[lua-monitoring] Send ARP table information

[openwisp]

[lua-monitoring] Send ARP table information

[PabloCastellano]

@nemesisdesign Apparently the arp command is deprecated and ip neigh is the way to go. In fact arp in the latest version of openwrt is an alias to cat /proc/net/arp.

Here is an example of the output of both so you can compare:

root@08-00-27-5D-DF-07:~# ip neigh
10.0.3.3 dev eth1 lladdr 52:54:00:12:35:03 used 0/0/0 probes 1 STALE
192.168.1.34 dev eth2 lladdr 18:5e:0f:12:12:0e used 0/0/0 probes 1 STALE
10.0.3.2 dev eth1 lladdr 52:54:00:12:35:02 used 0/0/0 probes 4 STALE
192.168.1.1 dev eth2 lladdr cc:d4:a1:06:dd:0a ref 1 used 0/0/0 probes 1 REACHABLE
192.168.56.1 dev br-mng lladdr 0a:00:27:00:00:00 ref 1 used 0/0/0 probes 4 REACHABLE
fe80::9a9c:57ff:fe8b:4f67 dev eth2 lladdr 98:9c:57:8b:4f:67 ref 1 used 0/0/0 probes 1 DELAY
fe80::2e0e:3dff:fed6:506 dev eth2 lladdr 2c:0e:3d:d6:05:06 ref 1 used 0/0/0 probes 1 REACHABLE
fe80::ced4:a1ff:fe06:dd0a dev eth2 lladdr cc:d4:a1:06:dd:0a router used 0/0/0 probes 0 STALE
fe80::be3d:85ff:fed7:53e0 dev eth2 lladdr bc:3d:85:d7:53:e0 used 0/0/0 probes 1 STALE

root@08-00-27-5D-DF-07:~# arp
IP address       HW type     Flags       HW address            Mask     Device
10.0.3.3         0x1         0x2         52:54:00:12:35:03     *        eth1
192.168.1.34     0x1         0x2         18:5e:0f:12:12:0e     *        eth2
10.0.3.2         0x1         0x2         52:54:00:12:35:02     *        eth1
192.168.1.1      0x1         0x2         cc:d4:a1:06:dd:0a     *        eth2
192.168.56.1     0x1         0x2         0a:00:27:00:00:00     *        br-mng

Should we still go with arp?

[nemesifier]

@PabloCastellano thanks for bringing this up, that's great.

Take a look at this:

# installs the full IP package
# (the default one I think is a stripped down version available in busybox)
opkg install ip
ip -json neighbour

The full ip package has a -json flag so you can avoid having to parse it.

We can use its format as is, this should reduce friction when we will try adding this kind of features on other embedded OSes in the future.

[PabloCastellano]

Since the output of ip neigh can be very different depending on the version, my PR just parses /proc/net/arp so far