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net: tcp: Refine the __tcp_select_window 

1. Move the "window = tp->rcv_wnd;" into the condition block without
tp->rx_opt.rcv_wscale.
Because it is unnecessary when enable wscale;

2. Use the macro ALIGN instead of two statements.
The two statements are used to make window align to 1<<wscale.
Use the ALIGN is more clearer.

3. Use the rounddown to make codes clearer.

Signed-off-by: Gao Feng <fgao@ikuai8.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gao Feng 2017-03-30 06:49:19 +08:00 committed by David S. Miller
parent bae76dd95b
commit 1935299d9c
1 changed files with 3 additions and 5 deletions
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8
net/ipv4/tcp_output.c
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@ -2561,7 +2561,6 @@ u32 __tcp_select_window(struct sock *sk)
/* Don't do rounding if we are using window scaling, since the
* scaled window will not line up with the MSS boundary anyway.
*/
window = tp->rcv_wnd;
if (tp->rx_opt.rcv_wscale) {
window = free_space;
@ -2569,10 +2568,9 @@ u32 __tcp_select_window(struct sock *sk)
* Import case: prevent zero window announcement if
* 1<<rcv_wscale > mss.
*/
if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
window = (((window >> tp->rx_opt.rcv_wscale) + 1)
<< tp->rx_opt.rcv_wscale);
window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
} else {
window = tp->rcv_wnd;
/* Get the largest window that is a nice multiple of mss.
* Window clamp already applied above.
* If our current window offering is within 1 mss of the
@ -2582,7 +2580,7 @@ u32 __tcp_select_window(struct sock *sk)
* is too small.
*/
if (window <= free_space - mss || window > free_space)
window = (free_space / mss) * mss;
window = rounddown(free_space, mss);
else if (mss == full_space &&
free_space > window + (full_space >> 1))
window = free_space;