[Twisted-Python] PcapIO

[Neil Blakey-Milner]

Hi again,

I'm currently using this PcapIO class in a traffic analyser, and thought
people might find it useful, possibly for inclusion in twisted.  It
relies on pylibpcap (http://pylibpcap.sourceforge.net/).  If interested,
it's easy enough to use the example code in the pylibpcap distribution
in your protocol's dataReceived.

Neil
-- 
Neil Blakey-Milner
nbm at mithrandr.moria.org
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#!/usr/local/bin/python
#
# Copyright (c) 2002 Neil Blakey-Milner
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# SUCH DAMAGE.
#

# system imports
import pcap
import sys

# Twisted Imports
from twisted.internet import abstract, protocol

# Sibling Imports
import pcapprotocol

class PcapIO(abstract.FileDescriptor):
    def __init__(self, protocol, dev):
        """Create me with a device dev to listen on.  Should probably
        accept files too, and allow choice of device promiscuity and
        snap lengths.
        """
        abstract.FileDescriptor.__init__(self)

        p = pcap.pcapObject()
        p.open_live(dev, 1600, 0, 100)
        p.setnonblock(1)

        self.fn = p.fileno()
        self.pcap = p
        self.protocol = protocol
        self.protocol.makeConnection(self)
        self.startReading()

    def fileno(self):
        return self.fn

    def doRead(self):
        try:
            output = self.pcap.next()
        except IOError, ioe:
            if ioe.args[0] == errno.EAGAIN:
                return
            else:
                return CONNECTION_LOST
        if not output:
            return CONNECTION_LOST
        self.protocol.dataReceived(output)

    def connectionLost(self, reason):
        self.protocol.connectionLost()