Re: Only some websites will open - Ubuntu

Em Quarta, 30 de Maio de 2007 02:38, Big Dave Smith escreveu:

> I have just installed a fresh copy of Kubuntu 7.04, and I'm having
> some unusual behavior. Only some websites will open. I have tried
> with firefox, and Konqueror, and the results are the same. For
> example:
>
> google.com opens. And fast too...speedy
> slashdot.org will not open
> vmware.com will not open
> ibm.com will open
>
> At first I thought it might have to do with DNS settings, but I
> manually changed the DNS server entries and it had no effect. DNS
> seems to be working anyway. In firefox, it finds the site, loads the
> title, the icon for the site, and then states "Transferring data from
> [blah]..." in the status bar. In Konqueror the transfer rate at the
> bottom immediately drops to about 100b/s, then disappears entirely.
>
> I am behind a Linksys RV082 router, but I have had another Kubuntu
> 7.04 system behind the same router with no problems.
>
> I MAY have had this issue with this computer before, so it might be a
> driver issue, but I am no linux pro, and I have no idea what steps to
> take to investigate or fix it. That is only a guess though.
>
> Any help will be really appreciated. Thank you in advance!

i've seen this situation before more than once, i bet it's the router.

reset and restart your adsl router, there should be a little button (hidden)
to do the reset, and then you have to reconfigure your router again
(country specs, username, password, etc...)

tell us if i'm right... good luck

ArameFarpado wrote:
> Em Quarta, 30 de Maio de 2007 02:38, Big Dave Smith escreveu:
>
>> I have just installed a fresh copy of Kubuntu 7.04, and I'm having
>> some unusual behavior. Only some websites will open. I have tried
>> with firefox, and Konqueror, and the results are the same. For
>> example:
>>
>> google.com opens. And fast too...speedy
>> slashdot.org will not open
>> vmware.com will not open
>> ibm.com will open
>>
>> At first I thought it might have to do with DNS settings, but I
>> manually changed the DNS server entries and it had no effect. DNS
>> seems to be working anyway. In firefox, it finds the site, loads the
>> title, the icon for the site, and then states "Transferring data from
>> [blah]..." in the status bar. In Konqueror the transfer rate at the
>> bottom immediately drops to about 100b/s, then disappears entirely.
>>
>> I am behind a Linksys RV082 router, but I have had another Kubuntu
>> 7.04 system behind the same router with no problems.
>>
>> I MAY have had this issue with this computer before, so it might be a
>> driver issue, but I am no linux pro, and I have no idea what steps to
>> take to investigate or fix it. That is only a guess though.
>>
>> Any help will be really appreciated. Thank you in advance!
>
> i've seen this situation before more than once, i bet it's the router.
>
> reset and restart your adsl router, there should be a little button (hidden)
> to do the reset, and then you have to reconfigure your router again
> (country specs, username, password, etc...)
>
> tell us if i'm right... good luck
>
It certainly could be that.

Try power cycling BEFORE you wipe out its settings though.

My router allows me to dump its settings onto a PC file and upload them
later as well. useful trick.

On Jun 8, 5:01 am, The Natural Philosopher wrote:

> > reset and restart your adsl router, there should be a little button (hidden)
> > to do the reset, and then you have to reconfigure your router again
> > (country specs, username, password, etc...)
>
> > tell us if i'm right... good luck
>
> It certainly could be that.
>
> Try power cycling BEFORE you wipe out its settings though.
>
> My router allows me to dump its settings onto a PC file and upload them
> later as well. useful trick.

It's really not a router issue. There's no problem with the Windows
boxes (although there IS a problem if I pop a LiveCD in the Windows
boxes). There's no problem with other locations on the network. We're
sharing a number of DSL connections among maybe 20 or so families,
most running Windows and a few running Linux and I'm the only one
having a problem. I'm also the only one running Kubuntu 7.04, although
I don't know if that's significant.

kubismo-at-gmail.com wrote:
> On Jun 8, 5:01 am, The Natural Philosopher wrote:
>
>>> reset and restart your adsl router, there should be a little button (hidden)
>>> to do the reset, and then you have to reconfigure your router again
>>> (country specs, username, password, etc...)
>>> tell us if i'm right... good luck
>> It certainly could be that.
>>
>> Try power cycling BEFORE you wipe out its settings though.
>>
>> My router allows me to dump its settings onto a PC file and upload them
>> later as well. useful trick.
>
> It's really not a router issue. There's no problem with the Windows
> boxes (although there IS a problem if I pop a LiveCD in the Windows
> boxes). There's no problem with other locations on the network. We're
> sharing a number of DSL connections among maybe 20 or so families,
> most running Windows and a few running Linux and I'm the only one
> having a problem. I'm also the only one running Kubuntu 7.04, although
> I don't know if that's significant.
>
>
I would not discount it being a router issue just because only one
machine is affected.

I had a very similar problem here and it WAS a router issue. Some sites
just 'timed out' on me.

Rebooting the router fixed it, and a firmware upgrade fixed it permanently.

Its a simple enough thing to do..just power cycle the router.

And would at least eliminate that one from the argument.

I have power cycled my router and swapped in a brand new one
(different make) and also power cycled the antennae. It doesn't make
any difference. Windows boxes in the house are fine, Linux boxes can
only connect to a tiny handful of sites. I can also ping some other
sites but most network traffic is not getting through. Even apt-get
update times out.

On Jun 8, 7:49 am, The Natural Philosopher wrote:

> Its a simple enough thing to do..just power cycle the router.
>
> And would at least eliminate that one from the argument.

kubismo-at-gmail.com wrote:
> I have power cycled my router and swapped in a brand new one
> (different make) and also power cycled the antennae. It doesn't make
> any difference. Windows boxes in the house are fine, Linux boxes can
> only connect to a tiny handful of sites. I can also ping some other
> sites but most network traffic is not getting through. Even apt-get
> update times out.
>

Ok. That starts to be interesting.

It would seem we are down to some kernel issues with the particular
router/ISP/Linux type/target site chain.

Pings are not always a reliable guide..some sites drop ICMP packets to
reduce potential DOS attacks and the like.

Let's review what you have.

DNS works OK, so we can pretty much say that IP basics, routing and UDP
traffic is OK.

What seems to be happening is that TCP traffic is subject to losses or
timeouts.

That could be buffer overflow in the kernel..due to wrong window sizes
or what have you.

Oh. I found this. It sorta rings a bit too close to what you are
reporting to be ignored. It also implicates routers ;-) Just like we
said..consider seeing if your local router can be upgraded with later
firmware as well..

"Because of a recent change in TCP window scale settings in Linux 2.6.17
kernel and higher, you may have had some problems connecting to certain
Web sites. In this tip, I'll show you a workaround for the time-out
problem, but first, let me give you the background on this issue.

A typical TCP packet has a window field that allows for a maximum window
size of 64 KB. While this was sufficient when the Internet was young and
most systems didn't have the power to handle anything greater, it's
quite small for today's bandwidth-hungry applications.

As a result, a solution called window scaling was codified back in 1992;
this provided an extra TCP option that contains an eight-bit scale
factor. The value of this field indicates how much larger the window
size should be by shifting the value of the window sizes by a certain
number of bits. For instance, if the scale factor is set to 5, the
window size would be shifted by 5 bits or multiplied by 32.

The problem is that in 2.6.16 and earlier, the default scale factor was
0, so there was no increase in TCP window sizes. In the 2.6.17 kernel,
this was changed to a value of 7. In an ideal world, this wouldn't be a
problem. In practice, however, some "broken" routers are rewriting the
window scale TCP option -- setting the scale factor to 0 but leaving the
actual enabling option in place.

Essentially, all of this means that there are some Web sites that cannot
be connected to from a system using kernel 2.6.17 and higher. The kernel
developer's stance is that those routers are broken and need to be
replaced. In the real world, these routers may continue to operate for
years before being fixed or replaced.

One solution is to reset the Linux kernel's window scaling option. While
this doesn't fix broken routers, it will allow your system to connect to
a remote site if you find you are experiencing the window scaling
problem. If you're unsure whether this is the problem you are having,
you can test it by executing:

echo 0 > /proc/sys/net/ipv4/tcp_default_win_scale

To make the setting permanent, edit /etc/sysctl.conf and add:

net.ipv4.tcp_default_win_scale = 0

This will disable window scaling completely, which will allow you to
reach some sites you couldn't before. Right or wrong, the kernel
developers refuse to revert the change, so options are either to disable
window scaling on your own and go back to pre-2.6.17 defaults, or
contact those sites that can't be reached and try to convince them to
find and replace the broken routers."

I note that my kernel is 2.6.16 only..so maybe thats why its stunningly
reliable haha!

Further to my last post

the command 'uname -a' should show what kernel you are running and the
site where I got the info and fix from is
http://www.builderau.com.au/program/linux/soa/
Try-this-workaround-for-time-out-issues-in-kernel-2-6-17-and-higher/
0,339028299,339277823,00.htm

Sorry that will definitely wrap into something unintelligible..

On Jun 8, 8:43 am, The Natural Philosopher wrote:

> problem. If you're unsure whether this is the problem you are having,
> you can test it by executing:
>
> echo 0 > /proc/sys/net/ipv4/tcp_default_win_scale
>
> To make the setting permanent, edit /etc/sysctl.conf and add:
>
> net.ipv4.tcp_default_win_scale = 0

I am indeed running a recent kernel (Linux ubuntu 2.6.20-16-generic #2
SMP Wed May 23 01:46:23 UTC 2007 i686 GNU/Linux) so perhaps this might
be the problem, but unfortunately this didn't fix it. I don't seem to
have a tcp_default_win_scale file on my system and editing the
sysctl.conf (with a reboot) didn't seem to change anything.

On Jun 8, 8:43 am, The Natural Philosopher wrote:

> problem. If you're unsure whether this is the problem you are having,
> you can test it by executing:
>
> echo 0 > /proc/sys/net/ipv4/tcp_default_win_scale
>
> To make the setting permanent, edit /etc/sysctl.conf and add:
>
> net.ipv4.tcp_default_win_scale = 0

I am indeed running a recent kernel (Linux ubuntu 2.6.20-16-generic #2
SMP Wed May 23 01:46:23 UTC 2007 i686 GNU/Linux) so perhaps this might
be the problem, but unfortunately this didn't fix it. I don't seem to
have a tcp_default_win_scale file on my system and editing the
sysctl.conf (with a reboot) didn't seem to change anything.

On Jun 8, 8:43 am, The Natural Philosopher wrote:

> problem. If you're unsure whether this is the problem you are having,
> you can test it by executing:
>
> echo 0 > /proc/sys/net/ipv4/tcp_default_win_scale
>
> To make the setting permanent, edit /etc/sysctl.conf and add:
>
> net.ipv4.tcp_default_win_scale = 0

I am indeed running a recent kernel (Linux ubuntu 2.6.20-16-generic #2
SMP Wed May 23 01:46:23 UTC 2007 i686 GNU/Linux) so perhaps this might
be the problem, but unfortunately this didn't fix it. I don't seem to
have a tcp_default_win_scale file on my system and editing the
sysctl.conf (with a reboot) didn't seem to change anything.