WIP NWEndpoint changes

New macos 15.0+ APIs uses Network.NWEndpoint for both
TCP remoteEndpoint (new name is remoteFlowEndpoint) and
UDP localEndpoint (new name is localFlowEndpoint).
The old APIs use a different type, which is NetworkExtension.NWEndpoint.

Network.NWEndpoint is available also on older macos versions, so we can just use that
type in our FlowTCP and FlowUDP classes, then for older versions convert from
NetworkExtension.NWEndpoint to it

Author: kp-michele-emiliani

ProxyExtension/IO/FlowProtocols.swift

@@ -1,5 +1,6 @@
 import Foundation
 import NetworkExtension
+import Network
 
 // Flow base protocol we use in place of NEAppProxyFlow, it also provides shortcuts for common functions.
 protocol Flow {
@@ -25,18 +26,19 @@ extension Flow {
             // Check if the address is an IPv6 address. IPv6 addresses always contain a ":"
             // We can't do the opposite (such as just checking for "." for an IPv4 address) due to IPv4-mapped IPv6 addresses
             // which are IPv6 addresses but include IPv4 address notation.
-            if let endpoint = flowTCP.flowEndpoint as? NWEndpoint {
+            let endpoint: Network.NWEndpoint? = flowTCP.flowEndpoint
+            if endpoint != nil {
                 // We have a valid NWEndpoint - let's see if it's IPv6
-                if endpoint.hostname.contains(":") {
+                if endpoint.host.contains(":") {
                     return true
                 }
             }
         } else if let flowUDP = self as? FlowUDP {
             // Use localEndpoint for UDP flows as UDP (as a "connectionless protocol")
             // doesn't have a fixed flowEndpoint
-            if let endpoint = flowUDP.localEndpoint as? NWEndpoint {
+            if let endpoint = flowUDP.localEndpoint {
                 // We have a valid NWEndpoint - let's see if it's IPv6
-                if endpoint.hostname.contains(":") {
+                if endpoint.host.contains(":") {
                     return true
                 }
             }
@@ -51,13 +53,13 @@ extension Flow {
 // FlowTCP and FlowUDP protocols abstract the relevant parts of NEAppProxyTCPFlow
 // and NEAppProxyUDPFlow for increased flexibility and improved testability.
 protocol FlowTCP: Flow {
-    var flowEndpoint: NWEndpoint { get }
+    var flowEndpoint: Network.NWEndpoint { get }
     func readData(completionHandler: @escaping (Data?, Error?) -> Void)
     func write(_ data: Data, withCompletionHandler completionHandler: @escaping (Error?) -> Void)
 }
 
 protocol FlowUDP: Flow {
     func readDatagrams(completionHandler: @escaping ([Data]?, [NWEndpoint]?, Error?) -> Void)
     func writeDatagrams(_ datagrams: [Data], sentBy remoteEndpoints: [NWEndpoint], completionHandler: @escaping (Error?) -> Void)
-    var localEndpoint: NWEndpoint? { get }
+    var localEndpoint: Network.NWEndpoint? { get }
 }