[TCP] FRTO: Clear frto_highmark only after process_frto that uses it

I broke this in commit 3de96471bd7fb76406e975ef6387abe3a0698149:

	[TCP]: Wrap-safed reordering detection FRTO check

tcp_process_frto should always see a valid frto_highmark. An invalid
frto_highmark (zero) is very likely what ultimately caused a seqno
compare in tcp_frto_enter_loss to do the wrong leading to the LOST-bit
leak.

Having LOST-bits integry ensured like done after commit
23aeeec365dcf8bc87fae44c533e50d0bb4f23cc:

	[TCP] FRTO: Plug potential LOST-bit leak

won't hurt. It may still be useful in some other, possibly legimate,
scenario.

Reported by Chazarain Guillaume <guichaz@yahoo.fr>.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3f126ece8eb5..0f0c1c9829a1 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3113,11 +3113,11 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
         /* See if we can take anything off of the retransmit queue. */
         flag |= tcp_clean_rtx_queue(sk, &seq_rtt, prior_fackets);
 
+        if (tp->frto_counter)
+                frto_cwnd = tcp_process_frto(sk, flag);
         /* Guarantee sacktag reordering detection against wrap-arounds */
         if (before(tp->frto_highmark, tp->snd_una))
                 tp->frto_highmark = 0;
-        if (tp->frto_counter)
-                frto_cwnd = tcp_process_frto(sk, flag);
 
         if (tcp_ack_is_dubious(sk, flag)) {
                 /* Advance CWND, if state allows this. */