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 = 0.22;

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.

=item $client->set_flags ($flags)

Set flags (NBD_FLAG_*) on the device.

=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 set_flags {
   my $self = shift;
              
   _set_flags 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:	1.14
Committed:	Tue May 30 03:58:30 2017 UTC (9 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.13:	+11 -1 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	1.14	$VERSION = 0.22;
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	root	1.14	=item $client->set_flags ($flags)
161
162			Set flags (NBD_FLAG_*) on the device.
163
164	root	1.1	=cut
165
166			sub disconnect {
167			my $self = shift;
168
169			_disconnect fileno $self->{device_fd};
170			}
171
172			sub clear_queue {
173			my $self = shift;
174
175			_clear_que fileno $self->{device_fd};
176			}
177
178	root	1.11	sub set_timeout {
179			my $self = shift;
180
181			_set_timeout fileno $self->{device_fd}, $_[0];
182			}
183
184	root	1.1	sub set_blocksize {
185			my $self = shift;
186
187			_set_blksize fileno $self->{device_fd}, $_[0];
188			}
189
190			sub set_size {
191			my $self = shift;
192
193			_set_size fileno $self->{device_fd}, $_[0];
194			}
195
196			sub set_blocks {
197			my $self = shift;
198
199			_set_size_blocks fileno $self->{device_fd}, $_[0];
200			}
201
202	root	1.14	sub set_flags {
203			my $self = shift;
204
205			_set_flags fileno $self->{device_fd}, $_[0];
206			}
207
208	root	1.11	sub print_debug {
209			my $self = shift;
210
211			_print_debug fileno $self->{device_fd};
212			}
213
214	root	1.1	=item $client->run
215
216	root	1.11	Closes all file descriptors except the server socket and enters
217			the service loop (waits for read/write requests on the device and
218	root	1.10	forwards them over the given socket). Only returns when somebody calls
219			C<disconnect> or the server is killed.
220	root	1.1
221			=item $pid = $client->run_async
222
223			Runs the service loop asynchronously and returns the pid of the newly
224			created service process.
225
226			=item $client->kill_async
227
228	root	1.2	Kills any running async service. Please note that this also kills the
229			socket, so you need to re-set the socket after this call.
230	root	1.1
231			=cut
232
233			sub run {
234			my $self = shift;
235	root	1.11
236	root	1.1	_doit fileno $self->{device_fd};
237			}
238
239			sub run_async {
240			my $self = shift;
241
242			$self->{pid} = fork;
243	root	1.10
244	root	1.1	defined $self->{pid} or croak "fork: $!";
245	root	1.10	return $self->{pid} if $self->{pid};
246	root	1.1
247	root	1.10	_doit fileno $self->{device_fd}, 1;
248	root	1.1	}
249
250			sub kill_async {
251			my $self = shift;
252
253			if (my $pid = delete $self->{pid}) {
254	root	1.3	#_clear_que fileno $self->{device_fd};
255			#_disconnect fileno $self->{device_fd};
256			#_clear_sock fileno $self->{device_fd};
257	root	1.5	# just kill -9 it, seems to be safest (all other ways just oops sooner or later)
258			kill 9, $pid;
259	root	1.1	}
260			}
261
262			sub DESTROY {
263			my $self = shift;
264
265			$self->kill_async;
266			}
267
268			=cut
269
270			1;
271
272			=back
273
274			=head1 AUTHOR
275
276	root	1.8	Marc Lehmann <schmorp@schmorp.de>
277			http://home.schmorp.de/
278	root	1.1
279			=cut
280