tcp: remove pointless .dsack/.num_sacks code

In the pure assignment case, the earlier zeroing is
still in effect.

David S. Miller raised concerns if the ifs are there to avoid
dirtying cachelines. I came to these conclusions:

> We'll be dirty it anyway (now that I check), the first "real" statement
> in tcp_rcv_established is:
>
>       tp->rx_opt.saw_tstamp = 0;
>
> ...that'll land on the same dword. :-/
>
> I suppose the blocks are there just because they had more complexity
> inside when they had to calculate the eff_sacks too (maybe it would
> have been better to just remove them in that drop-patch so you would
> have had less head-ache :-)).

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

1 files changed, 2 insertions, 5 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 5ecd7aa25979..cd39d1d02dc3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4248,8 +4248,7 @@ static void tcp_sack_remove(struct tcp_sock *tp)
                 this_sack++;
                 sp++;
         }
-        if (num_sacks != tp->rx_opt.num_sacks)
-                tp->rx_opt.num_sacks = num_sacks;
+        tp->rx_opt.num_sacks = num_sacks;
 }
 
 /* This one checks to see if we can put data from the
@@ -4325,8 +4324,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 
         TCP_ECN_accept_cwr(tp, skb);
 
-        if (tp->rx_opt.dsack)
-                tp->rx_opt.dsack = 0;
+        tp->rx_opt.dsack = 0;
 
         /*  Queue data for delivery to the user.
          *  Packets in sequence go to the receive queue.
@@ -4445,7 +4443,6 @@ drop:
                 /* Initial out of order segment, build 1 SACK. */
                 if (tcp_is_sack(tp)) {
                         tp->rx_opt.num_sacks = 1;
-                        tp->rx_opt.dsack     = 0;
                         tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
                         tp->selective_acks[0].end_seq =
                                                 TCP_SKB_CB(skb)->end_seq;