Messages in this thread | | | Date | Tue, 22 Jan 2013 16:18:04 -0500 | Subject | Re: [PATCH net-next] tcp: add ability to set a timestamp offset | From | Neal Cardwell <> |
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On Tue, Jan 22, 2013 at 3:52 PM, Andrey Vagin <avagin@openvz.org> wrote: > If a TCP socket will get live-migrated from one box to another the > timestamps (which are typically ON) will get screwed up -- the new > kernel will generate TS values that has nothing to do with what they > were on dump. The solution is to yet again fix the kernel and put a > "timestamp offset" on a socket.
One serious issue with this patch is that outgoing timestamp values will no longer correspond to tcp_time_stamp, so echoed timestamp values will also no longer have a meaningful relationship to tcp_time_stamp. That violates assumptions made in several places in the code, which assumes that we can compare echoed timestamp values to tcp_time_stamp; for example, there are several places where we do things like subtracting: tcp_time_stamp - tp->rx_opt.rcv_tsecr to find the estimated RTT for a segment.
neal
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