From 4fc6bf504e19ff7629c37c6109534b8b342c451c Mon Sep 17 00:00:00 2001
From: Eugene Burkov <e.burkov@adguard.com>
Date: Mon, 18 Dec 2023 14:43:08 +0300
Subject: [PATCH] Pull request 2108: 6541 hosts nodata

Updates #6541.

Squashed commit of the following:

commit e79507f6a7850cc3af316f0e46c289a84882ae15
Merge: 1a09de91d d32832735
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Dec 18 14:29:21 2023 +0300

    Merge branch 'master' into 6541-hosts-nodata

commit 1a09de91dc211e03a104ee7c58b7ea39498b73dd
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 14 18:24:56 2023 +0300

    filtering: separate files

commit e00d1d26c79c85d9266ccdb5e5b4c4a4fde2c90c
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 14 18:00:52 2023 +0300

    filtering: fix hosts nodata
---
 CHANGELOG.md                          |   3 +
 internal/filtering/dnsrewrite_test.go | 170 -----------------------
 internal/filtering/filtering.go       |  79 -----------
 internal/filtering/hosts.go           |  94 +++++++++++++
 internal/filtering/hosts_test.go      | 191 ++++++++++++++++++++++++++
 5 files changed, 288 insertions(+), 249 deletions(-)
 create mode 100644 internal/filtering/hosts.go
 create mode 100644 internal/filtering/hosts_test.go

diff --git a/CHANGELOG.md b/CHANGELOG.md
index afe12018..65f60b6c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,10 +33,13 @@ NOTE: Add new changes BELOW THIS COMMENT.
 
 ### Fixed
 
+- Names defined in the `/etc/hosts` for a single address family wrongly
+  considered undefined for another family ([#6541]).
 - Omitted CNAME records in safe search results, which can cause YouTube to not
   work on iOS ([#6352]).
 
 [#6352]: https://github.com/AdguardTeam/AdGuardHome/issues/6352
+[#6541]: https://github.com/AdguardTeam/AdGuardHome/issues/6541
 [#6545]: https://github.com/AdguardTeam/AdGuardHome/issues/6545
 
 <!--
diff --git a/internal/filtering/dnsrewrite_test.go b/internal/filtering/dnsrewrite_test.go
index 2793697c..06cd921b 100644
--- a/internal/filtering/dnsrewrite_test.go
+++ b/internal/filtering/dnsrewrite_test.go
@@ -1,17 +1,11 @@
 package filtering
 
 import (
-	"fmt"
 	"net/netip"
 	"path"
 	"testing"
-	"testing/fstest"
 
-	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
-	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
 	"github.com/AdguardTeam/golibs/netutil"
-	"github.com/AdguardTeam/golibs/testutil"
-	"github.com/AdguardTeam/urlfilter/rules"
 	"github.com/miekg/dns"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -215,167 +209,3 @@ func TestDNSFilter_CheckHostRules_dnsrewrite(t *testing.T) {
 		assert.Equal(t, "new-ptr-with-dot.", ptr)
 	})
 }
-
-func TestDNSFilter_CheckHost_hostsContainer(t *testing.T) {
-	addrv4 := netip.MustParseAddr("1.2.3.4")
-	addrv6 := netip.MustParseAddr("::1")
-	addrMapped := netip.MustParseAddr("::ffff:1.2.3.4")
-	addrv4Dup := netip.MustParseAddr("4.3.2.1")
-
-	data := fmt.Sprintf(
-		""+
-			"%[1]s v4.host.example\n"+
-			"%[2]s v6.host.example\n"+
-			"%[3]s mapped.host.example\n"+
-			"%[4]s v4.host.with-dup\n"+
-			"%[4]s v4.host.with-dup\n",
-		addrv4,
-		addrv6,
-		addrMapped,
-		addrv4Dup,
-	)
-
-	files := fstest.MapFS{
-		"hosts": &fstest.MapFile{
-			Data: []byte(data),
-		},
-	}
-	watcher := &aghtest.FSWatcher{
-		OnEvents: func() (e <-chan struct{}) { return nil },
-		OnAdd:    func(name string) (err error) { return nil },
-		OnClose:  func() (err error) { return nil },
-	}
-	hc, err := aghnet.NewHostsContainer(files, watcher, "hosts")
-	require.NoError(t, err)
-	testutil.CleanupAndRequireSuccess(t, hc.Close)
-
-	f, _ := newForTest(t, &Config{EtcHosts: hc}, nil)
-	setts := &Settings{
-		FilteringEnabled: true,
-	}
-
-	testCases := []struct {
-		name      string
-		host      string
-		wantRules []*ResultRule
-		wantResps []rules.RRValue
-		dtyp      uint16
-	}{{
-		name: "v4",
-		host: "v4.host.example",
-		dtyp: dns.TypeA,
-		wantRules: []*ResultRule{{
-			Text:         "1.2.3.4 v4.host.example",
-			FilterListID: SysHostsListID,
-		}},
-		wantResps: []rules.RRValue{addrv4},
-	}, {
-		name: "v6",
-		host: "v6.host.example",
-		dtyp: dns.TypeAAAA,
-		wantRules: []*ResultRule{{
-			Text:         "::1 v6.host.example",
-			FilterListID: SysHostsListID,
-		}},
-		wantResps: []rules.RRValue{addrv6},
-	}, {
-		name: "mapped",
-		host: "mapped.host.example",
-		dtyp: dns.TypeAAAA,
-		wantRules: []*ResultRule{{
-			Text:         "::ffff:1.2.3.4 mapped.host.example",
-			FilterListID: SysHostsListID,
-		}},
-		wantResps: []rules.RRValue{addrMapped},
-	}, {
-		name: "ptr",
-		host: "4.3.2.1.in-addr.arpa",
-		dtyp: dns.TypePTR,
-		wantRules: []*ResultRule{{
-			Text:         "1.2.3.4 v4.host.example",
-			FilterListID: SysHostsListID,
-		}},
-		wantResps: []rules.RRValue{"v4.host.example"},
-	}, {
-		name: "ptr-mapped",
-		host: "4.0.3.0.2.0.1.0.f.f.f.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa",
-		dtyp: dns.TypePTR,
-		wantRules: []*ResultRule{{
-			Text:         "::ffff:1.2.3.4 mapped.host.example",
-			FilterListID: SysHostsListID,
-		}},
-		wantResps: []rules.RRValue{"mapped.host.example"},
-	}, {
-		name:      "not_found_v4",
-		host:      "non.existent.example",
-		dtyp:      dns.TypeA,
-		wantRules: nil,
-		wantResps: nil,
-	}, {
-		name:      "not_found_v6",
-		host:      "non.existent.example",
-		dtyp:      dns.TypeAAAA,
-		wantRules: nil,
-		wantResps: nil,
-	}, {
-		name:      "not_found_ptr",
-		host:      "4.3.2.2.in-addr.arpa",
-		dtyp:      dns.TypePTR,
-		wantRules: nil,
-		wantResps: nil,
-	}, {
-		name:      "v4_mismatch",
-		host:      "v4.host.example",
-		dtyp:      dns.TypeAAAA,
-		wantRules: nil,
-		wantResps: nil,
-	}, {
-		name:      "v6_mismatch",
-		host:      "v6.host.example",
-		dtyp:      dns.TypeA,
-		wantRules: nil,
-		wantResps: nil,
-	}, {
-		name:      "wrong_ptr",
-		host:      "4.3.2.1.ip6.arpa",
-		dtyp:      dns.TypePTR,
-		wantRules: nil,
-		wantResps: nil,
-	}, {
-		name:      "unsupported_type",
-		host:      "v4.host.example",
-		dtyp:      dns.TypeCNAME,
-		wantRules: nil,
-		wantResps: nil,
-	}, {
-		name: "v4_dup",
-		host: "v4.host.with-dup",
-		dtyp: dns.TypeA,
-		wantRules: []*ResultRule{{
-			Text:         "4.3.2.1 v4.host.with-dup",
-			FilterListID: SysHostsListID,
-		}},
-		wantResps: []rules.RRValue{addrv4Dup},
-	}}
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			var res Result
-			res, err = f.CheckHost(tc.host, tc.dtyp, setts)
-			require.NoError(t, err)
-
-			if len(tc.wantRules) == 0 {
-				assert.Empty(t, res.Rules)
-				assert.Nil(t, res.DNSRewriteResult)
-
-				return
-			}
-
-			require.NotNil(t, res.DNSRewriteResult)
-			require.Contains(t, res.DNSRewriteResult.Response, tc.dtyp)
-
-			assert.Equal(t, tc.wantResps, res.DNSRewriteResult.Response[tc.dtyp])
-			assert.Equal(t, tc.wantRules, res.Rules)
-		})
-	}
-}
diff --git a/internal/filtering/filtering.go b/internal/filtering/filtering.go
index d54b0d35..2d382530 100644
--- a/internal/filtering/filtering.go
+++ b/internal/filtering/filtering.go
@@ -23,7 +23,6 @@ import (
 	"github.com/AdguardTeam/golibs/hostsfile"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/mathutil"
-	"github.com/AdguardTeam/golibs/netutil"
 	"github.com/AdguardTeam/golibs/stringutil"
 	"github.com/AdguardTeam/golibs/syncutil"
 	"github.com/AdguardTeam/urlfilter"
@@ -618,84 +617,6 @@ func (d *DNSFilter) CheckHost(
 	return Result{}, nil
 }
 
-// matchSysHosts tries to match the host against the operating system's hosts
-// database.  err is always nil.
-func (d *DNSFilter) matchSysHosts(
-	host string,
-	qtype uint16,
-	setts *Settings,
-) (res Result, err error) {
-	// TODO(e.burkov):  Where else is this checked?
-	if !setts.FilteringEnabled || d.conf.EtcHosts == nil {
-		return Result{}, nil
-	}
-
-	vals, rs := hostsRewrites(qtype, host, d.conf.EtcHosts)
-	if len(vals) > 0 {
-		res.DNSRewriteResult = &DNSRewriteResult{
-			Response: DNSRewriteResultResponse{
-				qtype: vals,
-			},
-			RCode: dns.RcodeSuccess,
-		}
-		res.Rules = rs
-		res.Reason = RewrittenAutoHosts
-	}
-
-	return res, nil
-}
-
-// hostsRewrites returns values and rules matched by qt and host within hs.
-func hostsRewrites(
-	qtype uint16,
-	host string,
-	hs hostsfile.Storage,
-) (vals []rules.RRValue, rs []*ResultRule) {
-	var isValidProto func(netip.Addr) (ok bool)
-	switch qtype {
-	case dns.TypeA:
-		isValidProto = netip.Addr.Is4
-	case dns.TypeAAAA:
-		isValidProto = netip.Addr.Is6
-	case dns.TypePTR:
-		// TODO(e.burkov):  Add some [netip]-aware alternative to [netutil].
-		ip, err := netutil.IPFromReversedAddr(host)
-		if err != nil {
-			log.Debug("filtering: failed to parse PTR record %q: %s", host, err)
-
-			return nil, nil
-		}
-
-		addr, _ := netip.AddrFromSlice(ip)
-
-		for _, name := range hs.ByAddr(addr) {
-			vals = append(vals, name)
-			rs = append(rs, &ResultRule{
-				Text:         fmt.Sprintf("%s %s", addr, name),
-				FilterListID: SysHostsListID,
-			})
-		}
-
-		return vals, rs
-	default:
-		log.Debug("filtering: unsupported qtype %d", qtype)
-
-		return nil, nil
-	}
-
-	for _, addr := range hs.ByName(host) {
-		if isValidProto(addr) {
-			vals = append(vals, addr)
-			rs = append(rs, &ResultRule{
-				Text:         fmt.Sprintf("%s %s", addr, host),
-				FilterListID: SysHostsListID,
-			})
-		}
-	}
-
-	return vals, rs
-}
-
 // processRewrites performs filtering based on the legacy rewrite records.
 //
 // Firstly, it finds CNAME rewrites for host.  If the CNAME is the same as host,
diff --git a/internal/filtering/hosts.go b/internal/filtering/hosts.go
new file mode 100644
index 00000000..2f747669
--- /dev/null
+++ b/internal/filtering/hosts.go
@@ -0,0 +1,94 @@
+package filtering
+
+import (
+	"fmt"
+	"net/netip"
+
+	"github.com/AdguardTeam/golibs/hostsfile"
+	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/netutil"
+	"github.com/AdguardTeam/urlfilter/rules"
+	"github.com/miekg/dns"
+)
+
+// matchSysHosts tries to match the host against the operating system's hosts
+// database.  err is always nil.
+func (d *DNSFilter) matchSysHosts(
+	host string,
+	qtype uint16,
+	setts *Settings,
+) (res Result, err error) {
+	// TODO(e.burkov):  Where else is this checked?
+	if !setts.FilteringEnabled || d.conf.EtcHosts == nil {
+		return Result{}, nil
+	}
+
+	vals, rs, matched := hostsRewrites(qtype, host, d.conf.EtcHosts)
+	if !matched {
+		return Result{}, nil
+	}
+
+	return Result{
+		DNSRewriteResult: &DNSRewriteResult{
+			Response: DNSRewriteResultResponse{
+				qtype: vals,
+			},
+			RCode: dns.RcodeSuccess,
+		},
+		Rules:  rs,
+		Reason: RewrittenAutoHosts,
+	}, nil
+}
+
+// hostsRewrites returns values and rules matched by qt and host within hs.
+func hostsRewrites(
+	qtype uint16,
+	host string,
+	hs hostsfile.Storage,
+) (vals []rules.RRValue, rls []*ResultRule, matched bool) {
+	var isValidProto func(netip.Addr) (ok bool)
+	switch qtype {
+	case dns.TypeA:
+		isValidProto = netip.Addr.Is4
+	case dns.TypeAAAA:
+		isValidProto = netip.Addr.Is6
+	case dns.TypePTR:
+		// TODO(e.burkov):  Add some [netip]-aware alternative to [netutil].
+		ip, err := netutil.IPFromReversedAddr(host)
+		if err != nil {
+			log.Debug("filtering: failed to parse PTR record %q: %s", host, err)
+
+			return nil, nil, false
+		}
+
+		addr, _ := netip.AddrFromSlice(ip)
+		names := hs.ByAddr(addr)
+
+		for _, name := range names {
+			vals = append(vals, name)
+			rls = append(rls, &ResultRule{
+				Text:         fmt.Sprintf("%s %s", addr, name),
+				FilterListID: SysHostsListID,
+			})
+		}
+
+		return vals, rls, len(names) > 0
+	default:
+		log.Debug("filtering: unsupported qtype %d", qtype)
+
+		return nil, nil, false
+	}
+
+	addrs := hs.ByName(host)
+	for _, addr := range addrs {
+		if isValidProto(addr) {
+			vals = append(vals, addr)
+		}
+		rls = append(rls, &ResultRule{
+			Text:         fmt.Sprintf("%s %s", addr, host),
+			FilterListID: SysHostsListID,
+		})
+	}
+
+	return vals, rls, len(addrs) > 0
+}
diff --git a/internal/filtering/hosts_test.go b/internal/filtering/hosts_test.go
new file mode 100644
index 00000000..baa6675c
--- /dev/null
+++ b/internal/filtering/hosts_test.go
@@ -0,0 +1,191 @@
+package filtering
+
+import (
+	"fmt"
+	"net/netip"
+	"testing"
+	"testing/fstest"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
+	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"github.com/AdguardTeam/golibs/testutil"
+	"github.com/AdguardTeam/urlfilter/rules"
+	"github.com/miekg/dns"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDNSFilter_CheckHost_hostsContainer(t *testing.T) {
+	addrv4 := netip.MustParseAddr("1.2.3.4")
+	addrv6 := netip.MustParseAddr("::1")
+	addrMapped := netip.MustParseAddr("::ffff:1.2.3.4")
+	addrv4Dup := netip.MustParseAddr("4.3.2.1")
+
+	data := fmt.Sprintf(
+		""+
+			"%[1]s v4.host.example\n"+
+			"%[2]s v6.host.example\n"+
+			"%[3]s mapped.host.example\n"+
+			"%[4]s v4.host.with-dup\n"+
+			"%[4]s v4.host.with-dup\n",
+		addrv4,
+		addrv6,
+		addrMapped,
+		addrv4Dup,
+	)
+
+	files := fstest.MapFS{
+		"hosts": &fstest.MapFile{
+			Data: []byte(data),
+		},
+	}
+	watcher := &aghtest.FSWatcher{
+		OnEvents: func() (e <-chan struct{}) { return nil },
+		OnAdd:    func(name string) (err error) { return nil },
+		OnClose:  func() (err error) { return nil },
+	}
+	hc, err := aghnet.NewHostsContainer(files, watcher, "hosts")
+	require.NoError(t, err)
+	testutil.CleanupAndRequireSuccess(t, hc.Close)
+
+	conf := &Config{
+		EtcHosts: hc,
+	}
+	f, err := New(conf, nil)
+	require.NoError(t, err)
+
+	setts := &Settings{
+		FilteringEnabled: true,
+	}
+
+	testCases := []struct {
+		name      string
+		host      string
+		wantRules []*ResultRule
+		wantResps []rules.RRValue
+		dtyp      uint16
+	}{{
+		name: "v4",
+		host: "v4.host.example",
+		dtyp: dns.TypeA,
+		wantRules: []*ResultRule{{
+			Text:         "1.2.3.4 v4.host.example",
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: []rules.RRValue{addrv4},
+	}, {
+		name: "v6",
+		host: "v6.host.example",
+		dtyp: dns.TypeAAAA,
+		wantRules: []*ResultRule{{
+			Text:         "::1 v6.host.example",
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: []rules.RRValue{addrv6},
+	}, {
+		name: "mapped",
+		host: "mapped.host.example",
+		dtyp: dns.TypeAAAA,
+		wantRules: []*ResultRule{{
+			Text:         "::ffff:1.2.3.4 mapped.host.example",
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: []rules.RRValue{addrMapped},
+	}, {
+		name: "ptr",
+		host: "4.3.2.1.in-addr.arpa",
+		dtyp: dns.TypePTR,
+		wantRules: []*ResultRule{{
+			Text:         "1.2.3.4 v4.host.example",
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: []rules.RRValue{"v4.host.example"},
+	}, {
+		name: "ptr-mapped",
+		host: "4.0.3.0.2.0.1.0.f.f.f.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa",
+		dtyp: dns.TypePTR,
+		wantRules: []*ResultRule{{
+			Text:         "::ffff:1.2.3.4 mapped.host.example",
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: []rules.RRValue{"mapped.host.example"},
+	}, {
+		name:      "not_found_v4",
+		host:      "non.existent.example",
+		dtyp:      dns.TypeA,
+		wantRules: nil,
+		wantResps: nil,
+	}, {
+		name:      "not_found_v6",
+		host:      "non.existent.example",
+		dtyp:      dns.TypeAAAA,
+		wantRules: nil,
+		wantResps: nil,
+	}, {
+		name:      "not_found_ptr",
+		host:      "4.3.2.2.in-addr.arpa",
+		dtyp:      dns.TypePTR,
+		wantRules: nil,
+		wantResps: nil,
+	}, {
+		name: "v4_mismatch",
+		host: "v4.host.example",
+		dtyp: dns.TypeAAAA,
+		wantRules: []*ResultRule{{
+			Text:         fmt.Sprintf("%s v4.host.example", addrv4),
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: nil,
+	}, {
+		name: "v6_mismatch",
+		host: "v6.host.example",
+		dtyp: dns.TypeA,
+		wantRules: []*ResultRule{{
+			Text:         fmt.Sprintf("%s v6.host.example", addrv6),
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: nil,
+	}, {
+		name:      "wrong_ptr",
+		host:      "4.3.2.1.ip6.arpa",
+		dtyp:      dns.TypePTR,
+		wantRules: nil,
+		wantResps: nil,
+	}, {
+		name:      "unsupported_type",
+		host:      "v4.host.example",
+		dtyp:      dns.TypeCNAME,
+		wantRules: nil,
+		wantResps: nil,
+	}, {
+		name: "v4_dup",
+		host: "v4.host.with-dup",
+		dtyp: dns.TypeA,
+		wantRules: []*ResultRule{{
+			Text:         "4.3.2.1 v4.host.with-dup",
+			FilterListID: SysHostsListID,
+		}},
+		wantResps: []rules.RRValue{addrv4Dup},
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var res Result
+			res, err = f.CheckHost(tc.host, tc.dtyp, setts)
+			require.NoError(t, err)
+
+			if len(tc.wantRules) == 0 {
+				assert.Empty(t, res.Rules)
+				assert.Nil(t, res.DNSRewriteResult)
+
+				return
+			}
+
+			require.NotNil(t, res.DNSRewriteResult)
+			require.Contains(t, res.DNSRewriteResult.Response, tc.dtyp)
+
+			assert.Equal(t, tc.wantResps, res.DNSRewriteResult.Response[tc.dtyp])
+			assert.Equal(t, tc.wantRules, res.Rules)
+		})
+	}
+}