| // 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 "github.com/google/netstack/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 = 2 + 2 + 1 + 1 + 2 + 2*6 + 2*4 |
| ) |
| |
| // 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 |
| |
| func (a ARP) hardwareAddressSpace() uint16 { return uint16(a[0])<<8 | uint16(a[1]) } |
| func (a ARP) protocolAddressSpace() uint16 { return uint16(a[2])<<8 | uint16(a[3]) } |
| func (a ARP) hardwareAddressSize() int { return int(a[4]) } |
| func (a ARP) protocolAddressSize() int { return int(a[5]) } |
| |
| // Op is the ARP opcode. |
| func (a ARP) Op() ARPOp { return ARPOp(a[6])<<8 | ARPOp(a[7]) } |
| |
| // SetOp sets the ARP opcode. |
| func (a ARP) SetOp(op ARPOp) { |
| a[6] = uint8(op >> 8) |
| a[7] = uint8(op) |
| } |
| |
| // SetIPv4OverEthernet configures the ARP packet for IPv4-over-Ethernet. |
| func (a ARP) SetIPv4OverEthernet() { |
| a[0], a[1] = 0, 1 // htypeEthernet |
| a[2], a[3] = 0x08, 0x00 // IPv4ProtocolNumber |
| a[4] = 6 // macSize |
| a[5] = 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 { |
| const s = 8 |
| return a[s : s+6] |
| } |
| |
| // 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 { |
| const s = 8 + 6 |
| return a[s : s+4] |
| } |
| |
| // 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 { |
| const s = 8 + 6 + 4 |
| return a[s : s+6] |
| } |
| |
| // 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 { |
| const s = 8 + 6 + 4 + 6 |
| return a[s : s+4] |
| } |
| |
| // IsValid reports whether this is an ARP packet for IPv4 over Ethernet. |
| func (a ARP) IsValid() bool { |
| if len(a) < ARPSize { |
| return false |
| } |
| const htypeEthernet = 1 |
| const macSize = 6 |
| return a.hardwareAddressSpace() == htypeEthernet && |
| a.protocolAddressSpace() == uint16(IPv4ProtocolNumber) && |
| a.hardwareAddressSize() == macSize && |
| a.protocolAddressSize() == IPv4AddressSize |
| } |