/
nbdserver.py
executable file
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/
nbdserver.py
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#!/usr/bin/python
from twisted.internet import protocol, endpoints, reactor, defer
from twisted.python import log
from zope.interface import Interface, Attribute, implements
import struct
import os
import argparse
from operator import itemgetter
NBD_REQUEST_MAGIC = 0x25609513
NBD_REPLY_MAGIC = 0x67446698
NBD_OPT_EXPORT_NAME = 1
NBD_CMD_READ = 0
NBD_CMD_WRITE = 1
NBD_CMD_DISC = 2
NBD_CMD_FLUSH = 3
NBD_CMD_TRIM = 4
class IBlockDevice(Interface):
size = Attribute("blocksize * nblocks")
flags = Attribute("NBD export flags")
def read(offset, length):
"""Read some data from the blockdev, return a str"""
def write(offset, data):
"""Write some data to the blockdev"""
class NBDRequestHeader(object):
hstruct = struct.Struct("!II8sQI")
size = hstruct.size
def __init__(self, data):
self.magic, self.requestType, self.handle, self.offset, self.length = self.hstruct.unpack(data)
def __repr__(self):
return "NBDRequestHeader(magic=%08x, requestType=%r, handle=%r offset=%r length=%r)" % (self.magic, self.requestType, self.handle, self.offset, self.length)
class NBDServer(protocol.Protocol):
flags = 0
def connectionMade(self):
# Initiate a new-new-style handshake
log.msg("Connection established")
self.transport.write("NBDMAGIC\x49\x48\x41\x56\x45\x4F\x50\x54\x00\x00")
self.state = self.initSent
def dataReceived(self, data):
"""Process the TCP stream and call requestReceived when
we have a complete request"""
if not hasattr(self, 'buf'):
self.buf = data
else:
self.buf += data
self.state()
def initSent(self):
if len(self.buf) < 4:
return
if self.buf[:4] != '\0\0\0\0':
log.msg("Only old-new handshakes supported")
self.transport.loseConnection()
return
self.buf = self.buf[4:]
log.msg("Negotiated old-new connection type")
self.state = self.receiveOpts
self.state()
def receiveOpts(self):
if len(self.buf) < 16:
log.msg("Incomplete magic received in opt")
return
if self.buf[:8] != '\x49\x48\x41\x56\x45\x4F\x50\x54':
log.msg("Invalid magic received")
self.transport.loseConnection()
return
(opt, length) = struct.unpack(">II", self.buf[8:16])
if len(self.buf) < 16 + length:
log.msg("Incomplete option received")
return
optData = self.buf[16:16+length]
self.buf = self.buf[16+length:]
if opt == NBD_OPT_EXPORT_NAME:
try:
self.bdev = self.factory.exports[optData]
reply = struct.pack(">QH124x", self.bdev.size, self.flags)
self.transport.write(reply)
log.msg("Export %r mounted by client" % optData)
self.state = self.dataPhase
self.state()
except KeyError:
log.msg("Export %r not available" % optData)
self.transport.loseConnection()
return
def dataPhase(self):
while len(self.buf) >= NBDRequestHeader.size:
header = NBDRequestHeader(self.buf[:NBDRequestHeader.size])
log.msg("Received %r" % header)
if header.requestType == NBD_CMD_WRITE:
if len(self.buf) < header.size + header.length:
log.msg("Incomplete write request received")
return
data = self.buf[header.size:header.size+header.length]
self.buf = self.buf[header.size+header.length:]
d = defer.maybeDeferred(self.bdev.write, header.offset, data)
d.addCallback(self.reply, header.handle)
d.addErrback(self.errorReply, header.handle)
elif header.requestType == NBD_CMD_READ:
self.buf = self.buf[header.size:]
d = defer.maybeDeferred(self.bdev.read, header.offset, header.length)
d.addCallback(self.reply, header.handle)
d.addErrback(self.errorReply, header.handle)
elif header.requestType == NBD_CMD_DISC:
self.transport.loseConnection()
return
else:
self.buf = self.buf[header.size:]
log.msg("Unsupported request type %d" % header.requestType)
self.transport.write(
struct.pack(">II8s",
NBD_REPLY_MAGIC,
1, # Operation not permitted
header.handle
)
)
def reply(self, data, handle):
reply = struct.pack(">II8s", NBD_REPLY_MAGIC, 0, handle)
if data is not None:
reply += data
self.transport.write(reply)
def errorReply(self, reason, handle):
log.err(reason)
reply = struct.pack(">II8s", NBD_REPLY_MAGIC, 5, handle)
self.transport.write(reply)
class NBDServerFactory(protocol.Factory):
protocol = NBDServer
def __init__(self, exports):
self.exports = exports
class FileBlockDevice(object):
implements(IBlockDevice)
def __init__(self, filename, readOnly=False):
if readOnly:
mode = "rb"
self.flags = 3
else:
mode = "rb+"
self.flags = 1
self.fp = open(filename, mode)
s = os.fstat(self.fp.fileno())
self.size = s.st_size
def read(self, offset, length):
self.fp.seek(offset)
return self.fp.read(length)
def write(self, offset, data):
self.fp.seek(offset)
self.fp.write(data)
self.fp.flush()
def main():
import argparse
import sys
def serverEndpoint(x):
return endpoints.serverFromString(reactor, x)
def listenFailed(reason):
log.err(reason)
reactor.stop()
def serverListening(_):
log.msg("NBD Server running")
log.startLogging(sys.stderr)
parser = argparse.ArgumentParser(description='NBD Server')
parser.add_argument('--listen',
help='Endpoint address to listen on',
type=serverEndpoint,
default='tcp:10809:interface=127.0.0.1')
parser.add_argument('--readonly',
help='Make the export read-only',
action='store_true')
parser.add_argument('filename',
help='File to serve')
args = parser.parse_args()
bdev = FileBlockDevice(args.filename, args.readonly)
f = NBDServerFactory({os.path.basename(args.filename): bdev})
d = args.listen.listen(f)
d.addErrback(listenFailed)
d.addCallback(serverListening)
reactor.run()
if __name__ == "__main__":
main()