[PATCH net-next 3/4] tcp: consistently account for overhead in rcv_wscale calculation
From: Heath Caldwell <hidden>
Date: 2021-01-12 00:36:33
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
When calculating the window scale to use for the advertised window for a TCP connection, adjust the size values used to extend the maximum possible window value so that overhead is properly accounted. In other words: convert the maximum value candidates from buffer size space into advertised window space. This adjustment keeps the scale of the maximum value consistent - that is, keeps it in window space. Without this adjustment, the window scale used could be larger than necessary, reducing granularity for the advertised window. Signed-off-by: Heath Caldwell <redacted> --- net/ipv4/tcp_output.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f322e798a351..1d2773cd02c8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c@@ -240,8 +240,12 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss, *rcv_wscale = 0; if (wscale_ok) { /* Set window scaling on max possible window */ - space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]); - space = max_t(u32, space, sysctl_rmem_max); + space = max_t(u32, space, + tcp_win_from_space( + sk, + sock_net(sk)->ipv4.sysctl_tcp_rmem[2])); + space = max_t(u32, space, + tcp_win_from_space(sk, sysctl_rmem_max)); space = min_t(u32, space, *window_clamp); *rcv_wscale = clamp_t(int, ilog2(space) - 15, 0, TCP_MAX_WSCALE);
--
2.28.0