/
plain.go
226 lines (199 loc) · 5 KB
/
plain.go
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package dcs
import (
"context"
"io"
"net"
"strconv"
"github.com/go-faster/errors"
"go.uber.org/multierr"
"github.com/gotd/td/crypto"
"github.com/gotd/td/mtproxy"
"github.com/gotd/td/mtproxy/obfuscator"
"github.com/gotd/td/proto/codec"
"github.com/gotd/td/tg"
"github.com/gotd/td/transport"
)
var _ Resolver = plain{}
type plain struct {
dial DialFunc
protocol Protocol
rand io.Reader
network string
noObfuscated bool
preferIPv6 bool
}
func (p plain) Primary(ctx context.Context, dc int, list List) (transport.Conn, error) {
candidates := FindPrimaryDCs(list.Options, dc, p.preferIPv6)
if p.noObfuscated {
n := 0
for _, x := range candidates {
if !x.TCPObfuscatedOnly {
candidates[n] = x
n++
}
}
candidates = candidates[:n]
}
return p.connect(ctx, dc, list.Test, candidates)
}
func (p plain) MediaOnly(ctx context.Context, dc int, list List) (transport.Conn, error) {
candidates := FindDCs(list.Options, dc, p.preferIPv6)
// Filter (in place) from SliceTricks.
n := 0
for _, x := range candidates {
if x.MediaOnly {
candidates[n] = x
n++
}
}
return p.connect(ctx, dc, list.Test, candidates[:n])
}
func (p plain) CDN(ctx context.Context, dc int, list List) (transport.Conn, error) {
return nil, errors.Errorf("can't resolve %d: CDN is unsupported", dc)
}
func (p plain) dialTransport(ctx context.Context, test bool, dc tg.DCOption) (_ transport.Conn, rerr error) {
addr := net.JoinHostPort(dc.IPAddress, strconv.Itoa(dc.Port))
conn, err := p.dial(ctx, p.network, addr)
if err != nil {
return nil, err
}
defer func() {
if rerr != nil {
multierr.AppendInto(&rerr, conn.Close())
}
}()
proto := p.protocol
if dc.TCPObfuscatedOnly {
dcID := dc.ID
if test {
if dcID < 0 {
dcID -= 10000
} else {
dcID += 10000
}
}
var (
cdc codec.Codec = codec.Intermediate{}
tag = codec.IntermediateClientStart
obfs = obfuscator.Obfuscated2
)
secret, err := mtproxy.ParseSecret(dc.Secret)
if err != nil {
return nil, errors.Wrap(err, "check DC secret")
}
if secret.Type == mtproxy.TLS {
obfs = obfuscator.FakeTLS
} else if c, ok := secret.ExpectedCodec(); ok {
tag = [4]byte{secret.Tag, secret.Tag, secret.Tag, secret.Tag}
cdc = c
}
obfsConn := obfs(p.rand, conn)
if err := obfsConn.Handshake(tag, dcID, secret); err != nil {
return nil, err
}
conn = obfsConn
proto = transport.NewProtocol(func() transport.Codec {
return codec.NoHeader{Codec: cdc}
})
}
transportConn, err := proto.Handshake(conn)
if err != nil {
return nil, errors.Wrap(err, "transport handshake")
}
return transportConn, nil
}
func (p plain) connect(ctx context.Context, dc int, test bool, dcOptions []tg.DCOption) (transport.Conn, error) {
switch len(dcOptions) {
case 0:
return nil, errors.Errorf("no addresses for DC %d", dc)
case 1:
return p.dialTransport(ctx, test, dcOptions[0])
}
type dialResult struct {
conn transport.Conn
err error
}
// We use unbuffered channel to ensure that only one connection will be returned
// and all other will be closed.
results := make(chan dialResult)
tryDial := func(ctx context.Context, option tg.DCOption) {
conn, err := p.dialTransport(ctx, test, option)
select {
case results <- dialResult{
conn: conn,
err: err,
}:
case <-ctx.Done():
if conn != nil {
_ = conn.Close()
}
}
}
dialCtx, dialCancel := context.WithCancel(ctx)
defer dialCancel()
for _, dcOption := range dcOptions {
go tryDial(dialCtx, dcOption)
}
remain := len(dcOptions)
var rErr error
for {
select {
case <-ctx.Done():
return nil, ctx.Err()
case result := <-results:
remain--
if result.err != nil {
rErr = multierr.Append(rErr, result.err)
if remain == 0 {
return nil, rErr
}
continue
}
return result.conn, nil
}
}
}
// PlainOptions is plain resolver creation options.
type PlainOptions struct {
// Protocol is the transport protocol to use. Defaults to intermediate.
Protocol Protocol
// Dial specifies the dial function for creating unencrypted TCP connections.
// If Dial is nil, then the resolver dials using package net.
Dial DialFunc
// Random source for TCPObfuscated DCs.
Rand io.Reader
// Network to use. Defaults to "tcp".
Network string
// NoObfuscated denotes to filter out TCP Obfuscated Only DCs.
NoObfuscated bool
// PreferIPv6 gives IPv6 DCs higher precedence.
// Default is to prefer IPv4 DCs over IPv6.
PreferIPv6 bool
}
func (m *PlainOptions) setDefaults() {
if m.Protocol == nil {
m.Protocol = transport.Intermediate
}
if m.Dial == nil {
var d net.Dialer
m.Dial = d.DialContext
}
if m.Rand == nil {
m.Rand = crypto.DefaultRand()
}
if m.Network == "" {
m.Network = "tcp"
}
}
// Plain creates plain DC resolver.
func Plain(opts PlainOptions) Resolver {
opts.setDefaults()
return plain{
dial: opts.Dial,
protocol: opts.Protocol,
rand: opts.Rand,
network: opts.Network,
noObfuscated: opts.NoObfuscated,
preferIPv6: opts.PreferIPv6,
}
}