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authorlaurent chavey <chavey@google.com>2009-12-15 11:15:28 +0000
committerDavid S. Miller <davem@davemloft.net>2009-12-23 14:13:30 -0800
commit31d12926e37291970dd4f6e9940df3897766a81d (patch)
tree7f20713b70fc2c9e03aa1f7fcf71ffa651c464fc /net/ipv4/tcp_output.c
parent068a2de57ddf4f472e32e7af868613c574ad1d88 (diff)
net: Add rtnetlink init_rcvwnd to set the TCP initial receive window
Add rtnetlink init_rcvwnd to set the TCP initial receive window size advertised by passive and active TCP connections. The current Linux TCP implementation limits the advertised TCP initial receive window to the one prescribed by slow start. For short lived TCP connections used for transaction type of traffic (i.e. http requests), bounding the advertised TCP initial receive window results in increased latency to complete the transaction. Support for setting initial congestion window is already supported using rtnetlink init_cwnd, but the feature is useless without the ability to set a larger TCP initial receive window. The rtnetlink init_rcvwnd allows increasing the TCP initial receive window, allowing TCP connection to advertise larger TCP receive window than the ones bounded by slow start. Signed-off-by: Laurent Chavey <chavey@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_output.c')
-rw-r--r--net/ipv4/tcp_output.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 12b2af36eab8..4a1605d3f909 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -183,7 +183,8 @@ static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
*/
void tcp_select_initial_window(int __space, __u32 mss,
__u32 *rcv_wnd, __u32 *window_clamp,
- int wscale_ok, __u8 *rcv_wscale)
+ int wscale_ok, __u8 *rcv_wscale,
+ __u32 init_rcv_wnd)
{
unsigned int space = (__space < 0 ? 0 : __space);
@@ -232,7 +233,13 @@ void tcp_select_initial_window(int __space, __u32 mss,
init_cwnd = 2;
else if (mss > 1460)
init_cwnd = 3;
- if (*rcv_wnd > init_cwnd * mss)
+ /* when initializing use the value from init_rcv_wnd
+ * rather than the default from above
+ */
+ if (init_rcv_wnd &&
+ (*rcv_wnd > init_rcv_wnd * mss))
+ *rcv_wnd = init_rcv_wnd * mss;
+ else if (*rcv_wnd > init_cwnd * mss)
*rcv_wnd = init_cwnd * mss;
}
@@ -2417,7 +2424,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
&req->rcv_wnd,
&req->window_clamp,
ireq->wscale_ok,
- &rcv_wscale);
+ &rcv_wscale,
+ dst_metric(dst, RTAX_INITRWND));
ireq->rcv_wscale = rcv_wscale;
}
@@ -2544,7 +2552,8 @@ static void tcp_connect_init(struct sock *sk)
&tp->rcv_wnd,
&tp->window_clamp,
sysctl_tcp_window_scaling,
- &rcv_wscale);
+ &rcv_wscale,
+ dst_metric(dst, RTAX_INITRWND));
tp->rx_opt.rcv_wscale = rcv_wscale;
tp->rcv_ssthresh = tp->rcv_wnd;