tcp: adding a per-socket timestamp offset

This functionality is used for restoring tcp sockets. A tcp timestamp
depends on how long a system has been running, so it's differ for each
host. The solution is to set a per-socket offset.

A per-socket offset for a TIME_WAIT socket is inherited from a proper
tcp socket.

tcp_request_sock doesn't have a timestamp offset, because the repair
mode for them are not implemented.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 0 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2c7e5963c2ea..8a90bda96038 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -400,6 +400,8 @@ void tcp_init_sock(struct sock *sk)
         tcp_enable_early_retrans(tp);
         icsk->icsk_ca_ops = &tcp_init_congestion_ops;
 
+        tp->tsoffset = 0;
+
         sk->sk_state = TCP_CLOSE;
 
         sk->sk_write_space = sk_stream_write_space;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index f0409287b5f4..4dfc99f54f67 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -288,6 +288,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
                 tcptw->tw_rcv_wnd       = tcp_receive_window(tp);
                 tcptw->tw_ts_recent     = tp->rx_opt.ts_recent;
                 tcptw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
+                tcptw->tw_ts_offset     = tp->tsoffset;
 
 #if IS_ENABLED(CONFIG_IPV6)
                 if (tw->tw_family == PF_INET6) {
@@ -499,6 +500,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
                         newtp->rx_opt.ts_recent_stamp = 0;
                         newtp->tcp_header_len = sizeof(struct tcphdr);
                 }
+                newtp->tsoffset = 0;
 #ifdef CONFIG_TCP_MD5SIG
                 newtp->md5sig_info = NULL;      /*XXX*/
                 if (newtp->af_specific->md5_lookup(sk, newsk))