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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"
"fmt"
"time"
"gvisor.dev/gvisor/pkg/tcpip"
)
func mldv2AndIGMPv3QuerierQueryCodeToInterval(code uint8) time.Duration {
// MLDv2: As per RFC 3810 section 5.1.19,
//
// The Querier's Query Interval Code field specifies the [Query
// Interval] used by the Querier. The actual interval, called the
// Querier's Query Interval (QQI), is represented in units of seconds,
// and is derived from the Querier's Query Interval Code as follows:
//
// If QQIC < 128, QQI = QQIC
//
// If QQIC >= 128, QQIC represents a floating-point value as follows:
//
// 0 1 2 3 4 5 6 7
// +-+-+-+-+-+-+-+-+
// |1| exp | mant |
// +-+-+-+-+-+-+-+-+
//
// QQI = (mant | 0x10) << (exp + 3)
//
// Multicast routers that are not the current Querier adopt the QQI
// value from the most recently received Query as their own [Query
// Interval] value, unless that most recently received QQI was zero, in
// which case the receiving routers use the default [Query Interval]
// value specified in section 9.2.
//
// IGMPv3: As per RFC 3376 section 4.1.7,
//
// The Querier's Query Interval Code field specifies the [Query
// Interval] used by the querier. The actual interval, called the
// Querier's Query Interval (QQI), is represented in units of seconds
// and is derived from the Querier's Query Interval Code as follows:
//
// If QQIC < 128, QQI = QQIC
//
// If QQIC >= 128, QQIC represents a floating-point value as follows:
//
// 0 1 2 3 4 5 6 7
// +-+-+-+-+-+-+-+-+
// |1| exp | mant |
// +-+-+-+-+-+-+-+-+
//
// QQI = (mant | 0x10) << (exp + 3)
//
// Multicast routers that are not the current querier adopt the QQI
// value from the most recently received Query as their own [Query
// Interval] value, unless that most recently received QQI was zero, in
// which case the receiving routers use the default [Query Interval]
// value specified in section 8.2.
interval := time.Duration(code)
if interval < 128 {
return interval * time.Second
}
const expMask = 0b111
const mantBits = 4
mant := interval & ((1 << mantBits) - 1)
exp := (interval >> mantBits) & expMask
return (mant | 0x10) << (exp + 3) * time.Second
}
// MakeAddressIterator returns an AddressIterator.
func MakeAddressIterator(addressSize int, buf *bytes.Buffer) AddressIterator {
return AddressIterator{addressSize: addressSize, buf: buf}
}
// AddressIterator is an iterator over IPv6 addresses.
type AddressIterator struct {
addressSize int
buf *bytes.Buffer
}
// Done indicates that the iterator has been exhausted/has no more elements.
func (it *AddressIterator) Done() bool {
return it.buf.Len() == 0
}
// Next returns the next address in the iterator.
//
// Returns false if the iterator has been exhausted.
func (it *AddressIterator) Next() (tcpip.Address, bool) {
if it.Done() {
var emptyAddress tcpip.Address
return emptyAddress, false
}
b := it.buf.Next(it.addressSize)
if len(b) != it.addressSize {
panic(fmt.Sprintf("got len(buf.Next(%d)) = %d, want = %d", it.addressSize, len(b), it.addressSize))
}
return tcpip.AddrFromSlice(b), true
}
func makeAddressIterator(b []byte, expectedAddresses uint16, addressSize int) (AddressIterator, bool) {
expectedLen := int(expectedAddresses) * addressSize
if len(b) < expectedLen {
return AddressIterator{}, false
}
return MakeAddressIterator(addressSize, bytes.NewBuffer(b[:expectedLen])), true
}
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