1 //go:build unix
2 3 /*
4 * Copyright 2023 gRPC authors.
5 *
6 * Licensed under the Apache License, Version 2.0 (the "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 *
18 */
19 20 package internal
21 22 import (
23 "net"
24 "syscall"
25 "time"
26 27 "golang.org/x/sys/unix"
28 )
29 30 // NetDialerWithTCPKeepalive returns a net.Dialer that enables TCP keepalives on
31 // the underlying connection with OS default values for keepalive parameters.
32 //
33 // TODO: Once https://github.com/golang/go/issues/62254 lands, and the
34 // appropriate Go version becomes less than our least supported Go version, we
35 // should look into using the new API to make things more straightforward.
36 func NetDialerWithTCPKeepalive() *net.Dialer {
37 return &net.Dialer{
38 // Setting a negative value here prevents the Go stdlib from overriding
39 // the values of TCP keepalive time and interval. It also prevents the
40 // Go stdlib from enabling TCP keepalives by default.
41 KeepAlive: time.Duration(-1),
42 // This method is called after the underlying network socket is created,
43 // but before dialing the socket (or calling its connect() method). The
44 // combination of unconditionally enabling TCP keepalives here, and
45 // disabling the overriding of TCP keepalive parameters by setting the
46 // KeepAlive field to a negative value above, results in OS defaults for
47 // the TCP keepalive interval and time parameters.
48 Control: func(_, _ string, c syscall.RawConn) error {
49 return c.Control(func(fd uintptr) {
50 unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_KEEPALIVE, 1)
51 })
52 },
53 }
54 }
55