[PATCH net-next] tcp: add ability to set a timestamp offset

[Andrey Vagin <avagin@openvz.org>]

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.

A socket offset is added in places where externally visible tcp
timestamp option is parsed/initialized.

Connections in the SYN_RECV state are not supported, global
tcp_time_stamp is used for them, because repair mode doesn't support
this state. In a future it can be implemented by the similar way as for
TIME_WAIT sockets.

For time-wait sockets offset is inhereted by a proper tcp_sock.

A per-socket offset can be set only for sockets in repair mode.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrey Vagin <avagin@openvz.org>

Andrey Vagin (3):
  tcp: adding a per-socket timestamp offset
  tcp: set and get per-socket timestamp
  tcp: send packets with a socket timestamp

 include/linux/tcp.h      |  3 +++
 include/uapi/linux/tcp.h |  1 +
 net/ipv4/tcp.c           | 11 +++++++++++
 net/ipv4/tcp_input.c     |  8 +++++++-
 net/ipv4/tcp_ipv4.c      | 12 +++++++-----
 net/ipv4/tcp_minisocks.c |  3 +++
 net/ipv4/tcp_output.c    |  4 ++--
 net/ipv6/tcp_ipv6.c      | 22 +++++++++++++---------
 8 files changed, 47 insertions(+), 17 deletions(-)
-- 
1.7.11.7