virinitctl: Expose fifo paths and allow caller to chose one

So far the virInitctlSetRunLevel() is fully automatic. It finds
the correct fifo to use to talk to the init and it will set the
desired runlevel. Well, callers (so far there is just one) will
need to inspect the fifo a bit just before the runlevel is set.
Therefore, expose the internal list of fifos and also allow
caller to explicitly use one.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>

src/libvirt_private.syms

@@ -2056,6 +2056,7 @@ virIdentitySetX509DName;
 
 
 # util/virinitctl.h
+virInitctlFifos;
 virInitctlSetRunLevel;
 
 

src/lxc/lxc_driver.c

@@ -3277,7 +3277,7 @@ lxcDomainInitctlCallback(pid_t pid ATTRIBUTE_UNUSED,
                          void *opaque)
 {
     int *command = opaque;
-    return virInitctlSetRunLevel(*command);
+    return virInitctlSetRunLevel(NULL, *command);
 }
 
 

src/util/virinitctl.c

@@ -101,7 +101,21 @@ struct virInitctlRequest {
   verify(sizeof(struct virInitctlRequest) == 384);
 # endif
 
-/*
+
+/* List of fifos that inits are known to listen on */
+const char *virInitctlFifos[] = {
+  "/run/initctl",
+  "/dev/initctl",
+  "/etc/.initctl",
+  NULL
+};
+
+
+/**
+ * virInitctlSetRunLevel:
+ * @fifo: the path to fifo that init listens on (can be NULL for autodetection)
+ * @level: the desired runlevel
+ *
  * Send a message to init to change the runlevel. This function is
  * asynchronous-signal-safe (thus safe to use after fork of a
  * multithreaded parent) - which is good, because it should only be
@@ -110,18 +124,14 @@ struct virInitctlRequest {
  * Returns 1 on success, 0 if initctl does not exist, -1 on error
  */
 int
-virInitctlSetRunLevel(virInitctlRunLevel level)
+virInitctlSetRunLevel(const char *fifo,
+                      virInitctlRunLevel level)
 {
     struct virInitctlRequest req;
     int fd = -1;
     int ret = -1;
-    const char *initctl_fifo = NULL;
+    const int open_flags = O_WRONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY;
     size_t i = 0;
-    const char *initctl_fifos[] = {
-        "/run/initctl",
-        "/dev/initctl",
-        "/etc/.initctl",
-    };
 
     memset(&req, 0, sizeof(req));
 
@@ -131,31 +141,39 @@ virInitctlSetRunLevel(virInitctlRunLevel level)
     /* Yes it is an 'int' field, but wants a numeric character. Go figure */
     req.runlevel = '0' + level;
 
-    for (i = 0; i < ARRAY_CARDINALITY(initctl_fifos); i++) {
-        initctl_fifo = initctl_fifos[i];
-
-        if ((fd = open(initctl_fifo,
-                       O_WRONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY)) >= 0)
-            break;
-
-        if (errno != ENOENT) {
+    if (fifo) {
+        if ((fd = open(fifo, open_flags)) < 0) {
             virReportSystemError(errno,
                                  _("Cannot open init control %s"),
-                                 initctl_fifo);
+                                 fifo);
             goto cleanup;
         }
-    }
+    } else {
+        for (i = 0; virInitctlFifos[i]; i++) {
+            fifo = virInitctlFifos[i];
 
-    /* Ensure we found a valid initctl fifo */
-    if (fd < 0) {
-        ret = 0;
-        goto cleanup;
+            if ((fd = open(fifo, open_flags)) >= 0)
+                break;
+
+            if (errno != ENOENT) {
+                virReportSystemError(errno,
+                                     _("Cannot open init control %s"),
+                                     fifo);
+                goto cleanup;
+            }
+        }
+
+        /* Ensure we found a valid initctl fifo */
+        if (fd < 0) {
+            ret = 0;
+            goto cleanup;
+        }
     }
 
     if (safewrite(fd, &req, sizeof(req)) != sizeof(req)) {
         virReportSystemError(errno,
                              _("Failed to send request to init control %s"),
-                             initctl_fifo);
+                             fifo);
         goto cleanup;
     }
 
@@ -166,7 +184,8 @@ virInitctlSetRunLevel(virInitctlRunLevel level)
     return ret;
 }
 #else
-int virInitctlSetRunLevel(virInitctlRunLevel level ATTRIBUTE_UNUSED)
+int virInitctlSetRunLevel(const char *fifo ATTRIBUTE_UNUSED,
+                          virInitctlRunLevel level ATTRIBUTE_UNUSED)
 {
     virReportUnsupportedError();
     return -1;

src/util/virinitctl.h

@@ -33,6 +33,10 @@ typedef enum {
     VIR_INITCTL_RUNLEVEL_LAST
 } virInitctlRunLevel;
 
-int virInitctlSetRunLevel(virInitctlRunLevel level);
+
+extern const char *virInitctlFifos[];
+
+int virInitctlSetRunLevel(const char *fifo,
+                          virInitctlRunLevel level);
 
 #endif /* LIBVIRT_VIRINITCTL_H */