clicon · dima1308 · Mar 2, 2026
diff --git a/apps/backend/backend_state.c b/apps/backend/backend_state.c
@@ -105,6 +105,7 @@ restconf_client_get_capabilities(clixon_handle h,
     cprintf(cb, "<capabilities>");
     cprintf(cb, "<capability>urn:ietf:params:restconf:capability:defaults:1.0?basic-mode=explicit</capability>");
     cprintf(cb, "<capability>urn:ietf:params:restconf:capability:depth:1.0</capability>");
+    cprintf(cb, "<capability>urn:ietf:params:restconf:capability:fields:1.0</capability>");
     cprintf(cb, "<capability>urn:ietf:params:restconf:capability:with-defaults:1.0</capability>");
     cprintf(cb, "</capabilities>");
     if (clixon_xml_parse_string(cbuf_get(cb), YB_PARENT, NULL, &xrstate, NULL) < 0)

diff --git a/apps/restconf/restconf_methods_get.c b/apps/restconf/restconf_methods_get.c
@@ -66,6 +66,79 @@
 /* Forward */
 static int api_data_pagination(clixon_handle h, void *req, char *api_path, int pi, cvec *qvec, int pretty, restconf_media media_out);
 
+/*! Filter top-level data nodes based on "fields" query parameter (RFC 8040 Sec 4.8.3)
+ *
+ * Simple implementation: only top-level module:node or module:* selection at data root.
+ * Removes children of xdata that do not match any entry in the semicolon-separated
+ * fields list.
+ * @param[in]  xdata       XML data root whose children are top-level data nodes
+ * @param[in]  fields_str  Value of the "fields" query parameter, e.g. "mod1:node1;mod2:node2"
+ * @retval     0           OK
+ * @retval    -1           Error
+ * @see RFC 8040 Sec 4.8.3
+ */
+static int
+restconf_fields_filter(cxobj *xdata,
+                       char  *fields_str)
+{
+    int        retval = -1;
+    char      *str = NULL;
+    char      *s;
+    char      *saveptr;
+    char      *colon;
+    cxobj     *x;
+    yang_stmt *ynode;
+    yang_stmt *ymod;
+    char      *modname;
+    char      *nodename;
+    int        i;
+    int        found;
+
+    for (i = xml_child_nr(xdata)-1; i >= 0; i--){
+        x = xml_child_i(xdata, i);
+        if (xml_type(x) != CX_ELMNT)
+            continue;
+        ynode = xml_spec(x);
+        ymod = (ynode != NULL) ? ys_module(ynode) : NULL;
+        modname = (ymod != NULL) ? yang_argument_get(ymod) : NULL;
+        nodename = xml_name(x);
+        found = 0;
+        if ((str = strdup(fields_str)) == NULL){
+            clixon_err(OE_UNIX, errno, "strdup");
+            goto done;
+        }
+        s = strtok_r(str, ";", &saveptr);
+        while (s != NULL){
+            colon = strchr(s, ':');
+            if (colon != NULL){
+                *colon = '\0';
+                if (modname != NULL &&
+                    strcmp(s, modname) == 0 &&
+                    strcmp(colon+1, nodename) == 0)
+                    found = 1;
+                *colon = ':';
+            }
+            else{
+                if (modname != NULL && strcmp(s, modname) == 0)
+                    found = 1;
+            }
+            if (found)
+                break;
+            s = strtok_r(NULL, ";", &saveptr);
+        }
+        free(str);
+        str = NULL;
+        if (!found)
+            if (xml_purge(x) < 0)
+                goto done;
+    }
+    retval = 0;
+ done:
+    if (str)
+        free(str);
+    return retval;
+}
+
 /*! Generic GET (both HEAD and GET)
  *
  * According to restconf
@@ -125,6 +198,7 @@ api_data_get2(clixon_handle  h,
     cxobj     *xtop = NULL;
     yang_stmt *y = NULL;
     char      *defaults = NULL;
+    char      *fields_str = NULL;
     cvec      *nscd = NULL;
     int        ret;
 
@@ -207,6 +281,11 @@ api_data_get2(clixon_handle  h,
         clixon_debug(CLIXON_DBG_RESTCONF, "with_defaults=%s", attr);
         defaults = attr;
     }
+    /* Check for fields attribute: simple root-level module:node filter, RFC 8040 Sec 4.8.3 */
+    if ((attr = cvec_find_str(qvec, "fields")) != NULL){
+        clixon_debug(CLIXON_DBG_RESTCONF, "fields=%s", attr);
+        fields_str = attr;
+    }
 
     clixon_debug(CLIXON_DBG_RESTCONF, "path:%s", xpath);
     if ((ret = clicon_rpc_get(h, xpath, nsc, content, depth, defaults, &xret)) < 0){
@@ -235,6 +314,11 @@ api_data_get2(clixon_handle  h,
         goto done;
     }
     if (xpath==NULL || strcmp(xpath,"/")==0){ /* Special case: data root */
+        /* Apply fields filter if requested */
+        if (fields_str != NULL){
+            if (restconf_fields_filter(xret, fields_str) < 0)
+                goto done;
+        }
         switch (media_out){
         case YANG_DATA_XML:
             if (clixon_xml2cbuf(cbx, xret, 0, pretty, NULL, -1, 0) < 0) /* Dont print top object?  */

diff --git a/test/test_restconf_jukebox.sh b/test/test_restconf_jukebox.sh
@@ -189,13 +189,30 @@ expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' $RCP
 
 # Maybe this is not correct w [null,null]but I have no good examples
 new 'B.3.2.  "depth" Parameter depth=3'
-expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' $RCPROTO://localhost/restconf/data/example-jukebox:jukebox?depth=3)" 0 "HTTP/$HVER 200" '{"example-jukebox:jukebox":{"artist":\[null,null\]}}}
-'
+expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' $RCPROTO://localhost/restconf/data/example-jukebox:jukebox?depth=3)" 0 "HTTP/$HVER 200" '{"example-jukebox:jukebox":{"artist":\[null,null\]}}}
+
+'
 
 new "restconf DELETE whole datastore"
 expectpart "$(curl $CURLOPTS -X DELETE $RCPROTO://localhost/restconf/data)" 0 "HTTP/$HVER 204"
 
-#new 'B.3.3.  "fields" Parameter'
+new 'B.3.3.  "fields" Parameter: preamble (create system and jukebox data)'
+expectpart "$(curl $CURLOPTS -X PATCH -H 'Content-Type: application/yang-data+xml' $RCPROTO://localhost/restconf/data -d '<data xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf"><system xmlns="http://example.com/ns/example-system"><enable-jukebox-streaming>true</enable-jukebox-streaming></system><jukebox xmlns="http://example.com/ns/example-jukebox"><library><artist><name>Fields Artist</name></artist></library></jukebox></data>')" 0 "HTTP/$HVER 204"
+
+new 'B.3.3.  "fields" Parameter: system only'
+expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' $RCPROTO://localhost/restconf/data?fields=example-system:system)" 0 "HTTP/$HVER 200" \
+    '"example-system:system"' --not-- '"example-jukebox:jukebox"'
+
+new 'B.3.3.  "fields" Parameter: jukebox only'
+expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' $RCPROTO://localhost/restconf/data?fields=example-jukebox:jukebox)" 0 "HTTP/$HVER 200" \
+    '"example-jukebox:jukebox"' --not-- '"example-system:system"'
+
+new 'B.3.3.  "fields" Parameter: two modules'
+expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' "$RCPROTO://localhost/restconf/data?fields=example-system:system%3Bexample-jukebox:jukebox")" 0 "HTTP/$HVER 200" \
+    '"example-system:system"' '"example-jukebox:jukebox"'
+
+new "restconf DELETE whole datastore (after fields test)"
+expectpart "$(curl $CURLOPTS -X DELETE $RCPROTO://localhost/restconf/data)" 0 "HTTP/$HVER 204"
 
 new 'B.3.4.  "insert" Parameter'
 JSON="{\"example-jukebox:song\":[{\"index\":1,\"id\":\"/example-jukebox:jukebox/library/artist[name='Foo Fighters']/album[name='Wasting Light']/song[name='Rope']\"}]}"
@@ -251,7 +268,6 @@ new 'B.3.5.  "insert/point" leaf-list check order (2,4,3,1)'
 expectpart "$(curl $CURLOPTS -X GET $RCPROTO://localhost/restconf/data/example-jukebox:extra -H 'Accept: application/yang-data+xml')" 0 "HTTP/$HVER 200" '<extra xmlns="http://example.com/ns/example-jukebox">2</extra><extra xmlns="http://example.com/ns/example-jukebox">4</extra><extra xmlns="http://example.com/ns/example-jukebox">3</extra><extra xmlns="http://example.com/ns/example-jukebox">1</extra>'
 
 #new "B.2.2.  Detect Datastore Resource Entity-Tag Change" # XXX done except entity-changed
-#new 'B.3.3.  "fields" Parameter'
 #new 'B.3.6.  "filter" Parameter'
 #new 'B.3.7.  "start-time" Parameter'
 #new 'B.3.8.  "stop-time" Parameter'

diff --git a/test/test_yang_with_defaults.sh b/test/test_yang_with_defaults.sh
@@ -509,14 +509,14 @@ expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' $RCP
 0 \
 "HTTP/$HVER 200" "Content-Type: application/yang-data+json" \
 'Cache-Control: no-cache' \
-'{"ietf-restconf-monitoring:capabilities":{"capability":\["urn:ietf:params:restconf:capability:defaults:1.0?basic-mode=explicit","urn:ietf:params:restconf:capability:depth:1.0","urn:ietf:params:restconf:capability:with-defaults:1.0"\]}}'
+'{"ietf-restconf-monitoring:capabilities":{"capability":\["urn:ietf:params:restconf:capability:defaults:1.0?basic-mode=explicit","urn:ietf:params:restconf:capability:depth:1.0","urn:ietf:params:restconf:capability:fields:1.0","urn:ietf:params:restconf:capability:with-defaults:1.0"\]}}'
 
 new "rfc8040 B.1.3.  Retrieve the Server Capability Information xml"
 expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+xml' $RCPROTO://localhost/restconf/data/ietf-restconf-monitoring:restconf-state/capabilities)" \
 0 \
 "HTTP/$HVER 200" "Content-Type: application/yang-data+xml" \
 'Cache-Control: no-cache' \
-'<capabilities xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring"><capability>urn:ietf:params:restconf:capability:defaults:1.0?basic-mode=explicit</capability><capability>urn:ietf:params:restconf:capability:depth:1.0</capability><capability>urn:ietf:params:restconf:capability:with-defaults:1.0</capability></capabilities>'
+'<capabilities xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring"><capability>urn:ietf:params:restconf:capability:defaults:1.0?basic-mode=explicit</capability><capability>urn:ietf:params:restconf:capability:depth:1.0</capability><capability>urn:ietf:params:restconf:capability:fields:1.0</capability><capability>urn:ietf:params:restconf:capability:with-defaults:1.0</capability></capabilities>'
 
 new "rfc8040 B.3.9. RESTCONF with-defaults parameter = report-all json"
 expectpart "$(curl $CURLOPTS -X GET -H 'Accept: application/yang-data+json' $RCPROTO://localhost/restconf/data/example:interfaces/interface=eth1?with-defaults=report-all)" \