tunnelkit/TunnelKit/Sources/Core/IPHeader.swift

58 lines
1.9 KiB
Swift

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