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// This file is part of gnunet-go, a GNUnet-implementation in Golang.
// Copyright (C) 2019, 2020 Bernd Fix >Y<
//
// gnunet-go is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// gnunet-go is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// SPDX-License-Identifier: AGPL3.0-or-later
package transport
import (
"encoding/hex"
"errors"
"fmt"
"path"
"strings"
"gnunet/message"
"gnunet/util"
"github.com/bfix/gospel/concurrent"
"github.com/bfix/gospel/data"
"github.com/bfix/gospel/logger"
)
// Error codes
var (
ErrChannelNotImplemented = fmt.Errorf("protocol not implemented")
ErrChannelNotOpened = fmt.Errorf("channel not opened")
ErrChannelInterrupted = fmt.Errorf("channel interrupted")
)
////////////////////////////////////////////////////////////////////////
// CHANNEL
// Channel is an abstraction for exchanging arbitrary data over various
// transport protocols and mechanisms. They are created by clients via
// 'NewChannel()' or by services run via 'NewChannelServer()'.
// A string specifies the end-point of the channel:
// "unix+/tmp/test.sock" -- for UDS channels
// "tcp+1.2.3.4:5" -- for TCP channels
// "udp+1.2.3.4:5" -- for UDP channels
type Channel interface {
Open(spec string) error // open channel (for read/write)
Close() error // close open channel
IsOpen() bool // check if channel is open
Read([]byte, *concurrent.Signaller) (int, error) // read from channel
Write([]byte, *concurrent.Signaller) (int, error) // write to channel
}
// ChannelFactory instantiates specific Channel imülementations.
type ChannelFactory func() Channel
// Known channel implementations.
var channelImpl = map[string]ChannelFactory{
"unix": NewSocketChannel,
"tcp": NewTCPChannel,
"udp": NewUDPChannel,
}
// NewChannel creates a new channel to the specified endpoint.
// Called by a client to connect to a service.
func NewChannel(spec string) (Channel, error) {
parts := strings.Split(spec, "+")
if fac, ok := channelImpl[parts[0]]; ok {
inst := fac()
err := inst.Open(spec)
return inst, err
}
return nil, ErrChannelNotImplemented
}
////////////////////////////////////////////////////////////////////////
// CHANNEL SERVER
// ChannelServer creates a listener for the specified endpoint.
// The specification string has the same format as for Channel with slightly
// different semantics (for TCP, and ICMP the address specifies is a mask
// for client addresses accepted for a channel request).
type ChannelServer interface {
Open(spec string, hdlr chan<- Channel) error
Close() error
}
// ChannelServerFactory instantiates specific ChannelServer imülementations.
type ChannelServerFactory func() ChannelServer
// Known channel server implementations.
var channelServerImpl = map[string]ChannelServerFactory{
"unix": NewSocketChannelServer,
"tcp": NewTCPChannelServer,
"udp": NewUDPChannelServer,
}
// NewChannelServer creates a new channel server instance
func NewChannelServer(spec string, hdlr chan<- Channel) (cs ChannelServer, err error) {
parts := strings.Split(spec, "+")
if fac, ok := channelServerImpl[parts[0]]; ok {
// check if the basedir for the spec exists...
if err = util.EnforceDirExists(path.Dir(parts[1])); err != nil {
return
}
// instantiate server implementation
cs = fac()
// create the domain socket and listen to it.
err = cs.Open(spec, hdlr)
return
}
return nil, ErrChannelNotImplemented
}
////////////////////////////////////////////////////////////////////////
// MESSAGE CHANNEL
// MsgChannel s a wrapper around a generic channel for GNUnet message exchange.
type MsgChannel struct {
ch Channel
buf []byte
}
// NewMsgChannel wraps a plain Channel for GNUnet message exchange.
func NewMsgChannel(ch Channel) *MsgChannel {
return &MsgChannel{
ch: ch,
buf: make([]byte, 65536),
}
}
// Close a MsgChannel by closing the wrapped plain Channel.
func (c *MsgChannel) Close() error {
return c.ch.Close()
}
// Send a GNUnet message over a channel.
func (c *MsgChannel) Send(msg message.Message, sig *concurrent.Signaller) error {
// convert message to binary data
data, err := data.Marshal(msg)
if err != nil {
return err
}
logger.Printf(logger.DBG, "==> %v\n", msg)
logger.Printf(logger.DBG, " [%s]\n", hex.EncodeToString(data))
// check message header size and packet size
mh, err := message.GetMsgHeader(data)
if err != nil {
return err
}
if len(data) != int(mh.MsgSize) {
return errors.New("send: message size mismatch")
}
// send packet
n, err := c.ch.Write(data, sig)
if err != nil {
return err
}
if n != len(data) {
return errors.New("incomplete send")
}
return nil
}
// Receive GNUnet messages over a plain Channel.
func (c *MsgChannel) Receive(sig *concurrent.Signaller) (message.Message, error) {
// get bytes from channel
get := func(pos, count int) error {
n, err := c.ch.Read(c.buf[pos:pos+count], sig)
if err != nil {
return err
}
if n != count {
return errors.New("not enough bytes on network")
}
return nil
}
if err := get(0, 4); err != nil {
return nil, err
}
mh, err := message.GetMsgHeader(c.buf[:4])
if err != nil {
return nil, err
}
if err := get(4, int(mh.MsgSize)-4); err != nil {
return nil, err
}
msg, err := message.NewEmptyMessage(mh.MsgType)
if err != nil {
return nil, err
}
if msg == nil {
return nil, fmt.Errorf("message{%d} is nil", mh.MsgType)
}
if err = data.Unmarshal(msg, c.buf[:mh.MsgSize]); err != nil {
return nil, err
}
logger.Printf(logger.DBG, "<== %v\n", msg)
logger.Printf(logger.DBG, " [%s]\n", hex.EncodeToString(c.buf[:mh.MsgSize]))
return msg, nil
}
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