From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Tue, 23 Mar 2021 10:11:44 +0000 (+0100)
Subject: lib/selection*: try to avoid TCP in STUB mode
X-Git-Tag: v5.3.1~3^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a07a58f739dc48b85aa6ac1e61150ee3847ff4a1;p=thirdparty%2Fknot-resolver.git

lib/selection*: try to avoid TCP in STUB mode

The target of STUB might commonly not have good support
for "advanced" features like TCP.
---

diff --git a/NEWS b/NEWS
index 839084d65..c8682aba5 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,7 @@ Knot Resolver 5.3.1 (2021-03-dd)
 Improvements
 ------------
 - doh2: send HTTP error status codes (#618, !1102)
+- policy.STUB: try to avoid TCP (compared to 5.3.0; !1155)
 
 Bugfixes
 --------
diff --git a/lib/selection_forward.c b/lib/selection_forward.c
index 165aa53f4..6fa3d743a 100644
--- a/lib/selection_forward.c
+++ b/lib/selection_forward.c
@@ -86,6 +86,9 @@ void forward_choose_transport(struct kr_query *qry,
 		 * says nothing about the network RTT of said target, since
 		 * it is doing resolution upstream. */
 		(*transport)->timeout = FORWARDING_TIMEOUT;
+		/* Try to avoid TCP in STUB case.  It seems better for common use cases. */
+		if (qry->flags.STUB && !tcp && (*transport)->protocol == KR_TRANSPORT_TCP)
+			(*transport)->protocol = KR_TRANSPORT_UDP;
 		/* We need to propagate this to flags since it's used in other
 		 * parts of the resolver (e.g. logging and stats). */
 		qry->flags.TCP = tcp;