(crossposted with a few modifications from my blog)
Recently, my team was kind enough to add a WLANpi to my toolset, and it is indeed a very handy gizmo for network engineering work.
The other day, I found yet another useful trick I could do with it: Pocket Software Repository. Sounds basic, because it is. But useful nonetheless. Necessity is the mother of invention, after all.
The situation was that I needed to update AirWave on a customer server, and the WLAN management network at this site is isolated from the rest of the world (and even if it wasn’t, a satellite connection is not a fun thing to download a couple of gigabytes over!). Since it was a multi-week trip away I came prepared for this and while I was at home on my gigabit fiber connection, I downloaded a whole host of software images I might need and stored them on my laptop.
AirWave’s limited CLI does give you the option of uploading a file, but it does it in a way that is in fact initiating an SCP download from somewhere. There’s not really any way to push a file to the box, so you have to initiate a pull from the AirWave server.
No worries, Macs are Unix-ish, and this should be trivial, right? Of course it's never that easy... in Mojave there appears to be a strange quirk where ssh won’t respond on anything but localhost. So, my plan to scp the file from my Mac was shot to bits. I needed a linux box, and didn’t want to download an install ISO over the satellite link any more than I wanted to download AirWave (after all, AirWave is itself Linux-based). Then I remembered I had my WLANpi.
Like an increasing number of gadgets these days, the WLANpi’s USB port (used for power) also happens to be an OTG port, and presents itself to the host system as an “RNDIS Ethernet Gadget”, and sets up an Ethernet link over the USB. This allows gadgets like the WLANpi and the Ekahau Sidekick to easily communicate with the host without going through the brain damage of custom device drivers (Aruba is taking a similar approach to IoT support on its APs via the USB port). RNDIS handles the messy layer 1 and layer 2 stuff, sets up layer 3 (the WLANpi defaults to 192.168.42.1) and then the application only has to implement standard upper-layer network communications.
So all I had left to do was open an ssh session to my WLANpi (I use Emtec’s ZOC, which I have been using since the days of OS/2!) to see if I had enough storage space on the device to hold the 2.5GB AirWave update (Narrator: it did). Then I fired up Transmit, my go-to file transfer application on MacOS (whatever your platform, anything that supports scp will fit the bill), and sent the Airwave update over to a newly created files directory in the WLANpi user’s home directory.
Once the file was on the WLANpi, I plugged the WLANpi’s Ethernet port into a VLAN that was accessible to the WLAN management devices (I used the AP management VLAN since it already had a DHCP server), and then opened an ssh session to the AirWave server from my existing session on the WLANpi, essentially using it as a jump box. This served to verify port 22 connectivity, and also meant I didn’t have to configure another port to put my laptop on that VLAN.
Once I was able to copy the file from the AirWave server, the process was a snap to get the thing upgraded.