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MIT License
Copyright (c) 2024 Fijxu <fijxu@nadeko.net>
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

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# natpmp-crystal
Work in progress implementation of RFC 6886 **NAT Port Mapping Protocol (NAT-PMP)**, client side.
Since RFC 6886 is a pretty simple protocol, it should be ready to use to requests mappings
## Installation
1. Add the dependency to your `shard.yml`:
```yaml
dependencies:
test:
github: fijxu/natpmp-crystal
```
2. Run `shards install`
## Usage
```crystal
# Create NAT-PMP client, replace the IP by the IP of your
# gateway
client = NatPMP::Client.new("192.168.1.1")
# Public address request
client.send_public_address_request # => {0, 128, 0, 22758, "104.0.0.0"}
client.send_public_address_request_raw # => Bytes[0, 128, 0, 0, 0, 0, 88, 230, 104, 0, 0, 0]
# Maps the internal port 25565 to external port 25565, TCP
client.request_mapping(25565, 25565, 2) # => {0, 130, 0, 22758, 25565, 25565, 7200}
# Destroys the mapping with internal port 25565, TCP
client.destroy_mapping(25565, 2) # => {0, 130, 0, 22758, 25565, 0, 0}
# Maps the internal port 22000 to external port 22000, UDP
client.request_mapping(22000, 22000, 1) # => {0, 129, 0, 22758, 22000, 22000, 7200}
# Destroys the mapping with internal port 25565, TCP
client.destroy_mapping(22000, 1) # => {0, 129, 0, 22758, 22000, 0, 0}
```
## Contributing
1. Fork it (<https://github.com/fijxu/natpmp-crystal/fork>)
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request
## Contributors
- [Fijxu](https://github.com/fijxu) - creator and maintainer

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name: natpmp-crystal
version: 0.1.0
authors:
- Fijxu <fijxu@nadeko.net>
crystal: '>= 1.14.0'
license: MIT

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require "./spec_helper"
describe Natpmpcrystal do
# TODO: Write tests
it "works" do
false.should eq(true)
end
end

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require "spec"
require "../src/natpmpcrystal"

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require "socket"
require "benchmark"
module NatPMP
enum ResultCodes
SUCCESS = 0
UNSUPPORTED_VERSION = 1
NOT_AUTHORIZED_OR_REFUSED = 2
NETWORK_FAILURE = 3
OUT_OF_RESOURCES = 4
UNSUPPORTED_OPCODE = 5
end
struct MappingPacket
@vers : UInt8 = 0_u8
@op : UInt8
@reserved : UInt16 = 0_u16
@internal_port : UInt16
@external_port : UInt16
@lifetime : UInt32 = 0_u32
def initialize(@internal_port, @external_port, @lifetime = 7200, @op = 1)
raise ArgumentError.new("operation should be either 1_u8 for UDP or 2_u8 for TCP") if ![1, 2].includes?(@op)
end
def to_io
io = IO::Memory.new(12)
io.write_bytes(@vers, IO::ByteFormat::BigEndian)
io.write_bytes(@op, IO::ByteFormat::BigEndian)
io.write_bytes(@reserved, IO::ByteFormat::BigEndian)
io.write_bytes(@internal_port, IO::ByteFormat::BigEndian)
io.write_bytes(@external_port, IO::ByteFormat::BigEndian)
io.write_bytes(@lifetime, IO::ByteFormat::BigEndian)
return io
end
def to_slice
# This is not actually a Slice, it's an StaticArray so I don't
# think this member function should be called like this.
slice = uninitialized UInt8[12]
IO::ByteFormat::BigEndian.encode(@op, o = Bytes.new(1))
IO::ByteFormat::BigEndian.encode(@internal_port, i = Bytes.new(2))
IO::ByteFormat::BigEndian.encode(@external_port, e = Bytes.new(2))
IO::ByteFormat::BigEndian.encode(@lifetime, l = Bytes.new(4))
slice[0] = 0 # vers is always 0
slice[1] = o[0]
slice[2] = 0 # RESERVED, always 0
slice[3] = 0 # RESERVED, always 0
slice[4] = i[0]
slice[5] = i[1]
slice[6] = e[0]
slice[7] = e[1]
slice[8] = l[0]
slice[9] = l[1]
slice[10] = l[2]
slice[11] = l[3]
return slice
end
end
class Client
@socket : UDPSocket
@gateway_ip : String
# Overload
def initialize(gateway_ip : URI)
initialize(gateway_ip.path)
end
def initialize(@gateway_ip : String, autoconnect : Bool = true)
# The specification is IPV4 only!
@socket = UDPSocket.new(Socket::Family::INET)
@socket.reuse_port = true
@socket.reuse_address = true
@socket.bind 5350
if autoconnect
connect()
end
end
def connect
@socket.connect(@gateway_ip, 5351)
end
def send_public_address_request_raw : Bytes
@socket.send("\x00\x00")
msg = Bytes.new(12)
@socket.receive(msg)
return msg
end
def send_public_address_request
@socket.send("\x00\x00")
msg = Bytes.new(12)
@socket.read_timeout = 250.milliseconds
8.times do |i|
begin
@socket.receive(msg)
break
rescue IO::TimeoutError
@socket.read_timeout = @socket.read_timeout.not_nil!*2
next
rescue
raise "The gateway '#{@gateway_ip}' does not support NAT-PMP"
break
end
end
vers : UInt8 = msg[0]
op : UInt8 = msg[1]
result_code = decode_msg(UInt16, msg[2..3])
epoch = decode_msg(UInt32, msg[4..7])
if result_code != 0
ip_address = nil
else
ip_address = get_ip_address(msg[8..11])
end
return vers, op, result_code, epoch, ip_address
end
# https://datatracker.ietf.org/doc/html/rfc6886#section-3.3
def request_mapping(internal_port : UInt16, external_port : UInt16, operation : UInt8, lifetime : UInt32 = 7200)
request = MappingPacket.new(internal_port, external_port, lifetime, operation).to_slice
msg = Bytes.new(16)
@socket.send(request)
@socket.receive(msg)
vers : UInt8 = msg[0]
op : UInt8 = msg[1]
result_code = decode_msg(UInt16, msg[2..3])
epoch = decode_msg(UInt32, msg[4..7])
internal_port = decode_msg(UInt16, msg[8..9])
external_port = decode_msg(UInt16, msg[10..11])
lifetime = decode_msg(UInt32, msg[12..15])
return vers, op, result_code, epoch, internal_port, external_port, lifetime
end
# https://datatracker.ietf.org/doc/html/rfc6886#section-3.4
def destroy_mapping(internal_port : UInt16, operation : UInt8)
request = MappingPacket.new(internal_port, 0, 0, operation).to_slice
msg = Bytes.new(16)
@socket.send(request)
@socket.receive(msg)
vers : UInt8 = msg[0]
op : UInt8 = msg[1]
result_code = decode_msg(UInt16, msg[2..3])
epoch = decode_msg(UInt32, msg[4..7])
internal_port = decode_msg(UInt16, msg[8..9])
external_port = decode_msg(UInt16, msg[10..11])
lifetime = decode_msg(UInt32, msg[12..15])
return vers, op, result_code, epoch, internal_port, external_port, lifetime
end
private macro decode_msg(type, msg)
IO::ByteFormat::BigEndian.decode({{type}}, {{msg}})
end
private def get_ip_address(msg)
"#{msg[0]}.#{msg[1]}.#{msg[2]}.#{msg[3]}"
end
end
end