127 lines
4.3 KiB
Swift
127 lines
4.3 KiB
Swift
//
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// ConnectionStrategy.swift
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// TunnelKit
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//
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// Created by Davide De Rosa on 6/18/18.
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// Copyright © 2018 London Trust Media. All rights reserved.
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//
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import Foundation
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import NetworkExtension
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import SwiftyBeaver
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private let log = SwiftyBeaver.self
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class ConnectionStrategy {
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private let hostname: String
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private let prefersResolvedAddresses: Bool
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private var resolvedAddresses: [String]?
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private let endpointProtocols: [TunnelKitProvider.EndpointProtocol]
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private var currentProtocolIndex = 0
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init(hostname: String, configuration: TunnelKitProvider.Configuration) {
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precondition(!configuration.prefersResolvedAddresses || !(configuration.resolvedAddresses?.isEmpty ?? true))
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self.hostname = hostname
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prefersResolvedAddresses = configuration.prefersResolvedAddresses
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resolvedAddresses = configuration.resolvedAddresses
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endpointProtocols = configuration.endpointProtocols
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}
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func createSocket(
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from provider: NEProvider,
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timeout: Int,
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preferredAddress: String? = nil,
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queue: DispatchQueue,
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completionHandler: @escaping (GenericSocket?, Error?) -> Void) {
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// reuse preferred address
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if let preferredAddress = preferredAddress {
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log.debug("Pick preferred address: \(preferredAddress)")
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let socket = provider.createSocket(to: preferredAddress, protocol: currentProtocol())
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completionHandler(socket, nil)
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return
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}
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// use any resolved address
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if prefersResolvedAddresses, let resolvedAddress = anyResolvedAddress() {
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log.debug("Pick resolved address: \(resolvedAddress)")
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let socket = provider.createSocket(to: resolvedAddress, protocol: currentProtocol())
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completionHandler(socket, nil)
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return
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}
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// fall back to DNS
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log.debug("DNS resolve hostname: \(hostname)")
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DNSResolver.resolve(hostname, timeout: timeout, queue: queue) { (addresses, error) in
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// refresh resolved addresses
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if let resolved = addresses, !resolved.isEmpty {
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self.resolvedAddresses = resolved
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log.debug("DNS resolved addresses: \(resolved)")
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} else {
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log.error("DNS resolution failed!")
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}
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guard let targetAddress = self.resolvedAddress(from: addresses) else {
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log.error("No resolved or fallback address available")
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completionHandler(nil, TunnelKitProvider.ProviderError.dnsFailure)
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return
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}
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let socket = provider.createSocket(to: targetAddress, protocol: self.currentProtocol())
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completionHandler(socket, nil)
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}
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}
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func tryNextProtocol() -> Bool {
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let next = currentProtocolIndex + 1
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guard next < endpointProtocols.count else {
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log.debug("No more protocols available")
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return false
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}
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currentProtocolIndex = next
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log.debug("Fall back to next protocol: \(currentProtocol())")
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return true
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}
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private func currentProtocol() -> TunnelKitProvider.EndpointProtocol {
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return endpointProtocols[currentProtocolIndex]
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}
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private func resolvedAddress(from addresses: [String]?) -> String? {
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guard let resolved = addresses, !resolved.isEmpty else {
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return anyResolvedAddress()
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}
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return resolved[0]
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}
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private func anyResolvedAddress() -> String? {
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guard let addresses = resolvedAddresses, !addresses.isEmpty else {
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return nil
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}
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let n = Int(arc4random() % UInt32(addresses.count))
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return addresses[n]
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}
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}
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private extension NEProvider {
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func createSocket(to address: String, protocol endpointProtocol: TunnelKitProvider.EndpointProtocol) -> GenericSocket {
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let endpoint = NWHostEndpoint(hostname: address, port: "\(endpointProtocol.port)")
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switch endpointProtocol.socketType {
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case .udp:
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let impl = createUDPSession(to: endpoint, from: nil)
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return NEUDPSocket(impl: impl)
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case .tcp:
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let impl = createTCPConnection(to: endpoint, enableTLS: false, tlsParameters: nil, delegate: nil)
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return NETCPSocket(impl: impl)
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}
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}
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}
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