lib: mgmtd: implement full XPath 1.0 functionality

Allow user to specify full YANG compatible XPath 1.0 functionality. This allows
for trimming results of generic queries using functions and other non-key
predicates from XPath 1.0

Signed-off-by: Christian Hopps <[email protected]>

lib/mgmt_msg.c

@@ -207,7 +207,7 @@ bool mgmt_msg_procbufs(struct mgmt_msg_state *ms,
 }
 
 /**
- * Write data from a onto the socket, using streams that have been queued for
+ * Write data onto the socket, using streams that have been queued for	       
  * sending by mgmt_msg_send_msg. This function should be reschedulable.
  *
  * Args:

lib/northbound.c

@@ -6,6 +6,7 @@
 
 #include <zebra.h>
 
+#include "darr.h"
 #include "libfrr.h"
 #include "log.h"
 #include "lib_errors.h"
@@ -174,6 +175,26 @@ struct nb_node *nb_node_find(const char *path)
 	return snode->priv;
 }
 
+struct nb_node **nb_nodes_find(const char *xpath)
+{
+	struct lysc_node **snodes = NULL;
+	struct nb_node **nb_nodes = NULL;
+	bool simple;
+	LY_ERR err;
+	uint i;
+
+	err = yang_resolve_snode_xpath(ly_native_ctx, xpath, &snodes, &simple);
+	if (err)
+		return NULL;
+
+	darr_ensure_i(nb_nodes, darr_lasti(snodes));
+	darr_foreach_i (snodes, i)
+		nb_nodes[i] = snodes[i]->priv;
+	darr_free(snodes);
+	return nb_nodes;
+}
+
+
 void nb_node_set_dependency_cbs(const char *dependency_xpath,
 				const char *dependant_xpath,
 				struct nb_dependency_callbacks *cbs)

lib/northbound.h

@@ -813,6 +813,14 @@ void nb_nodes_delete(void);
  */
 extern struct nb_node *nb_node_find(const char *xpath);
 
+/**
+ * nb_nodes_find() - find the NB nodes corresponding to complex xpath.
+ * @xpath: XPath to search for (with or without predicates).
+ *
+ * Return: a dynamic array (darr) of `struct nb_node *`s.
+ */
+extern struct nb_node **nb_nodes_find(const char *xpath);
+
 extern void nb_node_set_dependency_cbs(const char *dependency_xpath,
 				       const char *dependant_xpath,
 				       struct nb_dependency_callbacks *cbs);

lib/northbound_oper.c

@@ -1139,6 +1139,8 @@ static enum nb_error __walk(struct nb_op_yield_state *ys, bool is_resume)
 					/* predicate resolved to specific node */
 					is_specific_node = true;
 				else {
+					/* Should we should cache this result? */
+					/* XXX Change this to a debug, it's expected with complex xpaths */
 					flog_warn(EC_LIB_NB_OPERATIONAL_DATA,
 						  "%s: unable to create node for specific query string: %s",
 						  __func__,
@@ -1559,6 +1561,7 @@ static enum nb_error nb_op_yield(struct nb_op_yield_state *ys)
 static enum nb_error nb_op_ys_init_schema_path(struct nb_op_yield_state *ys,
 					       struct nb_node **last)
 {
+	struct nb_node **nb_nodes = NULL;
 	const struct lysc_node *sn;
 	struct nb_node *nblast;
 	char *s, *s2;
@@ -1576,6 +1579,11 @@ static enum nb_error nb_op_ys_init_schema_path(struct nb_op_yield_state *ys,
 	 * string over each schema trunk in the set.
 	 */
 	nblast = nb_node_find(ys->xpath);
+	if (!nblast) {
+		nb_nodes = nb_nodes_find(ys->xpath);
+		nblast = darr_len(nb_nodes) ? nb_nodes[0] : NULL;
+		darr_free(nb_nodes);
+	}
 	if (!nblast) {
 		flog_warn(EC_LIB_YANG_UNKNOWN_DATA_PATH,
 			  "%s: unknown data path: %s", __func__, ys->xpath);

lib/yang.c

@@ -251,6 +251,38 @@ void yang_snode_get_path(const struct lysc_node *snode,
 	}
 }
 
+LY_ERR yang_resolve_snode_xpath(struct ly_ctx *ly_ctx, const char *xpath,
+				struct lysc_node ***snodes, bool *simple)
+{
+	struct lysc_node *snode;
+	struct ly_set *set;
+	LY_ERR err;
+
+	/* lys_find_path will not resolve complex xpaths */
+	snode = (struct lysc_node *)lys_find_path(ly_ctx, NULL, xpath, 0);
+	if (snode) {
+		*darr_append(*snodes) = snode;
+		*simple = true;
+		return LY_SUCCESS;
+	}
+
+	/* Try again to catch complex query cases */
+	err = lys_find_xpath(ly_native_ctx, NULL, xpath, 0, &set);
+	if (err)
+		return err;
+	if (!set->count) {
+		ly_set_free(set, NULL);
+		return LY_ENOTFOUND;
+	}
+
+	*simple = false;
+	darr_ensure_i(*snodes, set->count - 1);
+	memcpy(*snodes, set->snodes, set->count * sizeof(set->snodes[0]));
+	ly_set_free(set, NULL);
+	return LY_SUCCESS;
+}
+
+
 struct lysc_node *yang_find_snode(struct ly_ctx *ly_ctx, const char *xpath,
 				  uint32_t options)
 {
@@ -1019,3 +1051,76 @@ LY_ERR yang_lyd_new_list(struct lyd_node_inner *parent,
 	/*NOTREACHED*/
 	return LY_EINVAL;
 }
+
+
+int yang_trim_tree(struct lyd_node *root, const char *xpath)
+{
+	enum nb_error ret = NB_OK;
+	LY_ERR err;
+#if 0
+	err = lyd_trim_xpath(&root, xpath, NULL);
+	if (err) {
+		flog_err_sys(EC_LIB_LIBYANG,
+			     "cannot obtain specific result for xpath \"%s\"",
+			     xpath);
+		return NB_ERR;
+	}
+	return NB_OK;
+#else
+	struct lyd_node *node;
+	struct lyd_node **remove = NULL;
+	struct ly_set *set = NULL;
+	uint32_t i;
+
+	err = lyd_find_xpath3(NULL, root, xpath, NULL, &set);
+	if (err) {
+		flog_err_sys(EC_LIB_LIBYANG,
+			     "cannot obtain specific result for xpath \"%s\"",
+			     xpath);
+		ret = NB_ERR;
+		goto done;
+	}
+	/*
+	 * Mark keepers and sweep deleting non-keepers.
+ 	 *
+	 * NOTE: We assume the data-nodes have NULL priv pointers and use that
+	 * for our mark.
+	 */
+
+	/* Mark */
+	for (i = 0; i < set->count; i++) {
+		for (node = set->dnodes[i]; node; node = &node->parent->node) {
+			if (node->priv)
+				break;
+			if (node == set->dnodes[i])
+				node->priv = (void *)2;
+			else
+				node->priv = (void *)1;
+		}
+	}
+
+	darr_ensure_cap(remove, 128);
+	LYD_TREE_DFS_BEGIN (root, node) {
+		/*
+		 * If this is a direct matching node then include it's subtree
+		 * which won't be marked and would otherwise be removed.
+		 */
+		if (node->priv == (void *)2)
+			LYD_TREE_DFS_continue = 1;
+		else if (!node->priv) {
+			LYD_TREE_DFS_continue = 1;
+			*darr_append(remove) = node;
+		}
+		LYD_TREE_DFS_END(root, node);
+	}
+	darr_foreach_i (remove, i)
+		lyd_free_tree(remove[i]);
+	darr_free(remove);
+
+done:
+	if (set)
+		ly_set_free(set, NULL);
+
+	return ret;
+#endif
+}

lib/yang.h

@@ -724,6 +724,35 @@ extern LY_ERR yang_lyd_new_list(struct lyd_node_inner *parent,
 				const struct lysc_node *snode,
 				const struct yang_list_keys *keys,
 				struct lyd_node_inner **node);
+/**
+ * yang_resolve_snodes() - Resolve an XPath to matching schema nodes.
+ * @ly_ctx: libyang context to operate on.
+ * @xpath: the path or XPath to resolve.
+ * @snodes: [OUT] pointer for resulting dynamic array (darr) of schema node
+ *          pointers.
+ * @simple: [OUT] indicates if @xpath was resolvable simply or not. Non-simple
+ *          means that the @xpath is not a simple path and utilizes XPath 1.0
+ *          functionality beyond simple key predicates.
+ *
+ * This function can be used to find the schema node (or nodes) that correspond
+ * to a given @xpath. If the @xpath includes non-key predicates (e.g., using
+ * functions) then @simple will be set to false, and @snodes may contain more
+ * than a single schema node.
+ *
+ * Return: a libyang error or LY_SUCCESS.
+ */
+extern LY_ERR yang_resolve_snode_xpath(struct ly_ctx *ly_ctx, const char *xpath,
+				       struct lysc_node ***snodes, bool *simple);
+
+/**
+ * yang_trim_tree() - trim the data tree to the given xpath
+ * @root: the data tree
+ * @xpath: the xpath to trim @root to.
+ *
+ * Return: enum nb_error..
+ */
+extern int yang_trim_tree(struct lyd_node *root, const char *xpath);
+
 #ifdef __cplusplus
 }
 #endif

mgmtd/mgmt_fe_adapter.c

@@ -1132,29 +1132,54 @@ static int fe_adapter_send_tree_data(struct mgmt_fe_session_ctx *session,
 }
 
 /**
- * Handle a get-tree message from the client.
+ * fe_adapter_handle_get_tree() - Handle a get-tree message from a FE client.
+ * @session: the client session.
+ * @msg_raw: the message data.
+ * @msg_len: the length of the message data.
  */
 static void fe_adapter_handle_get_tree(struct mgmt_fe_session_ctx *session,
-				       void *data, size_t len)
+				       void *__msg, size_t msg_len)
 {
-	struct mgmt_msg_get_tree *msg = data;
+	struct mgmt_msg_get_tree *msg = __msg;
+	struct lysc_node **snodes = NULL;
+	char *xpath_resolved = NULL;
 	uint64_t req_id = msg->req_id;
 	uint64_t clients;
+	bool simple_xpath;
+	LY_ERR err;
 	int ret;
 
 	MGMTD_FE_ADAPTER_DBG("Received get-tree request from client %s for session-id %" PRIu64
 			     " req-id %" PRIu64,
 			     session->adapter->name, session->session_id,
 			     msg->req_id);
 
+	if (!MGMT_MSG_VALIDATE_NUL_TERM(msg, msg_len)) {
+		fe_adapter_send_error(session, req_id, false, -EINVAL,
+				      "Invalid message rcvd from session-id: %" PRIu64,
+				      session->session_id);
+		goto done;
+	}
+
 	if (session->txn_id != MGMTD_TXN_ID_NONE) {
 		fe_adapter_send_error(session, req_id, false, -EINPROGRESS,
 				      "Transaction in progress txn-id: %" PRIu64
 				      " for session-id: %" PRIu64,
 				      session->txn_id, session->session_id);
-		return;
+		goto done;
 	}
 
+
+	err = yang_resolve_snode_xpath(ly_native_ctx, msg->xpath, &snodes,
+				       &simple_xpath);
+	if (err) {
+		fe_adapter_send_error(session, req_id, false, -EINPROGRESS,
+				      "XPath doesn't resolve for session-id: %" PRIu64,
+				      session->session_id);
+		goto done;
+	}
+	darr_free(snodes);
+
 	clients = mgmt_be_interested_clients(msg->xpath, false);
 	if (!clients) {
 		MGMTD_FE_ADAPTER_DBG("No backends provide xpath: %s for txn-id: %" PRIu64
@@ -1164,7 +1189,7 @@ static void fe_adapter_handle_get_tree(struct mgmt_fe_session_ctx *session,
 
 		fe_adapter_send_tree_data(session, req_id, false,
 					  msg->result_type, NULL, 0);
-		return;
+		goto done;
 	}
 
 	/* Start a SHOW Transaction */
@@ -1173,7 +1198,7 @@ static void fe_adapter_handle_get_tree(struct mgmt_fe_session_ctx *session,
 	if (session->txn_id == MGMTD_SESSION_ID_NONE) {
 		fe_adapter_send_error(session, req_id, false, -EINPROGRESS,
 				      "failed to create a 'show' txn");
-		return;
+		goto done;
 	}
 
 	MGMTD_FE_ADAPTER_DBG("Created new show txn-id: %" PRIu64
@@ -1182,13 +1207,17 @@ static void fe_adapter_handle_get_tree(struct mgmt_fe_session_ctx *session,
 
 	/* Create a GET-TREE request under the transaction */
 	ret = mgmt_txn_send_get_tree_oper(session->txn_id, req_id, clients,
-					  msg->result_type, msg->xpath);
+					  msg->result_type, simple_xpath,
+					  msg->xpath);
 	if (ret) {
 		/* destroy the just created txn */
 		mgmt_destroy_txn(&session->txn_id);
 		fe_adapter_send_error(session, req_id, false, -EINPROGRESS,
 				      "failed to create a 'show' txn");
 	}
+done:
+	darr_free(snodes);
+	darr_free(xpath_resolved);
 }
 
 /**