[SOLVED] Coffee shop wifi dns weirdness

mgushee · 2009-09-05 23:32:25

Let me preface this by saying that AFAICT I do not have an issue with wireless access in general--just in one location.

So, here it is. I have an ASUS Eee netbook (Celeron model), running Arch Linux of course, system last upgraded ~2 weeks ago. I use XFCE as my desktop and WICD as my main connection management tool. Anyway, I use this machine at various WiFi spots around town. Usually I have no difficulty in connecting--in fact I'm sitting at Panera right now, using their wireless network. Also, FWIW, I've never had any trouble connecting over my wired network at home. But there is one particular location--which happens to be my favorite coffee shop--where I can never seem to get on line--although it appears to be a different problem each time. The staff there are not technically inclined at all--couple weeks ago I asked the owner if he knew the IP address of the DNS server, and he didn't understand the question. I think they know how to reset the network password, and that's about it. They call Comcast when they have any serious issues.

But the most recent incident is truly bizarre. I found the right network in the WICD applet, pressed Connect ... authentication OK ... IP address OK. Then I opened Firefox and tried to access Google ... nope. Unable to find server. Then a few other popular sites: Facebook, Reddit, CNet ... nope, nope, nope. Tried the same sites in Midori, with the same result. But I could ping all of the sites with no trouble, and--even weirder--I had no trouble accessing the sites in Links (ncurses browser). So it appears that DNS was working in virtual terminals but not for GUI apps?!

Any notion what might be going on here?

Last edited by mgushee (2009-09-15 23:46:49)

mgushee · 2009-09-07 00:13:02

Update: I tried again today, and experienced the same problem. There's no doubt it is a name resolution issue, but my description may have been oversimplified--I tried some other apps/utilities today, each with several hosts/domains. What I can say for sure is that name resolution succeeds every time with certain apps, and fails every time with others. To wit:

SUCCEEDED
ping
traceroute
links
Midnight Commander (i.e., mounting an FTP site as a VFS)

FAILED
Firefox
Midori
wget
curl
kftp
ssh

Also: according to /etc/resolv.conf, the sole DNS server is the shop's wireless router. Also also: I found out they have switched from Comcast to Qwest.

neddie_seagoon · 2009-09-07 01:06:56

Have you tried to use different nameservers?
http://wiki.archlinux.org/index.php/OpenDNS

mcover · 2009-09-07 11:56:54

Since ping succeeds, name resolution shouldn't be the issue, since ping needs to resolve a name before pinging. I'd try lookup up a site like archlinux.org and take the IP-address and try access that with Firefox, just to verify the problem.

What does nslookup tell you?

nslookup www.archlinux.org

Does that fail?

mgushee · 2009-09-13 05:47:27

neddie_seagoon wrote:

Have you tried to use different nameservers?
http://wiki.archlinux.org/index.php/OpenDNS

No, but this looks like a good workaround. I'll do it if I can't find an actual solution.

ewaller · 2009-09-13 05:57:41

One thing I have found with some open public sites is that they block DNS servers other than themselves and then put you in "DNS Jail", directing you to a local page requiring you agree to T&Cs before they let you out of jail and provide real DNS results.

Now suppose, hypothetically of course, that that local page enforcing acknowledgment of T&Cs were to require a browser from a software house from the USA's Pacific Northwest. I'm just saying...

mgushee · 2009-09-13 06:29:05

mcover wrote:

Since ping succeeds, name resolution shouldn't be the issue,

No, it certainly shouldn't. Which I why I used terms like weirdness and bizarre in my original post.

since ping needs to resolve a name before pinging. I'd try lookup up a site like archlinux.org and take the IP-address and try access that with Firefox, just to verify the problem.

Yep, tried that with Google. Given the IP address, Firefox had no problem accessing the site.

But anyway ... I have gathered some more information with the help of Wireshark. Now, I haven't been able to test as thoroughly as I would like, because I found that starting a Wireshark capture session tends to kill the wireless connection (BTW, is that a known issue, and if so, are there measures I can take to prevent it?). However, I did see a pattern that seems relevant. Here is a DNS request initiated by Firefox:

     21 32.412754   192.168.0.145         192.168.0.1           DNS      Standard query A www.google.com
     22 32.412856   192.168.0.145         192.168.0.1           DNS      Standard query AAAA www.google.com
     24 32.437820   192.168.0.1           192.168.0.145         DNS      Standard query response CNAME www.l.google.com A 74.125.155.105 A 74.125.155.104 A 74.125.155.99 A 74.125.155.106 A 74.125.155.103 A 74.125.155.147
     25 32.438836   192.168.0.1           192.168.0.145         DNS      Standard query response

Note the second line--"Standard query AAAA." To the extent I was able to test, this appears for every app that doesn't work, and never for the apps that do work. Now, I'm really not familiar with the DNS protocol, but I found RFC 3596, which explains that the AAAA record type is for IPv6 addresses. So we have requests for IPv6 addresses, but as above, the only addresses that come in response are IPv4.

I also noticed that in some cases for the apps that can't access sites, the initial DNS request is followed by one for www.stopbadware.org--but that doesn't happen for every site, so I'm guessing it doesn't really matter. Just seemed a little strange.

So, am I on the right track? If not, I would be happy to post more of the Wireshark capture results.

mgushee · 2009-09-15 23:49:02

Okay, well, I found a solution: disable IPv6! I had seen posts referring to performance problems, but didn't realize that using IPv6 could cause DNS requests to fail completely.

I'm still curious as to why this would happen in some locations and not others.

BTW, OpenDNS worked fine too.

Thanks to everyone for the suggestions.

R00KIE · 2009-09-16 12:44:43

mgushee wrote:

Okay, well, I found a solution: disable IPv6! I had seen posts referring to performance problems, but didn't realize that using IPv6 could cause DNS requests to fail completely.
I'm still curious as to why this would happen in some locations and not others.
BTW, OpenDNS worked fine too.
Thanks to everyone for the suggestions.

Because most routers support ipv4 only and some don't play well with ipv6 enabled clients, at least thats what I've seen every time before when this problem pops up.

Besides I guess you don't really need ipv6 for now, the router you have at home most probably only supports ipv4, the same goes for most consumer equipment installed and on sale, of course I may be wrong, if anyone knows better please do correct me

Arch Linux

#1 2009-09-05 23:32:25

[SOLVED] Coffee shop wifi dns weirdness

#2 2009-09-07 00:13:02

Re: [SOLVED] Coffee shop wifi dns weirdness

#3 2009-09-07 01:06:56

Re: [SOLVED] Coffee shop wifi dns weirdness

#4 2009-09-07 11:56:54

Re: [SOLVED] Coffee shop wifi dns weirdness

#5 2009-09-13 05:47:27

Re: [SOLVED] Coffee shop wifi dns weirdness

#6 2009-09-13 05:57:41

Re: [SOLVED] Coffee shop wifi dns weirdness

#7 2009-09-13 06:29:05

Re: [SOLVED] Coffee shop wifi dns weirdness

#8 2009-09-15 23:49:02

Re: [SOLVED] Coffee shop wifi dns weirdness

#9 2009-09-16 12:44:43

Re: [SOLVED] Coffee shop wifi dns weirdness

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