From ac3b85114bb6effa5dbf6c943d81a9d1c361c9be Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Tue, 14 Mar 2023 21:15:04 -0700
Subject: [PATCH] ircd::net::dns::resolver: Add conf item to ease off ServFail
 retries.

---
 include/ircd/net/dns_resolver.h |  1 +
 ircd/net_dns_resolver.cc        | 16 +++++++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/ircd/net/dns_resolver.h b/include/ircd/net/dns_resolver.h
index ae3ac8cfa..284fd66dc 100644
--- a/include/ircd/net/dns_resolver.h
+++ b/include/ircd/net/dns_resolver.h
@@ -37,6 +37,7 @@ ircd::net::dns::resolver
 	static conf::item<milliseconds> send_rate;
 	static conf::item<size_t> send_burst;
 	static conf::item<size_t> retry_max;
+	static conf::item<bool> retry_serv_fail;
 
 	answers_callback callback;
 	std::vector<ip::udp::endpoint> server;       // The list of active servers
diff --git a/ircd/net_dns_resolver.cc b/ircd/net_dns_resolver.cc
index f64ff673d..100310938 100644
--- a/ircd/net_dns_resolver.cc
+++ b/ircd/net_dns_resolver.cc
@@ -39,6 +39,13 @@ ircd::net::dns::resolver::retry_max
 	{ "default",   20L                              },
 };
 
+decltype(ircd::net::dns::resolver::retry_serv_fail)
+ircd::net::dns::resolver::retry_serv_fail
+{
+	{ "name",     "ircd.net.dns.resolver.retry_serv_fail" },
+	{ "default",  true                                    },
+};
+
 decltype(ircd::net::dns::resolver::servers)
 ircd::net::dns::resolver::servers
 {
@@ -726,7 +733,14 @@ ircd::net::dns::resolver::handle_reply(const ipport &from,
 
 	// Handle ServFail as a special case here. We can try again without
 	// handling this tag or propagating this error any further yet.
-	if(header.rcode == 2 && tag.tries < size_t(server.size()))
+	const bool serv_fail_retry
+	{
+		retry_serv_fail
+		&& header.rcode == 2
+		&& tag.tries < size_t(server.size())
+	};
+
+	if(serv_fail_retry)
 	{
 		log::error
 		{