--- /dev/null
+// 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.
+
+// Package icmp provides basic functions for the manipulation of
+// messages used in the Internet Control Message Protocols,
+// ICMPv4 and ICMPv6.
+//
+// ICMPv4 and ICMPv6 are defined in RFC 792 and RFC 4443.
+// Multi-part message support for ICMP is defined in RFC 4884.
+// ICMP extensions for MPLS are defined in RFC 4950.
+// ICMP extensions for interface and next-hop identification are
+// defined in RFC 5837.
+package icmp // import "golang.org/x/net/icmp"
+
+import (
+ "encoding/binary"
+ "errors"
+ "net"
+ "syscall"
+
+ "golang.org/x/net/internal/iana"
+ "golang.org/x/net/ipv4"
+ "golang.org/x/net/ipv6"
+)
+
+// BUG(mikio): This package is not implemented on NaCl and Plan 9.
+
+var (
+ errMessageTooShort = errors.New("message too short")
+ errHeaderTooShort = errors.New("header too short")
+ errBufferTooShort = errors.New("buffer too short")
+ errOpNoSupport = errors.New("operation not supported")
+ errNoExtension = errors.New("no extension")
+ errInvalidExtension = errors.New("invalid extension")
+)
+
+func checksum(b []byte) uint16 {
+ csumcv := len(b) - 1 // checksum coverage
+ s := uint32(0)
+ for i := 0; i < csumcv; i += 2 {
+ s += uint32(b[i+1])<<8 | uint32(b[i])
+ }
+ if csumcv&1 == 0 {
+ s += uint32(b[csumcv])
+ }
+ s = s>>16 + s&0xffff
+ s = s + s>>16
+ return ^uint16(s)
+}
+
+// A Type represents an ICMP message type.
+type Type interface {
+ Protocol() int
+}
+
+// A Message represents an ICMP message.
+type Message struct {
+ Type Type // type, either ipv4.ICMPType or ipv6.ICMPType
+ Code int // code
+ Checksum int // checksum
+ Body MessageBody // body
+}
+
+// Marshal returns the binary encoding of the ICMP message m.
+//
+// For an ICMPv4 message, the returned message always contains the
+// calculated checksum field.
+//
+// For an ICMPv6 message, the returned message contains the calculated
+// checksum field when psh is not nil, otherwise the kernel will
+// compute the checksum field during the message transmission.
+// When psh is not nil, it must be the pseudo header for IPv6.
+func (m *Message) Marshal(psh []byte) ([]byte, error) {
+ var mtype int
+ switch typ := m.Type.(type) {
+ case ipv4.ICMPType:
+ mtype = int(typ)
+ case ipv6.ICMPType:
+ mtype = int(typ)
+ default:
+ return nil, syscall.EINVAL
+ }
+ b := []byte{byte(mtype), byte(m.Code), 0, 0}
+ if m.Type.Protocol() == iana.ProtocolIPv6ICMP && psh != nil {
+ b = append(psh, b...)
+ }
+ if m.Body != nil && m.Body.Len(m.Type.Protocol()) != 0 {
+ mb, err := m.Body.Marshal(m.Type.Protocol())
+ if err != nil {
+ return nil, err
+ }
+ b = append(b, mb...)
+ }
+ if m.Type.Protocol() == iana.ProtocolIPv6ICMP {
+ if psh == nil { // cannot calculate checksum here
+ return b, nil
+ }
+ off, l := 2*net.IPv6len, len(b)-len(psh)
+ binary.BigEndian.PutUint32(b[off:off+4], uint32(l))
+ }
+ s := checksum(b)
+ // Place checksum back in header; using ^= avoids the
+ // assumption the checksum bytes are zero.
+ b[len(psh)+2] ^= byte(s)
+ b[len(psh)+3] ^= byte(s >> 8)
+ return b[len(psh):], nil
+}
+
+var parseFns = map[Type]func(int, []byte) (MessageBody, error){
+ ipv4.ICMPTypeDestinationUnreachable: parseDstUnreach,
+ ipv4.ICMPTypeTimeExceeded: parseTimeExceeded,
+ ipv4.ICMPTypeParameterProblem: parseParamProb,
+
+ ipv4.ICMPTypeEcho: parseEcho,
+ ipv4.ICMPTypeEchoReply: parseEcho,
+
+ ipv6.ICMPTypeDestinationUnreachable: parseDstUnreach,
+ ipv6.ICMPTypePacketTooBig: parsePacketTooBig,
+ ipv6.ICMPTypeTimeExceeded: parseTimeExceeded,
+ ipv6.ICMPTypeParameterProblem: parseParamProb,
+
+ ipv6.ICMPTypeEchoRequest: parseEcho,
+ ipv6.ICMPTypeEchoReply: parseEcho,
+}
+
+// ParseMessage parses b as an ICMP message.
+// Proto must be either the ICMPv4 or ICMPv6 protocol number.
+func ParseMessage(proto int, b []byte) (*Message, error) {
+ if len(b) < 4 {
+ return nil, errMessageTooShort
+ }
+ var err error
+ m := &Message{Code: int(b[1]), Checksum: int(binary.BigEndian.Uint16(b[2:4]))}
+ switch proto {
+ case iana.ProtocolICMP:
+ m.Type = ipv4.ICMPType(b[0])
+ case iana.ProtocolIPv6ICMP:
+ m.Type = ipv6.ICMPType(b[0])
+ default:
+ return nil, syscall.EINVAL
+ }
+ if fn, ok := parseFns[m.Type]; !ok {
+ m.Body, err = parseDefaultMessageBody(proto, b[4:])
+ } else {
+ m.Body, err = fn(proto, b[4:])
+ }
+ if err != nil {
+ return nil, err
+ }
+ return m, nil
+}
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