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mountclient.py
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# Mount RPC client -- RFC 1094 (NFS), Appendix A # This module demonstrates how to write your own RPC client in Python. # When this example was written, there was no RPC compiler for # Python. Without such a compiler, you must first create classes # derived from Packer and Unpacker to handle the data types for the # server you want to interface to. You then write the client class. # If you want to support both the TCP and the UDP version of a # protocol, use multiple inheritance as shown below. import rpc from rpc import Packer, Unpacker, TCPClient, UDPClient # Program number and version for the mount protocol MOUNTPROG = 100005 MOUNTVERS = 1 # Size of the 'fhandle' opaque structure FHSIZE = 32 # Packer derived class for Mount protocol clients. # The only thing we need to pack beyond basic types is an 'fhandle' class MountPacker(Packer): def pack_fhandle(self, fhandle): self.pack_fopaque(FHSIZE, fhandle) # Unpacker derived class for Mount protocol clients. # The important types we need to unpack are fhandle, fhstatus, # mountlist and exportlist; mountstruct, exportstruct and groups are # used to unpack components of mountlist and exportlist and the # corresponding functions are passed as function argument to the # generic unpack_list function. class MountUnpacker(Unpacker): def unpack_fhandle(self): return self.unpack_fopaque(FHSIZE) def unpack_fhstatus(self): status = self.unpack_uint() if status == 0: fh = self.unpack_fhandle() else: fh = None return status, fh def unpack_mountlist(self): return self.unpack_list(self.unpack_mountstruct) def unpack_mountstruct(self): hostname = self.unpack_string() directory = self.unpack_string() return (hostname, directory) def unpack_exportlist(self): return self.unpack_list(self.unpack_exportstruct) def unpack_exportstruct(self): filesys = self.unpack_string() groups = self.unpack_groups() return (filesys, groups) def unpack_groups(self): return self.unpack_list(self.unpack_string) # These are the procedures specific to the Mount client class. # Think of this as a derived class of either TCPClient or UDPClient. class PartialMountClient: # This method is called by Client.__init__ to initialize # self.packer and self.unpacker def addpackers(self): self.packer = MountPacker() self.unpacker = MountUnpacker('') # This method is called by Client.__init__ to bind the socket # to a particular network interface and port. We use the # default network interface, but if we're running as root, # we want to bind to a reserved port def bindsocket(self): import os try: uid = os.getuid() except AttributeError: uid = 1 if uid == 0: port = rpc.bindresvport(self.sock, '') # 'port' is not used else: self.sock.bind(('', 0)) # This function is called to cough up a suitable # authentication object for a call to procedure 'proc'. def mkcred(self): if self.cred is None: self.cred = rpc.AUTH_UNIX, rpc.make_auth_unix_default() return self.cred # The methods Mnt, Dump etc. each implement one Remote # Procedure Call. This is done by calling self.make_call() # with as arguments: # # - the procedure number # - the arguments (or None) # - the "packer" function for the arguments (or None) # - the "unpacker" function for the return value (or None) # # The packer and unpacker function, if not None, *must* be # methods of self.packer and self.unpacker, respectively. # A value of None means that there are no arguments or is no # return value, respectively. # # The return value from make_call() is the return value from # the remote procedure call, as unpacked by the "unpacker" # function, or None if the unpacker function is None. # # (Even if you expect a result of None, you should still # return the return value from make_call(), since this may be # needed by a broadcasting version of the class.) # # If the call fails, make_call() raises an exception # (this includes time-outs and invalid results). # # Note that (at least with the UDP protocol) there is no # guarantee that a call is executed at most once. When you do # get a reply, you know it has been executed at least once; # when you don't get a reply, you know nothing. def Mnt(self, directory): return self.make_call(1, directory, \ self.packer.pack_string, \ self.unpacker.unpack_fhstatus) def Dump(self): return self.make_call(2, None, \ None, self.unpacker.unpack_mountlist) def Umnt(self, directory): return self.make_call(3, directory, \ self.packer.pack_string, None) def Umntall(self): return self.make_call(4, None, None, None) def Export(self): return self.make_call(5, None, \ None, self.unpacker.unpack_exportlist) # We turn the partial Mount client into a full one for either protocol # by use of multiple inheritance. (In general, when class C has base # classes B1...Bn, if x is an instance of class C, methods of x are # searched first in C, then in B1, then in B2, ..., finally in Bn.) class TCPMountClient(PartialMountClient, TCPClient): def __init__(self, host): TCPClient.__init__(self, host, MOUNTPROG, MOUNTVERS) class UDPMountClient(PartialMountClient, UDPClient): def __init__(self, host): UDPClient.__init__(self, host, MOUNTPROG, MOUNTVERS) # A little test program for the Mount client. This takes a host as # command line argument (default the local machine), prints its export # list, and attempts to mount and unmount each exported files system. # An optional first argument of -t or -u specifies the protocol to use # (TCP or UDP), default is UDP. def test(): import sys if sys.argv[1:] and sys.argv[1] == '-t': C = TCPMountClient del sys.argv[1] elif sys.argv[1:] and sys.argv[1] == '-u': C = UDPMountClient del sys.argv[1] else: C = UDPMountClient if sys.argv[1:]: host = sys.argv[1] else: host = '' mcl = C(host) list = mcl.Export() for item in list: print item try: mcl.Mnt(item[0]) except: print 'Sorry' continue mcl.Umnt(item[0])
