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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package header
import (
"encoding/binary"
"gvisor.dev/gvisor/pkg/tcpip"
)
// ICMPv4 represents an ICMPv4 header stored in a byte array.
type ICMPv4 []byte
const (
// ICMPv4PayloadOffset defines the start of ICMP payload.
ICMPv4PayloadOffset = 8
// ICMPv4MinimumSize is the minimum size of a valid ICMP packet.
ICMPv4MinimumSize = 8
// ICMPv4MinimumErrorPayloadSize Is the smallest number of bytes of an
// errant packet's transport layer that an ICMP error type packet should
// attempt to send as per RFC 792 (see each type) and RFC 1122
// section 3.2.2 which states:
// Every ICMP error message includes the Internet header and at
// least the first 8 data octets of the datagram that triggered
// the error; more than 8 octets MAY be sent; this header and data
// MUST be unchanged from the received datagram.
//
// RFC 792 shows:
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Type | Code | Checksum |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | unused |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Internet Header + 64 bits of Original Data Datagram |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ICMPv4MinimumErrorPayloadSize = 8
// ICMPv4ProtocolNumber is the ICMP transport protocol number.
ICMPv4ProtocolNumber tcpip.TransportProtocolNumber = 1
// icmpv4ChecksumOffset is the offset of the checksum field
// in an ICMPv4 message.
icmpv4ChecksumOffset = 2
// icmpv4MTUOffset is the offset of the MTU field
// in an ICMPv4FragmentationNeeded message.
icmpv4MTUOffset = 6
// icmpv4IdentOffset is the offset of the ident field
// in an ICMPv4EchoRequest/Reply message.
icmpv4IdentOffset = 4
// icmpv4PointerOffset is the offset of the pointer field
// in an ICMPv4ParamProblem message.
icmpv4PointerOffset = 4
// icmpv4SequenceOffset is the offset of the sequence field
// in an ICMPv4EchoRequest/Reply message.
icmpv4SequenceOffset = 6
)
// ICMPv4Type is the ICMP type field described in RFC 792.
type ICMPv4Type byte
// ICMPv4Code is the ICMP code field described in RFC 792.
type ICMPv4Code byte
// Typical values of ICMPv4Type defined in RFC 792.
const (
ICMPv4EchoReply ICMPv4Type = 0
ICMPv4DstUnreachable ICMPv4Type = 3
ICMPv4SrcQuench ICMPv4Type = 4
ICMPv4Redirect ICMPv4Type = 5
ICMPv4Echo ICMPv4Type = 8
ICMPv4TimeExceeded ICMPv4Type = 11
ICMPv4ParamProblem ICMPv4Type = 12
ICMPv4Timestamp ICMPv4Type = 13
ICMPv4TimestampReply ICMPv4Type = 14
ICMPv4InfoRequest ICMPv4Type = 15
ICMPv4InfoReply ICMPv4Type = 16
)
// ICMP codes for ICMPv4 Time Exceeded messages as defined in RFC 792.
const (
ICMPv4TTLExceeded ICMPv4Code = 0
ICMPv4ReassemblyTimeout ICMPv4Code = 1
)
// ICMP codes for ICMPv4 Destination Unreachable messages as defined in RFC 792.
const (
ICMPv4NetUnreachable ICMPv4Code = 0
ICMPv4HostUnreachable ICMPv4Code = 1
ICMPv4ProtoUnreachable ICMPv4Code = 2
ICMPv4PortUnreachable ICMPv4Code = 3
ICMPv4FragmentationNeeded ICMPv4Code = 4
)
// ICMPv4UnusedCode is a code to use in ICMP messages where no code is needed.
const ICMPv4UnusedCode ICMPv4Code = 0
// Type is the ICMP type field.
func (b ICMPv4) Type() ICMPv4Type { return ICMPv4Type(b[0]) }
// SetType sets the ICMP type field.
func (b ICMPv4) SetType(t ICMPv4Type) { b[0] = byte(t) }
// Code is the ICMP code field. Its meaning depends on the value of Type.
func (b ICMPv4) Code() ICMPv4Code { return ICMPv4Code(b[1]) }
// SetCode sets the ICMP code field.
func (b ICMPv4) SetCode(c ICMPv4Code) { b[1] = byte(c) }
// Pointer returns the pointer field in a Parameter Problem packet.
func (b ICMPv4) Pointer() byte { return b[icmpv4PointerOffset] }
// SetPointer sets the pointer field in a Parameter Problem packet.
func (b ICMPv4) SetPointer(c byte) { b[icmpv4PointerOffset] = c }
// Checksum is the ICMP checksum field.
func (b ICMPv4) Checksum() uint16 {
return binary.BigEndian.Uint16(b[icmpv4ChecksumOffset:])
}
// SetChecksum sets the ICMP checksum field.
func (b ICMPv4) SetChecksum(checksum uint16) {
binary.BigEndian.PutUint16(b[icmpv4ChecksumOffset:], checksum)
}
// SourcePort implements Transport.SourcePort.
func (ICMPv4) SourcePort() uint16 {
return 0
}
// DestinationPort implements Transport.DestinationPort.
func (ICMPv4) DestinationPort() uint16 {
return 0
}
// SetSourcePort implements Transport.SetSourcePort.
func (ICMPv4) SetSourcePort(uint16) {
}
// SetDestinationPort implements Transport.SetDestinationPort.
func (ICMPv4) SetDestinationPort(uint16) {
}
// Payload implements Transport.Payload.
func (b ICMPv4) Payload() []byte {
return b[ICMPv4PayloadOffset:]
}
// MTU retrieves the MTU field from an ICMPv4 message.
func (b ICMPv4) MTU() uint16 {
return binary.BigEndian.Uint16(b[icmpv4MTUOffset:])
}
// SetMTU sets the MTU field from an ICMPv4 message.
func (b ICMPv4) SetMTU(mtu uint16) {
binary.BigEndian.PutUint16(b[icmpv4MTUOffset:], mtu)
}
// Ident retrieves the Ident field from an ICMPv4 message.
func (b ICMPv4) Ident() uint16 {
return binary.BigEndian.Uint16(b[icmpv4IdentOffset:])
}
// SetIdent sets the Ident field from an ICMPv4 message.
func (b ICMPv4) SetIdent(ident uint16) {
binary.BigEndian.PutUint16(b[icmpv4IdentOffset:], ident)
}
// Sequence retrieves the Sequence field from an ICMPv4 message.
func (b ICMPv4) Sequence() uint16 {
return binary.BigEndian.Uint16(b[icmpv4SequenceOffset:])
}
// SetSequence sets the Sequence field from an ICMPv4 message.
func (b ICMPv4) SetSequence(sequence uint16) {
binary.BigEndian.PutUint16(b[icmpv4SequenceOffset:], sequence)
}
// ICMPv4Checksum calculates the ICMP checksum over the provided ICMP header,
// and payload.
func ICMPv4Checksum(h ICMPv4, payloadCsum uint16) uint16 {
xsum := payloadCsum
// h[2:4] is the checksum itself, skip it to avoid checksumming the checksum.
xsum = Checksum(h[:2], xsum)
xsum = Checksum(h[4:], xsum)
return ^xsum
}
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