Add implementation of telegram dialer

mtglib/internal/telegram/init.go

@@ -0,0 +1,53 @@
+package telegram
+
+import (
+	"context"
+	"net"
+)
+
+type preferIP uint8
+
+const (
+	preferIPOnlyIPv4 preferIP = iota
+	preferIPOnlyIPv6
+	preferIPPreferIPv4
+	preferIPPreferIPv6
+)
+
+type tgAddr struct {
+	network string
+	address string
+}
+
+// https://github.com/telegramdesktop/tdesktop/blob/master/Telegram/SourceFiles/mtproto/mtproto_dc_options.cpp#L30
+var (
+	v4Addresses = [5][]tgAddr{
+		{
+			{network: "tcp4", address: "149.154.175.50:443"},
+		},
+		{
+			{network: "tcp4", address: "149.154.167.51:443"},
+			{network: "tcp4", address: "95.161.76.100:443"},
+		},
+		{
+			{network: "tcp4", address: "149.154.175.100:443"},
+		},
+		{
+			{network: "tcp4", address: "149.154.167.91:443"},
+		},
+		{
+			{network: "tcp4", address: "149.154.171.5"},
+		},
+	}
+	v6Addresses = [5]tgAddr{
+		{network: "tcp6", address: "[2001:b28:f23d:f001::a]:443"},
+		{network: "tcp6", address: "[2001:67c:04e8:f002::a]:443"},
+		{network: "tcp6", address: "[2001:b28:f23d:f003::a]:443"},
+		{network: "tcp6", address: "[2001:67c:04e8:f004::a]:443"},
+		{network: "tcp6", address: "[2001:b28:f23f:f005::a]:443"},
+	}
+)
+
+type Dialer interface {
+	DialContext(ctx context.Context, network, address string) (net.Conn, error)
+}

mtglib/internal/telegram/telegram.go

@@ -0,0 +1,75 @@
+package telegram
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"net"
+	"strings"
+)
+
+type Telegram struct {
+	dialer   Dialer
+	preferIP preferIP
+}
+
+func (t Telegram) Dial(ctx context.Context, dc int) (net.Conn, error) {
+	if dc < 0 || dc > 4 {
+		return nil, fmt.Errorf("do not know how to dial to %d", dc)
+	}
+
+	var addresses []tgAddr
+
+	if t.preferIP == preferIPOnlyIPv6 {
+		addresses = []tgAddr{v6Addresses[dc]}
+	} else {
+		addresses = append(addresses, v4Addresses[dc]...)
+		rand.Shuffle(len(addresses), func(i, j int) {
+			addresses[i], addresses[j] = addresses[j], addresses[i]
+		})
+	}
+
+	switch t.preferIP {
+	case preferIPPreferIPv4:
+		addresses = append(addresses, v6Addresses[dc])
+	case preferIPPreferIPv6:
+		addresses = append([]tgAddr{v6Addresses[dc]}, addresses...)
+	case preferIPOnlyIPv4, preferIPOnlyIPv6:
+	}
+
+	var (
+		conn net.Conn
+		err  error
+	)
+
+	for _, v := range addresses {
+		conn, err = t.dialer.DialContext(ctx, v.network, v.address)
+		if err == nil {
+			return conn, nil
+		}
+	}
+
+	return nil, fmt.Errorf("cannot dial to %d dc: %w", dc, err)
+}
+
+func NewTelegramDialer(dialer Dialer, ipPreference string) (*Telegram, error) {
+	var pref preferIP
+
+	switch strings.ToLower(ipPreference) {
+	case "prefer-ipv4":
+		pref = preferIPPreferIPv4
+	case "prefer-ipv6":
+		pref = preferIPPreferIPv6
+	case "only-ipv4":
+		pref = preferIPOnlyIPv4
+	case "only-ipv6":
+		pref = preferIPOnlyIPv6
+	default:
+		return nil, fmt.Errorf("unknown ip preference %s", ipPreference)
+	}
+
+	return &Telegram{
+		dialer:   dialer,
+		preferIP: pref,
+	}, nil
+}