Data Centre

Networks

OK, Google: Why does Chromecast clobber Wi-Fi connections?

Router vendors sling firmware to protect users from packet floods

By Richard Chirgwin

111 SHARE

Wi-Fi router vendors have started issuing patches to defend their products against Google Chromecast devices.

TP-Link and Linksys were first out of the blocks with firmware fixes, and TP-Link has posted this explanation of the issue.

The bug is not in the routers, but in Google's "Cast" feature, used in Chromecast, Google Home, and other devices. Cast sends multicast DNS (MDNS) packets as a keep-alive for connections to products like Google Home, and it seems someone forgot to configure the feature to go quiet when Chromecast devices are sleeping.

That, at least, is how Vulture South reads the issue that TP-Link's engineer described:

“These packets normally sent in a 20-second interval. However, we have discovered that the devices will sometimes broadcast a large amount of these packets at a very high speed in a short amount of time. This occurs when the device is awakened from the 'sleep mode', and could exceed more than 100,000 packets in a short amount of time.”

It continues: “The longer your device is in 'sleep', the larger this packet burst will be.”

If left alone long enough, TP-Link warned, the burst will fill up the router's memory and leave a reboot the only option to restore connectivity.

As a poster to this Reddit thread noted, MDNS uses UDP – and UDP doesn't have congestion control.

Linksys posted its firmware update here, while Netgear acknowledged the issue and put up a beta firmware release here.

ASUS users may also be affected.

It should be noted that the router vendors' fixes are mitigations while the world waits for Google to patch Cast. ®

UPDATE: The Register understands that Google has admitted to the flaw, said it impacts a "small number" of users, and committed to providing a fix in short order.

Sign up to our NewsletterGet IT in your inbox daily

111 Comments

More from The Register

Roku opens up

Roku tweaks Apple's nose with telly-friendly vid-streaming boxes

Broadcast TV gets a big bear hug in upgraded operating system and gizmo line

Google's hardware extravaganza: Ad giant takes on Sonos, Roku, Linksys, Amazon, Oculus... you name it

No market is safe from search engine monster

Tech giants at war: Google pulls plug on YouTube in Amazon kit

You won't sell our stuff? We won't let you watch our vids

Europe plans special tax for Google, Apple, Facebook, Amazon

French minister says around two per cent of turnover sounds about right

Automated Weather Source didn't see this cloud coming: Amazon snatches up AWS.com

Uh, we'll be having that domain

4K-ing-A! Roku bangs out broad range of new streaming boom boxes

From super cheap $30 to hefty $130

Flaws found in Linksys routers that could be used to create a botnet

Engineers working on firmware updates

Comcast is totally down with you using a Roku to watch Xfinity cable TV – but it'll cost you extra

US ISP is always app-y to take your money

Now here's an idea: Break up Amazon to get more shareholder cash

Analyst wants a bigger slice of Bezos' $1tn pie