2019-04-29 21:25:05 +00:00
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// Copyright 2018 The gVisor Authors.
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2018-07-09 21:03:03 +00:00
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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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2018-04-27 17:37:02 +00:00
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package header
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2019-06-13 23:49:09 +00:00
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import "gvisor.dev/gvisor/pkg/tcpip"
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2018-04-27 17:37:02 +00:00
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const (
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// ARPProtocolNumber is the ARP network protocol number.
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ARPProtocolNumber tcpip.NetworkProtocolNumber = 0x0806
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// ARPSize is the size of an IPv4-over-Ethernet ARP packet.
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ARPSize = 2 + 2 + 1 + 1 + 2 + 2*6 + 2*4
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)
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// ARPOp is an ARP opcode.
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type ARPOp uint16
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// Typical ARP opcodes defined in RFC 826.
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const (
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ARPRequest ARPOp = 1
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ARPReply ARPOp = 2
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)
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// ARP is an ARP packet stored in a byte array as described in RFC 826.
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type ARP []byte
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func (a ARP) hardwareAddressSpace() uint16 { return uint16(a[0])<<8 | uint16(a[1]) }
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func (a ARP) protocolAddressSpace() uint16 { return uint16(a[2])<<8 | uint16(a[3]) }
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func (a ARP) hardwareAddressSize() int { return int(a[4]) }
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func (a ARP) protocolAddressSize() int { return int(a[5]) }
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// Op is the ARP opcode.
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func (a ARP) Op() ARPOp { return ARPOp(a[6])<<8 | ARPOp(a[7]) }
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// SetOp sets the ARP opcode.
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func (a ARP) SetOp(op ARPOp) {
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a[6] = uint8(op >> 8)
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a[7] = uint8(op)
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}
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// SetIPv4OverEthernet configures the ARP packet for IPv4-over-Ethernet.
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func (a ARP) SetIPv4OverEthernet() {
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a[0], a[1] = 0, 1 // htypeEthernet
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a[2], a[3] = 0x08, 0x00 // IPv4ProtocolNumber
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a[4] = 6 // macSize
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a[5] = uint8(IPv4AddressSize)
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}
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// HardwareAddressSender is the link address of the sender.
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// It is a view on to the ARP packet so it can be used to set the value.
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func (a ARP) HardwareAddressSender() []byte {
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const s = 8
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return a[s : s+6]
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}
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// ProtocolAddressSender is the protocol address of the sender.
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// It is a view on to the ARP packet so it can be used to set the value.
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func (a ARP) ProtocolAddressSender() []byte {
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const s = 8 + 6
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return a[s : s+4]
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}
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// HardwareAddressTarget is the link address of the target.
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// It is a view on to the ARP packet so it can be used to set the value.
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func (a ARP) HardwareAddressTarget() []byte {
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const s = 8 + 6 + 4
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return a[s : s+6]
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}
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// ProtocolAddressTarget is the protocol address of the target.
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// It is a view on to the ARP packet so it can be used to set the value.
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func (a ARP) ProtocolAddressTarget() []byte {
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const s = 8 + 6 + 4 + 6
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return a[s : s+4]
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}
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// IsValid reports whether this is an ARP packet for IPv4 over Ethernet.
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func (a ARP) IsValid() bool {
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if len(a) < ARPSize {
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return false
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}
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const htypeEthernet = 1
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const macSize = 6
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return a.hardwareAddressSpace() == htypeEthernet &&
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a.protocolAddressSpace() == uint16(IPv4ProtocolNumber) &&
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a.hardwareAddressSize() == macSize &&
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a.protocolAddressSize() == IPv4AddressSize
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}
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