| // 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 |
| |
| import "encoding/binary" |
| |
| // An Echo represents an ICMP echo request or reply message body. |
| type Echo struct { |
| ID int // identifier |
| Seq int // sequence number |
| Data []byte // data |
| } |
| |
| // Len implements the Len method of MessageBody interface. |
| func (p *Echo) Len(proto int) int { |
| if p == nil { |
| return 0 |
| } |
| return 4 + len(p.Data) |
| } |
| |
| // Marshal implements the Marshal method of MessageBody interface. |
| func (p *Echo) Marshal(proto int) ([]byte, error) { |
| b := make([]byte, 4+len(p.Data)) |
| binary.BigEndian.PutUint16(b[:2], uint16(p.ID)) |
| binary.BigEndian.PutUint16(b[2:4], uint16(p.Seq)) |
| copy(b[4:], p.Data) |
| return b, nil |
| } |
| |
| // parseEcho parses b as an ICMP echo request or reply message body. |
| func parseEcho(proto int, b []byte) (MessageBody, error) { |
| bodyLen := len(b) |
| if bodyLen < 4 { |
| return nil, errMessageTooShort |
| } |
| p := &Echo{ID: int(binary.BigEndian.Uint16(b[:2])), Seq: int(binary.BigEndian.Uint16(b[2:4]))} |
| if bodyLen > 4 { |
| p.Data = make([]byte, bodyLen-4) |
| copy(p.Data, b[4:]) |
| } |
| return p, nil |
| } |