// Copyright (C) 2016 Nippon Telegraph and Telephone Corporation.
//
// 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 server

import (
	"net"
	"os"
	"strings"
	"syscall"
	"unsafe"
)

const (
	TCP_MD5SIG = 14
)

type tcpmd5sig struct {
	ss_family uint16
	ss        [126]byte
	pad1      uint16
	keylen    uint16
	pad2      uint32
	key       [80]byte
}

func buildTcpMD5Sig(address string, key string) (tcpmd5sig, error) {
	t := tcpmd5sig{}
	addr := net.ParseIP(address)
	if addr.To4() != nil {
		t.ss_family = syscall.AF_INET
		copy(t.ss[2:], addr.To4())
	} else {
		t.ss_family = syscall.AF_INET6
		copy(t.ss[6:], addr.To16())
	}

	t.keylen = uint16(len(key))
	copy(t.key[0:], []byte(key))

	return t, nil
}

func SetTcpMD5SigSockopts(l *net.TCPListener, address string, key string) error {
	t, _ := buildTcpMD5Sig(address, key)
	fi, err := l.File()
	defer fi.Close()
	if err != nil {
		return err
	}
	if l, err := net.FileListener(fi); err == nil {
		defer l.Close()
	}
	_, _, e := syscall.Syscall6(syscall.SYS_SETSOCKOPT, fi.Fd(),
		uintptr(syscall.IPPROTO_TCP), uintptr(TCP_MD5SIG),
		uintptr(unsafe.Pointer(&t)), unsafe.Sizeof(t), 0)
	if e > 0 {
		return e
	}
	return nil
}

func SetTcpTTLSockopts(conn *net.TCPConn, ttl int) error {
	level := syscall.IPPROTO_IP
	name := syscall.IP_TTL
	if strings.Contains(conn.RemoteAddr().String(), "[") {
		level = syscall.IPPROTO_IPV6
		name = syscall.IPV6_UNICAST_HOPS
	}
	fi, err := conn.File()
	defer fi.Close()
	if err != nil {
		return err
	}
	if conn, err := net.FileConn(fi); err == nil {
		defer conn.Close()
	}
	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(int(fi.Fd()), level, name, ttl))
}