From ccfa43fcd5e7a63de86d926a28be80193f8eaad1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sergiusz=20Baza=C5=84ski?= <q3k@q3k.org>
Date: Wed, 14 Nov 2012 15:39:51 +0100
Subject: [PATCH] We actually need this.

---
 tftpy/TftpContexts.py | 239 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 239 insertions(+)
 create mode 100644 tftpy/TftpContexts.py

diff --git a/tftpy/TftpContexts.py b/tftpy/TftpContexts.py
new file mode 100644
index 0000000..b21c807
--- /dev/null
+++ b/tftpy/TftpContexts.py
@@ -0,0 +1,239 @@
+"""This module implements all contexts for state handling during uploads and
+downloads, the main interface to which being the TftpContext base class.
+
+The concept is simple. Each context object represents a single upload or
+download, and the state object in the context object represents the current
+state of that transfer. The state object has a handle() method that expects
+the next packet in the transfer, and returns a state object until the transfer
+is complete, at which point it returns None. That is, unless there is a fatal
+error, in which case a TftpException is returned instead."""
+
+from TftpShared import *
+from TftpPacketTypes import *
+from TftpPacketFactory import TftpPacketFactory
+from TftpStates import *
+import socket, time, sys
+
+###############################################################################
+# Utility classes
+###############################################################################
+
+class TftpMetrics(object):
+    """A class representing metrics of the transfer."""
+    def __init__(self):
+        # Bytes transferred
+        self.bytes = 0
+        # Bytes re-sent
+        self.resent_bytes = 0
+        # Duplicate packets received
+        self.dups = {}
+        self.dupcount = 0
+        # Times
+        self.start_time = 0
+        self.end_time = 0
+        self.duration = 0
+        # Rates
+        self.bps = 0
+        self.kbps = 0
+        # Generic errors
+        self.errors = 0
+
+    def compute(self):
+        # Compute transfer time
+        self.duration = self.end_time - self.start_time
+        if self.duration == 0:
+            self.duration = 1
+        log.debug("TftpMetrics.compute: duration is %s" % self.duration)
+        self.bps = (self.bytes * 8.0) / self.duration
+        self.kbps = self.bps / 1024.0
+        log.debug("TftpMetrics.compute: kbps is %s" % self.kbps)
+        for key in self.dups:
+            self.dupcount += self.dups[key]
+
+    def add_dup(self, pkt):
+        """This method adds a dup for a packet to the metrics."""
+        log.debug("Recording a dup of %s" % pkt)
+        s = str(pkt)
+        if self.dups.has_key(s):
+            self.dups[s] += 1
+        else:
+            self.dups[s] = 1
+        tftpassert(self.dups[s] < MAX_DUPS, "Max duplicates reached")
+
+###############################################################################
+# Context classes
+###############################################################################
+
+class TftpContext(object):
+    """The base class of the contexts."""
+
+    def __init__(self, host, port, timeout):
+        """Constructor for the base context, setting shared instance
+        variables."""
+        self.file_to_transfer = None
+        self.fileobj = None
+        self.options = None
+        self.packethook = None
+        self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        self.sock.settimeout(timeout)
+        self.timeout = timeout
+        self.state = None
+        self.next_block = 0
+        self.factory = TftpPacketFactory()
+        # Note, setting the host will also set self.address, as it's a property.
+        self.host = host
+        self.port = port
+        # The port associated with the TID
+        self.tidport = None
+        # Metrics
+        self.metrics = TftpMetrics()
+        # Fluag when the transfer is pending completion.
+        self.pending_complete = False
+        # Time when this context last received any traffic.
+        # FIXME: does this belong in metrics?
+        self.last_update = 0
+        # The last packet we sent, if applicable, to make resending easy.
+        self.last_pkt = None
+        # Count the number of retry attempts.
+        self.retry_count = 0
+
+    def getBlocksize(self):
+        """Fetch the current blocksize for this session."""
+        return int(self.options.get('blksize', 512))
+
+    def __del__(self):
+        """Simple destructor to try to call housekeeping in the end method if
+        not called explicitely. Leaking file descriptors is not a good
+        thing."""
+        self.end()
+
+    def checkTimeout(self, now):
+        """Compare current time with last_update time, and raise an exception
+        if we're over the timeout time."""
+        log.debug("checking for timeout on session %s" % self)
+        if now - self.last_update > self.timeout:
+            raise TftpTimeout, "Timeout waiting for traffic"
+
+    def start(self):
+        raise NotImplementedError, "Abstract method"
+
+    def end(self):
+        """Perform session cleanup, since the end method should always be
+        called explicitely by the calling code, this works better than the
+        destructor."""
+        log.debug("in TftpContext.end")
+        if self.fileobj is not None and not self.fileobj.closed:
+            log.debug("self.fileobj is open - closing")
+            self.fileobj.close()
+
+    def gethost(self):
+        "Simple getter method for use in a property."
+        return self.__host
+
+    def sethost(self, host):
+        """Setter method that also sets the address property as a result
+        of the host that is set."""
+        self.__host = host
+        self.address = socket.gethostbyname(host)
+
+    host = property(gethost, sethost)
+
+    def setNextBlock(self, block):
+        if block >= 2 ** 16:
+            log.debug("Block number rollover to 0 again")
+            block = 0
+        self.__eblock = block
+
+    def getNextBlock(self):
+        return self.__eblock
+
+    next_block = property(getNextBlock, setNextBlock)
+
+    def cycle(self):
+        """Here we wait for a response from the server after sending it
+        something, and dispatch appropriate action to that response."""
+        try:
+            (buffer, (raddress, rport)) = self.sock.recvfrom(MAX_BLKSIZE)
+        except socket.timeout:
+            log.warn("Timeout waiting for traffic, retrying...")
+            raise TftpTimeout, "Timed-out waiting for traffic"
+
+        # Ok, we've received a packet. Log it.
+        log.debug("Received %d bytes from %s:%s"
+                        % (len(buffer), raddress, rport))
+        # And update our last updated time.
+        self.last_update = time.time()
+
+        # Decode it.
+        recvpkt = self.factory.parse(buffer)
+
+        # Check for known "connection".
+        if raddress != self.address:
+            log.warn("Received traffic from %s, expected host %s. Discarding"
+                        % (raddress, self.host))
+
+        if self.tidport and self.tidport != rport:
+            log.warn("Received traffic from %s:%s but we're "
+                        "connected to %s:%s. Discarding."
+                        % (raddress, rport,
+                        self.host, self.tidport))
+
+        # If there is a packethook defined, call it. We unconditionally
+        # pass all packets, it's up to the client to screen out different
+        # kinds of packets. This way, the client is privy to things like
+        # negotiated options.
+        if self.packethook:
+            self.packethook(recvpkt)
+
+        # And handle it, possibly changing state.
+        self.state = self.state.handle(recvpkt, raddress, rport)
+        # If we didn't throw any exceptions here, reset the retry_count to
+        # zero.
+        self.retry_count = 0
+
+class TftpContextServer(TftpContext):
+    """The context for the server."""
+    def __init__(self, host, port, timeout, root, dyn_file_func=None):
+        TftpContext.__init__(self,
+                             host,
+                             port,
+                             timeout,
+                             )
+        # At this point we have no idea if this is a download or an upload. We
+        # need to let the start state determine that.
+        self.state = TftpStateServerStart(self)
+
+        self.root = root
+        self.dyn_file_func = dyn_file_func
+
+    def __str__(self):
+        return "%s:%s %s" % (self.host, self.port, self.state)
+
+    def start(self, buffer):
+        """Start the state cycle. Note that the server context receives an
+        initial packet in its start method. Also note that the server does not
+        loop on cycle(), as it expects the TftpServer object to manage
+        that."""
+        log.debug("In TftpContextServer.start")
+        self.metrics.start_time = time.time()
+        log.debug("Set metrics.start_time to %s" % self.metrics.start_time)
+        # And update our last updated time.
+        self.last_update = time.time()
+
+        pkt = self.factory.parse(buffer)
+        log.debug("TftpContextServer.start() - factory returned a %s" % pkt)
+
+        # Call handle once with the initial packet. This should put us into
+        # the download or the upload state.
+        self.state = self.state.handle(pkt,
+                                       self.host,
+                                       self.port)
+
+    def end(self):
+        """Finish up the context."""
+        TftpContext.end(self)
+        self.metrics.end_time = time.time()
+        log.debug("Set metrics.end_time to %s" % self.metrics.end_time)
+        self.metrics.compute()
+
+