From d9df7c13becdccc250d43423e81d777aadcae346 Mon Sep 17 00:00:00 2001
From: Eugene Burkov <e.burkov@adguard.com>
Date: Thu, 23 Dec 2021 16:35:10 +0300
Subject: [PATCH] Pull request: 3998 Make hosts rules match exactly

Merge in DNS/adguard-home from 3998-fix-hosts-gen to master

Closes #3998

Squashed commit of the following:

commit b565d51afb6c292dd16accd45b7d37ed386714e8
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 23 16:25:02 2021 +0300

    aghnet: make hosts rules match exactly
---
 internal/aghnet/hostscontainer.go      | 20 ++++++++------------
 internal/aghnet/hostscontainer_test.go | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/internal/aghnet/hostscontainer.go b/internal/aghnet/hostscontainer.go
index 85d6103d..612d2f9f 100644
--- a/internal/aghnet/hostscontainer.go
+++ b/internal/aghnet/hostscontainer.go
@@ -410,11 +410,11 @@ func (hp *hostsParser) writeAliasHostRule(alias, host string) {
 		sc = ";"
 
 		rwSuccess = rules.MaskSeparator + "$dnsrewrite=NOERROR" + sc + "CNAME" + sc
-		constLen  = len(rules.MaskStartURL) + len(rwSuccess) + len(nl)
+		constLen  = len(rules.MaskPipe) + len(rwSuccess) + len(nl)
 	)
 
 	hp.rulesBuilder.Grow(constLen + len(host) + len(alias))
-	stringutil.WriteToBuilder(hp.rulesBuilder, rules.MaskStartURL, alias, rwSuccess, host, nl)
+	stringutil.WriteToBuilder(hp.rulesBuilder, rules.MaskPipe, alias, rwSuccess, host, nl)
 }
 
 // writeMainHostRule writes the actual rule for the qtype and the PTR for the
@@ -431,8 +431,8 @@ func (hp *hostsParser) writeMainHostRule(host string, ip net.IP) (added, addedPt
 		rwSuccess    = "^$dnsrewrite=NOERROR;"
 		rwSuccessPTR = "^$dnsrewrite=NOERROR;PTR;"
 
-		modLen    = len("||") + len(rwSuccess) + len(";")
-		modLenPTR = len("||") + len(rwSuccessPTR)
+		modLen    = len(rules.MaskPipe) + len(rwSuccess) + len(";")
+		modLenPTR = len(rules.MaskPipe) + len(rwSuccessPTR)
 	)
 
 	var qtype string
@@ -451,7 +451,7 @@ func (hp *hostsParser) writeMainHostRule(host string, ip net.IP) (added, addedPt
 	ruleBuilder.Grow(modLen + len(host) + len(qtype) + len(ipStr))
 	stringutil.WriteToBuilder(
 		ruleBuilder,
-		"||",
+		rules.MaskPipe,
 		host,
 		rwSuccess,
 		qtype,
@@ -461,14 +461,10 @@ func (hp *hostsParser) writeMainHostRule(host string, ip net.IP) (added, addedPt
 	added = ruleBuilder.String()
 
 	ruleBuilder.Reset()
+
 	ruleBuilder.Grow(modLenPTR + len(arpa) + len(fqdn))
-	stringutil.WriteToBuilder(
-		ruleBuilder,
-		"||",
-		arpa,
-		rwSuccessPTR,
-		fqdn,
-	)
+	stringutil.WriteToBuilder(ruleBuilder, rules.MaskPipe, arpa, rwSuccessPTR, fqdn)
+
 	addedPtr = ruleBuilder.String()
 
 	hp.rulesBuilder.Grow(len(added) + len(addedPtr) + 2*len(nl))
diff --git a/internal/aghnet/hostscontainer_test.go b/internal/aghnet/hostscontainer_test.go
index 9d2b6a10..e2784908 100644
--- a/internal/aghnet/hostscontainer_test.go
+++ b/internal/aghnet/hostscontainer_test.go
@@ -346,6 +346,24 @@ func TestHostsContainer(t *testing.T) {
 		testTail: func(t *testing.T, res *urlfilter.DNSResult) {
 			assert.Equal(t, "hello", nRewrites(t, res, 1)[0].NewCNAME)
 		},
+	}, {
+		name: "hello_subdomain",
+		req: urlfilter.DNSRequest{
+			Hostname: "say.hello",
+			DNSType:  dns.TypeA,
+		},
+		testTail: func(t *testing.T, res *urlfilter.DNSResult) {
+			assert.Empty(t, res.DNSRewrites())
+		},
+	}, {
+		name: "hello_alias_subdomain",
+		req: urlfilter.DNSRequest{
+			Hostname: "say.hello.world",
+			DNSType:  dns.TypeA,
+		},
+		testTail: func(t *testing.T, res *urlfilter.DNSResult) {
+			assert.Empty(t, res.DNSRewrites())
+		},
 	}, {
 		name: "lots_of_aliases",
 		req: urlfilter.DNSRequest{