From 82505566f87fe10b80b2961456ed0150baed716c Mon Sep 17 00:00:00 2001
From: Eugene Burkov <e.burkov@adguard.com>
Date: Wed, 23 Mar 2022 20:47:45 +0300
Subject: [PATCH] Pull request: 2846 cover aghnet vol.2

Merge in DNS/adguard-home from 2846-cover-aghnet-vol.2 to master

Updates #2846.
Closes #4408.

Squashed commit of the following:

commit 8d62b29d5b5be875cb71e518e479e321d853eb1a
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 20:42:04 2022 +0300

    home: recover panic

commit 1d98109e910830bec712c7aecbbbcb8f659d823d
Merge: ac11d751 9ce2a0fb
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 20:32:05 2022 +0300

    Merge branch 'master' into 2846-cover-aghnet-vol.2

commit ac11d751fb7951e3dd0940bf425a893223c32789
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 20:29:41 2022 +0300

    aghnet: use iotest

commit 7c923df7bafd5d4b91c4b4a01e75ab161944f949
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 20:17:19 2022 +0300

    aghnet: cover more

commit 3bfd4d587e4b887b5527d60c0eb6027da15c7e37
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 14:13:59 2022 +0300

    aghnet: cover arpdb more

commit cd5cf7bbdecceeab6d3abee10a5572e1e907cc67
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 13:05:35 2022 +0300

    all: rm arpdb initial refresh

commit 0fb8d9e44a4d130ca4e8fc2ea5d595ec08555302
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Mar 22 21:13:16 2022 +0300

    aghnet: cover arpdb
---
 internal/aghnet/arpdb.go                      | 11 +---
 internal/aghnet/arpdb_bsd_test.go             |  8 +++
 internal/aghnet/arpdb_linux_test.go           |  7 +++
 internal/aghnet/arpdb_openbsd_test.go         |  2 +
 internal/aghnet/arpdb_test.go                 | 53 +++++++++++++++++++
 internal/aghnet/hostscontainer.go             |  4 +-
 internal/aghnet/net.go                        |  3 +-
 internal/aghnet/net_test.go                   | 25 +++++++++
 internal/aghnet/systemresolvers.go            | 40 ++------------
 internal/aghnet/systemresolvers_others.go     | 23 ++++----
 .../aghnet/systemresolvers_others_test.go     | 21 +++-----
 internal/aghnet/systemresolvers_test.go       | 14 +++--
 internal/aghnet/systemresolvers_windows.go    |  3 +-
 internal/aghnet/testdata/proc_net_arp         |  4 +-
 internal/dnsforward/dnsforward.go             |  2 +-
 internal/home/clients.go                      |  2 +
 internal/home/home.go                         |  9 +---
 17 files changed, 143 insertions(+), 88 deletions(-)

diff --git a/internal/aghnet/arpdb.go b/internal/aghnet/arpdb.go
index 759a688a..afb880c3 100644
--- a/internal/aghnet/arpdb.go
+++ b/internal/aghnet/arpdb.go
@@ -27,15 +27,8 @@ type ARPDB interface {
 }
 
 // NewARPDB returns the ARPDB properly initialized for the OS.
-func NewARPDB() (arp ARPDB, err error) {
-	arp = newARPDB()
-
-	err = arp.Refresh()
-	if err != nil {
-		return nil, fmt.Errorf("arpdb initial refresh: %w", err)
-	}
-
-	return arp, nil
+func NewARPDB() (arp ARPDB) {
+	return newARPDB()
 }
 
 // Empty ARPDB implementation
diff --git a/internal/aghnet/arpdb_bsd_test.go b/internal/aghnet/arpdb_bsd_test.go
index bbadc600..3404af69 100644
--- a/internal/aghnet/arpdb_bsd_test.go
+++ b/internal/aghnet/arpdb_bsd_test.go
@@ -8,8 +8,12 @@ import (
 )
 
 const arpAOutput = `
+invalid.mac (1.2.3.4) at 12:34:56:78:910 on el0 ifscope [ethernet]
+invalid.ip  (1.2.3.4.5) at ab:cd:ef:ab:cd:12 on ek0 ifscope [ethernet]
+invalid.fmt 1 at 12:cd:ef:ab:cd:ef on er0 ifscope [ethernet]
 hostname.one (192.168.1.2) at ab:cd:ef:ab:cd:ef on en0 ifscope [ethernet]
 hostname.two (::ffff:ffff) at ef:cd:ab:ef:cd:ab on em0 expires in 1198 seconds [ethernet]
+? (::1234) at aa:bb:cc:dd:ee:ff on ej0 expires in 1918 seconds [ethernet]
 `
 
 var wantNeighs = []Neighbor{{
@@ -20,4 +24,8 @@ var wantNeighs = []Neighbor{{
 	Name: "hostname.two",
 	IP:   net.ParseIP("::ffff:ffff"),
 	MAC:  net.HardwareAddr{0xEF, 0xCD, 0xAB, 0xEF, 0xCD, 0xAB},
+}, {
+	Name: "",
+	IP:   net.ParseIP("::1234"),
+	MAC:  net.HardwareAddr{0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF},
 }}
diff --git a/internal/aghnet/arpdb_linux_test.go b/internal/aghnet/arpdb_linux_test.go
index 0439c9b5..b9ed859f 100644
--- a/internal/aghnet/arpdb_linux_test.go
+++ b/internal/aghnet/arpdb_linux_test.go
@@ -16,14 +16,21 @@ import (
 
 const arpAOutputWrt = `
 IP address    HW type     Flags       HW address            Mask     Device
+1.2.3.4.5     0x1         0x2         aa:bb:cc:dd:ee:ff     *        wan
+1.2.3.4       0x1         0x2         12:34:56:78:910       *        wan
 192.168.1.2   0x1         0x2         ab:cd:ef:ab:cd:ef     *        wan
 ::ffff:ffff   0x1         0x2         ef:cd:ab:ef:cd:ab     *        wan`
 
 const arpAOutput = `
+invalid.mac (1.2.3.4) at 12:34:56:78:910 on el0 ifscope [ethernet]
+invalid.ip  (1.2.3.4.5) at ab:cd:ef:ab:cd:12 on ek0 ifscope [ethernet]
+invalid.fmt 1 at 12:cd:ef:ab:cd:ef on er0 ifscope [ethernet]
 ? (192.168.1.2) at ab:cd:ef:ab:cd:ef on en0 ifscope [ethernet]
 ? (::ffff:ffff) at ef:cd:ab:ef:cd:ab on em0 expires in 100 seconds [ethernet]`
 
 const ipNeighOutput = `
+1.2.3.4.5 dev enp0s3 lladdr aa:bb:cc:dd:ee:ff DELAY
+1.2.3.4 dev enp0s3 lladdr 12:34:56:78:910 DELAY
 192.168.1.2 dev enp0s3 lladdr ab:cd:ef:ab:cd:ef DELAY
 ::ffff:ffff dev enp0s3 lladdr ef:cd:ab:ef:cd:ab router STALE`
 
diff --git a/internal/aghnet/arpdb_openbsd_test.go b/internal/aghnet/arpdb_openbsd_test.go
index b1021513..915c17ff 100644
--- a/internal/aghnet/arpdb_openbsd_test.go
+++ b/internal/aghnet/arpdb_openbsd_test.go
@@ -9,6 +9,8 @@ import (
 
 const arpAOutput = `
 Host        Ethernet Address  Netif Expire    Flags
+1.2.3.4.5   aa:bb:cc:dd:ee:ff   em0 permanent
+1.2.3.4     12:34:56:78:910     em0 permanent
 192.168.1.2 ab:cd:ef:ab:cd:ef   em0 19m56s
 ::ffff:ffff ef:cd:ab:ef:cd:ab   em0 permanent l
 `
diff --git a/internal/aghnet/arpdb_test.go b/internal/aghnet/arpdb_test.go
index ce3da4fb..aa5c821a 100644
--- a/internal/aghnet/arpdb_test.go
+++ b/internal/aghnet/arpdb_test.go
@@ -6,6 +6,7 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"testing/iotest"
 
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/testutil"
@@ -13,6 +14,15 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestNewARPDB(t *testing.T) {
+	var a ARPDB
+	require.NotPanics(t, func() {
+		a = NewARPDB()
+	})
+
+	assert.NotNil(t, a)
+}
+
 // TestARPDB is the mock implementation of ARPDB to use in tests.
 type TestARPDB struct {
 	OnRefresh   func() (err error)
@@ -166,3 +176,46 @@ func TestCmdARPDB_arpa(t *testing.T) {
 		testutil.AssertErrorMsg(t, "cmd arpdb: running command: can't run", err)
 	})
 }
+
+func TestCmdARPDB_errors(t *testing.T) {
+	const errRead errors.Error = "can't read"
+
+	badReaderRunCmd := runCmdFunc(func() (r io.Reader, err error) {
+		return iotest.ErrReader(errRead), nil
+	})
+
+	a := &cmdARPDB{
+		runcmd: badReaderRunCmd,
+		parse:  parseArpA,
+		ns: &neighs{
+			mu: &sync.RWMutex{},
+			ns: make([]Neighbor, 0),
+		},
+	}
+
+	const wantErrMsg string = "cmd arpdb: scanning the output: " + string(errRead)
+
+	testutil.AssertErrorMsg(t, wantErrMsg, a.Refresh())
+}
+
+func TestEmptyARPDB(t *testing.T) {
+	a := EmptyARPDB{}
+
+	t.Run("refresh", func(t *testing.T) {
+		var err error
+		require.NotPanics(t, func() {
+			err = a.Refresh()
+		})
+
+		assert.NoError(t, err)
+	})
+
+	t.Run("neighbors", func(t *testing.T) {
+		var ns []Neighbor
+		require.NotPanics(t, func() {
+			ns = a.Neighbors()
+		})
+
+		assert.Empty(t, ns)
+	})
+}
diff --git a/internal/aghnet/hostscontainer.go b/internal/aghnet/hostscontainer.go
index 198d4c78..290dc1c0 100644
--- a/internal/aghnet/hostscontainer.go
+++ b/internal/aghnet/hostscontainer.go
@@ -368,8 +368,8 @@ func (hp *hostsParser) addPairs(ip net.IP, hosts []string) {
 	}
 }
 
-// writeRules writes the actual rule for the qtype and the PTR for the
-// host-ip pair into internal builders.
+// writeRules writes the actual rule for the qtype and the PTR for the host-ip
+// pair into internal builders.
 func (hp *hostsParser) writeRules(host string, ip net.IP) (rule, rulePtr string) {
 	arpa, err := netutil.IPToReversedAddr(ip)
 	if err != nil {
diff --git a/internal/aghnet/net.go b/internal/aghnet/net.go
index ecb70fa8..2d791c03 100644
--- a/internal/aghnet/net.go
+++ b/internal/aghnet/net.go
@@ -105,8 +105,7 @@ func GetValidNetInterfacesForWeb() ([]*NetInterface, error) {
 	ifaces, err := net.Interfaces()
 	if err != nil {
 		return nil, fmt.Errorf("couldn't get interfaces: %w", err)
-	}
-	if len(ifaces) == 0 {
+	} else if len(ifaces) == 0 {
 		return nil, errors.Error("couldn't find any legible interface")
 	}
 
diff --git a/internal/aghnet/net_test.go b/internal/aghnet/net_test.go
index 34e99faa..b461cb44 100644
--- a/internal/aghnet/net_test.go
+++ b/internal/aghnet/net_test.go
@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/netutil"
 	"github.com/AdguardTeam/golibs/testutil"
 	"github.com/stretchr/testify/assert"
@@ -130,3 +131,27 @@ func TestCheckPort(t *testing.T) {
 		assert.NoError(t, err)
 	})
 }
+
+func TestCollectAllIfacesAddrs(t *testing.T) {
+	addrs, err := CollectAllIfacesAddrs()
+	require.NoError(t, err)
+
+	assert.NotEmpty(t, addrs)
+}
+
+func TestIsAddrInUse(t *testing.T) {
+	t.Run("addr_in_use", func(t *testing.T) {
+		l, err := net.Listen("tcp", "0.0.0.0:0")
+		require.NoError(t, err)
+		testutil.CleanupAndRequireSuccess(t, l.Close)
+
+		_, err = net.Listen(l.Addr().Network(), l.Addr().String())
+		assert.True(t, IsAddrInUse(err))
+	})
+
+	t.Run("another", func(t *testing.T) {
+		const anotherErr errors.Error = "not addr in use"
+
+		assert.False(t, IsAddrInUse(anotherErr))
+	})
+}
diff --git a/internal/aghnet/systemresolvers.go b/internal/aghnet/systemresolvers.go
index 777127a3..13fbeb32 100644
--- a/internal/aghnet/systemresolvers.go
+++ b/internal/aghnet/systemresolvers.go
@@ -1,11 +1,5 @@
 package aghnet
 
-import (
-	"time"
-
-	"github.com/AdguardTeam/golibs/log"
-)
-
 // DefaultRefreshIvl is the default period of time between refreshing cached
 // addresses.
 // const DefaultRefreshIvl = 5 * time.Minute
@@ -16,39 +10,21 @@ type HostGenFunc func() (host string)
 
 // SystemResolvers helps to work with local resolvers' addresses provided by OS.
 type SystemResolvers interface {
-	// Get returns the slice of local resolvers' addresses.  It should be
-	// safe for concurrent use.
+	// Get returns the slice of local resolvers' addresses.  It must be safe for
+	// concurrent use.
 	Get() (rs []string)
-	// refresh refreshes the local resolvers' addresses cache.  It should be
-	// safe for concurrent use.
+	// refresh refreshes the local resolvers' addresses cache.  It must be safe
+	// for concurrent use.
 	refresh() (err error)
 }
 
-// refreshWithTicker refreshes the cache of sr after each tick form tickCh.
-func refreshWithTicker(sr SystemResolvers, tickCh <-chan time.Time) {
-	defer log.OnPanic("systemResolvers")
-
-	// TODO(e.burkov): Implement a functionality to stop ticker.
-	for range tickCh {
-		err := sr.refresh()
-		if err != nil {
-			log.Error("systemResolvers: error in refreshing goroutine: %s", err)
-
-			continue
-		}
-
-		log.Debug("systemResolvers: local addresses cache is refreshed")
-	}
-}
-
 // NewSystemResolvers returns a SystemResolvers with the cache refresh rate
 // defined by refreshIvl. It disables auto-resfreshing if refreshIvl is 0.  If
 // nil is passed for hostGenFunc, the default generator will be used.
 func NewSystemResolvers(
-	refreshIvl time.Duration,
 	hostGenFunc HostGenFunc,
 ) (sr SystemResolvers, err error) {
-	sr = newSystemResolvers(refreshIvl, hostGenFunc)
+	sr = newSystemResolvers(hostGenFunc)
 
 	// Fill cache.
 	err = sr.refresh()
@@ -56,11 +32,5 @@ func NewSystemResolvers(
 		return nil, err
 	}
 
-	if refreshIvl > 0 {
-		ticker := time.NewTicker(refreshIvl)
-
-		go refreshWithTicker(sr, ticker.C)
-	}
-
 	return sr, nil
 }
diff --git a/internal/aghnet/systemresolvers_others.go b/internal/aghnet/systemresolvers_others.go
index 8acdb6c7..f8afa286 100644
--- a/internal/aghnet/systemresolvers_others.go
+++ b/internal/aghnet/systemresolvers_others.go
@@ -24,12 +24,15 @@ func defaultHostGen() (host string) {
 
 // systemResolvers is a default implementation of SystemResolvers interface.
 type systemResolvers struct {
-	resolver    *net.Resolver
-	hostGenFunc HostGenFunc
-
-	// addrs is the set that contains cached local resolvers' addresses.
-	addrs     *stringutil.Set
+	// addrsLock protects addrs.
 	addrsLock sync.RWMutex
+	// addrs is the set that contains cached local resolvers' addresses.
+	addrs *stringutil.Set
+
+	// resolver is used to fetch the resolvers' addresses.
+	resolver *net.Resolver
+	// hostGenFunc generates hosts to resolve.
+	hostGenFunc HostGenFunc
 }
 
 const (
@@ -44,6 +47,7 @@ const (
 	errUnexpectedHostFormat errors.Error = "unexpected host format"
 )
 
+// refresh implements the SystemResolvers interface for *systemResolvers.
 func (sr *systemResolvers) refresh() (err error) {
 	defer func() { err = errors.Annotate(err, "systemResolvers: %w") }()
 
@@ -56,7 +60,7 @@ func (sr *systemResolvers) refresh() (err error) {
 	return err
 }
 
-func newSystemResolvers(refreshIvl time.Duration, hostGenFunc HostGenFunc) (sr SystemResolvers) {
+func newSystemResolvers(hostGenFunc HostGenFunc) (sr SystemResolvers) {
 	if hostGenFunc == nil {
 		hostGenFunc = defaultHostGen
 	}
@@ -76,19 +80,18 @@ func newSystemResolvers(refreshIvl time.Duration, hostGenFunc HostGenFunc) (sr S
 func validateDialedHost(host string) (err error) {
 	defer func() { err = errors.Annotate(err, "parsing %q: %w", host) }()
 
-	var ipStr string
 	parts := strings.Split(host, "%")
 	switch len(parts) {
 	case 1:
-		ipStr = host
+		// host
 	case 2:
 		// Remove the zone and check the IP address part.
-		ipStr = parts[0]
+		host = parts[0]
 	default:
 		return errUnexpectedHostFormat
 	}
 
-	if net.ParseIP(ipStr) == nil {
+	if _, err = netutil.ParseIP(host); err != nil {
 		return errBadAddrPassed
 	}
 
diff --git a/internal/aghnet/systemresolvers_others_test.go b/internal/aghnet/systemresolvers_others_test.go
index 79abeca2..f7cf9ef0 100644
--- a/internal/aghnet/systemresolvers_others_test.go
+++ b/internal/aghnet/systemresolvers_others_test.go
@@ -6,37 +6,32 @@ package aghnet
 import (
 	"context"
 	"testing"
-	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-func createTestSystemResolversImp(
+func createTestSystemResolversImpl(
 	t *testing.T,
-	refreshDur time.Duration,
 	hostGenFunc HostGenFunc,
 ) (imp *systemResolvers) {
 	t.Helper()
 
-	sr := createTestSystemResolvers(t, refreshDur, hostGenFunc)
+	sr := createTestSystemResolvers(t, hostGenFunc)
+	require.IsType(t, (*systemResolvers)(nil), sr)
 
-	var ok bool
-	imp, ok = sr.(*systemResolvers)
-	require.True(t, ok)
-
-	return imp
+	return sr.(*systemResolvers)
 }
 
 func TestSystemResolvers_Refresh(t *testing.T) {
 	t.Run("expected_error", func(t *testing.T) {
-		sr := createTestSystemResolvers(t, 0, nil)
+		sr := createTestSystemResolvers(t, nil)
 
 		assert.NoError(t, sr.refresh())
 	})
 
 	t.Run("unexpected_error", func(t *testing.T) {
-		_, err := NewSystemResolvers(0, func() string {
+		_, err := NewSystemResolvers(func() string {
 			return "127.0.0.1::123"
 		})
 		assert.Error(t, err)
@@ -44,7 +39,7 @@ func TestSystemResolvers_Refresh(t *testing.T) {
 }
 
 func TestSystemResolvers_DialFunc(t *testing.T) {
-	imp := createTestSystemResolversImp(t, 0, nil)
+	imp := createTestSystemResolversImpl(t, nil)
 
 	testCases := []struct {
 		want    error
@@ -52,7 +47,7 @@ func TestSystemResolvers_DialFunc(t *testing.T) {
 		address string
 	}{{
 		want:    errFakeDial,
-		name:    "valid",
+		name:    "valid_ipv4",
 		address: "127.0.0.1",
 	}, {
 		want:    errFakeDial,
diff --git a/internal/aghnet/systemresolvers_test.go b/internal/aghnet/systemresolvers_test.go
index 13145817..0a19490d 100644
--- a/internal/aghnet/systemresolvers_test.go
+++ b/internal/aghnet/systemresolvers_test.go
@@ -2,7 +2,6 @@ package aghnet
 
 import (
 	"testing"
-	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -10,13 +9,12 @@ import (
 
 func createTestSystemResolvers(
 	t *testing.T,
-	refreshDur time.Duration,
 	hostGenFunc HostGenFunc,
 ) (sr SystemResolvers) {
 	t.Helper()
 
 	var err error
-	sr, err = NewSystemResolvers(refreshDur, hostGenFunc)
+	sr, err = NewSystemResolvers(hostGenFunc)
 	require.NoError(t, err)
 	require.NotNil(t, sr)
 
@@ -24,8 +22,14 @@ func createTestSystemResolvers(
 }
 
 func TestSystemResolvers_Get(t *testing.T) {
-	sr := createTestSystemResolvers(t, 0, nil)
-	assert.NotEmpty(t, sr.Get())
+	sr := createTestSystemResolvers(t, nil)
+
+	var rs []string
+	require.NotPanics(t, func() {
+		rs = sr.Get()
+	})
+
+	assert.NotEmpty(t, rs)
 }
 
 // TODO(e.burkov): Write tests for refreshWithTicker.
diff --git a/internal/aghnet/systemresolvers_windows.go b/internal/aghnet/systemresolvers_windows.go
index 5acdfa85..f82d6e7e 100644
--- a/internal/aghnet/systemresolvers_windows.go
+++ b/internal/aghnet/systemresolvers_windows.go
@@ -11,7 +11,6 @@ import (
 	"os/exec"
 	"strings"
 	"sync"
-	"time"
 
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
@@ -27,7 +26,7 @@ type systemResolvers struct {
 	addrsLock sync.RWMutex
 }
 
-func newSystemResolvers(refreshIvl time.Duration, _ HostGenFunc) (sr SystemResolvers) {
+func newSystemResolvers(_ HostGenFunc) (sr SystemResolvers) {
 	return &systemResolvers{}
 }
 
diff --git a/internal/aghnet/testdata/proc_net_arp b/internal/aghnet/testdata/proc_net_arp
index 07d214e1..8460c8bb 100644
--- a/internal/aghnet/testdata/proc_net_arp
+++ b/internal/aghnet/testdata/proc_net_arp
@@ -1,4 +1,6 @@
 IP address     HW type     Flags       HW address            Mask     Device
 192.168.1.2    0x1         0x2         ab:cd:ef:ab:cd:ef     *        wan
 ::ffff:ffff    0x1         0x0         ef:cd:ab:ef:cd:ab     *        br-lan
-0.0.0.0        0x0         0x0         00:00:00:00:00:00     *        unspec
\ No newline at end of file
+0.0.0.0        0x0         0x0         00:00:00:00:00:00     *        unspec
+1.2.3.4.5      0x1         0x2         aa:bb:cc:dd:ee:ff     *        wan
+1.2.3.4        0x1         0x2         12:34:56:78:910       *        wan
\ No newline at end of file
diff --git a/internal/dnsforward/dnsforward.go b/internal/dnsforward/dnsforward.go
index a5b0098a..c0cd0e55 100644
--- a/internal/dnsforward/dnsforward.go
+++ b/internal/dnsforward/dnsforward.go
@@ -173,7 +173,7 @@ func NewServer(p DNSCreateParams) (s *Server, err error) {
 
 	// TODO(e.burkov): Enable the refresher after the actual implementation
 	// passes the public testing.
-	s.sysResolvers, err = aghnet.NewSystemResolvers(0, nil)
+	s.sysResolvers, err = aghnet.NewSystemResolvers(nil)
 	if err != nil {
 		return nil, fmt.Errorf("initializing system resolvers: %w", err)
 	}
diff --git a/internal/home/clients.go b/internal/home/clients.go
index 9230e565..fe15e514 100644
--- a/internal/home/clients.go
+++ b/internal/home/clients.go
@@ -257,6 +257,8 @@ func (clients *clientsContainer) forConfig() (objs []*clientObject) {
 }
 
 func (clients *clientsContainer) periodicUpdate() {
+	defer log.OnPanic("clients container")
+
 	for {
 		clients.Reload()
 		time.Sleep(clientsUpdatePeriod)
diff --git a/internal/home/home.go b/internal/home/home.go
index 4e4d3aee..5fae42c8 100644
--- a/internal/home/home.go
+++ b/internal/home/home.go
@@ -291,14 +291,7 @@ func setupConfig(args options) (err error) {
 		}
 	}
 
-	var arpdb aghnet.ARPDB
-	arpdb, err = aghnet.NewARPDB()
-	if err != nil {
-		log.Info("warning: creating arpdb: %s; using stub", err)
-
-		arpdb = aghnet.EmptyARPDB{}
-	}
-
+	arpdb := aghnet.NewARPDB()
 	Context.clients.Init(config.Clients, Context.dhcpServer, Context.etcHosts, arpdb)
 
 	if args.bindPort != 0 {