Drivers: hv: kvp: Cleanup error handling in KVP

In preparation to implementing IP injection, cleanup the way we propagate
and handle errors both in the driver as well as in the user level daemon.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 91 insertions, 23 deletions

diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index 0012eed6d872..eb4d0730f44d 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -48,13 +48,24 @@ static struct {
 	void *kvp_context; /* for the channel callback */
 } kvp_transaction;
 
+/*
+ * Before we can accept KVP messages from the host, we need
+ * to handshake with the user level daemon. This state tracks
+ * if we are in the handshake phase.
+ */
+static bool in_hand_shake = true;
+
+/*
+ * This state maintains the version number registered by the daemon.
+ */
+static int dm_reg_value;
+
 static void kvp_send_key(struct work_struct *dummy);
 
-#define TIMEOUT_FIRED 1
 
 static void kvp_respond_to_host(char *key, char *value, int error);
 static void kvp_work_func(struct work_struct *dummy);
-static void kvp_register(void);
+static void kvp_register(int);
 
 static DECLARE_DELAYED_WORK(kvp_work, kvp_work_func);
 static DECLARE_WORK(kvp_sendkey_work, kvp_send_key);
@@ -68,7 +79,7 @@ static u8 *recv_buffer;
  */
 
 static void
-kvp_register(void)
+kvp_register(int reg_value)
 {
 
 	struct cn_msg *msg;
@@ -83,7 +94,7 @@ kvp_register(void)
 		msg->id.idx =  CN_KVP_IDX;
 		msg->id.val = CN_KVP_VAL;
 
-		kvp_msg->kvp_hdr.operation = KVP_OP_REGISTER;
+		kvp_msg->kvp_hdr.operation = reg_value;
 		strcpy(version, HV_DRV_VERSION);
 		msg->len = sizeof(struct hv_kvp_msg);
 		cn_netlink_send(msg, 0, GFP_ATOMIC);
@@ -97,9 +108,43 @@ kvp_work_func(struct work_struct *dummy)
 	 * If the timer fires, the user-mode component has not responded;
 	 * process the pending transaction.
 	 */
-	kvp_respond_to_host("Unknown key", "Guest timed out", TIMEOUT_FIRED);
+	kvp_respond_to_host("Unknown key", "Guest timed out", HV_E_FAIL);
+}
+
+static int kvp_handle_handshake(struct hv_kvp_msg *msg)
+{
+	int ret = 1;
+
+	switch (msg->kvp_hdr.operation) {
+	case KVP_OP_REGISTER:
+		dm_reg_value = KVP_OP_REGISTER;
+		pr_info("KVP: IP injection functionality not available\n");
+		pr_info("KVP: Upgrade the KVP daemon\n");
+		break;
+	case KVP_OP_REGISTER1:
+		dm_reg_value = KVP_OP_REGISTER1;
+		break;
+	default:
+		pr_info("KVP: incompatible daemon\n");
+		pr_info("KVP: KVP version: %d, Daemon version: %d\n",
+			KVP_OP_REGISTER1, msg->kvp_hdr.operation);
+		ret = 0;
+	}
+
+	if (ret) {
+		/*
+		 * We have a compatible daemon; complete the handshake.
+		 */
+		pr_info("KVP: user-mode registering done.\n");
+		kvp_register(dm_reg_value);
+		kvp_transaction.active = false;
+		if (kvp_transaction.kvp_context)
+			hv_kvp_onchannelcallback(kvp_transaction.kvp_context);
+	}
+	return ret;
 }
 
+
 /*
  * Callback when data is received from user mode.
  */
@@ -109,27 +154,52 @@ kvp_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 {
 	struct hv_kvp_msg *message;
 	struct hv_kvp_msg_enumerate *data;
+	int	error = 0;
 
 	message = (struct hv_kvp_msg *)msg->data;
-	switch (message->kvp_hdr.operation) {
+
+	/*
+	 * If we are negotiating the version information
+	 * with the daemon; handle that first.
+	 */
+
+	if (in_hand_shake) {
+		if (kvp_handle_handshake(message))
+			in_hand_shake = false;
+		return;
+	}
+
+	/*
+	 * Based on the version of the daemon, we propagate errors from the
+	 * daemon differently.
+	 */
+
+	data = &message->body.kvp_enum_data;
+
+	switch (dm_reg_value) {
 	case KVP_OP_REGISTER:
-		pr_info("KVP: user-mode registering done.\n");
-		kvp_register();
-		kvp_transaction.active = false;
-		hv_kvp_onchannelcallback(kvp_transaction.kvp_context);
+		/*
+		 * Null string is used to pass back error condition.
+		 */
+		if (data->data.key[0] == 0)
+			error = HV_S_CONT;
 		break;
 
-	default:
-		data = &message->body.kvp_enum_data;
+	case KVP_OP_REGISTER1:
 		/*
-		 * Complete the transaction by forwarding the key value
-		 * to the host. But first, cancel the timeout.
+		 * We use the message header information from
+		 * the user level daemon to transmit errors.
 		 */
-		if (cancel_delayed_work_sync(&kvp_work))
-			kvp_respond_to_host(data->data.key,
-					 data->data.value,
-					!strlen(data->data.key));
+		error = message->error;
+		break;
 	}
+
+	/*
+	 * Complete the transaction by forwarding the key value
+	 * to the host. But first, cancel the timeout.
+	 */
+	if (cancel_delayed_work_sync(&kvp_work))
+		kvp_respond_to_host(data->data.key, data->data.value, error);
 }
 
 static void
@@ -287,6 +357,7 @@ kvp_respond_to_host(char *key, char *value, int error)
 		 */
 		return;
 
+	icmsghdrp->status = error;
 
 	/*
 	 * If the error parameter is set, terminate the host's enumeration
@@ -294,15 +365,12 @@ kvp_respond_to_host(char *key, char *value, int error)
 	 */
 	if (error) {
 		/*
-		 * Something failed or the we have timedout;
-		 * terminate the current  host-side iteration.
+		 * Something failed or we have timedout;
+		 * terminate the current host-side iteration.
 		 */
-		icmsghdrp->status = HV_S_CONT;
 		goto response_done;
 	}
 
-	icmsghdrp->status = HV_S_OK;
-
 	kvp_msg = (struct hv_kvp_msg *)
 			&recv_buffer[sizeof(struct vmbuspipe_hdr) +
 			sizeof(struct icmsg_hdr)];