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[alpine-devel] Alpinelinux openssh-hpn and vservers

From: Nathan Angelacos <>
Date: Sun, 17 Apr 2011 18:03:59 -0700

Just documenting something that I've noticed, don't know if this is the
root cause or not.

There are several guests running on a vserver host and each guest is
running sshd

Logging into a guest will /sometimes/ freeze up after the password or
key exchange. That is, the server allocates the terminal and starts the
command, but the client "locks up". The problem never happens on the
vserver host.

 From the client side, ssh will work fine 80% of the time, but then
won't work for several attempts, and then will work again.

After upgrading to 17 Apr 2010 edge on the vserver and guests, the
problem got worse.

Noticed the following in the new openssh config file:

> # the following are HPN related configuration options
> # tcp receive buffer polling. disable in non autotuning kernels
> # TcpRcvBufPoll yes
> # allow the use of the none cipher
> #NoneEnabled no
> # disable hpn performance boosts.
> # HPNDisabled no
> # buffer size for hpn to non-hpn connections
> #HPNBufferSize 2048

After setting TcpRcvBufPoll to NO, the problem went away.

Received on Sun Apr 17 2011 - 18:03:59 UTC