Pull request: 2846 cover aghnet vol.4

Merge in DNS/adguard-home from 2846-cover-aghnet-vol.4 to master

Updates #2846.

Squashed commit of the following:

commit 576ef857628a403ce1478c10a4aad23985c09613
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Mar 31 19:38:57 2022 +0300

    aghnet: imp code

commit 5b4b17ff52867aaab2c9d30a0fc7fc2fe31ff4d5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Mar 31 14:58:34 2022 +0300

    aghnet: imp coverage

internal/aghnet/arpdb_test.go

@@ -181,6 +181,16 @@ func TestCmdARPDB_arpa(t *testing.T) {
 		err := a.Refresh()
 		testutil.AssertErrorMsg(t, "cmd arpdb: running command: unexpected exit code 1", err)
 	})
+
+	t.Run("empty", func(t *testing.T) {
+		sh := theOnlyCmd("cmd", 0, "", nil)
+		substShell(t, sh.RunCmd)
+
+		err := a.Refresh()
+		require.NoError(t, err)
+
+		assert.Empty(t, a.Neighbors())
+	})
 }
 
 func TestEmptyARPDB(t *testing.T) {

internal/aghnet/hostgen.go

@@ -11,7 +11,7 @@ const (
 	ipv6HostnameMaxLen = len("ff80-f076-0000-0000-0000-0000-0000-0010")
 )
 
-// generateIPv4Hostname generates the hostname for specific IP version.
+// generateIPv4Hostname generates the hostname by IP address version 4.
 func generateIPv4Hostname(ipv4 net.IP) (hostname string) {
 	hnData := make([]byte, 0, ipv4HostnameMaxLen)
 	for i, part := range ipv4 {
@@ -24,7 +24,7 @@ func generateIPv4Hostname(ipv4 net.IP) (hostname string) {
 	return string(hnData)
 }
 
-// generateIPv6Hostname generates the hostname for specific IP version.
+// generateIPv6Hostname generates the hostname by IP address version 6.
 func generateIPv6Hostname(ipv6 net.IP) (hostname string) {
 	hnData := make([]byte, 0, ipv6HostnameMaxLen)
 	for i, partsNum := 0, net.IPv6len/2; i < partsNum; i++ {
@@ -51,12 +51,11 @@ func generateIPv6Hostname(ipv6 net.IP) (hostname string) {
 //
 //   ff80-f076-0000-0000-0000-0000-0000-0010
 //
+// ip must be either an IPv4 or an IPv6.
 func GenerateHostname(ip net.IP) (hostname string) {
 	if ipv4 := ip.To4(); ipv4 != nil {
 		return generateIPv4Hostname(ipv4)
-	} else if ipv6 := ip.To16(); ipv6 != nil {
-		return generateIPv6Hostname(ipv6)
 	}
 
-	return ""
+	return generateIPv6Hostname(ip)
 }

internal/aghnet/hostgen_test.go

@@ -8,6 +8,7 @@ import (
 )
 
 func TestGenerateHostName(t *testing.T) {
+	t.Run("valid", func(t *testing.T) {
 		testCases := []struct {
 			name string
 			want string
@@ -16,27 +17,14 @@ func TestGenerateHostName(t *testing.T) {
 			name: "good_ipv4",
 			want: "127-0-0-1",
 			ip:   net.IP{127, 0, 0, 1},
-	}, {
-		name: "bad_ipv4",
-		want: "",
-		ip:   net.IP{127, 0, 0, 1, 0},
 		}, {
 			name: "good_ipv6",
 			want: "fe00-0000-0000-0000-0000-0000-0000-0001",
 			ip:   net.ParseIP("fe00::1"),
 		}, {
-		name: "bad_ipv6",
-		want: "",
-		ip: net.IP{
-			0xff, 0xff, 0xff, 0xff,
-			0xff, 0xff, 0xff, 0xff,
-			0xff, 0xff, 0xff, 0xff,
-			0xff, 0xff, 0xff,
-		},
-	}, {
-		name: "nil",
-		want: "",
-		ip:   nil,
+			name: "4to6",
+			want: "1-2-3-4",
+			ip:   net.ParseIP("::ffff:1.2.3.4"),
 		}}
 
 		for _, tc := range testCases {
@@ -45,4 +33,32 @@ func TestGenerateHostName(t *testing.T) {
 				assert.Equal(t, tc.want, hostname)
 			})
 		}
+	})
+
+	t.Run("invalid", func(t *testing.T) {
+		testCases := []struct {
+			name string
+			ip   net.IP
+		}{{
+			name: "bad_ipv4",
+			ip:   net.IP{127, 0, 0, 1, 0},
+		}, {
+			name: "bad_ipv6",
+			ip: net.IP{
+				0xff, 0xff, 0xff, 0xff,
+				0xff, 0xff, 0xff, 0xff,
+				0xff, 0xff, 0xff, 0xff,
+				0xff, 0xff, 0xff,
+			},
+		}, {
+			name: "nil",
+			ip:   nil,
+		}}
+
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				assert.Panics(t, func() { GenerateHostname(tc.ip) })
+			})
+		}
+	})
 }

internal/aghnet/net.go

@@ -15,13 +15,17 @@ import (
 	"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
+// Variables and functions to substitute in tests.
+var (
+	// aghosRunCommand is the function to run shell commands.
+	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()
+	// netInterfaces is the function to get the available network interfaces.
+	netInterfaceAddrs = net.InterfaceAddrs
+
+	// rootDirFS is the filesystem pointing to the root directory.
+	rootDirFS = aghos.RootDirFS()
+)
 
 // ErrNoStaticIPInfo is returned by IfaceHasStaticIP when no information about
 // the IP being static is available.
@@ -65,23 +69,6 @@ func GatewayIP(ifaceName string) (ip net.IP) {
 	return net.ParseIP(string(fields[2]))
 }
 
-// CanBindPort checks if we can bind to the given port.
-func CanBindPort(port int) (can bool, err error) {
-	var addr *net.TCPAddr
-	addr, err = net.ResolveTCPAddr("tcp", fmt.Sprintf("127.0.0.1:%d", port))
-	if err != nil {
-		return false, err
-	}
-
-	var listener *net.TCPListener
-	listener, err = net.ListenTCP("tcp", addr)
-	if err != nil {
-		return false, err
-	}
-	_ = listener.Close()
-	return true, nil
-}
-
 // CanBindPrivilegedPorts checks if current process can bind to privileged
 // ports.
 func CanBindPrivilegedPorts() (can bool, err error) {
@@ -100,8 +87,8 @@ type NetInterface struct {
 	MTU          int              `json:"mtu"`
 }
 
-// MarshalJSON implements the json.Marshaler interface for NetInterface.
-func (iface NetInterface) MarshalJSON() ([]byte, error) {
+// MarshalText implements the json.Marshaler interface for NetInterface.
+func (iface NetInterface) MarshalText() ([]byte, error) {
 	type netInterface NetInterface
 	return json.Marshal(&struct {
 		HardwareAddr string `json:"hardware_address"`
@@ -114,9 +101,12 @@ 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() (netInterfaces []*NetInterface, err error) {
+// GetValidNetInterfacesForWeb returns interfaces that are eligible for DNS and
+// WEB only we do not return link-local addresses here.
+//
+// TODO(e.burkov):  Can't properly test the function since it's nontrivial to
+// substitute net.Interface.Addrs and the net.InterfaceAddrs can't be used.
+func GetValidNetInterfacesForWeb() (netIfaces []*NetInterface, err error) {
 	ifaces, err := net.Interfaces()
 	if err != nil {
 		return nil, fmt.Errorf("couldn't get interfaces: %w", err)
@@ -157,14 +147,16 @@ func GetValidNetInterfacesForWeb() (netInterfaces []*NetInterface, err error) {
 
 		// Discard interfaces with no addresses.
 		if len(netIface.Addresses) != 0 {
-			netInterfaces = append(netInterfaces, netIface)
+			netIfaces = append(netIfaces, netIface)
 		}
 	}
 
-	return netInterfaces, nil
+	return netIfaces, nil
 }
 
 // GetInterfaceByIP returns the name of interface containing provided ip.
+//
+// TODO(e.burkov):  See TODO on GetValidInterfacesForWeb.
 func GetInterfaceByIP(ip net.IP) string {
 	ifaces, err := GetValidNetInterfacesForWeb()
 	if err != nil {
@@ -184,6 +176,8 @@ func GetInterfaceByIP(ip net.IP) string {
 
 // GetSubnet returns pointer to net.IPNet for the specified interface or nil if
 // the search fails.
+//
+// TODO(e.burkov):  See TODO on GetValidInterfacesForWeb.
 func GetSubnet(ifaceName string) *net.IPNet {
 	netIfaces, err := GetValidNetInterfacesForWeb()
 	if err != nil {
@@ -234,17 +228,10 @@ func IsAddrInUse(err error) (ok bool) {
 // CollectAllIfacesAddrs returns the slice of all network interfaces IP
 // addresses without port number.
 func CollectAllIfacesAddrs() (addrs []string, err error) {
-	var ifaces []net.Interface
-	ifaces, err = net.Interfaces()
-	if err != nil {
-		return nil, fmt.Errorf("getting network interfaces: %w", err)
-	}
-
-	for _, iface := range ifaces {
 	var ifaceAddrs []net.Addr
-		ifaceAddrs, err = iface.Addrs()
+	ifaceAddrs, err = netInterfaceAddrs()
 	if err != nil {
-			return nil, fmt.Errorf("getting addresses for %q: %w", iface.Name, err)
+		return nil, fmt.Errorf("getting interfaces addresses: %w", err)
 	}
 
 	for _, addr := range ifaceAddrs {
@@ -257,7 +244,6 @@ func CollectAllIfacesAddrs() (addrs []string, err error) {
 
 		addrs = append(addrs, ip.String())
 	}
-	}
 
 	return addrs, nil
 }

internal/aghnet/net_darwin.go

@@ -24,10 +24,6 @@ type hardwarePortInfo struct {
 	static    bool
 }
 
-func canBindPrivilegedPorts() (can bool, err error) {
-	return aghos.HaveAdminRights()
-}
-
 func ifaceHasStaticIP(ifaceName string) (ok bool, err error) {
 	portInfo, err := getCurrentHardwarePortInfo(ifaceName)
 	if err != nil {

internal/aghnet/net_freebsd.go

@@ -13,10 +13,6 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 )
 
-func canBindPrivilegedPorts() (can bool, err error) {
-	return aghos.HaveAdminRights()
-}
-
 func ifaceHasStaticIP(ifaceName string) (ok bool, err error) {
 	const rcConfFilename = "etc/rc.conf"
 

internal/aghnet/net_freebsd_test.go

@@ -12,7 +12,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestRcConfStaticConfig(t *testing.T) {
+func TestIfaceHasStaticIP(t *testing.T) {
 	const (
 		ifaceName = `em0`
 		rcConf    = "etc/rc.conf"

internal/aghnet/net_linux.go

@@ -13,10 +13,28 @@ import (
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/stringutil"
 	"github.com/google/renameio/maybe"
 	"golang.org/x/sys/unix"
 )
 
+// dhcpсdConf is the name of /etc/dhcpcd.conf file in the root filesystem.
+const dhcpcdConf = "etc/dhcpcd.conf"
+
+func canBindPrivilegedPorts() (can bool, err error) {
+	cnbs, err := unix.PrctlRetInt(
+		unix.PR_CAP_AMBIENT,
+		unix.PR_CAP_AMBIENT_IS_SET,
+		unix.CAP_NET_BIND_SERVICE,
+		0,
+		0,
+	)
+	// Don't check the error because it's always nil on Linux.
+	adm, _ := aghos.HaveAdminRights()
+
+	return cnbs == 1 || adm, err
+}
+
 // dhcpcdStaticConfig checks if interface is configured by /etc/dhcpcd.conf to
 // have a static IP.
 func (n interfaceName) dhcpcdStaticConfig(r io.Reader) (subsources []string, cont bool, err error) {
@@ -89,7 +107,7 @@ func ifaceHasStaticIP(ifaceName string) (has bool, err error) {
 		filename string
 	}{{
 		FileWalker: iface.dhcpcdStaticConfig,
-		filename:   "etc/dhcpcd.conf",
+		filename:   dhcpcdConf,
 	}, {
 		FileWalker: iface.ifacesStaticConfig,
 		filename:   "etc/network/interfaces",
@@ -105,14 +123,6 @@ func ifaceHasStaticIP(ifaceName string) (has bool, err error) {
 	return false, ErrNoStaticIPInfo
 }
 
-func canBindPrivilegedPorts() (can bool, err error) {
-	cnbs, err := unix.PrctlRetInt(unix.PR_CAP_AMBIENT, unix.PR_CAP_AMBIENT_IS_SET, unix.CAP_NET_BIND_SERVICE, 0, 0)
-	// Don't check the error because it's always nil on Linux.
-	adm, _ := aghos.HaveAdminRights()
-
-	return cnbs == 1 || adm, err
-}
-
 // findIfaceLine scans s until it finds the line that declares an interface with
 // the given name.  If findIfaceLine can't find the line, it returns false.
 func findIfaceLine(s *bufio.Scanner, name string) (ok bool) {
@@ -128,25 +138,23 @@ func findIfaceLine(s *bufio.Scanner, name string) (ok bool) {
 }
 
 // ifaceSetStaticIP configures the system to retain its current IP on the
-// interface through dhcpdc.conf.
+// interface through dhcpcd.conf.
 func ifaceSetStaticIP(ifaceName string) (err error) {
 	ipNet := GetSubnet(ifaceName)
 	if ipNet.IP == nil {
 		return errors.Error("can't get IP address")
 	}
 
-	gatewayIP := GatewayIP(ifaceName)
-	add := dhcpcdConfIface(ifaceName, ipNet, gatewayIP, ipNet.IP)
-
-	const filename = "/etc/dhcpcd.conf"
-
-	body, err := os.ReadFile(filename)
+	body, err := os.ReadFile(dhcpcdConf)
 	if err != nil && !errors.Is(err, os.ErrNotExist) {
 		return err
 	}
 
+	gatewayIP := GatewayIP(ifaceName)
+	add := dhcpcdConfIface(ifaceName, ipNet, gatewayIP)
+
 	body = append(body, []byte(add)...)
-	err = maybe.WriteFile(filename, body, 0o644)
+	err = maybe.WriteFile(dhcpcdConf, body, 0o644)
 	if err != nil {
 		return fmt.Errorf("writing conf: %w", err)
 	}
@@ -156,22 +164,24 @@ func ifaceSetStaticIP(ifaceName string) (err error) {
 
 // dhcpcdConfIface returns configuration lines for the dhcpdc.conf files that
 // configure the interface to have a static IP.
-func dhcpcdConfIface(ifaceName string, ipNet *net.IPNet, gatewayIP, dnsIP net.IP) (conf string) {
-	var body []byte
-
-	add := fmt.Sprintf(
-		"\n# %[1]s added by AdGuard Home.\ninterface %[1]s\nstatic ip_address=%s\n",
+func dhcpcdConfIface(ifaceName string, ipNet *net.IPNet, gwIP net.IP) (conf string) {
+	b := &strings.Builder{}
+	stringutil.WriteToBuilder(
+		b,
+		"\n# ",
 		ifaceName,
-		ipNet)
-	body = append(body, []byte(add)...)
+		" added by AdGuard Home.\ninterface ",
+		ifaceName,
+		"\nstatic ip_address=",
+		ipNet.String(),
+		"\n",
+	)
 
-	if gatewayIP != nil {
-		add = fmt.Sprintf("static routers=%s\n", gatewayIP)
-		body = append(body, []byte(add)...)
+	if gwIP != nil {
+		stringutil.WriteToBuilder(b, "static routers=", gwIP.String(), "\n")
 	}
 
-	add = fmt.Sprintf("static domain_name_servers=%s\n\n", dnsIP)
-	body = append(body, []byte(add)...)
+	stringutil.WriteToBuilder(b, "static domain_name_servers=", ipNet.IP.String(), "\n\n")
 
-	return string(body)
+	return b.String()
 }

internal/aghnet/net_linux_test.go

@@ -5,7 +5,6 @@ package aghnet
 
 import (
 	"io/fs"
-	"net"
 	"testing"
 	"testing/fstest"
 
@@ -126,38 +125,3 @@ func TestHasStaticIP(t *testing.T) {
 		})
 	}
 }
-
-func TestSetStaticIP_dhcpcdConfIface(t *testing.T) {
-	testCases := []struct {
-		name       string
-		dhcpcdConf string
-		routers    net.IP
-	}{{
-		name: "with_gateway",
-		dhcpcdConf: nl + `# wlan0 added by AdGuard Home.` + nl +
-			`interface wlan0` + nl +
-			`static ip_address=192.168.0.2/24` + nl +
-			`static routers=192.168.0.1` + nl +
-			`static domain_name_servers=192.168.0.2` + nl + nl,
-		routers: net.IP{192, 168, 0, 1},
-	}, {
-		name: "without_gateway",
-		dhcpcdConf: nl + `# wlan0 added by AdGuard Home.` + nl +
-			`interface wlan0` + nl +
-			`static ip_address=192.168.0.2/24` + nl +
-			`static domain_name_servers=192.168.0.2` + nl + nl,
-		routers: nil,
-	}}
-
-	ipNet := &net.IPNet{
-		IP:   net.IP{192, 168, 0, 2},
-		Mask: net.IPMask{255, 255, 255, 0},
-	}
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			s := dhcpcdConfIface("wlan0", ipNet, tc.routers, net.IP{192, 168, 0, 2})
-			assert.Equal(t, tc.dhcpcdConf, s)
-		})
-	}
-}

internal/aghnet/net_nolinux.go

@@ -0,0 +1,10 @@
+//go:build !linux
+// +build !linux
+
+package aghnet
+
+import "github.com/AdguardTeam/AdGuardHome/internal/aghos"
+
+func canBindPrivilegedPorts() (can bool, err error) {
+	return aghos.HaveAdminRights()
+}

internal/aghnet/net_openbsd.go

@@ -13,10 +13,6 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 )
 
-func canBindPrivilegedPorts() (can bool, err error) {
-	return aghos.HaveAdminRights()
-}
-
 func ifaceHasStaticIP(ifaceName string) (ok bool, err error) {
 	filename := fmt.Sprintf("etc/hostname.%s", ifaceName)
 

internal/aghnet/net_test.go

@@ -56,7 +56,7 @@ type mapShell map[string]struct {
 	code int
 }
 
-// theOnlyCmd returns s that only handles a single command and arguments
+// theOnlyCmd returns mapShell 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}}
@@ -73,18 +73,34 @@ func (s mapShell) RunCmd(cmd string, args ...string) (code int, out []byte, err
 	return ret.code, []byte(ret.out), ret.err
 }
 
+// ifaceAddrsFunc is the signature of net.InterfaceAddrs function.
+type ifaceAddrsFunc func() (ifaces []net.Addr, err error)
+
+// substNetInterfaceAddrs replaces the the net.InterfaceAddrs function used
+// throughout the package with f for tests ran under t.
+func substNetInterfaceAddrs(t *testing.T, f ifaceAddrsFunc) {
+	t.Helper()
+
+	prev := netInterfaceAddrs
+	t.Cleanup(func() { netInterfaceAddrs = prev })
+	netInterfaceAddrs = f
+}
+
 func TestGatewayIP(t *testing.T) {
+	const ifaceName = "ifaceName"
+	const cmd = "ip route show dev " + ifaceName
+
 	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),
+		shell: theOnlyCmd(cmd, 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),
+		shell: theOnlyCmd(cmd, 0, `default via ::ffff onlink`, nil),
 		want: net.IP{
 			0x0, 0x0, 0x0, 0x0,
 			0x0, 0x0, 0x0, 0x0,
@@ -93,15 +109,15 @@ func TestGatewayIP(t *testing.T) {
 		},
 	}, {
 		name:  "bad_output",
-		shell: theOnlyCmd("ip route show dev ifaceName", 0, `non-default via 1.2.3.4 onlink`, nil),
+		shell: theOnlyCmd(cmd, 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")),
+		shell: theOnlyCmd(cmd, 0, "", errors.Error("can't run command")),
 		want:  nil,
 	}, {
 		name:  "bad_code",
-		shell: theOnlyCmd("ip route show dev ifaceName", 1, "", nil),
+		shell: theOnlyCmd(cmd, 1, "", nil),
 		want:  nil,
 	}}
 
@@ -109,7 +125,7 @@ func TestGatewayIP(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			substShell(t, tc.shell.RunCmd)
 
-			assert.Equal(t, tc.want, GatewayIP("ifaceName"))
+			assert.Equal(t, tc.want, GatewayIP(ifaceName))
 		})
 	}
 }
@@ -226,12 +242,56 @@ func TestCheckPort(t *testing.T) {
 }
 
 func TestCollectAllIfacesAddrs(t *testing.T) {
-	t.Skip("TODO(e.burkov):  Substitute the net.Interfaces.")
+	testCases := []struct {
+		name       string
+		wantErrMsg string
+		addrs      []net.Addr
+		wantAddrs  []string
+	}{{
+		name:       "success",
+		wantErrMsg: ``,
+		addrs: []net.Addr{&net.IPNet{
+			IP:   net.IP{1, 2, 3, 4},
+			Mask: net.CIDRMask(24, netutil.IPv4BitLen),
+		}, &net.IPNet{
+			IP:   net.IP{4, 3, 2, 1},
+			Mask: net.CIDRMask(16, netutil.IPv4BitLen),
+		}},
+		wantAddrs: []string{"1.2.3.4", "4.3.2.1"},
+	}, {
+		name:       "not_cidr",
+		wantErrMsg: `parsing cidr: invalid CIDR address: 1.2.3.4`,
+		addrs: []net.Addr{&net.IPAddr{
+			IP: net.IP{1, 2, 3, 4},
+		}},
+		wantAddrs: nil,
+	}, {
+		name:       "empty",
+		wantErrMsg: ``,
+		addrs:      []net.Addr{},
+		wantAddrs:  nil,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			substNetInterfaceAddrs(t, func() ([]net.Addr, error) { return tc.addrs, nil })
 
 			addrs, err := CollectAllIfacesAddrs()
-	require.NoError(t, err)
+			testutil.AssertErrorMsg(t, tc.wantErrMsg, err)
 
-	assert.NotEmpty(t, addrs)
+			assert.Equal(t, tc.wantAddrs, addrs)
+		})
+	}
+
+	t.Run("internal_error", func(t *testing.T) {
+		const errAddrs errors.Error = "can't get addresses"
+		const wantErrMsg string = `getting interfaces addresses: ` + string(errAddrs)
+
+		substNetInterfaceAddrs(t, func() ([]net.Addr, error) { return nil, errAddrs })
+
+		_, err := CollectAllIfacesAddrs()
+		testutil.AssertErrorMsg(t, wantErrMsg, err)
+	})
 }
 
 func TestIsAddrInUse(t *testing.T) {
@@ -250,3 +310,33 @@ func TestIsAddrInUse(t *testing.T) {
 		assert.False(t, IsAddrInUse(anotherErr))
 	})
 }
+
+func TestNetInterface_MarshalText(t *testing.T) {
+	const want = `{` +
+		`"hardware_address":"aa:bb:cc:dd:ee:ff",` +
+		`"flags":"up|multicast",` +
+		`"ip_addresses":["1.2.3.4","aaaa::1"],` +
+		`"name":"iface0",` +
+		`"mtu":1500` +
+		`}`
+
+	ip4, ip6 := net.IP{1, 2, 3, 4}, net.IP{0xAA, 0xAA, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
+	mask4, mask6 := net.CIDRMask(24, netutil.IPv4BitLen), net.CIDRMask(8, netutil.IPv6BitLen)
+
+	iface := &NetInterface{
+		Addresses: []net.IP{ip4, ip6},
+		Subnets: []*net.IPNet{{
+			IP:   ip4.Mask(mask4),
+			Mask: mask4,
+		}, {
+			IP:   ip6.Mask(mask6),
+			Mask: mask6,
+		}},
+		Name:         "iface0",
+		HardwareAddr: net.HardwareAddr{0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF},
+		Flags:        net.FlagUp | net.FlagMulticast,
+		MTU:          1500,
+	}
+
+	testutil.AssertMarshalText(t, want, iface)
+}

internal/aghnet/net_windows.go

@@ -13,10 +13,6 @@ import (
 	"golang.org/x/sys/windows"
 )
 
-func canBindPrivilegedPorts() (can bool, err error) {
-	return aghos.HaveAdminRights()
-}
-
 func ifaceHasStaticIP(string) (ok bool, err error) {
 	return false, aghos.Unsupported("checking static ip")
 }

internal/home/home.go

@@ -517,27 +517,15 @@ func StartMods() error {
 func checkPermissions() {
 	log.Info("Checking if AdGuard Home has necessary permissions")
 
-	if runtime.GOOS == "windows" {
-		// On Windows we need to have admin rights to run properly
-
-		admin, _ := aghos.HaveAdminRights()
-		if admin {
-			return
-		}
-
+	if ok, err := aghnet.CanBindPrivilegedPorts(); !ok || err != nil {
 		log.Fatal("This is the first launch of AdGuard Home. You must run it as Administrator.")
 	}
 
 	// We should check if AdGuard Home is able to bind to port 53
-	ok, err := aghnet.CanBindPort(53)
-
-	if ok {
-		log.Info("AdGuard Home can bind to port 53")
-		return
-	}
-
+	err := aghnet.CheckPort("tcp", net.IP{127, 0, 0, 1}, defaultPortDNS)
+	if err != nil {
 		if errors.Is(err, os.ErrPermission) {
-		msg := `Permission check failed.
+			log.Fatal(`Permission check failed.
 
 AdGuard Home is not allowed to bind to privileged ports (for instance, port 53).
 Please note, that this is crucial for a server to be able to use privileged ports.
@@ -545,16 +533,17 @@ Please note, that this is crucial for a server to be able to use privileged port
 You have two options:
 1. Run AdGuard Home with root privileges
 2. On Linux you can grant the CAP_NET_BIND_SERVICE capability:
-https://github.com/AdguardTeam/AdGuardHome/wiki/Getting-Started#running-without-superuser`
-
-		log.Fatal(msg)
+https://github.com/AdguardTeam/AdGuardHome/wiki/Getting-Started#running-without-superuser`)
 		}
 
-	msg := fmt.Sprintf(`AdGuard failed to bind to port 53 due to %v
+		log.Info(
+			"AdGuard failed to bind to port 53: %s\n\n"+
+				"Please note, that this is crucial for a DNS server to be able to use that port.",
+			err,
+		)
+	}
 
-Please note, that this is crucial for a DNS server to be able to use that port.`, err)
-
-	log.Info(msg)
+	log.Info("AdGuard Home can bind to port 53")
 }
 
 // Write PID to a file

scripts/make/go-lint.sh

@@ -134,9 +134,10 @@ underscores() {
 			-e '_bsd.go'\
 			-e '_darwin.go'\
 			-e '_freebsd.go'\
-			-e '_openbsd.go'\
 			-e '_linux.go'\
 			-e '_little.go'\
+			-e '_nolinux.go'\
+			-e '_openbsd.go'\
 			-e '_others.go'\
 			-e '_test.go'\
 			-e '_unix.go'\