Pull request: 2846 cover aghnet vol.3

Merge in DNS/adguard-home from 2846-cover-aghnet-vol.3 to master

Updates #2846.

Squashed commit of the following:

commit cb22987c43c17bbc8d098e65639cc84e2284bc7b
Merge: cf995e9d f31ffcc5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 30 15:01:10 2022 +0300

    Merge branch 'master' into 2846-cover-aghnet-vol.3

commit cf995e9dce635f16e10406a61e2ab12f06407f1f
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 18:29:50 2022 +0300

    aghnet: imp tests

commit bc225fe8800633b29216840bc7d5b82d7c2d2bfb
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 18:03:06 2022 +0300

    aghnet: imp tests

commit a82eb6045495b94a2e81ced9a3ef5bfe65788e56
Merge: f8081249 0d562a7b
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 17:39:13 2022 +0300

    Merge branch 'master' into 2846-cover-aghnet-vol.3

commit f80812490c49f69655d409c6f015b069affa2f19
Merge: edccaa79 3603b1fc
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 17:29:20 2022 +0300

    Merge branch 'master' into 2846-cover-aghnet-vol.3

commit edccaa79fca061ffeea1985c293eed123b16a09c
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 13:53:40 2022 +0300

    aghnet: imp tests

commit 7c5028c92f0a6680516bda67c73e794182c9b825
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Mar 25 18:01:28 2022 +0300

    aghnet: imp code & docs

commit 7897c6b13e9be340ae8a71947a8a0bab82c682eb
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Mar 25 17:11:46 2022 +0300

    aghnet: imp coverage

commit 1eef110af3bf721a0275c695bf27c31815abff04
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 21:10:29 2022 +0300

    all: return byte slice

internal/aghnet/arpdb.go

@@ -2,13 +2,11 @@ package aghnet
 
 import (
 	"bufio"
+	"bytes"
 	"fmt"
-	"io"
 	"net"
-	"strings"
 	"sync"
 
-	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/netutil"
 )
@@ -116,50 +114,33 @@ func (ns *neighs) reset(with []Neighbor) {
 // of Neighbors.
 type parseNeighsFunc func(sc *bufio.Scanner, lenHint int) (ns []Neighbor)
 
-// runCmdFunc is the function that runs some command and returns its output
-// wrapped to be a io.Reader.
-type runCmdFunc func() (r io.Reader, err error)
-
 // cmdARPDB is the implementation of the ARPDB that uses command line to
 // retrieve data.
 type cmdARPDB struct {
 	parse parseNeighsFunc
-	runcmd runCmdFunc
 	ns    *neighs
+	cmd   string
+	args  []string
 }
 
 // type check
 var _ ARPDB = (*cmdARPDB)(nil)
 
-// runCmd runs the cmd with it's args and returns the result wrapped to be an
-// io.Reader.  The error is returned either if the exit code retured by command
-// not equals 0 or the execution itself failed.
-func runCmd(cmd string, args ...string) (r io.Reader, err error) {
-	var code int
-	var out string
-	code, out, err = aghos.RunCommand(cmd, args...)
-	if err != nil {
-		return nil, err
-	} else if code != 0 {
-		return nil, fmt.Errorf("unexpected exit code %d", code)
-	}
-
-	return strings.NewReader(out), nil
-}
-
 // Refresh implements the ARPDB interface for *cmdARPDB.
 func (arp *cmdARPDB) Refresh() (err error) {
 	defer func() { err = errors.Annotate(err, "cmd arpdb: %w") }()
 
-	var r io.Reader
+	code, out, err := aghosRunCommand(arp.cmd, arp.args...)
-	r, err = arp.runcmd()
 	if err != nil {
 		return fmt.Errorf("running command: %w", err)
+	} else if code != 0 {
+		return fmt.Errorf("running command: unexpected exit code %d", code)
 	}
 
-	sc := bufio.NewScanner(r)
+	sc := bufio.NewScanner(bytes.NewReader(out))
 	ns := arp.parse(sc, arp.ns.len())
 	if err = sc.Err(); err != nil {
+		// TODO(e.burkov):  This error seems unreachable.  Investigate.
 		return fmt.Errorf("scanning the output: %w", err)
 	}
 
@@ -180,8 +161,7 @@ func (arp *cmdARPDB) Neighbors() (ns []Neighbor) {
 type arpdbs struct {
 	// arps is the set of ARPDB implementations to range through.
 	arps []ARPDB
-	// last is the last succeeded ARPDB index.
+	neighs
-	last int
 }
 
 // newARPDBs returns a properly initialized *arpdbs.  It begins refreshing from
@@ -189,7 +169,10 @@ type arpdbs struct {
 func newARPDBs(arps ...ARPDB) (arp *arpdbs) {
 	return &arpdbs{
 		arps: arps,
-		last: 0,
+		neighs: neighs{
+			mu: &sync.RWMutex{},
+			ns: make([]Neighbor, 0),
+		},
 	}
 }
 
@@ -199,20 +182,18 @@ var _ ARPDB = (*arpdbs)(nil)
 // Refresh implements the ARPDB interface for *arpdbs.
 func (arp *arpdbs) Refresh() (err error) {
 	var errs []error
-	l := len(arp.arps)
-	// Start from the last succeeded implementation.
-	for i := 0; i < l; i++ {
-		cur := (arp.last + i) % l
-		err = arp.arps[cur].Refresh()
-		if err == nil {
-			// The succeeded implementation found so update the last succeeded
-			// index.
-			arp.last = cur
 
-			return nil
+	for _, a := range arp.arps {
+		err = a.Refresh()
+		if err != nil {
+			errs = append(errs, err)
+
+			continue
 		}
 
-		errs = append(errs, err)
+		arp.reset(a.Neighbors())
+
+		return nil
 	}
 
 	if len(errs) > 0 {
@@ -223,10 +204,8 @@ func (arp *arpdbs) Refresh() (err error) {
 }
 
 // Neighbors implements the ARPDB interface for *arpdbs.
+//
+// TODO(e.burkov):  Think of a way to avoid cloning the slice twice.
 func (arp *arpdbs) Neighbors() (ns []Neighbor) {
-	if l := len(arp.arps); l > 0 && arp.last < l {
+	return arp.clone()
-		return arp.arps[arp.last].Neighbors()
-	}
-
-	return nil
 }

internal/aghnet/arpdb_bsd.go

@@ -16,11 +16,12 @@ import (
 func newARPDB() *cmdARPDB {
 	return &cmdARPDB{
 		parse: parseArpA,
-		runcmd: rcArpA,
 		ns: &neighs{
 			mu: &sync.RWMutex{},
 			ns: make([]Neighbor, 0),
 		},
+		cmd:  "arp",
+		args: []string{"-a"},
 	}
 }
 

internal/aghnet/arpdb_linux.go

@@ -6,7 +6,6 @@ package aghnet
 import (
 	"bufio"
 	"fmt"
-	"io"
 	"io/fs"
 	"net"
 	"strings"
@@ -34,11 +33,25 @@ func newARPDB() (arp *arpdbs) {
 
 	return newARPDBs(
 		// Try /proc/net/arp first.
-		&fsysARPDB{ns: ns, fsys: aghos.RootDirFS(), filename: "proc/net/arp"},
+		&fsysARPDB{
-		// Try "arp -a" then.
+			ns:       ns,
-		&cmdARPDB{parse: parseF, runcmd: rcArpA, ns: ns},
+			fsys:     rootDirFS,
-		// Try "ip neigh" finally.
+			filename: "proc/net/arp",
-		&cmdARPDB{parse: parseIPNeigh, runcmd: rcIPNeigh, ns: ns},
+		},
+		// Then, try "arp -a".
+		&cmdARPDB{
+			parse: parseF,
+			ns:    ns,
+			cmd:   "arp",
+			args:  []string{"-a"},
+		},
+		// Finally, try "ip neigh".
+		&cmdARPDB{
+			parse: parseIPNeigh,
+			ns:    ns,
+			cmd:   "ip",
+			args:  []string{"neigh"},
+		},
 	)
 }
 
@@ -187,11 +200,6 @@ func parseArpA(sc *bufio.Scanner, lenHint int) (ns []Neighbor) {
 	return ns
 }
 
-// rcIPNeigh runs "ip neigh".
-func rcIPNeigh() (r io.Reader, err error) {
-	return runCmd("ip", "neigh")
-}
-
 // parseIPNeigh parses the output of the "ip neigh" command on Linux.  The
 // expected input format:
 //

internal/aghnet/arpdb_linux_test.go

@@ -4,11 +4,10 @@
 package aghnet
 
 import (
-	"io"
 	"net"
-	"strings"
 	"sync"
 	"testing"
+	"testing/fstest"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -43,6 +42,8 @@ var wantNeighs = []Neighbor{{
 }}
 
 func TestFSysARPDB(t *testing.T) {
+	require.NoError(t, fstest.TestFS(testdata, "proc_net_arp"))
+
 	a := &fsysARPDB{
 		ns: &neighs{
 			mu: &sync.RWMutex{},
@@ -59,10 +60,18 @@ func TestFSysARPDB(t *testing.T) {
 	assert.Equal(t, wantNeighs, ns)
 }
 
-func TestCmdARPDB_arpawrt(t *testing.T) {
+func TestCmdARPDB_linux(t *testing.T) {
+	sh := mapShell{
+		"arp -a":   {err: nil, out: arpAOutputWrt, code: 0},
+		"ip neigh": {err: nil, out: ipNeighOutput, code: 0},
+	}
+	substShell(t, sh.RunCmd)
+
+	t.Run("wrt", func(t *testing.T) {
 		a := &cmdARPDB{
 			parse: parseArpAWrt,
-		runcmd: func() (r io.Reader, err error) { return strings.NewReader(arpAOutputWrt), nil },
+			cmd:   "arp",
+			args:  []string{"-a"},
 			ns: &neighs{
 				mu: &sync.RWMutex{},
 				ns: make([]Neighbor, 0),
@@ -73,12 +82,13 @@ func TestCmdARPDB_arpawrt(t *testing.T) {
 		require.NoError(t, err)
 
 		assert.Equal(t, wantNeighs, a.Neighbors())
-}
+	})
 
-func TestCmdARPDB_ipneigh(t *testing.T) {
+	t.Run("ip_neigh", func(t *testing.T) {
 		a := &cmdARPDB{
 			parse: parseIPNeigh,
-		runcmd: func() (r io.Reader, err error) { return strings.NewReader(ipNeighOutput), nil },
+			cmd:   "ip",
+			args:  []string{"neigh"},
 			ns: &neighs{
 				mu: &sync.RWMutex{},
 				ns: make([]Neighbor, 0),
@@ -88,4 +98,5 @@ func TestCmdARPDB_ipneigh(t *testing.T) {
 		require.NoError(t, err)
 
 		assert.Equal(t, wantNeighs, a.Neighbors())
+	})
 }

internal/aghnet/arpdb_openbsd.go

@@ -14,12 +14,13 @@ import (
 
 func newARPDB() *cmdARPDB {
 	return &cmdARPDB{
-		runcmd: rcArpA,
 		parse: parseArpA,
 		ns: &neighs{
 			mu: &sync.RWMutex{},
 			ns: make([]Neighbor, 0),
 		},
+		cmd:  "arp",
+		args: []string{"-a"},
 	}
 }
 

internal/aghnet/arpdb_test.go

@@ -1,12 +1,9 @@
 package aghnet
 
 import (
-	"io"
 	"net"
-	"strings"
 	"sync"
 	"testing"
-	"testing/iotest"
 
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/testutil"
@@ -16,9 +13,7 @@ import (
 
 func TestNewARPDB(t *testing.T) {
 	var a ARPDB
-	require.NotPanics(t, func() {
+	require.NotPanics(t, func() { a = NewARPDB() })
-		a = NewARPDB()
-	})
 
 	assert.NotNil(t, a)
 }
@@ -135,11 +130,11 @@ func TestARPDBS(t *testing.T) {
 		assert.Equal(t, 1, succRefrCount)
 		assert.NotEmpty(t, a.Neighbors())
 
-		// Only the last succeeded ARPDB should be used.
+		// Unstable ARPDB should refresh successfully again.
 		err = a.Refresh()
 		require.NoError(t, err)
 
-		assert.Equal(t, 2, succRefrCount)
+		assert.Equal(t, 1, succRefrCount)
 		assert.NotEmpty(t, a.Neighbors())
 	})
 
@@ -153,6 +148,7 @@ func TestARPDBS(t *testing.T) {
 
 func TestCmdARPDB_arpa(t *testing.T) {
 	a := &cmdARPDB{
+		cmd:   "cmd",
 		parse: parseArpA,
 		ns: &neighs{
 			mu: &sync.RWMutex{},
@@ -161,7 +157,8 @@ func TestCmdARPDB_arpa(t *testing.T) {
 	}
 
 	t.Run("arp_a", func(t *testing.T) {
-		a.runcmd = func() (r io.Reader, err error) { return strings.NewReader(arpAOutput), nil }
+		sh := theOnlyCmd("cmd", 0, arpAOutput, nil)
+		substShell(t, sh.RunCmd)
 
 		err := a.Refresh()
 		require.NoError(t, err)
@@ -170,32 +167,20 @@ func TestCmdARPDB_arpa(t *testing.T) {
 	})
 
 	t.Run("runcmd_error", func(t *testing.T) {
-		a.runcmd = func() (r io.Reader, err error) { return nil, errors.Error("can't run") }
+		sh := theOnlyCmd("cmd", 0, "", errors.Error("can't run"))
+		substShell(t, sh.RunCmd)
 
 		err := a.Refresh()
 		testutil.AssertErrorMsg(t, "cmd arpdb: running command: can't run", err)
 	})
-}
 
-func TestCmdARPDB_errors(t *testing.T) {
+	t.Run("bad_code", func(t *testing.T) {
-	const errRead errors.Error = "can't read"
+		sh := theOnlyCmd("cmd", 1, "", nil)
+		substShell(t, sh.RunCmd)
 
-	badReaderRunCmd := runCmdFunc(func() (r io.Reader, err error) {
+		err := a.Refresh()
-		return iotest.ErrReader(errRead), nil
+		testutil.AssertErrorMsg(t, "cmd arpdb: running command: unexpected exit code 1", err)
 	})
-
-	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) {

internal/aghnet/arpdb_unix.go

@@ -1,13 +0,0 @@
-//go:build !windows
-// +build !windows
-
-package aghnet
-
-import (
-	"io"
-)
-
-// rcArpA runs "arp -a".
-func rcArpA() (r io.Reader, err error) {
-	return runCmd("arp", "-a")
-}

internal/aghnet/arpdb_windows.go

@@ -5,7 +5,6 @@ package aghnet
 
 import (
 	"bufio"
-	"io"
 	"net"
 	"strings"
 	"sync"
@@ -13,20 +12,16 @@ import (
 
 func newARPDB() *cmdARPDB {
 	return &cmdARPDB{
-		runcmd: rcArpA,
+		parse: parseArpA,
 		ns: &neighs{
 			mu: &sync.RWMutex{},
 			ns: make([]Neighbor, 0),
 		},
-		parse: parseArpA,
+		cmd:  "arp",
+		args: []string{"/a"},
 	}
 }
 
-// rcArpA runs "arp /a".
-func rcArpA() (r io.Reader, err error) {
-	return runCmd("arp", "/a")
-}
-
 // parseArpA parses the output of the "arp /a" command on Windows.  The expected
 // input format (the first line is empty):
 //

internal/aghnet/hostscontainer_test.go

@@ -286,6 +286,8 @@ func TestHostsContainer_Translate(t *testing.T) {
 		OnClose:  func() (err error) { panic("not implemented") },
 	}
 
+	require.NoError(t, fstest.TestFS(testdata, "etc_hosts"))
+
 	hc, err := NewHostsContainer(0, testdata, &stubWatcher, "etc_hosts")
 	require.NoError(t, err)
 	testutil.CleanupAndRequireSuccess(t, hc.Close)
@@ -358,6 +360,8 @@ func TestHostsContainer_Translate(t *testing.T) {
 func TestHostsContainer(t *testing.T) {
 	const listID = 1234
 
+	require.NoError(t, fstest.TestFS(testdata, "etc_hosts"))
+
 	testCases := []struct {
 		want []*rules.DNSRewrite
 		name string

internal/aghnet/net.go

@@ -2,19 +2,27 @@
 package aghnet
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"io"
 	"net"
-	"os/exec"
-	"strings"
 	"syscall"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/netutil"
 )
 
+// aghosRunCommand is the function to run shell commands.  It's an unexported
+// variable instead of a direct call to make it substitutable in tests.
+var aghosRunCommand = aghos.RunCommand
+
+// rootDirFS is the filesystem pointing to the root directory.  It's an
+// unexported variable instead to make it substitutable in tests.
+var rootDirFS = aghos.RootDirFS()
+
 // ErrNoStaticIPInfo is returned by IfaceHasStaticIP when no information about
 // the IP being static is available.
 const ErrNoStaticIPInfo errors.Error = "no information about static ip"
@@ -32,22 +40,29 @@ func IfaceSetStaticIP(ifaceName string) (err error) {
 }
 
 // GatewayIP returns IP address of interface's gateway.
-func GatewayIP(ifaceName string) net.IP {
+//
-	cmd := exec.Command("ip", "route", "show", "dev", ifaceName)
+// TODO(e.burkov):  Investigate if the gateway address may be fetched in another
-	log.Tracef("executing %s %v", cmd.Path, cmd.Args)
+// way since not every machine has the software installed.
-	d, err := cmd.Output()
+func GatewayIP(ifaceName string) (ip net.IP) {
-	if err != nil || cmd.ProcessState.ExitCode() != 0 {
+	code, out, err := aghosRunCommand("ip", "route", "show", "dev", ifaceName)
+	if err != nil {
+		log.Debug("%s", err)
+
+		return nil
+	} else if code != 0 {
+		log.Debug("fetching gateway ip: unexpected exit code: %d", code)
+
 		return nil
 	}
 
-	fields := strings.Fields(string(d))
+	fields := bytes.Fields(out)
 	// The meaningful "ip route" command output should contain the word
 	// "default" at first field and default gateway IP address at third field.
-	if len(fields) < 3 || fields[0] != "default" {
+	if len(fields) < 3 || string(fields[0]) != "default" {
 		return nil
 	}
 
-	return net.ParseIP(fields[2])
+	return net.ParseIP(string(fields[2]))
 }
 
 // CanBindPort checks if we can bind to the given port.
@@ -101,7 +116,7 @@ func (iface NetInterface) MarshalJSON() ([]byte, error) {
 
 // GetValidNetInterfacesForWeb returns interfaces that are eligible for DNS and WEB only
 // we do not return link-local addresses here
-func GetValidNetInterfacesForWeb() ([]*NetInterface, error) {
+func GetValidNetInterfacesForWeb() (netInterfaces []*NetInterface, err error) {
 	ifaces, err := net.Interfaces()
 	if err != nil {
 		return nil, fmt.Errorf("couldn't get interfaces: %w", err)
@@ -109,8 +124,6 @@ func GetValidNetInterfacesForWeb() ([]*NetInterface, error) {
 		return nil, errors.Error("couldn't find any legible interface")
 	}
 
-	var netInterfaces []*NetInterface
-
 	for _, iface := range ifaces {
 		var addrs []net.Addr
 		addrs, err = iface.Addrs()
@@ -130,12 +143,14 @@ func GetValidNetInterfacesForWeb() ([]*NetInterface, error) {
 			ipNet, ok := addr.(*net.IPNet)
 			if !ok {
 				// Should be net.IPNet, this is weird.
-				return nil, fmt.Errorf("got iface.Addrs() element %s that is not net.IPNet, it is %T", addr, addr)
+				return nil, fmt.Errorf("got %s that is not net.IPNet, it is %T", addr, addr)
 			}
+
 			// Ignore link-local.
 			if ipNet.IP.IsLinkLocalUnicast() {
 				continue
 			}
+
 			netIface.Addresses = append(netIface.Addresses, ipNet.IP)
 			netIface.Subnets = append(netIface.Subnets, ipNet)
 		}

internal/aghnet/net_darwin.go

@@ -4,10 +4,11 @@
 package aghnet
 
 import (
+	"bufio"
+	"bytes"
 	"fmt"
-	"os"
+	"io"
 	"regexp"
-	"strings"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 	"github.com/AdguardTeam/golibs/errors"
@@ -27,7 +28,7 @@ func canBindPrivilegedPorts() (can bool, err error) {
 	return aghos.HaveAdminRights()
 }
 
-func ifaceHasStaticIP(ifaceName string) (bool, error) {
+func ifaceHasStaticIP(ifaceName string) (ok bool, err error) {
 	portInfo, err := getCurrentHardwarePortInfo(ifaceName)
 	if err != nil {
 		return false, err
@@ -36,9 +37,10 @@ func ifaceHasStaticIP(ifaceName string) (bool, error) {
 	return portInfo.static, nil
 }
 
-// getCurrentHardwarePortInfo gets information for the specified network interface.
+// getCurrentHardwarePortInfo gets information for the specified network
+// interface.
 func getCurrentHardwarePortInfo(ifaceName string) (hardwarePortInfo, error) {
-	// First of all we should find hardware port name
+	// First of all we should find hardware port name.
 	m := getNetworkSetupHardwareReports()
 	hardwarePort, ok := m[ifaceName]
 	if !ok {
@@ -48,6 +50,10 @@ func getCurrentHardwarePortInfo(ifaceName string) (hardwarePortInfo, error) {
 	return getHardwarePortInfo(hardwarePort)
 }
 
+// hardwareReportsReg is the regular expression matching the lines of
+// networksetup command output lines containing the interface information.
+var hardwareReportsReg = regexp.MustCompile("Hardware Port: (.*?)\nDevice: (.*?)\n")
+
 // getNetworkSetupHardwareReports parses the output of the `networksetup
 // -listallhardwareports` command it returns a map where the key is the
 // interface name, and the value is the "hardware port" returns nil if it fails
@@ -56,54 +62,44 @@ func getCurrentHardwarePortInfo(ifaceName string) (hardwarePortInfo, error) {
 // TODO(e.burkov):  There should be more proper approach than parsing the
 // command output.  For example, see
 // https://developer.apple.com/documentation/systemconfiguration.
-func getNetworkSetupHardwareReports() map[string]string {
+func getNetworkSetupHardwareReports() (reports map[string]string) {
-	_, out, err := aghos.RunCommand("networksetup", "-listallhardwareports")
+	_, out, err := aghosRunCommand("networksetup", "-listallhardwareports")
 	if err != nil {
 		return nil
 	}
 
-	re, err := regexp.Compile("Hardware Port: (.*?)\nDevice: (.*?)\n")
+	reports = make(map[string]string)
-	if err != nil {
+
-		return nil
+	matches := hardwareReportsReg.FindAllSubmatch(out, -1)
+	for _, m := range matches {
+		reports[string(m[2])] = string(m[1])
 	}
 
-	m := make(map[string]string)
+	return reports
-
-	matches := re.FindAllStringSubmatch(out, -1)
-	for i := range matches {
-		port := matches[i][1]
-		device := matches[i][2]
-		m[device] = port
 }
 
-	return m
+// hardwarePortReg is the regular expression matching the lines of networksetup
-}
+// command output lines containing the port information.
+var hardwarePortReg = regexp.MustCompile("IP address: (.*?)\nSubnet mask: (.*?)\nRouter: (.*?)\n")
 
-func getHardwarePortInfo(hardwarePort string) (hardwarePortInfo, error) {
+func getHardwarePortInfo(hardwarePort string) (h hardwarePortInfo, err error) {
-	h := hardwarePortInfo{}
+	_, out, err := aghosRunCommand("networksetup", "-getinfo", hardwarePort)
-
-	_, out, err := aghos.RunCommand("networksetup", "-getinfo", hardwarePort)
 	if err != nil {
 		return h, err
 	}
 
-	re := regexp.MustCompile("IP address: (.*?)\nSubnet mask: (.*?)\nRouter: (.*?)\n")
+	match := hardwarePortReg.FindSubmatch(out)
-
+	if len(match) != 4 {
-	match := re.FindStringSubmatch(out)
-	if len(match) == 0 {
 		return h, errors.Error("could not find hardware port info")
 	}
 
-	h.name = hardwarePort
+	return hardwarePortInfo{
-	h.ip = match[1]
+		name:      hardwarePort,
-	h.subnet = match[2]
+		ip:        string(match[1]),
-	h.gatewayIP = match[3]
+		subnet:    string(match[2]),
-
+		gatewayIP: string(match[3]),
-	if strings.Index(out, "Manual Configuration") == 0 {
+		static:    bytes.Index(out, []byte("Manual Configuration")) == 0,
-		h.static = true
+	}, nil
-	}
-
-	return h, nil
 }
 
 func ifaceSetStaticIP(ifaceName string) (err error) {
@@ -113,7 +109,7 @@ func ifaceSetStaticIP(ifaceName string) (err error) {
 	}
 
 	if portInfo.static {
-		return errors.Error("IP address is already static")
+		return errors.Error("ip address is already static")
 	}
 
 	dnsAddrs, err := getEtcResolvConfServers()
@@ -121,50 +117,62 @@ func ifaceSetStaticIP(ifaceName string) (err error) {
 		return err
 	}
 
-	args := make([]string, 0)
+	args := append([]string{"-setdnsservers", portInfo.name}, dnsAddrs...)
-	args = append(args, "-setdnsservers", portInfo.name)
-	args = append(args, dnsAddrs...)
 
 	// Setting DNS servers is necessary when configuring a static IP
-	code, _, err := aghos.RunCommand("networksetup", args...)
+	code, _, err := aghosRunCommand("networksetup", args...)
 	if err != nil {
 		return err
-	}
+	} else if code != 0 {
-	if code != 0 {
 		return fmt.Errorf("failed to set DNS servers, code=%d", code)
 	}
 
 	// Actually configures hardware port to have static IP
-	code, _, err = aghos.RunCommand("networksetup", "-setmanual",
+	code, _, err = aghosRunCommand(
-		portInfo.name, portInfo.ip, portInfo.subnet, portInfo.gatewayIP)
+		"networksetup",
+		"-setmanual",
+		portInfo.name,
+		portInfo.ip,
+		portInfo.subnet,
+		portInfo.gatewayIP,
+	)
 	if err != nil {
 		return err
-	}
+	} else if code != 0 {
-	if code != 0 {
 		return fmt.Errorf("failed to set DNS servers, code=%d", code)
 	}
 
 	return nil
 }
 
+// etcResolvConfReg is the regular expression matching the lines of resolv.conf
+// file containing a name server information.
+var etcResolvConfReg = regexp.MustCompile("nameserver ([a-zA-Z0-9.:]+)")
+
 // getEtcResolvConfServers returns a list of nameservers configured in
 // /etc/resolv.conf.
-func getEtcResolvConfServers() ([]string, error) {
+func getEtcResolvConfServers() (addrs []string, err error) {
-	body, err := os.ReadFile("/etc/resolv.conf")
+	const filename = "etc/resolv.conf"
-	if err != nil {
-		return nil, err
-	}
 
-	re := regexp.MustCompile("nameserver ([a-zA-Z0-9.:]+)")
+	_, err = aghos.FileWalker(func(r io.Reader) (_ []string, _ bool, err error) {
-
+		sc := bufio.NewScanner(r)
-	matches := re.FindAllStringSubmatch(string(body), -1)
+		for sc.Scan() {
+			matches := etcResolvConfReg.FindAllStringSubmatch(sc.Text(), -1)
 			if len(matches) == 0 {
-		return nil, errors.Error("found no DNS servers in /etc/resolv.conf")
+				continue
 			}
 
-	addrs := make([]string, 0)
+			for _, m := range matches {
-	for i := range matches {
+				addrs = append(addrs, m[1])
-		addrs = append(addrs, matches[i][1])
+			}
+		}
+
+		return nil, false, sc.Err()
+	}).Walk(rootDirFS, filename)
+	if err != nil {
+		return nil, fmt.Errorf("parsing etc/resolv.conf file: %w", err)
+	} else if len(addrs) == 0 {
+		return nil, fmt.Errorf("found no dns servers in %s", filename)
 	}
 
 	return addrs, nil

internal/aghnet/net_darwin_test.go

@@ -0,0 +1,261 @@
+package aghnet
+
+import (
+	"io/fs"
+	"testing"
+	"testing/fstest"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/testutil"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIfaceHasStaticIP(t *testing.T) {
+	testCases := []struct {
+		name       string
+		shell      mapShell
+		ifaceName  string
+		wantHas    assert.BoolAssertionFunc
+		wantErrMsg string
+	}{{
+		name: "success",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err:  nil,
+				out:  "IP address: 1.2.3.4\nSubnet mask: 255.255.255.0\nRouter: 1.2.3.1\n",
+				code: 0,
+			},
+		},
+		ifaceName:  "en0",
+		wantHas:    assert.False,
+		wantErrMsg: ``,
+	}, {
+		name: "success_static",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err: nil,
+				out: "Manual Configuration\nIP address: 1.2.3.4\n" +
+					"Subnet mask: 255.255.255.0\nRouter: 1.2.3.1\n",
+				code: 0,
+			},
+		},
+		ifaceName:  "en0",
+		wantHas:    assert.True,
+		wantErrMsg: ``,
+	}, {
+		name: "reports_error",
+		shell: theOnlyCmd(
+			"networksetup -listallhardwareports",
+			0,
+			"",
+			errors.Error("can't list"),
+		),
+		ifaceName:  "en0",
+		wantHas:    assert.False,
+		wantErrMsg: `could not find hardware port for en0`,
+	}, {
+		name: "port_error",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err:  errors.Error("can't get"),
+				out:  ``,
+				code: 0,
+			},
+		},
+		ifaceName:  "en0",
+		wantHas:    assert.False,
+		wantErrMsg: `can't get`,
+	}, {
+		name: "port_bad_output",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err:  nil,
+				out:  "nothing meaningful",
+				code: 0,
+			},
+		},
+		ifaceName:  "en0",
+		wantHas:    assert.False,
+		wantErrMsg: `could not find hardware port info`,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			substShell(t, tc.shell.RunCmd)
+
+			has, err := IfaceHasStaticIP(tc.ifaceName)
+			testutil.AssertErrorMsg(t, tc.wantErrMsg, err)
+
+			tc.wantHas(t, has)
+		})
+	}
+}
+
+func TestIfaceSetStaticIP(t *testing.T) {
+	succFsys := fstest.MapFS{
+		"etc/resolv.conf": &fstest.MapFile{
+			Data: []byte(`nameserver 1.1.1.1`),
+		},
+	}
+	panicFsys := &aghtest.FS{
+		OnOpen: func(name string) (fs.File, error) { panic("not implemented") },
+	}
+
+	testCases := []struct {
+		name       string
+		shell      mapShell
+		fsys       fs.FS
+		wantErrMsg string
+	}{{
+		name: "success",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err:  nil,
+				out:  "IP address: 1.2.3.4\nSubnet mask: 255.255.255.0\nRouter: 1.2.3.1\n",
+				code: 0,
+			},
+			"networksetup -setdnsservers hwport 1.1.1.1": {
+				err:  nil,
+				out:  "",
+				code: 0,
+			},
+			"networksetup -setmanual hwport 1.2.3.4 255.255.255.0 1.2.3.1": {
+				err:  nil,
+				out:  "",
+				code: 0,
+			},
+		},
+		fsys:       succFsys,
+		wantErrMsg: ``,
+	}, {
+		name: "static_already",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err: nil,
+				out: "Manual Configuration\nIP address: 1.2.3.4\n" +
+					"Subnet mask: 255.255.255.0\nRouter: 1.2.3.1\n",
+				code: 0,
+			},
+		},
+		fsys:       panicFsys,
+		wantErrMsg: `ip address is already static`,
+	}, {
+		name: "reports_error",
+		shell: theOnlyCmd(
+			"networksetup -listallhardwareports",
+			0,
+			"",
+			errors.Error("can't list"),
+		),
+		fsys:       panicFsys,
+		wantErrMsg: `could not find hardware port for en0`,
+	}, {
+		name: "resolv_conf_error",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err:  nil,
+				out:  "IP address: 1.2.3.4\nSubnet mask: 255.255.255.0\nRouter: 1.2.3.1\n",
+				code: 0,
+			},
+		},
+		fsys: fstest.MapFS{
+			"etc/resolv.conf": &fstest.MapFile{
+				Data: []byte("this resolv.conf is invalid"),
+			},
+		},
+		wantErrMsg: `found no dns servers in etc/resolv.conf`,
+	}, {
+		name: "set_dns_error",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err:  nil,
+				out:  "IP address: 1.2.3.4\nSubnet mask: 255.255.255.0\nRouter: 1.2.3.1\n",
+				code: 0,
+			},
+			"networksetup -setdnsservers hwport 1.1.1.1": {
+				err:  errors.Error("can't set"),
+				out:  "",
+				code: 0,
+			},
+		},
+		fsys:       succFsys,
+		wantErrMsg: `can't set`,
+	}, {
+		name: "set_manual_error",
+		shell: mapShell{
+			"networksetup -listallhardwareports": {
+				err:  nil,
+				out:  "Hardware Port: hwport\nDevice: en0\n",
+				code: 0,
+			},
+			"networksetup -getinfo hwport": {
+				err:  nil,
+				out:  "IP address: 1.2.3.4\nSubnet mask: 255.255.255.0\nRouter: 1.2.3.1\n",
+				code: 0,
+			},
+			"networksetup -setdnsservers hwport 1.1.1.1": {
+				err:  nil,
+				out:  "",
+				code: 0,
+			},
+			"networksetup -setmanual hwport 1.2.3.4 255.255.255.0 1.2.3.1": {
+				err:  errors.Error("can't set"),
+				out:  "",
+				code: 0,
+			},
+		},
+		fsys:       succFsys,
+		wantErrMsg: `can't set`,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			substShell(t, tc.shell.RunCmd)
+			substRootDirFS(t, tc.fsys)
+
+			err := IfaceSetStaticIP("en0")
+			testutil.AssertErrorMsg(t, tc.wantErrMsg, err)
+		})
+	}
+}

internal/aghnet/net_freebsd.go

@@ -22,7 +22,7 @@ func ifaceHasStaticIP(ifaceName string) (ok bool, err error) {
 
 	walker := aghos.FileWalker(interfaceName(ifaceName).rcConfStaticConfig)
 
-	return walker.Walk(aghos.RootDirFS(), rcConfFilename)
+	return walker.Walk(rootDirFS, rcConfFilename)
 }
 
 // rcConfStaticConfig checks if the interface is configured by /etc/rc.conf to

internal/aghnet/net_freebsd_test.go

@@ -4,56 +4,74 @@
 package aghnet
 
 import (
-	"strings"
+	"io/fs"
 	"testing"
+	"testing/fstest"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
 func TestRcConfStaticConfig(t *testing.T) {
-	const iface interfaceName = `em0`
+	const (
-	const nl = "\n"
+		ifaceName = `em0`
+		rcConf    = "etc/rc.conf"
+	)
 
 	testCases := []struct {
 		name     string
-		rcconfData string
+		rootFsys fs.FS
-		wantCont   bool
+		wantHas  assert.BoolAssertionFunc
 	}{{
 		name: "simple",
-		rcconfData: `ifconfig_em0="inet 127.0.0.253 netmask 0xffffffff"` + nl,
+		rootFsys: fstest.MapFS{rcConf: &fstest.MapFile{
-		wantCont:   false,
+			Data: []byte(`ifconfig_` + ifaceName + `="inet 127.0.0.253 netmask 0xffffffff"` + nl),
+		}},
+		wantHas: assert.True,
 	}, {
 		name: "case_insensitiveness",
-		rcconfData: `ifconfig_em0="InEt 127.0.0.253 NeTmAsK 0xffffffff"` + nl,
+		rootFsys: fstest.MapFS{rcConf: &fstest.MapFile{
-		wantCont:   false,
+			Data: []byte(`ifconfig_` + ifaceName + `="InEt 127.0.0.253 NeTmAsK 0xffffffff"` + nl),
+		}},
+		wantHas: assert.True,
 	}, {
 		name: "comments_and_trash",
-		rcconfData: `# comment 1` + nl +
+		rootFsys: fstest.MapFS{rcConf: &fstest.MapFile{
+			Data: []byte(`# comment 1` + nl +
 				`` + nl +
 				`# comment 2` + nl +
-			`ifconfig_em0="inet 127.0.0.253 netmask 0xffffffff"` + nl,
+				`ifconfig_` + ifaceName + `="inet 127.0.0.253 netmask 0xffffffff"` + nl,
-		wantCont: false,
+			),
+		}},
+		wantHas: assert.True,
 	}, {
 		name: "aliases",
-		rcconfData: `ifconfig_em0_alias="inet 127.0.0.1/24"` + nl +
+		rootFsys: fstest.MapFS{rcConf: &fstest.MapFile{
-			`ifconfig_em0="inet 127.0.0.253 netmask 0xffffffff"` + nl,
+			Data: []byte(`ifconfig_` + ifaceName + `_alias="inet 127.0.0.1/24"` + nl +
-		wantCont: false,
+				`ifconfig_` + ifaceName + `="inet 127.0.0.253 netmask 0xffffffff"` + nl,
+			),
+		}},
+		wantHas: assert.True,
 	}, {
 		name: "incorrect_config",
-		rcconfData: `ifconfig_em0="inet6 127.0.0.253 netmask 0xffffffff"` + nl +
+		rootFsys: fstest.MapFS{rcConf: &fstest.MapFile{
-			`ifconfig_em0="inet 256.256.256.256 netmask 0xffffffff"` + nl +
+			Data: []byte(
-			`ifconfig_em0=""` + nl,
+				`ifconfig_` + ifaceName + `="inet6 127.0.0.253 netmask 0xffffffff"` + nl +
-		wantCont: true,
+					`ifconfig_` + ifaceName + `="inet 256.256.256.256 netmask 0xffffffff"` + nl +
+					`ifconfig_` + ifaceName + `=""` + nl,
+			),
+		}},
+		wantHas: assert.False,
 	}}
 
 	for _, tc := range testCases {
-		r := strings.NewReader(tc.rcconfData)
 		t.Run(tc.name, func(t *testing.T) {
-			_, cont, err := iface.rcConfStaticConfig(r)
+			substRootDirFS(t, tc.rootFsys)
+
+			has, err := IfaceHasStaticIP(ifaceName)
 			require.NoError(t, err)
 
-			assert.Equal(t, tc.wantCont, cont)
+			tc.wantHas(t, has)
 		})
 	}
 }

internal/aghnet/net_linux.go

@@ -21,8 +21,7 @@ import (
 // have a static IP.
 func (n interfaceName) dhcpcdStaticConfig(r io.Reader) (subsources []string, cont bool, err error) {
 	s := bufio.NewScanner(r)
-	ifaceFound := findIfaceLine(s, string(n))
+	if !findIfaceLine(s, string(n)) {
-	if !ifaceFound {
 		return nil, true, s.Err()
 	}
 
@@ -61,9 +60,9 @@ func (n interfaceName) ifacesStaticConfig(r io.Reader) (sub []string, cont bool,
 		fields := strings.Fields(line)
 		fieldsNum := len(fields)
 
-		// Man page interfaces(5) declares that interface definition
+		// Man page interfaces(5) declares that interface definition should
-		// should consist of the key word "iface" followed by interface
+		// consist of the key word "iface" followed by interface name, and
-		// name, and method at fourth field.
+		// method at fourth field.
 		if fieldsNum >= 4 &&
 			fields[0] == "iface" && fields[1] == string(n) && fields[3] == "static" {
 			return nil, false, nil
@@ -78,10 +77,10 @@ func (n interfaceName) ifacesStaticConfig(r io.Reader) (sub []string, cont bool,
 }
 
 func ifaceHasStaticIP(ifaceName string) (has bool, err error) {
-	// TODO(a.garipov): Currently, this function returns the first
+	// TODO(a.garipov): Currently, this function returns the first definitive
-	// definitive result.  So if /etc/dhcpcd.conf has a static IP while
+	// result.  So if /etc/dhcpcd.conf has and /etc/network/interfaces has no
-	// /etc/network/interfaces doesn't, it will return true.  Perhaps this
+	// static IP configuration, it will return true.  Perhaps this is not the
-	// is not the most desirable behavior.
+	// most desirable behavior.
 
 	iface := interfaceName(ifaceName)
 
@@ -95,12 +94,10 @@ func ifaceHasStaticIP(ifaceName string) (has bool, err error) {
 		FileWalker: iface.ifacesStaticConfig,
 		filename:   "etc/network/interfaces",
 	}} {
-		has, err = pair.Walk(aghos.RootDirFS(), pair.filename)
+		has, err = pair.Walk(rootDirFS, pair.filename)
 		if err != nil {
 			return false, err
-		}
+		} else if has {
-
-		if has {
 			return true, nil
 		}
 	}
@@ -141,13 +138,15 @@ func ifaceSetStaticIP(ifaceName string) (err error) {
 	gatewayIP := GatewayIP(ifaceName)
 	add := dhcpcdConfIface(ifaceName, ipNet, gatewayIP, ipNet.IP)
 
-	body, err := os.ReadFile("/etc/dhcpcd.conf")
+	const filename = "/etc/dhcpcd.conf"
+
+	body, err := os.ReadFile(filename)
 	if err != nil && !errors.Is(err, os.ErrNotExist) {
 		return err
 	}
 
 	body = append(body, []byte(add)...)
-	err = maybe.WriteFile("/etc/dhcpcd.conf", body, 0o644)
+	err = maybe.WriteFile(filename, body, 0o644)
 	if err != nil {
 		return fmt.Errorf("writing conf: %w", err)
 	}

internal/aghnet/net_linux_test.go

@@ -4,122 +4,130 @@
 package aghnet
 
 import (
-	"bytes"
+	"io/fs"
 	"net"
 	"testing"
+	"testing/fstest"
 
+	"github.com/AdguardTeam/golibs/testutil"
 	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 )
 
-func TestDHCPCDStaticConfig(t *testing.T) {
+func TestHasStaticIP(t *testing.T) {
-	const iface interfaceName = `wlan0`
+	const ifaceName = "wlan0"
+
+	const (
+		dhcpcd    = "etc/dhcpcd.conf"
+		netifaces = "etc/network/interfaces"
+	)
 
 	testCases := []struct {
+		rootFsys   fs.FS
 		name       string
-		data     []byte
+		wantHas    assert.BoolAssertionFunc
-		wantCont bool
+		wantErrMsg string
 	}{{
-		name: "has_not",
+		rootFsys: fstest.MapFS{
-		data: []byte(`#comment` + nl +
+			dhcpcd: &fstest.MapFile{
+				Data: []byte(`#comment` + nl +
 					`# comment` + nl +
 					`interface eth0` + nl +
 					`static ip_address=192.168.0.1/24` + nl +
-			`# interface ` + iface + nl +
+					`# interface ` + ifaceName + nl +
 					`static ip_address=192.168.1.1/24` + nl +
 					`# comment` + nl,
 				),
-		wantCont: true,
+			},
+		},
+		name:       "dhcpcd_has_not",
+		wantHas:    assert.False,
+		wantErrMsg: `no information about static ip`,
 	}, {
-		name: "has",
+		rootFsys: fstest.MapFS{
-		data: []byte(`#comment` + nl +
+			dhcpcd: &fstest.MapFile{
+				Data: []byte(`#comment` + nl +
 					`# comment` + nl +
-			`interface eth0` + nl +
+					`interface ` + ifaceName + nl +
 					`static ip_address=192.168.0.1/24` + nl +
-			`# interface ` + iface + nl +
+					`# interface ` + ifaceName + nl +
 					`static ip_address=192.168.1.1/24` + nl +
-			`# comment` + nl +
+					`# comment` + nl,
-			`interface ` + iface + nl +
-			`# comment` + nl +
-			`static ip_address=192.168.2.1/24` + nl,
 				),
-		wantCont: false,
+			},
-	}}
+		},
-
+		name:       "dhcpcd_has",
-	for _, tc := range testCases {
+		wantHas:    assert.True,
-		t.Run(tc.name, func(t *testing.T) {
+		wantErrMsg: ``,
-			r := bytes.NewReader(tc.data)
+	}, {
-			_, cont, err := iface.dhcpcdStaticConfig(r)
+		rootFsys: fstest.MapFS{
-			require.NoError(t, err)
+			netifaces: &fstest.MapFile{
-
+				Data: []byte(`allow-hotplug ` + ifaceName + nl +
-			assert.Equal(t, tc.wantCont, cont)
-		})
-	}
-}
-
-func TestIfacesStaticConfig(t *testing.T) {
-	const iface interfaceName = `enp0s3`
-
-	testCases := []struct {
-		name         string
-		data         []byte
-		wantCont     bool
-		wantPatterns []string
-	}{{
-		name: "has_not",
-		data: []byte(`allow-hotplug ` + iface + nl +
 					`#iface enp0s3 inet static` + nl +
 					`#  address 192.168.0.200` + nl +
 					`#  netmask 255.255.255.0` + nl +
 					`#  gateway 192.168.0.1` + nl +
-			`iface ` + iface + ` inet dhcp` + nl,
+					`iface ` + ifaceName + ` inet dhcp` + nl,
 				),
-		wantCont:     true,
+			},
-		wantPatterns: []string{},
+		},
+		name:       "netifaces_has_not",
+		wantHas:    assert.False,
+		wantErrMsg: `no information about static ip`,
 	}, {
-		name: "has",
+		rootFsys: fstest.MapFS{
-		data: []byte(`allow-hotplug ` + iface + nl +
+			netifaces: &fstest.MapFile{
-			`iface ` + iface + ` inet static` + nl +
+				Data: []byte(`allow-hotplug ` + ifaceName + nl +
+					`iface ` + ifaceName + ` inet static` + nl +
 					`  address 192.168.0.200` + nl +
 					`  netmask 255.255.255.0` + nl +
 					`  gateway 192.168.0.1` + nl +
-			`#iface ` + iface + ` inet dhcp` + nl,
+					`#iface ` + ifaceName + ` inet dhcp` + nl,
 				),
-		wantCont:     false,
+			},
-		wantPatterns: []string{},
+		},
+		name:       "netifaces_has",
+		wantHas:    assert.True,
+		wantErrMsg: ``,
 	}, {
-		name: "return_patterns",
+		rootFsys: fstest.MapFS{
-		data: []byte(`source hello` + nl +
+			netifaces: &fstest.MapFile{
-			`source world` + nl +
+				Data: []byte(`source hello` + nl +
-			`#iface ` + iface + ` inet static` + nl,
+					`#iface ` + ifaceName + ` inet static` + nl,
 				),
-		wantCont:     true,
+			},
-		wantPatterns: []string{"hello", "world"},
+			"hello": &fstest.MapFile{
+				Data: []byte(`iface ` + ifaceName + ` inet static` + nl),
+			},
+		},
+		name:       "netifaces_another_file",
+		wantHas:    assert.True,
+		wantErrMsg: ``,
 	}, {
-		// This one tests if the first found valid interface prevents
+		rootFsys: fstest.MapFS{
-		// checking files under the `source` directive.
+			netifaces: &fstest.MapFile{
-		name: "ignore_patterns",
+				Data: []byte(`source hello` + nl +
-		data: []byte(`source hello` + nl +
+					`iface ` + ifaceName + ` inet static` + nl,
-			`source world` + nl +
-			`iface ` + iface + ` inet static` + nl,
 				),
-		wantCont:     false,
+			},
-		wantPatterns: []string{},
+		},
+		name:       "netifaces_ignore_another",
+		wantHas:    assert.True,
+		wantErrMsg: ``,
 	}}
 
 	for _, tc := range testCases {
-		r := bytes.NewReader(tc.data)
 		t.Run(tc.name, func(t *testing.T) {
-			patterns, has, err := iface.ifacesStaticConfig(r)
+			substRootDirFS(t, tc.rootFsys)
-			require.NoError(t, err)
 
-			assert.Equal(t, tc.wantCont, has)
+			has, err := IfaceHasStaticIP(ifaceName)
-			assert.ElementsMatch(t, tc.wantPatterns, patterns)
+			testutil.AssertErrorMsg(t, tc.wantErrMsg, err)
+
+			tc.wantHas(t, has)
 		})
 	}
 }
 
-func TestSetStaticIPdhcpcdConf(t *testing.T) {
+func TestSetStaticIP_dhcpcdConfIface(t *testing.T) {
 	testCases := []struct {
 		name       string
 		dhcpcdConf string

internal/aghnet/net_openbsd.go

@@ -20,7 +20,7 @@ func canBindPrivilegedPorts() (can bool, err error) {
 func ifaceHasStaticIP(ifaceName string) (ok bool, err error) {
 	filename := fmt.Sprintf("etc/hostname.%s", ifaceName)
 
-	return aghos.FileWalker(hostnameIfStaticConfig).Walk(aghos.RootDirFS(), filename)
+	return aghos.FileWalker(hostnameIfStaticConfig).Walk(rootDirFS, filename)
 }
 
 // hostnameIfStaticConfig checks if the interface is configured by

internal/aghnet/net_openbsd_test.go

@@ -4,49 +4,69 @@
 package aghnet
 
 import (
-	"strings"
+	"fmt"
+	"io/fs"
 	"testing"
+	"testing/fstest"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-func TestHostnameIfStaticConfig(t *testing.T) {
+func TestIfaceHasStaticIP(t *testing.T) {
-	const nl = "\n"
+	const ifaceName = "em0"
+
+	confFile := fmt.Sprintf("etc/hostname.%s", ifaceName)
 
 	testCases := []struct {
 		name     string
-		rcconfData string
+		rootFsys fs.FS
-		wantHas    bool
+		wantHas  assert.BoolAssertionFunc
 	}{{
 		name: "simple",
-		rcconfData: `inet 127.0.0.253` + nl,
+		rootFsys: fstest.MapFS{
-		wantHas:    true,
+			confFile: &fstest.MapFile{
+				Data: []byte(`inet 127.0.0.253` + nl),
+			},
+		},
+		wantHas: assert.True,
 	}, {
 		name: "case_sensitiveness",
-		rcconfData: `InEt 127.0.0.253` + nl,
+		rootFsys: fstest.MapFS{
-		wantHas:    false,
+			confFile: &fstest.MapFile{
+				Data: []byte(`InEt 127.0.0.253` + nl),
+			},
+		},
+		wantHas: assert.False,
 	}, {
 		name: "comments_and_trash",
-		rcconfData: `# comment 1` + nl +
+		rootFsys: fstest.MapFS{
-			`` + nl +
+			confFile: &fstest.MapFile{
+				Data: []byte(`# comment 1` + nl + nl +
 					`# inet 127.0.0.253` + nl +
 					`inet` + nl,
-		wantHas: false,
+				),
+			},
+		},
+		wantHas: assert.False,
 	}, {
 		name: "incorrect_config",
-		rcconfData: `inet6 127.0.0.253` + nl +
+		rootFsys: fstest.MapFS{
-			`inet 256.256.256.256` + nl,
+			confFile: &fstest.MapFile{
-		wantHas: false,
+				Data: []byte(`inet6 127.0.0.253` + nl + `inet 256.256.256.256` + nl),
+			},
+		},
+		wantHas: assert.False,
 	}}
 
 	for _, tc := range testCases {
-		r := strings.NewReader(tc.rcconfData)
 		t.Run(tc.name, func(t *testing.T) {
-			_, has, err := hostnameIfStaticConfig(r)
+			substRootDirFS(t, tc.rootFsys)
+
+			has, err := IfaceHasStaticIP(ifaceName)
 			require.NoError(t, err)
 
-			assert.Equal(t, tc.wantHas, has)
+			tc.wantHas(t, has)
 		})
 	}
 }

internal/aghnet/net_test.go

@@ -1,9 +1,11 @@
 package aghnet
 
 import (
+	"fmt"
 	"io/fs"
 	"net"
 	"os"
+	"strings"
 	"testing"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
@@ -14,11 +16,102 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestMain(m *testing.M) {
+	aghtest.DiscardLogOutput(m)
+}
+
 // testdata is the filesystem containing data for testing the package.
 var testdata fs.FS = os.DirFS("./testdata")
 
-func TestMain(m *testing.M) {
+// substRootDirFS replaces the aghos.RootDirFS function used throughout the
-	aghtest.DiscardLogOutput(m)
+// package with fsys for tests ran under t.
+func substRootDirFS(t testing.TB, fsys fs.FS) {
+	t.Helper()
+
+	prev := rootDirFS
+	t.Cleanup(func() { rootDirFS = prev })
+	rootDirFS = fsys
+}
+
+// RunCmdFunc is the signature of aghos.RunCommand function.
+type RunCmdFunc func(cmd string, args ...string) (code int, out []byte, err error)
+
+// substShell replaces the the aghos.RunCommand function used throughout the
+// package with rc for tests ran under t.
+func substShell(t testing.TB, rc RunCmdFunc) {
+	t.Helper()
+
+	prev := aghosRunCommand
+	t.Cleanup(func() { aghosRunCommand = prev })
+	aghosRunCommand = rc
+}
+
+// mapShell is a substitution of aghos.RunCommand that maps the command to it's
+// execution result.  It's only needed to simplify testing.
+//
+// TODO(e.burkov):  Perhaps put all the shell interactions behind an interface.
+type mapShell map[string]struct {
+	err  error
+	out  string
+	code int
+}
+
+// theOnlyCmd returns s that only handles a single command and arguments
+// combination from cmd.
+func theOnlyCmd(cmd string, code int, out string, err error) (s mapShell) {
+	return mapShell{cmd: {code: code, out: out, err: err}}
+}
+
+// RunCmd is a RunCmdFunc handled by s.
+func (s mapShell) RunCmd(cmd string, args ...string) (code int, out []byte, err error) {
+	key := strings.Join(append([]string{cmd}, args...), " ")
+	ret, ok := s[key]
+	if !ok {
+		return 0, nil, fmt.Errorf("unexpected shell command %q", key)
+	}
+
+	return ret.code, []byte(ret.out), ret.err
+}
+
+func TestGatewayIP(t *testing.T) {
+	testCases := []struct {
+		name  string
+		shell mapShell
+		want  net.IP
+	}{{
+		name:  "success_v4",
+		shell: theOnlyCmd("ip route show dev ifaceName", 0, `default via 1.2.3.4 onlink`, nil),
+		want:  net.IP{1, 2, 3, 4}.To16(),
+	}, {
+		name:  "success_v6",
+		shell: theOnlyCmd("ip route show dev ifaceName", 0, `default via ::ffff onlink`, nil),
+		want: net.IP{
+			0x0, 0x0, 0x0, 0x0,
+			0x0, 0x0, 0x0, 0x0,
+			0x0, 0x0, 0x0, 0x0,
+			0x0, 0x0, 0xFF, 0xFF,
+		},
+	}, {
+		name:  "bad_output",
+		shell: theOnlyCmd("ip route show dev ifaceName", 0, `non-default via 1.2.3.4 onlink`, nil),
+		want:  nil,
+	}, {
+		name:  "err_runcmd",
+		shell: theOnlyCmd("ip route show dev ifaceName", 0, "", errors.Error("can't run command")),
+		want:  nil,
+	}, {
+		name:  "bad_code",
+		shell: theOnlyCmd("ip route show dev ifaceName", 1, "", nil),
+		want:  nil,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			substShell(t, tc.shell.RunCmd)
+
+			assert.Equal(t, tc.want, GatewayIP("ifaceName"))
+		})
+	}
 }
 
 func TestGetInterfaceByIP(t *testing.T) {
@@ -133,6 +226,8 @@ func TestCheckPort(t *testing.T) {
 }
 
 func TestCollectAllIfacesAddrs(t *testing.T) {
+	t.Skip("TODO(e.burkov):  Substitute the net.Interfaces.")
+
 	addrs, err := CollectAllIfacesAddrs()
 	require.NoError(t, err)
 

internal/aghos/os.go

@@ -57,20 +57,22 @@ func HaveAdminRights() (bool, error) {
 const MaxCmdOutputSize = 64 * 1024
 
 // RunCommand runs shell command.
-func RunCommand(command string, arguments ...string) (code int, output string, err error) {
+func RunCommand(command string, arguments ...string) (code int, output []byte, err error) {
 	cmd := exec.Command(command, arguments...)
 	out, err := cmd.Output()
 	if len(out) > MaxCmdOutputSize {
 		out = out[:MaxCmdOutputSize]
 	}
 
-	if errors.As(err, new(*exec.ExitError)) {
+	if err != nil {
-		return cmd.ProcessState.ExitCode(), string(out), nil
+		if eerr := new(exec.ExitError); errors.As(err, &eerr) {
-	} else if err != nil {
+			return eerr.ExitCode(), eerr.Stderr, nil
-		return 1, "", fmt.Errorf("command %q failed: %w: %s", command, err, out)
 		}
 
-	return cmd.ProcessState.ExitCode(), string(out), nil
+		return 1, nil, fmt.Errorf("command %q failed: %w: %s", command, err, out)
+	}
+
+	return cmd.ProcessState.ExitCode(), out, nil
 }
 
 // PIDByCommand searches for process named command and returns its PID ignoring

internal/home/service_openbsd.go

@@ -314,12 +314,13 @@ func (s *openbsdRunComService) runCom(cmd string) (out string, err error) {
 	// TODO(e.burkov):  It's possible that os.ErrNotExist is caused by
 	// something different than the service script's non-existence.  Keep it
 	// in mind, when replace the aghos.RunCommand.
-	_, out, err = aghos.RunCommand(scriptPath, cmd)
+	var outData []byte
+	_, outData, err = aghos.RunCommand(scriptPath, cmd)
 	if errors.Is(err, os.ErrNotExist) {
 		return "", service.ErrNotInstalled
 	}
 
-	return out, err
+	return string(outData), err
 }
 
 // Status implements service.Service interface for *openbsdRunComService.