Revert "Allow serve_stale to be disabled"

This reverts commit 3b2301dcbf.

example-encrypted-dns.toml

@@ -78,12 +78,6 @@ cache_ttl_min = 3600
 cache_ttl_max = 86400
 
 
-## Temporarily serve cached entries after their TTL expired
-## when servers are not responsive.
-
-serve_stale = true
-
-
 ## DNS cache: error TTL
 
 cache_ttl_error = 600

src/config.rs

@@ -64,7 +64,6 @@ pub struct Config {
     pub cache_ttl_min: u32,
     pub cache_ttl_max: u32,
     pub cache_ttl_error: u32,
-    pub serve_stale: Option<bool>,
     pub user: Option<String>,
     pub group: Option<String>,
     pub chroot: Option<String>,

src/globals.rs

@@ -41,7 +41,6 @@ pub struct Globals {
     pub cache: Cache,
     pub cert_cache: Cache,
     pub blacklist: Option<BlackList>,
-    pub serve_stale: bool,
     pub anonymized_dns_enabled: bool,
     pub anonymized_dns_allowed_ports: Vec<u16>,
     pub anonymized_dns_allow_non_reserved_ports: bool,

src/main.rs

@@ -509,7 +509,6 @@ fn main() -> Result<(), Error> {
 
     let key_cache_capacity = config.dnscrypt.key_cache_capacity;
     let cache_capacity = config.cache_capacity;
-    let serve_stale = config.serve_stale.unwrap_or(true);
     let state_file = &config.state_file;
 
     if let Some(secret_key_path) = matches.value_of("import-from-dnscrypt-wrapper") {
@@ -657,7 +656,6 @@ fn main() -> Result<(), Error> {
         hasher,
         cache,
         cert_cache,
-        serve_stale,
         blacklist,
         anonymized_dns_enabled,
         anonymized_dns_allowed_ports,

src/resolver.rs

@@ -129,7 +129,7 @@ pub async fn resolve(
     globals.varz.upstream_received.inc();
     if dns::rcode_servfail(&response) || dns::rcode_refused(&response) {
         trace!("SERVFAIL/REFUSED: {}", dns::rcode(&response));
-        if let (true, Some(cached_response)) = (globals.serve_stale, cached_response) {
+        if let Some(cached_response) = cached_response {
             trace!("Serving stale");
             #[cfg(feature = "metrics")]
             {