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*SOLVED* SMTP-Problem with OpenVZ-Kernel [message #3100]

Fri, 12 May 2006 09:54

arvid-dd
Messages: 4
Registered: May 2006

Junior Member

Hello,

I use a VPS as SMTP-Relay. Now I discovered a problem. When my VPS is trying to connect to one specific Firewall on Port 25 the communication is stopped. If I
simulate this with telnet, it looks like this :

---------------snipp------------------------
Telnet 1.2.4.6 25
Trying 1.2.3.4...
Connected to 1.2.3.4.
Escape character is '^]'.
2
---------------------------------------------

As you can see there comes an answer from this Firewall but the Packet is not transferred completely.

I have tried this with OpenVZ-Kernels between 2.6.8-022stab061.1 and 2.6.8-022stab077.1 with and without SMP.
My Machine is a DualXeon-Server and the problematic firewall is a Netscreen 5 GT with Trendmicro Antivirus. By the way, if i disable the Trendmicro Antivirus it works but this is not really an option.

Also i have tried the test kernel 2.6.16-026test012.1 and this works quite perfectly. Does anybody have a suggestion for me or do i have to wait until kernel 2.6.16 becomes stable?

[Updated on: Wed, 02 August 2006 06:49] by Moderator

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Re: SMTP-Problem with OpenVZ-Kernel [message #3121 is a reply to message #3100]

Sat, 13 May 2006 05:31

RapidVPS
Messages: 32
Registered: January 2006

Member

Have you ensured the packets are hitting the HN/VPS? I would use ngrep and inspect port 25 for traffic. If your firewall is problematic, I would say the problem lies there before the kernel version.

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Re: SMTP-Problem with OpenVZ-Kernel [message #3131 is a reply to message #3121]

Sun, 14 May 2006 08:51

arvid-dd
Messages: 4
Registered: May 2006

Junior Member

Yes, I have observed communication between the firewall and my Server. It is ok if the trendmicro antivirus is disabled. The funny thing is that any other server can communicate to port 25 on this
firewall without any problem. I have tried different machines with different hardware. This problem arises on every machine with OpenVZ-Kernel-2.6.8. The SMTP Relay on the VPS communicates to many other servers without a problem. Because it works with the new OVZ-Kernel 2.6.16 , I think it is somehow
a network problem with 2.6.8.

[Updated on: Sun, 14 May 2006 09:03]

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Re: SMTP-Problem with OpenVZ-Kernel [message #3149 is a reply to message #3131]

Mon, 15 May 2006 09:36

dev
Messages: 1693
Registered: September 2005
Location: Moscow

Senior Member

You need to collect tcpdump logs from all the machines participating in communication to understand where things go wrong. It can be some kind of misconfiguration (e.g. ECN).

http://static.openvz.org/userbars/openvz-developer.png

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Re: SMTP-Problem with OpenVZ-Kernel [message #3150 is a reply to message #3149]

Mon, 15 May 2006 11:35

arvid-dd
Messages: 4
Registered: May 2006

Junior Member

The only machine where i can do a tcpdump is the OpenVZ-Server. A dump is attached.

Attachment: tcpdump.txt
(Size: 1.83KB, Downloaded 292 times)

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Re: SMTP-Problem with OpenVZ-Kernel -Solved- [message #4887 is a reply to message #3100]

Tue, 01 August 2006 19:03

arvid-dd
Messages: 4
Registered: May 2006

Junior Member

Hi,

this is exactly my problem. After reading this Bugreport ( http://bugzilla.openvz.org/show_bug.cgi?id=210 )and the discussion about it i have done "echo 0 /proc/sys/net/ipv4/tcp_window_scaling". Now my mailserver works fine .

[Updated on: Tue, 01 August 2006 19:11]

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