Commit ce89d01a authored by Kirill Smelkov's avatar Kirill Smelkov

go/neo/neonet: Teach Dial to autodetect server encoding

NEO/go server accepts preferred encoding of client from start, but
NEO/py server implements either N or M encoding and disconnects client
silently if handshake is not exactly what is expected.

However we can teach Dial to retry with different preferred options and
this way when connection to a NEO/py server, it will essentially
autodetect which encoding is used and accepted by remote peer.
parent 7f1d0c39
// Copyright (C) 2021 Nexedi SA and Contributors.
// Kirill Smelkov <kirr@nexedi.com>
//
// This program is free software: you can Use, Study, Modify and Redistribute
// it under the terms of the GNU General Public License version 3, or (at your
// option) any later version, as published by the Free Software Foundation.
//
// You can also Link and Combine this program with other software covered by
// the terms of any of the Free Software licenses or any of the Open Source
// Initiative approved licenses and Convey the resulting work. Corresponding
// source of such a combination shall include the source code for all other
// software used.
//
// This program is distributed WITHOUT ANY WARRANTY; without even the implied
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
//
// See COPYING file for full licensing terms.
// See https://www.nexedi.com/licensing for rationale and options.
// Package tneonet provides testing hooks for neonet package.
package tneonet
import (
"lab.nexedi.com/kirr/neo/go/neo/proto"
)
var DialEncTryOrder *[]proto.Encoding // = &neonet.dialEncTryOrder
......@@ -23,6 +23,7 @@ package neonet
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"net"
......@@ -33,6 +34,7 @@ import (
"lab.nexedi.com/kirr/go123/xnet"
"lab.nexedi.com/kirr/neo/go/internal/xcontext"
"lab.nexedi.com/kirr/neo/go/internal/xio"
"lab.nexedi.com/kirr/neo/go/neo/internal/tneonet"
"lab.nexedi.com/kirr/neo/go/neo/proto"
)
......@@ -43,7 +45,7 @@ import (
// do not have such uses.
func _HandshakeClient(ctx context.Context, conn net.Conn) (*NodeLink, error) {
return handshakeClient(ctx, conn, proto.Version, proto.Encoding('N'))
return handshakeClient(ctx, conn, proto.Version, dialEncTryOrder[0])
}
func _HandshakeServer(ctx context.Context, conn net.Conn) (*NodeLink, error) {
......@@ -273,15 +275,42 @@ func rxHello(errctx string, rx *xbufReader) (enc proto.Encoding, version uint32,
// ---- Dial & Listen at NodeLink level ----
// dialEncTryOrder is the order of trials for encoding when establishing a NEO link from client side.
//
// NEO/go server autodetects client preferred encoding and adjusts to that, but
// NEO/py rejects connections if client encoding does not exactly match server.
//
// To autodetect what NEO/py server uses DialLink retries dial + handshake with
// client-preferred encodings in the order specified by dialEncTryOrder.
//
// NOTE tests change this to verify that autodetection of NEO/py server
// encoding actually works.
var dialEncTryOrder = []proto.Encoding{'N', 'M'}
func init() {
tneonet.DialEncTryOrder = &dialEncTryOrder
}
// DialLink connects to address on given network, performs NEO protocol
// handshake and wraps the connection as NodeLink.
func DialLink(ctx context.Context, net xnet.Networker, addr string) (*NodeLink, error) {
func DialLink(ctx context.Context, net xnet.Networker, addr string) (link *NodeLink, err error) {
for _, enc := range dialEncTryOrder {
peerConn, err := net.Dial(ctx, addr)
if err != nil {
return nil, err
}
return _HandshakeClient(ctx, peerConn)
link, err = handshakeClient(ctx, peerConn, proto.Version, enc)
// NEO/py closes connection if it sees unexpected magic, version, etc.
// -> in such case retry with next encoding trying to autodetect and match server.
// -> stop trying on success, or on any other error.
if err == nil || !errors.Is(err, io.ErrUnexpectedEOF) {
break
}
}
// either link is established or the error indicates we should not retry anymore
return link, err
}
// ListenLink starts listening on laddr for incoming connections and wraps them as NodeLink.
......
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