NFS4 over tinc hangs

[Nikolaus Rath]

Hello,

I am experiencing system hangs when running NFSv4 over a tinc VPN. I
don't know if the problem is with NFS or tinc and would appreciate any
suggestions on how to narrow down the culprit. Unfortunately I cannot
simply run NFS directly over TCP -- the participating systems are
connected only over an open network.

The configuration is as follows: I have a master server ("spitzer") that
exports the NFS shares and also acts as the "primary" tinc server. All
other clients connect to the tinc instance on the main server to
establish the VPN, and then mount the NFS shares.

The server has 4 relevant network interfaces:

eth0 - Internet
eth1 - Internal network
hbt  - Tinc VPN
vnet0 - Virtual hosts
br0 - Bridge between eth1 and vnet0

The hbt, br0 (i.e., eth1 and vnet0) interfaces share a common
192.168.1.0/24 network. Proxy ARP is enabled for br0 and hbt.

I am using tinc 1.0.16 on 3.0.0, 64bit Ubuntu 10.04 LTS on both server
and client.

The problem is that as soon as more than three tinc clients are
accessing the NFS shares, any operations on the NFS mountpoints by the
clients hang. On the clients, tinc then takes 100% CPU time. On the
server, the tinc stance runs with about 20% load. When activating tinc
debugging, tinc seems to be busy forwarding packets. I also ran a packet
sniffer which showed me that 90% of the packets were NFS related, but I
am not familiar enough with NFS to be able to tell anything from the
packets themselves.

I could find no indication that the br0, eth1 and vnet0 interfaces and
systems are related to the problem in any way.


Any suggestions how I could debug this?


Best,

   -Nikolaus

-- 
 »Time flies like an arrow, fruit flies like a Banana.«

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