Use pipe instead of net.FileConn to read protobuf.

Signed-off-by: Njack.wxz <wangxiaozhe@linux.alibaba.com>

rune/libenclave/agent.go

@@ -208,15 +208,9 @@ func handleRequest(conn net.Conn, id int) {
 func relaySignal(signalPipe *os.File, id int) {
 	defer signalPipe.Close()
 
-	conn, err := net.FileConn(signalPipe)
-	if err != nil {
-		return
-	}
-	defer conn.Close()
-
 	for {
 		req := &pb.AgentServiceRequest{}
-		if err := protoBufRead(conn, req); err != nil {
+		if err := protoBufRead(signalPipe, req); err != nil {
 			return
 		}
 

rune/libenclave/utils.go

@@ -9,7 +9,6 @@ import (
 	pb "github.com/opencontainers/runc/libenclave/proto"
 	"golang.org/x/sys/unix"
 	"io"
-	"net"
 	"os"
 	"strconv"
 	"syscall"
@@ -79,7 +78,7 @@ func unstageFd(env string) {
 	}
 }
 
-func protoBufRead(conn net.Conn, unmarshaled interface{}) error {
+func protoBufRead(conn io.Reader, unmarshaled interface{}) error {
 	var sz uint32
 	data := make([]byte, unsafe.Sizeof(sz))
 	_, err := conn.Read(data)