tapback: Add -l/--libxl compatibility mode

libxl and xapi/xenopsd have different ordering requirements, and the
libxl required changes are not readily compatible with xapi.

Add a flag to allow running in libxl compatibility mode to bodge around
the issue.  The flag has to be passed from the parent tapback process
into the per-domain ones to ensure it is respected.

Some nearby hard tabs are converted to spaces.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>

tapback/backend.c

@@ -1197,7 +1197,7 @@ tapback_backend_handle_backend_watch(backend_t *backend,
                  * FIXME Shall we watch the child process?
                  */
             } else { /* child */
-                char *args[7];
+                char *args[8];
                 int i = 0;
 
                 args[i++] = (char*)tapback_name;
@@ -1211,8 +1211,10 @@ tapback_backend_handle_backend_watch(backend_t *backend,
                 }
                 if (log_level == LOG_DEBUG)
                     args[i++] = "-v";
-				if (!backend->barrier)
-					args[i++] = "-b";
+                if (!backend->barrier)
+                    args[i++] = "-b";
+                if (libxl_mode())
+                    args[i++] = "--libxl";
                 args[i] = NULL;
                 /*
                  * TODO we're hard-coding the name of the binary, better let

tapback/tapback.c

@@ -58,6 +58,7 @@
 const char tapback_name[] = "tapback";
 unsigned log_level;
 int tapdev_major;
+static bool opt_libxl_mode;
 
 struct list_head backends = LIST_HEAD_INIT(backends);
 
@@ -77,6 +78,12 @@ char *xenbus_strstate(const XenbusState xbs)
     return str[xbs];
 }
 
+bool
+libxl_mode(void)
+{
+    return opt_libxl_mode;
+}
+
 /**
  * Read changes that occurred on the "backend/<backend name>" XenStore path
  * or one of the front-end paths and act accordingly.
@@ -513,7 +520,8 @@ usage(FILE * const stream, const char * const prog)
 			"\t[-h|--help]\n"
             "\t[-v|--verbose]\n"
 			"\t[-b]--nobarrier]\n"
-            "\t[-n|--name]\n", prog);
+            "\t[-n|--name]\n"
+            "\t[-l|--libxl]\n", prog);
 }
 
 extern char *optarg;
@@ -612,8 +620,8 @@ int main(int argc, char **argv)
             {"name", 0, NULL, 'n'},
             {"pidfile", 0, NULL, 'p'},
             {"domain", 0, NULL, 'x'},
-			{"nobarrier", 0, NULL, 'b'},
-
+            {"nobarrier", 0, NULL, 'b'},
+            {"libxl", 0, NULL, 'l'},
         };
         int c;
 
@@ -628,6 +636,9 @@ int main(int argc, char **argv)
         case 'd':
             opt_debug = true;
             break;
+        case 'l':
+            opt_libxl_mode = true;
+            break;
         case 'v':
             opt_verbose = true;
             break;

tapback/tapback.h

@@ -524,4 +524,14 @@ tapback_backend_destroy(backend_t *backend);
 
 bool verbose(void);
 
+/**
+ * Indicates when tapback is running in libxl compatibility mode.  libxl needs
+ * backends to transition to InitWait earlier than xapi/xenopds.
+ *
+ * Returns true if tapback is running in libxl compatibility mode and false
+ * otherwise.
+ */
+bool
+libxl_mode(void);
+
 #endif /* __TAPBACK_H__ */