From 0df4bcb1d6d5b19f157979a79986059a90b614ea Mon Sep 17 00:00:00 2001
From: Max Khon <fjoe@samodelkin.net>
Date: Thu, 8 Aug 2019 14:07:26 +0700
Subject: [PATCH] recv_pdu() receives up to 1024 bytes at once from the agentx
 socket into a parsing buffer. Then the buffer is interpreted as a single PDU
 even if the buffer contained more than one PDU.

Fix this by using payload_length field of AgentX PDU header and
saving remaining unparsed buffer for the next recv_pdu() call.
---
 pyagentx/network.py | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/pyagentx/network.py b/pyagentx/network.py
index 9711398..c1d2370 100644
--- a/pyagentx/network.py
+++ b/pyagentx/network.py
@@ -14,6 +14,7 @@ def emit(self, record):
 import time
 import threading
 import Queue
+import struct
 
 import pyagentx
 from pyagentx.pdu import PDU
@@ -27,6 +28,7 @@ def __init__(self, queue, oid_list, sethandlers):
         self._queue = queue
         self._oid_list = oid_list
         self._sethandlers = sethandlers
+        self._recv_buf = ''
 
         self.session_id = 0
         self.transaction_id = 0
@@ -65,11 +67,18 @@ def send_pdu(self, pdu):
         self.socket.send(pdu.encode())
         
     def recv_pdu(self):
-        buf = self.socket.recv(1024)
-        if not buf: return None
+        if len(self._recv_buf) < 20:
+            self._recv_buf += self.socket.recv(1024)
+            if len(self._recv_buf) < 20:
+                return None
+        payload_len = struct.unpack('!L', self._recv_buf[16:20])[0]
+        logger.debug('buffer length {}, pdu length {}'.format(len(self._recv_buf), 20+payload_len))
         pdu = PDU()
-        pdu.decode(buf)
+        pdu.decode(self._recv_buf[:20+payload_len])
+        self._recv_buf = self._recv_buf[20+payload_len:]
         if self.debug: pdu.dump()
+        if len(self._recv_buf) > 0:
+            logger.debug('remaining buffer length {}'.format(len(self._recv_buf)))
         return pdu