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Re: [lwip-users] Incorrect RequestID field in SNMP response message


From: Frédéric BERNON
Subject: Re: [lwip-users] Incorrect RequestID field in SNMP response message
Date: Sun, 9 Sep 2007 12:45:27 +0200

Hi Lubo,
 
Take a look to these links, perhaps it could be the solution
 
bug #19699 : Bug in SNMP ASN1 decode; submitted patch
https://savannah.nongnu.org/bugs/?19699
 
patch #5896 : Bug in SNMP ASN1 decode; submitted patch
https://savannah.nongnu.org/patch/?5896 
 
https://savannah.nongnu.org/patch/download.php?file_id=12596
 
 
Tell us if this is the solution to your problem. If you see other place where this problem appear, tell us...
 
bye
 
----- Original Message -----
From: "Lubomir Toshev" <address@hidden>
To: <address@hidden>
Sent: Sunday, September 09, 2007 9:01 AM
Subject: [lwip-users] Incorrect RequestID field in SNMP response message

> Hello,
>
> I have ported lwIP 1.2.0 to a proprietary Coldfire system. I do not
> use RTOS and I work with a single thread. I use UDP communication as
> well as the SNMP agent. UDP communication works fine, but I have some
> problems with the SNMP agent.
>
> I noticed a mismatch between the RequestID fields of the request and
> response messages in an SNMP communication sequence. Some SNMP
> managers (like HostMonitor) succeed to GET values despite this
> mismatch. Others however (like Net-SNMP) will reject the response.
>
> It seems the RequetID field generated by my system has reversed byte
> order. Other fields of the message are encoded correctly, for example
> the specific variable values (sysUpTime, etc.).
>
> I am not sure if this is an issue of lwIP or it is related to my port.
> Please, make some comments on the possible reasons. What shall I be
> more carefull about?
>
> Two examples of SNMP GET request/response are given below. The first
> one is between HostMomitor (manager) and lwIP (agent). The second one
> is between Net-SNMP (manager) and lwIP (agent). Network traffic is
> captured by WireShark.
>
> 1. HostMonitor <-> lwIP (HostMonitor accepts the response)
>
> SNMP GET requet:
> RequestID is encoded 02 01 01 which is interpreted as "1"
>
> SNMP GET response:
> RequestID is encoded 02 04 01 00 00 00 which is interpreted as "16777216"
>
> SysUpTime value is encoded 43 03 00 9d c7 which is correct
>
> These are the two messages:
> +---------+---------------+----------+
> 04:39:39,029,776   ETHER
> |0   |00|06|70|00|00|01|00|c0|9f|16|ba|a3|08|00|45|00|00|44|00|a9|00|00|80|11|b8|
> aa|c0|a8|00|02|c0|a8|00|03|0b|e5|00|a1|00|30|3b|79|30|26|02|01|00|04|06|70|75|62|
> 6c|69|63|a0|19|02|01|01|02|01|00|02|01|00|30|0e|30|0c|06|08|2b|06|01|02|01|01|03|
> 00|05|00|
>
> +---------+---------------+----------+
> 04:39:39,030,235   ETHER
> |0   |00|c0|9f|16|ba|a3|00|06|70|00|00|01|08|00|45|00|00|4a|00|11|40|00|ff|11|fa|
> 3b|c0|a8|00|03|c0|a8|00|02|00|a1|0b|e5|00|36|fa|ef|30|2c|02|01|00|04|06|70|75|62|
> 6c|69|63|a2|1f|02|04|01|00|00|00|02|01|00|02|01|00|30|11|30|0f|06|08|2b|06|01|02|
> 01|01|03|00|43|03|00|9d|c7|
>
> 2. Net-SNMP <-> lwIP (Net-SNMP rejects the response)
>
> SNMP GET requet:
> RequestID is encoded 02 02 70 06 which is interpreted as "28678"
>
> SNMP GET response:
> RequestID is encoded 02 04 06 00 00 00 which is interpreted as "100663296"
>
> SysUpTime value is encoded 43 03 01 0F 57 which is correct
>
> These are the two messages:
> +---------+---------------+----------+
> 04:44:59,264,042   ETHER
> |0   |00|06|70|00|00|01|00|c0|9f|16|ba|a3|08|00|45|00|00|45|00|ae|00|00|80|11|b8|
> a4|c0|a8|00|02|c0|a8|00|03|0b|e6|00|a1|00|31|a2|96|30|27|02|01|00|04|06|70|75|62|
> 6c|69|63|a0|1a|02|02|70|06|02|01|00|02|01|00|30|0e|30|0c|06|08|2b|06|01|02|01|01|
> 03|00|05|00|
>
> +---------+---------------+----------+
> 04:44:59,264,466   ETHER
> |0   |00|c0|9f|16|ba|a3|00|06|70|00|00|01|08|00|45|00|00|4a|00|12|40|00|ff|11|fa|
> 3a|c0|a8|00|03|c0|a8|00|02|00|a1|0b|e6|00|36|89|59|30|2c|02|01|00|04|06|70|75|62|
> 6c|69|63|a2|1f|02|04|06|00|00|00|02|01|00|02|01|00|30|11|30|0f|06|08|2b|06|01|02|
> 01|01|03|00|43|03|01|0f|57|
>
>
> --
> Best regards,
> Lubo
>
>
>
>
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