182 lines
5.9 KiB
Go
182 lines
5.9 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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// IGMP represents an IGMP header stored in a byte array.
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type IGMP []byte
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// IGMP implements `Transport`.
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var _ Transport = (*IGMP)(nil)
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const (
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// IGMPMinimumSize is the minimum size of a valid IGMP packet in bytes,
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// as per RFC 2236, Section 2, Page 2.
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IGMPMinimumSize = 8
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// IGMPQueryMinimumSize is the minimum size of a valid Membership Query
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// Message in bytes, as per RFC 2236, Section 2, Page 2.
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IGMPQueryMinimumSize = 8
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// IGMPReportMinimumSize is the minimum size of a valid Report Message in
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// bytes, as per RFC 2236, Section 2, Page 2.
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IGMPReportMinimumSize = 8
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// IGMPLeaveMessageMinimumSize is the minimum size of a valid Leave Message
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// in bytes, as per RFC 2236, Section 2, Page 2.
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IGMPLeaveMessageMinimumSize = 8
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// IGMPTTL is the TTL for all IGMP messages, as per RFC 2236, Section 3, Page
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// 3.
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IGMPTTL = 1
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// igmpTypeOffset defines the offset of the type field in an IGMP message.
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igmpTypeOffset = 0
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// igmpMaxRespTimeOffset defines the offset of the MaxRespTime field in an
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// IGMP message.
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igmpMaxRespTimeOffset = 1
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// igmpChecksumOffset defines the offset of the checksum field in an IGMP
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// message.
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igmpChecksumOffset = 2
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// igmpGroupAddressOffset defines the offset of the Group Address field in an
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// IGMP message.
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igmpGroupAddressOffset = 4
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// IGMPProtocolNumber is IGMP's transport protocol number.
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IGMPProtocolNumber tcpip.TransportProtocolNumber = 2
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)
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// IGMPType is the IGMP type field as per RFC 2236.
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type IGMPType byte
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// Values for the IGMP Type described in RFC 2236 Section 2.1, Page 2.
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// Descriptions below come from there.
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const (
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// IGMPMembershipQuery indicates that the message type is Membership Query.
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// "There are two sub-types of Membership Query messages:
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// - General Query, used to learn which groups have members on an
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// attached network.
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// - Group-Specific Query, used to learn if a particular group
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// has any members on an attached network.
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// These two messages are differentiated by the Group Address, as
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// described in section 1.4 ."
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IGMPMembershipQuery IGMPType = 0x11
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// IGMPv1MembershipReport indicates that the message is a Membership Report
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// generated by a host using the IGMPv1 protocol: "an additional type of
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// message, for backwards-compatibility with IGMPv1"
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IGMPv1MembershipReport IGMPType = 0x12
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// IGMPv2MembershipReport indicates that the Message type is a Membership
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// Report generated by a host using the IGMPv2 protocol.
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IGMPv2MembershipReport IGMPType = 0x16
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// IGMPLeaveGroup indicates that the message type is a Leave Group
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// notification message.
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IGMPLeaveGroup IGMPType = 0x17
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)
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// Type is the IGMP type field.
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func (b IGMP) Type() IGMPType { return IGMPType(b[igmpTypeOffset]) }
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// SetType sets the IGMP type field.
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func (b IGMP) SetType(t IGMPType) { b[igmpTypeOffset] = byte(t) }
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// MaxRespTime gets the MaxRespTimeField. This is meaningful only in Membership
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// Query messages, in other cases it is set to 0 by the sender and ignored by
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// the receiver.
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func (b IGMP) MaxRespTime() time.Duration {
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// As per RFC 2236 section 2.2,
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//
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// The Max Response Time field is meaningful only in Membership Query
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// messages, and specifies the maximum allowed time before sending a
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// responding report in units of 1/10 second. In all other messages, it
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// is set to zero by the sender and ignored by receivers.
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return DecisecondToDuration(b[igmpMaxRespTimeOffset])
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}
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// SetMaxRespTime sets the MaxRespTimeField.
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func (b IGMP) SetMaxRespTime(m byte) { b[igmpMaxRespTimeOffset] = m }
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// Checksum is the IGMP checksum field.
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func (b IGMP) Checksum() uint16 {
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return binary.BigEndian.Uint16(b[igmpChecksumOffset:])
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}
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// SetChecksum sets the IGMP checksum field.
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func (b IGMP) SetChecksum(checksum uint16) {
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binary.BigEndian.PutUint16(b[igmpChecksumOffset:], checksum)
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}
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// GroupAddress gets the Group Address field.
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func (b IGMP) GroupAddress() tcpip.Address {
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return tcpip.Address(b[igmpGroupAddressOffset:][:IPv4AddressSize])
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}
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// SetGroupAddress sets the Group Address field.
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func (b IGMP) SetGroupAddress(address tcpip.Address) {
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if n := copy(b[igmpGroupAddressOffset:], address); n != IPv4AddressSize {
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panic(fmt.Sprintf("copied %d bytes, expected %d", n, IPv4AddressSize))
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}
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}
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// SourcePort implements Transport.SourcePort.
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func (IGMP) SourcePort() uint16 {
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return 0
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}
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// DestinationPort implements Transport.DestinationPort.
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func (IGMP) DestinationPort() uint16 {
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return 0
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}
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// SetSourcePort implements Transport.SetSourcePort.
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func (IGMP) SetSourcePort(uint16) {
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}
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// SetDestinationPort implements Transport.SetDestinationPort.
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func (IGMP) SetDestinationPort(uint16) {
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}
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// Payload implements Transport.Payload.
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func (IGMP) Payload() []byte {
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return nil
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}
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// IGMPCalculateChecksum calculates the IGMP checksum over the provided IGMP
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// header.
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func IGMPCalculateChecksum(h IGMP) uint16 {
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// The header contains a checksum itself, set it aside to avoid checksumming
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// the checksum and replace it afterwards.
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existingXsum := h.Checksum()
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h.SetChecksum(0)
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xsum := ^Checksum(h, 0)
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h.SetChecksum(existingXsum)
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return xsum
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}
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// DecisecondToDuration converts a value representing deci-seconds to a
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// time.Duration.
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func DecisecondToDuration(ds uint8) time.Duration {
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return time.Duration(ds) * time.Second / 10
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}
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