tcp: send packets with a socket timestamp

A socket timestamp is a sum of the global tcp_time_stamp and
a per-socket offset.

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.

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>

1 files changed, 7 insertions, 1 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index ea678b62e94f..d9bfaea34322 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3860,7 +3860,7 @@ static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr
                 ++ptr;
                 tp->rx_opt.rcv_tsval = ntohl(*ptr);
                 ++ptr;
-                tp->rx_opt.rcv_tsecr = ntohl(*ptr);
+                tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
                 return true;
         }
         return false;
@@ -3884,7 +3884,11 @@ static bool tcp_fast_parse_options(const struct sk_buff *skb,
                 if (tcp_parse_aligned_timestamp(tp, th))
                         return true;
         }
+
         tcp_parse_options(skb, &tp->rx_opt, hvpp, 1, NULL);
+        if (tp->rx_opt.saw_tstamp)
+                tp->rx_opt.rcv_tsecr -= tp->tsoffset;
+
         return true;
 }
 
@@ -5665,6 +5669,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
         int saved_clamp = tp->rx_opt.mss_clamp;
 
         tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, &foc);
+        if (tp->rx_opt.saw_tstamp)
+                tp->rx_opt.rcv_tsecr -= tp->tsoffset;
 
         if (th->ack) {
                 /* rfc793: