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=head1 NAME |
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Linux::NBD::Client - client (device) side of a network block device |
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|
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=head1 SYNOPSIS |
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|
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use Linux::NBD::Client; |
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|
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=head1 DESCRIPTION |
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|
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WARNING: I talked to the author of the nbd driver because nbd is so |
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extremely racy (right now, stopping it often causes oopses, a server |
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crashing also often oopses etc..). |
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|
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It turned out that he doesn't care at all and nbd is basically |
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unmaintained, so YMMV when using this module, especially when writing |
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servers. |
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|
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He really should have said that on his nbd pages ;[. |
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|
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OTOH, it works relatively reliable when you don't stop the servers, so |
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watch out and keep your fingers crossed. |
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|
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=head1 METHODS |
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|
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=over 4 |
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|
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=cut |
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|
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package Linux::NBD::Client; |
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|
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$VERSION = 0.22; |
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|
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use Linux::NBD (); |
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|
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use Carp qw(croak); |
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use Errno (); |
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|
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=item $client = new Linux::NBD::Client [socket => $fh][, device => "/dev/nbdX"], ... |
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Create a new client. |
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|
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Unless C<device> is given, an unused device node is looked up using the |
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C<device> method (this might result in an exception!). |
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|
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=item $client->socket ([$tcp_socket]) |
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Returns the current socket after setting a new one (if an argument is |
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supplied). The socket I<MUST> be a tcp socket. Believe me, bad things will |
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happen if not. |
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|
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The special argument C<undef> will try to clear the socket, if any was |
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set. |
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|
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=item $client->device ([$new_device]) |
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Returns the current device node (e.g. C</dev/nbd2>) after setting a new one if |
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an argument is supplied. |
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|
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If the argument is C<undef> it will search for an unallocated nbd-device |
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and use it. |
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|
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=cut |
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|
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sub new { |
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my $class = shift; |
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my $self = bless { @_ }, $class; |
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|
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$self->device (exists $self->{device} ? $self->{device} : undef); |
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exists $self->{socket} and $self->socket ($self->{socket}); |
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|
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$self; |
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} |
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|
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sub socket { |
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my $self = shift; |
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|
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if (@_) { |
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$self->{socket} = $_[0]; |
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|
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if (defined $self->{socket}) { |
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my $fileno = $_[0] =~ /[^0-9]/ ? fileno $_[0] : $_[0]; |
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_set_sock fileno $self->{device_fd}, $fileno; |
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} else { |
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_clear_sock fileno $self->{device_fd}; |
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} |
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} |
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|
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$self->{socket}; |
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} |
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|
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sub device { |
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my $self = shift; |
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|
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if (@_) { |
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my $device = shift; |
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|
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# try to load the module if the device nodes don't exist |
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# might be better to handle this via mknod? |
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-b "/dev/nbd0" |
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or system "modprobe nbd >/dev/null 2>&1"; |
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|
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if (defined $device) { |
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open my $dev, "+<$device" or croak "$device: $!"; |
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$self->{device} = $device; |
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$self->{device_fd} = $dev; |
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} else { |
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for (0..256) { |
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$_ < 256 or croak "unable to find an available nbd device"; |
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|
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my $path = "/dev/nbd$_"; |
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-e $path or system "mknod", $path, "b", 43, $_; |
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open my $dev, "+<$path" or croak "$device: $!"; |
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_set_sock fileno $dev, -1; |
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if ($!{EINVAL}) { |
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$self->{device} = $path; |
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$self->{device_fd} = $dev; |
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last; |
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} elsif ($!{EBUSY}) { |
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next; |
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} else { |
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croak "$path: $!"; |
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} |
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} |
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} |
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} |
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|
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$self->{device}; |
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} |
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|
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=item $client->disconnect |
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Tries to exit the server by sending a special disconnect message. |
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=item $client->clear_queue |
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Clears the request queue, if possible. Should be used before setting a new |
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socket. |
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=item $client->set_timeout ($timeout) |
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Set the request timeout, in seconds. |
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=item $client->set_blocksize ($blksize) |
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Set the device block size in bytes, i.e. how big each block is (must be |
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>512, <PAGESIZE and a power of two). |
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Also rounds down the device size to be a multiple of the block size. |
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=item $client->set_blocks ($nblocks) |
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Set the device size in block units. |
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|
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=item $client->set_size ($bytes) |
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Set the device size in octet units, will be rounded down to be a multiple |
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of the block size. |
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|
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=item $client->set_flags ($flags) |
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|
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Set flags (NBD_FLAG_*) on the device. |
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|
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=cut |
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|
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sub disconnect { |
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my $self = shift; |
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|
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_disconnect fileno $self->{device_fd}; |
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} |
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|
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sub clear_queue { |
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my $self = shift; |
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|
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_clear_que fileno $self->{device_fd}; |
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} |
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|
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sub set_timeout { |
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my $self = shift; |
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|
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_set_timeout fileno $self->{device_fd}, $_[0]; |
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} |
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|
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sub set_blocksize { |
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my $self = shift; |
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|
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_set_blksize fileno $self->{device_fd}, $_[0]; |
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} |
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sub set_size { |
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my $self = shift; |
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_set_size fileno $self->{device_fd}, $_[0]; |
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} |
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sub set_blocks { |
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my $self = shift; |
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_set_size_blocks fileno $self->{device_fd}, $_[0]; |
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} |
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sub set_flags { |
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my $self = shift; |
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_set_flags fileno $self->{device_fd}, $_[0]; |
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} |
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sub print_debug { |
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my $self = shift; |
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_print_debug fileno $self->{device_fd}; |
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} |
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=item $client->run |
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Closes all file descriptors except the server socket and enters |
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the service loop (waits for read/write requests on the device and |
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forwards them over the given socket). Only returns when somebody calls |
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C<disconnect> or the server is killed. |
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=item $pid = $client->run_async |
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Runs the service loop asynchronously and returns the pid of the newly |
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created service process. |
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=item $client->kill_async |
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Kills any running async service. Please note that this also kills the |
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socket, so you need to re-set the socket after this call. |
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|
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=cut |
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sub run { |
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my $self = shift; |
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_doit fileno $self->{device_fd}; |
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} |
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sub run_async { |
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my $self = shift; |
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$self->{pid} = fork; |
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defined $self->{pid} or croak "fork: $!"; |
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return $self->{pid} if $self->{pid}; |
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_doit fileno $self->{device_fd}, 1; |
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} |
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sub kill_async { |
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my $self = shift; |
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|
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if (my $pid = delete $self->{pid}) { |
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#_clear_que fileno $self->{device_fd}; |
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#_disconnect fileno $self->{device_fd}; |
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#_clear_sock fileno $self->{device_fd}; |
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# just kill -9 it, seems to be safest (all other ways just oops sooner or later) |
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kill 9, $pid; |
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} |
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} |
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|
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sub DESTROY { |
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my $self = shift; |
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$self->kill_async; |
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} |
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|
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=cut |
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1; |
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|
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=back |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
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=cut |
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|
