/
direct_split.go
89 lines (78 loc) · 2.34 KB
/
direct_split.go
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// Copyright 2019 The Outline Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package dialers
import (
"io"
"net"
"github.com/celzero/firestack/intra/protect"
)
// DuplexConn represents a bidirectional stream socket.
type DuplexConn interface {
net.Conn
io.ReaderFrom
CloseWrite() error
CloseRead() error
}
type splitter struct {
*net.TCPConn
used bool // Initially false. Becomes true after the first write.
}
// split returns a DuplexConn that always splits the initial upstream segment.
func split(c *net.TCPConn) DuplexConn {
return &splitter{TCPConn: c}
}
// DialWithSplit returns a TCP connection that always splits the initial upstream segment.
// Like net.Conn, it is intended for two-threaded use, with one thread calling
// Read and CloseRead, and another calling Write, ReadFrom, and CloseWrite.
func DialWithSplit(d *protect.RDial, addr *net.TCPAddr) (DuplexConn, error) {
conn, err := d.DialTCP(addr.Network(), nil, addr)
if err != nil {
return nil, err
}
if conn == nil {
return nil, errNoConn
}
return split(conn), nil
}
// Write-related functions
func (s *splitter) Write(b []byte) (int, error) {
conn := s.TCPConn
if s.used {
// After the first write, there is no special write behavior.
return conn.Write(b)
}
// Setting `used` to true ensures that this code only runs once per socket.
s.used = true
b1, b2 := splitHello(b)
n1, err := conn.Write(b1)
if err != nil {
return n1, err
}
n2, err := conn.Write(b2)
return n1 + n2, err
}
func (s *splitter) ReadFrom(reader io.Reader) (bytes int64, err error) {
if !s.used {
// This is the first write on this socket.
// Use copyOnce(), which calls Write(), to get Write's splitting behavior for
// the first segment.
if bytes, err = copyOnce(s, reader); err != nil {
return
}
}
var b int64
b, err = s.TCPConn.ReadFrom(reader)
bytes += b
return
}