240 lines
8.8 KiB
Python
240 lines
8.8 KiB
Python
"""This module implements all contexts for state handling during uploads and
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downloads, the main interface to which being the TftpContext base class.
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The concept is simple. Each context object represents a single upload or
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download, and the state object in the context object represents the current
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state of that transfer. The state object has a handle() method that expects
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the next packet in the transfer, and returns a state object until the transfer
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is complete, at which point it returns None. That is, unless there is a fatal
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error, in which case a TftpException is returned instead."""
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from TftpShared import *
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from TftpPacketTypes import *
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from TftpPacketFactory import TftpPacketFactory
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from TftpStates import *
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import socket, time, sys
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###############################################################################
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# Utility classes
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###############################################################################
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class TftpMetrics(object):
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"""A class representing metrics of the transfer."""
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def __init__(self):
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# Bytes transferred
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self.bytes = 0
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# Bytes re-sent
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self.resent_bytes = 0
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# Duplicate packets received
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self.dups = {}
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self.dupcount = 0
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# Times
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self.start_time = 0
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self.end_time = 0
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self.duration = 0
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# Rates
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self.bps = 0
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self.kbps = 0
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# Generic errors
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self.errors = 0
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def compute(self):
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# Compute transfer time
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self.duration = self.end_time - self.start_time
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if self.duration == 0:
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self.duration = 1
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log.debug("TftpMetrics.compute: duration is %s" % self.duration)
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self.bps = (self.bytes * 8.0) / self.duration
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self.kbps = self.bps / 1024.0
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log.debug("TftpMetrics.compute: kbps is %s" % self.kbps)
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for key in self.dups:
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self.dupcount += self.dups[key]
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def add_dup(self, pkt):
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"""This method adds a dup for a packet to the metrics."""
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log.debug("Recording a dup of %s" % pkt)
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s = str(pkt)
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if self.dups.has_key(s):
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self.dups[s] += 1
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else:
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self.dups[s] = 1
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tftpassert(self.dups[s] < MAX_DUPS, "Max duplicates reached")
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###############################################################################
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# Context classes
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###############################################################################
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class TftpContext(object):
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"""The base class of the contexts."""
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def __init__(self, host, port, timeout):
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"""Constructor for the base context, setting shared instance
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variables."""
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self.file_to_transfer = None
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self.fileobj = None
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self.options = None
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self.packethook = None
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self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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self.sock.settimeout(timeout)
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self.timeout = timeout
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self.state = None
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self.next_block = 0
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self.factory = TftpPacketFactory()
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# Note, setting the host will also set self.address, as it's a property.
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self.host = host
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self.port = port
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# The port associated with the TID
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self.tidport = None
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# Metrics
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self.metrics = TftpMetrics()
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# Fluag when the transfer is pending completion.
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self.pending_complete = False
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# Time when this context last received any traffic.
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# FIXME: does this belong in metrics?
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self.last_update = 0
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# The last packet we sent, if applicable, to make resending easy.
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self.last_pkt = None
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# Count the number of retry attempts.
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self.retry_count = 0
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def getBlocksize(self):
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"""Fetch the current blocksize for this session."""
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return int(self.options.get('blksize', 512))
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def __del__(self):
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"""Simple destructor to try to call housekeeping in the end method if
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not called explicitely. Leaking file descriptors is not a good
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thing."""
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self.end()
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def checkTimeout(self, now):
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"""Compare current time with last_update time, and raise an exception
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if we're over the timeout time."""
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log.debug("checking for timeout on session %s" % self)
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if now - self.last_update > self.timeout:
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raise TftpTimeout, "Timeout waiting for traffic"
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def start(self):
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raise NotImplementedError, "Abstract method"
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def end(self):
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"""Perform session cleanup, since the end method should always be
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called explicitely by the calling code, this works better than the
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destructor."""
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log.debug("in TftpContext.end")
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if self.fileobj is not None and not self.fileobj.closed:
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log.debug("self.fileobj is open - closing")
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self.fileobj.close()
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def gethost(self):
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"Simple getter method for use in a property."
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return self.__host
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def sethost(self, host):
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"""Setter method that also sets the address property as a result
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of the host that is set."""
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self.__host = host
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self.address = socket.gethostbyname(host)
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host = property(gethost, sethost)
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def setNextBlock(self, block):
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if block >= 2 ** 16:
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log.debug("Block number rollover to 0 again")
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block = 0
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self.__eblock = block
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def getNextBlock(self):
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return self.__eblock
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next_block = property(getNextBlock, setNextBlock)
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def cycle(self):
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"""Here we wait for a response from the server after sending it
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something, and dispatch appropriate action to that response."""
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try:
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(buffer, (raddress, rport)) = self.sock.recvfrom(MAX_BLKSIZE)
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except socket.timeout:
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log.warn("Timeout waiting for traffic, retrying...")
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raise TftpTimeout, "Timed-out waiting for traffic"
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# Ok, we've received a packet. Log it.
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log.debug("Received %d bytes from %s:%s"
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% (len(buffer), raddress, rport))
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# And update our last updated time.
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self.last_update = time.time()
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# Decode it.
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recvpkt = self.factory.parse(buffer)
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# Check for known "connection".
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if raddress != self.address:
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log.warn("Received traffic from %s, expected host %s. Discarding"
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% (raddress, self.host))
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if self.tidport and self.tidport != rport:
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log.warn("Received traffic from %s:%s but we're "
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"connected to %s:%s. Discarding."
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% (raddress, rport,
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self.host, self.tidport))
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# If there is a packethook defined, call it. We unconditionally
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# pass all packets, it's up to the client to screen out different
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# kinds of packets. This way, the client is privy to things like
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# negotiated options.
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if self.packethook:
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self.packethook(recvpkt)
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# And handle it, possibly changing state.
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self.state = self.state.handle(recvpkt, raddress, rport)
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# If we didn't throw any exceptions here, reset the retry_count to
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# zero.
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self.retry_count = 0
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class TftpContextServer(TftpContext):
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"""The context for the server."""
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def __init__(self, host, port, timeout, root, dyn_file_func=None):
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TftpContext.__init__(self,
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host,
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port,
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timeout,
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)
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# At this point we have no idea if this is a download or an upload. We
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# need to let the start state determine that.
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self.state = TftpStateServerStart(self)
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self.root = root
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self.dyn_file_func = dyn_file_func
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def __str__(self):
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return "%s:%s %s" % (self.host, self.port, self.state)
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def start(self, buffer):
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"""Start the state cycle. Note that the server context receives an
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initial packet in its start method. Also note that the server does not
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loop on cycle(), as it expects the TftpServer object to manage
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that."""
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log.debug("In TftpContextServer.start")
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self.metrics.start_time = time.time()
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log.debug("Set metrics.start_time to %s" % self.metrics.start_time)
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# And update our last updated time.
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self.last_update = time.time()
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pkt = self.factory.parse(buffer)
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log.debug("TftpContextServer.start() - factory returned a %s" % pkt)
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# Call handle once with the initial packet. This should put us into
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# the download or the upload state.
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self.state = self.state.handle(pkt,
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self.host,
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self.port)
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def end(self):
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"""Finish up the context."""
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TftpContext.end(self)
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self.metrics.end_time = time.time()
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log.debug("Set metrics.end_time to %s" % self.metrics.end_time)
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self.metrics.compute()
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