CIFS: Add echo request support for SMB2

Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsglob.h

@@ -73,6 +73,9 @@
 /*           (max path length + 1 for null) * 2 for unicode    */
 #define MAX_NAME 514
 
+/* SMB echo "timeout" -- FIXME: tunable? */
+#define SMB_ECHO_INTERVAL (60 * HZ)
+
 #include "cifspdu.h"
 
 #ifndef XATTR_DOS_ATTRIB

fs/cifs/connect.c

@@ -56,9 +56,6 @@
 #define CIFS_PORT 445
 #define RFC1001_PORT 139
 
-/* SMB echo "timeout" -- FIXME: tunable? */
-#define SMB_ECHO_INTERVAL (60 * HZ)
-
 extern mempool_t *cifs_req_poolp;
 
 /* FIXME: should these be tunable? */

fs/cifs/smb2ops.c

@@ -207,6 +207,12 @@ smb2_build_path_to_root(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
 	return NULL;
 }
 
+static bool
+smb2_can_echo(struct TCP_Server_Info *server)
+{
+	return server->echoes;
+}
+
 struct smb_version_operations smb21_operations = {
 	.setup_request = smb2_setup_request,
 	.setup_async_request = smb2_setup_async_request,
@@ -226,6 +232,8 @@ struct smb_version_operations smb21_operations = {
 	.tree_connect = SMB2_tcon,
 	.tree_disconnect = SMB2_tdis,
 	.is_path_accessible = smb2_is_path_accessible,
+	.can_echo = smb2_can_echo,
+	.echo = SMB2_echo,
 	.query_path_info = smb2_query_path_info,
 	.get_srv_inum = smb2_get_srv_inum,
 	.build_path_to_root = smb2_build_path_to_root,

fs/cifs/smb2pdu.c

@@ -1074,3 +1074,52 @@ qinf_exit:
 	free_rsp_buf(resp_buftype, rsp);
 	return rc;
 }
+
+/*
+ * This is a no-op for now. We're not really interested in the reply, but
+ * rather in the fact that the server sent one and that server->lstrp
+ * gets updated.
+ *
+ * FIXME: maybe we should consider checking that the reply matches request?
+ */
+static void
+smb2_echo_callback(struct mid_q_entry *mid)
+{
+	struct TCP_Server_Info *server = mid->callback_data;
+	struct smb2_echo_rsp *smb2 = (struct smb2_echo_rsp *)mid->resp_buf;
+	unsigned int credits_received = 1;
+
+	if (mid->mid_state == MID_RESPONSE_RECEIVED)
+		credits_received = le16_to_cpu(smb2->hdr.CreditRequest);
+
+	DeleteMidQEntry(mid);
+	add_credits(server, credits_received, CIFS_ECHO_OP);
+}
+
+int
+SMB2_echo(struct TCP_Server_Info *server)
+{
+	struct smb2_echo_req *req;
+	int rc = 0;
+	struct kvec iov;
+
+	cFYI(1, "In echo request");
+
+	rc = small_smb2_init(SMB2_ECHO, NULL, (void **)&req);
+	if (rc)
+		return rc;
+
+	req->hdr.CreditRequest = cpu_to_le16(1);
+
+	iov.iov_base = (char *)req;
+	/* 4 for rfc1002 length field */
+	iov.iov_len = get_rfc1002_length(req) + 4;
+
+	rc = cifs_call_async(server, &iov, 1, NULL, smb2_echo_callback, server,
+			     CIFS_ECHO_OP);
+	if (rc)
+		cFYI(1, "Echo request failed: %d", rc);
+
+	cifs_small_buf_release(req);
+	return rc;
+}

fs/cifs/smb2pdu.h

@@ -448,6 +448,18 @@ struct smb2_close_rsp {
 	__le32 Attributes;
 } __packed;
 
+struct smb2_echo_req {
+	struct smb2_hdr hdr;
+	__le16 StructureSize;	/* Must be 4 */
+	__u16  Reserved;
+} __packed;
+
+struct smb2_echo_rsp {
+	struct smb2_hdr hdr;
+	__le16 StructureSize;	/* Must be 4 */
+	__u16  Reserved;
+} __packed;
+
 /* Possible InfoType values */
 #define SMB2_O_INFO_FILE	0x01
 #define SMB2_O_INFO_FILESYSTEM	0x02

fs/cifs/smb2proto.h

@@ -73,5 +73,6 @@ extern int SMB2_close(const unsigned int xid, struct cifs_tcon *tcon,
 extern int SMB2_query_info(const unsigned int xid, struct cifs_tcon *tcon,
 			   u64 persistent_file_id, u64 volatile_file_id,
 			   struct smb2_file_all_info *data);
+extern int SMB2_echo(struct TCP_Server_Info *server);
 
 #endif			/* _SMB2PROTO_H */