SUNRPC: Send TLS Closure alerts before closing a TCP socket

Before closing a TCP connection, the TLS protocol wants peers to
send session close Alert notifications. Add those in both the RPC
client and server.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://lore.kernel.org/r/169047939404.5241.14392506226409865832.stgit@oracle-102.nfsv4bat.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/sunrpc/svcsock.c

@@ -1622,6 +1622,8 @@ static void svc_tcp_sock_detach(struct svc_xprt *xprt)
 {
 	struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
 
+	tls_handshake_close(svsk->sk_sock);
+
 	svc_sock_detach(xprt);
 
 	if (!test_bit(XPT_LISTENER, &xprt->xpt_flags)) {

net/sunrpc/xprtsock.c

@@ -1293,6 +1293,8 @@ static void xs_close(struct rpc_xprt *xprt)
 
 	dprintk("RPC:       xs_close xprt %p\n", xprt);
 
+	if (transport->sock)
+		tls_handshake_close(transport->sock);
 	xs_reset_transport(transport);
 	xprt->reestablish_timeout = 0;
 }