Make gtcpip public for external use

gtcpip/header/ipv6_fragment.go

@@ -0,0 +1,158 @@
+// 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"
+
+	"github.com/sagernet/sing-tun/gtcpip"
+)
+
+const (
+	nextHdrFrag = 0
+	fragOff     = 2
+	more        = 3
+	idV6        = 4
+)
+
+var _ IPv6SerializableExtHdr = (*IPv6SerializableFragmentExtHdr)(nil)
+
+// IPv6SerializableFragmentExtHdr is used to serialize an IPv6 fragment
+// extension header as defined in RFC 8200 section 4.5.
+type IPv6SerializableFragmentExtHdr struct {
+	// FragmentOffset is the "fragment offset" field of an IPv6 fragment.
+	FragmentOffset uint16
+
+	// M is the "more" field of an IPv6 fragment.
+	M bool
+
+	// Identification is the "identification" field of an IPv6 fragment.
+	Identification uint32
+}
+
+// identifier implements IPv6SerializableFragmentExtHdr.
+func (h *IPv6SerializableFragmentExtHdr) identifier() IPv6ExtensionHeaderIdentifier {
+	return IPv6FragmentHeader
+}
+
+// length implements IPv6SerializableFragmentExtHdr.
+func (h *IPv6SerializableFragmentExtHdr) length() int {
+	return IPv6FragmentHeaderSize
+}
+
+// serializeInto implements IPv6SerializableFragmentExtHdr.
+func (h *IPv6SerializableFragmentExtHdr) serializeInto(nextHeader uint8, b []byte) int {
+	// Prevent too many bounds checks.
+	_ = b[IPv6FragmentHeaderSize:]
+	binary.BigEndian.PutUint32(b[idV6:], h.Identification)
+	binary.BigEndian.PutUint16(b[fragOff:], h.FragmentOffset<<ipv6FragmentExtHdrFragmentOffsetShift)
+	b[nextHdrFrag] = nextHeader
+	if h.M {
+		b[more] |= ipv6FragmentExtHdrMFlagMask
+	}
+	return IPv6FragmentHeaderSize
+}
+
+// IPv6Fragment represents an ipv6 fragment header stored in a byte array.
+// Most of the methods of IPv6Fragment access to the underlying slice without
+// checking the boundaries and could panic because of 'index out of range'.
+// Always call IsValid() to validate an instance of IPv6Fragment before using other methods.
+type IPv6Fragment []byte
+
+const (
+	// IPv6FragmentHeader header is the number used to specify that the next
+	// header is a fragment header, per RFC 2460.
+	IPv6FragmentHeader = 44
+
+	// IPv6FragmentHeaderSize is the size of the fragment header.
+	IPv6FragmentHeaderSize = 8
+)
+
+// IsValid performs basic validation on the fragment header.
+func (b IPv6Fragment) IsValid() bool {
+	return len(b) >= IPv6FragmentHeaderSize
+}
+
+// NextHeader returns the value of the "next header" field of the ipv6 fragment.
+func (b IPv6Fragment) NextHeader() uint8 {
+	return b[nextHdrFrag]
+}
+
+// FragmentOffset returns the "fragment offset" field of the ipv6 fragment.
+func (b IPv6Fragment) FragmentOffset() uint16 {
+	return binary.BigEndian.Uint16(b[fragOff:]) >> 3
+}
+
+// More returns the "more" field of the ipv6 fragment.
+func (b IPv6Fragment) More() bool {
+	return b[more]&1 > 0
+}
+
+// Payload implements Network.Payload.
+func (b IPv6Fragment) Payload() []byte {
+	return b[IPv6FragmentHeaderSize:]
+}
+
+// ID returns the value of the identifier field of the ipv6 fragment.
+func (b IPv6Fragment) ID() uint32 {
+	return binary.BigEndian.Uint32(b[idV6:])
+}
+
+// TransportProtocol implements Network.TransportProtocol.
+func (b IPv6Fragment) TransportProtocol() tcpip.TransportProtocolNumber {
+	return tcpip.TransportProtocolNumber(b.NextHeader())
+}
+
+// The functions below have been added only to satisfy the Network interface.
+
+// Checksum is not supported by IPv6Fragment.
+func (b IPv6Fragment) Checksum() uint16 {
+	panic("not supported")
+}
+
+// SourceAddress is not supported by IPv6Fragment.
+func (b IPv6Fragment) SourceAddress() tcpip.Address {
+	panic("not supported")
+}
+
+// DestinationAddress is not supported by IPv6Fragment.
+func (b IPv6Fragment) DestinationAddress() tcpip.Address {
+	panic("not supported")
+}
+
+// SetSourceAddress is not supported by IPv6Fragment.
+func (b IPv6Fragment) SetSourceAddress(tcpip.Address) {
+	panic("not supported")
+}
+
+// SetDestinationAddress is not supported by IPv6Fragment.
+func (b IPv6Fragment) SetDestinationAddress(tcpip.Address) {
+	panic("not supported")
+}
+
+// SetChecksum is not supported by IPv6Fragment.
+func (b IPv6Fragment) SetChecksum(uint16) {
+	panic("not supported")
+}
+
+// TOS is not supported by IPv6Fragment.
+func (b IPv6Fragment) TOS() (uint8, uint32) {
+	panic("not supported")
+}
+
+// SetTOS is not supported by IPv6Fragment.
+func (b IPv6Fragment) SetTOS(t uint8, l uint32) {
+	panic("not supported")
+}