Subject: Connection remains in the ESTABLISHED state when the virtual IP is down.

From: Arkadiusz Bubała <[email-masked]>
Date: Thu, 04 Feb 2016 08:49:08 +0100

Hello,

I encountered following issue:
when I connect with NFS server through virtual IP then I remove this IP 
netstat still shows that connection is ESTABLISHED. When I put down 
whole interface all ESTABLISHED connections disappear.  The kernel 
version is 3.10.92.

How to reproduce.

create virtual IP:

ip addr add 88.88.88.1/24 dev eth0 label eth0:0 (or ifconfig eth0:0 
88.88.88.1)

then make connection from the NFS client. In netstat there is:
tcp        0      0 88.88.88.1:2049         88.88.88.2:765 ESTABLISHED-

and delete virtual IP:
ip addr del 88.88.88.1/24 dev eth0 (or ifconfig eth0:0 down)

the netstat still shows that conneciton is ESTABLISHED and remains in 
that state for about 5 minutes. Even if I recreate virtual IP I can't 
access to the server until it disappears.

When the whole interface is put down (ifconfig eth0 down)  the netstat 
doesn't show any entries for my virtual IP and if I put it up again I 
can access to the server immediately.

Shouldn't the ESTABLISHED connections be removed also when virtual IP is 
down? Or maybe there is any sysctl option to change that behaviour?

-- 
Best regards
Arkadiusz Bubała
Open-E Poland Sp. z o.o.
www.open-e.com