For important background information, read Extra-ordinary Networking before reading this. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Network Interface APIs Most developers don’t need to interact directly with network interfaces. If you do, read this post for a summary of the APIs available to you. Before you read this, read Network Interface Concepts. Interface List The standard way to get a list of interfaces and their addresses is getifaddrs. To learn more about this API, see its man page. A network interface has four fundamental attributes: A set of flags — These are packed into a CUnsignedInt. The flags bits are declared in <net/if.h>, starting with IFF_UP. An interface type — See Network Interface Type, below. An interface index — Valid indexes are greater than 0. A BSD interface name. For example, an Ethernet interface might be called en0. The interface name is shared between multiple network interfaces running over a given hardware interface. For example, IPv4 and IPv6 running over that Ethernet interface will both have the name en0. WARNING BSD interface names are not considered API. There’s no guarantee, for example, that an iPhone’s Wi-Fi interface is en0. You can map between the last two using if_indextoname and if_nametoindex. See the if_indextoname man page for details. An interface may also have address information. If present, this always includes the interface address (ifa_addr) and the network mask (ifa_netmask). In addition: Broadcast-capable interfaces (IFF_BROADCAST) have a broadcast address (ifa_broadaddr, which is an alias for ifa_dstaddr). Point-to-point interfaces (IFF_POINTOPOINT) have a destination address (ifa_dstaddr). Calling getifaddrs from Swift is a bit tricky. For an example of this, see QSocket: Interfaces. IP Address List Once you have getifaddrs working, it’s relatively easy to manipulate the results to build a list of just IP addresses, a list of IP addresses for each interface, and so on. QSocket: Interfaces has some Swift snippets that show this. Interface List Updates The interface list can change over time. Hardware interfaces can be added and removed, network interfaces come up and go down, and their addresses can change. It’s best to avoid caching information from getifaddrs. If thats unavoidable, use the kNotifySCNetworkChange Darwin notification to update your cache. For information about registering for Darwin notifications, see the notify man page (in section 3). This notification just tells you that something has changed. It’s up to you to fetch the new interface list and adjust your cache accordingly. You’ll find that this notification is sometimes posted numerous times in rapid succession. To avoid unnecessary thrashing, debounce it. While the Darwin notification API is easy to call from Swift, Swift does not import kNotifySCNetworkChange. To fix that, define that value yourself, calling a C function to get the value: var kNotifySCNetworkChange: UnsafePointer<CChar> { networkChangeNotifyKey() } Here’s what that C function looks like: extern const char * networkChangeNotifyKey(void) { return kNotifySCNetworkChange; } Network Interface Type There are two ways to think about a network interface’s type. Historically there were a wide variety of weird and wonderful types of network interfaces. The following code gets this legacy value for a specific BSD interface name: func legacyTypeForInterfaceNamed(_ name: String) -> UInt8? { var addrList: UnsafeMutablePointer<ifaddrs>? = nil let err = getifaddrs(&addrList) // In theory we could check `errno` here but, honestly, what are gonna // do with that info? guard err >= 0, let first = addrList else { return nil } defer { freeifaddrs(addrList) } return sequence(first: first, next: { $0.pointee.ifa_next }) .compactMap { addr in guard let nameC = addr.pointee.ifa_name, name == String(cString: nameC), let sa = addr.pointee.ifa_addr, sa.pointee.sa_family == AF_LINK, let data = addr.pointee.ifa_data else { return nil } return data.assumingMemoryBound(to: if_data.self).pointee.ifi_type } .first } The values are defined in <net/if_types.h>, starting with IFT_OTHER. However, this value is rarely useful because many interfaces ‘look like’ Ethernet and thus have a type of IFT_ETHER. Network framework has the concept of an interface’s functional type. This is an indication of how the interface fits into the system. There are two ways to get an interface’s functional type: If you’re using Network framework and have an NWInterface value, get the type property. If not, call ioctl with a SIOCGIFFUNCTIONALTYPE request. The return values are defined in <net/if.h>, starting with IFRTYPE_FUNCTIONAL_UNKNOWN. Swift does not import SIOCGIFFUNCTIONALTYPE, so it’s best to write this code in a C: extern uint32_t functionalTypeForInterfaceNamed(const char * name) { int fd = socket(AF_INET, SOCK_DGRAM, 0); if (fd < 0) { return IFRTYPE_FUNCTIONAL_UNKNOWN; } struct ifreq ifr = {}; strlcpy(ifr.ifr_name, name, sizeof(ifr.ifr_name)); bool success = ioctl(fd, SIOCGIFFUNCTIONALTYPE, &ifr) >= 0; int junk = close(fd); assert(junk == 0); if ( ! success ) { return IFRTYPE_FUNCTIONAL_UNKNOWN; } return ifr.ifr_ifru.ifru_functional_type; } Finally, TN3158 Resolving Xcode 15 device connection issues documents the SIOCGIFDIRECTLINK flag as a specific way to identify the network interfaces uses by Xcode for device connection traffic. Revision History 2025-12-10 Added info about SIOCGIFDIRECTLINK. 2023-07-19 First posted.

For important background information, read Extra-ordinary Networking before reading this. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Working with a Wi-Fi Accessory Building an app that works with a Wi-Fi accessory presents specific challenges. This post discusses those challenges and some recommendations for how to address them. Note While my focus here is iOS, much of the info in this post applies to all Apple platforms. IMPORTANT iOS 18 introduced AccessorySetupKit, a framework to simplify the discovery and configuration of an accessory. I’m not fully up to speed on that framework myself, but I encourage you to watch WWDC 2024 Session 10203 Meet AccessorySetupKit and read the framework documentation. IMPORTANT iOS 26 introduced WiFiAware, a framework for setting up communication with Wi-Fi Aware accessories. Wi-Fi Aware is an industry standard to securely discover, pair, and communicate with nearby devices. This is especially useful for stand-alone accessories (defined below). For more on this framework, watch WWDC 2025 Session 228 Supercharge device connectivity with Wi-Fi Aware and read the framework documentation. For information on how to create a Wi-Fi Aware accessory that works with iPhone, go to Developer > Accessories, download Accessory Design Guidelines for Apple Devices, and review the Wi-Fi Aware chapter. Accessory Categories I classify Wi-Fi accessories into three different categories. A bound accessory is ultimately intended to join the user’s Wi-Fi network. It may publish its own Wi-Fi network during the setup process, but the goal of that process is to get the accessory on to the existing network. Once that’s done, your app interacts with the accessory using ordinary networking APIs. An example of a bound accessory is a Wi-Fi capable printer. A stand-alone accessory publishes a Wi-Fi network at all times. An iOS device joins that network so that your app can interact with it. The accessory never provides access to the wider Internet. An example of a stand-alone accessory is a video camera that users take with them into the field. You might want to write an app that joins the camera’s network and downloads footage from it. A gateway accessory is one that publishes a Wi-Fi network that provides access to the wider Internet. Your app might need to interact with the accessory during the setup process, but after that it’s useful as is. An example of this is a Wi-Fi to WWAN gateway. Not all accessories fall neatly into these categories. Indeed, some accessories might fit into multiple categories, or transition between categories. Still, I’ve found these categories to be helpful when discussing various accessory integration challenges. Do You Control the Firmware? The key question here is Do you control the accessory’s firmware? If so, you have a bunch of extra options that will make your life easier. If not, you have to adapt to whatever the accessory’s current firmware does. Simple Improvements If you do control the firmware, I strongly encourage you to: Support IPv6 Implement Bonjour [1] These two things are quite easy to do — most embedded platforms support them directly, so it’s just a question of turning them on — and they will make your life significantly easier: Link-local addresses are intrinsic to IPv6, and IPv6 is intrinsic to Apple platforms. If your accessory supports IPv6, you’ll always be able to communicate with it, regardless of how messed up the IPv4 configuration gets. Similarly, if you support Bonjour, you’ll always be able to find your accessory on the network. [1] Bonjour is an Apple term for three Internet standards: RFC 3927 Dynamic Configuration of IPv4 Link-Local Addresses RFC 6762 Multicast DNS RFC 6763 DNS-Based Service Discovery WAC For a bound accessory, support Wireless Accessory Configuration (WAC). This is a relatively big ask — supporting WAC requires you to join the MFi Program — but it has some huge benefits: You don’t need to write an app to configure your accessory. The user will be able to do it directly from Settings. If you do write an app, you can use the EAWiFiUnconfiguredAccessoryBrowser class to simplify your configuration process. HomeKit For a bound accessory that works in the user’s home, consider supporting HomeKit. This yields the same onboarding benefits as WAC, and many other benefits as well. Also, you can get started with the HomeKit Open Source Accessory Development Kit (ADK). Bluetooth LE If your accessory supports Bluetooth LE, think about how you can use that to improve your app’s user experience. For an example of that, see SSID Scanning, below. Claiming the Default Route, Or Not? If your accessory publishes a Wi-Fi network, a key design decision is whether to stand up enough infrastructure for an iOS device to make it the default route. IMPORTANT To learn more about how iOS makes the decision to switch the default route, see The iOS Wi-Fi Lifecycle and Network Interface Concepts. This decision has significant implications. If the accessory’s network becomes the default route, most network connections from iOS will be routed to your accessory. If it doesn’t provide a path to the wider Internet, those connections will fail. That includes connections made by your own app. Note It’s possible to get around this by forcing your network connections to run over WWAN. See Binding to an Interface in Network Interface Techniques and Running an HTTP Request over WWAN. Of course, this only works if the user has WWAN. It won’t help most iPad users, for example. OTOH, if your accessory’s network doesn’t become the default route, you’ll see other issues. iOS will not auto-join such a network so, if the user locks their device, they’ll have to manually join the network again. In my experience a lot of accessories choose to become the default route in situations where they shouldn’t. For example, a bound accessory is never going to be able to provide a path to the wider Internet so it probably shouldn’t become the default route. However, there are cases where it absolutely makes sense, the most obvious being that of a gateway accessory. Acting as a Captive Network, or Not? If your accessory becomes the default route you must then decide whether to act like a captive network or not. IMPORTANT To learn more about how iOS determines whether a network is captive, see The iOS Wi-Fi Lifecycle. For bound and stand-alone accessories, becoming a captive network is generally a bad idea. When the user joins your network, the captive network UI comes up and they have to successfully complete it to stay on the network. If they cancel out, iOS will leave the network. That makes it hard for the user to run your app while their iOS device is on your accessory’s network. In contrast, it’s more reasonable for a gateway accessory to act as a captive network. SSID Scanning Many developers think that TN3111 iOS Wi-Fi API overview is lying when it says: iOS does not have a general-purpose API for Wi-Fi scanning It is not. Many developers think that the Hotspot Helper API is a panacea that will fix all their Wi-Fi accessory integration issues, if only they could get the entitlement to use it. It will not. Note this comment in the official docs: NEHotspotHelper is only useful for hotspot integration. There are both technical and business restrictions that prevent it from being used for other tasks, such as accessory integration or Wi-Fi based location. Even if you had the entitlement you would run into these technical restrictions. The API was specifically designed to support hotspot navigation — in this context hotspots are “Wi-Fi networks where the user must interact with the network to gain access to the wider Internet” — and it does not give you access to on-demand real-time Wi-Fi scan results. Many developers look at another developer’s app, see that it’s displaying real-time Wi-Fi scan results, and think there’s some special deal with Apple that’ll make that work. There is not. In reality, Wi-Fi accessory developers have come up with a variety of creative approaches for this, including: If you have a bound accessory, you might add WAC support, which makes this whole issue go away. In many cases, you can avoid the need for Wi-Fi scan results by adopting AccessorySetupKit. You might build your accessory with a barcode containing the info required to join its network, and scan that from your app. This is the premise behind the Configuring a Wi-Fi Accessory to Join the User’s Network sample code. You might configure all your accessories to have a common SSID prefix, and then take advantage of the prefix support in NEHotspotConfigurationManager. See Programmatically Joining a Network, below. You might have your app talk to your accessory via some other means, like Bluetooth LE, and have the accessory scan for Wi-Fi networks and return the results. Programmatically Joining a Network Network Extension framework has an API, NEHotspotConfigurationManager, to programmatically join a network, either temporarily or as a known network that supports auto-join. For the details, see Wi-Fi Configuration. One feature that’s particularly useful is it’s prefix support, allowing you to create a configuration that’ll join any network with a specific prefix. See the init(ssidPrefix:) initialiser for the details. For examples of how to use this API, see: Configuring a Wi-Fi Accessory to Join the User’s Network — It shows all the steps for one approach for getting a non-WAC bound accessory on to the user’s network. NEHotspotConfiguration Sample — Use this to explore the API in general. Secure Communication Users expect all network communication to be done securely. For some ideas on how to set up a secure connection to an accessory, see TLS For Accessory Developers. Revision History 2025-11-05 Added a link to the Accessory Design Guidelines for Apple Devices. 2025-06-19 Added a preliminary discussion of Wi-Fi Aware. 2024-09-12 Improved the discussion of AccessorySetupKit. 2024-07-16 Added a preliminary discussion of AccessorySetupKit. 2023-10-11 Added the HomeKit section. Fixed the link in Secure Communication to point to TLS For Accessory Developers. 2023-07-23 First posted.

This is a topic that’s come up a few times on the forums, so I thought I’d write up a summary of the issues I’m aware of. If you have questions or comments, start a new thread in the App & System Services > Networking subtopic and tag it with Network Extension. That way I’ll be sure to see it go by. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Network Extension Provider Packaging There are two ways to package a network extension provider: App extension ( appex ) System extension ( sysex ) Different provider types support different packaging on different platforms. See TN3134 Network Extension provider deployment for the details. Some providers, most notably packet tunnel providers on macOS, support both appex and sysex packaging. Sysex packaging has a number of advantages: It supports direct distribution, using Developer ID signing. It better matches the networking stack on macOS. An appex is tied to the logged in user, whereas a sysex, and the networking stack itself, is global to the system as a whole. Given that, it generally makes sense to package your Network Extension (NE) provider as a sysex on macOS. If you’re creating a new product that’s fine, but if you have an existing iOS product that you want to bring to macOS, you have to account for the differences brought on by the move to sysex packaging. Similarly, if you have an existing sysex product on macOS that you want to bring to iOS, you have to account for the appex packaging. This post summarises those changes. Keep the following in mind while reading this post: The information here applies to all NE providers that can be packaged as either an appex or a sysex. When this post uses a specific provider type in an example, it’s just an example. Unless otherwise noted, any information about iOS also applies to iPadOS, tvOS, and visionOS. Process Lifecycle With appex packaging, the system typically starts a new process for each instance of your NE provider. For example, with a packet tunnel provider: When the users starts the VPN, the system creates a process and then instantiates and starts the NE provider in that process. When the user stops the VPN, the system stops the NE provider and then terminates the process running it. If the user starts the VPN again, the system creates an entirely new process and instantiates and starts the NE provider in that. In contrast, with sysex packaging there’s typically a single process that runs all off the sysex’s NE providers. Returning to the packet tunnel provider example: When the users starts the VPN, the system instantiates and starts the NE provider in the sysex process. When the user stops the VPN, the system stops and deallocates the NE provider instances, but leaves the sysex process running. If the user starts the VPN again, the system instantiates and starts a new instances of the NE provider in the sysex process. This lifecycle reflects how the system runs the NE provider, which in turn has important consequences on what the NE provider can do: An appex acts like a launchd agent [1], in that it runs in a user context and has access to that user’s state. A sysex is effectively a launchd daemon. It runs in a context that’s global to the system as a whole. It does not have access to any single user’s state. Indeed, there might be no user logged in, or multiple users logged in. The following sections explore some consequences of the NE provider lifecycle. [1] It’s not actually run as a launchd agent. Rather, there’s a system launchd agent that acts as the host for the app extension. App Groups With an app extension, the app extension and its container app run as the same user. Thus it’s trivial to share state between them using an app group container. Note When talking about extensions on Apple platforms, the container app is the app in which the extension is embedded and the host app is the app using the extension. For network extensions the host app is the system itself. That’s not the case with a system extension. The system extension runs as root whereas the container app runs an the user who launched it. While both programs can claim access to the same app group, the app group container location they receive will be different. For the system extension that location will be inside the home directory for the root user. For the container app the location will be inside the home directory of the user who launched it. This does not mean that app groups are useless in a Network Extension app. App groups are also a factor in communicating between the container app and its extensions, the subject of the next section. IMPORTANT App groups have a long and complex history on macOS. For the full story, see App Groups: macOS vs iOS: Working Towards Harmony. Communicating with Extensions With an app extension there are two communication options: App-provider messages App groups App-provider messages are supported by NE directly. In the container app, send a message to the provider by calling sendProviderMessage(_:responseHandler:) method. In the appex, receive that message by overriding the handleAppMessage(_:completionHandler:) method. An appex can also implement inter-process communication (IPC) using various system IPC primitives. Both the container app and the appex claim access to the app group via the com.apple.security.application-groups entitlement. They can then set up IPC using various APIs, as explain in the documentation for that entitlement. With a system extension the story is very different. App-provider messages are supported, but they are rarely used. Rather, most products use XPC for their communication. In the sysex, publish a named XPC endpoint by setting the NEMachServiceName property in its Info.plist. Listen for XPC connections on that endpoint using the XPC API of your choice. Note For more information about the available XPC APIs, see XPC Resources. In the container app, connect to that named XPC endpoint using the XPC Mach service name API. For example, with NSXPCConnection, initialise the connection with init(machServiceName:options:), passing in the string from NEMachServiceName. To maximise security, set the .privileged flag. Note XPC Resources has a link to a post that explains why this flag is important. If the container app is sandboxed — necessary if you ship on the Mac App Store — then the endpoint name must be prefixed by an app group ID that’s accessible to that app, lest the App Sandbox deny the connection. See the app groups documentation for the specifics. When implementing an XPC listener in your sysex, keep in mind that: Your sysex’s named XPC endpoint is registered in the global namespace. Any process on the system can open a connection to it [1]. Your XPC listener must be prepared for this. If you want to restrict connections to just your container app, see XPC Resources for a link to a post that explains how to do that. Even if you restrict access in that way, it’s still possible for multiple instances of your container app to be running simultaneously, each with its own connection to your sysex. This happens, for example, if there are multiple GUI users logged in and different users run your container app. Design your XPC protocol with this in mind. Your sysex only gets one named XPC endpoint, and thus one XPC listener. If your sysex includes multiple NE providers, take that into account when you design your XPC protocol. [1] Assuming that connection isn’t blocked by some other mechanism, like the App Sandbox. Inter-provider Communication A sysex can include multiple types of NE providers. For example, a single sysex might include a content filter and a DNS proxy provider. In that case the system instantiates all of the NE providers in the same sysex process. These instances can communicate without using IPC, for example, by storing shared state in global variables (with suitable locking, of course). It’s also possible for a single container app to contain multiple sysexen, each including a single NE provider. In that case the system instantiates the NE providers in separate processes, one for each sysex. If these providers need to communicate, they have to use IPC. In the appex case, the system instantiates each provider in its own process. If two providers need to communicate, they have to use IPC. Managing Secrets An appex runs in a user context and thus can store secrets, like VPN credentials, in the keychain. On macOS this includes both the data protection keychain and the file-based keychain. It can also use a keychain access group to share secrets with its container app. See Sharing access to keychain items among a collection of apps. Note If you’re not familiar with the different types of keychain available on macOS, see TN3137 On Mac keychain APIs and implementations. A sysex runs in the global context and thus doesn’t have access to user state. It also doesn’t have access to the data protection keychain. It must use the file-based keychain, and specifically the System keychain. That means there’s no good way to share secrets with the container app. Instead, do all your keychain operations in the sysex. If the container app needs to work with a secret, have it pass that request to the sysex via IPC. For example, if the user wants to use a digital identity as a VPN credential, have the container app get the PKCS#12 data and password and then pass that to the sysex so that it can import the digital identity into the keychain. Memory Limits iOS imposes strict memory limits an NE provider appexen [1]. macOS imposes no memory limits on NE provider appexen or sysexen. [1] While these limits are not documented officially, you can get a rough handle on the current limits by reading the posts in this thread. Frameworks If you want to share code between a Mac app and its embedded appex, use a structure like this: MyApp.app/ Contents/ MacOS/ MyApp PlugIns/ MyExtension.appex/ Contents/ MacOS/ MyExtension … Frameworks/ MyFramework.framework/ … There’s one copy of the framework, in the app’s Frameworks directory, and both the app and the appex reference it. This approach works for an appex because the system always loads the appex from your app’s bundle. It does not work for a sysex. When you activate a sysex, the system copies it to a protected location. If that sysex references a framework in its container app, it will fail to start because that framework isn’t copied along with the sysex. The solution is to structure your app like this: MyApp.app/ Contents/ MacOS/ MyApp Library/ SystemExtensions/ MyExtension.systemextension/ Contents/ MacOS/ MyExtension Frameworks/ MyFramework.framework/ … … That is, have both the app and the sysex load the framework from the sysex’s Frameworks directory. When the system copies the sysex to its protected location, it’ll also copy the framework, allowing the sysex to load it. To make this work you have to change the default rpath configuration set up by Xcode. Read Dynamic Library Standard Setup for Apps to learn how that works and then tweak things so that: The framework is embedded in the sysex, not the container app. The container app has an additional LC_RPATH load command for the sysex’s Frameworks directory (@executable_path/../Library/SystemExtensions/MyExtension.systemextension/Contents/Frameworks). The sysex’s LC_RPATH load command doesn’t reference the container app’s Frameworks directory (@executable_path/../../../../Frameworks) but instead points to the sysex’s Framweorks directory (@executable_path/../Frameworks). Entitlements When you build an app with an embedded NE extension, both the app and the extension must be signed with the com.apple.developer.networking.networkextension entitlement. This is a restricted entitlement, that is, it must be authorised by a provisioning profile. The value of this entitlement is an array, and the values in that array differ depend on your distribution channel: If you distribute your app directly with Developer ID signing, use the values with the -systemextension suffix. Otherwise — including when you distribute the app on the App Store and when signing for development — use the values without that suffix. Make sure you authorise these values with your provisioning profile. If, for example, you use an App Store distribution profile with a Developer ID signed app, things won’t work because the profile doesn’t authorise the right values. In general, the easiest option is to use Xcode’s automatic code signing. However, watch out for the pitfall described in Exporting a Developer ID Network Extension. Revision History 2025-11-06 Added the Entitlements section. Explained that, with sysex packaging, multiple instances of your container app might connect simultaneously with your sysex. 2025-09-17 First posted.

I'm looking for help with a network extension filtering issue. Specifically, we have a subclass of NEFilterDataProvider that is used to filter flows based upon a set of rules, including source IP and destination IP. We've run into an issue where the source IP is frequently 0.0.0.0 (or the IPv6 equivalent) on outgoing flows. This has made it so rules based upon source IP don't work. This is also an issue as we report these connections, but we're lacking critical data. We were able to work around the issue somewhat by keeping a list of flows that we allow that we periodically check to see if the source IP is available, and then report after it becomes available. We also considered doing a "peekBytes" to allow a bit of data to flow and then recheck the flow, but we don't want to allow data leakage on connections that should be blocked because of the source IP. Is there a way to force the operating system or network extension frameworks to determine the source IP for an outbound flow without allowing any bytes to flow to the network? STEPS TO REPRODUCE Create a network filtering extension for filtering flows using NEFilterDataProvider See that when handleNewFlow: is called, the outgoing flow lacks the source IP (is 0.0.0.0) in most cases There is this post that is discussing a similar question, though for a slightly different reason. I imagine the answer to this and the other post will be related, at least as far as NEFilterDataProvider:handleNewFlow not having source IP is considered. Thanks!

Hello, I am currently investigating if we can disable usage of QUIC on application level. I know we can set enable_quic from /Library/Preferences/com.apple.networkd.plist to false but it will have a global impact since this is a system file, all the applications on machine will stop using QUIC. I don't want that. What i am looking for is to disable QUIC only for my application. Is there any way i can modify URLSession object in my application and disable QUIC? or modify URLSessionConfiguration so system will not use QUIC?

This issue has cropped up many times here on DevForums. Someone recently opened a DTS tech support incident about it, and I used that as an opportunity to post a definitive response here. If you have questions or comments about this, start a new thread and tag it with Network so that I see it. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" iOS Network Signal Strength The iOS SDK has no general-purpose API that returns Wi-Fi or cellular signal strength in real time. Given that this has been the case for more than 10 years, it’s safe to assume that it’s not an accidental omission but a deliberate design choice. For information about the Wi-Fi APIs that are available on iOS, see TN3111 iOS Wi-Fi API overview. Network performance Most folks who ask about this are trying to use the signal strength to estimate network performance. This is a technique that I specifically recommend against. That’s because it produces both false positives and false negatives: The network signal might be weak and yet your app has excellent connectivity. For example, an iOS device on stage at WWDC might have terrible WWAN and Wi-Fi signal but that doesn’t matter because it’s connected to the Ethernet. The network signal might be strong and yet your app has very poor connectivity. For example, if you’re on a train, Wi-Fi signal might be strong in each carriage but the overall connection to the Internet is poor because it’s provided by a single over-stretched WWAN. The only good way to determine whether connectivity is good is to run a network request and see how it performs. If you’re issuing a lot of requests, use the performance of those requests to build a running estimate of how well the network is doing. Indeed, Apple practices what we preach here: This is exactly how HTTP Live Streaming works. Remember that network performance can change from moment to moment. The user’s train might enter or leave a tunnel, the user might step into a lift, and so on. If you build code to estimate the network performance, make sure it reacts to such changes. Keeping all of the above in mind, iOS 26 beta has two new APIs related to this issue: Network framework now offers a linkQuality property. See this post for my take on how to use this effectively. The WirelessInsights framework can notify you of anticipated WWAN condition changes. But what about this code I found on the ’net? Over the years various folks have used various unsupported techniques to get around this limitation. If you find code on the ’net that, say, uses KVC to read undocumented properties, or grovels through system logs, or walks the view hierarchy of the status bar, don’t use it. Such techniques are unsupported and, assuming they haven’t broken yet, are likely to break in the future. But what about Hotspot Helper? Hotspot Helper does have an API to read Wi-Fi signal strength, namely, the signalStrength property. However, this is not a general-purpose API. Like the rest of Hotspot Helper, this is tied to the specific use case for which it was designed. This value only updates in real time for networks that your hotspot helper is managing, as indicated by the isChosenHelper property. But what about MetricKit? MetricKit is so cool. Amongst other things, it supports the MXCellularConditionMetric payload, which holds a summary of the cellular conditions while your app was running. However, this is not a real-time signal strength value. But what if I’m working for a carrier? This post is about APIs in the iOS SDK. If you’re working for a carrier, discuss your requirements with your carrier’s contact at Apple. Revision History 2025-07-02 Updated to cover new features in the iOS 16 beta. Made other minor editorial changes. 2022-12-01 First posted.

I'm developing a Matter-over-thread generic switch with 2 generic switch endpoints. This is configured as an Intermittently Connected Device with Long Idle Time. I have an Apple TV serving as the thread border router. I'm able to commission the device successfully in the Home app and assign actions to each of the buttons however when the device is rebooted the subscription doesn't appear to resume successfully and the buttons no longer work. I've tested this on various SOC's with their respective SDKs including ESP32-C6, nrf52840 and EFR32MG24 and the behaviour was consistent across all of them. It was working originally when I first started out on the ESP32-C6, then the issue popped up first when I was testing the nrf52840. In that SDK I set persistent subscriptions explicitly and it seemed to resolve the issue until it popped up again when I found that unplugging and restarting the Apple TV completely which appeared to fix the issue with subscriptions not resuming. Recently I've added a Home Pod Mini Gen 2 to the matter fabric so there are now two TBR on the network and restarting both the Apple TV and the HomePod doesn't appear to resolve the issue anymore and the subscriptions are not resuming across all three SOC's on device reboot I'm wondering if there might be something preventing the subscriptions from resuming?

Description I am seeing a consistent crash in a NEDNSProxyProvider on iOS when migrating from completion handlers to the new Swift Concurrency async/await variants of readDatagrams() and writeDatagrams() on NEAppProxyUDPFlow. The crash occurs inside the Swift Concurrency runtime during task resumption. Specifically, it seems the Task attempts to return to the flow’s internal serial executor (NEFlow queue) after a suspension point, but fails if the flow was invalidated or deallocated by the kernel while the task was suspended. Error Signature Thread 4: EXC_BAD_ACCESS (code=1, address=0x28) Thread 4 Queue : NEFlow queue (serial) #0 0x000000018fe919cc in swift::AsyncTask::flagAsAndEnqueueOnExecutor () #9 0x00000001ee25c3b8 in _pthread_wqthread () Steps The crash is highly timing-dependent. To reproduce it reliably: Use an iOS device with Developer Settings enabled. Go to Developer > Network Link Conditioner -> High Latency DNS. Intercept a DNS query and perform a DoH (DNS-over-HTTPS) request using URLSession. The first few network requests should trigger the crash Minimum Working Example (MWE) class DNSProxyProvider: NEDNSProxyProvider { override func handleNewFlow(_ flow: NEAppProxyFlow) -> Bool { guard let udpFlow = flow as? NEAppProxyUDPFlow else { return false } Task(priority: .userInitiated) { await handleUDPFlow(udpFlow) } return true } func handleUDPFlow(_ flow: NEAppProxyUDPFlow) async { do { try await flow.open(withLocalFlowEndpoint: nil) while !Task.isCancelled { // Suspension point 1: Waiting for datagrams let (flowData, error) = await flow.readDatagrams() if let error { throw error } guard let flowData, !flowData.isEmpty else { return } var responses: [(Data, Network.NWEndpoint)] = [] for (data, endpoint) in flowData { // Suspension point 2: External DoH resolution let response = try await resolveViaDoH(data) responses.append((response, endpoint)) } // Suspension point 3: Writing back to the flow // Extension will crash here on task resumption try await flow.writeDatagrams(responses) } } catch { flow.closeReadWithError(error) flow.closeWriteWithError(error) } } private func handleFlowData(_ packet: Data, endpoint: Network.NWEndpoint, using parameters: NWParameters) async throws -> Data { let url = URL(string: "https://dns.google/dns-query")! var request = URLRequest(url: url) request.httpMethod = "POST" request.httpBody = packet request.setValue("application/dns-message", forHTTPHeaderField: "Content-Type") let (data, _) = try await URLSession.shared.data(for: request) return data } } Crash Details & Analysis The disassembly at the crash point indicates a null dereference of an internal executor pointer (Voucher context): ldr x20, [TPIDRRO_EL0 + 0x340] ldr x0, [x20, #0x28] // x20 is NULL/0x0 here, resulting in address 0x28 It appears that NEAppProxyUDPFlow’s async methods bind the Task to a specific internal executor. When the kernel reclaims the flow memory, the pointer in x20 becomes invalid. Because the Swift runtime is unaware that the NEFlow queue executor has vanished, it attempts to resume on non-existing flow and then crashes. Checking !Task.isCancelled does not prevent this, as the crash happens during the transition into the task body before the cancellation check can even run. Questions Is this a known issue of the NetworkExtension async bridge? Why does Task.isCancelled not reflect the deallocation of the underlying NEAppProxyFlow? Is the only safe workaround? Please feel free to correct me if I misunderstood anything here. I'll be happy to hear any insights or suggestions :) Thank you!

We are using the [NEHotspotHelper supportedNetworkInterfaces] to get the Wi-Fi interface in our app, but it occasionally crashes on some devices with the following stack trace: 0 CaptiveNetwork 0x0000000221d87a4c ServerConnectionGetHandlerQueue + 0 (ServerConnection.c:509) 1 CaptiveNetwork 0x0000000221d8577c CNPluginCopySupportedInterfaces + 180 (CNPlugin.c:457) 2 NetworkExtension 0x00000001b0446618 +[NEHotspotHelper supportedNetworkInterfaces] + 32 (NEHotspotHelper.m:563) It seems like the crash is happening on apple's api of supportedNetworkInterfaces. We would like to understand the cause of the crash.

Getting -10985 error from urlSession while attempting to make a connection. Not sure why this is happening if anyone is aware please help

All of our uses of CFSockets have started causing crashes in iOS 16. They seem to be deprecated so we are trying to transition over to using the Network framework and NWConnection to try to fix the crashes. One of our uses of them is to ping a device on the local network to make sure it is there and online and provide a heartbeat status in logs as well as put the application into a disabled state if it is not available as it is critical to the functionality of the app. I know it is discouraged to disable any functionality based on the reachability of a resource but this is in an enterprise environment where the reachability of this device is mission critical. I've seen other people ask about the ability to ping with the Network framework and the answers I've found have said that this is not possible and pointed people to the SimplePing sample code but it turns out our existing ping code is already using this technique and it is crashing just like our other CFSocket usages, inside CFSocketInvalidate with the error BUG IN CLIENT OF LIBPLATFORM: Trying to recursively lock an os_unfair_lock. Is there any updated way to perform a ping without using the CFSocket APIs that now seem to be broken/unsupported on iOS 16?

Hey! We discovered an unexpected side-effect of enabling enforceRoutes in our iOS VPN application - video airplay from iOS to tvOS stopped working (Unable to Connect popup appears instead). Our flags combination is: includeAllNetworks = false enforceRoutes = true excludeLocalNetworks = true Interestingly, music content can be AirPlayed with the same conditions. Also, video AirPlay from iOS device to the macOS works flawlessly. Do you know if this is a known issue? Do you have any advice if we can fix this problem on our side, while keeping enforcRoutes flag enabled?

Hi everyone 👋 As a network engineer and indie iOS developer, I couldn’t find a lightweight mobile tool that fully supports IPv4/IPv6 dual-stack diagnostics — so I built NetToolbox -All-In-One Utility for engineers, DevOps, and developers. Here are its core features that solve real mobile networking pain points: One-Click Full Diagnostics: Integrates ping, traceroute, and multi-type DNS queries (A/AAAA/CNAME) — no need to switch between apps IPv4/IPv6 Dual-Stack Support: Seamlessly works in IPv6-only networks, with the ability to test connectivity differences between dual-stack environments LAN Device Scanning: Quickly identifies all devices on the same network segment and checks port availability Offline Functionality: Diagnostic logic is stored locally, enabling LAN troubleshooting without an internet connection Lightweight Design: 5MB install size, no storage bloat, and low power consumption during operation Dark Mode Support: Tailored for developers who work late at night During development, I leveraged Apple Intelligence alongside Claude Code and Gemini 3 to accelerate the process, optimize iOS native networking stack adaptation and local storage logic, and significantly boost development efficiency. I’d love to hear from the community: What must-have features are missing from mobile network diagnostic tools? Do you have experience optimizing iOS workflows with Apple Intelligence? 👉 You can try the app here: https://apps.apple.com/us/app/nettoolbox-all-in-one-utility/id6757392404 Feedback is highly appreciated — I’ll keep iterating to make it better! 🚀

We have a macOS system extension with NETransparentProxyProvider which is able to intercept traffic and handle it. We also wanted to setup few search domains from our network extension. However, unlike PacketTunnelProvider, NEDNSSettings are completely ignored with NETransparentProxyProvider. So whats the best way to setup few DNS search domains when using NETransparentProxyProvider.

IMPORTANT The resume rate limiter is now covered by the official documentation. See Use background sessions efficiently within Downloading files in the background. So, the following is here purely for historical perspective. NSURLSession’s background session support on iOS includes a resume rate limiter. This limiter exists to prevent apps from abusing the background session support in order to run continuously in the background. It works as follows: nsurlsessiond (the daemon that does all the background session work) maintains a delay value for your app. It doubles that delay every time it resumes (or relaunches) your app. It resets that delay to 0 when the user brings your app to the front. It also resets the delay to 0 if the delay period elapses without it having resumed your app. When your app creates a new task while it is in the background, the task does not start until that delay has expired. To understand the impact of this, consider what happens when you download 10 resources. If you pass them to the background session all at once, you see something like this: Your app creates tasks 1 through 10 in the background session. nsurlsessiond starts working on the first few tasks. As tasks complete, nsurlsessiond starts working on subsequent ones. Eventually all the tasks complete and nsurlsessiond resumes your app. Now consider what happens if you only schedule one task at a time: Your app creates task 1. nsurlsessiond starts working on it. When it completes, nsurlsessiond resumes your app. Your app creates task 2. nsurlsessiond delays the start of task 2 a little bit. nsurlsessiond starts working on task 2. When it completes, nsurlsessiond resumes your app. Your app creates task 3. nsurlsessiond delays the start of task 3 by double the previous amount. nsurlsessiond starts working on task 3. When it completes, nsurlsessiond resumes your app. Steps 8 through 11 repeat, and each time the delay doubles. Eventually the delay gets so large that it looks like your app has stopped making progress. If you have a lot of tasks to run then you can mitigate this problem by starting tasks in batches. That is, rather than start just one task in step 1, you would start 100. This only helps up to a point. If you have thousands of tasks to run, you will eventually start seeing serious delays. In that case it’s much better to change your design to use fewer, larger transfers. Note All of the above applies to iOS 8 and later. Things worked differently in iOS 7. There’s a post on DevForums that explains the older approach. Finally, keep in mind that there may be other reasons for your task not starting. Specifically, if the task is flagged as discretionary (because you set the discretionary flag when creating the task’s session or because the task was started while your app was in the background), the task may be delayed for other reasons (low power, lack of Wi-Fi, and so on). Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" (r. 22323366)

Summary I'm implementing NEURLFilter with the com.apple.developer.networking.networkextension.url-filter-provider entitlement for a system-wide URL filtering feature. The feature works perfectly in development-signed builds (connecting successfully to my PIR server over extended testing) but every production-signed build fails before any network call is made. NEURLFilterManager reports .serverSetupIncomplete (code 9). After installing the NetworkExtension debug profile, the unredacted com.apple.CipherML logs reveal the cause: no privacy proxy is provisioned for this bundle identifier, and the connection is configured proxy fail closed. Environment iOS 26 Entitlement: com.apple.developer.networking.networkextension.url-filter-provider Extension point: com.apple.networkextension.url-filter-control PIR server configured via NEURLFilterManager.setConfiguration(...) Privacy Pass issuer configured Dev-signed builds: working correctly, connecting to the PIR server Production-signed builds (both TestFlight and distribution): failing identically The Error Chain Surfaced to the app via NEURLFilterManager.lastDisconnectError: NEURLFilterManager.Error.serverSetupIncomplete (code 9) ← NEAgentURLFilterErrorDomain Code 3 ← com.apple.CipherML Code 1100 "Unable to query status" ← com.apple.CipherML Code 1800 (error details were logged and redacted) After installing the VPN (NetworkExtension) debug profile, the unredacted com.apple.CipherML subsystem shows: queryStatus(for:options:) threw an error: Error Domain=NSURLErrorDomain Code=-1009 "The Internet connection appears to be offline." UserInfo={ _NSURLErrorNWPathKey = satisfied (Path is satisfied), interface: en0[802.11], ipv4, dns, uses wifi, LQM: good, NSErrorFailingURLKey = https://<my-pir-server>/config, NSUnderlyingError = { Error Domain=NSPOSIXErrorDomain Code=50 "Network is down" }, _NSURLErrorPrivacyProxyFailureKey = true, NSLocalizedDescription = "The Internet connection appears to be offline." } The critical diagnostic line in the com.apple.network subsystem is: nw_endpoint_proxy_handler_should_use_proxy Proxies not present, but required to fail closed And the connection setup shows the proxy fail closed flag is mandatory for the connection: [C... ... Hostname#...:443 quic, bundle id: <my-bundle-id>, attribution: developer, using ephemeral configuration, context: NWURLSession (sensitive), proxy fail closed] start The network path itself is healthy (Wi-Fi good, DNS resolves correctly), but the connection is explicitly configured to fail closed if no proxy is present, and no proxy is provisioned for this bundle identifier. The entire failure happens in approximately 18 ms, far too fast for any network round-trip, confirming no traffic ever leaves the device. What I've Verified The entitlement is present in the distribution build The NEURLFilterControlProvider extension loads and returns a valid Bloom filter prefilter (with a tag that round-trips correctly between extension and framework) NEURLFilterManager.setConfiguration(pirServerURL:pirPrivacyPassIssuerURL:pirAuthenticationToken:controlProviderBundleIdentifier:) accepts all four parameters without error Development-signed builds of the same bundle identifier connect successfully to the same PIR server On production-signed builds, zero requests reach the PIR server — failure is purely client-side, before any network activity The Question How does the OHTTP privacy proxy get provisioned for a bundle identifier so that production builds can successfully use NEURLFilter? Specifically: Is there a Capability Request form I need to submit for url-filter-provider? I cannot find one in the Capability Requests section of my developer portal. Should I be running my own OHTTP gateway (for example using swift-nio-oblivious-http), and if so, does Apple then need to provision routing from their OHTTP relay to my gateway URL? Is the OHTTP relay path meant to be automatic once the entitlement is active, and if so, is there a specific activation step I'm missing? Is there any way to verify the current provisioning state for a specific bundle identifier from the developer portal? I can provide the full sysdiagnose and unredacted bundle/server details privately to an Apple engineer if that would help diagnose. I'd prefer to keep them out of a public post. Thanks!

I'm using NWBrowser to search for a server that I hosted. The browser does find my service but when it tries to connect to it, it gets stuck in the preparing phase in NWConnection.stateUpdateHandler. When I hardcode the local IP address of my computer (where the server is hosted) into NWConnection it works perfectly fine and is able to connect. When it gets stuck in the preparing phase, it gives me the warnings and error messages in the image below. You can also see that the service name is correct and it is found. I have tried _http._tcp and _ssh._tcp types and neither work. This is what my code looks like: func findServerAndConnect(port: UInt16) { print("Searching for server...") let browser = NWBrowser(for: .bonjour(type: "_ssh._tcp", domain: "local."), using: .tcp) browser.browseResultsChangedHandler = { results, _ in print("Found results: \(results)") for result in results { if case let NWEndpoint.service(name, type_, domain, interface) = result.endpoint { if name == "PocketPadServer" { print("Found service: \(name) of type \(type_) in domain \(domain) on interface \(interface)") // Construct the full service name, including type and domain let fullServiceName = "\(name).\(type_).\(domain)" print("Full service name: \(fullServiceName), \(result.endpoint)") self.connect(to: result.endpoint, port: port) browser.cancel() break } } } } browser.start(queue: .main) } func connect(to endpoint: NWEndpoint, port: UInt16) { print("Connecting to \(endpoint) on port \(port)...") // endpoint = NWEndpoint( let tcpParams = NWProtocolTCP.Options() tcpParams.enableFastOpen = true tcpParams.keepaliveIdle = 2 let params = NWParameters(tls: nil, tcp: tcpParams) params.includePeerToPeer = true // connection = NWConnection(host: NWEndpoint.Host("xx.xxx.xxx.xxx"), port: NWEndpoint.Port(3000), using: params) connection = NWConnection(to: endpoint, using: params) connection?.pathUpdateHandler = { path in print("Connection path update: \(path)") if path.status == .satisfied { print("Connection path is satisfied") } else { print("Connection path is not satisfied: \(path.status)") } } connection?.stateUpdateHandler = { newState in DispatchQueue.main.async { switch newState { case .ready: print("Connected to server") self.pairing = true self.receiveMessage() case .failed(let error): print("Connection failed: \(error)") self.isConnected = false case .waiting(let error): print("Waiting for connection... \(error)") self.isConnected = false case .cancelled: print("Connection cancelled") self.isConnected = false case .preparing: print("Preparing connection...") self.isConnected = false default: print("Connection state changed: \(newState)") break } } } connection?.start(queue: .main) }

Hi Apple Team / Community, We are currently pulling our hair out over a TestNet OTA issue and could really use some help. Our Matter Door Lock (VID: 5424, PID: 513) has already obtained official CSA Certification, so we are 100% confident that our device firmware and OTA Requestor logic are completely solid. However, we simply cannot get Apple's TestNet to serve the update via HomePod. Here is exactly what is happening: Our device successfully sends a QueryImage command to the HomePod. The HomePod receives it, but immediately fires back a QueryImageResponse that essentially means "UpdateNotAvailable", forcing the device into an 86400-second sleep timeout. Here is what we have verified so far: Local OTA works perfectly: If we use Nordic's chip-ota-provider-app locally with the exact same .ota file, the BDX transfer triggers instantly and the device updates without a hitch. DCL details are 100% accurate: We published a brand new version (1.0.4 / 16778240) which is strictly higher than the device's current version (1.0.1 / 16777472). The otaFileSize (973839) and Base64 Checksum match the file perfectly. ZERO hits on our server: The OTA file is hosted on an AWS S3 direct link (SSL Grade A via SSL Labs, ATS compliant). We checked our server logs, and there hasn't been a single download attempt from any Apple IP addresses. Since our device is certified and local OTA works flawlessly, it strongly feels like Apple's TestNet backend either has a stuck/cached "invalid" state for our VID/PID (very similar to what was reported in CHIP GitHub Issue #29338), or the Apple backend crawler is failing to reach our URL for some internal reason. Could someone please check if there is a cached exception for VID: 5424 / PID: 513 on the TestNet backend? Any help or pointers would be hugely appreciated! Thanks in advance.

My team is developing an enterprise VPN application that needs to respond to Mobile Device Management (MDM) profile installations and removals in real-time. Our app uses the NetworkExtension framework and needs to update the UI immediately when VPN configurations are added or removed via MDM. We are currently observing NEVPNConfigurationChangeNotification to detect VPN configuration changes: While NEVPNConfigurationChangeNotification fires reliably when users manually remove VPN profiles through Settings > General > VPN & Device Management, it appears to have inconsistent behavior when MDM profiles containing VPN configurations are installed programmatically via MDM systems. STEPS TO REPRODUCE From MDM Admin Console: Deploy a new VPN profile to the test device On Device: Wait for MDM profile installation (usually silent, no user interaction required) Check Device Settings: Go to Settings > General > VPN & Device Management to confirm profile is installed Return to App: Check if the UI shows the new VPN profile

Have you ever encountered the issue where the Wi-Fi MAC address information can no longer be retrieved after I updated to iOS 26?