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b560386c1a
This adds a new IP Protocol type, TSMP on protocol number 99 for sending inter-tailscale messages over WireGuard, currently just for why a peer rejects TCP SYNs (ACL rejection, shields up, and in the future: nothing listening, something listening on that port but wrong interface, etc) Updates #1094 Updates tailscale/corp#1185 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
53 lines
1.5 KiB
Go
53 lines
1.5 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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"errors"
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"math"
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)
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const tcpHeaderLength = 20
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// maxPacketLength is the largest length that all headers support.
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// IPv4 headers using uint16 for this forces an upper bound of 64KB.
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const maxPacketLength = math.MaxUint16
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var (
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// errSmallBuffer is returned when Marshal receives a buffer
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// too small to contain the header to marshal.
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errSmallBuffer = errors.New("buffer too small")
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// errLargePacket is returned when Marshal receives a payload
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// larger than the maximum representable size in header
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// fields.
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errLargePacket = errors.New("packet too large")
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)
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// Header is a packet header capable of marshaling itself into a byte
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// buffer.
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type Header interface {
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// Len returns the length of the marshaled packet.
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Len() int
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// Marshal serializes the header into buf, which must be at
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// least Len() bytes long. Implementations of Marshal assume
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// that bytes after the first Len() are payload bytes for the
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// purpose of computing length and checksum fields. Marshal
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// implementations must not allocate memory.
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Marshal(buf []byte) error
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}
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// Generate generates a new packet with the given Header and
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// payload. This function allocates memory, see Header.Marshal for an
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// allocation-free option.
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func Generate(h Header, payload []byte) []byte {
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hlen := h.Len()
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buf := make([]byte, hlen+len(payload))
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copy(buf[hlen:], payload)
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h.Marshal(buf)
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return buf
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}
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