ARP Table: hostname uses reverse DNS lookup as fallback

[soif]

Arp table only relies on dhcp-leases entries to get the hostname. So when using an external DHCP server, or for IP addresses that are not assigned by DHCP, the displayed hostnames are always blank.

Features added:

• if hostame is not found in the dhcp-leases, the hostname is fetched from a DNS PTR query, (using the system's DNS server).
• use_dns variable can allow/disallow this behaviour (useful is someone would like to move this to a system preference)

HTH

[AdSchellevis]

A similar construction as used for the routes might be acceptable, putting the burden to resolve (with timeouts for everyone) isn't, so if you're up for it, please change the PR to include the option to the endpoint, either as uri part or as parameter (latter might make more sense at the moment).

For some inspiration, the following code blocks are being used in the route dialog.

core/src/opnsense/mvc/app/views/OPNsense/Diagnostics/routes.volt

Line 62 in 745d46c

ajaxGet("/api/diagnostics/interface/getRoutes/", {resolve:resolve}, function (data, status) {

core/src/opnsense/mvc/app/controllers/OPNsense/Diagnostics/Api/InterfaceController.php

Lines 137 to 142 in 745d46c

	$backend = new Backend();
	if (empty($this->request->get('resolve'))) {
	$response = $backend->configdRun('interface routes list -n json');
	} else {
	$response = $backend->configdRun('interface routes list json');
	}

core/src/opnsense/scripts/routes/show_routes.py

Line 42 in 745d46c

sp = subprocess.run(['/usr/bin/netstat', '-rW' + resolv], capture_output=True, text=True)

ps: removing the -n from arp would resolve in the same pass.

[soif]

Hi thanks for the fast review!

You're perfectly right. I wrongly assumed that the ARP table should typically be only filled with LAN IP addresses where DNS timeout is usually not an issue for in-addr.arpa zones. But for cases where OPNsense is used mainly with publically routables ip addresses, that obviously would create timeout issues.

Thanks for the inspiration examples (helps a LOT): I'm gonna fix the PR to make DNS resolving optionnal, like in routes.

[soif]

Here it is.

Notice that:

• i used the -r as additional parameter, that triggers the Reverse DNS.
  Without -r, the command behaves exactly as in the latest release.

• I've added a natural sort of IP addresses (separate commit, to be easily reverted), as requested in IPs in ARP table not sorted numerically #4185.
  This is visible when using the command line:
  configctl "interface list arp -r"
  When using the GUI, and because Javascript sorts the results, it might still be usefull, when for example sorting by Interface or Interface name.

HTH

[AdSchellevis]

@soif thanks, I've made some small cleanups in 1548ae0 before merging. The natural sort has been left out for now as it will likely lead to new tickets since it doesn't fix the complete issue.

[soif]

@AdSchellevis Thank you for the fast merge & cleanup. 👍

Happy to contribute! 😎