chore: reset resolver's connection after default interface changed

dns/client.go

@@ -103,3 +103,5 @@ func (c *client) ExchangeContext(ctx context.Context, m *D.Msg) (*D.Msg, error)
 		return ret.msg, ret.err
 	}
 }
+
+func (c *client) ResetConnection() {}

dns/dhcp.go

@@ -53,6 +53,12 @@ func (d *dhcpClient) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg,
 	return
 }
 
+func (d *dhcpClient) ResetConnection() {
+	for _, client := range d.clients {
+		client.ResetConnection()
+	}
+}
+
 func (d *dhcpClient) resolve(ctx context.Context) ([]dnsClient, error) {
 	d.lock.Lock()
 

dns/doh.go

@@ -203,11 +203,23 @@ func (doh *dnsOverHTTPS) Close() (err error) {
 	return doh.closeClient(doh.client)
 }
 
-// closeClient cleans up resources used by client if necessary.  Note, that at
-// this point it should only be done for HTTP/3 as it may leak due to keep-alive
-// connections.
+func (doh *dnsOverHTTPS) ResetConnection() {
+	doh.clientMu.Lock()
+	defer doh.clientMu.Unlock()
+
+	if doh.client == nil {
+		return
+	}
+
+	_ = doh.closeClient(doh.client)
+	doh.client = nil
+}
+
+// closeClient cleans up resources used by client if necessary.
 func (doh *dnsOverHTTPS) closeClient(client *http.Client) (err error) {
-	if isHTTP3(client) {
+	client.CloseIdleConnections()
+
+	if isHTTP3(client) { // HTTP/3 may leak due to keep-alive connections.
 		return client.Transport.(io.Closer).Close()
 	}
 
@@ -508,6 +520,13 @@ func (h *http3Transport) Close() (err error) {
 	return h.baseTransport.Close()
 }
 
+func (h *http3Transport) CloseIdleConnections() {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	h.baseTransport.CloseIdleConnections()
+}
+
 // createTransportH3 tries to create an HTTP/3 transport for this upstream.
 // We should be able to fall back to H1/H2 in case if HTTP/3 is unavailable or
 // if it is too slow.  In order to do that, this method will run two probes

dns/doq.go

@@ -144,6 +144,10 @@ func (doq *dnsOverQUIC) Close() (err error) {
 	return err
 }
 
+func (doq *dnsOverQUIC) ResetConnection() {
+	doq.closeConnWithError(nil)
+}
+
 // exchangeQUIC attempts to open a QUIC connection, send the DNS message
 // through it and return the response it got from the server.
 func (doq *dnsOverQUIC) exchangeQUIC(ctx context.Context, msg *D.Msg) (resp *D.Msg, err error) {

dns/patch_android.go

@@ -12,6 +12,7 @@ func FlushCacheWithDefaultResolver() {
 	if r := resolver.DefaultResolver; r != nil {
 		r.ClearCache()
 	}
+	resolver.ResetConnection()
 }
 
 func UpdateSystemDNS(addr []string) {
@@ -30,3 +31,9 @@ func UpdateSystemDNS(addr []string) {
 func (c *systemClient) getDnsClients() ([]dnsClient, error) {
 	return systemResolver, nil
 }
+
+func (c *systemClient) ResetConnection() {
+	for _, r := range systemResolver {
+		r.ResetConnection()
+	}
+}

dns/rcode.go

@@ -48,3 +48,5 @@ func (r rcodeClient) ExchangeContext(ctx context.Context, m *D.Msg) (*D.Msg, err
 func (r rcodeClient) Address() string {
 	return r.addr
 }
+
+func (r rcodeClient) ResetConnection() {}

dns/resolver.go

@@ -24,6 +24,7 @@ import (
 type dnsClient interface {
 	ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, err error)
 	Address() string
+	ResetConnection()
 }
 
 type dnsCache interface {
@@ -48,7 +49,7 @@ type Resolver struct {
 	group                 singleflight.Group[*D.Msg]
 	cache                 dnsCache
 	policy                []dnsPolicy
-	proxyServer           []dnsClient
+	defaultResolver       *Resolver
 }
 
 func (r *Resolver) LookupIPPrimaryIPv4(ctx context.Context, host string) (ips []netip.Addr, err error) {
@@ -376,6 +377,20 @@ func (r *Resolver) ClearCache() {
 	}
 }
 
+func (r *Resolver) ResetConnection() {
+	if r != nil {
+		for _, c := range r.main {
+			c.ResetConnection()
+		}
+		for _, c := range r.fallback {
+			c.ResetConnection()
+		}
+		if dr := r.defaultResolver; dr != nil {
+			dr.ResetConnection()
+		}
+	}
+}
+
 type NameServer struct {
 	Net          string
 	Addr         string
@@ -425,16 +440,18 @@ type Config struct {
 	CacheAlgorithm       string
 }
 
-func NewResolver(config Config) *Resolver {
-	var cache dnsCache
-	if config.CacheAlgorithm == "lru" {
-		cache = lru.New(lru.WithSize[string, *D.Msg](4096), lru.WithStale[string, *D.Msg](true))
+func (config Config) newCache() dnsCache {
+	if config.CacheAlgorithm == "" || config.CacheAlgorithm == "lru" {
+		return lru.New(lru.WithSize[string, *D.Msg](4096), lru.WithStale[string, *D.Msg](true))
 	} else {
-		cache = arc.New(arc.WithSize[string, *D.Msg](4096))
+		return arc.New(arc.WithSize[string, *D.Msg](4096))
 	}
+}
+
+func NewResolver(config Config) (r *Resolver, pr *Resolver) {
 	defaultResolver := &Resolver{
 		main:        transform(config.Default, nil),
-		cache:       cache,
+		cache:       config.newCache(),
 		ipv6Timeout: time.Duration(config.IPv6Timeout) * time.Millisecond,
 	}
 
@@ -465,27 +482,29 @@ func NewResolver(config Config) *Resolver {
 		return
 	}
 
-	if config.CacheAlgorithm == "" || config.CacheAlgorithm == "lru" {
-		cache = lru.New(lru.WithSize[string, *D.Msg](4096), lru.WithStale[string, *D.Msg](true))
-	} else {
-		cache = arc.New(arc.WithSize[string, *D.Msg](4096))
-	}
-	r := &Resolver{
+	r = &Resolver{
 		ipv6:        config.IPv6,
 		main:        cacheTransform(config.Main),
-		cache:       cache,
+		cache:       config.newCache(),
 		hosts:       config.Hosts,
 		ipv6Timeout: time.Duration(config.IPv6Timeout) * time.Millisecond,
 	}
+	r.defaultResolver = defaultResolver
+
+	if len(config.ProxyServer) != 0 {
+		pr = &Resolver{
+			ipv6:        config.IPv6,
+			main:        cacheTransform(config.ProxyServer),
+			cache:       config.newCache(),
+			hosts:       config.Hosts,
+			ipv6Timeout: time.Duration(config.IPv6Timeout) * time.Millisecond,
+		}
+	}
 
 	if len(config.Fallback) != 0 {
 		r.fallback = cacheTransform(config.Fallback)
 	}
 
-	if len(config.ProxyServer) != 0 {
-		r.proxyServer = cacheTransform(config.ProxyServer)
-	}
-
 	if len(config.Policy) != 0 {
 		r.policy = make([]dnsPolicy, 0)
 
@@ -516,18 +535,7 @@ func NewResolver(config Config) *Resolver {
 	r.fallbackIPFilters = config.FallbackIPFilter
 	r.fallbackDomainFilters = config.FallbackDomainFilter
 
-	return r
-}
-
-func NewProxyServerHostResolver(old *Resolver) *Resolver {
-	r := &Resolver{
-		ipv6:        old.ipv6,
-		main:        old.proxyServer,
-		cache:       old.cache,
-		hosts:       old.hosts,
-		ipv6Timeout: old.ipv6Timeout,
-	}
-	return r
+	return
 }
 
 var ParseNameServer func(servers []string) ([]NameServer, error) // define in config/config.go

dns/system_common.go

@@ -69,3 +69,5 @@ func (c *systemClient) getDnsClients() ([]dnsClient, error) {
 	}
 	return nil, err
 }
+
+func (c *systemClient) ResetConnection() {}