Re: MacAddress type

On Wed, Sep 26, 2012 at 4:54 PM, Francois Bouchard
<[email protected]> wrote:
> Hi list,
>
> Question about one MacAddress SNMP oject type we have in the MIB.
>
> When sending a snmpget request to the MacAddress Object with the textual
> names:
>
> $ snmpget -v 3 -u  ......  MPBC-RMH-MIB::mpbcRMHMacAddress.0 we get garbage:
> MPBC-RMH-MIB::mpbcRMHMacAddress.0 = STRING:
> 36:43:3a:46:46:3a:42:45:3a:30:31:3a:30:30:3a:31:35
>
> Then, if sending the getsnmp to the same object, but using the OID we get
> the correct value "6C:FF:BE:01:00:15":
> $ snmpget -v 3 -u ...  .1.3.6.1.4.1.4464.2.1.4.1.5.0
> SNMPv2-SMI::enterprises.4464.2.1.4.1.5.0 = STRING: "6C:FF:BE:01:00:15"
>
>
> So in the code I should limit the string to 6 Bytes.  So must I omit the
> colon separated string when writing (see C source)?

Yes, you must turn the colon separated ASCII string that you get from
the Exec_Popen_Cmd() call into 6 bytes, and return that.

Make sure not to use strlen, since 0 is a valid value inside a MAC address.

  Bill

>
> Thanks,
>
> Francois
>
>
> From the C source:
>
>   // Get MAC, format : "11:22:33:44:55:66"
>     if(!Exec_Popen_Cmd(s_mac_addr, sizeof(s_mac_addr), "ifconfig -a eth0 |
> grep HWaddr | awk ' {print $5}'"))
>     {
>         strcpy(s_mac_addr, "??:??:??:??:??:??");
>     }
>
>
>     /* We are never called for a GETNEXT if it's registered as a
>        "instance", as it's "magically" handled for us.  */
>
>     /* a instance handler also only hands us one request at a time, so
>        we don't need to loop over a list of requests; we'll only get one. */
>
>     switch(reqinfo->mode) {
>
>         case MODE_GET:
>
>             snmp_set_var_typed_value(requests->requestvb, ASN_OCTET_STR,
> s_mac_addr, strlen(s_mac_addr));     // the length of the data in bytes
>             break;
>
>
>         default:
>             /* we should never get here, so this is a really bad error */
>             snmp_log(LOG_ERR, "unknown mode (%d) in
> handle_mpbcRMHMacAddress\n", reqinfo->mode );
>             return SNMP_ERR_GENERR;
>     }
>
> (...)
>
>
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