Nits

dnscrypt-proxy/coldstart.go

@@ -22,7 +22,7 @@ type CaptivePortalHandler struct {
 	cancelChannels []chan struct{}
 }
 
-func (captivePortalHandler *CaptivePortalHandler) Stop() {	
+func (captivePortalHandler *CaptivePortalHandler) Stop() {
 	for _, cancelChannel := range captivePortalHandler.cancelChannels {
 		cancelChannel <- struct{}{}
 		_ = <-cancelChannel

dnscrypt-proxy/plugin_dns64.go

@@ -30,7 +30,7 @@ func (plugin *PluginDNS64) Name() string {
 }
 
 func (plugin *PluginDNS64) Description() string {
-	return "Synth DNS64 AAAA responses"
+	return "Synthesize DNS64 AAAA responses"
 }
 
 func (plugin *PluginDNS64) Init(proxy *Proxy) error {

dnscrypt-proxy/plugin_ecs.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"math/rand"
+	"net"
+
+	"github.com/miekg/dns"
+)
+
+type PluginECS struct {
+	nets []*net.IPNet
+}
+
+func (plugin *PluginECS) Name() string {
+	return "ecs"
+}
+
+func (plugin *PluginECS) Description() string {
+	return "Set EDNS-client-subnet information in outgoing queries."
+}
+
+func (plugin *PluginECS) Init(proxy *Proxy) error {
+	plugin.nets = proxy.ednsClientSubnets
+	return nil
+}
+
+func (plugin *PluginECS) Drop() error {
+	return nil
+}
+
+func (plugin *PluginECS) Reload() error {
+	return nil
+}
+
+func (plugin *PluginECS) Eval(pluginsState *PluginsState, msg *dns.Msg) error {
+	var options *[]dns.EDNS0
+
+	for _, extra := range msg.Extra {
+		if extra.Header().Rrtype == dns.TypeOPT {
+			options = &extra.(*dns.OPT).Option
+			for _, option := range *options {
+				if option.Option() == dns.EDNS0SUBNET {
+					return nil
+				}
+			}
+			break
+		}
+	}
+	if options == nil {
+		msg.SetEdns0(uint16(pluginsState.maxPayloadSize), false)
+		for _, extra := range msg.Extra {
+			if extra.Header().Rrtype == dns.TypeOPT {
+				options = &extra.(*dns.OPT).Option
+				break
+			}
+		}
+	}
+	if options == nil {
+		return nil
+	}
+	prr := dns.EDNS0_SUBNET{}
+	prr.Code = dns.EDNS0SUBNET
+	net := plugin.nets[rand.Intn(len(plugin.nets))]
+	bits, totalSize := net.Mask.Size()
+	if totalSize == 32 {
+		prr.Family = 1
+	} else if totalSize == 128 {
+		prr.Family = 2
+	} else {
+		return nil
+	}
+	prr.SourceNetmask = uint8(bits)
+	prr.SourceScope = 0
+	prr.Address = net.IP
+	*options = append(*options, &prr)
+
+	return nil
+}