Re: Graph signal strength from OpenWrt?

On 21/04/12 08:50 AM, Gandalf wrote:
> IMHO, that's none of your choice.
> Either, the manufacturer (or provider of OpenWRT) supplies such a MIB or SNMP
> Agent or the like or you're at a loss.

mini_snmpd can be extended to publish additional OIDs, e.g.

> 	/* The demo MIB: two random integers (note: the random number is only
> 	 * updated every "g_timeout" seconds; if you want it updated every SNMP
> 	 * request, remove the enclosing "if" block).
> 	 * Caution: on changes, adapt the corresponding mib_build() section too!
> 	 */
> #ifdef __DEMO__
> 	if (full) {
> 		get_demoinfo(&u.demoinfo);
> 		if (mib_update_entry(&m_demo_oid, 1, 0, &pos, BER_TYPE_INTEGER, (const void *)u.demoinfo.random_value_1) == -1
> 			|| mib_update_entry(&m_demo_oid, 2, 0, &pos, BER_TYPE_INTEGER, (const void *)u.demoinfo.random_value_2) == -1) {
> 			return -1;
> 		}
> 	}
> #endif

snmpd can be extended in many ways, e.g. with arbitrary commands or 
shell scripts:

>        exec [MIBOID] NAME PROG ARGS
>
>        sh [MIBOID] NAME PROG ARGS
>               invoke  the  named  PROG with arguments of ARGS.  By default the
>               exit status and first line of output from the  command  will  be
>               reported via the extTable, discarding any additional output.

>        pass [-p priority] MIBOID PROG
>               will  pass control of the subtree rooted at MIBOID to the speci‐
>               fied PROG command.

I am inclined to extend mini_snmpd to publish wireless signal strength, 
is this a good strategy? I can SSH to OpenWrt, so another alternative is 
to skip SNMP and configure Cacti to grab signal strength with SSH (or 
yet another protocol?)

If I extend mini_snmpd, then I must choose which OID to use:

DD-WRT apparently publishes signal strength as: 
.1.3.6.1.4.1.2021.255.3.54.1.3.32.1.26.1 [1]

  - but I can't find the MIB where this OID is defined

Ubiquity AirOS publishes signal strength as: .1.3.6.1.4.1.14988.1.1.1.1.1.4

  - which is defined by a MikroTik MIB [2] but I also want to graph 
noise floor, and this MIB defines noise floor only for access points, 
not wireless stations

Cacti ships a data query for signal strength defined by a Karlnet MIB: 
.1.3.6.1.4.1.762.2.5.2.1.8 [3]

Since my goal is to graph signal strength with Cacti, maybe it's easiest 
to use this OID? However Karlnet now seems obscure: I struggled to 
Google for info about it

There is an IEEE802dot11 MIB [4] but it doesn't define signal strength

Any advice on choosing which OID to use?

[1] http://dd-wrt.com/wiki/index.php/Simple_Network_Management_Protocol
[2] http://www.mikrotik.com/download/Mikrotik.mib
[3] http://www.oidview.com/mibs/762/KBRIDGE-MIB.html
[4] http://www.oidview.com/mibs/0/IEEE802dot11-MIB.html

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