chore: share dnsClient in NewResolver

dns/resolver.go

@@ -19,6 +19,7 @@ import (
 
 	D "github.com/miekg/dns"
 	"github.com/samber/lo"
+	"golang.org/x/exp/maps"
 	"golang.org/x/sync/singleflight"
 )
 
@@ -370,6 +371,23 @@ type NameServer struct {
 	PreferH3     bool
 }
 
+func (ns NameServer) Equal(ns2 NameServer) bool {
+	defer func() {
+		// C.ProxyAdapter compare maybe panic, just ignore
+		recover()
+	}()
+	if ns.Net == ns2.Net &&
+		ns.Addr == ns2.Addr &&
+		ns.Interface == ns2.Interface &&
+		ns.ProxyAdapter == ns2.ProxyAdapter &&
+		ns.ProxyName == ns2.ProxyName &&
+		maps.Equal(ns.Params, ns2.Params) &&
+		ns.PreferH3 == ns2.PreferH3 {
+		return true
+	}
+	return false
+}
+
 type FallbackFilter struct {
 	GeoIP     bool
 	GeoIPCode string
@@ -399,20 +417,47 @@ func NewResolver(config Config) *Resolver {
 		ipv6Timeout: time.Duration(config.IPv6Timeout) * time.Millisecond,
 	}
 
+	var nameServerCache []struct {
+		NameServer
+		dnsClient
+	}
+	cacheTransform := func(nameserver []NameServer) (result []dnsClient) {
+	LOOP:
+		for _, ns := range nameserver {
+			for _, nsc := range nameServerCache {
+				if nsc.NameServer.Equal(ns) {
+					result = append(result, nsc.dnsClient)
+					continue LOOP
+				}
+			}
+			// not in cache
+			dc := transform([]NameServer{ns}, defaultResolver)
+			if len(dc) > 0 {
+				dc := dc[0]
+				nameServerCache = append(nameServerCache, struct {
+					NameServer
+					dnsClient
+				}{NameServer: ns, dnsClient: dc})
+				result = append(result, dc)
+			}
+		}
+		return
+	}
+
 	r := &Resolver{
 		ipv6:        config.IPv6,
-		main:        transform(config.Main, defaultResolver),
+		main:        cacheTransform(config.Main),
 		lruCache:    cache.New(cache.WithSize[string, *D.Msg](4096), cache.WithStale[string, *D.Msg](true)),
 		hosts:       config.Hosts,
 		ipv6Timeout: time.Duration(config.IPv6Timeout) * time.Millisecond,
 	}
 
 	if len(config.Fallback) != 0 {
-		r.fallback = transform(config.Fallback, defaultResolver)
+		r.fallback = cacheTransform(config.Fallback)
 	}
 
 	if len(config.ProxyServer) != 0 {
-		r.proxyServer = transform(config.ProxyServer, defaultResolver)
+		r.proxyServer = cacheTransform(config.ProxyServer)
 	}
 
 	if len(config.Policy) != 0 {
@@ -426,6 +471,7 @@ func NewResolver(config Config) *Resolver {
 				triePolicy = nil
 			}
 		}
+
 		for _, p := range config.Policy {
 			domain, nameserver := p.Extract()
 			domain = strings.ToLower(domain)
@@ -439,7 +485,7 @@ func NewResolver(config Config) *Resolver {
 						insertTriePolicy()
 						r.policy = append(r.policy, domainSetPolicy{
 							domainSetProvider: p,
-							dnsClients:        transform(nameserver, defaultResolver),
+							dnsClients:        cacheTransform(nameserver),
 						})
 						continue
 					}
@@ -458,7 +504,7 @@ func NewResolver(config Config) *Resolver {
 					r.policy = append(r.policy, geositePolicy{
 						matcher:    matcher,
 						inverse:    inverse,
-						dnsClients: transform(nameserver, defaultResolver),
+						dnsClients: cacheTransform(nameserver),
 					})
 					continue
 				}
@@ -466,7 +512,7 @@ func NewResolver(config Config) *Resolver {
 			if triePolicy == nil {
 				triePolicy = trie.New[[]dnsClient]()
 			}
-			_ = triePolicy.Insert(domain, transform(nameserver, defaultResolver))
+			_ = triePolicy.Insert(domain, cacheTransform(nameserver))
 		}
 		insertTriePolicy()
 	}