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# $OpenBSD: Tap.pm,v 1.1 2016/09/28 12:40:35 bluhm Exp $
# Copyright (c) 2014 Alexander Bluhm <bluhm@openbsd.org>
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
# Encapsulate tap interface handling into separate module.
use strict;
use warnings;
package Tap;
use parent 'Exporter';
our @EXPORT_OK = qw(opentap);
use Carp;
use Fcntl;
use File::Basename;
use POSIX qw(_exit);
use PassFd 'recvfd';
use Socket;
sub opentap {
my ($tap_number) = @_;
my $tap_device = "/dev/tap$tap_number";
if ($> == 0) {
sysopen(my $tap, $tap_device, O_RDWR)
or croak "Open $tap_device failed: $!";
return $tap;
}
if (!$ENV{SUDO}) {
die "To open the device $tap_device you must run as root or\n".
"set the SUDO environment variable and allow closefrom_override.\n";
}
my $opentap;
my $curdir = dirname($0) || ".";
if (-x "$curdir/opentap") {
$opentap = "$curdir/opentap";
} elsif (-x "./opentap") {
$opentap = "./opentap";
} else {
die "To open the device $tap_device the tool opentap is needed.\n".
"Executable opentap not found in $curdir or current directory.\n";
}
socketpair(my $parent, my $child, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
or croak "Socketpair failed: $!";
$child->fcntl(F_SETFD, 0)
or croak "Fcntl setfd failed: $!";
defined(my $pid = fork())
or croak "Fork failed: $!";
unless ($pid) {
# child process
close($parent) or do {
warn "Close parent socket failed: $!";
_exit(3);
};
my @cmd = ($ENV{SUDO}, '-C', $child->fileno()+1, $opentap,
$child->fileno(), $tap_number);
exec(@cmd);
warn "Exec '@cmd' failed: $!";
_exit(3);
}
# parent process
close($child)
or croak "Close child socket failed: $!";
my $tap = recvfd($parent)
or croak "Recvfd failed: $!";
wait()
or croak "Wait failed: $!";
$? == 0
or croak "Child process failed: $?";
return $tap;
}
1;
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