mgmtd: Add MGMT Backend Interface Framework

This commit introduces the MGMT Backend Interface which can be used
by back-end management client daemons like BGPd, Staticd, Zebra to
connect with new FRR Management daemon (MGMTd) and utilize the new
FRR Management Framework to let any Frontend clients to retrieve any
operational data or manipulate any configuration data owned by the
individual Backend daemon component.

This commit includes the following functionalities in the changeset:
1. Add new Backend server for Backend daemons connect to.
2. Add a C-based Backend client library which can be used by daemons
   to communicate with MGMTd via the Backend interface.
3. Maintain a backend adapter for each connection from an appropriate
   Backend client to facilitate client requests and track one or more
   transactions initiated from Frontend client sessions that involves
   the backend client component.
4. Add the following commands to inspect various Backend client
   related information
	a. show mgmt backend-adapter all
	b. show mgmt backend-yang-xpath-registry
        c. show mgmt yang-xpath-subscription

Co-authored-by: Pushpasis Sarkar <pushpasis@gmail.com>
Co-authored-by: Abhinay Ramesh <rabhinay@vmware.com>
Co-authored-by: Ujwal P <ujwalp@vmware.com>
Signed-off-by: Yash Ranjan <ranjany@vmware.com>

1 files changed, 79 insertions, 7 deletions

diff --git a/lib/northbound.h b/lib/northbound.h
index 572d669dc1..b63b216b0d 100644
--- a/lib/northbound.h
+++ b/lib/northbound.h
@@ -22,6 +22,39 @@ extern "C" {
 struct vty;
 struct debug;
 
+struct nb_yang_xpath_tag {
+	uint32_t ns;
+	uint32_t id;
+};
+
+struct nb_yang_value {
+	struct lyd_value value;
+	LY_DATA_TYPE value_type;
+	uint8_t value_flags;
+};
+
+struct nb_yang_xpath_elem {
+	struct nb_yang_xpath_tag tag;
+	struct nb_yang_value val;
+};
+
+#define NB_MAX_NUM_KEYS UINT8_MAX
+#define NB_MAX_NUM_XPATH_TAGS UINT8_MAX
+
+struct nb_yang_xpath {
+	uint8_t length;
+	struct {
+		uint8_t num_keys;
+		struct nb_yang_xpath_elem keys[NB_MAX_NUM_KEYS];
+	} tags[NB_MAX_NUM_XPATH_TAGS];
+};
+
+#define NB_YANG_XPATH_KEY(__xpath, __indx1, __indx2)                           \
+	((__xpath->num_tags > __indx1)                                         \
+			 && (__xpath->tags[__indx1].num_keys > __indx2)        \
+		 ? &__xpath->tags[__indx1].keys[__indx2]                       \
+		 : NULL)
+
 /* Northbound events. */
 enum nb_event {
 	/*
@@ -564,6 +597,8 @@ struct nb_node {
 #define F_NB_NODE_CONFIG_ONLY 0x01
 /* The YANG list doesn't contain key leafs. */
 #define F_NB_NODE_KEYLESS_LIST 0x02
+/* Ignore callbacks for this node */
+#define F_NB_NODE_IGNORE_CBS 0x04
 
 /*
  * HACK: old gcc versions (< 5.x) have a bug that prevents C99 flexible arrays
@@ -576,6 +611,12 @@ struct frr_yang_module_info {
 	/* YANG module name. */
 	const char *name;
 
+	/*
+	 * Ignore callbacks for this module. Set this to true to
+	 * load module without any callbacks.
+	 */
+	bool ignore_cbs;
+
 	/* Northbound callbacks. */
 	const struct {
 		/* Data path of this YANG node. */
@@ -620,6 +661,7 @@ enum nb_client {
 	NB_CLIENT_GRPC,
 	NB_CLIENT_PCEP,
 	NB_CLIENT_MGMTD_SERVER,
+	NB_CLIENT_MGMTD_BE,
 };
 
 /* Northbound context. */
@@ -631,12 +673,6 @@ struct nb_context {
 	const void *user;
 };
 
-/* Northbound configuration. */
-struct nb_config {
-	struct lyd_node *dnode;
-	uint32_t version;
-};
-
 /* Northbound configuration callback. */
 struct nb_config_cb {
 	RB_ENTRY(nb_config_cb) entry;
@@ -663,6 +699,13 @@ struct nb_transaction {
 	struct nb_config_cbs changes;
 };
 
+/* Northbound configuration. */
+struct nb_config {
+	struct lyd_node *dnode;
+	uint32_t version;
+	struct nb_config_cbs cfg_chgs;
+};
+
 /* Callback function used by nb_oper_data_iterate(). */
 typedef int (*nb_oper_data_cb)(const struct lysc_node *snode,
 			       struct yang_translator *translator,
@@ -832,6 +875,9 @@ extern int nb_candidate_edit(struct nb_config *candidate,
 			     const struct yang_data *previous,
 			     const struct yang_data *data);
 
+extern void nb_config_diff_created(const struct lyd_node *dnode, uint32_t *seq,
+				   struct nb_config_cbs *changes);
+
 /*
  * Check if a candidate configuration is outdated and needs to be updated.
  *
@@ -843,6 +889,30 @@ extern int nb_candidate_edit(struct nb_config *candidate,
  */
 extern bool nb_candidate_needs_update(const struct nb_config *candidate);
 
+extern void nb_candidate_edit_config_changes(
+	struct nb_config *candidate_config, struct nb_cfg_change cfg_changes[],
+	size_t num_cfg_changes, const char *xpath_base, const char *curr_xpath,
+	int xpath_index, char *err_buf, int err_bufsize, bool *error);
+
+extern void nb_config_diff_del_changes(struct nb_config_cbs *changes);
+
+extern int nb_candidate_diff_and_validate_yang(struct nb_context *context,
+					       struct nb_config *candidate,
+					       struct nb_config_cbs *changes,
+					       char *errmsg, size_t errmsg_len);
+
+extern void nb_config_diff(const struct nb_config *reference,
+			   const struct nb_config *incremental,
+			   struct nb_config_cbs *changes);
+
+extern int nb_candidate_validate_yang(struct nb_config *candidate, char *errmsg,
+				      size_t errmsg_len);
+
+extern int nb_candidate_validate_code(struct nb_context *context,
+				      struct nb_config *candidate,
+				      struct nb_config_cbs *changes,
+				      char *errmsg, size_t errmsg_len);
+
 /*
  * Update a candidate configuration by rebasing the changes on top of the latest
  * running configuration. Resolve conflicts automatically by giving preference
@@ -922,7 +992,9 @@ extern int nb_candidate_commit_prepare(struct nb_context context,
 				       struct nb_config *candidate,
 				       const char *comment,
 				       struct nb_transaction **transaction,
-				       char *errmsg, size_t errmsg_len);
+				       bool skip_validate,
+				       bool ignore_zero_change, char *errmsg,
+				       size_t errmsg_len);
 
 /*
  * Abort a previously created configuration transaction, releasing all resources