* Pushed tag to 4.0.1.PRE

* Restconf RFC 8040 increased feature compliance
  * Cache-Control: no-cache added in HTTP responses (RFC Section 5.5)
  * Restconf monitoring capabilities (RFC Section 9.1)
* Added support for Yang extensions
  * New plugin callback: ca_extension
  * Main backend example includes example code on how to implement a Yang extension in a plugin.
* JSON changes
  * Non-pretty-print output removed all extra spaces.
    * Example: `{"nacm-example:x": 42}` --> {"nacm-example:x":42}`
  * Empty JSON container changed from `null` to `{}`.
    * Empty list and leafs remain as `null`
* Removed unnecessary configure dependencies
  * libnsl, libcrypt, libm, if_vlan,...
* pseudo-plugin added, to enable callbacks also for main programs. Useful for extensions
* Yang Unique statements with multiple schema identifiers did not work on some platforms due to memory error.

lib/clixon/clixon_json.h

@@ -2,7 +2,7 @@
  *
   ***** BEGIN LICENSE BLOCK *****
  
-  Copyright (C) 2009-2019 Olof Hagsand and Benny Holmgren
+  Copyright (C) 2009-2019 Olof Hagsand
 
   This file is part of CLIXON.
 
@@ -32,6 +32,8 @@
   ***** END LICENSE BLOCK *****
 
  * JSON support functions.
+ * JSON syntax is according to:
+ * http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf
  */
 #ifndef _CLIXON_JSON_H
 #define _CLIXON_JSON_H

lib/clixon/clixon_plugin.h

@@ -106,6 +106,20 @@ typedef int (plgstart_t)(clicon_handle); /* Plugin start */
  */
 typedef int (plgexit_t)(clicon_handle);		       /* Plugin exit */
 
+/* For yang extension handling. 
+ * Called at parsing of yang module containing a statement of an extension.
+ * A plugin may identify the extension by its name, and perform actions
+ * on the yang statement, such as transforming the yang.
+ * A callback is made for every statement, which means that several calls per
+ * extension can be made.
+ * @param[in] h    Clixon handle
+ * @param[in] yext Yang node of extension 
+ * @param[in] ys   Yang node of (unknown) statement belonging to extension
+ * @retval     0   OK, all callbacks executed OK
+ * @retval    -1   Error in one callback
+ */
+typedef int (plgextension_t)(clicon_handle h, yang_stmt *yext, yang_stmt *ys);
+
 /*! Called by restconf to check credentials and return username
  */
 
@@ -168,6 +182,7 @@ struct clixon_plugin_api{
     plginit2_t       *ca_init;           /* Clixon plugin Init (implicit) */
     plgstart_t       *ca_start;          /* Plugin start */
     plgexit_t        *ca_exit;	         /* Plugin exit */
+    plgextension_t   *ca_extension;      /* Yang extension handler */
     union {
 	struct { /* cli-specific */
 	    cli_prompthook_t *ci_prompt;         /* Prompt hook */
@@ -189,7 +204,6 @@ struct clixon_plugin_api{
 	    trans_cb_t       *cb_trans_revert;   /* Transaction revert */
 	    trans_cb_t       *cb_trans_end;	 /* Transaction completed  */
     	    trans_cb_t       *cb_trans_abort;	 /* Transaction aborted */    
-
 	} cau_backend;
 
     } u;
@@ -245,12 +259,16 @@ clixon_plugin *clixon_plugin_find(clicon_handle h, char *name);
 
 int clixon_plugins_load(clicon_handle h, char *function, char *dir, char *regexp);
 
+int clixon_pseudo_plugin(clicon_handle h, char *name, clixon_plugin **cpp);
+
 int clixon_plugin_start(clicon_handle h);
 
 int clixon_plugin_exit(clicon_handle h);
 
 int clixon_plugin_auth(clicon_handle h, void *arg);
 
+int clixon_plugin_extension(clicon_handle h, yang_stmt *yext, yang_stmt *ys);
+
 /* rpc callback API */
 int rpc_callback_register(clicon_handle h, clicon_rpc_cb cb, void *arg, char *namespace, char *name);
 int rpc_callback_delete_all(clicon_handle h);

lib/clixon/clixon_yang.h

@@ -140,7 +140,6 @@ struct xml;
 
 typedef struct yang_stmt yang_stmt; /* Defined in clixon_yang_internal */
 
-
 typedef int (yang_applyfn_t)(yang_stmt *ys, void *arg);
 
 /*
@@ -157,6 +156,8 @@ int        yang_cvec_set(yang_stmt *ys, cvec *cvv);
 /* Other functions */
 yang_stmt *yspec_new(void);
 yang_stmt *ys_new(enum rfc_6020 keyw);
+yang_stmt *ys_prune(yang_stmt *yp, int i);
+
 int        ys_free(yang_stmt *ys);
 int        yspec_free(yang_stmt *yspec);
 int        ys_cp(yang_stmt *new, yang_stmt *old);