dns-resolve: Allow unbound's config file to be set through an env var.

When an unbound context is created, check whether OVS_UNBOUND_CONF has been
set. If a valid config file is supplied then use it to configure the
context. The procedure returns if the config file is invalid. If no config
file is found then the default unbound config is used.

Signed-off-by: Ted Elhourani <ted.elhourani@nutanix.com>
Signed-off-by: 0-day Robot <robot@bytheb.org>

Documentation/intro/install/general.rst

@@ -97,7 +97,9 @@ need the following software:
   specifying OpenFlow and OVSDB remotes. If unbound library is already
   installed, then Open vSwitch will automatically build with support for it.
   The environment variable OVS_RESOLV_CONF can be used to specify DNS server
-  configuration file (the default file on Linux is /etc/resolv.conf).
+  configuration file (the default file on Linux is /etc/resolv.conf), and
+  environment variable OVS_UNBOUND_CONF can be used to specify the configuration
+  file for unbound.
 
 On Linux, you may choose to compile the kernel module that comes with the Open
 vSwitch distribution or to use the kernel module built into the Linux kernel

lib/dns-resolve.c

@@ -82,6 +82,18 @@ dns_resolve_init(bool is_daemon)
         return;
     }
 
+    const char *ub_conf_filename = getenv("OVS_UNBOUND_CONF");
+    if (ub_conf_filename != NULL) {
+        int retval = ub_ctx_config(ub_ctx__, ub_conf_filename);
+        if (retval != 0) {
+            VLOG_WARN_RL(&rl, "Failed to set config of libunbound context: %s",
+                         ub_strerror(retval));
+            ub_ctx_delete(ub_ctx__);
+            ub_ctx__ = NULL;
+            return;
+      }
+    }
+
     const char *filename = getenv("OVS_RESOLV_CONF");
     if (!filename) {
 #ifdef _WIN32