// Copyright 2012 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.

// +build darwin dragonfly freebsd netbsd openbsd

package ipv4

import (
	"net"
	"syscall"
	"unsafe"
)

func setControlMessage(fd int, opt *rawOpt, cf ControlFlags, on bool) error {
	opt.Lock()
	defer opt.Unlock()
	if cf&FlagTTL != 0 {
		if err := setInt(fd, &sockOpts[ssoReceiveTTL], boolint(on)); err != nil {
			return err
		}
		if on {
			opt.set(FlagTTL)
		} else {
			opt.clear(FlagTTL)
		}
	}
	if sockOpts[ssoPacketInfo].name > 0 {
		if cf&(FlagSrc|FlagDst|FlagInterface) != 0 {
			if err := setInt(fd, &sockOpts[ssoPacketInfo], boolint(on)); err != nil {
				return err
			}
			if on {
				opt.set(cf & (FlagSrc | FlagDst | FlagInterface))
			} else {
				opt.clear(cf & (FlagSrc | FlagDst | FlagInterface))

			}
		}
	} else {
		if cf&FlagDst != 0 {
			if err := setInt(fd, &sockOpts[ssoReceiveDst], boolint(on)); err != nil {
				return err
			}
			if on {
				opt.set(FlagDst)
			} else {
				opt.clear(FlagDst)
			}
		}
		if cf&FlagInterface != 0 {
			if err := setInt(fd, &sockOpts[ssoReceiveInterface], boolint(on)); err != nil {
				return err
			}
			if on {
				opt.set(FlagInterface)
			} else {
				opt.clear(FlagInterface)
			}
		}
	}
	return nil
}

func (opt *rawOpt) oobLen() (l int) {
	if opt.isset(FlagTTL) {
		l += syscall.CmsgSpace(1)
	}
	if sockOpts[ssoPacketInfo].name > 0 {
		if opt.isset(FlagSrc | FlagDst | FlagInterface) {
			l += syscall.CmsgSpace(sysSizeofInetPktinfo)
		}
	} else {
		if opt.isset(FlagDst) {
			l += syscall.CmsgSpace(net.IPv4len)
		}
		if opt.isset(FlagInterface) {
			l += syscall.CmsgSpace(syscall.SizeofSockaddrDatalink)
		}
	}
	return
}

func (opt *rawOpt) marshalControlMessage() (oob []byte) {
	var off int
	oob = make([]byte, opt.oobLen())
	if opt.isset(FlagTTL) {
		m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
		m.Level = ianaProtocolIP
		m.Type = sysIP_RECVTTL
		m.SetLen(syscall.CmsgLen(1))
		off += syscall.CmsgSpace(1)
	}
	if sockOpts[ssoPacketInfo].name > 0 {
		if opt.isset(FlagSrc | FlagDst | FlagInterface) {
			m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
			m.Level = ianaProtocolIP
			m.Type = sysIP_PKTINFO
			m.SetLen(syscall.CmsgLen(sysSizeofInetPktinfo))
			off += syscall.CmsgSpace(sysSizeofInetPktinfo)
		}
	} else {
		if opt.isset(FlagDst) {
			m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
			m.Level = ianaProtocolIP
			m.Type = sysIP_RECVDSTADDR
			m.SetLen(syscall.CmsgLen(net.IPv4len))
			off += syscall.CmsgSpace(net.IPv4len)
		}
		if opt.isset(FlagInterface) {
			m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
			m.Level = ianaProtocolIP
			m.Type = sysIP_RECVIF
			m.SetLen(syscall.CmsgLen(syscall.SizeofSockaddrDatalink))
			off += syscall.CmsgSpace(syscall.SizeofSockaddrDatalink)
		}
	}
	return
}

func (cm *ControlMessage) oobLen() (l int) {
	if sockOpts[ssoPacketInfo].name > 0 && (cm.Src.To4() != nil || cm.IfIndex != 0) {
		l += syscall.CmsgSpace(sysSizeofInetPktinfo)
	}
	return
}

func (cm *ControlMessage) parseControlMessage(m *syscall.SocketControlMessage) {
	switch m.Header.Type {
	case sysIP_RECVTTL:
		cm.TTL = int(*(*byte)(unsafe.Pointer(&m.Data[:1][0])))
	case sysIP_RECVDSTADDR:
		cm.Dst = m.Data[:net.IPv4len]
	case sysIP_RECVIF:
		sadl := (*syscall.SockaddrDatalink)(unsafe.Pointer(&m.Data[0]))
		cm.IfIndex = int(sadl.Index)
	case sysIP_PKTINFO:
		pi := (*sysInetPktinfo)(unsafe.Pointer(&m.Data[0]))
		cm.IfIndex = int(pi.Ifindex)
		cm.Dst = pi.Addr[:]
	}
}