net: TCP thin dupack

This patch enables fast retransmissions after one dupACK for
TCP if the stream is identified as thin. This will reduce
latencies for thin streams that are not able to trigger fast
retransmissions due to high packet interarrival time. This
mechanism is only active if enabled by iocontrol or syscontrol
and the stream is identified as thin.

Signed-off-by: Andreas Petlund <apetlund@simula.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 21bae9afefea..5901010fad55 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2236,6 +2236,13 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
                         tp->thin_lto = val;
                 break;
 
+        case TCP_THIN_DUPACK:
+                if (val < 0 || val > 1)
+                        err = -EINVAL;
+                else
+                        tp->thin_dupack = val;
+                break;
+
         case TCP_CORK:
                 /* When set indicates to always queue non-full frames.
                  * Later the user clears this option and we transmit