Merge pull request #6414 from opensourcerouting/nb-error-handling

NB context + enhanced error handling

16 files changed, 720 insertions, 313 deletions

diff --git a/isisd/isis_nb_config.c b/isisd/isis_nb_config.c
index a649e896fa..9633e46415 100644
--- a/isisd/isis_nb_config.c
+++ b/isisd/isis_nb_config.c
@@ -116,8 +116,8 @@ int isis_instance_area_address_create(struct nb_cb_create_args *args)
 		addr.addr_len = dotformat2buff(buff, net_title);
 		memcpy(addr.area_addr, buff, addr.addr_len);
 		if (addr.area_addr[addr.addr_len - 1] != 0) {
-			flog_warn(
-				EC_LIB_NB_CB_CONFIG_VALIDATE,
+			snprintf(
+				args->errmsg, args->errmsg_len,
 				"nsel byte (last byte) in area address must be 0");
 			return NB_ERR_VALIDATION;
 		}
@@ -125,8 +125,8 @@ int isis_instance_area_address_create(struct nb_cb_create_args *args)
 			/* Check that the SystemID portions match */
 			if (memcmp(isis->sysid, GETSYSID((&addr)),
 				   ISIS_SYS_ID_LEN)) {
-				flog_warn(
-					EC_LIB_NB_CB_CONFIG_VALIDATE,
+				snprintf(
+					args->errmsg, args->errmsg_len,
 					"System ID must not change when defining additional area addresses");
 				return NB_ERR_VALIDATION;
 			}
@@ -332,8 +332,8 @@ int isis_instance_lsp_mtu_modify(struct nb_cb_modify_args *args)
 			    && circuit->state != C_STATE_UP)
 				continue;
 			if (lsp_mtu > isis_circuit_pdu_size(circuit)) {
-				flog_warn(
-					EC_LIB_NB_CB_CONFIG_VALIDATE,
+				snprintf(
+					args->errmsg, args->errmsg_len,
 					"ISIS area contains circuit %s, which has a maximum PDU size of %zu",
 					circuit->interface->name,
 					isis_circuit_pdu_size(circuit));
@@ -1047,6 +1047,7 @@ int isis_instance_redistribute_ipv6_metric_modify(
  */
 static int isis_multi_topology_common(enum nb_event event,
 				      const struct lyd_node *dnode,
+				      char *errmsg, size_t errmsg_len,
 				      const char *topology, bool create)
 {
 	struct isis_area *area;
@@ -1056,8 +1057,8 @@ static int isis_multi_topology_common(enum nb_event event,
 	switch (event) {
 	case NB_EV_VALIDATE:
 		if (mtid == (uint16_t)-1) {
-			flog_warn(EC_LIB_NB_CB_CONFIG_VALIDATE,
-				  "Unknown topology %s", topology);
+			snprintf(errmsg, errmsg_len, "Unknown topology %s",
+				 topology);
 			return NB_ERR_VALIDATION;
 		}
 		break;
@@ -1100,6 +1101,7 @@ int isis_instance_multi_topology_ipv4_multicast_create(
 	struct nb_cb_create_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv4-multicast", true);
 }
 
@@ -1107,6 +1109,7 @@ int isis_instance_multi_topology_ipv4_multicast_destroy(
 	struct nb_cb_destroy_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv4-multicast", false);
 }
 
@@ -1126,15 +1129,17 @@ int isis_instance_multi_topology_ipv4_multicast_overload_modify(
 int isis_instance_multi_topology_ipv4_management_create(
 	struct nb_cb_create_args *args)
 {
-	return isis_multi_topology_common(args->event, args->dnode, "ipv4-mgmt",
-					  true);
+	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
+					  "ipv4-mgmt", true);
 }
 
 int isis_instance_multi_topology_ipv4_management_destroy(
 	struct nb_cb_destroy_args *args)
 {
-	return isis_multi_topology_common(args->event, args->dnode, "ipv4-mgmt",
-					  false);
+	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
+					  "ipv4-mgmt", false);
 }
 
 /*
@@ -1154,6 +1159,7 @@ int isis_instance_multi_topology_ipv6_unicast_create(
 	struct nb_cb_create_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv6-unicast", true);
 }
 
@@ -1161,6 +1167,7 @@ int isis_instance_multi_topology_ipv6_unicast_destroy(
 	struct nb_cb_destroy_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv6-unicast", false);
 }
 
@@ -1181,6 +1188,7 @@ int isis_instance_multi_topology_ipv6_multicast_create(
 	struct nb_cb_create_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv6-multicast", true);
 }
 
@@ -1188,6 +1196,7 @@ int isis_instance_multi_topology_ipv6_multicast_destroy(
 	struct nb_cb_destroy_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv6-multicast", false);
 }
 
@@ -1207,15 +1216,17 @@ int isis_instance_multi_topology_ipv6_multicast_overload_modify(
 int isis_instance_multi_topology_ipv6_management_create(
 	struct nb_cb_create_args *args)
 {
-	return isis_multi_topology_common(args->event, args->dnode, "ipv6-mgmt",
-					  true);
+	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
+					  "ipv6-mgmt", true);
 }
 
 int isis_instance_multi_topology_ipv6_management_destroy(
 	struct nb_cb_destroy_args *args)
 {
-	return isis_multi_topology_common(args->event, args->dnode, "ipv6-mgmt",
-					  false);
+	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
+					  "ipv6-mgmt", false);
 }
 
 /*
@@ -1235,6 +1246,7 @@ int isis_instance_multi_topology_ipv6_dstsrc_create(
 	struct nb_cb_create_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv6-dstsrc", true);
 }
 
@@ -1242,6 +1254,7 @@ int isis_instance_multi_topology_ipv6_dstsrc_destroy(
 	struct nb_cb_destroy_args *args)
 {
 	return isis_multi_topology_common(args->event, args->dnode,
+					  args->errmsg, args->errmsg_len,
 					  "ipv6-dstsrc", false);
 }
 
@@ -1721,10 +1734,10 @@ int lib_interface_isis_create(struct nb_cb_create_args *args)
 			min_mtu = DEFAULT_LSP_MTU;
 #endif /* ifndef FABRICD */
 		if (actual_mtu < min_mtu) {
-			flog_warn(EC_LIB_NB_CB_CONFIG_VALIDATE,
-				  "Interface %s has MTU %" PRIu32
-				  ", minimum MTU for the area is %" PRIu32 "",
-				  ifp->name, actual_mtu, min_mtu);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "Interface %s has MTU %" PRIu32
+				 ", minimum MTU for the area is %" PRIu32 "",
+				 ifp->name, actual_mtu, min_mtu);
 			return NB_ERR_VALIDATION;
 		}
 		break;
@@ -1801,9 +1814,9 @@ int lib_interface_isis_area_tag_modify(struct nb_cb_modify_args *args)
 		area_tag = yang_dnode_get_string(args->dnode, NULL);
 		if (circuit && circuit->area && circuit->area->area_tag
 		    && strcmp(circuit->area->area_tag, area_tag)) {
-			flog_warn(EC_LIB_NB_CB_CONFIG_VALIDATE,
-				  "ISIS circuit is already defined on %s",
-				  circuit->area->area_tag);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "ISIS circuit is already defined on %s",
+				 circuit->area->area_tag);
 			return NB_ERR_VALIDATION;
 		}
 	}
@@ -1839,9 +1852,9 @@ int lib_interface_isis_circuit_type_modify(struct nb_cb_modify_args *args)
 		if (circuit && circuit->state == C_STATE_UP
 		    && circuit->area->is_type != IS_LEVEL_1_AND_2
 		    && circuit->area->is_type != circ_type) {
-			flog_warn(EC_LIB_NB_CB_CONFIG_VALIDATE,
-				  "Invalid circuit level for area %s",
-				  circuit->area->area_tag);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "Invalid circuit level for area %s",
+				 circuit->area->area_tag);
 			return NB_ERR_VALIDATION;
 		}
 		break;
@@ -2163,16 +2176,16 @@ int lib_interface_isis_network_type_modify(struct nb_cb_modify_args *args)
 		if (!circuit)
 			break;
 		if (circuit->circ_type == CIRCUIT_T_LOOPBACK) {
-			flog_warn(
-				EC_LIB_NB_CB_CONFIG_VALIDATE,
+			snprintf(
+				args->errmsg, args->errmsg_len,
 				"Cannot change network type on loopback interface");
 			return NB_ERR_VALIDATION;
 		}
 		if (net_type == CIRCUIT_T_BROADCAST
 		    && circuit->state == C_STATE_UP
 		    && !if_is_broadcast(circuit->interface)) {
-			flog_warn(
-				EC_LIB_NB_CB_CONFIG_VALIDATE,
+			snprintf(
+				args->errmsg, args->errmsg_len,
 				"Cannot configure non-broadcast interface for broadcast operation");
 			return NB_ERR_VALIDATION;
 		}
@@ -2208,8 +2221,8 @@ int lib_interface_isis_passive_modify(struct nb_cb_modify_args *args)
 		if (!ifp)
 			return NB_OK;
 		if (if_is_loopback(ifp)) {
-			flog_warn(EC_LIB_NB_CB_CONFIG_VALIDATE,
-				  "Loopback is always passive");
+			snprintf(args->errmsg, args->errmsg_len,
+				 "Loopback is always passive");
 			return NB_ERR_VALIDATION;
 		}
 	}
@@ -2312,7 +2325,8 @@ int lib_interface_isis_disable_three_way_handshake_modify(
  * /frr-interface:lib/interface/frr-isisd:isis/multi-topology/ipv4-unicast
  */
 static int lib_interface_isis_multi_topology_common(
-	enum nb_event event, const struct lyd_node *dnode, uint16_t mtid)
+	enum nb_event event, const struct lyd_node *dnode, char *errmsg,
+	size_t errmsg_len, uint16_t mtid)
 {
 	struct isis_circuit *circuit;
 	bool value;
@@ -2321,8 +2335,8 @@ static int lib_interface_isis_multi_topology_common(
 	case NB_EV_VALIDATE:
 		circuit = nb_running_get_entry(dnode, NULL, false);
 		if (circuit && circuit->area && circuit->area->oldmetric) {
-			flog_warn(
-				EC_LIB_NB_CB_CONFIG_VALIDATE,
+			snprintf(
+				errmsg, errmsg_len,
 				"Multi topology IS-IS can only be used with wide metrics");
 			return NB_ERR_VALIDATION;
 		}
@@ -2344,7 +2358,8 @@ int lib_interface_isis_multi_topology_ipv4_unicast_modify(
 	struct nb_cb_modify_args *args)
 {
 	return lib_interface_isis_multi_topology_common(
-		args->event, args->dnode, ISIS_MT_IPV4_UNICAST);
+		args->event, args->dnode, args->errmsg, args->errmsg_len,
+		ISIS_MT_IPV4_UNICAST);
 }
 
 /*
@@ -2355,7 +2370,8 @@ int lib_interface_isis_multi_topology_ipv4_multicast_modify(
 	struct nb_cb_modify_args *args)
 {
 	return lib_interface_isis_multi_topology_common(
-		args->event, args->dnode, ISIS_MT_IPV4_MULTICAST);
+		args->event, args->dnode, args->errmsg, args->errmsg_len,
+		ISIS_MT_IPV4_MULTICAST);
 }
 
 /*
@@ -2366,7 +2382,8 @@ int lib_interface_isis_multi_topology_ipv4_management_modify(
 	struct nb_cb_modify_args *args)
 {
 	return lib_interface_isis_multi_topology_common(
-		args->event, args->dnode, ISIS_MT_IPV4_MGMT);
+		args->event, args->dnode, args->errmsg, args->errmsg_len,
+		ISIS_MT_IPV4_MGMT);
 }
 
 /*
@@ -2377,7 +2394,8 @@ int lib_interface_isis_multi_topology_ipv6_unicast_modify(
 	struct nb_cb_modify_args *args)
 {
 	return lib_interface_isis_multi_topology_common(
-		args->event, args->dnode, ISIS_MT_IPV6_UNICAST);
+		args->event, args->dnode, args->errmsg, args->errmsg_len,
+		ISIS_MT_IPV6_UNICAST);
 }
 
 /*
@@ -2388,7 +2406,8 @@ int lib_interface_isis_multi_topology_ipv6_multicast_modify(
 	struct nb_cb_modify_args *args)
 {
 	return lib_interface_isis_multi_topology_common(
-		args->event, args->dnode, ISIS_MT_IPV6_MULTICAST);
+		args->event, args->dnode, args->errmsg, args->errmsg_len,
+		ISIS_MT_IPV6_MULTICAST);
 }
 
 /*
@@ -2399,7 +2418,8 @@ int lib_interface_isis_multi_topology_ipv6_management_modify(
 	struct nb_cb_modify_args *args)
 {
 	return lib_interface_isis_multi_topology_common(
-		args->event, args->dnode, ISIS_MT_IPV6_MGMT);
+		args->event, args->dnode, args->errmsg, args->errmsg_len,
+		ISIS_MT_IPV6_MGMT);
 }
 
 /*
@@ -2409,5 +2429,6 @@ int lib_interface_isis_multi_topology_ipv6_dstsrc_modify(
 	struct nb_cb_modify_args *args)
 {
 	return lib_interface_isis_multi_topology_common(
-		args->event, args->dnode, ISIS_MT_IPV6_DSTSRC);
+		args->event, args->dnode, args->errmsg, args->errmsg_len,
+		ISIS_MT_IPV6_DSTSRC);
 }
diff --git a/lib/if.c b/lib/if.c
index b34744f80d..f03574e787 100644
--- a/lib/if.c
+++ b/lib/if.c
@@ -1567,8 +1567,8 @@ static int lib_interface_destroy(struct nb_cb_destroy_args *args)
 	case NB_EV_VALIDATE:
 		ifp = nb_running_get_entry(args->dnode, NULL, true);
 		if (CHECK_FLAG(ifp->status, ZEBRA_INTERFACE_ACTIVE)) {
-			zlog_warn("%s: only inactive interfaces can be deleted",
-				  __func__);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "only inactive interfaces can be deleted");
 			return NB_ERR_VALIDATION;
 		}
 		break;
diff --git a/lib/libfrr.c b/lib/libfrr.c
index ac165f254e..cac9929577 100644
--- a/lib/libfrr.c
+++ b/lib/libfrr.c
@@ -902,14 +902,18 @@ static int frr_config_read_in(struct thread *t)
 	 * reading the configuration file.
 	 */
 	if (frr_get_cli_mode() == FRR_CLI_TRANSACTIONAL) {
+		struct nb_context context = {};
+		char errmsg[BUFSIZ] = {0};
 		int ret;
 
-		ret = nb_candidate_commit(vty_shared_candidate_config,
-					  NB_CLIENT_CLI, NULL, true,
-					  "Read configuration file", NULL);
+		context.client = NB_CLIENT_CLI;
+		ret = nb_candidate_commit(&context, vty_shared_candidate_config,
+					  true, "Read configuration file", NULL,
+					  errmsg, sizeof(errmsg));
 		if (ret != NB_OK && ret != NB_ERR_NO_CHANGES)
-			zlog_err("%s: failed to read configuration file.",
-				 __func__);
+			zlog_err(
+				"%s: failed to read configuration file: %s (%s)",
+				__func__, nb_err_name(ret), errmsg);
 	}
 
 	return 0;
diff --git a/lib/northbound.c b/lib/northbound.c
index e393c33928..48b8499bfc 100644
--- a/lib/northbound.c
+++ b/lib/northbound.c
@@ -63,19 +63,24 @@ static struct {
  */
 static bool transaction_in_progress;
 
-static int nb_callback_pre_validate(const struct nb_node *nb_node,
-				    const struct lyd_node *dnode);
-static int nb_callback_configuration(const enum nb_event event,
-				     struct nb_config_change *change);
-static struct nb_transaction *nb_transaction_new(struct nb_config *config,
-						 struct nb_config_cbs *changes,
-						 enum nb_client client,
-						 const void *user,
-						 const char *comment);
+static int nb_callback_pre_validate(struct nb_context *context,
+				    const struct nb_node *nb_node,
+				    const struct lyd_node *dnode, char *errmsg,
+				    size_t errmsg_len);
+static int nb_callback_configuration(struct nb_context *context,
+				     const enum nb_event event,
+				     struct nb_config_change *change,
+				     char *errmsg, size_t errmsg_len);
+static struct nb_transaction *
+nb_transaction_new(struct nb_context *context, struct nb_config *config,
+		   struct nb_config_cbs *changes, const char *comment,
+		   char *errmsg, size_t errmsg_len);
 static void nb_transaction_free(struct nb_transaction *transaction);
 static int nb_transaction_process(enum nb_event event,
-				  struct nb_transaction *transaction);
-static void nb_transaction_apply_finish(struct nb_transaction *transaction);
+				  struct nb_transaction *transaction,
+				  char *errmsg, size_t errmsg_len);
+static void nb_transaction_apply_finish(struct nb_transaction *transaction,
+					char *errmsg, size_t errmsg_len);
 static int nb_oper_data_iter_node(const struct lys_node *snode,
 				  const char *xpath, const void *list_entry,
 				  const struct yang_list_keys *list_keys,
@@ -581,20 +586,25 @@ int nb_candidate_update(struct nb_config *candidate)
  * WARNING: lyd_validate() can change the configuration as part of the
  * validation process.
  */
-static int nb_candidate_validate_yang(struct nb_config *candidate)
+static int nb_candidate_validate_yang(struct nb_config *candidate, char *errmsg,
+				      size_t errmsg_len)
 {
 	if (lyd_validate(&candidate->dnode,
 			 LYD_OPT_STRICT | LYD_OPT_CONFIG | LYD_OPT_WHENAUTODEL,
 			 ly_native_ctx)
-	    != 0)
+	    != 0) {
+		yang_print_errors(ly_native_ctx, errmsg, errmsg_len);
 		return NB_ERR_VALIDATION;
+	}
 
 	return NB_OK;
 }
 
 /* Perform code-level validation using the northbound callbacks. */
-static int nb_candidate_validate_code(struct nb_config *candidate,
-				      struct nb_config_cbs *changes)
+static int nb_candidate_validate_code(struct nb_context *context,
+				      struct nb_config *candidate,
+				      struct nb_config_cbs *changes,
+				      char *errmsg, size_t errmsg_len)
 {
 	struct nb_config_cb *cb;
 	struct lyd_node *root, *next, *child;
@@ -609,7 +619,8 @@ static int nb_candidate_validate_code(struct nb_config *candidate,
 			if (!nb_node->cbs.pre_validate)
 				goto next;
 
-			ret = nb_callback_pre_validate(nb_node, child);
+			ret = nb_callback_pre_validate(context, nb_node, child,
+						       errmsg, errmsg_len);
 			if (ret != NB_OK)
 				return NB_ERR_VALIDATION;
 
@@ -622,7 +633,8 @@ static int nb_candidate_validate_code(struct nb_config *candidate,
 	RB_FOREACH (cb, nb_config_cbs, changes) {
 		struct nb_config_change *change = (struct nb_config_change *)cb;
 
-		ret = nb_callback_configuration(NB_EV_VALIDATE, change);
+		ret = nb_callback_configuration(context, NB_EV_VALIDATE, change,
+						errmsg, errmsg_len);
 		if (ret != NB_OK)
 			return NB_ERR_VALIDATION;
 	}
@@ -630,30 +642,36 @@ static int nb_candidate_validate_code(struct nb_config *candidate,
 	return NB_OK;
 }
 
-int nb_candidate_validate(struct nb_config *candidate)
+int nb_candidate_validate(struct nb_context *context,
+			  struct nb_config *candidate, char *errmsg,
+			  size_t errmsg_len)
 {
 	struct nb_config_cbs changes;
 	int ret;
 
-	if (nb_candidate_validate_yang(candidate) != NB_OK)
+	if (nb_candidate_validate_yang(candidate, errmsg, sizeof(errmsg_len))
+	    != NB_OK)
 		return NB_ERR_VALIDATION;
 
 	RB_INIT(nb_config_cbs, &changes);
 	nb_config_diff(running_config, candidate, &changes);
-	ret = nb_candidate_validate_code(candidate, &changes);
+	ret = nb_candidate_validate_code(context, candidate, &changes, errmsg,
+					 errmsg_len);
 	nb_config_diff_del_changes(&changes);
 
 	return ret;
 }
 
-int nb_candidate_commit_prepare(struct nb_config *candidate,
-				enum nb_client client, const void *user,
+int nb_candidate_commit_prepare(struct nb_context *context,
+				struct nb_config *candidate,
 				const char *comment,
-				struct nb_transaction **transaction)
+				struct nb_transaction **transaction,
+				char *errmsg, size_t errmsg_len)
 {
 	struct nb_config_cbs changes;
 
-	if (nb_candidate_validate_yang(candidate) != NB_OK) {
+	if (nb_candidate_validate_yang(candidate, errmsg, errmsg_len)
+	    != NB_OK) {
 		flog_warn(EC_LIB_NB_CANDIDATE_INVALID,
 			  "%s: failed to validate candidate configuration",
 			  __func__);
@@ -665,7 +683,9 @@ int nb_candidate_commit_prepare(struct nb_config *candidate,
 	if (RB_EMPTY(nb_config_cbs, &changes))
 		return NB_ERR_NO_CHANGES;
 
-	if (nb_candidate_validate_code(candidate, &changes) != NB_OK) {
+	if (nb_candidate_validate_code(context, candidate, &changes, errmsg,
+				       errmsg_len)
+	    != NB_OK) {
 		flog_warn(EC_LIB_NB_CANDIDATE_INVALID,
 			  "%s: failed to validate candidate configuration",
 			  __func__);
@@ -673,29 +693,37 @@ int nb_candidate_commit_prepare(struct nb_config *candidate,
 		return NB_ERR_VALIDATION;
 	}
 
-	*transaction =
-		nb_transaction_new(candidate, &changes, client, user, comment);
+	*transaction = nb_transaction_new(context, candidate, &changes, comment,
+					  errmsg, errmsg_len);
 	if (*transaction == NULL) {
 		flog_warn(EC_LIB_NB_TRANSACTION_CREATION_FAILED,
-			  "%s: failed to create transaction", __func__);
+			  "%s: failed to create transaction: %s", __func__,
+			  errmsg);
 		nb_config_diff_del_changes(&changes);
 		return NB_ERR_LOCKED;
 	}
 
-	return nb_transaction_process(NB_EV_PREPARE, *transaction);
+	return nb_transaction_process(NB_EV_PREPARE, *transaction, errmsg,
+				      errmsg_len);
 }
 
 void nb_candidate_commit_abort(struct nb_transaction *transaction)
 {
-	(void)nb_transaction_process(NB_EV_ABORT, transaction);
+	char errmsg[BUFSIZ] = {0};
+
+	(void)nb_transaction_process(NB_EV_ABORT, transaction, errmsg,
+				     sizeof(errmsg));
 	nb_transaction_free(transaction);
 }
 
 void nb_candidate_commit_apply(struct nb_transaction *transaction,
 			       bool save_transaction, uint32_t *transaction_id)
 {
-	(void)nb_transaction_process(NB_EV_APPLY, transaction);
-	nb_transaction_apply_finish(transaction);
+	char errmsg[BUFSIZ] = {0};
+
+	(void)nb_transaction_process(NB_EV_APPLY, transaction, errmsg,
+				     sizeof(errmsg));
+	nb_transaction_apply_finish(transaction, errmsg, sizeof(errmsg));
 
 	/* Replace running by candidate. */
 	transaction->config->version++;
@@ -710,15 +738,16 @@ void nb_candidate_commit_apply(struct nb_transaction *transaction,
 	nb_transaction_free(transaction);
 }
 
-int nb_candidate_commit(struct nb_config *candidate, enum nb_client client,
-			const void *user, bool save_transaction,
-			const char *comment, uint32_t *transaction_id)
+int nb_candidate_commit(struct nb_context *context, struct nb_config *candidate,
+			bool save_transaction, const char *comment,
+			uint32_t *transaction_id, char *errmsg,
+			size_t errmsg_len)
 {
 	struct nb_transaction *transaction = NULL;
 	int ret;
 
-	ret = nb_candidate_commit_prepare(candidate, client, user, comment,
-					  &transaction);
+	ret = nb_candidate_commit_prepare(context, candidate, comment,
+					  &transaction, errmsg, errmsg_len);
 	/*
 	 * Apply the changes if the preparation phase succeeded. Otherwise abort
 	 * the transaction.
@@ -736,7 +765,7 @@ int nb_running_lock(enum nb_client client, const void *user)
 {
 	int ret = -1;
 
-	frr_with_mutex(&running_config_mgmt_lock.mtx) {
+	frr_with_mutex (&running_config_mgmt_lock.mtx) {
 		if (!running_config_mgmt_lock.locked) {
 			running_config_mgmt_lock.locked = true;
 			running_config_mgmt_lock.owner_client = client;
@@ -752,7 +781,7 @@ int nb_running_unlock(enum nb_client client, const void *user)
 {
 	int ret = -1;
 
-	frr_with_mutex(&running_config_mgmt_lock.mtx) {
+	frr_with_mutex (&running_config_mgmt_lock.mtx) {
 		if (running_config_mgmt_lock.locked
 		    && running_config_mgmt_lock.owner_client == client
 		    && running_config_mgmt_lock.owner_user == user) {
@@ -770,7 +799,7 @@ int nb_running_lock_check(enum nb_client client, const void *user)
 {
 	int ret = -1;
 
-	frr_with_mutex(&running_config_mgmt_lock.mtx) {
+	frr_with_mutex (&running_config_mgmt_lock.mtx) {
 		if (!running_config_mgmt_lock.locked
 		    || (running_config_mgmt_lock.owner_client == client
 			&& running_config_mgmt_lock.owner_user == user))
@@ -802,78 +831,237 @@ static void nb_log_config_callback(const enum nb_event event,
 		value);
 }
 
-static int nb_callback_create(const struct nb_node *nb_node,
+static int nb_callback_create(struct nb_context *context,
+			      const struct nb_node *nb_node,
 			      enum nb_event event, const struct lyd_node *dnode,
-			      union nb_resource *resource)
+			      union nb_resource *resource, char *errmsg,
+			      size_t errmsg_len)
 {
 	struct nb_cb_create_args args = {};
+	bool unexpected_error = false;
+	int ret;
 
 	nb_log_config_callback(event, NB_OP_CREATE, dnode);
 
+	args.context = context;
 	args.event = event;
 	args.dnode = dnode;
 	args.resource = resource;
-	return nb_node->cbs.create(&args);
+	args.errmsg = errmsg;
+	args.errmsg_len = errmsg_len;
+	ret = nb_node->cbs.create(&args);
+
+	/* Detect and log unexpected errors. */
+	switch (ret) {
+	case NB_OK:
+	case NB_ERR:
+		break;
+	case NB_ERR_VALIDATION:
+		if (event != NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	case NB_ERR_RESOURCE:
+		if (event != NB_EV_PREPARE)
+			unexpected_error = true;
+		break;
+	case NB_ERR_INCONSISTENCY:
+		if (event == NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	default:
+		unexpected_error = true;
+		break;
+	}
+	if (unexpected_error)
+		DEBUGD(&nb_dbg_cbs_config,
+		       "northbound callback: unexpected return value: %s",
+		       nb_err_name(ret));
+
+	return ret;
 }
 
-static int nb_callback_modify(const struct nb_node *nb_node,
+static int nb_callback_modify(struct nb_context *context,
+			      const struct nb_node *nb_node,
 			      enum nb_event event, const struct lyd_node *dnode,
-			      union nb_resource *resource)
+			      union nb_resource *resource, char *errmsg,
+			      size_t errmsg_len)
 {
 	struct nb_cb_modify_args args = {};
+	bool unexpected_error = false;
+	int ret;
 
 	nb_log_config_callback(event, NB_OP_MODIFY, dnode);
 
+	args.context = context;
 	args.event = event;
 	args.dnode = dnode;
 	args.resource = resource;
-	return nb_node->cbs.modify(&args);
+	args.errmsg = errmsg;
+	args.errmsg_len = errmsg_len;
+	ret = nb_node->cbs.modify(&args);
+
+	/* Detect and log unexpected errors. */
+	switch (ret) {
+	case NB_OK:
+	case NB_ERR:
+		break;
+	case NB_ERR_VALIDATION:
+		if (event != NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	case NB_ERR_RESOURCE:
+		if (event != NB_EV_PREPARE)
+			unexpected_error = true;
+		break;
+	case NB_ERR_INCONSISTENCY:
+		if (event == NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	default:
+		unexpected_error = true;
+		break;
+	}
+	if (unexpected_error)
+		DEBUGD(&nb_dbg_cbs_config,
+		       "northbound callback: unexpected return value: %s",
+		       nb_err_name(ret));
+
+	return ret;
 }
 
-static int nb_callback_destroy(const struct nb_node *nb_node,
+static int nb_callback_destroy(struct nb_context *context,
+			       const struct nb_node *nb_node,
 			       enum nb_event event,
-			       const struct lyd_node *dnode)
+			       const struct lyd_node *dnode, char *errmsg,
+			       size_t errmsg_len)
 {
 	struct nb_cb_destroy_args args = {};
+	bool unexpected_error = false;
+	int ret;
 
 	nb_log_config_callback(event, NB_OP_DESTROY, dnode);
 
+	args.context = context;
 	args.event = event;
 	args.dnode = dnode;
-	return nb_node->cbs.destroy(&args);
+	args.errmsg = errmsg;
+	args.errmsg_len = errmsg_len;
+	ret = nb_node->cbs.destroy(&args);
+
+	/* Detect and log unexpected errors. */
+	switch (ret) {
+	case NB_OK:
+	case NB_ERR:
+		break;
+	case NB_ERR_VALIDATION:
+		if (event != NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	case NB_ERR_INCONSISTENCY:
+		if (event == NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	default:
+		unexpected_error = true;
+		break;
+	}
+	if (unexpected_error)
+		DEBUGD(&nb_dbg_cbs_config,
+		       "northbound callback: unexpected return value: %s",
+		       nb_err_name(ret));
+
+	return ret;
 }
 
-static int nb_callback_move(const struct nb_node *nb_node, enum nb_event event,
-			    const struct lyd_node *dnode)
+static int nb_callback_move(struct nb_context *context,
+			    const struct nb_node *nb_node, enum nb_event event,
+			    const struct lyd_node *dnode, char *errmsg,
+			    size_t errmsg_len)
 {
 	struct nb_cb_move_args args = {};
+	bool unexpected_error = false;
+	int ret;
 
 	nb_log_config_callback(event, NB_OP_MOVE, dnode);
 
+	args.context = context;
 	args.event = event;
 	args.dnode = dnode;
-	return nb_node->cbs.move(&args);
+	args.errmsg = errmsg;
+	args.errmsg_len = errmsg_len;
+	ret = nb_node->cbs.move(&args);
+
+	/* Detect and log unexpected errors. */
+	switch (ret) {
+	case NB_OK:
+	case NB_ERR:
+		break;
+	case NB_ERR_VALIDATION:
+		if (event != NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	case NB_ERR_INCONSISTENCY:
+		if (event == NB_EV_VALIDATE)
+			unexpected_error = true;
+		break;
+	default:
+		unexpected_error = true;
+		break;
+	}
+	if (unexpected_error)
+		DEBUGD(&nb_dbg_cbs_config,
+		       "northbound callback: unexpected return value: %s",
+		       nb_err_name(ret));
+
+	return ret;
 }
 
-static int nb_callback_pre_validate(const struct nb_node *nb_node,
-				    const struct lyd_node *dnode)
+static int nb_callback_pre_validate(struct nb_context *context,
+				    const struct nb_node *nb_node,
+				    const struct lyd_node *dnode, char *errmsg,
+				    size_t errmsg_len)
 {
 	struct nb_cb_pre_validate_args args = {};
+	bool unexpected_error = false;
+	int ret;
 
 	nb_log_config_callback(NB_EV_VALIDATE, NB_OP_PRE_VALIDATE, dnode);
 
 	args.dnode = dnode;
-	return nb_node->cbs.pre_validate(&args);
+	args.errmsg = errmsg;
+	args.errmsg_len = errmsg_len;
+	ret = nb_node->cbs.pre_validate(&args);
+
+	/* Detect and log unexpected errors. */
+	switch (ret) {
+	case NB_OK:
+	case NB_ERR_VALIDATION:
+		break;
+	default:
+		unexpected_error = true;
+		break;
+	}
+	if (unexpected_error)
+		DEBUGD(&nb_dbg_cbs_config,
+		       "northbound callback: unexpected return value: %s",
+		       nb_err_name(ret));
+
+	return ret;
 }
 
-static void nb_callback_apply_finish(const struct nb_node *nb_node,
-				     const struct lyd_node *dnode)
+static void nb_callback_apply_finish(struct nb_context *context,
+				     const struct nb_node *nb_node,
+				     const struct lyd_node *dnode, char *errmsg,
+				     size_t errmsg_len)
 {
 	struct nb_cb_apply_finish_args args = {};
 
 	nb_log_config_callback(NB_EV_APPLY, NB_OP_APPLY_FINISH, dnode);
 
+	args.context = context;
 	args.dnode = dnode;
+	args.errmsg = errmsg;
+	args.errmsg_len = errmsg_len;
 	nb_node->cbs.apply_finish(&args);
 }
 
@@ -953,8 +1141,10 @@ int nb_callback_rpc(const struct nb_node *nb_node, const char *xpath,
  * Call the northbound configuration callback associated to a given
  * configuration change.
  */
-static int nb_callback_configuration(const enum nb_event event,
-				     struct nb_config_change *change)
+static int nb_callback_configuration(struct nb_context *context,
+				     const enum nb_event event,
+				     struct nb_config_change *change,
+				     char *errmsg, size_t errmsg_len)
 {
 	enum nb_operation operation = change->cb.operation;
 	char xpath[XPATH_MAXLEN];
@@ -963,7 +1153,6 @@ static int nb_callback_configuration(const enum nb_event event,
 	union nb_resource *resource;
 	int ret = NB_ERR;
 
-
 	if (event == NB_EV_VALIDATE)
 		resource = NULL;
 	else
@@ -971,16 +1160,20 @@ static int nb_callback_configuration(const enum nb_event event,
 
 	switch (operation) {
 	case NB_OP_CREATE:
-		ret = nb_callback_create(nb_node, event, dnode, resource);
+		ret = nb_callback_create(context, nb_node, event, dnode,
+					 resource, errmsg, errmsg_len);
 		break;
 	case NB_OP_MODIFY:
-		ret = nb_callback_modify(nb_node, event, dnode, resource);
+		ret = nb_callback_modify(context, nb_node, event, dnode,
+					 resource, errmsg, errmsg_len);
 		break;
 	case NB_OP_DESTROY:
-		ret = nb_callback_destroy(nb_node, event, dnode);
+		ret = nb_callback_destroy(context, nb_node, event, dnode,
+					  errmsg, errmsg_len);
 		break;
 	case NB_OP_MOVE:
-		ret = nb_callback_move(nb_node, event, dnode);
+		ret = nb_callback_move(context, nb_node, event, dnode, errmsg,
+				       errmsg_len);
 		break;
 	default:
 		yang_dnode_get_path(dnode, xpath, sizeof(xpath));
@@ -1015,45 +1208,48 @@ static int nb_callback_configuration(const enum nb_event event,
 			break;
 		default:
 			flog_err(EC_LIB_DEVELOPMENT,
-				 "%s: unknown event (%u) [xpath %s]",
-				 __func__, event, xpath);
+				 "%s: unknown event (%u) [xpath %s]", __func__,
+				 event, xpath);
 			exit(1);
 		}
 
 		flog(priority, ref,
-		     "%s: error processing configuration change: error [%s] event [%s] operation [%s] xpath [%s]",
-		     __func__, nb_err_name(ret), nb_event_name(event),
+		     "error processing configuration change: error [%s] event [%s] operation [%s] xpath [%s]",
+		     nb_err_name(ret), nb_event_name(event),
 		     nb_operation_name(operation), xpath);
+		if (strlen(errmsg) > 0)
+			flog(priority, ref,
+			     "error processing configuration change: %s",
+			     errmsg);
 	}
 
 	return ret;
 }
 
 static struct nb_transaction *
-nb_transaction_new(struct nb_config *config, struct nb_config_cbs *changes,
-		   enum nb_client client, const void *user, const char *comment)
+nb_transaction_new(struct nb_context *context, struct nb_config *config,
+		   struct nb_config_cbs *changes, const char *comment,
+		   char *errmsg, size_t errmsg_len)
 {
 	struct nb_transaction *transaction;
 
-	if (nb_running_lock_check(client, user)) {
-		flog_warn(
-			EC_LIB_NB_TRANSACTION_CREATION_FAILED,
-			"%s: running configuration is locked by another client",
-			__func__);
+	if (nb_running_lock_check(context->client, context->user)) {
+		strlcpy(errmsg,
+			"running configuration is locked by another client",
+			errmsg_len);
 		return NULL;
 	}
 
 	if (transaction_in_progress) {
-		flog_warn(
-			EC_LIB_NB_TRANSACTION_CREATION_FAILED,
-			"%s: error - there's already another transaction in progress",
-			__func__);
+		strlcpy(errmsg,
+			"there's already another transaction in progress",
+			errmsg_len);
 		return NULL;
 	}
 	transaction_in_progress = true;
 
 	transaction = XCALLOC(MTYPE_TMP, sizeof(*transaction));
-	transaction->client = client;
+	transaction->context = context;
 	if (comment)
 		strlcpy(transaction->comment, comment,
 			sizeof(transaction->comment));
@@ -1072,7 +1268,8 @@ static void nb_transaction_free(struct nb_transaction *transaction)
 
 /* Process all configuration changes associated to a transaction. */
 static int nb_transaction_process(enum nb_event event,
-				  struct nb_transaction *transaction)
+				  struct nb_transaction *transaction,
+				  char *errmsg, size_t errmsg_len)
 {
 	struct nb_config_cb *cb;
 
@@ -1088,7 +1285,8 @@ static int nb_transaction_process(enum nb_event event,
 			break;
 
 		/* Call the appropriate callback. */
-		ret = nb_callback_configuration(event, change);
+		ret = nb_callback_configuration(transaction->context, event,
+						change, errmsg, errmsg_len);
 		switch (event) {
 		case NB_EV_PREPARE:
 			if (ret != NB_OK)
@@ -1142,7 +1340,8 @@ nb_apply_finish_cb_find(struct nb_config_cbs *cbs,
 }
 
 /* Call the 'apply_finish' callbacks. */
-static void nb_transaction_apply_finish(struct nb_transaction *transaction)
+static void nb_transaction_apply_finish(struct nb_transaction *transaction,
+					char *errmsg, size_t errmsg_len)
 {
 	struct nb_config_cbs cbs;
 	struct nb_config_cb *cb;
@@ -1201,7 +1400,8 @@ static void nb_transaction_apply_finish(struct nb_transaction *transaction)
 
 	/* Call the 'apply_finish' callbacks, sorted by their priorities. */
 	RB_FOREACH (cb, nb_config_cbs, &cbs)
-		nb_callback_apply_finish(cb->nb_node, cb->dnode);
+		nb_callback_apply_finish(transaction->context, cb->nb_node,
+					 cb->dnode, errmsg, errmsg_len);
 
 	/* Release memory. */
 	while (!RB_EMPTY(nb_config_cbs, &cbs)) {
@@ -1939,7 +2139,7 @@ const char *nb_err_name(enum nb_error error)
 	case NB_ERR_LOCKED:
 		return "resource is locked";
 	case NB_ERR_VALIDATION:
-		return "validation error";
+		return "validation";
 	case NB_ERR_RESOURCE:
 		return "failed to allocate resource";
 	case NB_ERR_INCONSISTENCY:
diff --git a/lib/northbound.h b/lib/northbound.h
index 2a1beeabaa..bd57013f59 100644
--- a/lib/northbound.h
+++ b/lib/northbound.h
@@ -91,6 +91,9 @@ union nb_resource {
  */
 
 struct nb_cb_create_args {
+	/* Context of the configuration transaction. */
+	struct nb_context *context;
+
 	/*
 	 * The transaction phase. Refer to the documentation comments of
 	 * nb_event for more details.
@@ -107,9 +110,18 @@ struct nb_cb_create_args {
 	 * resource(s). It's set to NULL when the event is NB_EV_VALIDATE.
 	 */
 	union nb_resource *resource;
+
+	/* Buffer to store human-readable error message in case of error. */
+	char *errmsg;
+
+	/* Size of errmsg. */
+	size_t errmsg_len;
 };
 
 struct nb_cb_modify_args {
+	/* Context of the configuration transaction. */
+	struct nb_context *context;
+
 	/*
 	 * The transaction phase. Refer to the documentation comments of
 	 * nb_event for more details.
@@ -126,9 +138,18 @@ struct nb_cb_modify_args {
 	 * resource(s). It's set to NULL when the event is NB_EV_VALIDATE.
 	 */
 	union nb_resource *resource;
+
+	/* Buffer to store human-readable error message in case of error. */
+	char *errmsg;
+
+	/* Size of errmsg. */
+	size_t errmsg_len;
 };
 
 struct nb_cb_destroy_args {
+	/* Context of the configuration transaction. */
+	struct nb_context *context;
+
 	/*
 	 * The transaction phase. Refer to the documentation comments of
 	 * nb_event for more details.
@@ -137,9 +158,18 @@ struct nb_cb_destroy_args {
 
 	/* libyang data node that is being deleted. */
 	const struct lyd_node *dnode;
+
+	/* Buffer to store human-readable error message in case of error. */
+	char *errmsg;
+
+	/* Size of errmsg. */
+	size_t errmsg_len;
 };
 
 struct nb_cb_move_args {
+	/* Context of the configuration transaction. */
+	struct nb_context *context;
+
 	/*
 	 * The transaction phase. Refer to the documentation comments of
 	 * nb_event for more details.
@@ -148,16 +178,40 @@ struct nb_cb_move_args {
 
 	/* libyang data node that is being moved. */
 	const struct lyd_node *dnode;
+
+	/* Buffer to store human-readable error message in case of error. */
+	char *errmsg;
+
+	/* Size of errmsg. */
+	size_t errmsg_len;
 };
 
 struct nb_cb_pre_validate_args {
+	/* Context of the configuration transaction. */
+	struct nb_context *context;
+
 	/* libyang data node associated with the 'pre_validate' callback. */
 	const struct lyd_node *dnode;
+
+	/* Buffer to store human-readable error message in case of error. */
+	char *errmsg;
+
+	/* Size of errmsg. */
+	size_t errmsg_len;
 };
 
 struct nb_cb_apply_finish_args {
+	/* Context of the configuration transaction. */
+	struct nb_context *context;
+
 	/* libyang data node associated with the 'apply_finish' callback. */
 	const struct lyd_node *dnode;
+
+	/* Buffer to store human-readable error message in case of error. */
+	char *errmsg;
+
+	/* Size of errmsg. */
+	size_t errmsg_len;
 };
 
 struct nb_cb_get_elem_args {
@@ -305,6 +359,10 @@ struct nb_callbacks {
 	 * args
 	 *    Refer to the documentation comments of nb_cb_pre_validate_args for
 	 *    details.
+	 *
+	 * Returns:
+	 *    - NB_OK on success.
+	 *    - NB_ERR_VALIDATION when a validation error occurred.
 	 */
 	int (*pre_validate)(struct nb_cb_pre_validate_args *args);
 
@@ -538,6 +596,29 @@ enum nb_client {
 	NB_CLIENT_GRPC,
 };
 
+/* Northbound context. */
+struct nb_context {
+	/* Northbound client. */
+	enum nb_client client;
+
+	/* Northbound user (can be NULL). */
+	const void *user;
+
+	/* Client-specific data. */
+#if 0
+	union {
+		struct {
+		} cli;
+		struct {
+		} confd;
+		struct {
+		} sysrepo;
+		struct {
+		} grpc;
+	} client_data;
+#endif
+};
+
 /* Northbound configuration. */
 struct nb_config {
 	struct lyd_node *dnode;
@@ -564,7 +645,7 @@ struct nb_config_change {
 
 /* Northbound configuration transaction. */
 struct nb_transaction {
-	enum nb_client client;
+	struct nb_context *context;
 	char comment[80];
 	struct nb_config *config;
 	struct nb_config_cbs changes;
@@ -762,28 +843,36 @@ extern int nb_candidate_update(struct nb_config *candidate);
  * WARNING: the candidate can be modified as part of the validation process
  * (e.g. add default nodes).
  *
+ * context
+ *    Context of the northbound transaction.
+ *
  * candidate
  *    Candidate configuration to validate.
  *
+ * errmsg
+ *    Buffer to store human-readable error message in case of error.
+ *
+ * errmsg_len
+ *    Size of errmsg.
+ *
  * Returns:
  *    NB_OK on success, NB_ERR_VALIDATION otherwise.
  */
-extern int nb_candidate_validate(struct nb_config *candidate);
+extern int nb_candidate_validate(struct nb_context *context,
+				 struct nb_config *candidate, char *errmsg,
+				 size_t errmsg_len);
 
 /*
  * Create a new configuration transaction but do not commit it yet. Only
  * validate the candidate and prepare all resources required to apply the
  * configuration changes.
  *
+ * context
+ *    Context of the northbound transaction.
+ *
  * candidate
  *    Candidate configuration to commit.
  *
- * client
- *    Northbound client performing the commit.
- *
- * user
- *    Northbound user performing the commit (can be NULL).
- *
  * comment
  *    Optional comment describing the commit.
  *
@@ -793,6 +882,12 @@ extern int nb_candidate_validate(struct nb_config *candidate);
  *    nb_candidate_commit_abort() or committed using
  *    nb_candidate_commit_apply().
  *
+ * errmsg
+ *    Buffer to store human-readable error message in case of error.
+ *
+ * errmsg_len
+ *    Size of errmsg.
+ *
  * Returns:
  *    - NB_OK on success.
  *    - NB_ERR_NO_CHANGES when the candidate is identical to the running
@@ -803,10 +898,11 @@ extern int nb_candidate_validate(struct nb_config *candidate);
  *      the candidate configuration.
  *    - NB_ERR for other errors.
  */
-extern int nb_candidate_commit_prepare(struct nb_config *candidate,
-				       enum nb_client client, const void *user,
+extern int nb_candidate_commit_prepare(struct nb_context *context,
+				       struct nb_config *candidate,
 				       const char *comment,
-				       struct nb_transaction **transaction);
+				       struct nb_transaction **transaction,
+				       char *errmsg, size_t errmsg_len);
 
 /*
  * Abort a previously created configuration transaction, releasing all resources
@@ -842,16 +938,13 @@ extern void nb_candidate_commit_apply(struct nb_transaction *transaction,
  * take into account the results of the preparation phase of multiple managed
  * entities.
  *
+ * context
+ *    Context of the northbound transaction.
+ *
  * candidate
  *    Candidate configuration to commit. It's preserved regardless if the commit
  *    operation fails or not.
  *
- * client
- *    Northbound client performing the commit.
- *
- * user
- *    Northbound user performing the commit (can be NULL).
- *
  * save_transaction
  *    Specify whether the transaction should be recorded in the transactions log
  *    or not.
@@ -862,6 +955,12 @@ extern void nb_candidate_commit_apply(struct nb_transaction *transaction,
  * transaction_id
  *    Optional output parameter providing the ID of the committed transaction.
  *
+ * errmsg
+ *    Buffer to store human-readable error message in case of error.
+ *
+ * errmsg_len
+ *    Size of errmsg.
+ *
  * Returns:
  *    - NB_OK on success.
  *    - NB_ERR_NO_CHANGES when the candidate is identical to the running
@@ -872,10 +971,11 @@ extern void nb_candidate_commit_apply(struct nb_transaction *transaction,
  *      the candidate configuration.
  *    - NB_ERR for other errors.
  */
-extern int nb_candidate_commit(struct nb_config *candidate,
-			       enum nb_client client, const void *user,
+extern int nb_candidate_commit(struct nb_context *context,
+			       struct nb_config *candidate,
 			       bool save_transaction, const char *comment,
-			       uint32_t *transaction_id);
+			       uint32_t *transaction_id, char *errmsg,
+			       size_t errmsg_len);
 
 /*
  * Lock the running configuration.
@@ -1061,8 +1161,8 @@ extern void *nb_running_unset_entry(const struct lyd_node *dnode);
  * Returns:
  *    User pointer if found, NULL otherwise.
  */
-extern void *nb_running_get_entry(const struct lyd_node *dnode, const char *xpath,
-				  bool abort_if_not_found);
+extern void *nb_running_get_entry(const struct lyd_node *dnode,
+				  const char *xpath, bool abort_if_not_found);
 
 /*
  * Return a human-readable string representing a northbound event.
diff --git a/lib/northbound_cli.c b/lib/northbound_cli.c
index d4467facaf..105fc83cef 100644
--- a/lib/northbound_cli.c
+++ b/lib/northbound_cli.c
@@ -46,23 +46,11 @@ struct debug nb_dbg_libyang = {0, "libyang debugging"};
 struct nb_config *vty_shared_candidate_config;
 static struct thread_master *master;
 
-static void vty_show_libyang_errors(struct vty *vty, struct ly_ctx *ly_ctx)
+static void vty_show_nb_errors(struct vty *vty, int error, const char *errmsg)
 {
-	struct ly_err_item *ei;
-	const char *path;
-
-	ei = ly_err_first(ly_ctx);
-	if (!ei)
-		return;
-
-	for (; ei; ei = ei->next)
-		vty_out(vty, "%s\n", ei->msg);
-
-	path = ly_errpath(ly_ctx);
-	if (path)
-		vty_out(vty, "YANG path: %s\n", path);
-
-	ly_err_clean(ly_ctx, NULL);
+	vty_out(vty, "Error type: %s\n", nb_err_name(error));
+	if (strlen(errmsg) > 0)
+		vty_out(vty, "Error description: %s\n", errmsg);
 }
 
 void nb_cli_enqueue_change(struct vty *vty, const char *xpath,
@@ -158,24 +146,31 @@ int nb_cli_apply_changes(struct vty *vty, const char *xpath_base_fmt, ...)
 	}
 
 	if (error) {
+		char buf[BUFSIZ];
+
 		/*
 		 * Failure to edit the candidate configuration should never
 		 * happen in practice, unless there's a bug in the code. When
 		 * that happens, log the error but otherwise ignore it.
 		 */
 		vty_out(vty, "%% Failed to edit configuration.\n\n");
-		vty_show_libyang_errors(vty, ly_native_ctx);
+		vty_out(vty, "%s",
+			yang_print_errors(ly_native_ctx, buf, sizeof(buf)));
 	}
 
 	/* Do an implicit "commit" when using the classic CLI mode. */
 	if (frr_get_cli_mode() == FRR_CLI_CLASSIC) {
-		ret = nb_candidate_commit(vty->candidate_config, NB_CLIENT_CLI,
-					  vty, false, NULL, NULL);
+		struct nb_context context = {};
+		char errmsg[BUFSIZ] = {0};
+
+		context.client = NB_CLIENT_CLI;
+		context.user = vty;
+		ret = nb_candidate_commit(&context, vty->candidate_config,
+					  false, NULL, NULL, errmsg,
+					  sizeof(errmsg));
 		if (ret != NB_OK && ret != NB_ERR_NO_CHANGES) {
-			vty_out(vty, "%% Configuration failed: %s.\n\n",
-				nb_err_name(ret));
-			vty_out(vty,
-				"Please check the logs for more details.\n");
+			vty_out(vty, "%% Configuration failed.\n\n");
+			vty_show_nb_errors(vty, ret, errmsg);
 
 			/* Regenerate candidate for consistency. */
 			nb_config_replace(vty->candidate_config, running_config,
@@ -217,20 +212,27 @@ void nb_cli_confirmed_commit_clean(struct vty *vty)
 
 int nb_cli_confirmed_commit_rollback(struct vty *vty)
 {
+	struct nb_context context = {};
 	uint32_t transaction_id;
+	char errmsg[BUFSIZ] = {0};
 	int ret;
 
 	/* Perform the rollback. */
+	context.client = NB_CLIENT_CLI;
+	context.user = vty;
 	ret = nb_candidate_commit(
-		vty->confirmed_commit_rollback, NB_CLIENT_CLI, vty, true,
+		&context, vty->confirmed_commit_rollback, true,
 		"Rollback to previous configuration - confirmed commit has timed out",
-		&transaction_id);
+		&transaction_id, errmsg, sizeof(errmsg));
 	if (ret == NB_OK)
 		vty_out(vty,
 			"Rollback performed successfully (Transaction ID #%u).\n",
 			transaction_id);
-	else
-		vty_out(vty, "Failed to rollback to previous configuration.\n");
+	else {
+		vty_out(vty,
+			"Failed to rollback to previous configuration.\n\n");
+		vty_show_nb_errors(vty, ret, errmsg);
+	}
 
 	return ret;
 }
@@ -252,7 +254,9 @@ static int nb_cli_confirmed_commit_timeout(struct thread *thread)
 static int nb_cli_commit(struct vty *vty, bool force,
 			 unsigned int confirmed_timeout, char *comment)
 {
+	struct nb_context context = {};
 	uint32_t transaction_id = 0;
+	char errmsg[BUFSIZ] = {0};
 	int ret;
 
 	/* Check if there's a pending confirmed commit. */
@@ -295,8 +299,11 @@ static int nb_cli_commit(struct vty *vty, bool force,
 				 &vty->t_confirmed_commit_timeout);
 	}
 
-	ret = nb_candidate_commit(vty->candidate_config, NB_CLIENT_CLI, vty,
-				  true, comment, &transaction_id);
+	context.client = NB_CLIENT_CLI;
+	context.user = vty;
+	ret = nb_candidate_commit(&context, vty->candidate_config, true,
+				  comment, &transaction_id, errmsg,
+				  sizeof(errmsg));
 
 	/* Map northbound return code to CLI return code. */
 	switch (ret) {
@@ -312,9 +319,8 @@ static int nb_cli_commit(struct vty *vty, bool force,
 		return CMD_SUCCESS;
 	default:
 		vty_out(vty,
-			"%% Failed to commit candidate configuration: %s.\n\n",
-			nb_err_name(ret));
-		vty_out(vty, "Please check the logs for more details.\n");
+			"%% Failed to commit candidate configuration.\n\n");
+		vty_show_nb_errors(vty, ret, errmsg);
 		return CMD_WARNING;
 	}
 }
@@ -328,6 +334,7 @@ static int nb_cli_candidate_load_file(struct vty *vty,
 	struct lyd_node *dnode;
 	struct ly_ctx *ly_ctx;
 	int ly_format;
+	char buf[BUFSIZ];
 
 	switch (format) {
 	case NB_CFG_FMT_CMDS:
@@ -350,7 +357,9 @@ static int nb_cli_candidate_load_file(struct vty *vty,
 			flog_warn(EC_LIB_LIBYANG, "%s: lyd_parse_path() failed",
 				  __func__);
 			vty_out(vty, "%% Failed to load configuration:\n\n");
-			vty_show_libyang_errors(vty, ly_ctx);
+			vty_out(vty, "%s",
+				yang_print_errors(ly_native_ctx, buf,
+						  sizeof(buf)));
 			return CMD_WARNING;
 		}
 		if (translator
@@ -371,7 +380,8 @@ static int nb_cli_candidate_load_file(struct vty *vty,
 		 != NB_OK) {
 		vty_out(vty,
 			"%% Failed to merge the loaded configuration:\n\n");
-		vty_show_libyang_errors(vty, ly_native_ctx);
+		vty_out(vty, "%s",
+			yang_print_errors(ly_native_ctx, buf, sizeof(buf)));
 		return CMD_WARNING;
 	}
 
@@ -383,6 +393,7 @@ static int nb_cli_candidate_load_transaction(struct vty *vty,
 					     bool replace)
 {
 	struct nb_config *loaded_config;
+	char buf[BUFSIZ];
 
 	loaded_config = nb_db_transaction_load(transaction_id);
 	if (!loaded_config) {
@@ -397,7 +408,8 @@ static int nb_cli_candidate_load_transaction(struct vty *vty,
 		 != NB_OK) {
 		vty_out(vty,
 			"%% Failed to merge the loaded configuration:\n\n");
-		vty_show_libyang_errors(vty, ly_native_ctx);
+		vty_out(vty, "%s",
+			yang_print_errors(ly_native_ctx, buf, sizeof(buf)));
 		return CMD_WARNING;
 	}
 
@@ -690,13 +702,18 @@ DEFPY (config_commit_check,
        "Commit changes into the running configuration\n"
        "Check if the configuration changes are valid\n")
 {
+	struct nb_context context = {};
+	char errmsg[BUFSIZ] = {0};
 	int ret;
 
-	ret = nb_candidate_validate(vty->candidate_config);
+	context.client = NB_CLIENT_CLI;
+	context.user = vty;
+	ret = nb_candidate_validate(&context, vty->candidate_config, errmsg,
+				    sizeof(errmsg));
 	if (ret != NB_OK) {
 		vty_out(vty,
 			"%% Failed to validate candidate configuration.\n\n");
-		vty_show_libyang_errors(vty, ly_native_ctx);
+		vty_show_nb_errors(vty, ret, errmsg);
 		return CMD_WARNING;
 	}
 
@@ -1530,8 +1547,10 @@ DEFPY (show_yang_module_translator,
 static int nb_cli_rollback_configuration(struct vty *vty,
 					 uint32_t transaction_id)
 {
+	struct nb_context context = {};
 	struct nb_config *candidate;
 	char comment[80];
+	char errmsg[BUFSIZ] = {0};
 	int ret;
 
 	candidate = nb_db_transaction_load(transaction_id);
@@ -1544,8 +1563,10 @@ static int nb_cli_rollback_configuration(struct vty *vty,
 	snprintf(comment, sizeof(comment), "Rollback to transaction %u",
 		 transaction_id);
 
-	ret = nb_candidate_commit(candidate, NB_CLIENT_CLI, vty, true, comment,
-				  NULL);
+	context.client = NB_CLIENT_CLI;
+	context.user = vty;
+	ret = nb_candidate_commit(&context, candidate, true, comment, NULL,
+				  errmsg, sizeof(errmsg));
 	nb_config_free(candidate);
 	switch (ret) {
 	case NB_OK:
@@ -1558,7 +1579,7 @@ static int nb_cli_rollback_configuration(struct vty *vty,
 		return CMD_WARNING;
 	default:
 		vty_out(vty, "%% Rollback failed.\n\n");
-		vty_out(vty, "Please check the logs for more details.\n");
+		vty_show_nb_errors(vty, ret, errmsg);
 		return CMD_WARNING;
 	}
 }
diff --git a/lib/northbound_confd.c b/lib/northbound_confd.c
index 2fc3c81cf2..a3aaf02f08 100644
--- a/lib/northbound_confd.c
+++ b/lib/northbound_confd.c
@@ -285,8 +285,10 @@ frr_confd_cdb_diff_iter(confd_hkeypath_t *kp, enum cdb_iter_op cdb_op,
 
 static int frr_confd_cdb_read_cb_prepare(int fd, int *subp, int reslen)
 {
+	struct nb_context context = {};
 	struct nb_config *candidate;
 	struct cdb_iter_args iter_args;
+	char errmsg[BUFSIZ] = {0};
 	int ret;
 
 	candidate = nb_config_dup(running_config);
@@ -321,24 +323,21 @@ static int frr_confd_cdb_read_cb_prepare(int fd, int *subp, int reslen)
 	 * required to apply them.
 	 */
 	transaction = NULL;
-	ret = nb_candidate_commit_prepare(candidate, NB_CLIENT_CONFD, NULL,
-					  NULL, &transaction);
+	context.client = NB_CLIENT_CONFD;
+	ret = nb_candidate_commit_prepare(&context, candidate, NULL,
+					  &transaction, errmsg, sizeof(errmsg));
 	if (ret != NB_OK && ret != NB_ERR_NO_CHANGES) {
 		enum confd_errcode errcode;
-		const char *errmsg;
 
 		switch (ret) {
 		case NB_ERR_LOCKED:
 			errcode = CONFD_ERRCODE_IN_USE;
-			errmsg = "Configuration is locked by another process";
 			break;
 		case NB_ERR_RESOURCE:
 			errcode = CONFD_ERRCODE_RESOURCE_DENIED;
-			errmsg = "Failed do allocate resources";
 			break;
 		default:
-			errcode = CONFD_ERRCODE_INTERNAL;
-			errmsg = "Internal error";
+			errcode = CONFD_ERRCODE_APPLICATION;
 			break;
 		}
 
@@ -612,7 +611,7 @@ static int frr_confd_data_get_elem(struct confd_trans_ctx *tctx,
 				   confd_hkeypath_t *kp)
 {
 	struct nb_node *nb_node;
-	char xpath[BUFSIZ];
+	char xpath[XPATH_MAXLEN];
 	struct yang_data *data;
 	confd_value_t v;
 	const void *list_entry = NULL;
@@ -650,7 +649,7 @@ static int frr_confd_data_get_next(struct confd_trans_ctx *tctx,
 				   confd_hkeypath_t *kp, long next)
 {
 	struct nb_node *nb_node;
-	char xpath[BUFSIZ];
+	char xpath[XPATH_MAXLEN];
 	struct yang_data *data;
 	const void *parent_list_entry, *nb_next;
 	confd_value_t v[LIST_MAXKEYS];
@@ -758,8 +757,8 @@ static int frr_confd_data_get_object(struct confd_trans_ctx *tctx,
 {
 	struct nb_node *nb_node;
 	const struct lys_node *child;
-	char xpath[BUFSIZ];
-	char xpath_child[XPATH_MAXLEN];
+	char xpath[XPATH_MAXLEN];
+	char xpath_child[XPATH_MAXLEN * 2];
 	struct list *elements;
 	struct yang_data *data;
 	const void *list_entry;
@@ -832,7 +831,7 @@ static int frr_confd_data_get_object(struct confd_trans_ctx *tctx,
 static int frr_confd_data_get_next_object(struct confd_trans_ctx *tctx,
 					  confd_hkeypath_t *kp, long next)
 {
-	char xpath[BUFSIZ];
+	char xpath[XPATH_MAXLEN];
 	struct nb_node *nb_node;
 	struct list *elements;
 	const void *parent_list_entry;
@@ -916,7 +915,7 @@ static int frr_confd_data_get_next_object(struct confd_trans_ctx *tctx,
 		/* Loop through list child nodes. */
 		LY_TREE_FOR (nb_node->snode->child, child) {
 			struct nb_node *nb_node_child = child->priv;
-			char xpath_child[XPATH_MAXLEN];
+			char xpath_child[XPATH_MAXLEN * 2];
 			confd_value_t *v;
 
 			if (nvalues > CONFD_MAX_CHILD_NODES)
@@ -1059,7 +1058,7 @@ static int frr_confd_action_execute(struct confd_user_info *uinfo,
 				    struct xml_tag *name, confd_hkeypath_t *kp,
 				    confd_tag_value_t *params, int nparams)
 {
-	char xpath[BUFSIZ];
+	char xpath[XPATH_MAXLEN];
 	struct nb_node *nb_node;
 	struct list *input;
 	struct list *output;
@@ -1091,7 +1090,7 @@ static int frr_confd_action_execute(struct confd_user_info *uinfo,
 
 	/* Process input nodes. */
 	for (int i = 0; i < nparams; i++) {
-		char xpath_input[BUFSIZ];
+		char xpath_input[XPATH_MAXLEN * 2];
 		char value_str[YANG_VALUE_MAXLEN];
 
 		snprintf(xpath_input, sizeof(xpath_input), "%s/%s", xpath,
diff --git a/lib/northbound_db.c b/lib/northbound_db.c
index 598805b961..244e760b2b 100644
--- a/lib/northbound_db.c
+++ b/lib/northbound_db.c
@@ -86,7 +86,7 @@ int nb_db_transaction_save(const struct nb_transaction *transaction,
 	if (!ss)
 		goto exit;
 
-	client_name = nb_client_name(transaction->client);
+	client_name = nb_client_name(transaction->context->client);
 	/* Always record configurations in the XML format. */
 	if (lyd_print_mem(&config_str, transaction->config->dnode, LYD_XML,
 			  LYP_FORMAT | LYP_WITHSIBLINGS)
diff --git a/lib/northbound_grpc.cpp b/lib/northbound_grpc.cpp
index 2962a977eb..83d7e0ce95 100644
--- a/lib/northbound_grpc.cpp
+++ b/lib/northbound_grpc.cpp
@@ -175,14 +175,13 @@ class NorthboundImpl
 	void HandleGetCapabilities(RpcState<frr::GetCapabilitiesRequest,
 					    frr::GetCapabilitiesResponse> *tag)
 	{
-		if (nb_dbg_client_grpc)
-			zlog_debug("received RPC GetCapabilities()");
-
 		switch (tag->state) {
 		case CREATE:
 			REQUEST_RPC(GetCapabilities);
 			tag->state = PROCESS;
 		case PROCESS: {
+			if (nb_dbg_client_grpc)
+				zlog_debug("received RPC GetCapabilities()");
 
 			// Response: string frr_version = 1;
 			tag->response.set_frr_version(FRR_VERSION);
@@ -298,14 +297,14 @@ class NorthboundImpl
 	void HandleCreateCandidate(RpcState<frr::CreateCandidateRequest,
 					    frr::CreateCandidateResponse> *tag)
 	{
-		if (nb_dbg_client_grpc)
-			zlog_debug("received RPC CreateCandidate()");
-
 		switch (tag->state) {
 		case CREATE:
 			REQUEST_RPC(CreateCandidate);
 			tag->state = PROCESS;
 		case PROCESS: {
+			if (nb_dbg_client_grpc)
+				zlog_debug("received RPC CreateCandidate()");
+
 			struct candidate *candidate = create_candidate();
 			if (!candidate) {
 				tag->responder.Finish(
@@ -672,15 +671,22 @@ class NorthboundImpl
 
 
 			// Execute the user request.
+			struct nb_context context = {};
+			context.client = NB_CLIENT_GRPC;
+			char errmsg[BUFSIZ] = {0};
+
 			switch (phase) {
 			case frr::CommitRequest::VALIDATE:
-				ret = nb_candidate_validate(candidate->config);
+				ret = nb_candidate_validate(
+					&context, candidate->config, errmsg,
+					sizeof(errmsg));
 				break;
 			case frr::CommitRequest::PREPARE:
 				ret = nb_candidate_commit_prepare(
-					candidate->config, NB_CLIENT_GRPC, NULL,
+					&context, candidate->config,
 					comment.c_str(),
-					&candidate->transaction);
+					&candidate->transaction, errmsg,
+					sizeof(errmsg));
 				break;
 			case frr::CommitRequest::ABORT:
 				nb_candidate_commit_abort(
@@ -693,71 +699,51 @@ class NorthboundImpl
 				break;
 			case frr::CommitRequest::ALL:
 				ret = nb_candidate_commit(
-					candidate->config, NB_CLIENT_GRPC, NULL,
-					true, comment.c_str(), &transaction_id);
+					&context, candidate->config, true,
+					comment.c_str(), &transaction_id,
+					errmsg, sizeof(errmsg));
 				break;
 			}
 
-			// Map northbound error codes to gRPC error codes.
+			// Map northbound error codes to gRPC status codes.
+			grpc::Status status;
 			switch (ret) {
+			case NB_OK:
+				status = grpc::Status::OK;
+				break;
 			case NB_ERR_NO_CHANGES:
-				tag->responder.Finish(
-					tag->response,
-					grpc::Status(
-						grpc::StatusCode::ABORTED,
-						"No configuration changes detected"),
-					tag);
-				tag->state = FINISH;
-				return;
+				status = grpc::Status(grpc::StatusCode::ABORTED,
+						      errmsg);
+				break;
 			case NB_ERR_LOCKED:
-				tag->responder.Finish(
-					tag->response,
-					grpc::Status(
-						grpc::StatusCode::UNAVAILABLE,
-						"There's already a transaction in progress"),
-					tag);
-				tag->state = FINISH;
-				return;
+				status = grpc::Status(
+					grpc::StatusCode::UNAVAILABLE, errmsg);
+				break;
 			case NB_ERR_VALIDATION:
-				tag->responder.Finish(
-					tag->response,
-					grpc::Status(grpc::StatusCode::
-							     INVALID_ARGUMENT,
-						     "Validation error"),
-					tag);
-				tag->state = FINISH;
-				return;
+				status = grpc::Status(
+					grpc::StatusCode::INVALID_ARGUMENT,
+					errmsg);
+				break;
 			case NB_ERR_RESOURCE:
-				tag->responder.Finish(
-					tag->response,
-					grpc::Status(
-						grpc::StatusCode::
-							RESOURCE_EXHAUSTED,
-						"Failed do allocate resources"),
-					tag);
-				tag->state = FINISH;
-				return;
+				status = grpc::Status(
+					grpc::StatusCode::RESOURCE_EXHAUSTED,
+					errmsg);
+				break;
 			case NB_ERR:
-				tag->responder.Finish(
-					tag->response,
-					grpc::Status(grpc::StatusCode::INTERNAL,
-						     "Internal error"),
-					tag);
-				tag->state = FINISH;
-				return;
 			default:
+				status = grpc::Status(
+					grpc::StatusCode::INTERNAL, errmsg);
 				break;
 			}
+			if (ret == NB_OK) {
+				// Response: uint32 transaction_id = 1;
+				if (transaction_id)
+					tag->response.set_transaction_id(
+						transaction_id);
+			}
 
-			// Response: uint32 transaction_id = 1;
-			if (transaction_id)
-				tag->response.set_transaction_id(
-					transaction_id);
-
-			tag->responder.Finish(tag->response, grpc::Status::OK,
-					      tag);
+			tag->responder.Finish(tag->response, status, tag);
 			tag->state = FINISH;
-
 			break;
 		}
 		case FINISH:
@@ -769,9 +755,6 @@ class NorthboundImpl
 	HandleListTransactions(RpcState<frr::ListTransactionsRequest,
 					frr::ListTransactionsResponse> *tag)
 	{
-		if (nb_dbg_client_grpc)
-			zlog_debug("received RPC ListTransactions()");
-
 		switch (tag->state) {
 		case CREATE:
 			REQUEST_RPC_STREAMING(ListTransactions);
@@ -781,6 +764,9 @@ class NorthboundImpl
 						   tag->context);
 			tag->state = PROCESS;
 		case PROCESS: {
+			if (nb_dbg_client_grpc)
+				zlog_debug("received RPC ListTransactions()");
+
 			auto list = static_cast<std::list<std::tuple<
 				int, std::string, std::string, std::string>> *>(
 				tag->context);
@@ -889,14 +875,14 @@ class NorthboundImpl
 	void HandleLockConfig(
 		RpcState<frr::LockConfigRequest, frr::LockConfigResponse> *tag)
 	{
-		if (nb_dbg_client_grpc)
-			zlog_debug("received RPC LockConfig()");
-
 		switch (tag->state) {
 		case CREATE:
 			REQUEST_RPC(LockConfig);
 			tag->state = PROCESS;
 		case PROCESS: {
+			if (nb_dbg_client_grpc)
+				zlog_debug("received RPC LockConfig()");
+
 			if (nb_running_lock(NB_CLIENT_GRPC, NULL)) {
 				tag->responder.Finish(
 					tag->response,
@@ -922,14 +908,14 @@ class NorthboundImpl
 	void HandleUnlockConfig(RpcState<frr::UnlockConfigRequest,
 					 frr::UnlockConfigResponse> *tag)
 	{
-		if (nb_dbg_client_grpc)
-			zlog_debug("received RPC UnlockConfig()");
-
 		switch (tag->state) {
 		case CREATE:
 			REQUEST_RPC(UnlockConfig);
 			tag->state = PROCESS;
 		case PROCESS: {
+			if (nb_dbg_client_grpc)
+				zlog_debug("received RPC UnlockConfig()");
+
 			if (nb_running_unlock(NB_CLIENT_GRPC, NULL)) {
 				tag->responder.Finish(
 					tag->response,
diff --git a/lib/northbound_sysrepo.c b/lib/northbound_sysrepo.c
index b94c939763..500203173c 100644
--- a/lib/northbound_sysrepo.c
+++ b/lib/northbound_sysrepo.c
@@ -245,7 +245,9 @@ static int frr_sr_config_change_cb_verify(sr_session_ctx_t *session,
 	sr_change_oper_t sr_op;
 	sr_val_t *sr_old_val, *sr_new_val;
 	char xpath[XPATH_MAXLEN];
+	struct nb_context context = {};
 	struct nb_config *candidate;
+	char errmsg[BUFSIZ] = {0};
 
 	snprintf(xpath, sizeof(xpath), "/%s:*", module_name);
 	ret = sr_get_changes_iter(session, xpath, &it);
@@ -276,21 +278,33 @@ static int frr_sr_config_change_cb_verify(sr_session_ctx_t *session,
 	}
 
 	transaction = NULL;
+	context.client = NB_CLIENT_SYSREPO;
 	if (startup_config) {
 		/*
 		 * sysrepod sends the entire startup configuration using a
 		 * single event (SR_EV_ENABLED). This means we need to perform
 		 * the full two-phase commit protocol in one go here.
 		 */
-		ret = nb_candidate_commit(candidate, NB_CLIENT_SYSREPO, NULL,
-					  true, NULL, NULL);
+		ret = nb_candidate_commit(&context, candidate, true, NULL, NULL,
+					  errmsg, sizeof(errmsg));
+		if (ret != NB_OK && ret != NB_ERR_NO_CHANGES)
+			flog_warn(
+				EC_LIB_LIBSYSREPO,
+				"%s: failed to apply startup configuration: %s (%s)",
+				__func__, nb_err_name(ret), errmsg);
 	} else {
 		/*
 		 * Validate the configuration changes and allocate all resources
 		 * required to apply them.
 		 */
-		ret = nb_candidate_commit_prepare(candidate, NB_CLIENT_SYSREPO,
-						  NULL, NULL, &transaction);
+		ret = nb_candidate_commit_prepare(&context, candidate, NULL,
+						  &transaction, errmsg,
+						  sizeof(errmsg));
+		if (ret != NB_OK && ret != NB_ERR_NO_CHANGES)
+			flog_warn(
+				EC_LIB_LIBSYSREPO,
+				"%s: failed to prepare configuration transaction: %s (%s)",
+				__func__, nb_err_name(ret), errmsg);
 	}
 
 	/* Map northbound return code to sysrepo return code. */
diff --git a/lib/vrf.c b/lib/vrf.c
index 9df5d19516..fb64589287 100644
--- a/lib/vrf.c
+++ b/lib/vrf.c
@@ -1082,8 +1082,8 @@ static int lib_vrf_destroy(struct nb_cb_destroy_args *args)
 	case NB_EV_VALIDATE:
 		vrfp = nb_running_get_entry(args->dnode, NULL, true);
 		if (CHECK_FLAG(vrfp->status, VRF_ACTIVE)) {
-			zlog_debug("%s Only inactive VRFs can be deleted",
-				   __func__);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "Only inactive VRFs can be deleted");
 			return NB_ERR_VALIDATION;
 		}
 		break;
diff --git a/lib/vty.c b/lib/vty.c
index 784f9cf2ac..ffef05e4dc 100644
--- a/lib/vty.c
+++ b/lib/vty.c
@@ -2349,12 +2349,18 @@ static void vty_read_file(struct nb_config *config, FILE *confp)
 	 * reading the configuration file.
 	 */
 	if (config == NULL) {
-		ret = nb_candidate_commit(vty->candidate_config, NB_CLIENT_CLI,
-					  vty, true, "Read configuration file",
-					  NULL);
+		struct nb_context context = {};
+		char errmsg[BUFSIZ] = {0};
+
+		context.client = NB_CLIENT_CLI;
+		context.user = vty;
+		ret = nb_candidate_commit(&context, vty->candidate_config, true,
+					  "Read configuration file", NULL,
+					  errmsg, sizeof(errmsg));
 		if (ret != NB_OK && ret != NB_ERR_NO_CHANGES)
-			zlog_err("%s: failed to read configuration file.",
-				 __func__);
+			zlog_err(
+				"%s: failed to read configuration file: %s (%s)",
+				__func__, nb_err_name(ret), errmsg);
 	}
 
 	vty_close(vty);
diff --git a/lib/vty.h b/lib/vty.h
index 694aac3944..5d5676199b 100644
--- a/lib/vty.h
+++ b/lib/vty.h
@@ -43,7 +43,7 @@ extern "C" {
 #define VTY_MAXHIST 20
 #define VTY_MAXDEPTH 8
 
-#define VTY_MAXCFGCHANGES 8
+#define VTY_MAXCFGCHANGES 16
 
 struct vty_error {
 	char error_buf[VTY_BUFSIZ];
diff --git a/lib/yang.c b/lib/yang.c
index 7ac39f4182..0714ddf7bb 100644
--- a/lib/yang.c
+++ b/lib/yang.c
@@ -647,6 +647,34 @@ static void ly_log_cb(LY_LOG_LEVEL level, const char *msg, const char *path)
 		zlog(priority, "libyang: %s", msg);
 }
 
+const char *yang_print_errors(struct ly_ctx *ly_ctx, char *buf, size_t buf_len)
+{
+	struct ly_err_item *ei;
+	const char *path;
+
+	ei = ly_err_first(ly_ctx);
+	if (!ei)
+		return "";
+
+	strlcpy(buf, "YANG error(s):\n", buf_len);
+	for (; ei; ei = ei->next) {
+		strlcat(buf, " ", buf_len);
+		strlcat(buf, ei->msg, buf_len);
+		strlcat(buf, "\n", buf_len);
+	}
+
+	path = ly_errpath(ly_ctx);
+	if (path) {
+		strlcat(buf, " YANG path: ", buf_len);
+		strlcat(buf, path, buf_len);
+		strlcat(buf, "\n", buf_len);
+	}
+
+	ly_err_clean(ly_ctx, NULL);
+
+	return buf;
+}
+
 void yang_debugging_set(bool enable)
 {
 	if (enable) {
diff --git a/lib/yang.h b/lib/yang.h
index 3be0fe5383..85ef0d758c 100644
--- a/lib/yang.h
+++ b/lib/yang.h
@@ -519,6 +519,24 @@ extern struct ly_ctx *yang_ctx_new_setup(bool embedded_modules);
 extern void yang_debugging_set(bool enable);
 
 /*
+ * Print libyang error messages into the provided buffer.
+ *
+ * ly_ctx
+ *    libyang context to operate on.
+ *
+ * buf
+ *    Buffer to store the libyang error messages.
+ *
+ * buf_len
+ *    Size of buf.
+ *
+ * Returns:
+ *    The provided buffer.
+ */
+extern const char *yang_print_errors(struct ly_ctx *ly_ctx, char *buf,
+				     size_t buf_len);
+
+/*
  * Initialize the YANG subsystem. Should be called only once during the
  * daemon initialization process.
  *
diff --git a/zebra/zebra_nb_config.c b/zebra/zebra_nb_config.c
index 5b87a18a06..948ef51320 100644
--- a/zebra/zebra_nb_config.c
+++ b/zebra/zebra_nb_config.c
@@ -941,13 +941,15 @@ int lib_interface_zebra_ip_addrs_create(struct nb_cb_create_args *args)
 	case NB_EV_VALIDATE:
 		if (prefix.family == AF_INET
 		    && ipv4_martian(&prefix.u.prefix4)) {
-			zlog_debug("invalid address %s",
-				   prefix2str(&prefix, buf, sizeof(buf)));
+			snprintf(args->errmsg, args->errmsg_len,
+				 "invalid address %s",
+				 prefix2str(&prefix, buf, sizeof(buf)));
 			return NB_ERR_VALIDATION;
 		} else if (prefix.family == AF_INET6
 			   && ipv6_martian(&prefix.u.prefix6)) {
-			zlog_debug("invalid address %s",
-				   prefix2str(&prefix, buf, sizeof(buf)));
+			snprintf(args->errmsg, args->errmsg_len,
+				 "invalid address %s",
+				 prefix2str(&prefix, buf, sizeof(buf)));
 			return NB_ERR_VALIDATION;
 		}
 		break;
@@ -982,16 +984,18 @@ int lib_interface_zebra_ip_addrs_destroy(struct nb_cb_destroy_args *args)
 			/* Check current interface address. */
 			ifc = connected_check_ptp(ifp, &prefix, NULL);
 			if (!ifc) {
-				zlog_debug("interface %s Can't find address\n",
-					   ifp->name);
+				snprintf(args->errmsg, args->errmsg_len,
+					 "interface %s Can't find address\n",
+					 ifp->name);
 				return NB_ERR_VALIDATION;
 			}
 		} else if (prefix.family == AF_INET6) {
 			/* Check current interface address. */
 			ifc = connected_check(ifp, &prefix);
 			if (!ifc) {
-				zlog_debug("interface can't find address %s",
-					   ifp->name);
+				snprintf(args->errmsg, args->errmsg_len,
+					 "interface can't find address %s",
+					 ifp->name);
 				return NB_ERR_VALIDATION;
 			}
 		} else
@@ -999,7 +1003,8 @@ int lib_interface_zebra_ip_addrs_destroy(struct nb_cb_destroy_args *args)
 
 		/* This is not configured address. */
 		if (!CHECK_FLAG(ifc->conf, ZEBRA_IFC_CONFIGURED)) {
-			zlog_debug("interface %s not configured", ifp->name);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "interface %s not configured", ifp->name);
 			return NB_ERR_VALIDATION;
 		}
 
@@ -1244,8 +1249,8 @@ int lib_vrf_zebra_ribs_rib_create(struct nb_cb_create_args *args)
 	switch (args->event) {
 	case NB_EV_VALIDATE:
 		if (!zrt) {
-			zlog_debug("%s: vrf %s table is not found.", __func__,
-				   vrf->name);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "vrf %s table is not found.", vrf->name);
 			return NB_ERR_VALIDATION;
 		}
 		break;
@@ -1376,7 +1381,8 @@ int lib_route_map_entry_match_condition_source_protocol_modify(
 	case NB_EV_VALIDATE:
 		type = yang_dnode_get_string(args->dnode, NULL);
 		if (proto_name2num(type) == -1) {
-			zlog_warn("%s: invalid protocol: %s", __func__, type);
+			snprintf(args->errmsg, args->errmsg_len,
+				 "invalid protocol: %s", type);
 			return NB_ERR_VALIDATION;
 		}
 		return NB_OK;
@@ -1470,8 +1476,9 @@ int lib_route_map_entry_set_action_source_v4_modify(
 		memset(&p, 0, sizeof(p));
 		yang_dnode_get_ipv4p(&p, args->dnode, NULL);
 		if (zebra_check_addr(&p) == 0) {
-			zlog_warn("%s: invalid IPv4 address: %s", __func__,
-				  yang_dnode_get_string(args->dnode, NULL));
+			snprintf(args->errmsg, args->errmsg_len,
+				 "invalid IPv4 address: %s",
+				 yang_dnode_get_string(args->dnode, NULL));
 			return NB_ERR_VALIDATION;
 		}
 
@@ -1482,8 +1489,9 @@ int lib_route_map_entry_set_action_source_v4_modify(
 				break;
 		}
 		if (pif == NULL) {
-			zlog_warn("%s: is not a local adddress: %s", __func__,
-				  yang_dnode_get_string(args->dnode, NULL));
+			snprintf(args->errmsg, args->errmsg_len,
+				 "is not a local adddress: %s",
+				 yang_dnode_get_string(args->dnode, NULL));
 			return NB_ERR_VALIDATION;
 		}
 		return NB_OK;
@@ -1536,8 +1544,9 @@ int lib_route_map_entry_set_action_source_v6_modify(
 		memset(&p, 0, sizeof(p));
 		yang_dnode_get_ipv6p(&p, args->dnode, NULL);
 		if (zebra_check_addr(&p) == 0) {
-			zlog_warn("%s: invalid IPv6 address: %s", __func__,
-				  yang_dnode_get_string(args->dnode, NULL));
+			snprintf(args->errmsg, args->errmsg_len,
+				 "invalid IPv6 address: %s",
+				 yang_dnode_get_string(args->dnode, NULL));
 			return NB_ERR_VALIDATION;
 		}
 
@@ -1548,8 +1557,9 @@ int lib_route_map_entry_set_action_source_v6_modify(
 				break;
 		}
 		if (pif == NULL) {
-			zlog_warn("%s: is not a local adddress: %s", __func__,
-				  yang_dnode_get_string(args->dnode, NULL));
+			snprintf(args->errmsg, args->errmsg_len,
+				 "is not a local adddress: %s",
+				 yang_dnode_get_string(args->dnode, NULL));
 			return NB_ERR_VALIDATION;
 		}
 		return NB_OK;