tcp: remove early retransmit

This patch removes the support of RFC5827 early retransmit (i.e.,
fast recovery on small inflight with <3 dupacks) because it is
subsumed by the new RACK loss detection. More specifically when
RACK receives DUPACKs, it'll arm a reordering timer to start fast
recovery after a quarter of (min)RTT, hence it covers the early
retransmit except RACK does not limit itself to specific inflight
or dupack numbers.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 14 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 7dd65c9cf707..7de2cf79e16f 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -246,21 +246,12 @@ tcp_dsack - BOOLEAN
         Allows TCP to send "duplicate" SACKs.
 
 tcp_early_retrans - INTEGER
-        Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold
-        for triggering fast retransmit when the amount of outstanding data is
-        small and when no previously unsent data can be transmitted (such
-        that limited transmit could be used). Also controls the use of
-        Tail loss probe (TLP) that converts RTOs occurring due to tail
-        losses into fast recovery (draft-dukkipati-tcpm-tcp-loss-probe-01).
+        Tail loss probe (TLP) converts RTOs occurring due to tail
+        losses into fast recovery (draft-ietf-tcpm-rack). Note that
+        TLP requires RACK to function properly (see tcp_recovery below)
         Possible values:
-                0 disables ER
-                1 enables ER
-                2 enables ER but delays fast recovery and fast retransmit
-                  by a fourth of RTT. This mitigates connection falsely
-                  recovers when network has a small degree of reordering
-                  (less than 3 packets).
-                3 enables delayed ER and TLP.
-                4 enables TLP only.
+                0 disables TLP
+                3 or 4 enables TLP
         Default: 3
 
 tcp_ecn - INTEGER