[PATCH] Add hook that allows modification of default settings.

[Jelmer Vernooij]

This is useful for reducing the amount of configuration necessary for
OpenChange.

Change-Id: Ic8bacdd8b4c92a2a4b97cfa1a50dc41365b78071
Signed-Off-By: Jelmer Vernooij <jelmer at samba.org>
---
 lib/param/loadparm.c | 35 ++++++++++++++++++++++++++++++++++-
 lib/param/param.h    | 15 +++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/lib/param/loadparm.c b/lib/param/loadparm.c
index bfa9c7b..0ab2aca 100644
--- a/lib/param/loadparm.c
+++ b/lib/param/loadparm.c
@@ -2337,6 +2337,25 @@ static int lpcfg_destructor(struct loadparm_context *lp_ctx)
 	return 0;
 }
 
+typedef bool (*lpcfg_defaults_hook) (struct loadparm_context *);
+
+struct defaults_hook_data {
+	const char *name;
+	lpcfg_defaults_hook hook;
+	struct defaults_hook_data *prev, *next;
+} *defaults_hooks = NULL;
+
+
+bool lpcfg_register_defaults_hook(const char *name, lpcfg_defaults_hook hook)
+{
+	struct defaults_hook_data *hook_data = talloc(talloc_autofree_context(),
+												  struct defaults_hook_data);
+	hook_data->name = talloc_strdup(hook_data, name);
+	hook_data->hook = hook;
+	DLIST_ADD(defaults_hooks, hook_data);
+	return false;
+}
+
 /**
  * Initialise the global parameter structure.
  *
@@ -2349,6 +2368,7 @@ struct loadparm_context *loadparm_init(TALLOC_CTX *mem_ctx)
 	struct loadparm_context *lp_ctx;
 	struct parmlist_entry *parm;
 	char *logfile;
+	struct defaults_hook_data *defaults_hook;
 
 	lp_ctx = talloc_zero(mem_ctx, struct loadparm_context);
 	if (lp_ctx == NULL)
@@ -2744,6 +2764,20 @@ struct loadparm_context *loadparm_init(TALLOC_CTX *mem_ctx)
 
 	lpcfg_do_global_parameter(lp_ctx, "printjob username", "%U");
 
+	/* Allow modules to adjust defaults */
+	for (defaults_hook = defaults_hooks; defaults_hook;
+		 defaults_hook = defaults_hook->next) {
+		bool ret;
+
+		ret = defaults_hook->hook(lp_ctx);
+		if (!ret) {
+			DEBUG(1, ("Defaults hook %s failed to run.",
+					  defaults_hook->name));
+			talloc_free(lp_ctx);
+			return NULL;
+		}
+	}
+
 	for (i = 0; parm_table[i].label; i++) {
 		if (!(lp_ctx->flags[i] & FLAG_CMDLINE)) {
 			lp_ctx->flags[i] |= FLAG_DEFAULT;
@@ -2762,7 +2796,6 @@ struct loadparm_context *loadparm_init(TALLOC_CTX *mem_ctx)
 		}
 	}
 
-
 	return lp_ctx;
 }
 
diff --git a/lib/param/param.h b/lib/param/param.h
index 2fb6d4b..9064033 100644
--- a/lib/param/param.h
+++ b/lib/param/param.h
@@ -37,6 +37,8 @@ struct param_section {
 struct param_context;
 struct smbsrv_connection;
 
+typedef bool (*lpcfg_defaults_hook) (struct loadparm_context *);
+
 #define Auto (2)
 
 #include "libds/common/roles.h"
@@ -212,6 +214,19 @@ const char *lpcfg_socket_options(struct loadparm_context *);
 struct dcerpc_server_info *lpcfg_dcerpc_server_info(TALLOC_CTX *mem_ctx, struct loadparm_context *lp_ctx);
 struct gensec_settings *lpcfg_gensec_settings(TALLOC_CTX *, struct loadparm_context *);
 
+/* Hooks to override defaults.
+ *
+ * Every time a loadparm context is initialized, the hooks are
+ * called on it, once Samba itself has set defaults.
+ *
+ * This allows modules to tweak defaults (before any smb.conf file or registry
+ * is loaded). Usually they would do this by calling lpcfg_do_global_parameter
+ * or lpcfg_do_service_parameter.
+ *
+ * A good use case for this is OpenChange, which by default enables its
+ * DCE/RPC services when it is installed.
+ * */
+bool lpcfg_register_defaults_hook(const char *name, lpcfg_defaults_hook hook);
 
 /* The following definitions come from param/generic.c  */
 
-- 
2.2.0.rc0.207.ga3a616c