1// +build !appengine
2
3/*
4 *
5 * Copyright 2018 gRPC authors.
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 *     http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 */
20
21// Package internal contains credentials-internal code.
22package internal
23
24import (
25	"net"
26	"syscall"
27)
28
29type sysConn = syscall.Conn
30
31// syscallConn keeps reference of rawConn to support syscall.Conn for channelz.
32// SyscallConn() (the method in interface syscall.Conn) is explicitly
33// implemented on this type,
34//
35// Interface syscall.Conn is implemented by most net.Conn implementations (e.g.
36// TCPConn, UnixConn), but is not part of net.Conn interface. So wrapper conns
37// that embed net.Conn don't implement syscall.Conn. (Side note: tls.Conn
38// doesn't embed net.Conn, so even if syscall.Conn is part of net.Conn, it won't
39// help here).
40type syscallConn struct {
41	net.Conn
42	// sysConn is a type alias of syscall.Conn. It's necessary because the name
43	// `Conn` collides with `net.Conn`.
44	sysConn
45}
46
47// WrapSyscallConn tries to wrap rawConn and newConn into a net.Conn that
48// implements syscall.Conn. rawConn will be used to support syscall, and newConn
49// will be used for read/write.
50//
51// This function returns newConn if rawConn doesn't implement syscall.Conn.
52func WrapSyscallConn(rawConn, newConn net.Conn) net.Conn {
53	sysConn, ok := rawConn.(syscall.Conn)
54	if !ok {
55		return newConn
56	}
57	return &syscallConn{
58		Conn:    newConn,
59		sysConn: sysConn,
60	}
61}
62