lib: northbound: improve xpath functionality

Allow user to leave keys off of a list entry node at the end of the xpath. This
will return all list entries. Previously there was no way to just get the list
entries. One had to leave off the last list entry node which would then return
all list nodes as well as all the siblings at the same level.

Signed-off-by: Christian Hopps <chopps@labn.net>

lib/frrstr.c

@@ -249,3 +249,24 @@ const char *frrstr_skip_over_char(const char *s, int skipc)
 	}
 	return NULL;
 }
+
+/*
+ * Advance backward in string until reaching the char `toc`
+ * if beginning of string is reached w/o finding char return NULL
+ *
+ * /foo/bar'baz/booz'/foo
+ */
+const char *frrstr_back_to_char(const char *s, int toc)
+{
+	const char *next = s;
+	const char *prev = NULL;
+
+	if (s[0] == 0)
+		return NULL;
+	if (!strpbrk(s, "'\"\\"))
+		return strrchr(s, toc);
+	while ((next = frrstr_skip_over_char(next, toc)))
+		prev = next - 1;
+	return prev;
+}
+

lib/frrstr.h

@@ -167,13 +167,19 @@ int all_digit(const char *str);
  */
 char *frrstr_hex(char *buff, size_t bufsiz, const uint8_t *str, size_t num);
 
-
 /*
  * Advance past a given char `skipc` in a string, while honoring quoting and
  * backslash escapes (i.e., ignore `skipc` which occur in quoted sections).
  */
 const char *frrstr_skip_over_char(const char *s, int skipc);
 
+/*
+ * Advance back from end to a given char `toc` in a string, while honoring
+ * quoting and backslash escapes. `toc` chars inside quote or escaped are
+ * ignored.
+ */
+const char *frrstr_back_to_char(const char *s, int toc);
+
 #ifdef __cplusplus
 }
 #endif

lib/northbound.c

@@ -2032,6 +2032,62 @@ static int nb_oper_data_iter_node(const struct lysc_node *snode,
 	return ret;
 }
 
+static int nb_xpath_dirname(char *xpath)
+{
+	int len = strlen(xpath);
+	bool abs = xpath[0] == '/';
+	char *slash;
+
+	/* "//" or "/" => NULL */
+	if (abs && (len == 1 || (len == 2 && xpath[1] == '/')))
+		return NB_ERR_NOT_FOUND;
+	slash = (char *)frrstr_back_to_char(xpath, '/');
+	/* "/foo/bar/" or "/foo/bar//" => "/foo " */
+	if (slash && slash == &xpath[len - 1]) {
+		xpath[--len] = 0;
+		slash = (char *)frrstr_back_to_char(xpath, '/');
+		if (slash && slash == &xpath[len - 1]) {
+			xpath[--len] = 0;
+			slash = (char *)frrstr_back_to_char(xpath, '/');
+		}
+	}
+	if (!slash)
+		return NB_ERR_NOT_FOUND;
+	*slash = 0;
+	return NB_OK;
+}
+
+static int nb_oper_data_xpath_to_tree(const char *xpath_in,
+				      struct lyd_node **dnode,
+				      bool is_top_node_list)
+{
+	/* Eventually this function will loop until it finds a concrete path */
+	char *xpath;
+	LY_ERR err;
+	int ret;
+
+	err = lyd_new_path2(NULL, ly_native_ctx, xpath_in, NULL, 0, 0,
+			    LYD_NEW_PATH_UPDATE, NULL, dnode);
+	if (err == LY_SUCCESS)
+		return NB_OK;
+	if (!is_top_node_list)
+		return NB_ERR_NOT_FOUND;
+
+	xpath = XSTRDUP(MTYPE_TMP, xpath_in);
+	ret = nb_xpath_dirname(xpath);
+	if (ret != NB_OK)
+		goto done;
+
+	err = lyd_new_path2(NULL, ly_native_ctx, xpath, NULL, 0, 0,
+			    LYD_NEW_PATH_UPDATE, NULL, dnode);
+	if (err != LY_SUCCESS)
+		ret = NB_ERR_NOT_FOUND;
+done:
+	XFREE(MTYPE_TMP, xpath);
+	return ret;
+}
+
+
 int nb_oper_data_iterate(const char *xpath, struct yang_translator *translator,
 			 uint32_t flags, nb_oper_data_cb cb, void *arg)
 {
@@ -2064,25 +2120,23 @@ int nb_oper_data_iterate(const char *xpath, struct yang_translator *translator,
 	 * all YANG lists (if any).
 	 */
 
-	LY_ERR err = lyd_new_path2(NULL, ly_native_ctx, xpath, NULL, 0, 0,
-				   LYD_NEW_PATH_UPDATE, NULL, &dnode);
-	if (err || !dnode) {
-		const char *errmsg =
-			err ? ly_errmsg(ly_native_ctx) : "node not found";
-		flog_warn(EC_LIB_LIBYANG, "%s: lyd_new_path() failed %s",
-			  __func__, errmsg);
-		return NB_ERR;
+	ret = nb_oper_data_xpath_to_tree(xpath, &dnode,
+					 nb_node->snode->nodetype == LYS_LIST);
+	if (ret) {
+		flog_warn(EC_LIB_LIBYANG,
+			  "%s: can't instantiate concrete path using xpath: %s",
+			  __func__, xpath);
+		return ret;
 	}
 
 	/*
 	 * Create a linked list to sort the data nodes starting from the root.
 	 */
 	list_dnodes = list_new();
-	for (dn = dnode; dn; dn = lyd_parent(dn)) {
-		if (dn->schema->nodetype != LYS_LIST || !lyd_child(dn))
-			continue;
+	for (dn = dnode; dn; dn = lyd_parent(dn))
+		if (dn->schema->nodetype == LYS_LIST)
 			listnode_add_head(list_dnodes, dn);
-	}
+
 	/*
 	 * Use the northbound callbacks to find list entry pointer corresponding
 	 * to the given XPath.
@@ -2104,6 +2158,10 @@ int nb_oper_data_iterate(const char *xpath, struct yang_translator *translator,
 		}
 		list_keys.num = n;
 		if (list_keys.num != yang_snode_num_keys(dn->schema)) {
+			flog_warn(
+				EC_LIB_NB_OPERATIONAL_DATA,
+				"%s: internal list entry '%s' missing required key values predicates in xpath: %s",
+				__func__, dn->schema->name, xpath);
 			list_delete(&list_dnodes);
 			yang_dnode_free(dnode);
 			return NB_ERR_NOT_FOUND;
@@ -2121,6 +2179,11 @@ int nb_oper_data_iterate(const char *xpath, struct yang_translator *translator,
 			return NB_ERR;
 		}
 
+		/* NOTE: To add support for multiple levels of unspecified keys
+		 * we need to loop here using the list entry's get_next to work
+		 * with each "existing in the data" list entry. It will be a bit
+		 * tricky b/c we are inside a loop here.
+		 */
 		list_entry =
 			nb_callback_lookup_entry(nn, list_entry, &list_keys);
 		if (list_entry == NULL) {
@@ -2130,8 +2193,11 @@ int nb_oper_data_iterate(const char *xpath, struct yang_translator *translator,
 		}
 	}
 
-	/* If a list entry was given, iterate over that list entry only. */
-	if (dnode->schema->nodetype == LYS_LIST && lyd_child(dnode))
+	/* If a list entry was given with keys as the last node in the path,
+	 * iterate over that list entry only.
+	 */
+	if (dnode->schema->nodetype == LYS_LIST && lyd_child(dnode)
+	    && dnode->schema == nb_node->snode)
 		ret = nb_oper_data_iter_children(
 			nb_node->snode, xpath, list_entry, &list_keys,
 			translator, true, flags, cb, arg);