[Libguestfs] [nbdkit PATCH v4 3/4] vddk: Delay loading VDDK until config_complete.

[Eric Blake]

From: "Richard W.M. Jones" <rjones at redhat.com>

We were previously dlopen-ing it in the load() method.  This is very
early and in particular means that the only possible way to configure
where we find the library is through environment variables and not
through config parameters.  Also it's not necessary as we don't call
any functions from the library (such as VixDiskLib_InitEx) until
config_complete.

This change is neutral refactoring as currently we _do_ configure the
location through an environment variable (LD_LIBRARY_PATH).
Message-Id: <20200213160449.732936-2-rjones at redhat.com>
---
 plugins/vddk/vddk.c | 100 ++++++++++++++++++++++----------------------
 1 file changed, 51 insertions(+), 49 deletions(-)

diff --git a/plugins/vddk/vddk.c b/plugins/vddk/vddk.c
index 5d3764d6..db61c1d8 100644
--- a/plugins/vddk/vddk.c
+++ b/plugins/vddk/vddk.c
@@ -143,54 +143,7 @@ error_function (const char *fs, va_list args)
   nbdkit_error ("%s", str);
 }

-/* Load and unload the plugin. */
-static void
-vddk_load (void)
-{
-  static const char *sonames[] = {
-    /* Prefer the newest library in case multiple exist. */
-    "libvixDiskLib.so.6",
-    "libvixDiskLib.so.5",
-  };
-  size_t i;
-  CLEANUP_FREE char *orig_error = NULL;
-
-  /* Load the library. */
-  for (i = 0; i < sizeof sonames / sizeof sonames[0]; ++i) {
-    dl = dlopen (sonames[i], RTLD_NOW);
-    if (dl != NULL)
-      break;
-    if (i == 0) {
-      orig_error = dlerror ();
-      if (orig_error)
-        orig_error = strdup (orig_error);
-    }
-  }
-  if (dl == NULL) {
-    nbdkit_error ("%s\n\n"
-                  "If '%s' is located on a non-standard path you may need to\n"
-                  "set $LD_LIBRARY_PATH or edit /etc/ld.so.conf.\n\n"
-                  "See the nbdkit-vddk-plugin(1) man page for details.",
-                  orig_error ? : "(unknown error)", sonames[0]);
-    exit (EXIT_FAILURE);
-  }
-
-  /* Load symbols. */
-#define STUB(fn,ret,args)                                         \
-  do {                                                            \
-    fn = dlsym (dl, #fn);                                         \
-    if (fn == NULL) {                                             \
-      nbdkit_error ("required VDDK symbol \"%s\" is missing: %s", \
-                    #fn, dlerror ());                             \
-      exit (EXIT_FAILURE);                                        \
-    }                                                             \
-  } while (0)
-#define OPTIONAL_STUB(fn,ret,args) fn = dlsym (dl, #fn)
-#include "vddk-stubs.h"
-#undef STUB
-#undef OPTIONAL_STUB
-}
-
+/* Unload the plugin. */
 static void
 vddk_unload (void)
 {
@@ -289,6 +242,54 @@ vddk_config (const char *key, const char *value)
   return 0;
 }

+/* Load the VDDK library. */
+static void
+load_library (void)
+{
+  static const char *sonames[] = {
+    /* Prefer the newest library in case multiple exist. */
+    "libvixDiskLib.so.6",
+    "libvixDiskLib.so.5",
+  };
+  size_t i;
+  CLEANUP_FREE char *orig_error = NULL;
+
+  /* Load the library. */
+  for (i = 0; i < sizeof sonames / sizeof sonames[0]; ++i) {
+    dl = dlopen (sonames[i], RTLD_NOW);
+    if (dl != NULL)
+      break;
+    if (i == 0) {
+      orig_error = dlerror ();
+      if (orig_error)
+        orig_error = strdup (orig_error);
+    }
+  }
+  if (dl == NULL) {
+    nbdkit_error ("%s\n\n"
+                  "If '%s' is located on a non-standard path you may need to\n"
+                  "set $LD_LIBRARY_PATH or edit /etc/ld.so.conf.\n\n"
+                  "See the nbdkit-vddk-plugin(1) man page for details.",
+                  orig_error ? : "(unknown error)", sonames[0]);
+    exit (EXIT_FAILURE);
+  }
+
+  /* Load symbols. */
+#define STUB(fn,ret,args)                                         \
+  do {                                                            \
+    fn = dlsym (dl, #fn);                                         \
+    if (fn == NULL) {                                             \
+      nbdkit_error ("required VDDK symbol \"%s\" is missing: %s", \
+                    #fn, dlerror ());                             \
+      exit (EXIT_FAILURE);                                        \
+    }                                                             \
+  } while (0)
+#define OPTIONAL_STUB(fn,ret,args) fn = dlsym (dl, #fn)
+#include "vddk-stubs.h"
+#undef STUB
+#undef OPTIONAL_STUB
+}
+
 static int
 vddk_config_complete (void)
 {
@@ -330,6 +331,8 @@ vddk_config_complete (void)
 #undef missing
   }

+  load_library ();
+
   /* Initialize VDDK library. */
   DEBUG_CALL ("VixDiskLib_InitEx",
               "%d, %d, &debug_fn, &error_fn, &error_fn, %s, %s",
@@ -831,7 +834,6 @@ static struct nbdkit_plugin plugin = {
   .name              = "vddk",
   .longname          = "VMware VDDK plugin",
   .version           = PACKAGE_VERSION,
-  .load              = vddk_load,
   .unload            = vddk_unload,
   .config            = vddk_config,
   .config_complete   = vddk_config_complete,
-- 
2.24.1