Pull request: dhcpd: wait for interfaces' ip addresses to appear

Merge in DNS/adguard-home from 2304-dncp-backoff to master

Updates #2304.

Squashed commit of the following:

commit c9bff8b27c6b031d43a7dd98152adcde7f49fff1
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Nov 27 14:08:03 2020 +0300

    dhcpd: try for 5s instead of 10s

commit 983cf471832de0e7762b8b6e0a4ba9bb76ecadfc
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Nov 25 19:58:41 2020 +0300

    dhcpd: wait for interfaces' ip addresses to appear

internal/dhcpd/v46_test.go

@@ -0,0 +1,189 @@
+package dhcpd
+
+import (
+	"errors"
+	"net"
+	"testing"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/agherr"
+	"github.com/stretchr/testify/assert"
+)
+
+type fakeIface struct {
+	addrs []net.Addr
+	err   error
+}
+
+// Addrs implements the netIface interface for *fakeIface.
+func (iface *fakeIface) Addrs() (addrs []net.Addr, err error) {
+	if iface.err != nil {
+		return nil, iface.err
+	}
+
+	return iface.addrs, nil
+}
+
+func TestIfaceIPAddrs(t *testing.T) {
+	const errTest agherr.Error = "test error"
+
+	ip4 := net.IP{1, 2, 3, 4}
+	addr4 := &net.IPNet{IP: ip4}
+
+	ip6 := net.IP{1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6}
+	addr6 := &net.IPNet{IP: ip6}
+
+	testCases := []struct {
+		name    string
+		iface   netIface
+		ipv     ipVersion
+		want    []net.IP
+		wantErr error
+	}{{
+		name:    "ipv4_success",
+		iface:   &fakeIface{addrs: []net.Addr{addr4}, err: nil},
+		ipv:     ipVersion4,
+		want:    []net.IP{ip4},
+		wantErr: nil,
+	}, {
+		name:    "ipv4_success_with_ipv6",
+		iface:   &fakeIface{addrs: []net.Addr{addr6, addr4}, err: nil},
+		ipv:     ipVersion4,
+		want:    []net.IP{ip4},
+		wantErr: nil,
+	}, {
+		name:    "ipv4_error",
+		iface:   &fakeIface{addrs: []net.Addr{addr4}, err: errTest},
+		ipv:     ipVersion4,
+		want:    nil,
+		wantErr: errTest,
+	}, {
+		name:    "ipv6_success",
+		iface:   &fakeIface{addrs: []net.Addr{addr6}, err: nil},
+		ipv:     ipVersion6,
+		want:    []net.IP{ip6},
+		wantErr: nil,
+	}, {
+		name:    "ipv6_success_with_ipv4",
+		iface:   &fakeIface{addrs: []net.Addr{addr6, addr4}, err: nil},
+		ipv:     ipVersion6,
+		want:    []net.IP{ip6},
+		wantErr: nil,
+	}, {
+		name:    "ipv6_error",
+		iface:   &fakeIface{addrs: []net.Addr{addr6}, err: errTest},
+		ipv:     ipVersion6,
+		want:    nil,
+		wantErr: errTest,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, gotErr := ifaceIPAddrs(tc.iface, tc.ipv)
+			assert.Equal(t, tc.want, got)
+			assert.True(t, errors.Is(gotErr, tc.wantErr))
+		})
+	}
+}
+
+type waitingFakeIface struct {
+	addrs []net.Addr
+	err   error
+	n     int
+}
+
+// Addrs implements the netIface interface for *waitingFakeIface.
+func (iface *waitingFakeIface) Addrs() (addrs []net.Addr, err error) {
+	if iface.err != nil {
+		return nil, iface.err
+	}
+
+	if iface.n == 0 {
+		return iface.addrs, nil
+	}
+
+	iface.n--
+
+	return nil, nil
+}
+
+func TestIfaceDNSIPAddrs(t *testing.T) {
+	const errTest agherr.Error = "test error"
+
+	ip4 := net.IP{1, 2, 3, 4}
+	addr4 := &net.IPNet{IP: ip4}
+
+	ip6 := net.IP{1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6}
+	addr6 := &net.IPNet{IP: ip6}
+
+	testCases := []struct {
+		name    string
+		iface   netIface
+		ipv     ipVersion
+		want    []net.IP
+		wantErr error
+	}{{
+		name:    "ipv4_success",
+		iface:   &fakeIface{addrs: []net.Addr{addr4}, err: nil},
+		ipv:     ipVersion4,
+		want:    []net.IP{ip4, ip4},
+		wantErr: nil,
+	}, {
+		name:    "ipv4_success_with_ipv6",
+		iface:   &fakeIface{addrs: []net.Addr{addr6, addr4}, err: nil},
+		ipv:     ipVersion4,
+		want:    []net.IP{ip4, ip4},
+		wantErr: nil,
+	}, {
+		name:    "ipv4_error",
+		iface:   &fakeIface{addrs: []net.Addr{addr4}, err: errTest},
+		ipv:     ipVersion4,
+		want:    nil,
+		wantErr: errTest,
+	}, {
+		name: "ipv4_wait",
+		iface: &waitingFakeIface{
+			addrs: []net.Addr{addr4},
+			err:   nil,
+			n:     1,
+		},
+		ipv:     ipVersion4,
+		want:    []net.IP{ip4, ip4},
+		wantErr: nil,
+	}, {
+		name:    "ipv6_success",
+		iface:   &fakeIface{addrs: []net.Addr{addr6}, err: nil},
+		ipv:     ipVersion6,
+		want:    []net.IP{ip6, ip6},
+		wantErr: nil,
+	}, {
+		name:    "ipv6_success_with_ipv4",
+		iface:   &fakeIface{addrs: []net.Addr{addr6, addr4}, err: nil},
+		ipv:     ipVersion6,
+		want:    []net.IP{ip6, ip6},
+		wantErr: nil,
+	}, {
+		name:    "ipv6_error",
+		iface:   &fakeIface{addrs: []net.Addr{addr6}, err: errTest},
+		ipv:     ipVersion6,
+		want:    nil,
+		wantErr: errTest,
+	}, {
+		name: "ipv6_wait",
+		iface: &waitingFakeIface{
+			addrs: []net.Addr{addr6},
+			err:   nil,
+			n:     1,
+		},
+		ipv:     ipVersion6,
+		want:    []net.IP{ip6, ip6},
+		wantErr: nil,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, gotErr := ifaceDNSIPAddrs(tc.iface, tc.ipv, 2, 0)
+			assert.Equal(t, tc.want, got)
+			assert.True(t, errors.Is(gotErr, tc.wantErr))
+		})
+	}
+}