Windows 7 Network Awareness: How Windows knows it has an Internet connection

http://blog.superuser.com/2011/05/16/windows-7-network-awareness/

by ivoflipse • 15 years ago

222 40 15 years ago

blog.superuser.com

jerrya7• 15 years ago

Yes, I have wanted to build something like that for Android, mainly to keep my phone from getting confused when it's connected to someone's wifi that demands some check box be checked off for service.

It would periodically awaken, see if the wifi is connected, if it is is there connectivity, if there is, go back to sleep, if there is not, turn the wifi off.

I've also wanted to build for Android the same piece of code, but if for 2 or 5 urls it gets back the same page with a checkbox, it checks off the box and sends it back off.

But I am curious, do all those wifi dns terms and agreements hijacking pages break any sort of RFC?

And is there any solution in ip6?

Or is there a real fix possible in ip4?

ephemient• 15 years ago

I'm not sure if you can access its state programmatically, but Android already does detection: the WiFi status icon is green if the system can make a connection to Google's servers, and grey otherwise.

IPv[46] have nothing to do with it. "Captive portal" pages are meant to prevent you from getting to the larger Internet, until you do whatever magic is required to dismiss them.

jerrya7• 15 years ago

"the WiFi status icon is green if the system can make a connection to Google's servers, and grey otherwise."

That's interesting. How does it detect it's at Google's servers?

I've often had occasions on my non-rooted, gingerbread, nexus one, where the phone believes it is on the net, on wifi, and shunts all activity to wifi, and yet, it's really stuck on one of those captive portal pages.

It even happens if I am just driving down the road.

I had thought that perhaps a small bit of technology would fix that, perhaps by turning the wifi off, or by automatically checking in on starbuck's router, but I am beginning to see I may just have a sick-making sense of entitlement.

Without being terribly cognizant of the RFCs I am surprised these portal captures are within spec.

dsl• 15 years ago

To answer all of your questions: Don't use someone else's wifi if you don't like how it behaves. Your sense of entitlement makes me sick.

jerrya7• 15 years ago

Can you expand on that?

How is my wanting to either turn my wifi off, or automatically checking a terms and conditions box at a starbucks, or library, or school, or courtroom, or hospital router demonstrating a sick making sense of entitlement?

I would think many people would want such behavior from their phones, but I can see that you and whomeever voted my original question down are genuinely disturbed I would want this.

jodrellblank• 15 years ago

How much are we supposed to adjust our opinions based on your feeling sick, exactly? Have you tried not feeling sick? Perhaps it's a localised glitch?

telcodud• 15 years ago

Check out this open source application sbautologin (link: http://code.google.com/p/sbautologin/) that automatically logs into Starbucks (AT&T really) WiFi.

jerrya7• 15 years ago

Thank you!

snprbob86• 15 years ago

The iPhone uses a very similar technique. If you connect to a wifi network that requires login, a browser sans address bar will pop-up over your current app and allow you to login. Once an external resource can be reached, the browser disappears and returns you to the previous app. Steve Jobs even alluded to it / bragged about it when the iPhone was first unveiled, 2 years before Win7 was released.

upthedale• 15 years ago

In fairness, this has nothing to do with Win7 specifically. The NCSI service was introduced with Vista.

kinetik• 15 years ago

...8 months before the iPhone was released.

wrs• 15 years ago

For the curious, previous HN discussion on this wifi captive portal trick ("WISPr"): http://news.ycombinator.com/item?id=1674911

phlux• 15 years ago

Just a note - this functionality was not in the initial day-1 release of the iPhone... I don't recall which update had this, but it was well after 1.0

greengarstudios• 15 years ago

iPhone OS 3.0

(now called iOS 3.0)

- iOS app developer who was there when Apple explained it

ilikejam• 15 years ago

Possible vector for some sort of attack? The ncsi service that requests www.msftncsi.com is presumably very simple, but then...

jerrya7• 15 years ago

It serves approx 32 bytes but it serves it to such an enormous number of machines that I have been curious as to how it is set up.

Netcraft says: F5 Big-IP Microsoft-IIS/7.0 213.199.181.90

But I am curious as to what the real details of the setup are.

TeHCrAzY• 15 years ago

probably a small cluster of w2k8 servers? I doubt ms would be using anything else.

ahi• 15 years ago

I just assumed it noticed when I entered the login information 2 minutes prior, then waited until the most annoying moment to give me a completely useless fraking notification.

drivebyacct2• 15 years ago

if you're paranoid enough to disable this, you shouldn't be using windows. there are far more and better ways for windows and other windows software to phone home.

Blarat• 15 years ago

I think that making it phone your own NCSI server instead would be quite interesting, just in case your computer gets stolen.

omh• 15 years ago

It could be useful for corporate laptop users. I can imagine using this so that I know the IP address and connectivity status of remote users to use when they call in with issues.

idonthack• 15 years ago

Do we really need an entire article about this? Seriously, if you couldn't figure this out on your own in about 10 seconds, you're in the wrong line of work

aneth2• 15 years ago

It's nice to see the precise mechanics explained, and it might be rather "negative" to make your point, but it is a pretty obvious solution and I agree with you.

mlinsey• 15 years ago

" If the response is never received, or if there is a redirect, then a DNS request for dns.msftncsi.com is made. If DNS resolves properly but the page is inaccessible, then it is assumed that there is a working internet connection, but an in-browser authentication page is blocking access to the file. This results in the pop-up balloon above. If DNS resolution fails or returns the wrong address, then it is assumed that the internet connection is completely unsuccessful, and the “no internet access” error is shown."

Would this mean that DNS poisoning msftncsi.com would prevent Win7 machines from accessing the internet? Or would this merely cause the 'no internet access' error to be displayed despite your connection working anyway?

yakyak• 15 years ago

This service can be disabled, so obviously it doesn't prevent you from accessing the internet even if it thinks it doesn't have access. It would SAY "no internet connection", but internet resources would still work just fine.

alvarosm2• 15 years ago

Well, you tell my granny to disable some service...

alvarosm2• 15 years ago

Which is terribly annoying when you have a crappy router that intercepts dns queries and sometimes fails to resolve, making Windows think there's no internet, which makes it NOT let you even try to send the packets. Not my case but I've seen it happen: big FAIL. What a crappy way of "checking" you have internet access... (@yakyak, no they don't work, that's what's so screwed up not just the half-assed method for checking)

dominikb• 15 years ago

Apple claims that Mac OS X is "the world's most advanced operating system". But it's these details that I consider advanced and clever. Apple's marketing statements went from funny to offensive and unsupported.

known• 15 years ago

Sounds like http://linuxcommand.org/man_pages/ruptime1.html

Windows 7 Network Awareness: How Windows knows it has an Internet connection

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