feat: shorten dns cache ttl of empty record

Author: linfan

pkg/common/dns_util.go

@@ -57,8 +57,8 @@ func ReadCache(domain string, qtype uint16, ttl int64) []dns.RR {
 }
 
 // WriteCache record to cache
-func WriteCache(domain string, qtype uint16, answer []dns.RR) {
-	nsCache.Store(getCacheKey(domain, qtype), NsEntry{answer, time.Now().Unix()})
+func WriteCache(domain string, qtype uint16, answer []dns.RR, timestamp int64) {
+	nsCache.Store(getCacheKey(domain, qtype), NsEntry{answer, timestamp})
 }
 
 func notExpired(timestamp int64, ttl int64) bool {

pkg/kt/service/dns/dnsserver.go

@@ -88,14 +88,14 @@ func query(req *dns.Msg, dnsAddresses []string) []dns.RR {
 		if res != nil && len(res.Answer) > 0 {
 			// only record none-empty result of cluster dns
 			log.Debug().Msgf("Found domain %s (%d) in dns (%s)", domain, qtype, ipAndPort)
-			common.WriteCache(domain, qtype, res.Answer)
+			common.WriteCache(domain, qtype, res.Answer, time.Now().Unix())
 			return res.Answer
 		} else if err != nil && !common.IsDomainNotExist(err) {
 			// usually io timeout error
 			log.Warn().Err(err).Msgf("Failed to lookup %s (%d) in dns (%s)", domain, qtype, ipAndPort)
 		}
 	}
 	log.Debug().Msgf("Empty answer for domain lookup %s (%d)", domain, qtype)
-	common.WriteCache(domain, qtype, []dns.RR{})
+	common.WriteCache(domain, qtype, []dns.RR{}, time.Now().Unix() - opt.Get().ConnectOptions.DnsCacheTtl / 2)
 	return []dns.RR{}
 }

pkg/shadow/dnsserver/dnsserver.go

@@ -8,6 +8,7 @@ import (
 	"github.com/rs/zerolog/log"
 	"net"
 	"strings"
+	"time"
 )
 
 // DnsServer nds server
@@ -77,7 +78,7 @@ func (s *DnsServer) query(req *dns.Msg) (rr []dns.RR) {
 			break
 		}
 	}
-	common.WriteCache(name, qtype, rr)
+	common.WriteCache(name, qtype, rr, time.Now().Unix())
 	return
 }