Avoid virGetVersion failure on specific driver support configurations

virGetVersion itself doesn't take a virConnectPtr, but in order to obtain
the hypervisor version against which libvirt was compiled it is used in
combination with virConnectGetType like this:

hvType = virConnectGetType(conn)
virGetVersion(&libVer, hvType, &typeVer)

When virConnectGetType is called on a remote connection then the remote
driver returns the type of the underlying driver on the server side, for
example QEMU. Then virGetVersion compares hvType to a set of strings that
depend on configure options and returns LIBVIR_VERSION_NUMBER in most
cases. Now this fails in case libvirt on the client side is just compiled
with the remote driver enabled only and the server side has the actual
driver such as the QEMU driver. It just happens to work when the actual
driver is enabled on client and server side. But that's not always true.
I noticed this on FreeBSD:

freebsd# virsh -c qemu+tcp://192.168.178.22/system version
Compiled against library: libvir 0.9.2
error: failed to get the library version
error: this function is not supported by the connection driver: virGetVersion

This is not FreeBSD specific, happens on Windows as well due to the
similar driver support configuration. The problem is that virConnectGetType
returns QEMU, but virGetVersion on the client side only accepts Remote
as hvType due to all other drivers being disabled on the client side.

Daniel P. Berrange suggested to get rid of all the conditional code in
virGetVersion, ignoring the hvType and always setting typeVer to
LIBVIR_VERSION_NUMBER. virConnectGetVersion is supposed to be used to
obtain the hypervisor version.

src/libvirt.c

@@ -894,21 +894,25 @@ int virStateActive(void) {
 /**
  * virGetVersion:
  * @libVer: return value for the library version (OUT)
- * @type: the type of connection/driver looked at, if @typeVer is not NULL
- * @typeVer: optional return value for the version of the hypervisor (OUT)
- *
- * Provides information on up to two versions: @libVer is the version of the
- * library and will always be set unless an error occurs, in which case an
- * error code will be returned. If @typeVer is not NULL it will be set to the
- * version of the hypervisor @type against which the library was compiled.
- * If @type is NULL, "Xen" is assumed, if @type is unknown or not
- * available, an error code will be returned and @typeVer will be 0.
+ * @type: ignored; pass NULL
+ * @typeVer: pass NULL; for historical purposes duplicates @libVer if
+ * non-NULL
+ *
+ * Provides version information. @libVer is the version of the
+ * library and will always be set unless an error occurs, in which case
+ * an error code will be returned. @typeVer exists for historical
+ * compatibility; if it is not NULL it will duplicate @libVer (it was
+ * originally intended to return hypervisor information based on @type,
+ * but due to the design of remote clients this is not reliable). To
+ * get the version of the running hypervisor use the virConnectGetVersion
+ * function instead. To get the libvirt library version used by a
+ * connection use the virConnectGetLibVersion instead.
  *
  * Returns -1 in case of failure, 0 otherwise, and values for @libVer and
  *       @typeVer have the format major * 1,000,000 + minor * 1,000 + release.
  */
 int
-virGetVersion(unsigned long *libVer, const char *type,
+virGetVersion(unsigned long *libVer, const char *type ATTRIBUTE_UNUSED,
               unsigned long *typeVer)
 {
     VIR_DEBUG("libVir=%p, type=%s, typeVer=%p", libVer, type, typeVer);
@@ -921,78 +925,9 @@ virGetVersion(unsigned long *libVer, const char *type,
         goto error;
     *libVer = LIBVIR_VERSION_NUMBER;
 
-    if (typeVer != NULL) {
-        if (type == NULL)
-            type = "Xen";
-
-/* FIXME: Add _proper_ type version handling for loadable driver modules... */
-#ifdef WITH_DRIVER_MODULES
+    if (typeVer != NULL)
         *typeVer = LIBVIR_VERSION_NUMBER;
-#else
-        *typeVer = 0;
 
-# if WITH_XEN
-        if (STRCASEEQ(type, "Xen"))
-            *typeVer = xenUnifiedVersion();
-# endif
-# if WITH_TEST
-        if (STRCASEEQ(type, "Test"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_QEMU
-        if (STRCASEEQ(type, "QEMU"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_LXC
-        if (STRCASEEQ(type, "LXC"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_LIBXL
-        if (STRCASEEQ(type, "xenlight"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_PHYP
-        if (STRCASEEQ(type, "phyp"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_OPENVZ
-        if (STRCASEEQ(type, "OpenVZ"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_VMWARE
-        if (STRCASEEQ(type, "VMware"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_VBOX
-        if (STRCASEEQ(type, "VBox"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_UML
-        if (STRCASEEQ(type, "UML"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_ONE
-        if (STRCASEEQ(type, "ONE"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_ESX
-        if (STRCASEEQ(type, "ESX"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_XENAPI
-        if (STRCASEEQ(type, "XenAPI"))
-            *typeVer = LIBVIR_VERSION_NUMBER;
-# endif
-# if WITH_REMOTE
-        if (STRCASEEQ(type, "Remote"))
-            *typeVer = remoteVersion();
-# endif
-        if (*typeVer == 0) {
-            virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
-            goto error;
-        }
-#endif /* WITH_DRIVER_MODULES */
-    }
     return 0;
 
 error: