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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