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// Copyright 2022 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 (
"bytes"
"encoding/binary"
"fmt"
"time"
"gvisor.dev/gvisor/pkg/tcpip"
)
const (
// MLDv2QueryMinimumSize is the minimum size for an MLDv2 message.
MLDv2QueryMinimumSize = 24
mldv2QueryMaximumResponseCodeOffset = 0
mldv2QueryResvSQRVOffset = 20
mldv2QueryQRVMask = 0b111
mldv2QueryQQICOffset = 21
// mldv2QueryNumberOfSourcesOffset is the offset to the Number of Sources
// field within MLDv2Query.
mldv2QueryNumberOfSourcesOffset = 22
// MLDv2ReportMinimumSize is the minimum size of an MLDv2 report.
MLDv2ReportMinimumSize = 24
// mldv2QuerySourcesOffset is the offset to the Sources field within
// MLDv2Query.
mldv2QuerySourcesOffset = 24
)
var (
// MLDv2RoutersAddress is the address to send MLDv2 reports to.
//
// As per RFC 3810 section 5.2.14,
//
// Version 2 Multicast Listener Reports are sent with an IP destination
// address of FF02:0:0:0:0:0:0:16, to which all MLDv2-capable multicast
// routers listen (see section 11 for IANA considerations related to
// this special destination address).
MLDv2RoutersAddress = tcpip.AddrFrom16([16]byte{0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x16})
)
// MLDv2Query is a Multicast Listener Discovery Version 2 Query message in an
// ICMPv6 packet.
//
// MLDv2Query will only contain the body of an ICMPv6 packet.
//
// As per RFC 3810 section 5.1, MLDv2 Query messages have the following format
// (MLDv2Query only holds the bytes after the first four bytes in the diagram
// below):
//
// 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 = 130 | Code | Checksum |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Maximum Response Code | Reserved |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// * *
// | |
// * Multicast Address *
// | |
// * *
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Resv |S| QRV | QQIC | Number of Sources (N) |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// * *
// | |
// * Source Address [1] *
// | |
// * *
// | |
// +- -+
// | |
// * *
// | |
// * Source Address [2] *
// | |
// * *
// | |
// +- . -+
// . . .
// . . .
// +- -+
// | |
// * *
// | |
// * Source Address [N] *
// | |
// * *
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type MLDv2Query MLD
// MaximumResponseCode returns the Maximum Response Code
func (m MLDv2Query) MaximumResponseCode() uint16 {
return binary.BigEndian.Uint16(m[mldv2QueryMaximumResponseCodeOffset:])
}
// MLDv2MaximumResponseDelay returns the Maximum Response Delay in an MLDv2
// Maximum Response Code.
//
// As per RFC 3810 section 5.1.3,
//
// The Maximum Response Code field specifies the maximum time allowed
// before sending a responding Report. The actual time allowed, called
// the Maximum Response Delay, is represented in units of milliseconds,
// and is derived from the Maximum Response Code as follows:
//
// If Maximum Response Code < 32768,
// Maximum Response Delay = Maximum Response Code
//
// If Maximum Response Code >=32768, Maximum Response Code represents a
// floating-point value as follows:
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |1| exp | mant |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//
// Maximum Response Delay = (mant | 0x1000) << (exp+3)
//
// Small values of Maximum Response Delay allow MLDv2 routers to tune
// the "leave latency" (the time between the moment the last node on a
// link ceases to listen to a specific multicast address and the moment
// the routing protocol is notified that there are no more listeners for
// that address). Larger values, especially in the exponential range,
// allow the tuning of the burstiness of MLD traffic on a link.
func MLDv2MaximumResponseDelay(codeRaw uint16) time.Duration {
code := time.Duration(codeRaw)
if code < 32768 {
return code * time.Millisecond
}
const mantBits = 12
const expMask = 0b111
exp := (code >> mantBits) & expMask
mant := code & ((1 << mantBits) - 1)
return (mant | 0x1000) << (exp + 3) * time.Millisecond
}
// MulticastAddress returns the Multicast Address.
func (m MLDv2Query) MulticastAddress() tcpip.Address {
// As per RFC 2710 section 3.5:
//
// In a Query message, the Multicast Address field is set to zero when
// sending a General Query, and set to a specific IPv6 multicast address
// when sending a Multicast-Address-Specific Query.
//
// In a Report or Done message, the Multicast Address field holds a
// specific IPv6 multicast address to which the message sender is
// listening or is ceasing to listen, respectively.
return tcpip.AddrFrom16([16]byte(m[mldMulticastAddressOffset:][:IPv6AddressSize]))
}
// QuerierRobustnessVariable returns the querier's robustness variable.
func (m MLDv2Query) QuerierRobustnessVariable() uint8 {
return m[mldv2QueryResvSQRVOffset] & mldv2QueryQRVMask
}
// QuerierQueryInterval returns the querier's query interval.
func (m MLDv2Query) QuerierQueryInterval() time.Duration {
return mldv2AndIGMPv3QuerierQueryCodeToInterval(m[mldv2QueryQQICOffset])
}
// Sources returns an iterator over source addresses in the query.
//
// Returns false if the message cannot hold the expected number of sources.
func (m MLDv2Query) Sources() (AddressIterator, bool) {
return makeAddressIterator(
m[mldv2QuerySourcesOffset:],
binary.BigEndian.Uint16(m[mldv2QueryNumberOfSourcesOffset:]),
IPv6AddressSize,
)
}
// MLDv2ReportRecordType is the type of an MLDv2 multicast address record
// found in an MLDv2 report, as per RFC 3810 section 5.2.12.
type MLDv2ReportRecordType int
// MLDv2 multicast address record types, as per RFC 3810 section 5.2.12.
const (
MLDv2ReportRecordModeIsInclude MLDv2ReportRecordType = 1
MLDv2ReportRecordModeIsExclude MLDv2ReportRecordType = 2
MLDv2ReportRecordChangeToIncludeMode MLDv2ReportRecordType = 3
MLDv2ReportRecordChangeToExcludeMode MLDv2ReportRecordType = 4
MLDv2ReportRecordAllowNewSources MLDv2ReportRecordType = 5
MLDv2ReportRecordBlockOldSources MLDv2ReportRecordType = 6
)
const (
mldv2ReportMulticastAddressRecordMinimumSize = 20
mldv2ReportMulticastAddressRecordTypeOffset = 0
mldv2ReportMulticastAddressRecordAuxDataLenOffset = 1
mldv2ReportMulticastAddressRecordAuxDataLenUnits = 4
mldv2ReportMulticastAddressRecordNumberOfSourcesOffset = 2
mldv2ReportMulticastAddressRecordMulticastAddressOffset = 4
mldv2ReportMulticastAddressRecordSourcesOffset = 20
)
// MLDv2ReportMulticastAddressRecordSerializer is an MLDv2 Multicast Address
// Record serializer.
//
// As per RFC 3810 section 5.2, a Multicast Address Record has the following
// internal format:
//
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Record Type | Aux Data Len | Number of Sources (N) |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// * *
// | |
// * Multicast Address *
// | |
// * *
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// * *
// | |
// * Source Address [1] *
// | |
// * *
// | |
// +- -+
// | |
// * *
// | |
// * Source Address [2] *
// | |
// * *
// | |
// +- -+
// . . .
// . . .
// . . .
// +- -+
// | |
// * *
// | |
// * Source Address [N] *
// | |
// * *
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Auxiliary Data .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type MLDv2ReportMulticastAddressRecordSerializer struct {
RecordType MLDv2ReportRecordType
MulticastAddress tcpip.Address
Sources []tcpip.Address
}
// Length returns the number of bytes this serializer would occupy.
func (s *MLDv2ReportMulticastAddressRecordSerializer) Length() int {
return mldv2ReportMulticastAddressRecordSourcesOffset + len(s.Sources)*IPv6AddressSize
}
func copyIPv6Address(dst []byte, src tcpip.Address) {
if n := copy(dst, src.AsSlice()); n != IPv6AddressSize {
panic(fmt.Sprintf("got copy(...) = %d, want = %d", n, IPv6AddressSize))
}
}
// SerializeInto serializes the record into the buffer.
//
// Panics if the buffer does not have enough space to fit the record.
func (s *MLDv2ReportMulticastAddressRecordSerializer) SerializeInto(b []byte) {
b[mldv2ReportMulticastAddressRecordTypeOffset] = byte(s.RecordType)
b[mldv2ReportMulticastAddressRecordAuxDataLenOffset] = 0
binary.BigEndian.PutUint16(b[mldv2ReportMulticastAddressRecordNumberOfSourcesOffset:], uint16(len(s.Sources)))
copyIPv6Address(b[mldv2ReportMulticastAddressRecordMulticastAddressOffset:], s.MulticastAddress)
b = b[mldv2ReportMulticastAddressRecordSourcesOffset:]
for _, source := range s.Sources {
copyIPv6Address(b, source)
b = b[IPv6AddressSize:]
}
}
const (
mldv2ReportReservedOffset = 0
mldv2ReportNumberOfMulticastAddressRecordsOffset = 2
mldv2ReportMulticastAddressRecordsOffset = 4
)
// MLDv2ReportSerializer is an MLD Version 2 Report serializer.
//
// As per RFC 3810 section 5.2,
//
// 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 = 143 | Reserved | Checksum |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Reserved |Nr of Mcast Address Records (M)|
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Multicast Address Record [1] .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Multicast Address Record [2] .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | . |
// . . .
// | . |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Multicast Address Record [M] .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type MLDv2ReportSerializer struct {
Records []MLDv2ReportMulticastAddressRecordSerializer
}
// Length returns the number of bytes this serializer would occupy.
func (s *MLDv2ReportSerializer) Length() int {
ret := mldv2ReportMulticastAddressRecordsOffset
for _, record := range s.Records {
ret += record.Length()
}
return ret
}
// SerializeInto serializes the report into the buffer.
//
// Panics if the buffer does not have enough space to fit the report.
func (s *MLDv2ReportSerializer) SerializeInto(b []byte) {
binary.BigEndian.PutUint16(b[mldv2ReportReservedOffset:], 0)
binary.BigEndian.PutUint16(b[mldv2ReportNumberOfMulticastAddressRecordsOffset:], uint16(len(s.Records)))
b = b[mldv2ReportMulticastAddressRecordsOffset:]
for _, record := range s.Records {
len := record.Length()
record.SerializeInto(b[:len])
b = b[len:]
}
}
// MLDv2ReportMulticastAddressRecord is an MLDv2 record.
//
// As per RFC 3810 section 5.2, a Multicast Address Record has the following
// internal format:
//
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Record Type | Aux Data Len | Number of Sources (N) |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// * *
// | |
// * Multicast Address *
// | |
// * *
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// * *
// | |
// * Source Address [1] *
// | |
// * *
// | |
// +- -+
// | |
// * *
// | |
// * Source Address [2] *
// | |
// * *
// | |
// +- -+
// . . .
// . . .
// . . .
// +- -+
// | |
// * *
// | |
// * Source Address [N] *
// | |
// * *
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Auxiliary Data .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type MLDv2ReportMulticastAddressRecord []byte
// RecordType returns the type of this record.
func (r MLDv2ReportMulticastAddressRecord) RecordType() MLDv2ReportRecordType {
return MLDv2ReportRecordType(r[mldv2ReportMulticastAddressRecordTypeOffset])
}
// AuxDataLen returns the length of the auxiliary data in this record.
func (r MLDv2ReportMulticastAddressRecord) AuxDataLen() int {
return int(r[mldv2ReportMulticastAddressRecordAuxDataLenOffset]) * mldv2ReportMulticastAddressRecordAuxDataLenUnits
}
// numberOfSources returns the number of sources in this record.
func (r MLDv2ReportMulticastAddressRecord) numberOfSources() uint16 {
return binary.BigEndian.Uint16(r[mldv2ReportMulticastAddressRecordNumberOfSourcesOffset:])
}
// MulticastAddress returns the multicast address this record targets.
func (r MLDv2ReportMulticastAddressRecord) MulticastAddress() tcpip.Address {
return tcpip.AddrFrom16([16]byte(r[mldv2ReportMulticastAddressRecordMulticastAddressOffset:][:IPv6AddressSize]))
}
// Sources returns an iterator over source addresses in the query.
//
// Returns false if the message cannot hold the expected number of sources.
func (r MLDv2ReportMulticastAddressRecord) Sources() (AddressIterator, bool) {
expectedLen := int(r.numberOfSources()) * IPv6AddressSize
b := r[mldv2ReportMulticastAddressRecordSourcesOffset:]
if len(b) < expectedLen {
return AddressIterator{}, false
}
return AddressIterator{addressSize: IPv6AddressSize, buf: bytes.NewBuffer(b[:expectedLen])}, true
}
// MLDv2Report is an MLDv2 Report.
//
// As per RFC 3810 section 5.2,
//
// 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 = 143 | Reserved | Checksum |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Reserved |Nr of Mcast Address Records (M)|
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Multicast Address Record [1] .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Multicast Address Record [2] .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | . |
// . . .
// | . |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// . .
// . Multicast Address Record [M] .
// . .
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type MLDv2Report []byte
// MLDv2ReportMulticastAddressRecordIterator is an iterator over MLDv2 Multicast
// Address Records.
type MLDv2ReportMulticastAddressRecordIterator struct {
recordsLeft uint16
buf *bytes.Buffer
}
// MLDv2ReportMulticastAddressRecordIteratorNextDisposition is the possible
// return values from MLDv2ReportMulticastAddressRecordIterator.Next.
type MLDv2ReportMulticastAddressRecordIteratorNextDisposition int
const (
// MLDv2ReportMulticastAddressRecordIteratorNextOk indicates that a multicast
// address record was yielded.
MLDv2ReportMulticastAddressRecordIteratorNextOk MLDv2ReportMulticastAddressRecordIteratorNextDisposition = iota
// MLDv2ReportMulticastAddressRecordIteratorNextDone indicates that the iterator
// has been exhausted.
MLDv2ReportMulticastAddressRecordIteratorNextDone
// MLDv2ReportMulticastAddressRecordIteratorNextErrBufferTooShort indicates
// that the iterator expected another record, but the buffer ended
// prematurely.
MLDv2ReportMulticastAddressRecordIteratorNextErrBufferTooShort
)
// Next returns the next MLDv2 Multicast Address Record.
func (it *MLDv2ReportMulticastAddressRecordIterator) Next() (MLDv2ReportMulticastAddressRecord, MLDv2ReportMulticastAddressRecordIteratorNextDisposition) {
if it.recordsLeft == 0 {
return MLDv2ReportMulticastAddressRecord{}, MLDv2ReportMulticastAddressRecordIteratorNextDone
}
if it.buf.Len() < mldv2ReportMulticastAddressRecordMinimumSize {
return MLDv2ReportMulticastAddressRecord{}, MLDv2ReportMulticastAddressRecordIteratorNextErrBufferTooShort
}
hdr := MLDv2ReportMulticastAddressRecord(it.buf.Bytes())
expectedLen := mldv2ReportMulticastAddressRecordMinimumSize +
int(hdr.AuxDataLen()) + int(hdr.numberOfSources())*IPv6AddressSize
bytes := it.buf.Next(expectedLen)
if len(bytes) < expectedLen {
return MLDv2ReportMulticastAddressRecord{}, MLDv2ReportMulticastAddressRecordIteratorNextErrBufferTooShort
}
it.recordsLeft--
return MLDv2ReportMulticastAddressRecord(bytes), MLDv2ReportMulticastAddressRecordIteratorNextOk
}
// MulticastAddressRecords returns an iterator of MLDv2 Multicast Address
// Records.
func (m MLDv2Report) MulticastAddressRecords() MLDv2ReportMulticastAddressRecordIterator {
return MLDv2ReportMulticastAddressRecordIterator{
recordsLeft: binary.BigEndian.Uint16(m[mldv2ReportNumberOfMulticastAddressRecordsOffset:]),
buf: bytes.NewBuffer(m[mldv2ReportMulticastAddressRecordsOffset:]),
}
}
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