diff options
| -rw-r--r-- | pkg/tcpip/header/mld.go | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/pkg/tcpip/header/mld.go b/pkg/tcpip/header/mld.go new file mode 100644 index 000000000..f70623092 --- /dev/null +++ b/pkg/tcpip/header/mld.go @@ -0,0 +1,96 @@ +// 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" +) + +const ( + // mldMaximumResponseDelayOffset is the offset to the Maximum Response Delay + // field within MLD. + mldMaximumResponseDelayOffset = 0 + + // mldMulticastAddressOffset is the offset to the Multicast Address field + // within MLD. + mldMulticastAddressOffset = 4 +) + +// MLD is a Multicast Listener Discovery message in an ICMPv6 packet. +// +// MLD will only contain the body of an ICMPv6 packet. +// +// As per RFC 2710 section 3, MLD messages have the following format (MLD only +// holds the bytes after the first four bytes in the diagram below): +// +// 0 1 2 3 +// 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 +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// | Type | Code | Checksum | +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// | Maximum Response Delay | Reserved | +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// | | +// + + +// | | +// + Multicast Address + +// | | +// + + +// | | +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +type MLD []byte + +// MaximumResponseDelay returns the Maximum Response Delay. +func (m MLD) MaximumResponseDelay() time.Duration { + // As per RFC 2710 section 3.4: + // + // The Maximum Response Delay field is meaningful only in Query + // messages, and specifies the maximum allowed delay before sending a + // responding Report, in units of milliseconds. In all other messages, + // it is set to zero by the sender and ignored by receivers. + return time.Duration(binary.BigEndian.Uint16(m[mldMaximumResponseDelayOffset:])) * time.Millisecond +} + +// SetMaximumResponseDelay sets the Maximum Response Delay field. +// +// maxRespDelayMS is the value in milliseconds. +func (m MLD) SetMaximumResponseDelay(maxRespDelayMS uint16) { + binary.BigEndian.PutUint16(m[mldMaximumResponseDelayOffset:], maxRespDelayMS) +} + +// MulticastAddress returns the Multicast Address. +func (m MLD) MulticastAddress() tcpip.Address { + // As per RFC 2710 section 3.5: + // + // In a Query message, the Multicast Address field is set to zero when + // sending a General Query, and set to a specific IPv6 multicast address + // when sending a Multicast-Address-Specific Query. + // + // In a Report or Done message, the Multicast Address field holds a + // specific IPv6 multicast address to which the message sender is + // listening or is ceasing to listen, respectively. + return tcpip.Address(m[mldMulticastAddressOffset:][:IPv6AddressSize]) +} + +// SetMulticastAddress sets the Multicast Address field. +func (m MLD) SetMulticastAddress(multicastAddress tcpip.Address) { + if n := copy(m[mldMulticastAddressOffset:], multicastAddress); n != IPv6AddressSize { + panic(fmt.Sprintf("copied %d bytes, expected to copy %d bytes", n, IPv6AddressSize)) + } +} |