tcpip/header/ipv4.go - third_party/netstack - Git at Google

 // Copyright 2016 The Netstack 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 header

 import (
 	"encoding/binary"

 	"github.com/google/netstack/tcpip"
 )

 const (
 	versIHL  = 0
 	tos      = 1
 	totalLen = 2
 	id       = 4
 	flagsFO  = 6
 	ttl      = 8
 	protocol = 9
 	checksum = 10
 	srcAddr  = 12
 	dstAddr  = 16
 )

 // IPv4Fields contains the fields of an IPv4 packet. It is used to describe the
 // fields of a packet that needs to be encoded.
 type IPv4Fields struct {
 	// IHL is the "internet header length" field of an IPv4 packet.
 	IHL uint8

 	// TOS is the "type of service" field of an IPv4 packet.
 	TOS uint8

 	// TotalLength is the "total length" field of an IPv4 packet.
 	TotalLength uint16

 	// ID is the "identification" field of an IPv4 packet.
 	ID uint16

 	// Flags is the "flags" field of an IPv4 packet.
 	Flags uint8

 	// FragmentOffset is the "fragment offset" field of an IPv4 packet.
 	FragmentOffset uint16

 	// TTL is the "time to live" field of an IPv4 packet.
 	TTL uint8

 	// Protocol is the "protocol" field of an IPv4 packet.
 	Protocol uint8

 	// Checksum is the "checksum" field of an IPv4 packet.
 	Checksum uint16

 	// SrcAddr is the "source ip address" of an IPv4 packet.
 	SrcAddr tcpip.Address

 	// DstAddr is the "destination ip address" of an IPv4 packet.
 	DstAddr tcpip.Address
 }

 // IPv4 represents an ipv4 header stored in a byte array.
 type IPv4 []byte

 const (
 	// IPv4MinimumSize is the minimum size of a valid IPv4 packet.
 	IPv4MinimumSize = 20

 	// IPv4MaximumHeaderSize is the maximum size of an IPv4 header. Given
 	// that there are only 4 bits to represents the header length in 32-bit
 	// units, the header cannot exceed 15*4 = 60 bytes.
 	IPv4MaximumHeaderSize = 60

 	// IPv4AddressSize is the size, in bytes, of an IPv4 address.
 	IPv4AddressSize = 4

 	// IPv4ProtocolNumber is IPv4's network protocol number.
 	IPv4ProtocolNumber tcpip.NetworkProtocolNumber = 0x0800

 	// IPv4Version is the version of the ipv4 procotol.
 	IPv4Version = 4

 	// IPv4Loopback is the loopback address of the IPv4 procotol.
 	IPv4Loopback tcpip.Address = "\x7f\x00\x00\x01"
 )

 // Flags that may be set in an IPv4 packet.
 const (
 	IPv4FlagMoreFragments = 1 << iota
 	IPv4FlagDontFragment
 )

 // IPVersion returns the version of IP used in the given packet. It returns -1
 // if the packet is not large enough to contain the version field.
 func IPVersion(b []byte) int {
 	// Length must be at least offset+length of version field.
 	if len(b) < versIHL+1 {
 		return -1
 	}
 	return int(b[versIHL] >> 4)
 }

 // HeaderLength returns the value of the "header length" field of the ipv4
 // header.
 func (b IPv4) HeaderLength() uint8 {
 	return (b[versIHL] & 0xf) * 4
 }

 // ID returns the value of the identifier field of the the ipv4 header.
 func (b IPv4) ID() uint16 {
 	return binary.BigEndian.Uint16(b[id:])
 }

 // Protocol returns the value of the protocol field of the the ipv4 header.
 func (b IPv4) Protocol() uint8 {
 	return b[protocol]
 }

 // Flags returns the "flags" field of the ipv4 header.
 func (b IPv4) Flags() uint8 {
 	return uint8(binary.BigEndian.Uint16(b[flagsFO:]) >> 13)
 }

 // TTL returns the "TTL" field of the ipv4 header.
 func (b IPv4) TTL() uint8 {
 	return b[ttl]
 }

 // FragmentOffset returns the "fragment offset" field of the ipv4 header.
 func (b IPv4) FragmentOffset() uint16 {
 	return binary.BigEndian.Uint16(b[flagsFO:]) << 3
 }

 // TotalLength returns the "total length" field of the ipv4 header.
 func (b IPv4) TotalLength() uint16 {
 	return binary.BigEndian.Uint16(b[totalLen:])
 }

 // Checksum returns the checksum field of the ipv4 header.
 func (b IPv4) Checksum() uint16 {
 	return binary.BigEndian.Uint16(b[checksum:])
 }

 // SourceAddress returns the "source address" field of the ipv4 header.
 func (b IPv4) SourceAddress() tcpip.Address {
 	return tcpip.Address(b[srcAddr : srcAddr+IPv4AddressSize])
 }

 // DestinationAddress returns the "destination address" field of the ipv4
 // header.
 func (b IPv4) DestinationAddress() tcpip.Address {
 	return tcpip.Address(b[dstAddr : dstAddr+IPv4AddressSize])
 }

 // TransportProtocol implements Network.TransportProtocol.
 func (b IPv4) TransportProtocol() tcpip.TransportProtocolNumber {
 	return tcpip.TransportProtocolNumber(b.Protocol())
 }

 // Payload implements Network.Payload.
 func (b IPv4) Payload() []byte {
 	return b[b.HeaderLength():][:b.PayloadLength()]
 }

 // PayloadLength returns the length of the payload portion of the ipv4 packet.
 func (b IPv4) PayloadLength() uint16 {
 	return b.TotalLength() - uint16(b.HeaderLength())
 }

 // TOS returns the "type of service" field of the ipv4 header.
 func (b IPv4) TOS() (uint8, uint32) {
 	return b[tos], 0
 }

 // SetTOS sets the "type of service" field of the ipv4 header.
 func (b IPv4) SetTOS(v uint8, _ uint32) {
 	b[tos] = v
 }

 // SetTotalLength sets the "total length" field of the ipv4 header.
 func (b IPv4) SetTotalLength(totalLength uint16) {
 	binary.BigEndian.PutUint16(b[totalLen:], totalLength)
 }

 // SetChecksum sets the checksum field of the ipv4 header.
 func (b IPv4) SetChecksum(v uint16) {
 	binary.BigEndian.PutUint16(b[checksum:], v)
 }

 // SetFlagsFragmentOffset sets the "flags" and "fragment offset" fields of the
 // ipv4 header.
 func (b IPv4) SetFlagsFragmentOffset(flags uint8, offset uint16) {
 	v := (uint16(flags) << 13) | (offset >> 3)
 	binary.BigEndian.PutUint16(b[flagsFO:], v)
 }

 // SetSourceAddress sets the "source address" field of the ipv4 header.
 func (b IPv4) SetSourceAddress(addr tcpip.Address) {
 	copy(b[srcAddr:srcAddr+IPv4AddressSize], addr)
 }

 // SetDestinationAddress sets the "destination address" field of the ipv4
 // header.
 func (b IPv4) SetDestinationAddress(addr tcpip.Address) {
 	copy(b[dstAddr:dstAddr+IPv4AddressSize], addr)
 }

 // CalculateChecksum calculates the checksum of the ipv4 header.
 func (b IPv4) CalculateChecksum() uint16 {
 	return Checksum(b[:b.HeaderLength()], 0)
 }

 // Encode encodes all the fields of the ipv4 header.
 func (b IPv4) Encode(i *IPv4Fields) {
 	b[versIHL] = (4 << 4) | ((i.IHL / 4) & 0xf)
 	b[tos] = i.TOS
 	b.SetTotalLength(i.TotalLength)
 	binary.BigEndian.PutUint16(b[id:], i.ID)
 	b.SetFlagsFragmentOffset(i.Flags, i.FragmentOffset)
 	b[ttl] = i.TTL
 	b[protocol] = i.Protocol
 	b.SetChecksum(i.Checksum)
 	copy(b[srcAddr:srcAddr+IPv4AddressSize], i.SrcAddr)
 	copy(b[dstAddr:dstAddr+IPv4AddressSize], i.DstAddr)
 }

 // EncodePartial updates the total length and checksum fields of ipv4 header,
 // taking in the partial checksum, which is the checksum of the header without
 // the total length and checksum fields. It is useful in cases when similar
 // packets are produced.
 func (b IPv4) EncodePartial(partialChecksum, totalLength uint16) {
 	b.SetTotalLength(totalLength)
 	checksum := Checksum(b[totalLen:totalLen+2], partialChecksum)
 	b.SetChecksum(^checksum)
 }

 // IsValid performs basic validation on the packet.
 func (b IPv4) IsValid(pktSize int) bool {
 	if len(b) < IPv4MinimumSize {
 		return false
 	}

 	hlen := int(b.HeaderLength())
 	tlen := int(b.TotalLength())
 	if hlen > tlen || tlen > pktSize {
 		return false
 	}

 	return true
 }

 // IsV4MulticastAddress determines if the provided address is an IPv4
 // multicast address (range 224.0.0.0 to 239.255.255.255).
 func IsV4MulticastAddress(addr tcpip.Address) bool {
 	if len(addr) != IPv4AddressSize {
 		return false
 	}
 	return (addr[0] & 0xf0) == 0xe0
 }
	// Copyright 2016 The Netstack 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 header

	import (
	"encoding/binary"

	"github.com/google/netstack/tcpip"
	)

	const (
	versIHL = 0
	tos = 1
	totalLen = 2
	id = 4
	flagsFO = 6
	ttl = 8
	protocol = 9
	checksum = 10
	srcAddr = 12
	dstAddr = 16
	)

	// IPv4Fields contains the fields of an IPv4 packet. It is used to describe the
	// fields of a packet that needs to be encoded.
	type IPv4Fields struct {
	// IHL is the "internet header length" field of an IPv4 packet.
	IHL uint8

	// TOS is the "type of service" field of an IPv4 packet.
	TOS uint8

	// TotalLength is the "total length" field of an IPv4 packet.
	TotalLength uint16

	// ID is the "identification" field of an IPv4 packet.
	ID uint16

	// Flags is the "flags" field of an IPv4 packet.
	Flags uint8

	// FragmentOffset is the "fragment offset" field of an IPv4 packet.
	FragmentOffset uint16

	// TTL is the "time to live" field of an IPv4 packet.
	TTL uint8

	// Protocol is the "protocol" field of an IPv4 packet.
	Protocol uint8

	// Checksum is the "checksum" field of an IPv4 packet.
	Checksum uint16

	// SrcAddr is the "source ip address" of an IPv4 packet.
	SrcAddr tcpip.Address

	// DstAddr is the "destination ip address" of an IPv4 packet.
	DstAddr tcpip.Address
	}

	// IPv4 represents an ipv4 header stored in a byte array.
	type IPv4 []byte

	const (
	// IPv4MinimumSize is the minimum size of a valid IPv4 packet.
	IPv4MinimumSize = 20

	// IPv4MaximumHeaderSize is the maximum size of an IPv4 header. Given
	// that there are only 4 bits to represents the header length in 32-bit
	// units, the header cannot exceed 15*4 = 60 bytes.
	IPv4MaximumHeaderSize = 60

	// IPv4AddressSize is the size, in bytes, of an IPv4 address.
	IPv4AddressSize = 4

	// IPv4ProtocolNumber is IPv4's network protocol number.
	IPv4ProtocolNumber tcpip.NetworkProtocolNumber = 0x0800

	// IPv4Version is the version of the ipv4 procotol.
	IPv4Version = 4

	// IPv4Loopback is the loopback address of the IPv4 procotol.
	IPv4Loopback tcpip.Address = "\x7f\x00\x00\x01"
	)

	// Flags that may be set in an IPv4 packet.
	const (
	IPv4FlagMoreFragments = 1 << iota
	IPv4FlagDontFragment
	)

	// IPVersion returns the version of IP used in the given packet. It returns -1
	// if the packet is not large enough to contain the version field.
	func IPVersion(b []byte) int {
	// Length must be at least offset+length of version field.
	if len(b) < versIHL+1 {
	return -1
	}
	return int(b[versIHL] >> 4)
	}

	// HeaderLength returns the value of the "header length" field of the ipv4
	// header.
	func (b IPv4) HeaderLength() uint8 {
	return (b[versIHL] & 0xf) * 4
	}

	// ID returns the value of the identifier field of the the ipv4 header.
	func (b IPv4) ID() uint16 {
	return binary.BigEndian.Uint16(b[id:])
	}

	// Protocol returns the value of the protocol field of the the ipv4 header.
	func (b IPv4) Protocol() uint8 {
	return b[protocol]
	}

	// Flags returns the "flags" field of the ipv4 header.
	func (b IPv4) Flags() uint8 {
	return uint8(binary.BigEndian.Uint16(b[flagsFO:]) >> 13)
	}

	// TTL returns the "TTL" field of the ipv4 header.
	func (b IPv4) TTL() uint8 {
	return b[ttl]
	}

	// FragmentOffset returns the "fragment offset" field of the ipv4 header.
	func (b IPv4) FragmentOffset() uint16 {
	return binary.BigEndian.Uint16(b[flagsFO:]) << 3
	}

	// TotalLength returns the "total length" field of the ipv4 header.
	func (b IPv4) TotalLength() uint16 {
	return binary.BigEndian.Uint16(b[totalLen:])
	}

	// Checksum returns the checksum field of the ipv4 header.
	func (b IPv4) Checksum() uint16 {
	return binary.BigEndian.Uint16(b[checksum:])
	}

	// SourceAddress returns the "source address" field of the ipv4 header.
	func (b IPv4) SourceAddress() tcpip.Address {
	return tcpip.Address(b[srcAddr : srcAddr+IPv4AddressSize])
	}

	// DestinationAddress returns the "destination address" field of the ipv4
	// header.
	func (b IPv4) DestinationAddress() tcpip.Address {
	return tcpip.Address(b[dstAddr : dstAddr+IPv4AddressSize])
	}

	// TransportProtocol implements Network.TransportProtocol.
	func (b IPv4) TransportProtocol() tcpip.TransportProtocolNumber {
	return tcpip.TransportProtocolNumber(b.Protocol())
	}

	// Payload implements Network.Payload.
	func (b IPv4) Payload() []byte {
	return b[b.HeaderLength():][:b.PayloadLength()]
	}

	// PayloadLength returns the length of the payload portion of the ipv4 packet.
	func (b IPv4) PayloadLength() uint16 {
	return b.TotalLength() - uint16(b.HeaderLength())
	}

	// TOS returns the "type of service" field of the ipv4 header.
	func (b IPv4) TOS() (uint8, uint32) {
	return b[tos], 0
	}

	// SetTOS sets the "type of service" field of the ipv4 header.
	func (b IPv4) SetTOS(v uint8, _ uint32) {
	b[tos] = v
	}

	// SetTotalLength sets the "total length" field of the ipv4 header.
	func (b IPv4) SetTotalLength(totalLength uint16) {
	binary.BigEndian.PutUint16(b[totalLen:], totalLength)
	}

	// SetChecksum sets the checksum field of the ipv4 header.
	func (b IPv4) SetChecksum(v uint16) {
	binary.BigEndian.PutUint16(b[checksum:], v)
	}

	// SetFlagsFragmentOffset sets the "flags" and "fragment offset" fields of the
	// ipv4 header.
	func (b IPv4) SetFlagsFragmentOffset(flags uint8, offset uint16) {
	v := (uint16(flags) << 13) \| (offset >> 3)
	binary.BigEndian.PutUint16(b[flagsFO:], v)
	}

	// SetSourceAddress sets the "source address" field of the ipv4 header.
	func (b IPv4) SetSourceAddress(addr tcpip.Address) {
	copy(b[srcAddr:srcAddr+IPv4AddressSize], addr)
	}

	// SetDestinationAddress sets the "destination address" field of the ipv4
	// header.
	func (b IPv4) SetDestinationAddress(addr tcpip.Address) {
	copy(b[dstAddr:dstAddr+IPv4AddressSize], addr)
	}

	// CalculateChecksum calculates the checksum of the ipv4 header.
	func (b IPv4) CalculateChecksum() uint16 {
	return Checksum(b[:b.HeaderLength()], 0)
	}

	// Encode encodes all the fields of the ipv4 header.
	func (b IPv4) Encode(i *IPv4Fields) {
	b[versIHL] = (4 << 4) \| ((i.IHL / 4) & 0xf)
	b[tos] = i.TOS
	b.SetTotalLength(i.TotalLength)
	binary.BigEndian.PutUint16(b[id:], i.ID)
	b.SetFlagsFragmentOffset(i.Flags, i.FragmentOffset)
	b[ttl] = i.TTL
	b[protocol] = i.Protocol
	b.SetChecksum(i.Checksum)
	copy(b[srcAddr:srcAddr+IPv4AddressSize], i.SrcAddr)
	copy(b[dstAddr:dstAddr+IPv4AddressSize], i.DstAddr)
	}

	// EncodePartial updates the total length and checksum fields of ipv4 header,
	// taking in the partial checksum, which is the checksum of the header without
	// the total length and checksum fields. It is useful in cases when similar
	// packets are produced.
	func (b IPv4) EncodePartial(partialChecksum, totalLength uint16) {
	b.SetTotalLength(totalLength)
	checksum := Checksum(b[totalLen:totalLen+2], partialChecksum)
	b.SetChecksum(^checksum)
	}

	// IsValid performs basic validation on the packet.
	func (b IPv4) IsValid(pktSize int) bool {
	if len(b) < IPv4MinimumSize {
	return false
	}

	hlen := int(b.HeaderLength())
	tlen := int(b.TotalLength())
	if hlen > tlen \|\| tlen > pktSize {
	return false
	}

	return true
	}

	// IsV4MulticastAddress determines if the provided address is an IPv4
	// multicast address (range 224.0.0.0 to 239.255.255.255).
	func IsV4MulticastAddress(addr tcpip.Address) bool {
	if len(addr) != IPv4AddressSize {
	return false
	}
	return (addr[0] & 0xf0) == 0xe0
	}