Network

Monitoring and controlling a JUDO i-Soft plus via LAN

| Mario

Some time ago, a water softening device was installed in my home main water supply line. Such a device contains one or multiple gel capsules that act as ion exchangers, replacing calcium and magnesium in the fresh water supply with sodium. In regions with a rather hard water, this can save you a lot of trouble with maintenance of valves and the lifetime of water-consuming devices like washing machines and dishwashers.

Fig. 1: JUDO i-Soft plus unit with LCD touchscreen user interface.

For regulation, a conductivity sensor determines the hardness of the incoming water. After running through the gel exchanger, the residual hardness is assumed to be around 0.5 °dH which allows the mixing ratio of raw and processed water to be calculated. I won’t go further into details here, the bottom line is: It works like a charm, water is as soft as it needs to be. The device at hand is built by JUDO and is available in several configurations. Basic models contain a two-capsule exchanger for seamless switchover/regeneration cycles and an integrated electronic control unit for automatic regeneration of the gel. A more advanced “i-Soft plus” model is extended by a touchscreen user interface complete with LAN/WLAN network access. This enables monitoring through a specialized iPad application where the interested user can view total water consumption per day, week, month or year as well as change different system parameters. As a nice bonus, the plus unit has an integrated main line valve which is closed automatically whenever user-set time, volume or flow rate limits are exceeded. This already saved my ass once when a pipe became leaky inside a wall. Unfortunately, the exact protocol for communication with the device is not disclosed, which is where this story begins. Continue reading →

DNS problems with Netgear FVS equipment

| Mario

A follow-up on the recent DNS-related stuff:

I figured out today that my router had a hand in those weird random connection problems. What made me especially nervous was the almost systematic way that DNS and other random UDP packets vanished from the ‘net during browsing or testing with various tools. The requests were shown to be sent in both the Wireshark protocols and the router packet capture, but an answer never arrived. As it turns out, Enterprise-class devices have their firewall preconfigured to block UDP flood from inside the local network.

The definition of “flood” used here is:

“20 simultaneous, active UDP connections from a single computer on the LAN”

http://documentation.netgear.com/fvs336g/enu/202-10257-01/FVS336G_RM-06-09.html

Now, somehow my setup managed to step over that line, and from what I gather on the ‘net I am not the only one experiencing this. Sometimes the system will run clean for a few days, then bug in increasing frequency until I get fed up with it and kill the whole DNS process plus cache. Apparently, this fixes the problem for some time as a good reset almost always does, but it is no permanent solution.

To debug, first turn on the attack-related logging functions in the router and clear the logs. Then call up “nslookup” on Windows based systems and fire some random URL DNS requests in fast sequence. In my case, after four requests the firewall kicks in and UDP flood warnings appear in the log. Maybe Windows 7 just leaves the ports open a little too long, I don’t know and I haven’t checked. However, since this feature has been turned off in the firewall settings I had no further DNS problems, and the speed of browsing has increased a little.  Hopefully that was all there was to it.

Another point of interest: Some Netgear devices have developed a habit of kicking lots of NBSTAT-packets on the LAN, one about every 5 seconds or so. Seems to belong to some type of NETBIOS detection mechanism, though the sense escapes me. The packets are of unicast-type and therefore disrupt everything one could possibly have in the way of wake-on-unicast, which linux supports to wakeup devices from standby if they are talked to directly. NETBIOS features are nowhere to be found in the configuration menu, so I guess at some point the checkbox for that must have gotten mislabeled. The one responsible is “ARP broadcast” found with the LAN settings. Turning it off quiets things down a lot.

But: You lose the capability to show unknown devices in the LAN clients list for simple management of DHCP fixed leases. You can still turn on ARP for a few minutes if you need to detect anything, though.