tcp: fix range tcp_shifted_skb() passes to tcp_sacktag_one()

[ Upstream commit daef52bab1fd26e24e8e9578f8fb33ba1d0cb412 ]

Fix the newly-SACKed range to be the range of newly-shifted bytes.

Previously - since 832d11c5cd076abc0aa1eaf7be96c81d1a59ce41 -
tcp_shifted_skb() incorrectly called tcp_sacktag_one() with the start
and end sequence numbers of the skb it passes in set to the range just
beyond the range that is newly-SACKed.

This commit also removes a special-case adjustment to lost_cnt_hint in
tcp_shifted_skb() since the pre-existing adjustment of lost_cnt_hint
in tcp_sacktag_one() now properly handles this things now that the
correct start sequence number is passed in.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index af41044..78689e5 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1370,6 +1370,9 @@ static u8 tcp_sacktag_one(struct sock *sk,
        return sacked;
 }
 
+/* Shift newly-SACKed bytes from this skb to the immediately previous
+ * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
+ */
 static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
                           struct tcp_sacktag_state *state,
                           unsigned int pcount, int shifted, int mss,
@@ -1377,12 +1380,11 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
 {
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
+       u32 start_seq = TCP_SKB_CB(skb)->seq;   /* start of newly-SACKed */
+       u32 end_seq = start_seq + shifted;      /* end of newly-SACKed */
 
        BUG_ON(!pcount);
 
-       if (skb == tp->lost_skb_hint)
-               tp->lost_cnt_hint += pcount;
-
        TCP_SKB_CB(prev)->end_seq += shifted;
        TCP_SKB_CB(skb)->seq += shifted;
 
@@ -1406,12 +1408,11 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
                skb_shinfo(skb)->gso_type = 0;
        }
 
-       /* We discard results */
-       tcp_sacktag_one(sk, state,
-                       TCP_SKB_CB(skb)->sacked,
-                       TCP_SKB_CB(skb)->seq,
-                       TCP_SKB_CB(skb)->end_seq,
-                       dup_sack, pcount);
+       /* Adjust counters and hints for the newly sacked sequence range but
+        * discard the return value since prev is already marked.
+        */
+       tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
+                       start_seq, end_seq, dup_sack, pcount);
 
        /* Difference in this won't matter, both ACKed by the same cumul. ACK */
        TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);