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57 lines
1.6 KiB
Go
57 lines
1.6 KiB
Go
// Copyright (C) 2019 Storj Labs, Inc.
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// See LICENSE for copying information.
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// +build linux
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package netutil
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import (
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"errors"
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"net"
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"syscall"
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"time"
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"golang.org/x/sys/unix"
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)
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// SetUserTimeout sets the TCP_USER_TIMEOUT setting on the provided conn.
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func SetUserTimeout(conn *net.TCPConn, timeout time.Duration) error {
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// By default from Go, keep alive period + idle are ~15sec. The default
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// keep count is 8 according to some kernel docs. That means it should
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// fail after ~120 seconds. Unfortunately, keep alive only happens if
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// there is no send-q on the socket, and so a slow reader can still cause
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// hanging sockets forever. By setting user timeout, we will kill the
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// connection if any writes go unacknowledged for the amount of time.
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// This should close the keep alive hole.
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//
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// See https://blog.cloudflare.com/when-tcp-sockets-refuse-to-die/
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rawConn, err := conn.SyscallConn()
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if err != nil {
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return err
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}
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controlErr := rawConn.Control(func(fd uintptr) {
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err = unix.SetsockoptInt(int(fd), unix.SOL_TCP, unix.TCP_USER_TIMEOUT, int(timeout.Milliseconds()))
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})
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if controlErr != nil {
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return controlErr
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}
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if ignoreProtocolNotAvailable(err) != nil {
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return err
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}
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return nil
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}
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// ignoreProtocolNotAvailable ignores the "protocol not available" error that
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// is returned when netutil.SetUserTimeout is called if running on the Windows
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// Subsystem for Linux (see Jira issue COM-23).
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func ignoreProtocolNotAvailable(err error) error {
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var errno syscall.Errno
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if errors.As(err, &errno) {
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if errno == syscall.ENOPROTOOPT {
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return nil
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}
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}
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return err
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}
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