tcp: add a sysctl to config the tcp_default_init_rwnd
The default initial rwnd is hardcoded to 10.
Now we allow it to be controlled via
/proc/sys/net/ipv4/tcp_default_init_rwnd
which limits the values from 3 to 100
This is somewhat needed because ipv6 routes are
autoconfigured by the kernel.
See "An Argument for Increasing TCP's Initial Congestion Window"
in https://developers.google.com/speed/articles/tcp_initcwnd_paper.pdf
Change-Id: I386b2a9d62de0ebe05c1ebe1b4bd91b314af5c54
Signed-off-by: JP Abgrall <jpa@google.com>
Conflicts:
net/ipv4/sysctl_net_ipv4.c
net/ipv4/tcp_input.c
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 1cb67de..d9bce1c 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -151,6 +151,21 @@
return ret;
}
+/* Validate changes from /proc interface. */
+static int proc_tcp_default_init_rwnd(ctl_table *ctl, int write,
+ void __user *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ int old_value = *(int *)ctl->data;
+ int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
+ int new_value = *(int *)ctl->data;
+
+ if (write && ret == 0 && (new_value < 3 || new_value > 100))
+ *(int *)ctl->data = old_value;
+
+ return ret;
+}
+
static int proc_tcp_congestion_control(struct ctl_table *ctl, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
@@ -624,6 +639,13 @@
.proc_handler = proc_dointvec_ms_jiffies,
},
{
+ .procname = "tcp_default_init_rwnd",
+ .data = &sysctl_tcp_default_init_rwnd,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_tcp_default_init_rwnd
+ },
+ {
.procname = "icmp_msgs_per_sec",
.data = &sysctl_icmp_msgs_per_sec,
.maxlen = sizeof(int),