[PATCH net 1/1] net: tcp: Permit user set TCP_MAXSEG to default value

[fgao]

From: Gao Feng <f...@ikuai8.com>

When user_mss is zero, it means use the default value. But the current
codes don't permit user set TCP_MAXSEG to the default value.
It would return the -EINVAL when val is zero.

Signed-off-by: Gao Feng <f...@ikuai8.com>
---
 net/ipv4/tcp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1e319a5..dd5e8e2 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2470,7 +2470,8 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
                /* Values greater than interface MTU won't take effect. However
                 * at the point when this call is done we typically don't yet
                 * know which interface is going to be used */
-               if (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW) {
+               if (val < 0 || (val > 0 && val < TCP_MIN_MSS) ||
+                   val > MAX_TCP_WINDOW) {
                        err = -EINVAL;
                        break;
                }
-- 
1.9.1