Gigaom reports that Google has filed a lawsuit this week against Rockstar, the patent holding company jointly owned by Apple, Microsoft, BlackBerry, Sony, and Ericsson whose portfolio comes mostly from the corpse of bankrupt Canadian telecom giant Nortel. In October, Rockstar had sued Google and a variety of Android OEMs — Samsung, LG, and HTC included — alleging infringement on a number of those ex-Nortel patents, and Google's countersuit is geared directly at sliding the platform out of the consortium's aim. The filing stops just short of calling Rockstar an outright patent troll:

Rockstar produces no products and practices no patents. Instead, Rockstar employs a staff of engineers in Ontario, Canada, who examine other companies' successful products to find anything that Rockstar might use to demand and extract licenses to its patents under threat of litigation.

It also effectively calls out Rockstar for disproportionately targeting Android when its underlying patent portfolio could apply to a much wider swath of technology — in fact, there's an entire section of the filing titled "Rockstar's Campaign Against Android." The company notes that in situations where targeted Android OEMs make other devices not running the platform, those devices have been excluded from Rockstar's complaint.

Android is a frequent target for patent lawsuits

Google, of course, is no stranger to patent litigation over Android: its purchase of Motorola Mobility was seen in part as an effort to beef up its defensive intellectual property position, and Microsoft (a Rockstar co-owner) is known to make good money by licensing patents to companies producing Android products. But Mountain View is using some particularly dire language in this latest suit, accusing Rockstar of having "placed a cloud" over Android and of "[interfering] with Google's business relationships" with OEMs.

To that end, the suit is geared at protecting the very companies making the bulk of the devices in the Android ecosystem — up to and including the crown jewel, Samsung — but it also has its own Nexus line in mind. Throughout the filing, Google calls out the Nexus 5, 7, and 10 by name, seeking a court ruling that neither the Nexus phones and tablets nor the operating system itself infringe any of the patents in question.

Barring a situation where Google and Android OEMs strike licensing deals with Rockstar — which seems unlikely in light of this latest volley — the legal proceedings could drag out for quite a while.