Is someone able to answer my question?
We use net-snmp as agentx master agent and I need to know what is the max
length of a single octet-string?
//Regards
Claus
On 01.08.2013, at 21:52, Claus Klein wrote:
> Hi,
>
> I found 2 defines and one 1 mib value which are not clear to me:
>
> snmp_agent.h
> #define SNMP_MAX_PDU_SIZE 64000 /* local constraint on PDU size sent by agent
> * (see also SNMP_MAX_MSG_SIZE in snmp_api.h)
> */
>
> snmp_api.h
> #define SNMP_MAX_MSG_SIZE 1472 /* ethernet MTU minus IP/UDP header */
>
> used only at protocol.c
> int
> agentx_parse(netsnmp_session * session, netsnmp_pdu *pdu, u_char * data,
> size_t len)
> {
> register u_char *bufp = data;
> u_char buffer[SNMP_MAX_MSG_SIZE];
> ...
> }
>
> and there is the mib var:
> SNMP-FRAMEWORK-MIB::snmpEngineMaxMessageSize.0 = INTEGER: 1500
>
>
> Why is the SNMP_MAX_PDU_SIZE is not used?
> Can the max PUD size grater than the max message size?
> Why is snmpEngineMaxMessageSize not 1472?
>
>
> P.S.: there is this caclulation at snmpusm.c:
> /*
> * Calculate the biggest sPDU for the response (i.e., whole - ovrhd).
> *
> * FIX Correct?
> */
> *maxSizeResponse = maxMsgSize - (end_of_overhead - wholeMsg);
>
> and at snmptsm.c I found this:
> /* Section 5.2, Step 7:
> The maxSizeResponseScopedPDU is calculated. This is the maximum
> size allowed for a scopedPDU for a possible Response message.
> */
> *parms->maxSizeResponse = parms->maxMsgSize; /* XXX */
>
> A short test with snmpget -V3 -Ddump ... got this:
> dumph_send: msgMaxSize
> dumpx_send: 02 03 00 FF E3
> dumpv_send: Integer: 65507 (0xFFE3)
>
>
> Can anyone please help?
>
> Thanks in advance
> Best Regards
> Claus
>
>
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