A simple convenience configfile can provide a mapping between VPP
interface names, Linux Control Plane interface names, and descriptions.
An example:
```
interfaces:
"TenGigabitEthernet6/0/0":
description: "Infra: xsw0.chrma0:2"
lcp: "xe1-0"
"TenGigabitEthernet6/0/0.3102":
description: "Infra: QinQ to Solnet for Daedalean"
lcp: "xe1-0.3102"
"TenGigabitEthernet6/0/0.310211":
description: "Cust: Daedalean IP Transit"
lcp: "xe1-0.3102.11"
```
This configuration file is completely optional. If the `-c` flag is
empty, or it's set but the file does not exist, the Agent will simply
enumerate all interfaces, and set the `ifAlias` OID to the same value
as the `ifName`. However, if the config file is read, it will change
the behavior as follows:
* Any `tapNN` interface names from VPP will be matched to their PHY by
looking up their Linux Control Plane interface. The `ifName` field
will be rewritten to the _LIP_ `host-if`. For example, `tap3` above
will become `xe1-0` while `tap3.310211` will become `xe1-0.3102.11`.
* The `ifAlias` OID for a PHY will be set to the `description` field.
* The `ifAlias` OID for a TAP will be set to the string `LCP: `
followed by its PHY `ifName`. For example, `xe1-0.3102.11` will
become `LCP TenGigabitEthernet6/0/0.310211 (tap9)`
When using SNMP BULK GET requests (from Zabbix in our case), the default value of 1024 truncates the request, resulting in malformed requests reaching the agent. Using an 8K buffer fixes this. A better approach perhaps would be to process the buffer using a loop.
