storage: Fix formatting and parsing of qemu type 'UnixSocketAddress'

The documentation for the JSON/qapi type 'UnixSocketAddress' states that
the unix socket path field is named 'path'. Unfortunately qemu uses
'socket' in case of the gluster driver (despite documented otherwise).

Add logic which will format the correct fields while keeping support of
the old spelling.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1544325Signed-off-by: NPeter Krempa <pkrempa@redhat.com>

src/qemu/qemu_block.c

@@ -467,11 +467,14 @@ qemuBlockStorageSourceGetURI(virStorageSourcePtr src)
 /**
  * qemuBlockStorageSourceBuildJSONSocketAddress
  * @host: the virStorageNetHostDefPtr definition to build
- * @legacy: use 'tcp' instead of 'inet' for compatibility reasons
+ * @legacy: use old field names/values
  *
  * Formats @hosts into a json object conforming to the 'SocketAddress' type
  * in qemu.
  *
+ * For compatibility with old approach used in the gluster driver of old qemus
+ * use the old spelling for TCP transport and, the path field of the unix socket.
+ *
  * Returns a virJSONValuePtr for a single server.
  */
 static virJSONValuePtr
@@ -481,6 +484,7 @@ qemuBlockStorageSourceBuildJSONSocketAddress(virStorageNetHostDefPtr host,
     virJSONValuePtr server = NULL;
     virJSONValuePtr ret = NULL;
     const char *transport;
+    const char *field;
     char *port = NULL;
 
     switch ((virStorageNetHostTransport) host->transport) {
@@ -502,9 +506,14 @@ qemuBlockStorageSourceBuildJSONSocketAddress(virStorageNetHostDefPtr host,
         break;
 
     case VIR_STORAGE_NET_HOST_TRANS_UNIX:
+        if (legacy)
+            field = "s:socket";
+        else
+            field = "s:path";
+
         if (virJSONValueObjectCreate(&server,
                                      "s:type", "unix",
-                                     "s:socket", host->socket,
+                                     field, host->socket,
                                      NULL) < 0)
             goto cleanup;
         break;

src/util/virstoragefile.c

@@ -2893,7 +2893,13 @@ virStorageSourceParseBackingJSONSocketAddress(virStorageNetHostDefPtr host,
     } else if (STREQ(type, "unix")) {
         host->transport = VIR_STORAGE_NET_HOST_TRANS_UNIX;
 
-        if (!(socket = virJSONValueObjectGetString(json, "socket"))) {
+        socket = virJSONValueObjectGetString(json, "path");
+
+        /* check for old spelling for gluster protocol */
+        if (!socket)
+            socket = virJSONValueObjectGetString(json, "socket");
+
+        if (!socket) {
             virReportError(VIR_ERR_INVALID_ARG, "%s",
                            _("missing socket path for udp backing server in "
                              "JSON backing volume definition"));