VMCI: routing implementation.

VMCI routing code is responsible for routing between various hosts/guests as well as
routing in nested scenarios.

Signed-off-by: George Zhang <[e-mail]>
Acked-by: Andy king <[e-mail]>
Acked-by: Dmitry Torokhov <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/vmw_vmci/vmci_route.c

···
+/*
+ * VMware VMCI Driver
+ *
+ * Copyright (C) 2012 VMware, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation version 2 and no later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#include <linux/vmw_vmci_defs.h>
+#include <linux/vmw_vmci_api.h>
+
+#include "vmci_context.h"
+#include "vmci_driver.h"
+#include "vmci_route.h"
+
+/*
+ * Make a routing decision for the given source and destination handles.
+ * This will try to determine the route using the handles and the available
+ * devices.  Will set the source context if it is invalid.
+ */
+int vmci_route(struct vmci_handle *src,
+	       const struct vmci_handle *dst,
+	       bool from_guest,
+	       enum vmci_route *route)
+{
+	bool has_host_device = vmci_host_code_active();
+	bool has_guest_device = vmci_guest_code_active();
+
+	*route = VMCI_ROUTE_NONE;
+
+	/*
+	 * "from_guest" is only ever set to true by
+	 * IOCTL_VMCI_DATAGRAM_SEND (or by the vmkernel equivalent),
+	 * which comes from the VMX, so we know it is coming from a
+	 * guest.
+	 *
+	 * To avoid inconsistencies, test these once.  We will test
+	 * them again when we do the actual send to ensure that we do
+	 * not touch a non-existent device.
+	 */
+
+	/* Must have a valid destination context. */
+	if (VMCI_INVALID_ID == dst->context)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	/* Anywhere to hypervisor. */
+	if (VMCI_HYPERVISOR_CONTEXT_ID == dst->context) {
+
+		/*
+		 * If this message already came from a guest then we
+		 * cannot send it to the hypervisor.  It must come
+		 * from a local client.
+		 */
+		if (from_guest)
+			return VMCI_ERROR_DST_UNREACHABLE;
+
+		/*
+		 * We must be acting as a guest in order to send to
+		 * the hypervisor.
+		 */
+		if (!has_guest_device)
+			return VMCI_ERROR_DEVICE_NOT_FOUND;
+
+		/* And we cannot send if the source is the host context. */
+		if (VMCI_HOST_CONTEXT_ID == src->context)
+			return VMCI_ERROR_INVALID_ARGS;
+
+		/*
+		 * If the client passed the ANON source handle then
+		 * respect it (both context and resource are invalid).
+		 * However, if they passed only an invalid context,
+		 * then they probably mean ANY, in which case we
+		 * should set the real context here before passing it
+		 * down.
+		 */
+		if (VMCI_INVALID_ID == src->context &&
+		    VMCI_INVALID_ID != src->resource)
+			src->context = vmci_get_context_id();
+
+		/* Send from local client down to the hypervisor. */
+		*route = VMCI_ROUTE_AS_GUEST;
+		return VMCI_SUCCESS;
+	}
+
+	/* Anywhere to local client on host. */
+	if (VMCI_HOST_CONTEXT_ID == dst->context) {
+		/*
+		 * If it is not from a guest but we are acting as a
+		 * guest, then we need to send it down to the host.
+		 * Note that if we are also acting as a host then this
+		 * will prevent us from sending from local client to
+		 * local client, but we accept that restriction as a
+		 * way to remove any ambiguity from the host context.
+		 */
+		if (src->context == VMCI_HYPERVISOR_CONTEXT_ID) {
+			/*
+			 * If the hypervisor is the source, this is
+			 * host local communication. The hypervisor
+			 * may send vmci event datagrams to the host
+			 * itself, but it will never send datagrams to
+			 * an "outer host" through the guest device.
+			 */
+
+			if (has_host_device) {
+				*route = VMCI_ROUTE_AS_HOST;
+				return VMCI_SUCCESS;
+			} else {
+				return VMCI_ERROR_DEVICE_NOT_FOUND;
+			}
+		}
+
+		if (!from_guest && has_guest_device) {
+			/* If no source context then use the current. */
+			if (VMCI_INVALID_ID == src->context)
+				src->context = vmci_get_context_id();
+
+			/* Send it from local client down to the host. */
+			*route = VMCI_ROUTE_AS_GUEST;
+			return VMCI_SUCCESS;
+		}
+
+		/*
+		 * Otherwise we already received it from a guest and
+		 * it is destined for a local client on this host, or
+		 * it is from another local client on this host.  We
+		 * must be acting as a host to service it.
+		 */
+		if (!has_host_device)
+			return VMCI_ERROR_DEVICE_NOT_FOUND;
+
+		if (VMCI_INVALID_ID == src->context) {
+			/*
+			 * If it came from a guest then it must have a
+			 * valid context.  Otherwise we can use the
+			 * host context.
+			 */
+			if (from_guest)
+				return VMCI_ERROR_INVALID_ARGS;
+
+			src->context = VMCI_HOST_CONTEXT_ID;
+		}
+
+		/* Route to local client. */
+		*route = VMCI_ROUTE_AS_HOST;
+		return VMCI_SUCCESS;
+	}
+
+	/*
+	 * If we are acting as a host then this might be destined for
+	 * a guest.
+	 */
+	if (has_host_device) {
+		/* It will have a context if it is meant for a guest. */
+		if (vmci_ctx_exists(dst->context)) {
+			if (VMCI_INVALID_ID == src->context) {
+				/*
+				 * If it came from a guest then it
+				 * must have a valid context.
+				 * Otherwise we can use the host
+				 * context.
+				 */
+
+				if (from_guest)
+					return VMCI_ERROR_INVALID_ARGS;
+
+				src->context = VMCI_HOST_CONTEXT_ID;
+			} else if (VMCI_CONTEXT_IS_VM(src->context) &&
+				   src->context != dst->context) {
+				/*
+				 * VM to VM communication is not
+				 * allowed. Since we catch all
+				 * communication destined for the host
+				 * above, this must be destined for a
+				 * VM since there is a valid context.
+				 */
+
+				return VMCI_ERROR_DST_UNREACHABLE;
+			}
+
+			/* Pass it up to the guest. */
+			*route = VMCI_ROUTE_AS_HOST;
+			return VMCI_SUCCESS;
+		} else if (!has_guest_device) {
+			/*
+			 * The host is attempting to reach a CID
+			 * without an active context, and we can't
+			 * send it down, since we have no guest
+			 * device.
+			 */
+
+			return VMCI_ERROR_DST_UNREACHABLE;
+		}
+	}
+
+	/*
+	 * We must be a guest trying to send to another guest, which means
+	 * we need to send it down to the host. We do not filter out VM to
+	 * VM communication here, since we want to be able to use the guest
+	 * driver on older versions that do support VM to VM communication.
+	 */
+	if (!has_guest_device) {
+		/*
+		 * Ending up here means we have neither guest nor host
+		 * device.
+		 */
+		return VMCI_ERROR_DEVICE_NOT_FOUND;
+	}
+
+	/* If no source context then use the current context. */
+	if (VMCI_INVALID_ID == src->context)
+		src->context = vmci_get_context_id();
+
+	/*
+	 * Send it from local client down to the host, which will
+	 * route it to the other guest for us.
+	 */
+	*route = VMCI_ROUTE_AS_GUEST;
+	return VMCI_SUCCESS;
+}

drivers/misc/vmw_vmci/vmci_route.h

···
+/*
+ * VMware VMCI Driver
+ *
+ * Copyright (C) 2012 VMware, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation version 2 and no later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#ifndef _VMCI_ROUTE_H_
+#define _VMCI_ROUTE_H_
+
+#include <linux/vmw_vmci_defs.h>
+
+enum vmci_route {
+	VMCI_ROUTE_NONE,
+	VMCI_ROUTE_AS_HOST,
+	VMCI_ROUTE_AS_GUEST,
+};
+
+int vmci_route(struct vmci_handle *src, const struct vmci_handle *dst,
+	       bool from_guest, enum vmci_route *route);
+
+#endif /* _VMCI_ROUTE_H_ */