add new option: 'respond_with_ip'

.gitignore

@@ -9,3 +9,4 @@
 *~
 dnscrypt-proxy/dnscrypt-proxy2
 dnscrypt-proxy/dnscrypt-proxy
+.idea

dnscrypt-proxy/config.go

@@ -81,6 +81,7 @@ type Config struct {
 	OfflineMode              bool                       `toml:"offline_mode"`
 	HTTPProxyURL             string                     `toml:"http_proxy"`
 	RefusedCodeInResponses   bool                       `toml:"refused_code_in_responses"`
+	RespondWithIP            string                     `toml:"respond_with_ip"`
 }
 
 func newConfig() Config {
@@ -291,6 +292,7 @@ func ConfigLoad(proxy *Proxy, svcFlag *string) error {
 	proxy.xTransport.rebuildTransport()
 
 	proxy.refusedCodeInResponses = config.RefusedCodeInResponses
+	proxy.respondWithIP = config.RespondWithIP
 	proxy.timeout = time.Duration(config.Timeout) * time.Millisecond
 	proxy.maxClients = config.MaxClients
 	proxy.mainProto = "udp"

dnscrypt-proxy/dnsutils.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/binary"
+	"net"
 	"strings"
 	"time"
 
@@ -31,7 +32,7 @@ func EmptyResponseFromMessage(srcMsg *dns.Msg) (*dns.Msg, error) {
 	return dstMsg, nil
 }
 
-func RefusedResponseFromMessage(srcMsg *dns.Msg, refusedCode bool) (*dns.Msg, error) {
+func RefusedResponseFromMessage(srcMsg *dns.Msg, refusedCode bool, ip net.IP, ttl uint32) (*dns.Msg, error) {
 	dstMsg, err := EmptyResponseFromMessage(srcMsg)
 	if err != nil {
 		return dstMsg, err
@@ -42,12 +43,38 @@ func RefusedResponseFromMessage(srcMsg *dns.Msg, refusedCode bool) (*dns.Msg, er
 		dstMsg.Rcode = dns.RcodeSuccess
 		questions := srcMsg.Question
 		if len(questions) > 0 {
-			hinfo := new(dns.HINFO)
-			hinfo.Hdr = dns.RR_Header{Name: questions[0].Name, Rrtype: dns.TypeHINFO,
-				Class: dns.ClassINET, Ttl: 1}
-			hinfo.Cpu = "This query has been locally blocked"
-			hinfo.Os = "by dnscrypt-proxy"
-			dstMsg.Answer = []dns.RR{hinfo}
+			question := questions[0]
+			sendHInfoResponse := true
+
+			if ip != nil {
+				if question.Qtype == dns.TypeA {
+					rr := new(dns.A)
+					rr.Hdr = dns.RR_Header{Name: question.Name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: ttl}
+					rr.A = ip.To4()
+					if rr.A != nil {
+						dstMsg.Answer = []dns.RR{rr}
+						sendHInfoResponse = false
+					}
+
+				} else if question.Qtype == dns.TypeAAAA {
+					rr := new(dns.AAAA)
+					rr.Hdr = dns.RR_Header{Name: question.Name, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: ttl}
+					rr.AAAA = ip.To16()
+					if rr.AAAA != nil {
+						dstMsg.Answer = []dns.RR{rr}
+						sendHInfoResponse = false
+					}
+				}
+			}
+
+			if sendHInfoResponse {
+				hinfo := new(dns.HINFO)
+				hinfo.Hdr = dns.RR_Header{Name: question.Name, Rrtype: dns.TypeHINFO,
+					Class: dns.ClassINET, Ttl: 1}
+				hinfo.Cpu = "This query has been locally blocked"
+				hinfo.Os = "by dnscrypt-proxy"
+				dstMsg.Answer = []dns.RR{hinfo}
+			}
 		}
 	}
 	return dstMsg, nil

dnscrypt-proxy/example-dnscrypt-proxy.toml

@@ -117,6 +117,12 @@ keepalive = 30
 
 refused_code_in_responses = false
 
+## If refused_code_in_responses is `false`, use this optional setting
+## to redirect blocked respones to an IP address (e.g. pixelserv-tls)
+## instead of returning an HINFO record
+
+# respond_with_ip = '192.168.1.4'
+
 
 ## Load-balancing strategy: 'p2' (default), 'ph', 'first' or 'random'
 

dnscrypt-proxy/plugins.go

@@ -26,6 +26,7 @@ type PluginsGlobals struct {
 	responsePlugins        *[]Plugin
 	loggingPlugins         *[]Plugin
 	refusedCodeInResponses bool
+	respondWithIP          net.IP
 }
 
 type PluginsReturnCode int
@@ -136,6 +137,7 @@ func InitPluginsGlobals(pluginsGlobals *PluginsGlobals, proxy *Proxy) error {
 	(*pluginsGlobals).responsePlugins = responsePlugins
 	(*pluginsGlobals).loggingPlugins = loggingPlugins
 	(*pluginsGlobals).refusedCodeInResponses = proxy.refusedCodeInResponses
+	(*pluginsGlobals).respondWithIP = net.ParseIP(proxy.respondWithIP)
 	return nil
 }
 
@@ -186,7 +188,7 @@ func (pluginsState *PluginsState) ApplyQueryPlugins(pluginsGlobals *PluginsGloba
 			return packet, ret
 		}
 		if pluginsState.action == PluginsActionReject {
-			synth, err := RefusedResponseFromMessage(&msg, pluginsGlobals.refusedCodeInResponses)
+			synth, err := RefusedResponseFromMessage(&msg, pluginsGlobals.refusedCodeInResponses, pluginsGlobals.respondWithIP, pluginsState.cacheMinTTL)
 			if err != nil {
 				return nil, err
 			}
@@ -234,7 +236,7 @@ func (pluginsState *PluginsState) ApplyResponsePlugins(pluginsGlobals *PluginsGl
 			return packet, ret
 		}
 		if pluginsState.action == PluginsActionReject {
-			synth, err := RefusedResponseFromMessage(&msg, pluginsGlobals.refusedCodeInResponses)
+			synth, err := RefusedResponseFromMessage(&msg, pluginsGlobals.refusedCodeInResponses, pluginsGlobals.respondWithIP, pluginsState.cacheMinTTL)
 			if err != nil {
 				return nil, err
 			}

dnscrypt-proxy/proxy.go

@@ -64,6 +64,7 @@ type Proxy struct {
 	logMaxAge                    int
 	logMaxBackups                int
 	refusedCodeInResponses       bool
+	respondWithIP                string
 	showCerts                    bool
 }