add ip_lookup_strategy config option for hickory resolver

Signed-off-by: strawberry <strawberry@puppygock.gay>

conduwuit-example.toml

@@ -514,6 +514,21 @@ allow_profile_lookup_federation_requests = true
 # The default is to query one nameserver and stop (false).
 #query_all_nameservers = true
 
+# DNS A/AAAA record lookup strategy
+#
+# Takes a number of one of the following options:
+# 1 - Ipv4Only (Only query for A records, no AAAA/IPv6)
+# 2 - Ipv6Only (Only query for AAAA records, no A/IPv4)
+# 3 - Ipv4AndIpv6 (Query for A and AAAA records in parallel, uses whatever returns a successful response first)
+# 4 - Ipv6thenIpv4 (Query for AAAA record, if that fails then query the A record)
+# 5 - Ipv4thenIpv6 (Query for A record, if that fails then query the AAAA record)
+#
+# If you don't have IPv6 networking, then for better performance it may be suitable to set this to Ipv4Only (1) as
+# you will never ever use the AAAA record contents even if the AAAA record is successful instead of the A record.
+#
+# Defaults to 5 - Ipv4ThenIpv6 as this is the most compatible and IPv4 networking is currently the most prevalent.
+#ip_lookup_strategy = 5
+
 
 ### Request Timeouts, Connection Timeouts, and Connection Pooling
 

src/config/mod.rs

@@ -103,6 +103,8 @@ pub(crate) struct Config {
 	pub(crate) dns_tcp_fallback: bool,
 	#[serde(default = "true_fn")]
 	pub(crate) query_all_nameservers: bool,
+	#[serde(default = "default_ip_lookup_strategy")]
+	pub(crate) ip_lookup_strategy: u8,
 
 	#[serde(default = "default_max_request_size")]
 	pub(crate) max_request_size: u32,
@@ -902,6 +904,8 @@ fn default_dns_attempts() -> u16 { 10 }
 
 fn default_dns_timeout() -> u64 { 10 }
 
+fn default_ip_lookup_strategy() -> u8 { 5 }
+
 fn default_max_request_size() -> u32 {
 	20 * 1024 * 1024 // Default to 20 MB
 }

src/service/globals/resolver.rs

@@ -67,6 +67,13 @@ impl Resolver {
 		opts.num_concurrent_reqs = 1;
 		opts.shuffle_dns_servers = true;
 		opts.rotate = true;
+		opts.ip_strategy = match config.ip_lookup_strategy {
+			1 => hickory_resolver::config::LookupIpStrategy::Ipv4Only,
+			2 => hickory_resolver::config::LookupIpStrategy::Ipv6Only,
+			3 => hickory_resolver::config::LookupIpStrategy::Ipv4AndIpv6,
+			4 => hickory_resolver::config::LookupIpStrategy::Ipv6thenIpv4,
+			_ => hickory_resolver::config::LookupIpStrategy::Ipv4thenIpv6,
+		};
 
 		let resolver = Arc::new(TokioAsyncResolver::tokio(conf, opts));
 		let overrides = Arc::new(StdRwLock::new(TlsNameMap::new()));