diff options
Diffstat (limited to 'pkg/tcpip/header/ipv4.go')
| -rw-r--r-- | pkg/tcpip/header/ipv4.go | 493 |
1 files changed, 463 insertions, 30 deletions
diff --git a/pkg/tcpip/header/ipv4.go b/pkg/tcpip/header/ipv4.go index 4c6e4be64..961b77628 100644 --- a/pkg/tcpip/header/ipv4.go +++ b/pkg/tcpip/header/ipv4.go @@ -16,6 +16,7 @@ package header import ( "encoding/binary" + "errors" "fmt" "gvisor.dev/gvisor/pkg/tcpip" @@ -38,7 +39,6 @@ import ( // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Options | Padding | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -// const ( versIHL = 0 tos = 1 @@ -93,7 +93,7 @@ type IPv4Fields struct { DstAddr tcpip.Address } -// IPv4 represents an ipv4 header stored in a byte array. +// IPv4 is an IPv4 header. // Most of the methods of IPv4 access to the underlying slice without // checking the boundaries and could panic because of 'index out of range'. // Always call IsValid() to validate an instance of IPv4 before using other @@ -106,10 +106,13 @@ const ( 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. + // that there are only 4 bits (max 0xF (15)) to represent the header length + // in 32-bit (4 byte) units, the header cannot exceed 15*4 = 60 bytes. IPv4MaximumHeaderSize = 60 + // IPv4MaximumOptionsSize is the largest size the IPv4 options can be. + IPv4MaximumOptionsSize = IPv4MaximumHeaderSize - IPv4MinimumSize + // IPv4MaximumPayloadSize is the maximum size of a valid IPv4 payload. // // Linux limits this to 65,515 octets (the max IP datagram size - the IPv4 @@ -130,7 +133,7 @@ const ( // IPv4ProtocolNumber is IPv4's network protocol number. IPv4ProtocolNumber tcpip.NetworkProtocolNumber = 0x0800 - // IPv4Version is the version of the ipv4 protocol. + // IPv4Version is the version of the IPv4 protocol. IPv4Version = 4 // IPv4AllSystems is the all systems IPv4 multicast address as per @@ -148,6 +151,13 @@ const ( // packet that every IPv4 capable host must be able to // process/reassemble. IPv4MinimumProcessableDatagramSize = 576 + + // IPv4MinimumMTU is the minimum MTU required by IPv4, per RFC 791, + // section 3.2: + // Every internet module must be able to forward a datagram of 68 octets + // without further fragmentation. This is because an internet header may be + // up to 60 octets, and the minimum fragment is 8 octets. + IPv4MinimumMTU = 68 ) // Flags that may be set in an IPv4 packet. @@ -191,14 +201,13 @@ func IPVersion(b []byte) int { // Internet Header Length is the length of the internet header in 32 // bit words, and thus points to the beginning of the data. Note that // the minimum value for a correct header is 5. -// const ( ipVersionShift = 4 ipIHLMask = 0x0f IPv4IHLStride = 4 ) -// HeaderLength returns the value of the "header length" field of the ipv4 +// HeaderLength returns the value of the "header length" field of the IPv4 // header. The length returned is in bytes. func (b IPv4) HeaderLength() uint8 { return (b[versIHL] & ipIHLMask) * IPv4IHLStride @@ -212,17 +221,17 @@ func (b IPv4) SetHeaderLength(hdrLen uint8) { b[versIHL] = (IPv4Version << ipVersionShift) | ((hdrLen / IPv4IHLStride) & ipIHLMask) } -// ID returns the value of the identifier field of the ipv4 header. +// ID returns the value of the identifier field of the IPv4 header. func (b IPv4) ID() uint16 { return binary.BigEndian.Uint16(b[id:]) } -// Protocol returns the value of the protocol field of the ipv4 header. +// Protocol returns the value of the protocol field of the IPv4 header. func (b IPv4) Protocol() uint8 { return b[protocol] } -// Flags returns the "flags" field of the ipv4 header. +// Flags returns the "flags" field of the IPv4 header. func (b IPv4) Flags() uint8 { return uint8(binary.BigEndian.Uint16(b[flagsFO:]) >> 13) } @@ -232,41 +241,44 @@ func (b IPv4) More() bool { return b.Flags()&IPv4FlagMoreFragments != 0 } -// TTL returns the "TTL" field of the ipv4 header. +// 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. +// 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. +// TotalLength returns the "total length" field of the IPv4 header. func (b IPv4) TotalLength() uint16 { return binary.BigEndian.Uint16(b[IPv4TotalLenOffset:]) } -// Checksum returns the checksum field of the ipv4 header. +// 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. +// 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 +// DestinationAddress returns the "destination address" field of the IPv4 // header. func (b IPv4) DestinationAddress() tcpip.Address { return tcpip.Address(b[dstAddr : dstAddr+IPv4AddressSize]) } -// Options returns a a buffer holding the options. -func (b IPv4) Options() []byte { +// IPv4Options is a buffer that holds all the raw IP options. +type IPv4Options []byte + +// Options returns a buffer holding the options. +func (b IPv4) Options() IPv4Options { hdrLen := b.HeaderLength() - return b[options:hdrLen:hdrLen] + return IPv4Options(b[options:hdrLen:hdrLen]) } // TransportProtocol implements Network.TransportProtocol. @@ -279,17 +291,17 @@ func (b IPv4) Payload() []byte { return b[b.HeaderLength():][:b.PayloadLength()] } -// PayloadLength returns the length of the payload portion of the ipv4 packet. +// 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. +// 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. +// SetTOS sets the "type of service" field of the IPv4 header. func (b IPv4) SetTOS(v uint8, _ uint32) { b[tos] = v } @@ -299,18 +311,18 @@ func (b IPv4) SetTTL(v byte) { b[ttl] = v } -// SetTotalLength sets the "total length" field of the ipv4 header. +// SetTotalLength sets the "total length" field of the IPv4 header. func (b IPv4) SetTotalLength(totalLength uint16) { binary.BigEndian.PutUint16(b[IPv4TotalLenOffset:], totalLength) } -// SetChecksum sets the checksum field of the ipv4 header. +// 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. +// IPv4 header. func (b IPv4) SetFlagsFragmentOffset(flags uint8, offset uint16) { v := (uint16(flags) << 13) | (offset >> 3) binary.BigEndian.PutUint16(b[flagsFO:], v) @@ -321,23 +333,23 @@ func (b IPv4) SetID(v uint16) { binary.BigEndian.PutUint16(b[id:], v) } -// SetSourceAddress sets the "source address" field of the ipv4 header. +// 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 +// 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. +// 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. +// Encode encodes all the fields of the IPv4 header. func (b IPv4) Encode(i *IPv4Fields) { b.SetHeaderLength(i.IHL) b[tos] = i.TOS @@ -351,7 +363,7 @@ func (b IPv4) Encode(i *IPv4Fields) { copy(b[dstAddr:dstAddr+IPv4AddressSize], i.DstAddr) } -// EncodePartial updates the total length and checksum fields of ipv4 header, +// 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. @@ -398,3 +410,424 @@ func IsV4LoopbackAddress(addr tcpip.Address) bool { } return addr[0] == 0x7f } + +// ========================= Options ========================== + +// An IPv4OptionType can hold the valuse for the Type in an IPv4 option. +type IPv4OptionType byte + +// These constants are needed to identify individual options in the option list. +// While RFC 791 (page 31) says "Every internet module must be able to act on +// every option." This has not generally been adhered to and some options have +// very low rates of support. We do not support options other than those shown +// below. + +const ( + // IPv4OptionListEndType is the option type for the End Of Option List + // option. Anything following is ignored. + IPv4OptionListEndType IPv4OptionType = 0 + + // IPv4OptionNOPType is the No-Operation option. May appear between other + // options and may appear multiple times. + IPv4OptionNOPType IPv4OptionType = 1 + + // IPv4OptionRecordRouteType is used by each router on the path of the packet + // to record its path. It is carried over to an Echo Reply. + IPv4OptionRecordRouteType IPv4OptionType = 7 + + // IPv4OptionTimestampType is the option type for the Timestamp option. + IPv4OptionTimestampType IPv4OptionType = 68 + + // ipv4OptionTypeOffset is the offset in an option of its type field. + ipv4OptionTypeOffset = 0 + + // IPv4OptionLengthOffset is the offset in an option of its length field. + IPv4OptionLengthOffset = 1 +) + +// Potential errors when parsing generic IP options. +var ( + ErrIPv4OptZeroLength = errors.New("zero length IP option") + ErrIPv4OptDuplicate = errors.New("duplicate IP option") + ErrIPv4OptInvalid = errors.New("invalid IP option") + ErrIPv4OptMalformed = errors.New("malformed IP option") + ErrIPv4OptionTruncated = errors.New("truncated IP option") + ErrIPv4OptionAddress = errors.New("bad IP option address") +) + +// IPv4Option is an interface representing various option types. +type IPv4Option interface { + // Type returns the type identifier of the option. + Type() IPv4OptionType + + // Size returns the size of the option in bytes. + Size() uint8 + + // Contents returns a slice holding the contents of the option. + Contents() []byte +} + +var _ IPv4Option = (*IPv4OptionGeneric)(nil) + +// IPv4OptionGeneric is an IPv4 Option of unknown type. +type IPv4OptionGeneric []byte + +// Type implements IPv4Option. +func (o *IPv4OptionGeneric) Type() IPv4OptionType { + return IPv4OptionType((*o)[ipv4OptionTypeOffset]) +} + +// Size implements IPv4Option. +func (o *IPv4OptionGeneric) Size() uint8 { return uint8(len(*o)) } + +// Contents implements IPv4Option. +func (o *IPv4OptionGeneric) Contents() []byte { return []byte(*o) } + +// IPv4OptionIterator is an iterator pointing to a specific IP option +// at any point of time. It also holds information as to a new options buffer +// that we are building up to hand back to the caller. +type IPv4OptionIterator struct { + options IPv4Options + // ErrCursor is where we are while parsing options. It is exported as any + // resulting ICMP packet is supposed to have a pointer to the byte within + // the IP packet where the error was detected. + ErrCursor uint8 + nextErrCursor uint8 + newOptions [IPv4MaximumOptionsSize]byte + writePoint int +} + +// MakeIterator sets up and returns an iterator of options. It also sets up the +// building of a new option set. +func (o IPv4Options) MakeIterator() IPv4OptionIterator { + return IPv4OptionIterator{ + options: o, + nextErrCursor: IPv4MinimumSize, + } +} + +// RemainingBuffer returns the remaining (unused) part of the new option buffer, +// into which a new option may be written. +func (i *IPv4OptionIterator) RemainingBuffer() IPv4Options { + return IPv4Options(i.newOptions[i.writePoint:]) +} + +// ConsumeBuffer marks a portion of the new buffer as used. +func (i *IPv4OptionIterator) ConsumeBuffer(size int) { + i.writePoint += size +} + +// PushNOPOrEnd puts one of the single byte options onto the new options. +// Only values 0 or 1 (ListEnd or NOP) are valid input. +func (i *IPv4OptionIterator) PushNOPOrEnd(val IPv4OptionType) { + if val > IPv4OptionNOPType { + panic(fmt.Sprintf("invalid option type %d pushed onto option build buffer", val)) + } + i.newOptions[i.writePoint] = byte(val) + i.writePoint++ +} + +// Finalize returns the completed replacement options buffer padded +// as needed. +func (i *IPv4OptionIterator) Finalize() IPv4Options { + // RFC 791 page 31 says: + // The options might not end on a 32-bit boundary. The internet header + // must be filled out with octets of zeros. The first of these would + // be interpreted as the end-of-options option, and the remainder as + // internet header padding. + // Since the buffer is already zero filled we just need to step the write + // pointer up to the next multiple of 4. + options := IPv4Options(i.newOptions[:(i.writePoint+0x3) & ^0x3]) + // Poison the write pointer. + i.writePoint = len(i.newOptions) + return options +} + +// Next returns the next IP option in the buffer/list of IP options. +// It returns +// - A slice of bytes holding the next option or nil if there is error. +// - A boolean which is true if parsing of all the options is complete. +// - An error which is non-nil if an error condition was encountered. +func (i *IPv4OptionIterator) Next() (IPv4Option, bool, error) { + // The opts slice gets shorter as we process the options. When we have no + // bytes left we are done. + if len(i.options) == 0 { + return nil, true, nil + } + + i.ErrCursor = i.nextErrCursor + + optType := IPv4OptionType(i.options[ipv4OptionTypeOffset]) + + if optType == IPv4OptionNOPType || optType == IPv4OptionListEndType { + optionBody := i.options[:1] + i.options = i.options[1:] + i.nextErrCursor = i.ErrCursor + 1 + retval := IPv4OptionGeneric(optionBody) + return &retval, false, nil + } + + // There are no more single byte options defined. All the rest have a length + // field so we need to sanity check it. + if len(i.options) == 1 { + return nil, true, ErrIPv4OptMalformed + } + + optLen := i.options[IPv4OptionLengthOffset] + + if optLen == 0 { + i.ErrCursor++ + return nil, true, ErrIPv4OptZeroLength + } + + if optLen == 1 { + i.ErrCursor++ + return nil, true, ErrIPv4OptMalformed + } + + if optLen > uint8(len(i.options)) { + i.ErrCursor++ + return nil, true, ErrIPv4OptionTruncated + } + + optionBody := i.options[:optLen] + i.nextErrCursor = i.ErrCursor + optLen + i.options = i.options[optLen:] + + // Check the length of some option types that we know. + switch optType { + case IPv4OptionTimestampType: + if optLen < IPv4OptionTimestampHdrLength { + i.ErrCursor++ + return nil, true, ErrIPv4OptMalformed + } + retval := IPv4OptionTimestamp(optionBody) + return &retval, false, nil + + case IPv4OptionRecordRouteType: + if optLen < IPv4OptionRecordRouteHdrLength { + i.ErrCursor++ + return nil, true, ErrIPv4OptMalformed + } + retval := IPv4OptionRecordRoute(optionBody) + return &retval, false, nil + } + retval := IPv4OptionGeneric(optionBody) + return &retval, false, nil +} + +// +// IP Timestamp option - RFC 791 page 22. +// +--------+--------+--------+--------+ +// |01000100| length | pointer|oflw|flg| +// +--------+--------+--------+--------+ +// | internet address | +// +--------+--------+--------+--------+ +// | timestamp | +// +--------+--------+--------+--------+ +// | ... | +// +// Type = 68 +// +// The Option Length is the number of octets in the option counting +// the type, length, pointer, and overflow/flag octets (maximum +// length 40). +// +// The Pointer is the number of octets from the beginning of this +// option to the end of timestamps plus one (i.e., it points to the +// octet beginning the space for next timestamp). The smallest +// legal value is 5. The timestamp area is full when the pointer +// is greater than the length. +// +// The Overflow (oflw) [4 bits] is the number of IP modules that +// cannot register timestamps due to lack of space. +// +// The Flag (flg) [4 bits] values are +// +// 0 -- time stamps only, stored in consecutive 32-bit words, +// +// 1 -- each timestamp is preceded with internet address of the +// registering entity, +// +// 3 -- the internet address fields are prespecified. An IP +// module only registers its timestamp if it matches its own +// address with the next specified internet address. +// +// Timestamps are defined in RFC 791 page 22 as milliseconds since midnight UTC. +// +// The Timestamp is a right-justified, 32-bit timestamp in +// milliseconds since midnight UT. If the time is not available in +// milliseconds or cannot be provided with respect to midnight UT +// then any time may be inserted as a timestamp provided the high +// order bit of the timestamp field is set to one to indicate the +// use of a non-standard value. + +// IPv4OptTSFlags sefines the values expected in the Timestamp +// option Flags field. +type IPv4OptTSFlags uint8 + +// +// Timestamp option specific related constants. +const ( + // IPv4OptionTimestampHdrLength is the length of the timestamp option header. + IPv4OptionTimestampHdrLength = 4 + + // IPv4OptionTimestampSize is the size of an IP timestamp. + IPv4OptionTimestampSize = 4 + + // IPv4OptionTimestampWithAddrSize is the size of an IP timestamp + Address. + IPv4OptionTimestampWithAddrSize = IPv4AddressSize + IPv4OptionTimestampSize + + // IPv4OptionTimestampMaxSize is limited by space for options + IPv4OptionTimestampMaxSize = IPv4MaximumOptionsSize + + // IPv4OptionTimestampOnlyFlag is a flag indicating that only timestamp + // is present. + IPv4OptionTimestampOnlyFlag IPv4OptTSFlags = 0 + + // IPv4OptionTimestampWithIPFlag is a flag indicating that both timestamps and + // IP are present. + IPv4OptionTimestampWithIPFlag IPv4OptTSFlags = 1 + + // IPv4OptionTimestampWithPredefinedIPFlag is a flag indicating that + // predefined IP is present. + IPv4OptionTimestampWithPredefinedIPFlag IPv4OptTSFlags = 3 +) + +// ipv4TimestampTime provides the current time as specified in RFC 791. +func ipv4TimestampTime(clock tcpip.Clock) uint32 { + const millisecondsPerDay = 24 * 3600 * 1000 + const nanoPerMilli = 1000000 + return uint32((clock.NowNanoseconds() / nanoPerMilli) % millisecondsPerDay) +} + +// IP Timestamp option fields. +const ( + // IPv4OptTSPointerOffset is the offset of the Timestamp pointer field. + IPv4OptTSPointerOffset = 2 + + // IPv4OptTSPointerOffset is the offset of the combined Flag and Overflow + // fields, (each being 4 bits). + IPv4OptTSOFLWAndFLGOffset = 3 + // These constants define the sub byte fields of the Flag and OverFlow field. + ipv4OptionTimestampOverflowshift = 4 + ipv4OptionTimestampFlagsMask byte = 0x0f +) + +var _ IPv4Option = (*IPv4OptionTimestamp)(nil) + +// IPv4OptionTimestamp is a Timestamp option from RFC 791. +type IPv4OptionTimestamp []byte + +// Type implements IPv4Option.Type(). +func (ts *IPv4OptionTimestamp) Type() IPv4OptionType { return IPv4OptionTimestampType } + +// Size implements IPv4Option. +func (ts *IPv4OptionTimestamp) Size() uint8 { return uint8(len(*ts)) } + +// Contents implements IPv4Option. +func (ts *IPv4OptionTimestamp) Contents() []byte { return []byte(*ts) } + +// Pointer returns the pointer field in the IP Timestamp option. +func (ts *IPv4OptionTimestamp) Pointer() uint8 { + return (*ts)[IPv4OptTSPointerOffset] +} + +// Flags returns the flags field in the IP Timestamp option. +func (ts *IPv4OptionTimestamp) Flags() IPv4OptTSFlags { + return IPv4OptTSFlags((*ts)[IPv4OptTSOFLWAndFLGOffset] & ipv4OptionTimestampFlagsMask) +} + +// Overflow returns the Overflow field in the IP Timestamp option. +func (ts *IPv4OptionTimestamp) Overflow() uint8 { + return (*ts)[IPv4OptTSOFLWAndFLGOffset] >> ipv4OptionTimestampOverflowshift +} + +// IncOverflow increments the Overflow field in the IP Timestamp option. It +// returns the incremented value. If the return value is 0 then the field +// overflowed. +func (ts *IPv4OptionTimestamp) IncOverflow() uint8 { + (*ts)[IPv4OptTSOFLWAndFLGOffset] += 1 << ipv4OptionTimestampOverflowshift + return ts.Overflow() +} + +// UpdateTimestamp updates the fields of the next free timestamp slot. +func (ts *IPv4OptionTimestamp) UpdateTimestamp(addr tcpip.Address, clock tcpip.Clock) { + slot := (*ts)[ts.Pointer()-1:] + + switch ts.Flags() { + case IPv4OptionTimestampOnlyFlag: + binary.BigEndian.PutUint32(slot, ipv4TimestampTime(clock)) + (*ts)[IPv4OptTSPointerOffset] += IPv4OptionTimestampSize + case IPv4OptionTimestampWithIPFlag: + if n := copy(slot, addr); n != IPv4AddressSize { + panic(fmt.Sprintf("copied %d bytes, expected %d bytes", n, IPv4AddressSize)) + } + binary.BigEndian.PutUint32(slot[IPv4AddressSize:], ipv4TimestampTime(clock)) + (*ts)[IPv4OptTSPointerOffset] += IPv4OptionTimestampWithAddrSize + case IPv4OptionTimestampWithPredefinedIPFlag: + if tcpip.Address(slot[:IPv4AddressSize]) == addr { + binary.BigEndian.PutUint32(slot[IPv4AddressSize:], ipv4TimestampTime(clock)) + (*ts)[IPv4OptTSPointerOffset] += IPv4OptionTimestampWithAddrSize + } + } +} + +// RecordRoute option specific related constants. +// +// from RFC 791 page 20: +// Record Route +// +// +--------+--------+--------+---------//--------+ +// |00000111| length | pointer| route data | +// +--------+--------+--------+---------//--------+ +// Type=7 +// +// The record route option provides a means to record the route of +// an internet datagram. +// +// The option begins with the option type code. The second octet +// is the option length which includes the option type code and the +// length octet, the pointer octet, and length-3 octets of route +// data. The third octet is the pointer into the route data +// indicating the octet which begins the next area to store a route +// address. The pointer is relative to this option, and the +// smallest legal value for the pointer is 4. +const ( + // IPv4OptionRecordRouteHdrLength is the length of the Record Route option + // header. + IPv4OptionRecordRouteHdrLength = 3 + + // IPv4OptRRPointerOffset is the offset to the pointer field in an RR + // option, which points to the next free slot in the list of addresses. + IPv4OptRRPointerOffset = 2 +) + +var _ IPv4Option = (*IPv4OptionRecordRoute)(nil) + +// IPv4OptionRecordRoute is an IPv4 RecordRoute option defined by RFC 791. +type IPv4OptionRecordRoute []byte + +// Pointer returns the pointer field in the IP RecordRoute option. +func (rr *IPv4OptionRecordRoute) Pointer() uint8 { + return (*rr)[IPv4OptRRPointerOffset] +} + +// StoreAddress stores the given IPv4 address into the next free slot. +func (rr *IPv4OptionRecordRoute) StoreAddress(addr tcpip.Address) { + start := rr.Pointer() - 1 // A one based number. + // start and room checked by caller. + if n := copy((*rr)[start:], addr); n != IPv4AddressSize { + panic(fmt.Sprintf("copied %d bytes, expected %d bytes", n, IPv4AddressSize)) + } + (*rr)[IPv4OptRRPointerOffset] += IPv4AddressSize +} + +// Type implements IPv4Option. +func (rr *IPv4OptionRecordRoute) Type() IPv4OptionType { return IPv4OptionRecordRouteType } + +// Size implements IPv4Option. +func (rr *IPv4OptionRecordRoute) Size() uint8 { return uint8(len(*rr)) } + +// Contents implements IPv4Option. +func (rr *IPv4OptionRecordRoute) Contents() []byte { return []byte(*rr) } |