| // Copyright 2018 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" |
| |
| "gvisor.dev/gvisor/pkg/tcpip" |
| ) |
| |
| const ( |
| // ARPProtocolNumber is the ARP network protocol number. |
| ARPProtocolNumber tcpip.NetworkProtocolNumber = 0x0806 |
| |
| // ARPSize is the size of an IPv4-over-Ethernet ARP packet. |
| ARPSize = 28 |
| ) |
| |
| // ARPHardwareType is the hardware type for LinkEndpoint in an ARP header. |
| type ARPHardwareType uint16 |
| |
| // Typical ARP HardwareType values. Some of the constants have to be specific |
| // values as they are egressed on the wire in the HTYPE field of an ARP header. |
| const ( |
| ARPHardwareNone ARPHardwareType = 0 |
| // ARPHardwareEther specifically is the HTYPE for Ethernet as specified |
| // in the IANA list here: |
| // |
| // https://www.iana.org/assignments/arp-parameters/arp-parameters.xhtml#arp-parameters-2 |
| ARPHardwareEther ARPHardwareType = 1 |
| ARPHardwareLoopback ARPHardwareType = 2 |
| ) |
| |
| // ARPOp is an ARP opcode. |
| type ARPOp uint16 |
| |
| // Typical ARP opcodes defined in RFC 826. |
| const ( |
| ARPRequest ARPOp = 1 |
| ARPReply ARPOp = 2 |
| ) |
| |
| // ARP is an ARP packet stored in a byte array as described in RFC 826. |
| type ARP []byte |
| |
| const ( |
| hTypeOffset = 0 |
| protocolOffset = 2 |
| haAddressSizeOffset = 4 |
| protoAddressSizeOffset = 5 |
| opCodeOffset = 6 |
| senderHAAddressOffset = 8 |
| senderProtocolAddressOffset = senderHAAddressOffset + EthernetAddressSize |
| targetHAAddressOffset = senderProtocolAddressOffset + IPv4AddressSize |
| targetProtocolAddressOffset = targetHAAddressOffset + EthernetAddressSize |
| ) |
| |
| func (a ARP) hardwareAddressType() ARPHardwareType { |
| return ARPHardwareType(binary.BigEndian.Uint16(a[hTypeOffset:])) |
| } |
| |
| func (a ARP) protocolAddressSpace() uint16 { return binary.BigEndian.Uint16(a[protocolOffset:]) } |
| func (a ARP) hardwareAddressSize() int { return int(a[haAddressSizeOffset]) } |
| func (a ARP) protocolAddressSize() int { return int(a[protoAddressSizeOffset]) } |
| |
| // Op is the ARP opcode. |
| func (a ARP) Op() ARPOp { return ARPOp(binary.BigEndian.Uint16(a[opCodeOffset:])) } |
| |
| // SetOp sets the ARP opcode. |
| func (a ARP) SetOp(op ARPOp) { |
| binary.BigEndian.PutUint16(a[opCodeOffset:], uint16(op)) |
| } |
| |
| // SetIPv4OverEthernet configures the ARP packet for IPv4-over-Ethernet. |
| func (a ARP) SetIPv4OverEthernet() { |
| binary.BigEndian.PutUint16(a[hTypeOffset:], uint16(ARPHardwareEther)) |
| binary.BigEndian.PutUint16(a[protocolOffset:], uint16(IPv4ProtocolNumber)) |
| a[haAddressSizeOffset] = EthernetAddressSize |
| a[protoAddressSizeOffset] = uint8(IPv4AddressSize) |
| } |
| |
| // HardwareAddressSender is the link address of the sender. |
| // It is a view on to the ARP packet so it can be used to set the value. |
| func (a ARP) HardwareAddressSender() []byte { |
| return a[senderHAAddressOffset : senderHAAddressOffset+EthernetAddressSize] |
| } |
| |
| // ProtocolAddressSender is the protocol address of the sender. |
| // It is a view on to the ARP packet so it can be used to set the value. |
| func (a ARP) ProtocolAddressSender() []byte { |
| return a[senderProtocolAddressOffset : senderProtocolAddressOffset+IPv4AddressSize] |
| } |
| |
| // HardwareAddressTarget is the link address of the target. |
| // It is a view on to the ARP packet so it can be used to set the value. |
| func (a ARP) HardwareAddressTarget() []byte { |
| return a[targetHAAddressOffset : targetHAAddressOffset+EthernetAddressSize] |
| } |
| |
| // ProtocolAddressTarget is the protocol address of the target. |
| // It is a view on to the ARP packet so it can be used to set the value. |
| func (a ARP) ProtocolAddressTarget() []byte { |
| return a[targetProtocolAddressOffset : targetProtocolAddressOffset+IPv4AddressSize] |
| } |
| |
| // IsValid reports whether this is an ARP packet for IPv4 over Ethernet. |
| func (a ARP) IsValid() bool { |
| if len(a) < ARPSize { |
| return false |
| } |
| return a.hardwareAddressType() == ARPHardwareEther && |
| a.protocolAddressSpace() == uint16(IPv4ProtocolNumber) && |
| a.hardwareAddressSize() == EthernetAddressSize && |
| a.protocolAddressSize() == IPv4AddressSize |
| } |