From f8e45c13f3c0968b261235c34dc13d309c57de17 Mon Sep 17 00:00:00 2001
From: Eugene Burkov <e.burkov@adguard.com>
Date: Tue, 22 Mar 2022 15:21:03 +0300
Subject: [PATCH] Pull request: 3142 swap arp and rdns priority

Merge in DNS/adguard-home from 3142-fix-clients to master

Updates #3142.
Updates #3597.

Squashed commit of the following:

commit 4dcabedbfb1a4e4a0aaba588f708e4625442fce8
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Mar 22 15:13:15 2022 +0300

    all: imp log of changes

commit 481088d05eecac1109daf378e0b4d5f6b2cf099b
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Mar 22 14:36:44 2022 +0300

    all: swap arp and rdns priority
---
 CHANGELOG.md                      | 2 ++
 internal/dnsforward/dnsforward.go | 4 +++-
 internal/home/clients.go          | 6 ++----
 internal/home/rdns.go             | 8 +++-----
 4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d663d78e..bc986774 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,6 +29,8 @@ and this project adheres to
 
 ### Changed
 
+- Reverse DNS now has a greater priority as the source of runtime clients'
+  informmation than ARP neighborhood.
 - Improved detection of runtime clients through more resilient ARP processing
   ([#3597]).
 - The TTL of responses served from the optimistic cache is now lowered to 10
diff --git a/internal/dnsforward/dnsforward.go b/internal/dnsforward/dnsforward.go
index 48e344b3..a5b0098a 100644
--- a/internal/dnsforward/dnsforward.go
+++ b/internal/dnsforward/dnsforward.go
@@ -314,7 +314,7 @@ func (s *Server) Exchange(ip net.IP) (host string, err error) {
 		StartTime: time.Now(),
 	}
 
-	resolver := s.internalProxy
+	var resolver *proxy.Proxy
 	if s.privateNets.Contains(ip) {
 		if !s.conf.UsePrivateRDNS {
 			return "", nil
@@ -322,6 +322,8 @@ func (s *Server) Exchange(ip net.IP) (host string, err error) {
 
 		resolver = s.localResolvers
 		s.recDetector.add(*req)
+	} else {
+		resolver = s.internalProxy
 	}
 
 	if err = resolver.Resolve(ctx); err != nil {
diff --git a/internal/home/clients.go b/internal/home/clients.go
index d9aad40e..08d70bb9 100644
--- a/internal/home/clients.go
+++ b/internal/home/clients.go
@@ -53,8 +53,8 @@ type clientSource uint
 // Client sources.  The order determines the priority.
 const (
 	ClientSourceWHOIS clientSource = iota
-	ClientSourceRDNS
 	ClientSourceARP
+	ClientSourceRDNS
 	ClientSourceDHCP
 	ClientSourceHostsFile
 )
@@ -723,9 +723,7 @@ func (clients *clientsContainer) AddHost(ip net.IP, host string, src clientSourc
 	clients.lock.Lock()
 	defer clients.lock.Unlock()
 
-	ok = clients.addHostLocked(ip, host, src)
-
-	return ok, nil
+	return clients.addHostLocked(ip, host, src), nil
 }
 
 // addHostLocked adds a new IP-hostname pairing.  For internal use only.
diff --git a/internal/home/rdns.go b/internal/home/rdns.go
index cba748af..7a2d1bcd 100644
--- a/internal/home/rdns.go
+++ b/internal/home/rdns.go
@@ -125,14 +125,12 @@ func (r *RDNS) workerLoop() {
 			log.Debug("rdns: resolving %q: %s", ip, err)
 
 			continue
-		}
-
-		if host == "" {
+		} else if host == "" {
 			continue
 		}
 
-		// Don't handle any errors since AddHost doesn't return non-nil
-		// errors for now.
+		// Don't handle any errors since AddHost doesn't return non-nil errors
+		// for now.
 		_, _ = r.clients.AddHost(ip, host, ClientSourceRDNS)
 	}
 }