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, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a75c48f62e27..ed6606cf5b3e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3759,11 +3759,12 @@ void tcp_parse_options(const struct sk_buff *skb,
                                     !estab && sysctl_tcp_window_scaling) {
                                         __u8 snd_wscale = *(__u8 *)ptr;
                                         opt_rx->wscale_ok = 1;
-                                        if (snd_wscale > 14) {
-                                                net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
+                                        if (snd_wscale > TCP_MAX_WSCALE) {
+                                                net_info_ratelimited("%s: Illegal window scaling value %d > %u received\n",
                                                                      __func__,
-                                                                     snd_wscale);
-                                                snd_wscale = 14;
+                                                                     snd_wscale,
+                                                                     TCP_MAX_WSCALE);
+                                                snd_wscale = TCP_MAX_WSCALE;
                                         }
                                         opt_rx->snd_wscale = snd_wscale;
                                 }