[CRIU] [PATCH] tcp: don't apply tsoffset if rcv_tsecr is zero

[Andrew Vagin]

On Tue, Aug 20, 2013 at 11:11:58AM +0400, Cyrill Gorcunov wrote:
> On Tue, Aug 20, 2013 at 10:49:27AM +0400, Andrey Vagin wrote:
> > From: Andrew Vagin <avagin at openvz.org>
> > 
> > The zero value means that tsecr is not valid, so it's a special case.
> > 
> > Currently this issue affects logic of tcp_rcv_rtt_measure_ts.
> 
> Andrew, could you please provide more detailed change log? Ie
> with description which issue we've faced and why it happened.
> I know that you know very well why it's happaned and where
> but other people (especially on net-dev@) might be quite
> surprised what we're fixing.

tcp: don't apply tsoffset if rcv_tsecr is zero

The zero value means that tsecr is not valid, so it's a special case.

tsoffset is used to customize tcp_time_stamp for one socket.
tsoffset is usually zero, it's used when a socket was moved from one
host to another host.

Currently this issue affects logic of tcp_rcv_rtt_measure_ts. Due to
incorrect value of rcv_tsecr, tcp_rcv_rtt_measure_ts sets rto to
TCP_RTO_MAX.