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net: Add rtnetlink init_rcvwnd to set the TCP initial receive window

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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>
This commit is contained in:
laurent chavey 2009-12-15 11:15:28 +00:00 committed by David S. Miller
parent 068a2de57d
commit 31d12926e3
6 changed files with 21 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/rtnetlink.h
View File

@ -362,6 +362,8 @@ enum {
#define RTAX_FEATURES RTAX_FEATURES
RTAX_RTO_MIN,
#define RTAX_RTO_MIN RTAX_RTO_MIN
RTAX_INITRWND,
#define RTAX_INITRWND RTAX_INITRWND
__RTAX_MAX
};

2
include/net/dst.h
View File

@ -83,8 +83,6 @@ struct dst_entry {
* (L1_CACHE_SIZE would be too much)
*/
#ifdef CONFIG_64BIT
long __pad_to_align_refcnt[2];
#else
long __pad_to_align_refcnt[1];
#endif
/*

3
include/net/tcp.h
View File

@ -965,7 +965,8 @@ static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
/* Determine a window scaling and initial window to offer. */
extern 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);
static inline int tcp_win_from_space(int space)
{

3
net/ipv4/syncookies.c
View File

@ -358,7 +358,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
tcp_select_initial_window(tcp_full_space(sk), req->mss,
&req->rcv_wnd, &req->window_clamp,
ireq->wscale_ok, &rcv_wscale);
ireq->wscale_ok, &rcv_wscale,
dst_metric(&rt->u.dst, RTAX_INITRWND));
ireq->rcv_wscale = rcv_wscale;

17
net/ipv4/tcp_output.c
View File

@ -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;

3
net/ipv6/syncookies.c
View File

@ -269,7 +269,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
req->window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
tcp_select_initial_window(tcp_full_space(sk), req->mss,
&req->rcv_wnd, &req->window_clamp,
ireq->wscale_ok, &rcv_wscale);
ireq->wscale_ok, &rcv_wscale,
dst_metric(dst, RTAX_INITRWND));
ireq->rcv_wscale = rcv_wscale;