vddk: Work with VDDK libraries back to 5.1.1.

Enhance the configure test so it recognizes the optional fields
nfcHostPort and vimApiVer in VixDiskLibConnectParams.

Modify the code to make these fields optional.

To check if the optional fields are present, use --dump-plugin.  You
will see these lines if the corresponding fields (and command line
keys) are present, otherwise they will be missing:

vddk_has_nfchostport=1
vddk_has_vimapiver=1

configure.ac

@@ -424,7 +424,7 @@ AS_IF([test "$with_vddk" = "yes"],[
     VDDK_LIBS="-lvixDiskLib"
     # XXX Warning: stupid VMware API.
     VDDK_LIBDIR="$libdir/vmware-vix-disklib"
-    AC_MSG_NOTICE([VDDK plugin enabled])
+    AC_MSG_NOTICE([VDDK plugin enabled from $VDDK_LIBDIR])
     ],[
     AS_IF([test "$with_vddk" != "no"], [
         VDDK_CFLAGS="-I$with_vddk/include"
@@ -435,6 +435,49 @@ AS_IF([test "$with_vddk" = "yes"],[
         [AC_MSG_NOTICE([VDDK plugin disabled])
     ])
 ])
+
+dnl If the VDDK plugin was enabled, compile and link a test program to make
+dnl sure the library really works.
+AS_IF([test "x$VDDK_LIBS" != "x"],[
+    # Save CFLAGS etc while we do this test.
+    acx_nbdkit_save_CFLAGS="${CFLAGS}"
+    acx_nbdkit_save_LIBS="${LIBS}"
+    CFLAGS="$CFLAGS $VDDK_CFLAGS"
+    LIBS="$VDDK_LIBS $LIBS"
+
+    AC_MSG_CHECKING([if we can link to VDDK])
+    AC_LINK_IFELSE([
+        AC_LANG_SOURCE([[
+#include <stdio.h>
+#include <stdint.h>
+#include <vixDiskLib.h>
+
+int
+main ()
+{
+    VixDiskLib_Exit ();
+}
+]])
+    ],[
+        AC_MSG_RESULT([yes])
+    ],[
+        AC_MSG_RESULT([no])
+        AC_MSG_ERROR([could not link to VDDK, see ‘config.log’ for more information])
+    ])
+
+    dnl Check for optional fields in VixDiskLibConnectParams struct.
+    AC_CHECK_MEMBERS([VixDiskLibConnectParams.nfcHostPort, VixDiskLibConnectParams.vimApiVer],
+                    [], [], [[
+#include <stdio.h>
+#include <stdint.h>
+#include <vixDiskLib.h>
+]])
+
+    dnl Restore CFLAGS, etc.
+    CFLAGS="${acx_nbdkit_save_CFLAGS}"
+    LIBS="${acx_nbdkit_save_LIBS}"
+])
+
 AC_SUBST([VDDK_CFLAGS])
 AC_SUBST([VDDK_LIBS])
 AC_DEFINE_UNQUOTED([VDDK_LIBDIR],["$VDDK_LIBDIR"],[VDDK 'libDir'.])

plugins/vddk/nbdkit-vddk-plugin.pod

@@ -12,6 +12,7 @@ nbdkit-vddk-plugin - VMware VDDK plugin for nbdkit
              [cookie=COOKIE] [thumbprint=THUMBPRINT]
              [vimapiver=APIVER] [port=PORT] [nfchostport=PORT]
              [snapshot=MOREF] [transports=MODE:MODE:...]
+ nbdkit vddk --dump-plugin
 
 =head1 DESCRIPTION
 
@@ -77,6 +78,8 @@ compile time is used.
 Optional.  Port used to establish an NFC connection to ESXi.  Defaults
 to 902.
 
+(Only supported in VDDK ≥ 5.5.5 and ≥ 6.0.1)
+
 =item B<password=PASSWORD>
 
 Optional (required for remote connections).  Set the password to use
@@ -177,6 +180,8 @@ L<https://blogs.vmware.com/vsphere/2012/02/uniquely-identifying-virtual-machines
 Optional.  Specify the VIM API version.  If not given it defaults to
 the current version.
 
+(Only supported in VDDK ≥ 6.5.0)
+
 =back
 
 =head1 EXAMPLES
@@ -242,6 +247,37 @@ C<file> is the actual file you want to open, usually in the form
 C<"[datastore] vmname/vmname.vmdk">.  You can find this from the
 L<virsh(1)> as described in L</PARAMETERS> above.
 
+=head1 DUMP-PLUGIN OUTPUT
+
+To query more information about the plugin (and whether it is
+working), use:
+
+ nbdkit vddk --dump-plugin
+
+If the plugin is not present, not working or the library path is wrong
+you will get an error.
+
+If it works the output will include:
+
+=over 4
+
+=item C<vddk_default_libdir=...>
+
+The compiled-in library path.  Use C<libdir=PATHNAME> to override this
+at runtime.
+
+=item C<vddk_has_nfchostport=1>
+
+If this is printed then the C<nfchostport=PORT> parameter is supported
+by this build.
+
+=item C<vddk_has_vimapiver=1>
+
+If this is printed then the C<vimapiver=APIVER> parameter is supported
+by this build.
+
+=back
+
 =head1 DEBUGGING VDDK
 
 Debugging messages can be very helpful if you have problems connecting

plugins/vddk/vddk.c

@@ -171,10 +171,15 @@ vddk_config (const char *key, const char *value)
     libdir = value;
   }
   else if (strcmp (key, "nfchostport") == 0) {
+#if HAVE_VIXDISKLIBCONNECTPARAMS_NFCHOSTPORT
     if (sscanf (value, "%d", &nfc_host_port) != 1) {
       nbdkit_error ("cannot parse nfchostport: %s", value);
       return -1;
     }
+#else
+    nbdkit_error ("this version of VDDK is too old to support nfchostpost");
+    return -1;
+#endif
   }
   else if (strcmp (key, "password") == 0) {
     free (password);
@@ -203,7 +208,12 @@ vddk_config (const char *key, const char *value)
     username = value;
   }
   else if (strcmp (key, "vimapiver") == 0) {
+#if HAVE_VIXDISKLIBCONNECTPARAMS_VIMAPIVER
     vim_api_ver = value;
+#else
+    nbdkit_error ("this version of VDDK is too old to support vimapiver");
+    return -1;
+#endif
   }
   else if (strcmp (key, "vm") == 0) {
     vmx_spec = value;
@@ -266,6 +276,15 @@ static void
 vddk_dump_plugin (void)
 {
   printf ("vddk_default_libdir=%s\n", VDDK_LIBDIR);
+
+#if HAVE_VIXDISKLIBCONNECTPARAMS_NFCHOSTPORT
+  printf ("vddk_has_nfchostport=1\n");
+#endif
+
+#if HAVE_VIXDISKLIBCONNECTPARAMS_VIMAPIVER
+  printf ("vddk_has_vimapiver=1\n");
+#endif
+
   /* XXX We really need to print the version of the dynamically
    * linked library here, but VDDK does not provide it.
    */
@@ -315,8 +334,12 @@ vddk_open (int readonly)
     }
     params.thumbPrint = (char *) thumb_print;
     params.port = port;
+#if HAVE_VIXDISKLIBCONNECTPARAMS_NFCHOSTPORT
     params.nfcHostPort = nfc_host_port;
+#endif
+#if HAVE_VIXDISKLIBCONNECTPARAMS_VIMAPIVER
     params.vimApiVer = (char *) vim_api_ver;
+#endif
   }
 
   /* XXX Some documentation suggests we should call