route/sys.go

// 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.

//go:build darwin || dragonfly || freebsd || netbsd || openbsd

package route

import (
	"syscall"
	"unsafe"
)

var (
	nativeEndian binaryByteOrder
	kernelAlign  int
	rtmVersion   byte
	wireFormats  map[int]*wireFormat
)

func init() {
	i := uint32(1)
	b := (*[4]byte)(unsafe.Pointer(&i))
	if b[0] == 1 {
		nativeEndian = littleEndian
	} else {
		nativeEndian = bigEndian
	}
	// might get overridden in probeRoutingStack
	rtmVersion = syscall.RTM_VERSION
	kernelAlign, wireFormats = probeRoutingStack()
}

func roundup(l int) int {
	if l == 0 {
		return kernelAlign
	}
	return (l + kernelAlign - 1) &^ (kernelAlign - 1)
}

type wireFormat struct {
	extOff  int // offset of header extension
	bodyOff int // offset of message body
	parse   func(RIBType, []byte) (Message, error)
}