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Subject[ 33/72] tcp: fix range tcp_shifted_skb() passes to tcp_sacktag_one()
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Neal Cardwell <ncardwell@google.com>

[ 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>
---
net/ipv4/tcp_input.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1391,6 +1391,9 @@ static u8 tcp_sacktag_one(struct sock *s
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,
@@ -1398,12 +1401,11 @@ static int tcp_shifted_skb(struct sock *
{
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;

@@ -1427,12 +1429,11 @@ static int tcp_shifted_skb(struct sock *
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);



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