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NBDServer.py
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NBDServer.py
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import struct
import socket
class NBDServer(object):
NBD_CMD_READ = 0
NBD_CMD_WRITE = 1
NBD_CMD_DISC = 2
NBD_INIT_PASSWD = b'NBDMAGIC'
NBD_INIT_IHAVEOPT = b'IHAVEOPT'
NBD_CLISERV_MAGIC = bytes([0, 0x42, 0x02, 0x81, 0x86, 0x12, 0x53])
NBD_REPLY_MAGIC = 0x3e889045565a9
NBD_SIMPLE_REPLY_MAGIC = 0x67446698
NBD_REQUEST_MAGIC = 0x25609513
#handshake flags
NBD_FLAG_FIXED_NEWSTYLE = 1
NBD_FLAG_NO_ZEROES = 1<<1
#transmission flags
NBD_FLAG_HAS_FLAGS = 1
NBD_FLAG_READ_ONLY = 1<<1
NBD_FLAG_SEND_FLUSH = 1<<2
NBD_FLAG_SEND_FUA = 1<<3
NBD_FLAG_ROTATIONAL = 1<<4
NBD_FLAG_SEND_TRIM = 1<<5
NBD_FLAG_SEND_WRITE_ZEROES = 1<<6
NBD_FLAG_SEND_DF = 1<<7
NBD_FLAG_CAN_MULTI_CONN = 1<<8
NBD_FLAG_SEND_RESIZE = 1<<9
NBD_FLAG_SEND_CACHE = 1<<10
NBD_FLAG_SEND_FAST_ZERO = 1<<11
#option types
NBD_OPT_EXPORT_NAME = 1
NBD_OPT_ABORT = 2
NBD_OPT_LIST = 3
NBD_OPT_PEEK_EXPORT = 4
NBD_OPT_STARTTLS = 5
NBD_OPT_INFO = 6
NBD_OPT_GO = 7
NBD_OPT_STRUCTURED_REPLY = 8
NBD_OPT_LIST_META_CONTEXT = 9
NBD_OPT_SET_META_CONTEXT = 10
#option reply types
NBD_REP_ACK = 1
NBD_REP_SERVER = 2
NBD_REP_INFO = 3
NBD_REP_META_CONTEXT = 4
NBD_REP_ERR_UNSUP = 2**31 + 1
NBD_REP_ERR_POLICY = 2**31 + 2
NBD_REP_ERR_INVALID = 2**31 + 3
NBD_REP_ERR_PLATFORM = 2**31 + 4
NBD_REP_ERR_TLS_REQD = 2**31 + 5
NBD_REP_ERR_UNKNOWN = 2**31 + 6
NBD_REP_ERR_SHUTDOWN = 2**31 + 7
NBD_REP_ERR_BLOCK_SIZE_REQD = 2**31 + 8
NBD_REP_ERR_TOO_BIG = 2**31 + 9
#information types (for NBD_REP_INFO)
NBD_INFO_EXPORT = 0
NBD_INFO_NAME = 1
NBD_INFO_DESCRIPTION = 2
NBD_INFO_BLOCK_SIZE = 3
def __init__(self, **kwargs):
if (not "read" in kwargs) or (not "write" in kwargs) or (not "disksize" in kwargs):
raise ValueError()
self.debug = False
if "debug" in kwargs:
self.debug = kwargs["debug"]
self.read = kwargs["read"]
self.write = kwargs["write"]
self.disksize = kwargs["disksize"]
return
def handshake_oldstyle(self, conn, disksize):
conn.send(self.NBD_INIT_PASSWD)
conn.send(self.NBD_CLISERV_MAGIC)
conn.send(struct.pack('>Q', disksize))
conn.send(bytes(4)) #flags
conn.send(bytes(124)) #reserved
return
def handshake_fixednewstyle(self, conn, disksize):
transmissionflags = self.NBD_FLAG_HAS_FLAGS
handshakeflags = self.NBD_FLAG_FIXED_NEWSTYLE
conn.send(self.NBD_INIT_PASSWD)
conn.send(self.NBD_INIT_IHAVEOPT)
conn.send(struct.pack('>H', handshakeflags))
clientflags = struct.unpack('>I', conn.recv(4))[0]
if self.debug:
print(f'NBD client flags: {clientflags}')
while True:
clientihaveopts = conn.recv(8)
if clientihaveopts!=self.NBD_INIT_IHAVEOPT:
print(f'NBD client IHAVEOPT was nonsense: {clientihaveopts}')
clientopt = struct.unpack('>I', conn.recv(4))[0]
clientoptsize = struct.unpack('>I', conn.recv(4))[0]
if self.debug:
print(f'NBD client opt: {clientopt} size: {clientoptsize}')
clientoptparam = conn.recv(clientoptsize)
if self.debug:
print(f'NBD client opt param: {clientoptparam}')
if clientopt == self.NBD_OPT_EXPORT_NAME:
if self.debug:
print(f'NBD client sent NBD_OPT_EXPORT_NAME.')
conn.send(struct.pack('>Q', disksize))
conn.send(struct.pack('>H', transmissionflags)) #transmission flags
conn.send(bytes(124)) #reserved
break
else:
print(f'NBD replying NBD_REP_ERR_UNSUP at unknown client option: {clientopt}.')
conn.send(struct.pack(">Q", self.NBD_REPLY_MAGIC))
conn.send(struct.pack('>I', clientopt))
conn.send(struct.pack('>I', self.NBD_REP_ERR_UNSUP))
conn.send(bytes(4)) #reply length = 0
return
def server(self, host, port):
#FIXME: TCP_NODELAY
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
sock.bind((host, port))
sock.listen(1)
conn, addr = sock.accept()
with conn:
print(f'Client {addr} connected')
#self.handshake_oldstyle(conn, self.disksize)
self.handshake_fixednewstyle(conn, self.disksize)
sreq = '>IHHQQI'
while True:
#print(conn.recv(1))
(magic, cmdflags, cmdtype, handle, offset, length) = struct.unpack(sreq, conn.recv(struct.calcsize(sreq)))
if self.debug:
print(f'NBD req magic: {hex(magic)}, cmdflags: {cmdflags}, type: {cmdtype}, handle: {hex(handle)}, offset: {offset}, length: {length}.')
if magic != self.NBD_REQUEST_MAGIC:
print(f'NBD req wrong request magic: {magic}.')
break
if cmdtype == self.NBD_CMD_READ:
if self.debug:
print("NBD NBD_CMD_READ")
data = self.read(offset, length)
conn.send(struct.pack('>I', self.NBD_SIMPLE_REPLY_MAGIC))
conn.send(bytes(4)) #error
conn.send(struct.pack('>Q', handle))
conn.send(data)
elif cmdtype == self.NBD_CMD_WRITE:
if self.debug:
print("NBD NBD_CMD_WRITE")
data = bytearray()
while len(data) < length:
data += conn.recv(length-len(data))
self.write(offset, data)
conn.send(struct.pack('>I', self.NBD_SIMPLE_REPLY_MAGIC))
conn.send(bytes(4)) #error
conn.send(struct.pack('>Q', handle))
elif cmdtype == self.NBD_CMD_DISC:
if self.debug:
print("NBD NBD_CMD_DISC")
break
else:
print(f'NBD unsupported type: {cmdtype}.')
return