Commit:     b8ed601cefe7a4014b93560bd846caf44f25b1c1
Parent:     1e757f9996114f713a79d3fbcd08739efcfc5c34
Author:     Ilpo Järvinen <[EMAIL PROTECTED]>
AuthorDate: Mon Jul 30 19:51:12 2007 -0700
Committer:  David S. Miller <[EMAIL PROTECTED]>
CommitDate: Tue Jul 31 02:28:31 2007 -0700

    [TCP]: Bidir flow must not disregard SACK blocks for lost marking
    It's possible that new SACK blocks that should trigger new LOST
    markings arrive with new data (which previously made is_dupack
    false). In addition, I think this fixes a case where we get
    a cumulative ACK with enough SACK blocks to trigger the fast
    recovery (is_dupack would be false there too).
    I'm not completely pleased with this solution because readability
    of the code is somewhat questionable as 'is_dupack' in SACK case
    is no longer about dupacks only but would mean something like
    'lost_marker_work_todo' too... But because of Eifel stuff done
    in CA_Recovery, the FLAG_DATA_SACKED check cannot be placed to
    the if statement which seems attractive solution. Nevertheless,
    I didn't like adding another variable just for that either... :-)
    Signed-off-by: Ilpo Järvinen <[EMAIL PROTECTED]>
    Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
 net/ipv4/tcp_input.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 41163dd..378ca8a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2112,7 +2112,10 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct tcp_sock *tp = tcp_sk(sk);
-       int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
+       int is_dupack = (tp->snd_una == prior_snd_una &&
+                        (!(flag&FLAG_NOT_DUP) ||
+                         ((flag&FLAG_DATA_SACKED) &&
+                          (tp->fackets_out > tp->reordering))));
        /* Some technical things:
         * 1. Reno does not count dupacks (sacked_out) automatically. */
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