confd: Add helper to ensure that required modules are loaded

Unfortunately, sysrepo considers it an error to load a module that is
already loaded, ruling out using `sr_install_modules`.

Therefore, provide `require_modules` instead, which ensures that a
given set of modules are loaded, or loads them otherwise.

src/confd/src/Makefile.am

@@ -7,4 +7,4 @@ plugin_LTLIBRARIES      = confd-plugin.la
 confd_plugin_la_CFLAGS  = $(augeas_CFLAGS) $(sysrepo_CFLAGS) $(CFLAGS)
 confd_plugin_la_LIBADD  = $(augeas_LIBS)   $(sysrepo_LIBS)
 confd_plugin_la_LDFLAGS = -module -avoid-version -shared
-confd_plugin_la_SOURCES = core.c core.h run.c ietf-system.c ietf-interfaces.c
+confd_plugin_la_SOURCES = core.c core.h run.c sr_ext.c sr_ext.h ietf-system.c ietf-interfaces.c

src/confd/src/sr_ext.c

@@ -0,0 +1,60 @@
+#include <libyang/libyang.h>
+
+#include "sr_ext.h"
+
+sr_error_t srx_require_module(sr_conn_ctx_t *conn,
+			      const struct srx_module_requirement *mr)
+{
+	sr_error_t err = SR_ERR_OK;
+	const struct ly_ctx *ly;
+	struct lys_module *mod;
+	const char **f;
+	char *path;
+
+	ly = sr_acquire_context(conn);
+	if (!ly)
+		return SR_ERR_INVAL_ARG;
+
+	mod = ly_ctx_get_module(ly, mr->name, mr->rev);
+	sr_release_context(conn);
+
+	if (mod && mod->implemented) {
+		if (!mr->features)
+			return SR_ERR_OK;
+
+		for (f = mr->features; *f; f++) {
+			switch (lys_feature_value(mod, *f)) {
+			case LY_SUCCESS:
+				continue;
+			case LY_ENOT:
+				err = sr_enable_module_feature(conn, mr->name, *f);
+				if (err)
+					return err;
+				break;
+			default:
+				return SR_ERR_UNSUPPORTED;
+			}
+		}
+	} else {
+		/* `search_dirs` argument is ignored by sysrepo 2.2.60,
+		 * so we supply the full path instead.
+		 */
+		asprintf(&path, "%s/%s%s%s.yang", mr->dir ? : "", mr->name,
+			 mr->rev ? "@" : "", mr->rev ? : "");
+		err = sr_install_module(conn, path, NULL, mr->features);
+		free(path);
+	}
+
+	return err;
+}
+
+sr_error_t srx_require_modules(sr_conn_ctx_t *conn,
+			       const struct srx_module_requirement *mrs)
+{
+	sr_error_t err = SR_ERR_OK;
+
+	for (; mrs->name && !err; mrs++)
+		err = srx_require_module(conn, mrs);
+
+	return err;
+}

src/confd/src/sr_ext.h

@@ -0,0 +1,18 @@
+#ifndef CONFD_SR_EXT_H_
+#define CONFD_SR_EXT_H_
+
+#include <sysrepo.h>
+
+struct srx_module_requirement {
+	const char *dir;
+	const char *name;
+	const char *rev;
+	const char **features;
+};
+
+sr_error_t srx_require_module(sr_conn_ctx_t *conn,
+			      const struct srx_module_requirement *mr);
+sr_error_t srx_require_modules(sr_conn_ctx_t *conn,
+			       const struct srx_module_requirement *mrs);
+
+#endif	/* CONFD_SR_EXT_H_ */