NFS via VPN stuck after a certain amount of transfer

[Corey Smith]

On 2/26/06, Yusuke Shinyama <yusuke at cs.nyu.edu> wrote:
> More concretely, I made a connection from a Linux box
> to a FreeBSD box via a cable modem. Both are running openssh-4.3p2
> client/server and enabled for point-to-point tunneling.
> Then I mounted the remote directory via NFS with tcp and intr option.
> Everything worked fine so far. Then I tried to
> "cp -Rp /mnt/remote/linux-2.4.31 /local".
> After the directory is partially transferred, the cp process
> stopped and ping to the remote host (via tun) didn't respond.
> But this only happens occationaly. For smaller directories,
> the copy finishes without any problem.

This sounds very familiar:

http://www.mindrot.org/pipermail/openssh-unix-dev/2006-January/024101.html

Have you tried looking at a tcpdump of the tun interface?  I would be
interested to know if the tunnel is unidirectional (packets are only
received but not sent or vise versa).

-Corey Smith