Pull request: 3914 fix lack of client name

Merge in DNS/adguard-home from 3914-fix-client-name to master

Closes #3914.

Squashed commit of the following:

commit 6bd06d277ec5e64fc548245eee75edd8da67fa2c
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Dec 3 17:13:15 2021 +0300

    dnsforward: fix lack of client name

internal/dnsforward/clientid.go

@@ -2,7 +2,6 @@ package dnsforward
 
 import (
 	"crypto/tls"
-	"encoding/binary"
 	"fmt"
 	"path"
 	"strings"
@@ -172,19 +171,3 @@ func (s *Server) clientIDFromDNSContext(pctx *proxy.DNSContext) (clientID string
 
 	return clientID, nil
 }
-
-// processClientID puts the clientID into the DNS context, if there is one.
-func (s *Server) processClientID(dctx *dnsContext) (rc resultCode) {
-	pctx := dctx.proxyCtx
-
-	var key [8]byte
-	binary.BigEndian.PutUint64(key[:], pctx.RequestID)
-	clientIDData := s.clientIDCache.Get(key[:])
-	if clientIDData == nil {
-		return resultCodeSuccess
-	}
-
-	dctx.clientID = string(clientIDData)
-
-	return resultCodeSuccess
-}

internal/dnsforward/dns.go

@@ -1,6 +1,7 @@
 package dnsforward
 
 import (
+	"encoding/binary"
 	"net"
 	"strings"
 	"time"
@@ -86,7 +87,6 @@ func (s *Server) handleDNSRequest(_ *proxy.Proxy, d *proxy.DNSContext) error {
 		s.processInternalHosts,
 		s.processRestrictLocal,
 		s.processInternalIPAddrs,
-		s.processClientID,
 		s.processFilteringBeforeRequest,
 		s.processLocalPTR,
 		s.processUpstream,
@@ -131,7 +131,10 @@ func (s *Server) processRecursion(dctx *dnsContext) (rc resultCode) {
 	return resultCodeSuccess
 }
 
-// Perform initial checks;  process WHOIS & rDNS
+// processInitial terminates the following processing for some requests if
+// needed and enriches the ctx with some client-specific information.
+//
+// TODO(e.burkov):  Decompose into less general processors.
 func (s *Server) processInitial(ctx *dnsContext) (rc resultCode) {
 	d := ctx.proxyCtx
 	if s.conf.AAAADisabled && d.Req.Question[0].Qtype == dns.TypeAAAA {
@@ -151,6 +154,13 @@ func (s *Server) processInitial(ctx *dnsContext) (rc resultCode) {
 		return resultCodeFinish
 	}
 
+	// Get the client's ID if any.  It should be performed before getting
+	// client-specific filtering settings.
+	var key [8]byte
+	binary.BigEndian.PutUint64(key[:], d.RequestID)
+	ctx.clientID = string(s.clientIDCache.Get(key[:]))
+
+	// Get the client-specific filtering settings.
 	ctx.protectionEnabled = s.conf.ProtectionEnabled
 	ctx.setts = s.getClientRequestFilteringSettings(ctx)