tcp: add tcp_sock_set_keepintvl

Add a helper to directly set the TCP_KEEPINTVL sockopt from kernel space
without going through a fake uaccess.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index bdf0ff9..7eb083e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2934,6 +2934,18 @@ int tcp_sock_set_keepidle(struct sock *sk, int val)
 }
 EXPORT_SYMBOL(tcp_sock_set_keepidle);
 
+int tcp_sock_set_keepintvl(struct sock *sk, int val)
+{
+	if (val < 1 || val > MAX_TCP_KEEPINTVL)
+		return -EINVAL;
+
+	lock_sock(sk);
+	tcp_sk(sk)->keepalive_intvl = val * HZ;
+	release_sock(sk);
+	return 0;
+}
+EXPORT_SYMBOL(tcp_sock_set_keepintvl);
+
 /*
  *	Socket option code for TCP.
  */