mirror of
https://github.com/tailscale/tailscale.git
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118 lines
3.0 KiB
Go
118 lines
3.0 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package packet
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import (
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"encoding/binary"
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"fmt"
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"inet.af/netaddr"
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)
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// IP6 is an IPv6 address.
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type IP6 struct {
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Hi, Lo uint64
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}
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// IP6FromRaw16 converts a raw 16-byte IPv6 address to an IP6.
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func IP6FromRaw16(ip [16]byte) IP6 {
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return IP6{binary.BigEndian.Uint64(ip[:8]), binary.BigEndian.Uint64(ip[8:])}
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}
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// IP6FromNetaddr converts a netaddr.IP to an IP6. Panics if !ip.Is6.
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func IP6FromNetaddr(ip netaddr.IP) IP6 {
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if !ip.Is6() {
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panic(fmt.Sprintf("IP6FromNetaddr called with non-v6 addr %q", ip))
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}
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return IP6FromRaw16(ip.As16())
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}
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// Netaddr converts ip to a netaddr.IP.
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func (ip IP6) Netaddr() netaddr.IP {
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var b [16]byte
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binary.BigEndian.PutUint64(b[:8], ip.Hi)
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binary.BigEndian.PutUint64(b[8:], ip.Lo)
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return netaddr.IPFrom16(b)
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}
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func (ip IP6) String() string {
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return ip.Netaddr().String()
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}
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func (ip IP6) IsMulticast() bool {
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return (ip.Hi >> 56) == 0xFF
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}
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func (ip IP6) IsLinkLocalUnicast() bool {
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return (ip.Hi >> 48) == 0xFE80
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}
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// ip6HeaderLength is the length of an IPv6 header with no IP options.
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const ip6HeaderLength = 40
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// IP6Header represents an IPv6 packet header.
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type IP6Header struct {
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IPProto IPProto
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IPID uint32 // only lower 20 bits used
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SrcIP IP6
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DstIP IP6
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}
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// Len implements Header.
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func (h IP6Header) Len() int {
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return ip6HeaderLength
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}
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// Marshal implements Header.
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func (h IP6Header) Marshal(buf []byte) error {
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if len(buf) < h.Len() {
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return errSmallBuffer
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}
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if len(buf) > maxPacketLength {
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return errLargePacket
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}
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binary.BigEndian.PutUint32(buf[:4], h.IPID&0x000FFFFF)
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buf[0] = 0x60
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binary.BigEndian.PutUint16(buf[4:6], uint16(len(buf)-ip6HeaderLength)) // Total length
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buf[6] = uint8(h.IPProto) // Inner protocol
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buf[7] = 64 // TTL
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binary.BigEndian.PutUint64(buf[8:16], h.SrcIP.Hi)
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binary.BigEndian.PutUint64(buf[16:24], h.SrcIP.Lo)
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binary.BigEndian.PutUint64(buf[24:32], h.DstIP.Hi)
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binary.BigEndian.PutUint64(buf[32:40], h.DstIP.Lo)
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return nil
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}
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// ToResponse implements Header.
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func (h *IP6Header) ToResponse() {
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h.SrcIP, h.DstIP = h.DstIP, h.SrcIP
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// Flip the bits in the IPID. If incoming IPIDs are distinct, so are these.
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h.IPID = (^h.IPID) & 0x000FFFFF
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}
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// marshalPseudo serializes h into buf in the "pseudo-header" form
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// required when calculating UDP checksums.
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func (h IP6Header) marshalPseudo(buf []byte) error {
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if len(buf) < h.Len() {
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return errSmallBuffer
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}
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if len(buf) > maxPacketLength {
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return errLargePacket
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}
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binary.BigEndian.PutUint64(buf[:8], h.SrcIP.Hi)
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binary.BigEndian.PutUint64(buf[8:16], h.SrcIP.Lo)
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binary.BigEndian.PutUint64(buf[16:24], h.DstIP.Hi)
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binary.BigEndian.PutUint64(buf[24:32], h.DstIP.Lo)
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binary.BigEndian.PutUint32(buf[32:36], uint32(len(buf)-h.Len()))
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buf[36] = 0
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buf[37] = 0
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buf[38] = 0
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buf[39] = 17 // NextProto
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return nil
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}
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