58 lines
1.9 KiB
Swift
58 lines
1.9 KiB
Swift
//
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// IPHeader.swift
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// TunnelKit
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//
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// Created by Davide De Rosa on 5/12/20.
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// Copyright (c) 2020 Davide De Rosa. All rights reserved.
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//
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// https://github.com/passepartoutvpn
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//
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// This file is part of TunnelKit.
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//
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// TunnelKit is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// TunnelKit is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with TunnelKit. If not, see <http://www.gnu.org/licenses/>.
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import Foundation
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/// Helper for handling IP headers.
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public struct IPHeader {
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private static let ipV4: UInt8 = 4
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private static let ipV6: UInt8 = 6
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private static let ipV4ProtocolNumber = AF_INET as NSNumber
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private static let ipV6ProtocolNumber = AF_INET6 as NSNumber
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private static let fallbackProtocolNumber = ipV4ProtocolNumber
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/**
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Returns the protocol number from the IP header of a data packet.
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- Parameter packet: The data to inspect.
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- Returns: A protocol number between `AF_INET` and `AF_INET6`.
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*/
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public static func protocolNumber(inPacket packet: Data) -> NSNumber {
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guard !packet.isEmpty else {
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return fallbackProtocolNumber
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}
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// 'packet' contains the decrypted incoming IP packet data
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// The first 4 bits identify the IP version
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let ipVersion = (packet[0] & 0xf0) >> 4
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assert(ipVersion == ipV4 || ipVersion == ipV6)
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return (ipVersion == ipV6) ? ipV6ProtocolNumber : ipV4ProtocolNumber
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}
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}
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