tcp: consolidate paws check

Wow, it was quite tricky to merge that stream of negations
but I think I finally got it right:

check & replace_ts_recent:
(s32)(rcv_tsval - ts_recent) >= 0                  => 0
(s32)(ts_recent - rcv_tsval) <= 0                  => 0

discard:
(s32)(ts_recent - rcv_tsval)  > TCP_PAWS_WINDOW    => 1
(s32)(ts_recent - rcv_tsval) <= TCP_PAWS_WINDOW    => 0

I toggled the return values of tcp_paws_check around since
the old encoding added yet-another negation making tracking
of truth-values really complicated.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 6 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f527a16a7b33..b7d02c5dd6da 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3883,8 +3883,7 @@ static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
                  * Not only, also it occurs for expired timestamps.
                  */
 
-                if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
-                   get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
+                if (tcp_paws_check(&tp->rx_opt, 0))
                         tcp_store_ts_recent(tp);
         }
 }
@@ -3936,9 +3935,9 @@ static inline int tcp_paws_discard(const struct sock *sk,
                                    const struct sk_buff *skb)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
-        return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
-                get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
-                !tcp_disordered_ack(sk, skb));
+
+        return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
+               !tcp_disordered_ack(sk, skb);
 }
 
 /* Check segment sequence number for validity.
@@ -5513,7 +5512,7 @@ discard:
 
         /* PAWS check. */
         if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
-            tcp_paws_check(&tp->rx_opt, 0))
+            tcp_paws_reject(&tp->rx_opt, 0))
                 goto discard_and_undo;
 
         if (th->syn) {