gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/pkg/tcpip/header/mldv2_igmpv3_common.go (about)

     1  // Copyright 2022 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package header
    16  
    17  import (
    18  	"bytes"
    19  	"fmt"
    20  	"time"
    21  
    22  	"gvisor.dev/gvisor/pkg/tcpip"
    23  )
    24  
    25  func mldv2AndIGMPv3QuerierQueryCodeToInterval(code uint8) time.Duration {
    26  	// MLDv2: As per RFC 3810 section 5.1.19,
    27  	//
    28  	//   The Querier's Query Interval Code field specifies the [Query
    29  	//   Interval] used by the Querier.  The actual interval, called the
    30  	//   Querier's Query Interval (QQI), is represented in units of seconds,
    31  	//   and is derived from the Querier's Query Interval Code as follows:
    32  	//
    33  	//   If QQIC < 128, QQI = QQIC
    34  	//
    35  	//   If QQIC >= 128, QQIC represents a floating-point value as follows:
    36  	//
    37  	//       0 1 2 3 4 5 6 7
    38  	//      +-+-+-+-+-+-+-+-+
    39  	//      |1| exp | mant  |
    40  	//      +-+-+-+-+-+-+-+-+
    41  	//
    42  	//   QQI = (mant | 0x10) << (exp + 3)
    43  	//
    44  	//   Multicast routers that are not the current Querier adopt the QQI
    45  	//   value from the most recently received Query as their own [Query
    46  	//   Interval] value, unless that most recently received QQI was zero, in
    47  	//   which case the receiving routers use the default [Query Interval]
    48  	//   value specified in section 9.2.
    49  	//
    50  	// IGMPv3: As per RFC 3376 section 4.1.7,
    51  	//
    52  	//   The Querier's Query Interval Code field specifies the [Query
    53  	//   Interval] used by the querier.  The actual interval, called the
    54  	//   Querier's Query Interval (QQI), is represented in units of seconds
    55  	//   and is derived from the Querier's Query Interval Code as follows:
    56  	//
    57  	//   If QQIC < 128, QQI = QQIC
    58  	//
    59  	//   If QQIC >= 128, QQIC represents a floating-point value as follows:
    60  	//
    61  	//       0 1 2 3 4 5 6 7
    62  	//      +-+-+-+-+-+-+-+-+
    63  	//      |1| exp | mant  |
    64  	//      +-+-+-+-+-+-+-+-+
    65  	//
    66  	//   QQI = (mant | 0x10) << (exp + 3)
    67  	//
    68  	//   Multicast routers that are not the current querier adopt the QQI
    69  	//   value from the most recently received Query as their own [Query
    70  	//   Interval] value, unless that most recently received QQI was zero, in
    71  	//   which case the receiving routers use the default [Query Interval]
    72  	//   value specified in section 8.2.
    73  	interval := time.Duration(code)
    74  	if interval < 128 {
    75  		return interval * time.Second
    76  	}
    77  
    78  	const expMask = 0b111
    79  	const mantBits = 4
    80  	mant := interval & ((1 << mantBits) - 1)
    81  	exp := (interval >> mantBits) & expMask
    82  	return (mant | 0x10) << (exp + 3) * time.Second
    83  }
    84  
    85  // MakeAddressIterator returns an AddressIterator.
    86  func MakeAddressIterator(addressSize int, buf *bytes.Buffer) AddressIterator {
    87  	return AddressIterator{addressSize: addressSize, buf: buf}
    88  }
    89  
    90  // AddressIterator is an iterator over IPv6 addresses.
    91  type AddressIterator struct {
    92  	addressSize int
    93  	buf         *bytes.Buffer
    94  }
    95  
    96  // Done indicates that the iterator has been exhausted/has no more elements.
    97  func (it *AddressIterator) Done() bool {
    98  	return it.buf.Len() == 0
    99  }
   100  
   101  // Next returns the next address in the iterator.
   102  //
   103  // Returns false if the iterator has been exhausted.
   104  func (it *AddressIterator) Next() (tcpip.Address, bool) {
   105  	if it.Done() {
   106  		var emptyAddress tcpip.Address
   107  		return emptyAddress, false
   108  	}
   109  
   110  	b := it.buf.Next(it.addressSize)
   111  	if len(b) != it.addressSize {
   112  		panic(fmt.Sprintf("got len(buf.Next(%d)) = %d, want = %d", it.addressSize, len(b), it.addressSize))
   113  	}
   114  
   115  	return tcpip.AddrFromSlice(b), true
   116  }
   117  
   118  func makeAddressIterator(b []byte, expectedAddresses uint16, addressSize int) (AddressIterator, bool) {
   119  	expectedLen := int(expectedAddresses) * addressSize
   120  	if len(b) < expectedLen {
   121  		return AddressIterator{}, false
   122  	}
   123  	return MakeAddressIterator(addressSize, bytes.NewBuffer(b[:expectedLen])), true
   124  }