Weird Problem: no contact to selected websites only on one..

jochen.czemmel · External Since: Dec 29, 2006 Posts: 4

Hello,

I've got a weird Problem:

On my newest Laptop some websites are not displayed.
I tried it with firefox and konqueror. On another laptop in
the same net these sites are displayed correctly.
On the new laptop, the host names are resolved correctly,
I can telnet to the undisplayed websites, but I don't get no
answer. From the new laptop I can login to both the old
laptop and the firewall machine.

Technical Details:

websites I can contact: eg. http://www.wohin-heute.at/
websites I can not contact: eg. http://www.gmx.de

Firewall: OpenBSD 3.3 with packet filtering
(Logs do not show anything I can relate to the problem)
no DNS server running, ppp connection via DSL

New Laptop: OpenSuse 10.2, Firewall completely
disabled, default route to the firewall machine,
no proxy for firefox ('direct connection to internet') and in yast
can ping and telnet to www.gmx.de (on port 80) but gets no
answer (the same is true for wget).

Old Laptop: Suse 10.0, default route to the firewall machine
works without problems

As I can ping all websites, this is not a problem of DNS, right?
As I can see the websites on another laptop in my local net,
this is not a problem of the firewall, right?
As I can't see the websites in both firefox and konqueror,
this is not a problem of firefox, right?
As I can see some websites, this can not be a problem of
firewall port 80 or wrong proxy, right?
As I do not get an answer from www.gmx.de on port 80
via telnet (but I get the connection!), this can not be a
problem of 'web 2.0' features the browser may not
support, right?

So I currently have the Problem: where should I start searching?

I found a hint in the opensuse faq (proxy setttings and ipv6 settings),
I tried both, no effect.

Could this be a problem between (older) OpenBSD and (newer) Linux?

Any Ideas?

Jochen

shedied · External Since: Nov 11, 2006 Posts: 35

jochen.czemmel RemoveThis @gmx.de wrote:
> Hello,
>
> I've got a weird Problem:
>
> On my newest Laptop some websites are not displayed.
> I tried it with firefox and konqueror. On another laptop in
> the same net these sites are displayed correctly.
> On the new laptop, the host names are resolved correctly,
> I can telnet to the undisplayed websites, but I don't get no
> answer. From the new laptop I can login to both the old
> laptop and the firewall machine.
>
> Technical Details:
>
> websites I can contact: eg. http://www.wohin-heute.at/
> websites I can not contact: eg. http://www.gmx.de
>
> Firewall: OpenBSD 3.3 with packet filtering
> (Logs do not show anything I can relate to the problem)
> no DNS server running, ppp connection via DSL
>
> New Laptop: OpenSuse 10.2, Firewall completely
> disabled, default route to the firewall machine,
> no proxy for firefox ('direct connection to internet') and in yast
> can ping and telnet to www.gmx.de (on port 80) but gets no
> answer (the same is true for wget).
>
> Old Laptop: Suse 10.0, default route to the firewall machine
> works without problems
>
> As I can ping all websites, this is not a problem of DNS, right?
> As I can see the websites on another laptop in my local net,
> this is not a problem of the firewall, right?
> As I can't see the websites in both firefox and konqueror,
> this is not a problem of firefox, right?
> As I can see some websites, this can not be a problem of
> firewall port 80 or wrong proxy, right?
> As I do not get an answer from www.gmx.de on port 80
> via telnet (but I get the connection!), this can not be a
> problem of 'web 2.0' features the browser may not
> support, right?
>
> So I currently have the Problem: where should I start searching?
>
> I found a hint in the opensuse faq (proxy setttings and ipv6 settings),
> I tried both, no effect.
>
> Could this be a problem between (older) OpenBSD and (newer) Linux?
>
> Any Ideas?
Does the new laptop know which one is the gateway? Or did you let the
thing 'autodetect' network settings? Maybe it's not a 'direct
connection' to the internet but more of an 'access the internet thru a
LAN' connection? The networking HOWTO in ldp.org (linux documentation
project site) may be more helpful in this regard; I remember there is a
list of questions or faqs there that could narrow down your problem, to
help you move forward on this.

CBFalconer · External Since: Jun 08, 2005 Posts: 661

jochen.czemmel DeleteThis @gmx.de wrote:
>
> On my newest Laptop some websites are not displayed.
> I tried it with firefox and konqueror. On another laptop in
> the same net these sites are displayed correctly.
> On the new laptop, the host names are resolved correctly,
> I can telnet to the undisplayed websites, but I don't get no
> answer. From the new laptop I can login to both the old
> laptop and the firewall machine.

Maybe you have them disabled via your hosts file?

--
Merry Christmas, Happy Hanukah, Happy New Year
Joyeux Noel, Bonne Annee.
Chuck F (cbfalconer at maineline dot net)
<http://cbfalconer.home.att.net>

jochen.czemmel · External Since: Dec 29, 2006 Posts: 4

Thank you for your hints, but:

The new laptop knows the route and the gateway, as the
old one does, and the host file on the new machine is up-to-date
(I did not use anything like 'auto detection', I configure my network
by hand, and my network with OpenBSD firewall and some Linux
boxes works since a couple of years).

If the routing or the hosts file would have been wrongly configured,
the new laptop would not be able to see some web pages, right?

The Problem is that it works for some web pages correctly, and for
some others not, they can ping and telnet (port 80) to the machine,
but the web servers do not answer (or the answer does not
reach the client - telnet, firefox, konqueror).

LDP was a good hint, I'll start searching for some Information.

UPDATE: When I boot Windows XP on the new laptop, everything works
fine, so the OpenBSD Firewall should not cause the problem, it must
be the configuration of OpenSuSE 10.2. I noticed that the firewall has
to be disabled at several places, perhaps this causes the problem.

Any more Ideas?

Jochen

Moe Trin · External Since: Aug 12, 2004 Posts: 1732

On 29 Dec 2006, in the Usenet newsgroup comp.os.linux.misc, in article
<1167413863.702377.303030.RemoveThis@n51g2000cwc.googlegroups.com>, jochen.czemmel.RemoveThis@gmx.de
wrote:

>I can telnet to the undisplayed websites, but I don't get no answer.

What does this mean? Do you not get a response, or do you get an error
message - either from your system or the remote?

>Firewall: OpenBSD 3.3 with packet filtering
>(Logs do not show anything I can relate to the problem)
>no DNS server running, ppp connection via DSL

On the SuSE boxes - what is the MTU settings? You'd see this in the output
of /sbin/ifconfig -a

>New Laptop: OpenSuse 10.2, Firewall completely
>disabled, default route to the firewall machine,

>Old Laptop: Suse 10.0, default route to the firewall machine
>works without problems

Run tcpdump on both systems, and compare the packets. Look specifically
at the packet size, IP and TCP header flags, and any ICMP error packets.

>As I can ping all websites, this is not a problem of DNS, right?

Or routing - correct

>As I can see the websites on another laptop in my local net,
>this is not a problem of the firewall, right?

Probably correct

>As I can't see the websites in both firefox and konqueror,
>this is not a problem of firefox, right?

Correct - but remember those are complicated applications, depending on
the system networking running correctly.

>As I can see some websites, this can not be a problem of
>firewall port 80 or wrong proxy, right?

Correct

>As I do not get an answer from www.gmx.de on port 80
>via telnet (but I get the connection!), this can not be a
>problem of 'web 2.0' features the browser may not
>support, right?

Might be MTU - might be ECN

>So I currently have the Problem: where should I start searching?

packet sniffer. You should also try to compare the network setup
configuration files.

>I found a hint in the opensuse faq (proxy setttings and ipv6 settings),
>I tried both, no effect.

Not surprisingly

>Could this be a problem between (older) OpenBSD and (newer) Linux?

OBSD3.3 is Spring 2003... SuSE 10.0 is Fall 2005, while 10.2 is brand
new. I doubt it, as both PMTU and ECN problems have been around for
over six years.

Old guy

CBFalconer · External Since: Jun 08, 2005 Posts: 661

Moe Trin wrote:
> jochen.czemmel RemoveThis @gmx.de wrote:
>
>> I can telnet to the undisplayed websites, but I don't get no answer.
>
> What does this mean? Do you not get a response, or do you get an
> error message - either from your system or the remote?

I suspect he meant to write "I don't get any answer". "no answer"
is both vile English grammar and ambiguous.

--
Merry Christmas, Happy Hanukah, Happy New Year
Joyeux Noel, Bonne Annee.
Chuck F (cbfalconer at maineline dot net)
<http://cbfalconer.home.att.net>

s. keeling · External Since: Nov 10, 2005 Posts: 230

Moe Trin <ibuprofin.DeleteThis@painkiller.example.tld>:
> On 29 Dec 2006, in the Usenet newsgroup comp.os.linux.misc, in article
> <1167413863.702377.303030.DeleteThis@n51g2000cwc.googlegroups.com>, jochen.czemmel.DeleteThis@gmx.de
> wrote:
>
> >I can telnet to the undisplayed websites, but I don't get no answer.
>
> What does this mean? Do you not get a response, or do you get an error
> message - either from your system or the remote?
> [tour de force snipped]
> Old guy

Great debug session. I learned a few things. Your posts are very
high S/N ratio, thanks.

> OBSD3.3 is Spring 2003... SuSE 10.0 is Fall 2005, while 10.2 is brand
> new. I doubt it, as both PMTU and ECN problems have been around for
> over six years.

To the OP, you need to be up to date wrt bug fixes and security
patches before you get to keep both pieces. Sorry.

--
Any technology distinguishable from magic is insufficiently advanced.
(*) http://www.spots.ab.ca/~keeling Linux Counter #80292
- - http://www.faqs.org/rfcs/rfc1855.html Please, don't Cc: me.
Spammers! http://www.spots.ab.ca/~keeling/emails.html

jochen.czemmel · External Since: Dec 29, 2006 Posts: 4

Hi all,

when I telnet to one of the web sites that I can not see
in the browsers, telnet tells me that I am connected.

something like

Trying 143.166.83.38...
Connected to www.dell.com.
Escape character is '^]'.

Then I type in a HTTP GET request (requesting for example index.html),
then nothing happens any more, for a long time. When I do this
on the older laptop, I get an immediate answer.

I know that my OpenBSD 3.3 is out of date.

However, nobody up to now could really EXPLAIN what could
be the cause, so I am afraid that my new laptop does not
work even after I have upgraded to OpenBSD 4.0.

Thank you for telling me that my pidgin English is ambiguous,
sorry for that. Please answer a bit more detailed than
"Might be MTU - might be ECN"
Whats the point about MTU and ECN?

Any more Ideas?

Regards

Jochen

jochen.czemmel · External Since: Dec 29, 2006 Posts: 4

Hello,

this seems to be a problem of OpenSuSE 10.2, cf.

https://bugzilla.novell.com/show_bug.cgi?id=227090

So I hope that this bug will be fixed soon...

Regards

Jochen