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package proxy
import (
"io"
"net"
"syscall"
)
// TCPProxy is a proxy for TCP connections. It implements the Proxy interface to
// handle TCP traffic forwarding between the frontend and backend addresses.
type TCPProxy struct {
Logger logger
listener *net.TCPListener
frontendAddr *net.TCPAddr
backendAddr *net.TCPAddr
}
// NewTCPProxy creates a new TCPProxy.
func NewTCPProxy(frontendAddr, backendAddr *net.TCPAddr, ops ...func(*TCPProxy)) (*TCPProxy, error) {
listener, err := net.ListenTCP("tcp", frontendAddr)
if err != nil {
return nil, err
}
// If the port in frontendAddr was 0 then ListenTCP will have a picked
// a port to listen on, hence the call to Addr to get that actual port:
proxy := &TCPProxy{
listener: listener,
frontendAddr: listener.Addr().(*net.TCPAddr),
backendAddr: backendAddr,
Logger: &noopLogger{},
}
for _, op := range ops {
op(proxy)
}
return proxy, nil
}
func (proxy *TCPProxy) clientLoop(client *net.TCPConn, quit chan bool) {
backend, err := net.DialTCP("tcp", nil, proxy.backendAddr)
if err != nil {
proxy.Logger.Printf("Can't forward traffic to backend tcp/%v: %s\n", proxy.backendAddr, err)
client.Close()
return
}
event := make(chan int64)
var broker = func(to, from *net.TCPConn) {
written, err := io.Copy(to, from)
if err != nil {
// If the socket we are writing to is shutdown with
// SHUT_WR, forward it to the other end of the pipe:
if err, ok := err.(*net.OpError); ok && err.Err == syscall.EPIPE {
from.CloseWrite()
}
}
to.CloseRead()
event <- written
}
go broker(client, backend)
go broker(backend, client)
var transferred int64
for i := 0; i < 2; i++ {
select {
case written := <-event:
transferred += written
case <-quit:
// Interrupt the two brokers and "join" them.
client.Close()
backend.Close()
for ; i < 2; i++ {
transferred += <-event
}
return
}
}
client.Close()
backend.Close()
}
// Run starts forwarding the traffic using TCP.
func (proxy *TCPProxy) Run() {
quit := make(chan bool)
defer close(quit)
for {
client, err := proxy.listener.Accept()
if err != nil {
proxy.Logger.Printf("Stopping proxy on tcp/%v for tcp/%v (%s)", proxy.frontendAddr, proxy.backendAddr, err)
return
}
go proxy.clientLoop(client.(*net.TCPConn), quit)
}
}
// Close stops forwarding the traffic.
func (proxy *TCPProxy) Close() { proxy.listener.Close() }
// FrontendAddr returns the TCP address on which the proxy is listening.
func (proxy *TCPProxy) FrontendAddr() net.Addr { return proxy.frontendAddr }
// BackendAddr returns the TCP proxied address.
func (proxy *TCPProxy) BackendAddr() net.Addr { return proxy.backendAddr }
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