Pull request: 2704 local addresses vol.2

Merge in DNS/adguard-home from 2704-local-addresses-vol.2 to master

Updates AdguardTeam#2704.
Updates AdguardTeam#2829.

Squashed commit of the following:

commit 507d038
Author: Eugene Burkov <[email protected]>
Date:   Wed Mar 31 14:33:05 2021 +0300

    aghtest: fix file name

commit 8e19f99
Author: Eugene Burkov <[email protected]>
Date:   Wed Mar 31 14:06:43 2021 +0300

    aghnet: rm redundant mutexes

commit 361fa41
Author: Eugene Burkov <[email protected]>
Date:   Wed Mar 31 13:45:30 2021 +0300

    all: fix names, docs

commit 14034f4
Merge: 35e265c a72ce1c
Author: Eugene Burkov <[email protected]>
Date:   Wed Mar 31 13:38:15 2021 +0300

    Merge branch 'master' into 2704-local-addresses-vol.2

commit 35e265c
Author: Eugene Burkov <[email protected]>
Date:   Wed Mar 31 13:33:35 2021 +0300

    aghnet: imp naming

commit 7a7edac
Author: Eugene Burkov <[email protected]>
Date:   Tue Mar 30 20:59:54 2021 +0300

    changelog: oops, nope yet

commit d26a5d2
Author: Eugene Burkov <[email protected]>
Date:   Tue Mar 30 20:55:53 2021 +0300

    all: some renaming for the glory of semantics

commit 9937fa6
Author: Eugene Burkov <[email protected]>
Date:   Mon Mar 29 15:34:42 2021 +0300

    all: log changes

commit d8d9e6d
Author: Eugene Burkov <[email protected]>
Date:   Fri Mar 26 18:32:23 2021 +0300

    all: imp localresolver, imp cutting off own addresses

commit 344140d
Author: Eugene Burkov <[email protected]>
Date:   Fri Mar 26 14:53:33 2021 +0300

    all: imp code quality

commit 1c5c0ba
Author: Eugene Burkov <[email protected]>
Date:   Thu Mar 25 20:44:08 2021 +0300

    all: fix go.mod

commit 0b9fb3c
Author: Eugene Burkov <[email protected]>
Date:   Thu Mar 25 20:38:51 2021 +0300

    all: add error handling

commit a7a2e51
Merge: c13be63 27f4f05
Author: Eugene Burkov <[email protected]>
Date:   Thu Mar 25 19:48:36 2021 +0300

    Merge branch 'master' into 2704-local-addresses-vol.2

commit c13be63
Author: Eugene Burkov <[email protected]>
Date:   Thu Mar 25 18:52:28 2021 +0300

    all: cover rdns with tests, imp aghnet functionality

commit 48bed90
Author: Eugene Burkov <[email protected]>
Date:   Wed Mar 24 20:18:07 2021 +0300

    home: make rdns great again

commit 1dbacfc
Author: Eugene Burkov <[email protected]>
Date:   Wed Mar 24 16:07:52 2021 +0300

    all: imp external client restriction

commit 1208a31
Author: Eugene Burkov <[email protected]>
Date:   Mon Mar 22 15:26:45 2021 +0300

    all: finish local ptr processor

commit c8827fc
Author: Eugene Burkov <[email protected]>
Date:   Tue Mar 2 13:41:22 2021 +0300

    all: imp ipdetector, add local ptr processor

CHANGELOG.md

@@ -23,6 +23,8 @@ and this project adheres to
 
 ### Changed
 
+- The reverse lookup for local addresses is now performed via local resolvers
+  ([#2704]).
 - Stricter validation of the IP addresses of static leases in the DHCP server
   with regards to the netmask ([#2838]).
 - Stricter validation of `$dnsrewrite` filter modifier parameters ([#2498]).
@@ -50,6 +52,7 @@ and this project adheres to
 [#2498]: https://github.com/AdguardTeam/AdGuardHome/issues/2498
 [#2533]: https://github.com/AdguardTeam/AdGuardHome/issues/2533
 [#2541]: https://github.com/AdguardTeam/AdGuardHome/issues/2541
+[#2704]: https://github.com/AdguardTeam/AdGuardHome/issues/2704
 [#2828]: https://github.com/AdguardTeam/AdGuardHome/issues/2828
 [#2835]: https://github.com/AdguardTeam/AdGuardHome/issues/2835
 [#2838]: https://github.com/AdguardTeam/AdGuardHome/issues/2838

HACKING.md

@@ -188,8 +188,8 @@ on GitHub and most other Markdown renderers. -->
 
  ###  <a id="formatting" href="#formatting">Formatting</a>
 
- *  Add an empty line before `break`, `continue`, `fallthrough`, and `return`,
-    unless it's the only statement in that block.
+ *  Decorate `break`, `continue`, `fallthrough`, `return`, and other function
+    exit points with empty lines unless it's the only statement in that block.
 
  *  Use `gofumpt --extra -s`.
 

internal/aghnet/exchanger.go

@@ -0,0 +1,79 @@
+package aghnet
+
+import (
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/agherr"
+	"github.com/AdguardTeam/dnsproxy/upstream"
+	"github.com/miekg/dns"
+)
+
+// This package is not the best place for this functionality, but we put it here
+// since we need to use it in both rDNS (home) and dnsServer (dnsforward).
+
+// NoUpstreamsErr should be returned when there are no upstreams inside
+// Exchanger implementation.
+const NoUpstreamsErr agherr.Error = "no upstreams specified"
+
+// Exchanger represents an object able to resolve DNS messages.
+//
+// TODO(e.burkov): Maybe expand with method like ExchangeParallel to be able to
+// use user's upstream mode settings.  Also, think about Update method to
+// refresh the internal state.
+type Exchanger interface {
+	Exchange(req *dns.Msg) (resp *dns.Msg, err error)
+}
+
+// multiAddrExchanger is the default implementation of Exchanger interface.
+type multiAddrExchanger struct {
+	ups []upstream.Upstream
+}
+
+// NewMultiAddrExchanger creates an Exchanger instance from passed addresses.
+// It returns an error if any of addrs failed to become an upstream.
+func NewMultiAddrExchanger(addrs []string, timeout time.Duration) (e Exchanger, err error) {
+	defer agherr.Annotate("exchanger: %w", &err)
+
+	if len(addrs) == 0 {
+		return &multiAddrExchanger{}, nil
+	}
+
+	var ups []upstream.Upstream = make([]upstream.Upstream, 0, len(addrs))
+	for _, addr := range addrs {
+		var u upstream.Upstream
+		u, err = upstream.AddressToUpstream(addr, upstream.Options{Timeout: timeout})
+		if err != nil {
+			return nil, err
+		}
+
+		ups = append(ups, u)
+	}
+
+	return &multiAddrExchanger{ups: ups}, nil
+}
+
+// Exсhange performs a query to each resolver until first response.
+func (e *multiAddrExchanger) Exchange(req *dns.Msg) (resp *dns.Msg, err error) {
+	defer agherr.Annotate("exchanger: %w", &err)
+
+	// TODO(e.burkov): Maybe prohibit the initialization without upstreams.
+	if len(e.ups) == 0 {
+		return nil, NoUpstreamsErr
+	}
+
+	var errs []error
+	for _, u := range e.ups {
+		resp, err = u.Exchange(req)
+		if err != nil {
+			errs = append(errs, err)
+
+			continue
+		}
+
+		if resp != nil {
+			return resp, nil
+		}
+	}
+
+	return nil, agherr.Many("can't exchange", errs...)
+}

internal/aghnet/exchanger_test.go

@@ -0,0 +1,64 @@
+package aghnet
+
+import (
+	"testing"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"github.com/AdguardTeam/dnsproxy/upstream"
+	"github.com/miekg/dns"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewMultiAddrExchanger(t *testing.T) {
+	var e Exchanger
+	var err error
+
+	t.Run("empty", func(t *testing.T) {
+		e, err = NewMultiAddrExchanger([]string{}, 0)
+		require.NoError(t, err)
+		assert.NotNil(t, e)
+	})
+
+	t.Run("successful", func(t *testing.T) {
+		e, err = NewMultiAddrExchanger([]string{"www.example.com"}, 0)
+		require.NoError(t, err)
+		assert.NotNil(t, e)
+	})
+
+	t.Run("unsuccessful", func(t *testing.T) {
+		e, err = NewMultiAddrExchanger([]string{"invalid-proto://www.example.com"}, 0)
+		require.Error(t, err)
+		assert.Nil(t, e)
+	})
+}
+
+func TestMultiAddrExchanger_Exchange(t *testing.T) {
+	e := &multiAddrExchanger{}
+
+	t.Run("error", func(t *testing.T) {
+		e.ups = []upstream.Upstream{&aghtest.TestErrUpstream{}}
+
+		resp, err := e.Exchange(nil)
+		require.Error(t, err)
+		assert.Nil(t, resp)
+	})
+
+	t.Run("success", func(t *testing.T) {
+		e.ups = []upstream.Upstream{&aghtest.TestUpstream{
+			Reverse: map[string][]string{
+				"abc": {"cba"},
+			},
+		}}
+
+		resp, err := e.Exchange(&dns.Msg{
+			Question: []dns.Question{{
+				Name:  "abc",
+				Qtype: dns.TypePTR,
+			}},
+		})
+		require.NoError(t, err)
+		require.Len(t, resp.Answer, 1)
+		assert.Equal(t, "cba", resp.Answer[0].Header().Name)
+	})
+}