net: tcp: Define the TCP_MAX_WSCALE instead of literal number 14

Define one new macro TCP_MAX_WSCALE instead of literal number '14',
and use U16_MAX instead of 65535 as the max value of TCP window.
There is another minor change, use rounddown(space, mss) instead of
(space / mss) * mss;

Signed-off-by: Gao Feng <fgao@ikuai8.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 7 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 13971942211b..0e807a83c1bc 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -212,12 +212,12 @@ void tcp_select_initial_window(int __space, __u32 mss,
 
         /* If no clamp set the clamp to the max possible scaled window */
         if (*window_clamp == 0)
-                (*window_clamp) = (65535 << 14);
+                (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
         space = min(*window_clamp, space);
 
         /* Quantize space offering to a multiple of mss if possible. */
         if (space > mss)
-                space = (space / mss) * mss;
+                space = rounddown(space, mss);
 
         /* NOTE: offering an initial window larger than 32767
          * will break some buggy TCP stacks. If the admin tells us
@@ -234,13 +234,11 @@ void tcp_select_initial_window(int __space, __u32 mss,
 
         (*rcv_wscale) = 0;
         if (wscale_ok) {
-                /* Set window scaling on max possible window
-                 * See RFC1323 for an explanation of the limit to 14
-                 */
+                /* Set window scaling on max possible window */
                 space = max_t(u32, space, sysctl_tcp_rmem[2]);
                 space = max_t(u32, space, sysctl_rmem_max);
                 space = min_t(u32, space, *window_clamp);
-                while (space > 65535 && (*rcv_wscale) < 14) {
+                while (space > U16_MAX && (*rcv_wscale) < TCP_MAX_WSCALE) {
                         space >>= 1;
                         (*rcv_wscale)++;
                 }
@@ -253,7 +251,7 @@ void tcp_select_initial_window(int __space, __u32 mss,
         }
 
         /* Set the clamp no higher than max representable value */
-        (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
+        (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
 }
 EXPORT_SYMBOL(tcp_select_initial_window);