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// Copyright 2020 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 (
"encoding/binary"
"fmt"
"time"
"gvisor.dev/gvisor/pkg/tcpip"
)
// IGMP represents an IGMP header stored in a byte array.
type IGMP []byte
// IGMP implements `Transport`.
var _ Transport = (*IGMP)(nil)
const (
// IGMPMinimumSize is the minimum size of a valid IGMP packet in bytes,
// as per RFC 2236, Section 2, Page 2.
IGMPMinimumSize = 8
// IGMPQueryMinimumSize is the minimum size of a valid Membership Query
// Message in bytes, as per RFC 2236, Section 2, Page 2.
IGMPQueryMinimumSize = 8
// IGMPReportMinimumSize is the minimum size of a valid Report Message in
// bytes, as per RFC 2236, Section 2, Page 2.
IGMPReportMinimumSize = 8
// IGMPLeaveMessageMinimumSize is the minimum size of a valid Leave Message
// in bytes, as per RFC 2236, Section 2, Page 2.
IGMPLeaveMessageMinimumSize = 8
// IGMPTTL is the TTL for all IGMP messages, as per RFC 2236, Section 3, Page
// 3.
IGMPTTL = 1
// igmpTypeOffset defines the offset of the type field in an IGMP message.
igmpTypeOffset = 0
// igmpMaxRespTimeOffset defines the offset of the MaxRespTime field in an
// IGMP message.
igmpMaxRespTimeOffset = 1
// igmpChecksumOffset defines the offset of the checksum field in an IGMP
// message.
igmpChecksumOffset = 2
// igmpGroupAddressOffset defines the offset of the Group Address field in an
// IGMP message.
igmpGroupAddressOffset = 4
// IGMPProtocolNumber is IGMP's transport protocol number.
IGMPProtocolNumber tcpip.TransportProtocolNumber = 2
)
// IGMPType is the IGMP type field as per RFC 2236.
type IGMPType byte
// Values for the IGMP Type described in RFC 2236 Section 2.1, Page 2.
// Descriptions below come from there.
const (
// IGMPMembershipQuery indicates that the message type is Membership Query.
// "There are two sub-types of Membership Query messages:
// - General Query, used to learn which groups have members on an
// attached network.
// - Group-Specific Query, used to learn if a particular group
// has any members on an attached network.
// These two messages are differentiated by the Group Address, as
// described in section 1.4 ."
IGMPMembershipQuery IGMPType = 0x11
// IGMPv1MembershipReport indicates that the message is a Membership Report
// generated by a host using the IGMPv1 protocol: "an additional type of
// message, for backwards-compatibility with IGMPv1"
IGMPv1MembershipReport IGMPType = 0x12
// IGMPv2MembershipReport indicates that the Message type is a Membership
// Report generated by a host using the IGMPv2 protocol.
IGMPv2MembershipReport IGMPType = 0x16
// IGMPLeaveGroup indicates that the message type is a Leave Group
// notification message.
IGMPLeaveGroup IGMPType = 0x17
)
// Type is the IGMP type field.
func (b IGMP) Type() IGMPType { return IGMPType(b[igmpTypeOffset]) }
// SetType sets the IGMP type field.
func (b IGMP) SetType(t IGMPType) { b[igmpTypeOffset] = byte(t) }
// MaxRespTime gets the MaxRespTimeField. This is meaningful only in Membership
// Query messages, in other cases it is set to 0 by the sender and ignored by
// the receiver.
func (b IGMP) MaxRespTime() time.Duration {
// As per RFC 2236 section 2.2,
//
// The Max Response Time field is meaningful only in Membership Query
// messages, and specifies the maximum allowed time before sending a
// responding report in units of 1/10 second. In all other messages, it
// is set to zero by the sender and ignored by receivers.
return DecisecondToDuration(b[igmpMaxRespTimeOffset])
}
// SetMaxRespTime sets the MaxRespTimeField.
func (b IGMP) SetMaxRespTime(m byte) { b[igmpMaxRespTimeOffset] = m }
// Checksum is the IGMP checksum field.
func (b IGMP) Checksum() uint16 {
return binary.BigEndian.Uint16(b[igmpChecksumOffset:])
}
// SetChecksum sets the IGMP checksum field.
func (b IGMP) SetChecksum(checksum uint16) {
binary.BigEndian.PutUint16(b[igmpChecksumOffset:], checksum)
}
// GroupAddress gets the Group Address field.
func (b IGMP) GroupAddress() tcpip.Address {
return tcpip.Address(b[igmpGroupAddressOffset:][:IPv4AddressSize])
}
// SetGroupAddress sets the Group Address field.
func (b IGMP) SetGroupAddress(address tcpip.Address) {
if n := copy(b[igmpGroupAddressOffset:], address); n != IPv4AddressSize {
panic(fmt.Sprintf("copied %d bytes, expected %d", n, IPv4AddressSize))
}
}
// SourcePort implements Transport.SourcePort.
func (IGMP) SourcePort() uint16 {
return 0
}
// DestinationPort implements Transport.DestinationPort.
func (IGMP) DestinationPort() uint16 {
return 0
}
// SetSourcePort implements Transport.SetSourcePort.
func (IGMP) SetSourcePort(uint16) {
}
// SetDestinationPort implements Transport.SetDestinationPort.
func (IGMP) SetDestinationPort(uint16) {
}
// Payload implements Transport.Payload.
func (IGMP) Payload() []byte {
return nil
}
// IGMPCalculateChecksum calculates the IGMP checksum over the provided IGMP
// header.
func IGMPCalculateChecksum(h IGMP) uint16 {
// The header contains a checksum itself, set it aside to avoid checksumming
// the checksum and replace it afterwards.
existingXsum := h.Checksum()
h.SetChecksum(0)
xsum := ^Checksum(h, 0)
h.SetChecksum(existingXsum)
return xsum
}
// DecisecondToDuration converts a value representing deci-seconds to a
// time.Duration.
func DecisecondToDuration(ds uint8) time.Duration {
return time.Duration(ds) * time.Second / 10
}
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