Handles RFC4138 shortcoming (in step 2); it should also have case
c) which ignores ACKs that are not duplicates nor advance window
(opposite dir data, winupdate).
Signed-off-by: Ilpo Järvinen <[EMAIL PROTECTED]>
---
net/ipv4/tcp_input.c | 13 ++++++++++---
1 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d1e731f..5831daa 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2495,9 +2495,9 @@ static void tcp_conservative_spur_to_res
/* F-RTO spurious RTO detection algorithm (RFC4138)
*
- * F-RTO affects during two new ACKs following RTO. State (ACK number) is kept
- * in frto_counter. When ACK advances window (but not to or beyond highest
- * sequence sent before RTO):
+ * F-RTO affects during two new ACKs following RTO (well, almost, see inline
+ * comments). State (ACK number) is kept in frto_counter. When ACK advances
+ * window (but not to or beyond highest sequence sent before RTO):
* On First ACK, send two new segments out.
* On Second ACK, RTO was likely spurious. Do spurious response (response
* algorithm is not part of the F-RTO detection algorithm
@@ -2527,6 +2527,13 @@ static void tcp_process_frto(struct sock
if (flag&FLAG_DATA_ACKED)
inet_csk(sk)->icsk_retransmits = 0;
+ /* RFC4138 shortcoming in step 2; should also have case c): ACK isn't
+ * duplicate nor advances window, e.g., opposite dir data, winupdate
+ */
+ if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) &&
+ !(flag&FLAG_FORWARD_PROGRESS))
+ return;
+
if (tp->snd_una == prior_snd_una ||
!before(tp->snd_una, tp->frto_highmark)) {
tcp_enter_frto_loss(sk);
--
1.4.2
-
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