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// Copyright 2015 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 icmp
import "golang.org/x/net/internal/iana"
// multipartMessageBodyDataLen takes b as an original datagram and
// exts as extensions, and returns a required length for message body
// and a required length for a padded original datagram in wire
// format.
func multipartMessageBodyDataLen(proto int, withOrigDgram bool, b []byte, exts []Extension) (bodyLen, dataLen int) {
bodyLen = 4 // length of leading octets
var extLen int
var rawExt bool // raw extension may contain an empty object
for _, ext := range exts {
extLen += ext.Len(proto)
if _, ok := ext.(*RawExtension); ok {
rawExt = true
}
}
if extLen > 0 && withOrigDgram {
dataLen = multipartMessageOrigDatagramLen(proto, b)
} else {
dataLen = len(b)
}
if extLen > 0 || rawExt {
bodyLen += 4 // length of extension header
}
bodyLen += dataLen + extLen
return bodyLen, dataLen
}
// multipartMessageOrigDatagramLen takes b as an original datagram,
// and returns a required length for a padded orignal datagram in wire
// format.
func multipartMessageOrigDatagramLen(proto int, b []byte) int {
roundup := func(b []byte, align int) int {
// According to RFC 4884, the padded original datagram
// field must contain at least 128 octets.
if len(b) < 128 {
return 128
}
r := len(b)
return (r + align - 1) &^ (align - 1)
}
switch proto {
case iana.ProtocolICMP:
return roundup(b, 4)
case iana.ProtocolIPv6ICMP:
return roundup(b, 8)
default:
return len(b)
}
}
// marshalMultipartMessageBody takes data as an original datagram and
// exts as extesnsions, and returns a binary encoding of message body.
// It can be used for non-multipart message bodies when exts is nil.
func marshalMultipartMessageBody(proto int, withOrigDgram bool, data []byte, exts []Extension) ([]byte, error) {
bodyLen, dataLen := multipartMessageBodyDataLen(proto, withOrigDgram, data, exts)
b := make([]byte, bodyLen)
copy(b[4:], data)
if len(exts) > 0 {
b[4+dataLen] = byte(extensionVersion << 4)
off := 4 + dataLen + 4 // leading octets, data, extension header
for _, ext := range exts {
switch ext := ext.(type) {
case *MPLSLabelStack:
if err := ext.marshal(proto, b[off:]); err != nil {
return nil, err
}
off += ext.Len(proto)
case *InterfaceInfo:
attrs, l := ext.attrsAndLen(proto)
if err := ext.marshal(proto, b[off:], attrs, l); err != nil {
return nil, err
}
off += ext.Len(proto)
case *InterfaceIdent:
if err := ext.marshal(proto, b[off:]); err != nil {
return nil, err
}
off += ext.Len(proto)
case *RawExtension:
copy(b[off:], ext.Data)
off += ext.Len(proto)
}
}
s := checksum(b[4+dataLen:])
b[4+dataLen+2] ^= byte(s)
b[4+dataLen+3] ^= byte(s >> 8)
if withOrigDgram {
switch proto {
case iana.ProtocolICMP:
b[1] = byte(dataLen / 4)
case iana.ProtocolIPv6ICMP:
b[0] = byte(dataLen / 8)
}
}
}
return b, nil
}
// parseMultipartMessageBody parses b as either a non-multipart
// message body or a multipart message body.
func parseMultipartMessageBody(proto int, typ Type, b []byte) ([]byte, []Extension, error) {
var l int
switch proto {
case iana.ProtocolICMP:
l = 4 * int(b[1])
case iana.ProtocolIPv6ICMP:
l = 8 * int(b[0])
}
if len(b) == 4 {
return nil, nil, nil
}
exts, l, err := parseExtensions(typ, b[4:], l)
if err != nil {
l = len(b) - 4
}
var data []byte
if l > 0 {
data = make([]byte, l)
copy(data, b[4:])
}
return data, exts, nil
}
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