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Xip.io - a magic domain name that provides wildcard DNS for any IP address

xip.io

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Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#61

Post by harbud »

aoberoi wrote: post #31
mariocesar wrote: post #19

Earlier quoted context omitted.

If you click on the "custom DNS server" link on the site, you will get a surprise

hah, they wrote it in node.

Nice, although were I to write one, I'd probably just use PowerDNS and its pipe backend. Probably only some 30 lines of Perl/Ruby/whatever. Example: http://wiki.powerdns.com/trac/browser/trunk/pdns/modules/pip...

Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#63

Post by ajasmin »

no_more_death wrote: post #53
shawndrost wrote: post #51

I've also made use of lvh.me (local virtual host), a url who's dns points at 127.0.0.1. It's good for testing subdomains on localhost.

localhost.microsoft.com and localhost.yahoo.com also used to redirect to 127.0.0.1. And, of course, this wreaked utter havoc with cookies (since cookies are accessible across the entire domain). Zalewski discusses in TTW (The Tangled Web). DNS hackery is really dangerous.

I gather that Xip.io have the same issue with cookies.

Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#65

Post by sp332 »

Karunamon wrote: post #40
zaptheimpaler wrote: post #15

Earlier quoted context omitted.

We have no proof that the code on the repo is related in any way to the code the actual site is running.

You have no proof that you aren't running a rootkit logging all your keystrokes right this second ;)

You have no proof that you're not living in the Matix right now!

Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#66

Post by mparlane »

sstephenson wrote: post #16
zaptheimpaler wrote: post #15

Earlier quoted context omitted.

We have no proof that the code on the repo is related in any way to the code the actual site is running.

You're right. I'm probably just running xip.io to steal all your sensitive development-mode form data!

Information you have access to:

External ip addresses of requestees. Internal ip addresses of requestees.

To some, this is very useful...

Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#67

Post by sim0n »

Karunamon wrote: post #38
MiguelHudnandez wrote: post #36

Earlier quoted context omitted.

I know you meant your question rhetorically, but I believe you can add a proxy server to the iPhone and handle any hostname trickery there. Edit: Proxy settings can't be global, but are assigned individually for each WiFi connection.

Yeah but then you're into jailbreak-warranty-invalidation territory. Great for personal devices, not so great on corporate.

Why would adding a proxy server invalidate your warranty? Adding a proxy is built in to iOS.

Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#68

Post by colmmacc »

jsprinkles wrote: post #48

I've identified several technical problems with this domain, and this isn't an example of how to properly operate DNS. 37signals is setting an absurdly low TTL on these records (10 minutes; the answers never change, I absolutely do not understand the logic behind this TTL), which means every 10 minutes you're re-resolving a local address , through a CNAME (so two DNS round trips, and in my case this resolution took b…

It's a cool idea, but there are some other problems too; which I just want to list to help the developers and am not trying to rain on a parade.

As in the parent comment, a CNAME is returned for arbitrary names;

  % dig foo.192.0.2.1.xip.io     
  foo.192.0.2.1.xip.io.	600	IN	CNAME	foo.a2eo0.xip.io.
  foo.a2eo0.xip.io.	600	IN	A	192.0.2.1
but only if the request is of type A. Requests of other types return invalid NXDOMAIN responses - invalid because they contain no SOA in the authoritative section. CNAMEs are supposed to be returned for all records of any type for a given name, not doing so is dangerous as it can poison caches. Not returning the CNAME even for a query of type "CNAME" is particularly harmful.

Responding with no name would be bad on its own, but saying that no name exists is clearly wrong and can be used to poison caches (the NXDOMAIN is cacheable). Note that most browsers and clients will now perform an AAAA lookup prior to the A lookup - poisoning their own cache if they happen to have a copy of the SOA for xip.io in cache (the SOA record hints to the negative cache lifetime).

It's not clear that using an intermittent CNAME does anything useful - why not just return an A record, with a billion second TTL value. As-is, it merely adds a round-trip (the CNAME and A are not returned in one pass by ns-1.xip.io).

Additionally, ns-1.xip.io does not mark the "authoritative answer" bit in any responses - which will cause issues with some resolvers.

But, still a neat idea. Question for the developers;

It's clear that the intermediate CNAME represents an encoding of the IP address, e.g.;

  foo.192.0.2.1.xip.io.	600	IN	CNAME	foo.a2eo0.xip.io.
here "a2eo0" is an encoding of 192.0.2.1 , but then;

  foo.192.0.2.2.xip.io.	600	IN	CNAME	foo.k201s.xip.io.
are you using some kind of cipher?

PS. Everybody please use 192.0.2.0/24 for IP addresses in examples and documentation, and 2001:db8::/16 for IPv6. See RFC3330/5735 and RFC3849. It's good karma ;-)

Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#69

Post by dools »

jsprinkles wrote: post #48

I've identified several technical problems with this domain, and this isn't an example of how to properly operate DNS. 37signals is setting an absurdly low TTL on these records (10 minutes; the answers never change, I absolutely do not understand the logic behind this TTL), which means every 10 minutes you're re-resolving a local address , through a CNAME (so two DNS round trips, and in my case this resolution took b…

Hold on - who cares? This isn't meant for use in production right? Or am I missing something... from what I can tell the purpose here is that I can setup a domain that will resolve to an address on my LAN without having to modify, say, /etc/hosts on my android device (which I wouldn't even know how to do) or setup a DNS server on my LAN (which is of course possible but a lot more long winded than the solution proposed here).

I can't see how it matters whether or not there are problems with this from the perspective of being a "correct" DNS server so long as it works for it's intended purpose (testing things on your local network from a bunch of different devices).

Re: Xip.io - a magic domain name that provides wildcard DNS for any IP address

#70

Post by dools »

LocalPCGuy wrote: post #62

I'm not exactly why it is so hard to connect to a local machine on your network. Either determine your local IP address or your network computer name.

If you're creating an application where connecting on the "root domain" matters it can be problematic. For example, imagine you were creating some URL rewrites using apache's mod_rewrite and they worked for http://some.domain.com/rewrite-goes-here/ you would have to do a bunch of extra work (or an extra set of rules even) to make that work also for 10.0.1.1/my_app_without_vhost/rewrite-goes-here/

When you're testing on your LAN using a PC/mac or whatever you can do a local DNS modification on the machine (eg. /etc/hosts) but when you're testing from an iPad or some other device this is either impossible or prohibitively difficult.

The other option is to setup a DNS server on your LAN which is a headache all it's own - this is a very simple and elegant way of circumventing these issues. Awesome stuff.

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