Hi all,
While I read __tcp_select_window() code, I find that it maybe return a
smaller window.
Below is one scenario I thought, may be not right:
In function __tcp_select_window(), assume:
full_space is 6mss, free_space is 2mss, tp->rcv_wnd is 3MSS.
And assume disable window scaling, then
window = tp->rcv_wnd > free_space && window > free_space
then it will round down free_space and return it.
Is this expected behavior? The comment is also saying
"Get the largest window that is a nice multiple of mss."
Should we do something like below ? Or I miss something?
I don't know how to verify it now.
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2680,9 +2680,9 @@ u32 __tcp_select_window(struct sock *sk)
* We also don't do any window rounding when the free space
* is too small.
*/
- if (window <= free_space - mss || window > free_space)
+ if (window <= free_space - mss)
window = rounddown(free_space, mss);
- else if (mss == full_space &&
+ else if (window <= free_space && mss == full_space &&
free_space > window + (full_space >> 1))
window = free_space;
}
Thanks.
