debconf-apt-progress

#!/usr/bin/perl -w

=head1 NAME

debconf-apt-progress - install packages using debconf to display a progress bar

=head1 SYNOPSIS

 debconf-apt-progress [--] command [args ...]
 debconf-apt-progress --config
 debconf-apt-progress --start
 debconf-apt-progress --from waypoint --to waypoint [--] command [args ...]
 debconf-apt-progress --stop

=head1 DESCRIPTION

B<debconf-apt-progress> installs packages using debconf to display a
progress bar. The given I<command> should be any command-line apt frontend;
specifically, it must send progress information to the file descriptor
selected by the C<APT::Status-Fd> configuration option, and must keep the
file descriptors nominated by the C<APT::Keep-Fds> configuration option open
when invoking debconf (directly or indirectly), as those file descriptors
will be used for the debconf passthrough protocol.

The arguments to the command you supply should generally include B<-y> (for
B<apt-get> or B<aptitude>) or similar to avoid the apt frontend prompting
for input. B<debconf-apt-progress> cannot do this itself because the
appropriate argument may differ between apt frontends.

The B<--start>, B<--stop>, B<--from>, and B<--to> options may be used to
create a progress bar with multiple segments for different stages of
installation, provided that the caller is a debconf confmodule. The caller
may also interact with the progress bar itself using the debconf protocol if
it so desires.

debconf locks its config database when it starts up, which makes it
unfortunately inconvenient to have one instance of debconf displaying the
progress bar and another passing through questions from packages being
installed. If you're using a multiple-segment progress bar, you'll need to
eval the output of the B<--config> option before starting the debconf
frontend to work around this. See L<the EXAMPLES section/EXAMPLES> below.

=head1 OPTIONS

=over 4

=item B<--config>

Print environment variables necessary to start up a progress bar frontend.

=item B<--start>

Start up a progress bar, running from 0 to 100 by default. Use B<--from> and
B<--to> to use other endpoints.

=item B<--from> I<waypoint>

If used with B<--start>, make the progress bar begin at I<waypoint> rather
than 0.

Otherwise, install packages with their progress bar beginning at this
"waypoint". Must be used with B<--to>.

=item B<--to> I<waypoint>

If used with B<--start>, make the progress bar end at I<waypoint> rather
than 100.

Otherwise, install packages with their progress bar ending at this
"waypoint". Must be used with B<--from>.

=item B<--stop>

Stop a running progress bar.

=item B<--no-progress>

Avoid starting, stopping, or stepping the progress bar. Progress
messages from apt, media change events, and debconf questions will still
be passed through to debconf.

=item B<--dlwaypoint> I<percentage>

Specify what percent of the progress bar to use for downloading packages.
The remainder will be used for installing packages. The default is to use
15% for downloading and the remaining 85% for installing.

=item B<--logfile> I<file>

Send the normal output from apt to the given file.

=item B<--logstderr>

Send the normal output from apt to stderr. If you supply neither
B<--logfile> nor B<--logstderr>, the normal output from apt will be
discarded.

=item B<-->

Terminate options. Since you will normally need to give at least the B<-y>
argument to the command being run, you will usually need to use B<--> to
prevent that being interpreted as an option to B<debconf-apt-progress>
itself.

=back

=head1 EXAMPLES

Install the GNOME desktop and an X window system development environment
within a progress bar:

 debconf-apt-progress -- aptitude -y install gnome x-window-system-dev

Install the GNOME, KDE, and XFCE desktops within a single progress bar,
allocating 45% of the progress bar for each of GNOME and KDE and the
remaining 10% for XFCE:

 #! /bin/sh
 set -e
 case $1 in
   '')
     eval "$(debconf-apt-progress --config)"
     "$0" debconf
     ;;
   debconf)
     . /usr/share/debconf/confmodule
     debconf-apt-progress --start
     debconf-apt-progress --from 0 --to 45 -- apt-get -y install gnome
     debconf-apt-progress --from 45 --to 90 -- apt-get -y install kde
     debconf-apt-progress --from 90 --to 100 -- apt-get -y install xfce4
     debconf-apt-progress --stop
     ;;
 esac

=head1 RETURN CODE

The exit code of the specified command is returned, unless the user hit the
cancel button on the progress bar. If the cancel button was hit, a value of
30 is returned. To avoid ambiguity, if the command returned 30, a value of
3 will be returned.

=cut

use strict;
use POSIX;
use Fcntl;
use Getopt::Long;
# Avoid starting the debconf frontend just yet.
use Debconf::Client::ConfModule ();

my ($config, $start, $from, $to, $stop);
my $progress=1;
my $dlwaypoint=15;
my ($logfile, $logstderr);
my $had_frontend;

sub checkopen (@) {
	my $file = $_[0];
	my $fd = POSIX::open($file, &POSIX::O_RDONLY);
	defined $fd or die "$0: can't open $_[0]: $!\n";
	return $fd;
}

sub checkclose ($) {
	my $fd = $_[0];
	unless (POSIX::close($fd)) {
		return if $! == &POSIX::EBADF;
		die "$0: can't close fd $fd: $!\n";
	}
}

sub checkdup2 ($$) {
	my ($oldfd, $newfd) = @_;
	checkclose($newfd);
	POSIX::dup2($oldfd, $newfd)
		or die "$0: can't dup fd $oldfd to $newfd: $!\n";
}

sub nocloexec (*) {
	my $fh = shift;
	my $flags = fcntl($fh, F_GETFD, 0);
	fcntl($fh, F_SETFD, $flags & ~FD_CLOEXEC);
}

sub nonblock (*) {
	my $fh = shift;
	my $flags = fcntl($fh, F_GETFL, 0);
	fcntl($fh, F_SETFL, $flags | O_NONBLOCK);
}

# Open the given file descriptors to make sure they won't accidentally be
# used by Perl, leading to confusion.
sub reservefds (@) {
	my $null = checkopen('/dev/null');
	my $close = 1;
	for my $fd (@_) {
		if ($null == $fd) {
			$close = 0;
		} else {
			checkclose($fd);
			checkdup2($null, $fd);
		}
	}
	if ($close) {
		checkclose($null);
	}
}

# Does this environment variable exist, and is it non-empty?
sub envnonempty ($) {
	my $name = shift;
	return (exists $ENV{$name} and $ENV{$name} ne '');
}

sub start_debconf (@) {
	if (! $ENV{DEBIAN_HAS_FRONTEND}) {
		# Save existing environment variables.
		if (envnonempty('DEBCONF_DB_REPLACE')) {
			$ENV{DEBCONF_APT_PROGRESS_DB_REPLACE} =
				$ENV{DEBCONF_DB_REPLACE};
		}
		if (envnonempty('DEBCONF_DB_OVERRIDE')) {
			$ENV{DEBCONF_APT_PROGRESS_DB_OVERRIDE} =
				$ENV{DEBCONF_DB_OVERRIDE};
		}

		# Make sure the main configdb is opened read-only ...
		$ENV{DEBCONF_DB_REPLACE} = 'configdb';
		# ... and stack a writable db on top of it, since the
		# passthrough instance is going to be sending us db updates.
		$ENV{DEBCONF_DB_OVERRIDE} = 'Pipe{infd:none outfd:none}';

		# Leave a note for ourselves. We need to do it this way
		# round since DEBIAN_HAS_FRONTEND will be set the second
		# time round even if it isn't set initially.
		$ENV{DEBCONF_APT_PROGRESS_NO_FRONTEND} = 1;

		# Restore @ARGV so that
		# Debconf::Client::ConfModule::import() can use it.
		@ARGV = @_;
	}

	import Debconf::Client::ConfModule;
}

sub passthrough (@) {
	my $priority = Debconf::Client::ConfModule::get('debconf/priority');

	defined(my $pid = fork) or die "$0: can't fork: $!\n";
	if (!$pid) {
		close STATUS_READ;
		close COMMAND_WRITE;
		close DEBCONF_COMMAND_READ;
		close DEBCONF_REPLY_WRITE;
		$^F = 6; # avoid close-on-exec
		if (fileno(COMMAND_READ) != 0) {
			checkdup2(fileno(COMMAND_READ), 0);
			close COMMAND_READ;
		}
		if (fileno(APT_LOG) != 1) {
			checkclose(1);
			checkdup2(fileno(APT_LOG), 1);
		}
		if (fileno(APT_LOG) != 2) {
			checkclose(2);
			checkdup2(fileno(APT_LOG), 2);
		}
		close APT_LOG;
		delete $ENV{DEBIAN_HAS_FRONTEND};
		delete $ENV{DEBCONF_REDIR};
		delete $ENV{DEBCONF_SYSTEMRC};
		delete $ENV{DEBCONF_PIPE}; # just in case ...
		$ENV{DEBIAN_FRONTEND} = 'passthrough';
		$ENV{DEBIAN_PRIORITY} = $priority;
		$ENV{DEBCONF_READFD} = 5;
		$ENV{DEBCONF_WRITEFD} = 6;
		$ENV{APT_LISTCHANGES_FRONTEND} = 'none';
		# If we already had a debconf frontend when we started, then
		# the passthrough child needs to use the same pipe-database
		# trick as we do. See start_debconf.
		if ($had_frontend) {
			$ENV{DEBCONF_DB_REPLACE} = 'configdb';
			$ENV{DEBCONF_DB_OVERRIDE} = 'Pipe{infd:none outfd:none}';
		}
		exec @_;
	}

	close STATUS_WRITE;
	close COMMAND_READ;
	close DEBCONF_COMMAND_WRITE;
	close DEBCONF_REPLY_READ;
	return $pid;
}

sub handle_status ($$$) {
	my ($from, $to, $line) = @_;
	my ($status, $pkg, $percent, $description) = split ':', $line, 4;

	my ($min, $len);
	if ($status eq 'dlstatus') {
		$min = 0;
		$len = $dlwaypoint;
	}
	elsif ($status eq 'pmstatus') {
		$min = $dlwaypoint;
		$len = 100 - $dlwaypoint;
	}
	elsif ($status eq 'media-change') {
		Debconf::Client::ConfModule::subst(
			'debconf-apt-progress/media-change', 'MESSAGE',
			$description);
		my @ret = Debconf::Client::ConfModule::input(
			'critical', 'debconf-apt-progress/media-change');
		$ret[0] == 0 or die "Can't display media change request!\n";
		Debconf::Client::ConfModule::go();
		print COMMAND_WRITE "\n" || die "can't talk to command fd: $!";
		return;
	}
	else {
		return;
	}

	$percent = ($percent * $len / 100 + $min);
	$percent = ($percent * ($to - $from) / 100 + $from);
	$percent =~ s/\..*//;
	if ($progress) {
		my @ret=Debconf::Client::ConfModule::progress('SET', $percent);
		if ($ret[0] eq '30') {
			cancel();
		}
	}
	Debconf::Client::ConfModule::subst(
		'debconf-apt-progress/info', 'DESCRIPTION', $description);
	my @ret=Debconf::Client::ConfModule::progress(
		'INFO', 'debconf-apt-progress/info');
	if ($ret[0] eq '30') {
		cancel();
	}
}

sub handle_debconf_command ($) {
	my $line = shift;

	# Debconf::Client::ConfModule has already dealt with checking
	# DEBCONF_REDIR.
	print "$line\n" || die "can't write to stdout: $!";
	my $ret = <STDIN>;
	chomp $ret;
	print DEBCONF_REPLY_WRITE "$ret\n" ||
		die "can't write to DEBCONF_REPLY_WRITE: $!";
}

my $pid;
sub run_progress ($$@) {
	my $from = shift;
	my $to = shift;
	my $command = shift;
	local (*STATUS_READ, *STATUS_WRITE);
	local (*COMMAND_READ, *COMMAND_WRITE);
	local (*DEBCONF_COMMAND_READ, *DEBCONF_COMMAND_WRITE);
	local (*DEBCONF_REPLY_READ, *DEBCONF_REPLY_WRITE);
	local *APT_LOG;
	use IO::Handle;

	if ($progress) {
		my @ret=Debconf::Client::ConfModule::progress(
			'INFO', 'debconf-apt-progress/preparing');
		if ($ret[0] eq '30') {
			cancel();
			return 30;
		}
	}

	reservefds(4, 5, 6);

	pipe STATUS_READ, STATUS_WRITE
		or die "$0: can't create status pipe: $!";
	nonblock(\*STATUS_READ);
	checkdup2(fileno(STATUS_WRITE), 4);
	open STATUS_WRITE, '>&=4'
		or die "$0: can't reopen STATUS_WRITE as fd 4: $!";
	nocloexec(\*STATUS_WRITE);

	pipe COMMAND_READ, COMMAND_WRITE
		or die "$0: can't create command pipe: $!";
	nocloexec(\*COMMAND_READ);
	COMMAND_WRITE->autoflush(1);

	pipe DEBCONF_COMMAND_READ, DEBCONF_COMMAND_WRITE
		or die "$0: can't create debconf command pipe: $!";
	nonblock(\*DEBCONF_COMMAND_READ);
	checkdup2(fileno(DEBCONF_COMMAND_WRITE), 6);
	open DEBCONF_COMMAND_WRITE, '>&=6'
		or die "$0: can't reopen DEBCONF_COMMAND_WRITE as fd 6: $!";
	nocloexec(\*DEBCONF_COMMAND_WRITE);

	pipe DEBCONF_REPLY_READ, DEBCONF_REPLY_WRITE
		or die "$0: can't create debconf reply pipe: $!";
	checkdup2(fileno(DEBCONF_REPLY_READ), 5);
	open DEBCONF_REPLY_READ, '<&=5'
		or die "$0: can't reopen DEBCONF_REPLY_READ as fd 5: $!";
	nocloexec(\*DEBCONF_REPLY_READ);
	DEBCONF_REPLY_WRITE->autoflush(1);

	if (defined $logfile) {
		open APT_LOG, '>>', $logfile
			or die "$0: can't open $logfile: $!";
	} elsif ($logstderr) {
		open APT_LOG, '>&STDERR'
			or die "$0: can't duplicate stderr: $!";
	} else {
		open APT_LOG, '>', '/dev/null'
			or die "$0: can't open /dev/null: $!";
	}
	nocloexec(\*APT_LOG);

	$pid = passthrough $command,
		'-o', 'APT::Status-Fd=4',
		'-o', 'APT::Keep-Fds::=5',
		'-o', 'APT::Keep-Fds::=6',
		@_;

	my $status_eof = 0;
	my $debconf_command_eof = 0;
	my $status_buf = '';
	my $debconf_command_buf = '';

	# STATUS_READ should be the last fd to close. DEBCONF_COMMAND_WRITE
	# may end up captured by buggy daemons, so terminate the loop even
	# if we haven't hit $debconf_command_eof.
	while (not $status_eof) {
		my $rin = '';
		my $rout;
		vec($rin, fileno(STATUS_READ), 1) = 1;
		vec($rin, fileno(DEBCONF_COMMAND_READ), 1) = 1
			unless $debconf_command_eof;
		my $sel = select($rout = $rin, undef, undef, undef);
		if ($sel < 0) {
			next if $! == &POSIX::EINTR;
			die "$0: select failed: $!";
		}

		if (vec($rout, fileno(STATUS_READ), 1) == 1) {
			# Status message from apt. Transform into debconf
			# messages.
			while (1) {
				my $r = sysread(STATUS_READ, $status_buf, 4096,
						length $status_buf);
				if (not defined $r) {
					next if $! == &POSIX::EINTR;
					last if $! == &POSIX::EAGAIN or
						$! == &POSIX::EWOULDBLOCK;
					die "$0: read STATUS_READ failed: $!";
				}
				elsif ($r == 0) {
					if ($status_buf ne '' and
					    $status_buf !~ /\n$/) {
						$status_buf .= "\n";
					}
					$status_eof = 1;
					last;
				}
				last if $status_buf =~ /\n/;
			}

			while ($status_buf =~ /\n/) {
				my $status_line;
				($status_line, $status_buf) =
					split /\n/, $status_buf, 2;
				handle_status $from, $to, $status_line;
			}
		}

		if (vec($rout, fileno(DEBCONF_COMMAND_READ), 1) == 1) {
			# Debconf command. Pass straight through.
			while (1) {
				my $r = sysread(DEBCONF_COMMAND_READ,
						$debconf_command_buf, 4096,
						length $debconf_command_buf);
				if (not defined $r) {
					next if $! == &POSIX::EINTR;
					last if $! == &POSIX::EAGAIN or
						$! == &POSIX::EWOULDBLOCK;
					die "$0: read DEBCONF_COMMAND_READ " .
					    "failed: $!";
				}
				elsif ($r == 0) {
					if ($debconf_command_buf ne '' and
					    $debconf_command_buf !~ /\n$/) {
						$debconf_command_buf .= "\n";
					}
					$debconf_command_eof = 1;
					last;
				}
				last if $debconf_command_buf =~ /\n/;
			}

			while ($debconf_command_buf =~ /\n/) {
				my $debconf_command_line;
				($debconf_command_line, $debconf_command_buf) =
					split /\n/, $debconf_command_buf, 2;
				handle_debconf_command $debconf_command_line;
			}
		}
	}

	waitpid $pid, 0;
	undef $pid;
	my $status = $?;

	# make sure that the progress bar always gets to the end
	if ($progress) {
		my @ret=Debconf::Client::ConfModule::progress('SET', $to);
		if ($ret[0] eq '30') {
			cancel();
		}
	}

	if ($status & 127) {
		return 127;
	}

	return ($status >> 8);
}

# Called if the progress bar is cancelled. Starts with a SIGINT but
# if called repeatedly, falls back to SIGKILL.
my $cancelled=0;
my $cancel_sent_signal=0;
sub cancel () {
	$cancelled++;
	if (defined $pid) {
		$cancel_sent_signal++;
		if ($cancel_sent_signal == 1) {
			kill INT => $pid;
		}
		else {
			kill KILL => $pid;
		}
	}
}

sub start_bar ($$) {
	my ($from, $to) = @_;
	if ($progress) {
		Debconf::Client::ConfModule::progress(
			'START', $from, $to, 'debconf-apt-progress/title');
		my @ret=Debconf::Client::ConfModule::progress(
			'INFO', 'debconf-apt-progress/preparing');
		if ($ret[0] eq '30') {
			cancel();
		}
	}
}

sub stop_bar () {
	Debconf::Client::ConfModule::progress('STOP') if $progress;
	# If we don't stop, we leave a zombie in case some daemon fails to
	# disconnect from fd 3. Don't do this if debconf was already
	# running, though, since in that case we're running as part of a
	# larger application which will need to take its own care to stop
	# when it's finished.
	Debconf::Client::ConfModule::stop() unless $had_frontend;
}

# Restore saved environment variables.
if (envnonempty('DEBCONF_APT_PROGRESS_DB_REPLACE')) {
	$ENV{DEBCONF_DB_REPLACE} = $ENV{DEBCONF_APT_PROGRESS_DB_REPLACE};
} else {
	delete $ENV{DEBCONF_DB_REPLACE};
}
if (envnonempty('DEBCONF_APT_PROGRESS_DB_OVERRIDE')) {
	$ENV{DEBCONF_DB_OVERRIDE} = $ENV{DEBCONF_APT_PROGRESS_DB_OVERRIDE};
} else {
	delete $ENV{DEBCONF_DB_OVERRIDE};
}
$had_frontend = 1 unless $ENV{DEBCONF_APT_PROGRESS_NO_FRONTEND};
delete $ENV{DEBCONF_APT_PROGRESS_NO_FRONTEND}; # avoid inheritance

my @saved_argv = @ARGV;

my $result = GetOptions('config'       => \$config,
			'start'        => \$start,
			'from=i'       => \$from,
			'to=i'         => \$to,
			'stop'         => \$stop,
			'logfile=s'    => \$logfile,
			'logstderr'    => \$logstderr,
			'progress!'    => \$progress,
			'dlwaypoint=i' => \$dlwaypoint,
);

if (! $progress && ($start || $from || $to || $stop)) {
	die "--no-progress cannot be used with --start, --from, --to, or --stop\n";
}

unless ($start) {
	if (defined $from and not defined $to) {
		die "$0: --from requires --to\n";
	} elsif (defined $to and not defined $from) {
		die "$0: --to requires --from\n";
	}
}

my $mutex = 0;
++$mutex if $config;
++$mutex if $start;
++$mutex if $stop;
if ($mutex > 1) {
	die "$0: must use only one of --config, --start, or --stop\n";
}

if (($config or $stop) and (defined $from or defined $to)) {
	die "$0: cannot use --from or --to with --config or --stop\n";
}

start_debconf(@saved_argv) unless $config;

my $status = 0;

if ($config) {
	print <<'EOF';
DEBCONF_APT_PROGRESS_DB_REPLACE="$DEBCONF_DB_REPLACE"
DEBCONF_APT_PROGRESS_DB_OVERRIDE="$DEBCONF_DB_OVERRIDE"
export DEBCONF_APT_PROGRESS_DB_REPLACE DEBCONF_APT_PROGRESS_DB_OVERRIDE
DEBCONF_DB_REPLACE=configdb
DEBCONF_DB_OVERRIDE='Pipe{infd:none outfd:none}'
export DEBCONF_DB_REPLACE DEBCONF_DB_OVERRIDE
EOF
} elsif ($start) {
	$from = 0 unless defined $from;
	$to = 100 unless defined $to;
	start_bar($from, $to);
} elsif (defined $from) {
	$status = run_progress($from, $to, @ARGV);
} elsif ($stop) {
	stop_bar();
} else {
	start_bar(0, 100);
	if (! $cancelled) {
		$status = run_progress(0, 100, @ARGV);
		stop_bar();
	}
}

if ($cancelled) {
	# This is pure paranoia. What if the child was in the
	# middle of writing a debconf command out, only to be
	# interrupted with a truncated write? Let's send a no-op
	# command to finish it out just in case.
	Debconf::Client::ConfModule::get("debconf/priority");

	exit 30;
}
elsif ($status == 30) {
	exit 3;
}
else {
	exit $status;
}

=head1 AUTHORS

Colin Watson <cjwatson@debian.org>

Joey Hess <joeyh@debian.org>

=cut