Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 106 insertions, 0 deletions

diff --git a/pkg/tcpip/header/udp.go b/pkg/tcpip/header/udp.go
new file mode 100644
index 000000000..7c2548634
--- /dev/null
+++ b/pkg/tcpip/header/udp.go
@@ -0,0 +1,106 @@
+// 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 (
+	"encoding/binary"
+
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+)
+
+const (
+	udpSrcPort  = 0
+	udpDstPort  = 2
+	udpLength   = 4
+	udpChecksum = 6
+)
+
+// UDPFields contains the fields of a UDP packet. It is used to describe the
+// fields of a packet that needs to be encoded.
+type UDPFields struct {
+	// SrcPort is the "source port" field of a UDP packet.
+	SrcPort uint16
+
+	// DstPort is the "destination port" field of a UDP packet.
+	DstPort uint16
+
+	// Length is the "length" field of a UDP packet.
+	Length uint16
+
+	// Checksum is the "checksum" field of a UDP packet.
+	Checksum uint16
+}
+
+// UDP represents a UDP header stored in a byte array.
+type UDP []byte
+
+const (
+	// UDPMinimumSize is the minimum size of a valid UDP packet.
+	UDPMinimumSize = 8
+
+	// UDPProtocolNumber is UDP's transport protocol number.
+	UDPProtocolNumber tcpip.TransportProtocolNumber = 17
+)
+
+// SourcePort returns the "source port" field of the udp header.
+func (b UDP) SourcePort() uint16 {
+	return binary.BigEndian.Uint16(b[udpSrcPort:])
+}
+
+// DestinationPort returns the "destination port" field of the udp header.
+func (b UDP) DestinationPort() uint16 {
+	return binary.BigEndian.Uint16(b[udpDstPort:])
+}
+
+// Length returns the "length" field of the udp header.
+func (b UDP) Length() uint16 {
+	return binary.BigEndian.Uint16(b[udpLength:])
+}
+
+// Payload returns the data contained in the UDP datagram.
+func (b UDP) Payload() []byte {
+	return b[UDPMinimumSize:]
+}
+
+// Checksum returns the "checksum" field of the udp header.
+func (b UDP) Checksum() uint16 {
+	return binary.BigEndian.Uint16(b[udpChecksum:])
+}
+
+// SetSourcePort sets the "source port" field of the udp header.
+func (b UDP) SetSourcePort(port uint16) {
+	binary.BigEndian.PutUint16(b[udpSrcPort:], port)
+}
+
+// SetDestinationPort sets the "destination port" field of the udp header.
+func (b UDP) SetDestinationPort(port uint16) {
+	binary.BigEndian.PutUint16(b[udpDstPort:], port)
+}
+
+// SetChecksum sets the "checksum" field of the udp header.
+func (b UDP) SetChecksum(checksum uint16) {
+	binary.BigEndian.PutUint16(b[udpChecksum:], checksum)
+}
+
+// CalculateChecksum calculates the checksum of the udp packet, given the total
+// length of the packet and the checksum of the network-layer pseudo-header
+// (excluding the total length) and the checksum of the payload.
+func (b UDP) CalculateChecksum(partialChecksum uint16, totalLen uint16) uint16 {
+	// Add the length portion of the checksum to the pseudo-checksum.
+	tmp := make([]byte, 2)
+	binary.BigEndian.PutUint16(tmp, totalLen)
+	checksum := Checksum(tmp, partialChecksum)
+
+	// Calculate the rest of the checksum.
+	return Checksum(b[:UDPMinimumSize], checksum)
+}
+
+// Encode encodes all the fields of the udp header.
+func (b UDP) Encode(u *UDPFields) {
+	binary.BigEndian.PutUint16(b[udpSrcPort:], u.SrcPort)
+	binary.BigEndian.PutUint16(b[udpDstPort:], u.DstPort)
+	binary.BigEndian.PutUint16(b[udpLength:], u.Length)
+	binary.BigEndian.PutUint16(b[udpChecksum:], u.Checksum)
+}