[TCP]: Handle SACK'd packets properly in tcp_fragment().

The problem is that we're now calling tcp_fragment() in a context
where the packets might be marked as SACKED_ACKED or SACKED_RETRANS.
This was not possible before as you never retransmitted packets that
are so marked.

Because of this, we need to adjust sacked_out and retrans_out in
tcp_fragment().  This is exactly what the following patch does.

We also need to preserve the SACKED_ACKED/SACKED_RETRANS marking
if they exist.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 3 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b018e31b653..5dd6dd7d091 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -461,9 +461,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss
         flags = TCP_SKB_CB(skb)->flags;
         TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
         TCP_SKB_CB(buff)->flags = flags;
-        TCP_SKB_CB(buff)->sacked =
-                (TCP_SKB_CB(skb)->sacked &
-                 (TCPCB_LOST | TCPCB_EVER_RETRANS | TCPCB_AT_TAIL));
+        TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
         TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL;
 
         if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) {
@@ -501,6 +499,12 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss
                         tcp_skb_pcount(buff);
 
                 tp->packets_out -= diff;
+
+                if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
+                        tp->sacked_out -= diff;
+                if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
+                        tp->retrans_out -= diff;
+
                 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
                         tp->lost_out -= diff;
                         tp->left_out -= diff;