github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/net/icmp/packettoobig.go (about) 1 // Copyright 2014 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package icmp 6 7 // A PacketTooBig represents an ICMP packet too big message body. 8 type PacketTooBig struct { 9 MTU int // maximum transmission unit of the nexthop link 10 Data []byte // data, known as original datagram field 11 } 12 13 // Len implements the Len method of MessageBody interface. 14 func (p *PacketTooBig) Len(proto int) int { 15 if p == nil { 16 return 0 17 } 18 return 4 + len(p.Data) 19 } 20 21 // Marshal implements the Marshal method of MessageBody interface. 22 func (p *PacketTooBig) Marshal(proto int) ([]byte, error) { 23 b := make([]byte, 4+len(p.Data)) 24 b[0], b[1], b[2], b[3] = byte(p.MTU>>24), byte(p.MTU>>16), byte(p.MTU>>8), byte(p.MTU) 25 copy(b[4:], p.Data) 26 return b, nil 27 } 28 29 // parsePacketTooBig parses b as an ICMP packet too big message body. 30 func parsePacketTooBig(proto int, b []byte) (MessageBody, error) { 31 bodyLen := len(b) 32 if bodyLen < 4 { 33 return nil, errMessageTooShort 34 } 35 p := &PacketTooBig{MTU: int(b[0])<<24 | int(b[1])<<16 | int(b[2])<<8 | int(b[3])} 36 if bodyLen > 4 { 37 p.Data = make([]byte, bodyLen-4) 38 copy(p.Data, b[4:]) 39 } 40 return p, nil 41 }