builder: Upload /etc/resolv.conf from the host when the network is enabled.

When the user has enabled the network (not the default) we upload
/etc/resolv.conf from the host to the appliance /etc/resolv.conf
so that programs in the appliance can contact nameservers.

Commit 9521422ce6 previously changed the
behaviour to copy /etc/resolv.conf into the sysroot when running
commands.

daemon/debug.c

@@ -751,6 +751,14 @@ do_debug_upload (const char *filename, int mode)
   return 0;
 }
 
+/* This function is identical to debug_upload. */
+/* Has one FileIn parameter. */
+int
+do_internal_upload (const char *filename, int mode)
+{
+  return do_debug_upload (filename, mode);
+}
+
 /* Internal function used only when testing
  * https://bugzilla.redhat.com/show_bug.cgi?id=914931
  */

generator/actions.ml

@@ -11607,6 +11607,16 @@ The label (name of the last element) of the Augeas path expression
 C<augpath> is returned.  C<augpath> must match exactly one node, else
 this function returns an error." };
 
+  { defaults with
+    name = "internal_upload";
+    style = RErr, [FileIn "filename"; String "tmpname"; Int "mode"], [];
+    proc_nr = Some 413;
+    visibility = VInternal;
+    cancellable = true;
+    shortdesc = "upload a file to the appliance (internal use only)";
+    longdesc = "\
+This function is used internally when setting up the appliance." };
+
 ]
 
 (* Non-API meta-commands available only in guestfish.

src/MAX_PROC_NR

@@ -1 +1 @@
-412
+413

src/launch.c

@@ -83,7 +83,17 @@ guestfs__launch (guestfs_h *g)
   }
 
   /* Launch the appliance. */
-  return g->backend_ops->launch (g, g->backend_data, g->backend_arg);
+  if (g->backend_ops->launch (g, g->backend_data, g->backend_arg) == -1)
+    return -1;
+
+  /* If network is enabled, upload /etc/resolv.conf from the host so
+   * the guest will know how to reach the nameservers.
+   */
+  if (g->enable_network && access ("/etc/resolv.conf", F_OK) == 0) {
+    guestfs_internal_upload (g, "/etc/resolv.conf", "/etc/resolv.conf", 0644);
+  }
+
+  return 0;
 }
 
 /* launch (of the appliance) generates approximate progress