From: Štěpán Balážik <stepan.balazik@nic.cz>
Date: Fri, 9 Oct 2020 14:54:01 +0000 (+0200)
Subject: selection: support serve_stale module
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a59ab5cef466de90fcfdf1bc5c577f389b95faea;p=thirdparty%2Fknot-resolver.git

selection: support serve_stale module
---

diff --git a/lib/resolve.c b/lib/resolve.c
index 2239735ea..5dfeb88ae 100644
--- a/lib/resolve.c
+++ b/lib/resolve.c
@@ -1323,8 +1323,14 @@ int kr_resolve_produce(struct kr_request *request, struct kr_transport **transpo
 	qry->server_selection.choose_transport(qry, transport);
 
 	if (*transport == NULL) {
-		// There is no point in continuing.
-		return KR_STATE_FAIL;
+		/* Properly signal to serve_stale module. */
+		if (qry->flags.NO_NS_FOUND) {
+			ITERATE_LAYERS(request, qry, reset);
+			kr_rplan_pop(rplan, qry);
+		} else {
+			qry->flags.NO_NS_FOUND = true;
+		}
+		return KR_STATE_PRODUCE;
 	}
 
 	if ((*transport)->protocol == KR_TRANSPORT_NOADDR) {
diff --git a/lib/selection.c b/lib/selection.c
index 52f39c186..60696454c 100644
--- a/lib/selection.c
+++ b/lib/selection.c
@@ -359,6 +359,10 @@ void error(struct kr_query *qry, struct address_state *addr_state, const struct
 		qry->server_selection.truncated = true;
 	}
 
+	if (UNRECOVERABLE_ERRORS[sel_error]) {
+		addr_state->unrecoverable_errors++;
+	}
+
 	addr_state->errors[sel_error]++;
 	addr_state->error_count++;
 
diff --git a/lib/selection.h b/lib/selection.h
index 743e0c532..a102ca085 100644
--- a/lib/selection.h
+++ b/lib/selection.h
@@ -34,7 +34,22 @@ enum kr_selection_error {
 	KR_SELECTION_DNSSEC_ERROR,
 	KR_SELECTION_LAME_DELEGATION,
 
-	KR_SELECTION_NUMBER_OF_ERRORS /**< Leave this last, as it is use as array size. */
+	KR_SELECTION_NUMBER_OF_ERRORS /**< Leave this last, as it is used as array size. */
+};
+
+static const bool UNRECOVERABLE_ERRORS[] = {
+	[KR_SELECTION_TIMEOUT] = false,
+	[KR_SELECTION_TLS_HANDSHAKE_FAILED] = false,
+	[KR_SELECTION_TCP_CONNECT_FAILED] = false,
+	[KR_SELECTION_TCP_CONNECT_TIMEOUT] = false,
+	[KR_SELECTION_REFUSED] = true,
+	[KR_SELECTION_SERVFAIL] = true,
+	[KR_SELECTION_FORMERROR] = true,
+	[KR_SELECTION_NOTIMPL] = true,
+	[KR_SELECTION_OTHER_RCODE] = true,
+	[KR_SELECTION_TRUNCATED] = false,
+	[KR_SELECTION_DNSSEC_ERROR] = true,
+	[KR_SELECTION_LAME_DELEGATION] = true,
 };
 
 enum kr_transport_protocol {
@@ -128,6 +143,7 @@ struct address_state {
 
 	int forward_index;
 	int error_count;
+	int unrecoverable_errors;
 	int errors[KR_SELECTION_NUMBER_OF_ERRORS];
 };
 
diff --git a/lib/selection_iter.c b/lib/selection_iter.c
index 9ec0f8e7d..09bbfc185 100644
--- a/lib/selection_iter.c
+++ b/lib/selection_iter.c
@@ -163,7 +163,7 @@ void iter_choose_transport(struct kr_query *qry, struct kr_transport **transport
 		size_t address_len;
 		uint8_t* address = (uint8_t *)trie_it_key(it, &address_len);
 		struct address_state *address_state = (struct address_state *)*trie_it_val(it);
-		if (address_state->generation == local_state->generation) {
+		if (address_state->generation == local_state->generation && !address_state->unrecoverable_errors) {
 			choices[valid_addresses] = (struct choice){
 				.address = address,
 				.address_len = address_len,