From a0fd414a38cc6cf7d342974eea9a0f8f9d55799a Mon Sep 17 00:00:00 2001
From: elie <elie>
Date: Wed, 7 Jan 2015 10:28:09 +0000
Subject: first attempt to make SNMP Engine settings persistent across reboots

---
 CHANGES                 |  2 ++
 pysnmp/entity/engine.py | 36 +++++++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index 034d18f..1ce6719 100644
--- a/CHANGES
+++ b/CHANGES
@@ -62,6 +62,8 @@ Revision 4.2.6rc0
   startup time.
 - Multiple fixes to verify pyasn1 decoder.decode() return to withstand
   broken SNMP messages or its components.
+- First attempt made to make some of SNMP Engine settings persistent
+  across reboots.
 - Fix to authoritative engine side snmpEngineID discovery procedure: 
   respond with notInTimeWindows rather then with unsupportedSecurityLevel
   at time synchronization phase.
diff --git a/pysnmp/entity/engine.py b/pysnmp/entity/engine.py
index a497e48..6076e19 100644
--- a/pysnmp/entity/engine.py
+++ b/pysnmp/entity/engine.py
@@ -1,4 +1,6 @@
 # SNMP engine
+import os
+import tempfile
 from pysnmp.proto.rfc3412 import MsgAndPduDispatcher
 from pysnmp.proto.mpmod.rfc2576 import SnmpV1MessageProcessingModel, \
      SnmpV2cMessageProcessingModel
@@ -8,6 +10,7 @@ from pysnmp.proto.secmod.rfc2576 import SnmpV1SecurityModel, \
 from pysnmp.proto.secmod.rfc3414 import SnmpUSMSecurityModel
 from pysnmp.proto.acmod import rfc3415, void
 from pysnmp.entity import observer
+from pysnmp import debug
 from pysnmp import error
 
 class SnmpEngine:
@@ -50,9 +53,40 @@ class SnmpEngine:
         snmpEngineBoots, = self.msgAndPduDsp.mibInstrumController.mibBuilder.importSymbols('__SNMP-FRAMEWORK-MIB', 'snmpEngineBoots')
         snmpEngineBoots.syntax = snmpEngineBoots.syntax + 1        
         origSnmpEngineID, = self.msgAndPduDsp.mibInstrumController.mibBuilder.importSymbols('__SNMP-FRAMEWORK-MIB', 'snmpEngineID')
+
         if snmpEngineID is not None:
             origSnmpEngineID.syntax = origSnmpEngineID.syntax.clone(snmpEngineID)
-        self.snmpEngineID = origSnmpEngineID.syntax
+            self.snmpEngineID = origSnmpEngineID.syntax
+
+            debug.logger & debug.flagApp and debug.logger('SnmpEngine: using custom SNMP Engine ID: %s' % self.snmpEngineID.prettyPrint())
+
+            # Attempt to make some of snmp Engine settings persistent.
+            # This should probably be generalized as a non-volatile MIB store.
+
+            persistentPath = os.path.join(tempfile.gettempdir(), '__pysnmp', self.snmpEngineID.prettyPrint())
+
+            debug.logger & debug.flagApp and debug.logger('SnmpEngine: using persistent directory: %s' % persistentPath)
+
+            if not os.path.exists(persistentPath):
+                try:
+                    os.makedirs(persistentPath)
+                except OSError:
+                    return
+
+            f = os.path.join(persistentPath, 'boots')
+            try:
+                snmpEngineBoots.syntax = snmpEngineBoots.syntax.clone(open(f).read())
+            except:
+                pass
+
+            snmpEngineBoots.syntax = snmpEngineBoots.syntax + 1
+
+            try:
+                open(f, 'w').write(snmpEngineBoots.syntax.prettyPrint())
+            except:
+                pass
+
+            debug.logger & debug.flagApp and debug.logger('SnmpEngine: stored SNMP Engine Boots: %s' % snmpEngineBoots.syntax.prettyPrint())
 
     # Transport dispatcher bindings
     
-- 
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