2 files changed, 67 insertions, 0 deletions
diff --git a/modules/extended_error/extended_error.c b/modules/extended_error/extended_error.c
new file mode 100644
index 0000000..db0ed57
--- /dev/null
+++ b/modules/extended_error/extended_error.c
@@ -0,0 +1,47 @@
+#include <libknot/rrtype/opt.h>
+
+#include "lib/module.h"
+#include "daemon/engine.h"
+
+static int extended_error_finalize(kr_layer_t *ctx) {
+	struct kr_request *req = ctx->req;
+	const knot_rrset_t *src_opt = req->qsource.packet->opt_rr;
+	const struct kr_extended_error *ede = &req->extended_error;
+
+	if (ede->info_code == KNOT_EDNS_EDE_NONE  /* no extended error */
+	    || src_opt == NULL  /* no EDNS in query */
+	    || kr_fails_assert(ede->info_code >= 0 && ede->info_code < UINT16_MAX)  /* info code out of range */
+	    || kr_fails_assert(req->answer->opt_rr)  /* sanity check - answer should have EDNS */
+	    ) {
+		return ctx->state;
+	}
+
+	const uint16_t info_code = (uint16_t)ede->info_code;
+	const size_t extra_len = ede->extra_text ? strlen(ede->extra_text) : 0;
+	uint8_t buf[sizeof(info_code) + extra_len];
+	knot_wire_write_u16(buf, info_code);
+	if (extra_len)
+		memcpy(buf + sizeof(info_code), ede->extra_text, extra_len);
+
+	if (knot_edns_add_option(req->answer->opt_rr, KNOT_EDNS_OPTION_EDE,
+				 sizeof(buf), buf, &req->pool) != KNOT_EOK) {
+		/* something went wrong and there is no way to salvage content of OPT RRset */
+		kr_log_req(req, 0, 0, EDE, "unable to add Extended Error option\n");
+		knot_rrset_clear(req->answer->opt_rr, &req->pool);
+	}
+
+	return ctx->state;
+}
+
+KR_EXPORT
+int extended_error_init(struct kr_module *module) {
+	static kr_layer_api_t layer = {
+		.answer_finalize = &extended_error_finalize,
+	};
+	layer.data = module;
+	module->layer = &layer;
+
+	return kr_ok();
+}
+
+KR_MODULE_EXPORT(extended_error)
diff --git a/modules/extended_error/meson.build b/modules/extended_error/meson.build
new file mode 100644
index 0000000..15a1772
--- /dev/null
+++ b/modules/extended_error/meson.build
@@ -0,0 +1,20 @@
+# C module: extended_error
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+extended_error_src = files([
+  'extended_error.c',
+])
+c_src_lint += extended_error_src
+
+extended_error_mod = shared_module(
+  'extended_error',
+  extended_error_src,
+  dependencies: [
+    libknot,
+  ],
+  include_directories: mod_inc_dir,
+  name_prefix: '',
+  install: true,
+  install_dir: modules_dir,
+  link_with: kresd,
+)