename`) || die("Could not determine xid of $slicename\n");
$portnumber = <STDIN>;
chop($portnumber);

if ($portnumber!~/^\d+$/) {
        die("$portnumber is not a port number");
}

if ($portnumber<61001 || $portnumber>65535) {
	die("$portnumber lies in the local port-rover range\n");
}

$fuser_cmd = "ncontext --nid $xid --migrate -- vcontext --xid $xid --migrate fuser -n tcp $portnumber 2>/dev/null";
$pid = `$fuser_cmd` || die("Please bind to port $portnumber, e.g. run nc -l $portnumber."); 
$pid=~s/\s+//g;

my $cat_cmd;

$cat_cmd = "chcontext --ctx 1 cat /proc/$pid/vinfo";
$_ = `$cat_cmd`;
@vinfo = split /\n/;
($#vinfo>0) || die("Port reservation failed. Please try again.\n");

$_=@vinfo[0];

($foo,$real_xid) = split;

if (int($real_xid)!=$xid) {
    die("Port $portnumber belongs to user $real_xid, not to you.\n"); 
}

# OK. We're good
# Only, slices are allowed only 1 port reservation/session

if ( -f "/dev/shm/$slicename-port" ) {
	print "You have already reserved the following port:\n";
	system("cat /dev/shm/$slicename-port");
	exit(1);
}

open FIL,">/dev/shm/$slicename-port";
print FIL "$portnumber";
close FIL;

system("iptables -t mangle -A INPUT -m tcp -p tcp --dport $portnumber -j MARK --set-mark $xid");