// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package transport

import (
	"net"
	"time"
)

// NewKeepAliveListener returns a listener that listens on the given address.
// http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/overview.html
func NewKeepAliveListener(addr string, scheme string, info TLSInfo) (net.Listener, error) {
	ln, err := NewListener(addr, scheme, info)
	if err != nil {
		return nil, err
	}
	return &keepaliveListener{
		Listener: ln,
	}, nil
}

type keepaliveListener struct {
	net.Listener
}

func (kln *keepaliveListener) Accept() (net.Conn, error) {
	c, err := kln.Listener.Accept()
	if err != nil {
		return nil, err
	}
	tcpc := c.(*net.TCPConn)
	// detection time: tcp_keepalive_time + tcp_keepalive_probes + tcp_keepalive_intvl
	// default on linux:  30 + 8 * 30
	// default on osx:    30 + 8 * 75
	tcpc.SetKeepAlive(true)
	tcpc.SetKeepAlivePeriod(30 * time.Second)
	return tcpc, nil
}