You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: sys_freebsd.go
    path of file: ./repos/go-starter-kit/vendor/golang.org/x/net/route
    
    the code of the file until where you have to start completion: // Copyright 2016 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 route

import (
	"syscall"
	"unsafe"
)

func (typ RIBType) parseable() bool { return true }

// A RouteMetrics represents route metrics.
type RouteMetrics
    
func probeRoutingStack() (int, map[int]*wireFormat) {
	var p uintptr
	wordSize := int(unsafe.Sizeof(p))
	align := int(unsafe.Sizeof(p))
	// In the case of kern.supported_archs="amd64 i386", we need
	// to know the underlying kernel's architecture because the
	// alignment for routing facilities are set at the build time
	// of the kernel.
	conf, _ := syscall.Sysctl("kern.conftxt")
	for i, j := 0, 0; j < len(conf); j++ {
		if conf[j] != '\n' {
			continue
		}
		s := conf[i:j]
		i = j + 1
		if len(s) > len("machine") && s[:len("machine")] == "machine" {
			s = s[len("machine"):]
			for k := 0; k < len(s); k++ {
				if s[k] == ' ' || s[k] == '\t' {
					s = s[1:]
				}
				break
			}
			if s == "amd64" {
				align = 8
			}
			break
		}
	}
	var rtm, ifm, ifam, ifmam, ifanm *wireFormat
	if align != wordSize { // 386 emulation on amd64
		rtm = &wireFormat{extOff: sizeofRtMsghdrFreeBSD10Emu - sizeofRtMetricsFreeBSD10Emu, bodyOff: sizeofRtMsghdrFreeBSD10Emu}
		ifm = &wireFormat{extOff: 16}
		ifam = &wireFormat{extOff: sizeofIfaMsghdrFreeBSD10Emu, bodyOff: sizeofIfaMsghdrFreeBSD10Emu}
		ifmam = &wireFormat{extOff: sizeofIfmaMsghdrFreeBSD10Emu, bodyOff: sizeofIfmaMsghdrFreeBSD10Emu}
		ifanm = &wireFormat{extOff: sizeofIfAnnouncemsghdrFreeBSD10Emu, bodyOff: sizeofIfAnnouncemsghdrFreeBSD10Emu}
	} else {
		rtm = &wireFormat{extOff: sizeofRtMsghdrFreeBSD10 - sizeofRtMetricsFreeBSD10, bodyOff: sizeofRtMsghdrFreeBSD10}
		ifm = &wireFormat{extOff: 16}
		ifam = &wireFormat{extOff: sizeofIfaMsghdrFreeBSD10, bodyOff: sizeofIfaMsghdrFreeBSD10}
		ifmam = &wireFormat{extOff: sizeofIfmaMsghdrFreeBSD10, bodyOff: sizeofIfmaMsghdrFreeBSD10}
		ifanm = &wireFormat{extOff: sizeofIfAnnouncemsghdrFreeBSD10, bodyOff: sizeofIfAnnouncemsghdrFreeBSD10}
	}
	rel, _ := syscall.SysctlUint32("kern.osreldate")
	switch {
	case rel < 800000:
		if align != wordSize { // 386 emulation on amd64
			ifm.bodyOff = sizeofIfMsghdrFreeBSD7Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD7
		}
	case 800000 <= rel && rel < 900000:
		if align != wordSize { // 386 emulation on amd64
			ifm.bodyOff = sizeofIfMsghdrFreeBSD8Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD8
		}
	case 900000 <= rel && rel < 1000000:
		if align != wordSize { // 386 emulation on amd64
			ifm.bodyOff = sizeofIfMsghdrFreeBSD9Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD9
		}
	case 1000000 <= rel && rel < 1100000:
		if align != wordSize { // 386 emulation on amd64
			ifm.bodyOff = sizeofIfMsghdrFreeBSD10Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD10
		}
	default:
		if align != wordSize { // 386 emulation on amd64
			ifm.bodyOff = sizeofIfMsghdrFreeBSD11Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD11
		}
	}
	rtm.parse = rtm.parseRouteMessage
	ifm.parse = ifm.parseInterfaceMessage
	ifam.parse = ifam.parseInterfaceAddrMessage
	ifmam.parse = ifmam.parseInterfaceMulticastAddrMessage
	ifanm.parse = ifanm.parseInterfaceAnnounceMessage
	return align, map[int]*wireFormat{
		sysRTM_ADD:        rtm,
		sysRTM_DELETE:     rtm,
		sysRTM_CHANGE:     rtm,
		sysRTM_GET:        rtm,
		sysRTM_LOSING:     rtm,
		sysRTM_REDIRECT:   rtm,
		sysRTM_MISS:       rtm,
		sysRTM_LOCK:       rtm,
		sysRTM_RESOLVE:    rtm,
		sysRTM_NEWADDR:    ifam,
		sysRTM_DELADDR:    ifam,
		sysRTM_IFINFO:     ifm,
		sysRTM_NEWMADDR:   ifmam,
		sysRTM_DELMADDR:   ifmam,
		sysRTM_IFANNOUNCE: ifanm,
	}
}