Improve DNS caching

docs/configuration/dns/index.md

@@ -11,6 +11,7 @@
     "strategy": "",
     "disable_cache": false,
     "disable_expire": false,
+    "independent_cache": false,
     "reverse_mapping": false,
     "fakeip": {}
   }
@@ -48,6 +49,10 @@ Disable dns cache.
 
 Disable dns cache expire.
 
+#### independent_cache
+
+Make each DNS server's cache independent for special purposes. If enabled, will slightly degrade performance.
+
 #### reverse_mapping
 
 Stores a reverse mapping of IP addresses after responding to a DNS query in order to provide domain names when routing.

docs/configuration/dns/index.zh.md

@@ -11,6 +11,7 @@
     "strategy": "",
     "disable_cache": false,
     "disable_expire": false,
+    "independent_cache": false,
     "reverse_mapping": false,
     "fakeip": {}
   }
@@ -47,6 +48,10 @@
 
 禁用 DNS 缓存过期。
 
+#### independent_cache
+
+使每个 DNS 服务器的缓存独立，以满足特殊目的。如果启用，将轻微降低性能。
+
 #### reverse_mapping
 
 在响应 DNS 查询后存储 IP 地址的反向映射以为路由目的提供域名。

go.mod

@@ -25,7 +25,7 @@ require (
 	github.com/sagernet/quic-go v0.0.0-20230202071646-a8c8afb18b32
 	github.com/sagernet/reality v0.0.0-20230406110435-ee17307e7691
 	github.com/sagernet/sing v0.2.5-0.20230425122720-bf0aaacc6754
-	github.com/sagernet/sing-dns v0.1.5-0.20230415085626-111ecf799dfc
+	github.com/sagernet/sing-dns v0.1.5-0.20230426113254-25d948c44223
 	github.com/sagernet/sing-mux v0.0.0-20230425130511-b0a6ffd8406f
 	github.com/sagernet/sing-shadowsocks v0.2.2-0.20230417102954-f77257340507
 	github.com/sagernet/sing-shadowtls v0.1.2-0.20230417103049-4f682e05f19b

go.sum

@@ -113,8 +113,8 @@ github.com/sagernet/sing v0.0.0-20220817130738-ce854cda8522/go.mod h1:QVsS5L/ZA2
 github.com/sagernet/sing v0.1.8/go.mod h1:jt1w2u7lJQFFSGLiRrRIs5YWmx4kAPfWuOejuDW9qMk=
 github.com/sagernet/sing v0.2.5-0.20230425122720-bf0aaacc6754 h1:y89Ntm1rrZPQVb1f+TKd4DH6NwX5XCyMIwoseTQd/5U=
 github.com/sagernet/sing v0.2.5-0.20230425122720-bf0aaacc6754/go.mod h1:Ta8nHnDLAwqySzKhGoKk4ZIB+vJ3GTKj7UPrWYvM+4w=
-github.com/sagernet/sing-dns v0.1.5-0.20230415085626-111ecf799dfc h1:hmbuqKv48SAjiKPoqtJGvS5pEHVPZjTHq9CPwQY2cZ4=
+github.com/sagernet/sing-dns v0.1.5-0.20230426113254-25d948c44223 h1:L4eMuM07iSHY3UCknFnuFuHoe5clZuF2Xnf2wwA6Lwc=
-github.com/sagernet/sing-dns v0.1.5-0.20230415085626-111ecf799dfc/go.mod h1:ZKuuqgsHRxDahYrzgSgy4vIAGGuKPlIf4hLcNzYzLkY=
+github.com/sagernet/sing-dns v0.1.5-0.20230426113254-25d948c44223/go.mod h1:ZKuuqgsHRxDahYrzgSgy4vIAGGuKPlIf4hLcNzYzLkY=
 github.com/sagernet/sing-mux v0.0.0-20230425130511-b0a6ffd8406f h1:iEpOTgBTjt0vZJVXMTqYq13XyIu/337TWbq6WZ3CMWc=
 github.com/sagernet/sing-mux v0.0.0-20230425130511-b0a6ffd8406f/go.mod h1:pF+RnLvCAOhECrvauy6LYOpBakJ/vuaF1Wm4lPsWryI=
 github.com/sagernet/sing-shadowsocks v0.2.2-0.20230417102954-f77257340507 h1:bAHZCdWqJkb8LEW98+YsMVDXGRMUVjka8IC+St6ot88=

option/dns.go

@@ -23,6 +23,7 @@ type DNSClientOptions struct {
 	Strategy         DomainStrategy `json:"strategy,omitempty"`
 	DisableCache     bool           `json:"disable_cache,omitempty"`
 	DisableExpire    bool           `json:"disable_expire,omitempty"`
+	IndependentCache bool           `json:"independent_cache,omitempty"`
 }
 
 type DNSFakeIPOptions struct {

route/router.go

@@ -113,7 +113,12 @@ func NewRouter(
 		defaultMark:           options.DefaultMark,
 		platformInterface:     platformInterface,
 	}
-	router.dnsClient = dns.NewClient(dnsOptions.DNSClientOptions.DisableCache, dnsOptions.DNSClientOptions.DisableExpire, router.dnsLogger)
+	router.dnsClient = dns.NewClient(dns.ClientOptions{
+		DisableCache:     dnsOptions.DNSClientOptions.DisableCache,
+		DisableExpire:    dnsOptions.DNSClientOptions.DisableExpire,
+		IndependentCache: dnsOptions.DNSClientOptions.IndependentCache,
+		Logger:           router.dnsLogger,
+	})
 	for i, ruleOptions := range options.Rules {
 		routeRule, err := NewRule(router, router.logger, ruleOptions)
 		if err != nil {

route/router_dns.go

@@ -73,6 +73,13 @@ func (r *Router) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, er
 	if len(message.Question) > 0 {
 		r.dnsLogger.DebugContext(ctx, "exchange ", formatQuestion(message.Question[0].String()))
 	}
+	var (
+		response *mDNS.Msg
+		cached   bool
+		err      error
+	)
+	response, cached = r.dnsClient.ExchangeCache(ctx, message)
+	if !cached {
 		ctx, metadata := adapter.AppendContext(ctx)
 		if len(message.Question) > 0 {
 			metadata.QueryType = message.Question[0].Qtype
@@ -87,10 +94,11 @@ func (r *Router) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, er
 		ctx, transport, strategy := r.matchDNS(ctx)
 		ctx, cancel := context.WithTimeout(ctx, C.DNSTimeout)
 		defer cancel()
-	response, err := r.dnsClient.Exchange(ctx, transport, message, strategy)
+		response, err = r.dnsClient.Exchange(ctx, transport, message, strategy)
 		if err != nil && len(message.Question) > 0 {
 			r.dnsLogger.ErrorContext(ctx, E.Cause(err, "exchange failed for ", formatQuestion(message.Question[0].String())))
 		}
+	}
 	if len(message.Question) > 0 && response != nil {
 		LogDNSAnswers(r.dnsLogger, ctx, message.Question[0].Name, response.Answer)
 	}