[TCP]: Add tcp_slow_start_after_idle sysctl.
A lot of people have asked for a way to disable tcp_cwnd_restart(),
and it seems reasonable to add a sysctl to do that.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index e7fb665..ce4cd5f 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -690,6 +690,14 @@
.proc_handler = &proc_dointvec
},
#endif
+ {
+ .ctl_name = NET_TCP_SLOW_START_AFTER_IDLE,
+ .procname = "tcp_slow_start_after_idle",
+ .data = &sysctl_tcp_slow_start_after_idle,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec
+ },
{ .ctl_name = 0 }
};
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f33c9dd..07bb5a2 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -59,6 +59,9 @@
int sysctl_tcp_mtu_probing = 0;
int sysctl_tcp_base_mss = 512;
+/* By default, RFC2861 behavior. */
+int sysctl_tcp_slow_start_after_idle = 1;
+
static void update_send_head(struct sock *sk, struct tcp_sock *tp,
struct sk_buff *skb)
{
@@ -138,7 +141,8 @@
struct inet_connection_sock *icsk = inet_csk(sk);
const u32 now = tcp_time_stamp;
- if (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)
+ if (sysctl_tcp_slow_start_after_idle &&
+ (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
tcp_cwnd_restart(sk, __sk_dst_get(sk));
tp->lsndtime = now;
