[TCP]: Add two new spurious RTO responses to FRTO

New sysctl tcp_frto_response is added to select amongst these
responses:
	- Rate halving based; reuses CA_CWR state (default)
	- Very conservative; used to be the only one available (=1)
	- Undo cwr; undoes ssthresh and cwnd reductions (=2)

The response with rate halving requires a new parameter to
tcp_enter_cwr because FRTO has already reduced ssthresh and
doing a second reduction there has to be prevented. In addition,
to keep things nice on 80 cols screen, a local variable was
added.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index d68effe98e8d..6817d6485df5 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -647,6 +647,14 @@ ctl_table ipv4_table[] = {
                 .proc_handler   = &proc_dointvec
         },
         {
+                .ctl_name       = NET_TCP_FRTO_RESPONSE,
+                .procname       = "tcp_frto_response",
+                .data           = &sysctl_tcp_frto_response,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec
+        },
+        {
                 .ctl_name       = NET_TCP_LOW_LATENCY,
                 .procname       = "tcp_low_latency",
                 .data           = &sysctl_tcp_low_latency,