tcp: early retransmit: delayed fast retransmit
Implementing the advanced early retransmit (sysctl_tcp_early_retrans==2).
Delays the fast retransmit by an interval of RTT/4. We borrow the
RTO timer to implement the delay. If we receive another ACK or send
a new packet, the timer is cancelled and restored to original RTO
value offset by time elapsed. When the delayed-ER timer fires,
we enter fast recovery and perform fast retransmit.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 7859b41..d9b42c5be 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -372,7 +372,8 @@
repair : 1,
unused : 1;
u8 repair_queue;
- u8 do_early_retrans:1;/* Enable RFC5827 early-retransmit */
+ u8 do_early_retrans:1,/* Enable RFC5827 early-retransmit */
+ early_retrans_delayed:1; /* Delayed ER timer installed */
/* RTT measurement */
u32 srtt; /* smoothed round trip time << 3 */