diff options
Diffstat (limited to 'pkg/tcpip/header')
| -rw-r--r-- | pkg/tcpip/header/ipv6.go | 15 | ||||
| -rw-r--r-- | pkg/tcpip/header/ipv6_extension_headers.go | 326 | ||||
| -rw-r--r-- | pkg/tcpip/header/ipv6_fragment.go | 42 |
3 files changed, 355 insertions, 28 deletions
diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go index 55d09355a..d522e5f10 100644 --- a/pkg/tcpip/header/ipv6.go +++ b/pkg/tcpip/header/ipv6.go @@ -48,11 +48,13 @@ type IPv6Fields struct { // FlowLabel is the "flow label" field of an IPv6 packet. FlowLabel uint32 - // PayloadLength is the "payload length" field of an IPv6 packet. + // PayloadLength is the "payload length" field of an IPv6 packet, including + // the length of all extension headers. PayloadLength uint16 - // NextHeader is the "next header" field of an IPv6 packet. - NextHeader uint8 + // TransportProtocol is the transport layer protocol number. Serialized in the + // last "next header" field of the IPv6 header + extension headers. + TransportProtocol tcpip.TransportProtocolNumber // HopLimit is the "Hop Limit" field of an IPv6 packet. HopLimit uint8 @@ -62,6 +64,9 @@ type IPv6Fields struct { // DstAddr is the "destination ip address" of an IPv6 packet. DstAddr tcpip.Address + + // ExtensionHeaders are the extension headers following the IPv6 header. + ExtensionHeaders IPv6ExtHdrSerializer } // IPv6 represents an ipv6 header stored in a byte array. @@ -253,12 +258,14 @@ func (IPv6) SetChecksum(uint16) { // Encode encodes all the fields of the ipv6 header. func (b IPv6) Encode(i *IPv6Fields) { + extHdr := b[IPv6MinimumSize:] b.SetTOS(i.TrafficClass, i.FlowLabel) b.SetPayloadLength(i.PayloadLength) - b[IPv6NextHeaderOffset] = i.NextHeader b[hopLimit] = i.HopLimit b.SetSourceAddress(i.SrcAddr) b.SetDestinationAddress(i.DstAddr) + nextHeader, _ := i.ExtensionHeaders.Serialize(i.TransportProtocol, extHdr) + b[IPv6NextHeaderOffset] = nextHeader } // IsValid performs basic validation on the packet. diff --git a/pkg/tcpip/header/ipv6_extension_headers.go b/pkg/tcpip/header/ipv6_extension_headers.go index 571eae233..1fbb2cc98 100644 --- a/pkg/tcpip/header/ipv6_extension_headers.go +++ b/pkg/tcpip/header/ipv6_extension_headers.go @@ -20,7 +20,9 @@ import ( "encoding/binary" "fmt" "io" + "math" + "gvisor.dev/gvisor/pkg/tcpip" "gvisor.dev/gvisor/pkg/tcpip/buffer" ) @@ -75,8 +77,8 @@ const ( // Fragment Offset field within an IPv6FragmentExtHdr. ipv6FragmentExtHdrFragmentOffsetOffset = 0 - // ipv6FragmentExtHdrFragmentOffsetShift is the least significant bits to - // discard from the Fragment Offset. + // ipv6FragmentExtHdrFragmentOffsetShift is the bit offset of the Fragment + // Offset field within an IPv6FragmentExtHdr. ipv6FragmentExtHdrFragmentOffsetShift = 3 // ipv6FragmentExtHdrFlagsIdx is the index to the flags field within an @@ -114,6 +116,37 @@ const ( IPv6FragmentExtHdrFragmentOffsetBytesPerUnit = 8 ) +// padIPv6OptionsLength returns the total length for IPv6 options of length l +// considering the 8-octet alignment as stated in RFC 8200 Section 4.2. +func padIPv6OptionsLength(length int) int { + return (length + ipv6ExtHdrLenBytesPerUnit - 1) & ^(ipv6ExtHdrLenBytesPerUnit - 1) +} + +// padIPv6Option fills b with the appropriate padding options depending on its +// length. +func padIPv6Option(b []byte) { + switch len(b) { + case 0: // No padding needed. + case 1: // Pad with Pad1. + b[ipv6ExtHdrOptionTypeOffset] = uint8(ipv6Pad1ExtHdrOptionIdentifier) + default: // Pad with PadN. + s := b[ipv6ExtHdrOptionPayloadOffset:] + for i := range s { + s[i] = 0 + } + b[ipv6ExtHdrOptionTypeOffset] = uint8(ipv6PadNExtHdrOptionIdentifier) + b[ipv6ExtHdrOptionLengthOffset] = uint8(len(s)) + } +} + +// ipv6OptionsAlignmentPadding returns the number of padding bytes needed to +// serialize an option at headerOffset with alignment requirements +// [align]n + alignOffset. +func ipv6OptionsAlignmentPadding(headerOffset int, align int, alignOffset int) int { + padLen := headerOffset - alignOffset + return ((padLen + align - 1) & ^(align - 1)) - padLen +} + // IPv6PayloadHeader is implemented by the various headers that can be found // in an IPv6 payload. // @@ -206,29 +239,51 @@ type IPv6ExtHdrOption interface { isIPv6ExtHdrOption() } -// IPv6ExtHdrOptionIndentifier is an IPv6 extension header option identifier. -type IPv6ExtHdrOptionIndentifier uint8 +// IPv6ExtHdrOptionIdentifier is an IPv6 extension header option identifier. +type IPv6ExtHdrOptionIdentifier uint8 const ( // ipv6Pad1ExtHdrOptionIdentifier is the identifier for a padding option that // provides 1 byte padding, as outlined in RFC 8200 section 4.2. - ipv6Pad1ExtHdrOptionIdentifier IPv6ExtHdrOptionIndentifier = 0 + ipv6Pad1ExtHdrOptionIdentifier IPv6ExtHdrOptionIdentifier = 0 // ipv6PadBExtHdrOptionIdentifier is the identifier for a padding option that // provides variable length byte padding, as outlined in RFC 8200 section 4.2. - ipv6PadNExtHdrOptionIdentifier IPv6ExtHdrOptionIndentifier = 1 + ipv6PadNExtHdrOptionIdentifier IPv6ExtHdrOptionIdentifier = 1 + + // ipv6RouterAlertHopByHopOptionIdentifier is the identifier for the Router + // Alert Hop by Hop option as defined in RFC 2711 section 2.1. + ipv6RouterAlertHopByHopOptionIdentifier IPv6ExtHdrOptionIdentifier = 5 + + // ipv6ExtHdrOptionTypeOffset is the option type offset in an extension header + // option as defined in RFC 8200 section 4.2. + ipv6ExtHdrOptionTypeOffset = 0 + + // ipv6ExtHdrOptionLengthOffset is the option length offset in an extension + // header option as defined in RFC 8200 section 4.2. + ipv6ExtHdrOptionLengthOffset = 1 + + // ipv6ExtHdrOptionPayloadOffset is the option payload offset in an extension + // header option as defined in RFC 8200 section 4.2. + ipv6ExtHdrOptionPayloadOffset = 2 ) +// ipv6UnknownActionFromIdentifier maps an extension header option's +// identifier's high bits to the action to take when the identifier is unknown. +func ipv6UnknownActionFromIdentifier(id IPv6ExtHdrOptionIdentifier) IPv6OptionUnknownAction { + return IPv6OptionUnknownAction((id & ipv6UnknownExtHdrOptionActionMask) >> ipv6UnknownExtHdrOptionActionShift) +} + // IPv6UnknownExtHdrOption holds the identifier and data for an IPv6 extension // header option that is unknown by the parsing utilities. type IPv6UnknownExtHdrOption struct { - Identifier IPv6ExtHdrOptionIndentifier + Identifier IPv6ExtHdrOptionIdentifier Data []byte } // UnknownAction implements IPv6OptionUnknownAction.UnknownAction. func (o *IPv6UnknownExtHdrOption) UnknownAction() IPv6OptionUnknownAction { - return IPv6OptionUnknownAction((o.Identifier & ipv6UnknownExtHdrOptionActionMask) >> ipv6UnknownExtHdrOptionActionShift) + return ipv6UnknownActionFromIdentifier(o.Identifier) } // isIPv6ExtHdrOption implements IPv6ExtHdrOption.isIPv6ExtHdrOption. @@ -251,7 +306,7 @@ func (i *IPv6OptionsExtHdrOptionsIterator) Next() (IPv6ExtHdrOption, bool, error // options buffer has been exhausted and we are done iterating. return nil, true, nil } - id := IPv6ExtHdrOptionIndentifier(temp) + id := IPv6ExtHdrOptionIdentifier(temp) // If the option identifier indicates the option is a Pad1 option, then we // know the option does not have Length and Data fields. End processing of @@ -294,6 +349,14 @@ func (i *IPv6OptionsExtHdrOptionsIterator) Next() (IPv6ExtHdrOption, bool, error panic(fmt.Sprintf("error when skipping PadN (N = %d) option's data bytes: %s", length, err)) } continue + case ipv6RouterAlertHopByHopOptionIdentifier: + var routerAlertValue [ipv6RouterAlertPayloadLength]byte + if n, err := i.reader.Read(routerAlertValue[:]); err != nil { + panic(fmt.Sprintf("error when reading RouterAlert option's data bytes: %s", err)) + } else if n != ipv6RouterAlertPayloadLength { + return nil, true, fmt.Errorf("read %d bytes for RouterAlert option, expected %d", n, ipv6RouterAlertPayloadLength) + } + return &IPv6RouterAlertOption{Value: IPv6RouterAlertValue(binary.BigEndian.Uint16(routerAlertValue[:]))}, false, nil default: bytes := make([]byte, length) if n, err := io.ReadFull(&i.reader, bytes); err != nil { @@ -609,3 +672,248 @@ func (i *IPv6PayloadIterator) nextHeaderData(fragmentHdr bool, bytes []byte) (IP return IPv6ExtensionHeaderIdentifier(nextHdrIdentifier), bytes, nil } + +// IPv6SerializableExtHdr provides serialization for IPv6 extension +// headers. +type IPv6SerializableExtHdr interface { + // identifier returns the assigned IPv6 header identifier for this extension + // header. + identifier() IPv6ExtensionHeaderIdentifier + + // length returns the total serialized length in bytes of this extension + // header, including the common next header and length fields. + length() int + + // serializeInto serializes the receiver into the provided byte + // buffer and with the provided nextHeader value. + // + // Note, the caller MUST provide a byte buffer with size of at least + // length. Implementers of this function may assume that the byte buffer + // is of sufficient size. serializeInto MAY panic if the provided byte + // buffer is not of sufficient size. + // + // serializeInto returns the number of bytes that was used to serialize the + // receiver. Implementers must only use the number of bytes required to + // serialize the receiver. Callers MAY provide a larger buffer than required + // to serialize into. + serializeInto(nextHeader uint8, b []byte) int +} + +var _ IPv6SerializableExtHdr = (*IPv6SerializableHopByHopExtHdr)(nil) + +// IPv6SerializableHopByHopExtHdr implements serialization of the Hop by Hop +// options extension header. +type IPv6SerializableHopByHopExtHdr []IPv6SerializableHopByHopOption + +const ( + // ipv6HopByHopExtHdrNextHeaderOffset is the offset of the next header field + // in a hop by hop extension header as defined in RFC 8200 section 4.3. + ipv6HopByHopExtHdrNextHeaderOffset = 0 + + // ipv6HopByHopExtHdrLengthOffset is the offset of the length field in a hop + // by hop extension header as defined in RFC 8200 section 4.3. + ipv6HopByHopExtHdrLengthOffset = 1 + + // ipv6HopByHopExtHdrPayloadOffset is the offset of the options in a hop by + // hop extension header as defined in RFC 8200 section 4.3. + ipv6HopByHopExtHdrOptionsOffset = 2 + + // ipv6HopByHopExtHdrUnaccountedLenWords is the implicit number of 8-octet + // words in a hop by hop extension header's length field, as stated in RFC + // 8200 section 4.3: + // Length of the Hop-by-Hop Options header in 8-octet units, + // not including the first 8 octets. + ipv6HopByHopExtHdrUnaccountedLenWords = 1 +) + +// identifier implements IPv6SerializableExtHdr. +func (IPv6SerializableHopByHopExtHdr) identifier() IPv6ExtensionHeaderIdentifier { + return IPv6HopByHopOptionsExtHdrIdentifier +} + +// length implements IPv6SerializableExtHdr. +func (h IPv6SerializableHopByHopExtHdr) length() int { + var total int + for _, opt := range h { + align, alignOffset := opt.alignment() + total += ipv6OptionsAlignmentPadding(total, align, alignOffset) + total += ipv6ExtHdrOptionPayloadOffset + int(opt.length()) + } + // Account for next header and total length fields and add padding. + return padIPv6OptionsLength(ipv6HopByHopExtHdrOptionsOffset + total) +} + +// serializeInto implements IPv6SerializableExtHdr. +func (h IPv6SerializableHopByHopExtHdr) serializeInto(nextHeader uint8, b []byte) int { + optBuffer := b[ipv6HopByHopExtHdrOptionsOffset:] + totalLength := ipv6HopByHopExtHdrOptionsOffset + for _, opt := range h { + // Calculate alignment requirements and pad buffer if necessary. + align, alignOffset := opt.alignment() + padLen := ipv6OptionsAlignmentPadding(totalLength, align, alignOffset) + if padLen != 0 { + padIPv6Option(optBuffer[:padLen]) + totalLength += padLen + optBuffer = optBuffer[padLen:] + } + + l := opt.serializeInto(optBuffer[ipv6ExtHdrOptionPayloadOffset:]) + optBuffer[ipv6ExtHdrOptionTypeOffset] = uint8(opt.identifier()) + optBuffer[ipv6ExtHdrOptionLengthOffset] = l + l += ipv6ExtHdrOptionPayloadOffset + totalLength += int(l) + optBuffer = optBuffer[l:] + } + padded := padIPv6OptionsLength(totalLength) + if padded != totalLength { + padIPv6Option(optBuffer[:padded-totalLength]) + totalLength = padded + } + wordsLen := totalLength/ipv6ExtHdrLenBytesPerUnit - ipv6HopByHopExtHdrUnaccountedLenWords + if wordsLen > math.MaxUint8 { + panic(fmt.Sprintf("IPv6 hop by hop options too large: %d+1 64-bit words", wordsLen)) + } + b[ipv6HopByHopExtHdrNextHeaderOffset] = nextHeader + b[ipv6HopByHopExtHdrLengthOffset] = uint8(wordsLen) + return totalLength +} + +// IPv6SerializableHopByHopOption provides serialization for hop by hop options. +type IPv6SerializableHopByHopOption interface { + // identifier returns the option identifier of this Hop by Hop option. + identifier() IPv6ExtHdrOptionIdentifier + + // length returns the *payload* size of the option (not considering the type + // and length fields). + length() uint8 + + // alignment returns the alignment requirements from this option. + // + // Alignment requirements take the form [align]n + offset as specified in + // RFC 8200 section 4.2. The alignment requirement is on the offset between + // the option type byte and the start of the hop by hop header. + // + // align must be a power of 2. + alignment() (align int, offset int) + + // serializeInto serializes the receiver into the provided byte + // buffer. + // + // Note, the caller MUST provide a byte buffer with size of at least + // length. Implementers of this function may assume that the byte buffer + // is of sufficient size. serializeInto MAY panic if the provided byte + // buffer is not of sufficient size. + // + // serializeInto will return the number of bytes that was used to + // serialize the receiver. Implementers must only use the number of + // bytes required to serialize the receiver. Callers MAY provide a + // larger buffer than required to serialize into. + serializeInto([]byte) uint8 +} + +var _ IPv6SerializableHopByHopOption = (*IPv6RouterAlertOption)(nil) + +// IPv6RouterAlertOption is the IPv6 Router alert Hop by Hop option defined in +// RFC 2711 section 2.1. +type IPv6RouterAlertOption struct { + Value IPv6RouterAlertValue +} + +// IPv6RouterAlertValue is the payload of an IPv6 Router Alert option. +type IPv6RouterAlertValue uint16 + +const ( + // IPv6RouterAlertMLD indicates a datagram containing a Multicast Listener + // Discovery message as defined in RFC 2711 section 2.1. + IPv6RouterAlertMLD IPv6RouterAlertValue = 0 + // IPv6RouterAlertRSVP indicates a datagram containing an RSVP message as + // defined in RFC 2711 section 2.1. + IPv6RouterAlertRSVP IPv6RouterAlertValue = 1 + // IPv6RouterAlertActiveNetworks indicates a datagram containing an Active + // Networks message as defined in RFC 2711 section 2.1. + IPv6RouterAlertActiveNetworks IPv6RouterAlertValue = 2 + + // ipv6RouterAlertPayloadLength is the length of the Router Alert payload + // as defined in RFC 2711. + ipv6RouterAlertPayloadLength = 2 + + // ipv6RouterAlertAlignmentRequirement is the alignment requirement for the + // Router Alert option defined as 2n+0 in RFC 2711. + ipv6RouterAlertAlignmentRequirement = 2 + + // ipv6RouterAlertAlignmentOffsetRequirement is the alignment offset + // requirement for the Router Alert option defined as 2n+0 in RFC 2711 section + // 2.1. + ipv6RouterAlertAlignmentOffsetRequirement = 0 +) + +// UnknownAction implements IPv6ExtHdrOption. +func (*IPv6RouterAlertOption) UnknownAction() IPv6OptionUnknownAction { + return ipv6UnknownActionFromIdentifier(ipv6RouterAlertHopByHopOptionIdentifier) +} + +// isIPv6ExtHdrOption implements IPv6ExtHdrOption. +func (*IPv6RouterAlertOption) isIPv6ExtHdrOption() {} + +// identifier implements IPv6SerializableHopByHopOption. +func (*IPv6RouterAlertOption) identifier() IPv6ExtHdrOptionIdentifier { + return ipv6RouterAlertHopByHopOptionIdentifier +} + +// length implements IPv6SerializableHopByHopOption. +func (*IPv6RouterAlertOption) length() uint8 { + return ipv6RouterAlertPayloadLength +} + +// alignment implements IPv6SerializableHopByHopOption. +func (*IPv6RouterAlertOption) alignment() (int, int) { + // From RFC 2711 section 2.1: + // Alignment requirement: 2n+0. + return ipv6RouterAlertAlignmentRequirement, ipv6RouterAlertAlignmentOffsetRequirement +} + +// serializeInto implements IPv6SerializableHopByHopOption. +func (o *IPv6RouterAlertOption) serializeInto(b []byte) uint8 { + binary.BigEndian.PutUint16(b, uint16(o.Value)) + return ipv6RouterAlertPayloadLength +} + +// IPv6ExtHdrSerializer provides serialization of IPv6 extension headers. +type IPv6ExtHdrSerializer []IPv6SerializableExtHdr + +// Serialize serializes the provided list of IPv6 extension headers into b. +// +// Note, b must be of sufficient size to hold all the headers in s. See +// IPv6ExtHdrSerializer.Length for details on the getting the total size of a +// serialized IPv6ExtHdrSerializer. +// +// Serialize may panic if b is not of sufficient size to hold all the options +// in s. +// +// Serialize takes the transportProtocol value to be used as the last extension +// header's Next Header value and returns the header identifier of the first +// serialized extension header and the total serialized length. +func (s IPv6ExtHdrSerializer) Serialize(transportProtocol tcpip.TransportProtocolNumber, b []byte) (uint8, int) { + nextHeader := uint8(transportProtocol) + if len(s) == 0 { + return nextHeader, 0 + } + var totalLength int + for i, h := range s[:len(s)-1] { + length := h.serializeInto(uint8(s[i+1].identifier()), b) + b = b[length:] + totalLength += length + } + totalLength += s[len(s)-1].serializeInto(nextHeader, b) + return uint8(s[0].identifier()), totalLength +} + +// Length returns the total number of bytes required to serialize the extension +// headers. +func (s IPv6ExtHdrSerializer) Length() int { + var totalLength int + for _, h := range s { + totalLength += h.length() + } + return totalLength +} diff --git a/pkg/tcpip/header/ipv6_fragment.go b/pkg/tcpip/header/ipv6_fragment.go index 018555a26..9d09f32eb 100644 --- a/pkg/tcpip/header/ipv6_fragment.go +++ b/pkg/tcpip/header/ipv6_fragment.go @@ -27,12 +27,11 @@ const ( idV6 = 4 ) -// IPv6FragmentFields contains the fields of an IPv6 fragment. It is used to describe the -// fields of a packet that needs to be encoded. -type IPv6FragmentFields struct { - // NextHeader is the "next header" field of an IPv6 fragment. - NextHeader uint8 +var _ IPv6SerializableExtHdr = (*IPv6SerializableFragmentExtHdr)(nil) +// IPv6SerializableFragmentExtHdr is used to serialize an IPv6 fragment +// extension header as defined in RFC 8200 section 4.5. +type IPv6SerializableFragmentExtHdr struct { // FragmentOffset is the "fragment offset" field of an IPv6 fragment. FragmentOffset uint16 @@ -43,6 +42,29 @@ type IPv6FragmentFields struct { Identification uint32 } +// identifier implements IPv6SerializableFragmentExtHdr. +func (h *IPv6SerializableFragmentExtHdr) identifier() IPv6ExtensionHeaderIdentifier { + return IPv6FragmentHeader +} + +// length implements IPv6SerializableFragmentExtHdr. +func (h *IPv6SerializableFragmentExtHdr) length() int { + return IPv6FragmentHeaderSize +} + +// serializeInto implements IPv6SerializableFragmentExtHdr. +func (h *IPv6SerializableFragmentExtHdr) serializeInto(nextHeader uint8, b []byte) int { + // Prevent too many bounds checks. + _ = b[IPv6FragmentHeaderSize:] + binary.BigEndian.PutUint32(b[idV6:], h.Identification) + binary.BigEndian.PutUint16(b[fragOff:], h.FragmentOffset<<ipv6FragmentExtHdrFragmentOffsetShift) + b[nextHdrFrag] = nextHeader + if h.M { + b[more] |= ipv6FragmentExtHdrMFlagMask + } + return IPv6FragmentHeaderSize +} + // IPv6Fragment represents an ipv6 fragment header stored in a byte array. // Most of the methods of IPv6Fragment access to the underlying slice without // checking the boundaries and could panic because of 'index out of range'. @@ -58,16 +80,6 @@ const ( IPv6FragmentHeaderSize = 8 ) -// Encode encodes all the fields of the ipv6 fragment. -func (b IPv6Fragment) Encode(i *IPv6FragmentFields) { - b[nextHdrFrag] = i.NextHeader - binary.BigEndian.PutUint16(b[fragOff:], i.FragmentOffset<<3) - if i.M { - b[more] |= 1 - } - binary.BigEndian.PutUint32(b[idV6:], i.Identification) -} - // IsValid performs basic validation on the fragment header. func (b IPv6Fragment) IsValid() bool { return len(b) >= IPv6FragmentHeaderSize |