From d02b74a5dcfed4bfc8f2f8e545bca4d2afabb296 Mon Sep 17 00:00:00 2001
From: Googler <noreply@google.com>
Date: Fri, 27 Apr 2018 10:37:02 -0700
Subject: Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463
---
 pkg/tcpip/header/arp.go | 90 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 pkg/tcpip/header/arp.go

(limited to 'pkg/tcpip/header/arp.go')

diff --git a/pkg/tcpip/header/arp.go b/pkg/tcpip/header/arp.go
new file mode 100644
index 000000000..af7f988f3
--- /dev/null
+++ b/pkg/tcpip/header/arp.go
@@ -0,0 +1,90 @@
+// Copyright 2016 The Netstack Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package header
+
+import "gvisor.googlesource.com/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 = 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
+}
-- 
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