// Copyright 2015 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package net

import (
	"os"
	"syscall"
	"time"
)

func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
	if err := fd.incref(); err != nil {
		return err
	}
	defer fd.decref()
	// The kernel expects milliseconds so round to next highest
	// millisecond.
	d += (time.Millisecond - time.Nanosecond)
	msecs := int(d / time.Millisecond)

	// Normally we'd do
	//	syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPINTVL, secs)
	// here, but we can't because Solaris does not have TCP_KEEPINTVL.
	// Solaris has TCP_KEEPALIVE_ABORT_THRESHOLD, but it's not the same
	// thing, it refers to the total time until aborting (not between
	// probes), and it uses an exponential backoff algorithm instead of
	// waiting the same time between probes. We can't hope for the best
	// and do it anyway, like on Darwin, because Solaris might eventually
	// allocate a constant with a different meaning for the value of
	// TCP_KEEPINTVL on illumos.

	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPALIVE_THRESHOLD, msecs))
}