libceph: add nocephx_sign_messages option

Support for message signing was merged into 3.19, along with
nocephx_require_signatures option.  But, all that option does is allow
the kernel client to talk to clusters that don't support MSG_AUTH
feature bit.  That's pretty useless, given that it's been supported
since bobtail.

Meanwhile, if one disables message signing on the server side with
"cephx sign messages = false", it becomes impossible to use the kernel
client since it expects messages to be signed if MSG_AUTH was
negotiated.  Add nocephx_sign_messages option to support this use case.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
diff --git a/net/ceph/auth_x.c b/net/ceph/auth_x.c
index 3a544ca..10d87753 100644
--- a/net/ceph/auth_x.c
+++ b/net/ceph/auth_x.c
@@ -8,6 +8,7 @@
 
 #include <linux/ceph/decode.h>
 #include <linux/ceph/auth.h>
+#include <linux/ceph/libceph.h>
 #include <linux/ceph/messenger.h>
 
 #include "crypto.h"
@@ -698,6 +699,9 @@
 {
 	int ret;
 
+	if (ceph_test_opt(from_msgr(msg->con->msgr), NOMSGSIGN))
+		return 0;
+
 	ret = calcu_signature((struct ceph_x_authorizer *)auth->authorizer,
 			      msg, &msg->footer.sig);
 	if (ret < 0)
@@ -712,6 +716,9 @@
 	__le64 sig_check;
 	int ret;
 
+	if (ceph_test_opt(from_msgr(msg->con->msgr), NOMSGSIGN))
+		return 0;
+
 	ret = calcu_signature((struct ceph_x_authorizer *)auth->authorizer,
 			      msg, &sig_check);
 	if (ret < 0)
diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
index d1494d1..6b4d3a1 100644
--- a/net/ceph/ceph_common.c
+++ b/net/ceph/ceph_common.c
@@ -245,6 +245,8 @@
 	Opt_nocrc,
 	Opt_cephx_require_signatures,
 	Opt_nocephx_require_signatures,
+	Opt_cephx_sign_messages,
+	Opt_nocephx_sign_messages,
 	Opt_tcp_nodelay,
 	Opt_notcp_nodelay,
 };
@@ -267,6 +269,8 @@
 	{Opt_nocrc, "nocrc"},
 	{Opt_cephx_require_signatures, "cephx_require_signatures"},
 	{Opt_nocephx_require_signatures, "nocephx_require_signatures"},
+	{Opt_cephx_sign_messages, "cephx_sign_messages"},
+	{Opt_nocephx_sign_messages, "nocephx_sign_messages"},
 	{Opt_tcp_nodelay, "tcp_nodelay"},
 	{Opt_notcp_nodelay, "notcp_nodelay"},
 	{-1, NULL}
@@ -491,6 +495,12 @@
 		case Opt_nocephx_require_signatures:
 			opt->flags |= CEPH_OPT_NOMSGAUTH;
 			break;
+		case Opt_cephx_sign_messages:
+			opt->flags &= ~CEPH_OPT_NOMSGSIGN;
+			break;
+		case Opt_nocephx_sign_messages:
+			opt->flags |= CEPH_OPT_NOMSGSIGN;
+			break;
 
 		case Opt_tcp_nodelay:
 			opt->flags |= CEPH_OPT_TCP_NODELAY;
@@ -534,6 +544,8 @@
 		seq_puts(m, "nocrc,");
 	if (opt->flags & CEPH_OPT_NOMSGAUTH)
 		seq_puts(m, "nocephx_require_signatures,");
+	if (opt->flags & CEPH_OPT_NOMSGSIGN)
+		seq_puts(m, "nocephx_sign_messages,");
 	if ((opt->flags & CEPH_OPT_TCP_NODELAY) == 0)
 		seq_puts(m, "notcp_nodelay,");
 
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 1110807..0cc5608 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2677,7 +2677,7 @@
 		if (ret <= 0) {
 			switch (ret) {
 			case -EBADMSG:
-				con->error_msg = "bad crc";
+				con->error_msg = "bad crc/signature";
 				/* fall through */
 			case -EBADE:
 				ret = -EIO;