104 lines
4.1 KiB
Go
104 lines
4.1 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package header
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import (
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"encoding/binary"
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"fmt"
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"time"
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"gvisor.dev/gvisor/pkg/tcpip"
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)
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const (
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// MLDMinimumSize is the minimum size for an MLD message.
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MLDMinimumSize = 20
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// MLDHopLimit is the Hop Limit for all IPv6 packets with an MLD message, as
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// per RFC 2710 section 3.
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MLDHopLimit = 1
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// mldMaximumResponseDelayOffset is the offset to the Maximum Response Delay
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// field within MLD.
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mldMaximumResponseDelayOffset = 0
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// mldMulticastAddressOffset is the offset to the Multicast Address field
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// within MLD.
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mldMulticastAddressOffset = 4
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)
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// MLD is a Multicast Listener Discovery message in an ICMPv6 packet.
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//
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// MLD will only contain the body of an ICMPv6 packet.
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//
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// As per RFC 2710 section 3, MLD messages have the following format (MLD only
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// holds the bytes after the first four bytes in the diagram below):
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//
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// 0 1 2 3
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// 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
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Type | Code | Checksum |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Maximum Response Delay | Reserved |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | |
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// + +
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// | |
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// + Multicast Address +
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// | |
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// + +
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// | |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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type MLD []byte
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// MaximumResponseDelay returns the Maximum Response Delay.
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func (m MLD) MaximumResponseDelay() time.Duration {
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// As per RFC 2710 section 3.4:
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//
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// The Maximum Response Delay field is meaningful only in Query
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// messages, and specifies the maximum allowed delay before sending a
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// responding Report, in units of milliseconds. In all other messages,
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// it is set to zero by the sender and ignored by receivers.
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return time.Duration(binary.BigEndian.Uint16(m[mldMaximumResponseDelayOffset:])) * time.Millisecond
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}
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// SetMaximumResponseDelay sets the Maximum Response Delay field.
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//
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// maxRespDelayMS is the value in milliseconds.
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func (m MLD) SetMaximumResponseDelay(maxRespDelayMS uint16) {
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binary.BigEndian.PutUint16(m[mldMaximumResponseDelayOffset:], maxRespDelayMS)
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}
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// MulticastAddress returns the Multicast Address.
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func (m MLD) MulticastAddress() tcpip.Address {
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// As per RFC 2710 section 3.5:
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//
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// In a Query message, the Multicast Address field is set to zero when
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// sending a General Query, and set to a specific IPv6 multicast address
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// when sending a Multicast-Address-Specific Query.
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//
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// In a Report or Done message, the Multicast Address field holds a
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// specific IPv6 multicast address to which the message sender is
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// listening or is ceasing to listen, respectively.
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return tcpip.Address(m[mldMulticastAddressOffset:][:IPv6AddressSize])
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}
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// SetMulticastAddress sets the Multicast Address field.
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func (m MLD) SetMulticastAddress(multicastAddress tcpip.Address) {
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if n := copy(m[mldMulticastAddressOffset:], multicastAddress); n != IPv6AddressSize {
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panic(fmt.Sprintf("copied %d bytes, expected to copy %d bytes", n, IPv6AddressSize))
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}
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}
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