Support multiple routes per destination

dnscrypt-proxy/config.go

@@ -168,8 +168,8 @@ type BlockIPConfig struct {
 }
 
 type AnonymizedDNSRouteConfig struct {
-	ServerName string `toml:"server_name"`
-	RelayName  string `toml:"via"`
+	ServerName string   `toml:"server_name"`
+	RelayNames []string `toml:"via"`
 }
 
 type AnonymizedDNSConfig struct {
@@ -433,10 +433,9 @@ func ConfigLoad(proxy *Proxy, svcFlag *string) error {
 	proxy.allWeeklyRanges = allWeeklyRanges
 
 	if configRoutes := config.AnonymizedDNS.Routes; configRoutes != nil {
-		routes := make(map[string]string)
+		routes := make(map[string][]string)
 		for _, configRoute := range configRoutes {
-			routes[configRoute.ServerName] = configRoute.RelayName
-			dlog.Debugf("Routing server [%s] via [%s]", configRoute.ServerName, configRoute.RelayName)
+			routes[configRoute.ServerName] = configRoute.RelayNames
 		}
 		proxy.routes = &routes
 	}
@@ -491,7 +490,7 @@ func ConfigLoad(proxy *Proxy, svcFlag *string) error {
 	if proxy.routes != nil && len(*proxy.routes) > 0 {
 		for _, server := range proxy.registeredServers {
 			if via, ok := (*proxy.routes)[server.name]; ok {
-				dlog.Noticef("Anonymized DNS: routing [%v] via [%v]", server.name, via)
+				dlog.Noticef("Anonymized DNS: routing [%v] via %v", server.name, via)
 			}
 		}
 	}

dnscrypt-proxy/example-dnscrypt-proxy.toml

@@ -546,6 +546,23 @@ cache_neg_max_ttl = 600
   #  minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'
 
 
+################################
+#        Anonymized DNS        #
+################################
+
+[anonymized_dns]
+
+## Define one or more routes, i.e. indirect ways to reach servers.
+## A set of possible relay servers is assigned to each DNS resolver.
+## A relay can be specified as a DNS Stamp (either a relay stamp, or a
+## DNSCrypt stamp), an IP:port, a hostname:port, or a server name, if
+## the server is in the servers_list.
+
+# routes = [
+#    { server_name='comodo-02', via=['sdns://gRIxMzcuNzQuMjIzLjIzNDo0NDM'] },
+#    { server_name='quad9-dnscrypt-ip4-nofilter-pri', via=['sdns://gRIxMzcuNzQuMjIzLjIzNDo0NDM'] }
+# ]
+
 
 ## Optional, local, static list of additional servers
 ## Mostly useful for testing your own servers.

dnscrypt-proxy/proxy.go

@@ -66,7 +66,7 @@ type Proxy struct {
 	logMaxBackups                int
 	blockedQueryResponse         string
 	queryMeta                    []string
-	routes                       *map[string]string
+	routes                       *map[string][]string
 	showCerts                    bool
 }
 

dnscrypt-proxy/serversInfo.go

@@ -264,9 +264,16 @@ func (serversInfo *ServersInfo) fetchDNSCryptServerInfo(proxy *Proxy, name strin
 	var relayTCPAddr *net.TCPAddr
 	routes := proxy.routes
 	if routes != nil {
-		if relayName, ok := (*routes)[name]; ok {
+		if relayNames, ok := (*routes)[name]; ok {
+			var relayName string
+			if len(relayNames) > 0 {
+				candidate := rand.Intn(len(relayNames))
+				relayName = relayNames[candidate]
+			}
 			var relayCandidateStamp *stamps.ServerStamp
-			if stamp, err = stamps.NewServerStampFromString(relayName); err == nil {
+			if len(relayName) == 0 {
+				dlog.Errorf("Route declared for [%v] but an empty relay list", name)
+			} else if stamp, err = stamps.NewServerStampFromString(relayName); err == nil {
 				relayCandidateStamp = &stamp
 			} else if _, err := net.ResolveUDPAddr("udp", relayName); err == nil {
 				relayCandidateStamp = &stamps.ServerStamp{