Ticket #8: autodiscovery2

diff --git a/generate-cert.sh b/generate-cert.sh
index 4daf76a..ce28e03 100755
--- a/generate-cert.sh
+++ b/generate-cert.sh
@@ -5,4 +5,5 @@ if [ ! -x /usr/bin/certtool ] ; then
 fi
 
 certtool --generate-privkey --outfile ca-key.pem
-certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca-cert.pem
\ No newline at end of file
+certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca-cert.pem
+
diff --git a/manage.py b/manage.py
old mode 100644
new mode 100755
diff --git a/pydra_server/cluster/master.py b/pydra_server/cluster/master.py
index 47bb2a6..fe5d612 100755
--- a/pydra_server/cluster/master.py
+++ b/pydra_server/cluster/master.py
@@ -46,6 +46,12 @@ import datetime
 
 from threading import Lock
 
+# should be executed before any other reactor stuff to prevent from using non
+# glib2 event loop which we need for dbus
+
+from twisted.internet import glib2reactor
+glib2reactor.install()
+
 from zope.interface import implements
 from twisted.cred import portal, checkers
 from twisted.spread import pb
@@ -56,6 +62,8 @@ from twisted.web import server, resource
 from twisted.cred import credentials
 from django.utils import simplejson
 import settings
+import dbus, avahi
+from dbus.mainloop.glib import DBusGMainLoop
 
 from pydra_server.models import Node, TaskInstance
 from pydra_server.cluster.constants import *
@@ -143,6 +151,66 @@ class Master(object):
 
         self.host = 'localhost'
         self.port = 18800
+        self.autodiscovery()
+
+    def autodiscovery(self, callback=None):
+        """
+        set up the dbus loop, and add the callbacks for adding nodes on the fly
+
+        based on http://avahi.org/wiki/PythonBrowseExample
+        """
+        def service_resolved(*args):
+            # at this point we have all the info about the node we need
+
+            #decode TXT record, dbus's array of array's of dbus.Byte
+            txt = ""
+            for c in args[9][0]: 
+                if c >= 32 and c < 127: 
+                    txt += "%c" % c 
+                else: 
+                    txt += "." 
+
+            # make sure we only accept nodes we haven't seen before this is NOT
+            # a security measure (the key verification still takes place), only
+            # intended to prevent multiple hosts from being discovered via
+            # different routes (for example over both ipv6 and ipv4)
+            from md5 import md5
+            for node in self.nodes.values():
+                if md5(str(node.pub_key)).hexdigest() == txt:
+                    return
+
+            # add the node (without the restart)
+            node = Node.objects.create(host=args[7], port=args[8])
+            self.nodes[node.id] = node
+            self.reconnect_nodes()
+
+        def print_error(*args):
+            logger.info("Couldn't resolve avahi name: %s" % str(args))
+
+        def node_found(interface, protocol, name, stype, domain, flags):
+            if flags & avahi.LOOKUP_RESULT_LOCAL:
+                    # local service, skip
+                    pass
+
+            server.ResolveService(interface, protocol, name, stype,
+                domain, avahi.PROTO_UNSPEC, dbus.UInt32(0),
+                reply_handler=service_resolved, error_handler=print_error)
+
+        # initialize dbus stuff needed for discovery
+        loop = DBusGMainLoop()
+
+        bus = dbus.SystemBus(mainloop=loop)
+
+        server = dbus.Interface( bus.get_object(avahi.DBUS_NAME, '/'),
+                'org.freedesktop.Avahi.Server')
+
+        sbrowser = dbus.Interface(bus.get_object(avahi.DBUS_NAME,
+                server.ServiceBrowserNew(avahi.IF_UNSPEC,
+                    avahi.PROTO_UNSPEC, '_pydra._tcp', 'local', dbus.UInt32(0))),
+                avahi.DBUS_INTERFACE_SERVICE_BROWSER)
+
+        sbrowser.connect_to_signal("ItemNew", node_found)
+
 
     def get_services(self):
         """
diff --git a/pydra_server/cluster/node.py b/pydra_server/cluster/node.py
index d4a727f..4eb9ce0 100755
--- a/pydra_server/cluster/node.py
+++ b/pydra_server/cluster/node.py
@@ -46,6 +46,8 @@ from twisted.application import service, internet
 
 import os
 from subprocess import Popen
+import platform, dbus, avahi
+from django.utils import simplejson
 from pydra_server.cluster.auth.rsa_auth import load_crypto
 from pydra_server.cluster.auth.master_avatar import MasterAvatar
 
@@ -55,6 +57,46 @@ import settings
 from pydra_server.logging.logger import init_logging
 logger = init_logging(settings.LOG_FILENAME_NODE)
 
+class ZeroconfService:
+    """A simple class to publish a network service with zeroconf using
+    avahi.
+
+    Shamelessly stolen from http://stackp.online.fr/?p=35 
+    """
+
+    def __init__(self, name, port, stype="_http._tcp",
+                 domain="", host="", text=""):
+        self.name = name
+        self.stype = stype
+        self.domain = domain
+        self.host = host
+        self.port = port
+        self.text = text
+
+    def publish(self):
+        bus = dbus.SystemBus()
+        server = dbus.Interface(
+                         bus.get_object(
+                                 avahi.DBUS_NAME,
+                                 avahi.DBUS_PATH_SERVER),
+                        avahi.DBUS_INTERFACE_SERVER)
+
+        g = dbus.Interface(
+                    bus.get_object(avahi.DBUS_NAME,
+                                   server.EntryGroupNew()),
+                    avahi.DBUS_INTERFACE_ENTRY_GROUP)
+
+        g.AddService(avahi.IF_UNSPEC, avahi.PROTO_UNSPEC,dbus.UInt32(0),
+                     self.name, self.stype, self.domain, self.host,
+                     dbus.UInt16(self.port), self.text)
+
+        g.Commit()
+        #import ipdb; ipdb.set_trace()
+        self.group = g
+
+    def unpublish(self):
+        self.group.Reset()
+
 
 class NodeServer:
     """
@@ -81,6 +123,18 @@ class NodeServer:
         # get information about the server
         self.determine_info()
 
+
+        # TXT record must be array of array of dbus.Byte, let's encode it
+        dbus_array = [] 
+        from md5 import md5
+
+        for c in md5(simplejson.dumps(self.pub_key)).hexdigest(): 
+            dbus_array.append(dbus.Byte(ord(c))) 
+        service = ZeroconfService(name=platform.node(), port=self.port,
+            stype="_pydra._tcp", text=[dbus_array])
+        service.publish()
+
+
         logger.info('Node - starting server on port %s' % self.port)
 
 
@@ -142,7 +196,6 @@ class NodeServer:
         Exchange public keys with the master.  This allows the Master
         to authenticate in the future using the keypair handshake
         """
-        from django.utils import simplejson
         from Crypto.PublicKey import RSA
         from twisted.conch.ssh.keys import Key
         import math