[lvs-users] Weird problem with LVS-DR

To: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: [lvs-users] Weird problem with LVS-DR
From: Martijn Grendelman <martijn@xxxxxxxx>
Date: Wed, 19 Dec 2007 14:58:42 +0100

I am a long-time user of LVS, but now I've got a problem that I can't
seem to solve. Searching the HOWTO and the web hasn't given me anything
useful, so I turn to the experts now ;-)

I have a quite straightforward LVS-DR setup: two machines, both running
a webserver on port 80, one of them directing traffic to either the
local node or the other machine. I am using the 'sh' scheduler, as I
have been for ages.

Since a while, directing traffic to the other machine (not the director)
doesn't work anymore, BUT ONLY on a specific VIP:PORT combination.
During my tests, the LVS setup is as follows:

martijn@whisky:~> rr ipvsadm -L -n
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP sh
  ->            Route   500    0          0
TCP sh
  ->            Route   500    0          0
TCP sh
  ->            Route   500    0          0

Note that all references to the local node have been temporarily
removed. Now, the service defined second (port 81) works. The third one,
port 80, but a different VIP, works too. The first one, the one that I
need, does not.

When I connect to, I see some kind of SYN storm on
both the director and the real server on

14:37:42.232694 IP > S
557344343:557344343(0) win 5840 <mss 1460,sackOK,timestamp 218577173
0,nop,wscale 7>
14:37:42.232961 IP > S
557344343:557344343(0) win 5840 <mss 1460,sackOK,timestamp 218577923
0,nop,wscale 7>

Mostly identical lines (and nothing else) keep appearing at a high rate,
even after I kill the connection on the client. Only after I remove the
service from LVS, this stops.

Any idea what may cause this? I'd be happy to provide additional
information, if needed.

Best regards,

Martijn Grendelman

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