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d507126101
This is in preparation for future changes, but also improves the
handling when talking to pre-v0.13 clients. It breaks out the Hello
message and magic from the rest of the protocol implementation, with the
intention that this small part of the protocol will survive future
changes.
To enable this, and future testing, the new ExchangeHello function takes
an interface that can be implemented by future Hello versions and
returns a version indendent result type. It correctly detects pre-v0.13
protocols and returns a "too old" error message which gets logged to the
user at warning level:
[I6KAH] 09:21:36 WARNING: Connecting to [...]:
the remote device speaks an older version of the protocol (v0.12) not
compatible with this version
Conversely, something entirely unknown will generate:
[I6KAH] 09:40:27 WARNING: Connecting to [...]:
the remote device speaks an unknown (newer?) version of the protocol
The intention is that in future iterations the Hello exchange will
succeed on at least one side and ExchangeHello will return the actual
data from the Hello together with ErrTooOld and an even more precise
message can be generated.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3289
106 lines
2.8 KiB
Go
106 lines
2.8 KiB
Go
// Copyright (C) 2016 The Protocol Authors.
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package protocol
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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)
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// The HelloMessage interface is implemented by the version specific hello
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// message. It knows its magic number and how to serialize itself to a byte
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// buffer.
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type HelloMessage interface {
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Magic() uint32
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Marshal() ([]byte, error)
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}
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// The HelloResult is the non version specific interpretation of the other
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// side's Hello message.
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type HelloResult struct {
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DeviceName string
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ClientName string
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ClientVersion string
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}
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var (
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// ErrTooOldVersion12 is returned by ExchangeHello when the other side
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// speaks the older, incompatible version 0.12 of the protocol.
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ErrTooOldVersion12 = errors.New("the remote device speaks an older version of the protocol (v0.12) not compatible with this version")
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// ErrUnknownMagic is returned by ExchangeHellow when the other side
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// speaks something entirely unknown.
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ErrUnknownMagic = errors.New("the remote device speaks an unknown (newer?) version of the protocol")
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)
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func ExchangeHello(c io.ReadWriter, h HelloMessage) (HelloResult, error) {
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if err := writeHello(c, h); err != nil {
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return HelloResult{}, err
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}
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return readHello(c)
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}
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// IsVersionMismatch returns true if the error is a reliable indication of a
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// version mismatch that we might want to alert the user about.
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func IsVersionMismatch(err error) bool {
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switch err {
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case ErrTooOldVersion12, ErrUnknownMagic:
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return true
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default:
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return false
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}
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}
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func readHello(c io.Reader) (HelloResult, error) {
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header := make([]byte, 8)
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if _, err := io.ReadFull(c, header); err != nil {
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return HelloResult{}, err
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}
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switch binary.BigEndian.Uint32(header[:4]) {
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case Version13HelloMagic:
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// This is a v0.13 Hello message in XDR format
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msgSize := binary.BigEndian.Uint32(header[4:])
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if msgSize > 1024 {
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return HelloResult{}, fmt.Errorf("hello message too big")
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}
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buf := make([]byte, msgSize)
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if _, err := io.ReadFull(c, buf); err != nil {
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return HelloResult{}, err
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}
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var hello Version13HelloMessage
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if err := hello.UnmarshalXDR(buf); err != nil {
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return HelloResult{}, err
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}
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res := HelloResult{
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DeviceName: hello.DeviceName,
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ClientName: hello.ClientName,
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ClientVersion: hello.ClientVersion,
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}
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return res, nil
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case 0x00010001, 0x00010000:
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// This is the first word of a v0.12 cluster config message.
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// (Version 0, message ID 1, message type 0, compression enabled or disabled)
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return HelloResult{}, ErrTooOldVersion12
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}
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return HelloResult{}, ErrUnknownMagic
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}
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func writeHello(c io.Writer, h HelloMessage) error {
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msg, err := h.Marshal()
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if err != nil {
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return err
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}
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header := make([]byte, 8)
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binary.BigEndian.PutUint32(header[:4], h.Magic())
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binary.BigEndian.PutUint32(header[4:], uint32(len(msg)))
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_, err = c.Write(append(header, msg...))
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return err
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}
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