On client CloseWrite, do CloseWrite instead of Close for backend

Co-authored-by: Mathieu Lonjaret <mathieu.lonjaret@gmail.com>

pkg/tcp/proxy.go

@@ -3,28 +3,32 @@ package tcp
 import (
 	"io"
 	"net"
+	"time"
 
 	"github.com/containous/traefik/v2/pkg/log"
 )
 
 // Proxy forwards a TCP request to a TCP service
 type Proxy struct {
-	target *net.TCPAddr
+	target           *net.TCPAddr
+	terminationDelay time.Duration
 }
 
 // NewProxy creates a new Proxy
-func NewProxy(address string) (*Proxy, error) {
+func NewProxy(address string, terminationDelay time.Duration) (*Proxy, error) {
 	tcpAddr, err := net.ResolveTCPAddr("tcp", address)
 	if err != nil {
 		return nil, err
 	}
 
-	return &Proxy{target: tcpAddr}, nil
+	return &Proxy{target: tcpAddr, terminationDelay: terminationDelay}, nil
 }
 
 // ServeTCP forwards the connection to a service
-func (p *Proxy) ServeTCP(conn net.Conn) {
+func (p *Proxy) ServeTCP(conn WriteCloser) {
 	log.Debugf("Handling connection from %s", conn.RemoteAddr())
+
+	// needed because of e.g. server.trackedConnection
 	defer conn.Close()
 
 	connBackend, err := net.DialTCP("tcp", nil, p.target)
@@ -32,19 +36,35 @@ func (p *Proxy) ServeTCP(conn net.Conn) {
 		log.Errorf("Error while connection to backend: %v", err)
 		return
 	}
+
+	// maybe not needed, but just in case
 	defer connBackend.Close()
 
-	errChan := make(chan error, 1)
-	go connCopy(conn, connBackend, errChan)
-	go connCopy(connBackend, conn, errChan)
+	errChan := make(chan error)
+	go p.connCopy(conn, connBackend, errChan)
+	go p.connCopy(connBackend, conn, errChan)
 
 	err = <-errChan
 	if err != nil {
-		log.Errorf("Error during connection: %v", err)
+		log.WithoutContext().Errorf("Error during connection: %v", err)
 	}
+
+	<-errChan
 }
 
-func connCopy(dst, src net.Conn, errCh chan error) {
+func (p Proxy) connCopy(dst, src WriteCloser, errCh chan error) {
 	_, err := io.Copy(dst, src)
 	errCh <- err
+
+	errClose := dst.CloseWrite()
+	if errClose != nil {
+		log.WithoutContext().Errorf("Error while terminating connection: %v", errClose)
+	}
+
+	if p.terminationDelay >= 0 {
+		err := dst.SetReadDeadline(time.Now().Add(p.terminationDelay))
+		if err != nil {
+			log.WithoutContext().Errorf("Error while setting deadline: %v", err)
+		}
+	}
 }