From 49466002623d57e8bcdd1beb6b044448535f03ba Mon Sep 17 00:00:00 2001
From: a3284642 <a3284642@trbvm.com>
Date: Thu, 18 Sep 2014 22:40:23 +0000
Subject: [PATCH] Update class_receiveDataThread.py

Modified code so that clients send out their inventory lists with the the objects with the most proof of work first. The purpose is to ensure that a small minority of users contributing a relatively low amount of computational resources will not be able to DOS the network because their low proof of work messages are likely to be the last ones delivered and the first ones delayed past object expiration, as discussed here: https://bitmessage.org/forum/index.php?topic=4067.150
---
 src/class_receiveDataThread.py | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/class_receiveDataThread.py b/src/class_receiveDataThread.py
index 879faff6..bf65c4f8 100644
--- a/src/class_receiveDataThread.py
+++ b/src/class_receiveDataThread.py
@@ -276,15 +276,17 @@ class receiveDataThread(threading.Thread):
         # Select all hashes which are younger than two days old and in this
         # stream.
         queryreturn = sqlQuery(
-            '''SELECT hash FROM inventory WHERE ((receivedtime>? and objecttype<>'pubkey') or (receivedtime>? and objecttype='pubkey')) and streamnumber=?''',
+            '''SELECT hash, payload FROM inventory WHERE ((receivedtime>? and objecttype<>'pubkey') or (receivedtime>? and objecttype='pubkey')) and streamnumber=?''',
             int(time.time()) - shared.maximumAgeOfObjectsThatIAdvertiseToOthers,
             int(time.time()) - shared.lengthOfTimeToHoldOnToAllPubkeys,
             self.streamNumber)
         bigInvList = {}
         for row in queryreturn:
-            hash, = row
+            hash, payload = row
             if hash not in self.someObjectsOfWhichThisRemoteNodeIsAlreadyAware:
-                bigInvList[hash] = 0
+		POW, = unpack('>Q', hashlib.sha512(hashlib.sha512(payload[
+		:8] + hashlib.sha512(payload[8:]).digest()).digest()).digest()[0:8]) #check POW
+                bigInvList[hash] = POW
         # We also have messages in our inventory in memory (which is a python
         # dictionary). Let's fetch those too.
         with shared.inventoryLock:
@@ -292,12 +294,14 @@ class receiveDataThread(threading.Thread):
                 if hash not in self.someObjectsOfWhichThisRemoteNodeIsAlreadyAware:
                     objectType, streamNumber, payload, receivedTime, tag = storedValue
                     if streamNumber == self.streamNumber and receivedTime > int(time.time()) - shared.maximumAgeOfObjectsThatIAdvertiseToOthers:
-                        bigInvList[hash] = 0
+			POW, = unpack('>Q', hashlib.sha512(hashlib.sha512(payload[
+			:8] + hashlib.sha512(payload[8:]).digest()).digest()).digest()[0:8]) #check POW
+                        bigInvList[hash] = POW
         numberOfObjectsInInvMessage = 0
         payload = ''
         # Now let us start appending all of these hashes together. They will be
-        # sent out in a big inv message to our new peer.
-        for hash, storedValue in bigInvList.items():
+        # sent out in a big inv message to our new peer in POW order
+        for hash in sorted(bigInvList, key=bigInvList.__getitem__):
             payload += hash
             numberOfObjectsInInvMessage += 1
             if numberOfObjectsInInvMessage == 50000:  # We can only send a max of 50000 items per inv message but we may have more objects to advertise. They must be split up into multiple inv messages.