Linux/NBD/Client.pm

=head1 NAME

Linux::NBD::Client - client (device) side of a network block device

=head1 SYNOPSIS

 use Linux::NBD::Client;

=head1 DESCRIPTION

WARNING: I talked to the author of the nbd driver because nbd is so
extremely racy (right now, stopping it often causes oopses, a server
crashing also often oopses etc..).

It turned out that he doesn't care at all and nbd is basically
unmaintained, so YMMV when using this module, especially when writing
servers.

He really should have said that on his nbd pages ;[.

OTOH, it works relatively reliable when you don't stop the servers, so
watch out and keep your fingers crossed.

=head1 METHODS

=over 4

=cut

package Linux::NBD::Client;

$VERSION = 0.21;

use Linux::NBD ();

use Carp qw(croak);
use Errno ();

=item $client = new Linux::NBD::Client [socket => $fh][, device => "/dev/nbdX"], ...

Create a new client.

Unless C<device> is given, an unused device node is looked up using the
C<device> method (this might result in an exception!).

=item $client->socket ([$tcp_socket])

Returns the current socket after setting a new one (if an argument is
supplied). The socket I<MUST> be a tcp socket. Believe me, bad things will
happen if not.

The special argument C<undef> will try to clear the socket, if any was
set.

=item $client->device ([$new_device])

Returns the current device node (e.g. C</dev/nbd2>) after setting a new one if
an argument is supplied.

If the argument is C<undef> it will search for an unallocated nbd-device
and use it.

=cut

sub new {
   my $class = shift;
   my $self = bless { @_ }, $class;

   $self->device (exists $self->{device} ? $self->{device} : undef);
   exists $self->{socket} and $self->socket ($self->{socket});
   
   $self;
}

sub socket {
   my $self = shift;

   if (@_) {
      $self->{socket} = $_[0];

      if (defined $self->{socket}) {
         my $fileno = $_[0] =~ /[^0-9]/ ? fileno $_[0] : $_[0];
         _set_sock fileno $self->{device_fd}, $fileno;
      } else {
         _clear_sock fileno $self->{device_fd};
      }
   }

   $self->{socket};
}

sub device {
   my $self = shift;

   if (@_) {
      my $device = shift;

      # try to load the module if the device nodes don't exist
      # might be better to handle this via mknod?
      -b "/dev/nbd0"
         or system "modprobe nbd >/dev/null 2>&1";

      if (defined $device) {
         open my $dev, "+<$device" or croak "$device: $!";
         $self->{device} = $device;
         $self->{device_fd} = $dev;
      } else {
        for (0..256) {
           $_ < 256 or croak "unable to find an available nbd device";

           my $path = "/dev/nbd$_";
           -e $path or system "mknod", $path, "b", 43, $_;
           open my $dev, "+<$path" or croak "$device: $!";
           _set_sock fileno $dev, -1;
           if ($!{EINVAL}) {
              $self->{device} = $path;
              $self->{device_fd} = $dev;
              last;
           } elsif ($!{EBUSY}) {
              next;
           } else {
              croak "$path: $!";
           }
        }
      }
   }

   $self->{device};
}

=item $client->disconnect

Tries to exit the server by sending a special disconnect message.

=item $client->clear_queue

Clears the request queue, if possible. Should be used before setting a new
socket.

=item $client->set_timeout ($timeout)

Set the request timeout, in seconds.

=item $client->set_blocksize ($blksize)

Set the device block size in bytes, i.e. how big each block is (must be
>512, <PAGESIZE and a power of two).

Also rounds down the device size to be a multiple of the block size.

=item $client->set_blocks ($nblocks)

Set the device size in block units.

=item $client->set_size ($bytes)

Set the device size in octet units, will be rounded down to be a multiple
of the block size.

=cut

sub disconnect {
   my $self = shift;

   _disconnect fileno $self->{device_fd};
}

sub clear_queue {
   my $self = shift;

   _clear_que fileno $self->{device_fd};
}

sub set_timeout {
   my $self = shift;
              
   _set_timeout fileno $self->{device_fd}, $_[0];
}

sub set_blocksize {
   my $self = shift;
              
   _set_blksize fileno $self->{device_fd}, $_[0];
}

sub set_size {
   my $self = shift;
              
   _set_size fileno $self->{device_fd}, $_[0];
}

sub set_blocks {
   my $self = shift;
              
   _set_size_blocks fileno $self->{device_fd}, $_[0];
}

sub print_debug {
   my $self = shift;
              
   _print_debug fileno $self->{device_fd};
}

=item $client->run

Closes all file descriptors except the server socket and enters
the service loop (waits for read/write requests on the device and
forwards them over the given socket). Only returns when somebody calls
C<disconnect> or the server is killed.

=item $pid = $client->run_async

Runs the service loop asynchronously and returns the pid of the newly
created service process.

=item $client->kill_async

Kills any running async service. Please note that this also kills the
socket, so you need to re-set the socket after this call.

=cut

sub run {
   my $self = shift;

   _doit fileno $self->{device_fd};
}

sub run_async {
   my $self = shift;

   $self->{pid} = fork;

   defined $self->{pid} or croak "fork: $!";
   return $self->{pid} if $self->{pid};

   _doit fileno $self->{device_fd}, 1;
}

sub kill_async {
   my $self = shift;

   if (my $pid = delete $self->{pid}) {
      #_clear_que fileno $self->{device_fd};
      #_disconnect fileno $self->{device_fd};
      #_clear_sock fileno $self->{device_fd};
      # just kill -9 it, seems to be safest (all other ways just oops sooner or later)
      kill 9, $pid;
   }
}

sub DESTROY {
   my $self = shift;

   $self->kill_async;
}

=cut

1;

=back

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.13
Committed:	Tue Sep 21 11:51:55 2010 UTC (16 years ago) by root
Branch:	MAIN
CVS Tags:	rel-1_0
Changes since 1.12:	+5 -0 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.9	Linux::NBD::Client - client (device) side of a network block device
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Linux::NBD::Client;
8
9			=head1 DESCRIPTION
10
11	root	1.4	WARNING: I talked to the author of the nbd driver because nbd is so
12			extremely racy (right now, stopping it often causes oopses, a server
13			crashing also often oopses etc..).
14
15			It turned out that he doesn't care at all and nbd is basically
16			unmaintained, so YMMV when using this module, especially when writing
17			servers.
18
19			He really should have said that on his nbd pages ;[.
20
21			OTOH, it works relatively reliable when you don't stop the servers, so
22			watch out and keep your fingers crossed.
23	root	1.1
24			=head1 METHODS
25
26			=over 4
27
28			=cut
29
30			package Linux::NBD::Client;
31
32	root	1.7	$VERSION = 0.21;
33	root	1.1
34			use Linux::NBD ();
35
36			use Carp qw(croak);
37			use Errno ();
38
39	root	1.12	=item $client = new Linux::NBD::Client [socket => $fh][, device => "/dev/nbdX"], ...
40	root	1.1
41			Create a new client.
42
43			Unless C<device> is given, an unused device node is looked up using the
44			C<device> method (this might result in an exception!).
45
46	root	1.10	=item $client->socket ([$tcp_socket])
47	root	1.1
48			Returns the current socket after setting a new one (if an argument is
49	root	1.10	supplied). The socket I<MUST> be a tcp socket. Believe me, bad things will
50			happen if not.
51	root	1.1
52			The special argument C<undef> will try to clear the socket, if any was
53			set.
54
55	root	1.10	=item $client->device ([$new_device])
56	root	1.1
57	root	1.12	Returns the current device node (e.g. C</dev/nbd2>) after setting a new one if
58	root	1.1	an argument is supplied.
59
60			If the argument is C<undef> it will search for an unallocated nbd-device
61			and use it.
62
63			=cut
64
65			sub new {
66			my $class = shift;
67			my $self = bless { @_ }, $class;
68
69			$self->device (exists $self->{device} ? $self->{device} : undef);
70	root	1.12	exists $self->{socket} and $self->socket ($self->{socket});
71	root	1.1
72			$self;
73			}
74
75			sub socket {
76			my $self = shift;
77
78			if (@_) {
79			$self->{socket} = $_[0];
80
81			if (defined $self->{socket}) {
82			my $fileno = $_[0] =~ /[^0-9]/ ? fileno $_[0] : $_[0];
83			_set_sock fileno $self->{device_fd}, $fileno;
84			} else {
85			_clear_sock fileno $self->{device_fd};
86			}
87			}
88
89			$self->{socket};
90			}
91
92			sub device {
93			my $self = shift;
94
95			if (@_) {
96			my $device = shift;
97
98	root	1.13	# try to load the module if the device nodes don't exist
99			# might be better to handle this via mknod?
100			-b "/dev/nbd0"
101			or system "modprobe nbd >/dev/null 2>&1";
102
103	root	1.1	if (defined $device) {
104			open my $dev, "+<$device" or croak "$device: $!";
105			$self->{device} = $device;
106			$self->{device_fd} = $dev;
107			} else {
108			for (0..256) {
109			$_ < 256 or croak "unable to find an available nbd device";
110
111	root	1.12	my $path = "/dev/nbd$_";
112	root	1.6	-e $path or system "mknod", $path, "b", 43, $_;
113	root	1.1	open my $dev, "+<$path" or croak "$device: $!";
114			_set_sock fileno $dev, -1;
115			if ($!{EINVAL}) {
116			$self->{device} = $path;
117			$self->{device_fd} = $dev;
118			last;
119			} elsif ($!{EBUSY}) {
120			next;
121			} else {
122			croak "$path: $!";
123			}
124			}
125			}
126			}
127
128			$self->{device};
129			}
130
131			=item $client->disconnect
132
133	root	1.10	Tries to exit the server by sending a special disconnect message.
134	root	1.1
135			=item $client->clear_queue
136
137			Clears the request queue, if possible. Should be used before setting a new
138			socket.
139
140	root	1.11	=item $client->set_timeout ($timeout)
141
142			Set the request timeout, in seconds.
143
144	root	1.10	=item $client->set_blocksize ($blksize)
145	root	1.1
146	root	1.11	Set the device block size in bytes, i.e. how big each block is (must be
147			>512, <PAGESIZE and a power of two).
148
149			Also rounds down the device size to be a multiple of the block size.
150	root	1.1
151	root	1.11	=item $client->set_blocks ($nblocks)
152	root	1.1
153	root	1.11	Set the device size in block units.
154	root	1.1
155	root	1.11	=item $client->set_size ($bytes)
156	root	1.1
157	root	1.11	Set the device size in octet units, will be rounded down to be a multiple
158			of the block size.
159	root	1.1
160			=cut
161
162			sub disconnect {
163			my $self = shift;
164
165			_disconnect fileno $self->{device_fd};
166			}
167
168			sub clear_queue {
169			my $self = shift;
170
171			_clear_que fileno $self->{device_fd};
172			}
173
174	root	1.11	sub set_timeout {
175			my $self = shift;
176
177			_set_timeout fileno $self->{device_fd}, $_[0];
178			}
179
180	root	1.1	sub set_blocksize {
181			my $self = shift;
182
183			_set_blksize fileno $self->{device_fd}, $_[0];
184			}
185
186			sub set_size {
187			my $self = shift;
188
189			_set_size fileno $self->{device_fd}, $_[0];
190			}
191
192			sub set_blocks {
193			my $self = shift;
194
195			_set_size_blocks fileno $self->{device_fd}, $_[0];
196			}
197
198	root	1.11	sub print_debug {
199			my $self = shift;
200
201			_print_debug fileno $self->{device_fd};
202			}
203
204	root	1.1	=item $client->run
205
206	root	1.11	Closes all file descriptors except the server socket and enters
207			the service loop (waits for read/write requests on the device and
208	root	1.10	forwards them over the given socket). Only returns when somebody calls
209			C<disconnect> or the server is killed.
210	root	1.1
211			=item $pid = $client->run_async
212
213			Runs the service loop asynchronously and returns the pid of the newly
214			created service process.
215
216			=item $client->kill_async
217
218	root	1.2	Kills any running async service. Please note that this also kills the
219			socket, so you need to re-set the socket after this call.
220	root	1.1
221			=cut
222
223			sub run {
224			my $self = shift;
225	root	1.11
226	root	1.1	_doit fileno $self->{device_fd};
227			}
228
229			sub run_async {
230			my $self = shift;
231
232			$self->{pid} = fork;
233	root	1.10
234	root	1.1	defined $self->{pid} or croak "fork: $!";
235	root	1.10	return $self->{pid} if $self->{pid};
236	root	1.1
237	root	1.10	_doit fileno $self->{device_fd}, 1;
238	root	1.1	}
239
240			sub kill_async {
241			my $self = shift;
242
243			if (my $pid = delete $self->{pid}) {
244	root	1.3	#_clear_que fileno $self->{device_fd};
245			#_disconnect fileno $self->{device_fd};
246			#_clear_sock fileno $self->{device_fd};
247	root	1.5	# just kill -9 it, seems to be safest (all other ways just oops sooner or later)
248			kill 9, $pid;
249	root	1.1	}
250			}
251
252			sub DESTROY {
253			my $self = shift;
254
255			$self->kill_async;
256			}
257
258			=cut
259
260			1;
261
262			=back
263
264			=head1 AUTHOR
265
266	root	1.8	Marc Lehmann <schmorp@schmorp.de>
267			http://home.schmorp.de/
268	root	1.1
269			=cut
270