NetworkInterfaceInfo

Basically a Swift abstraction over getifaddrs; a way to enumerate all the network interfaces on the current host, with their core information such as associated addresses & netmasks.

This is intentionally very lightweight, and designed to be very efficient even for cases where you're looking for a small subset of interfaces. e.g. to find all active IPv4 addresses (excluding loopback networks):

import NetworkInterfaceInfo

try NetworkInterface.all
    .filter { $0.up             // Only active network interfaces…
              && !$0.loopback } // Ignoring loopback interfaces…
    .compactMap(\.address)      // That have addresses and…
    .filter(\.isIPv4)           // Use IPv4.

On macOS only, interface metrics are also available - both configuration values such as MTU and line speed, as well as counters such as bytes & packets sent & received.

See the documentation for more details.

Change monitoring

There is also a second module which allows you to monitor for changes to network interfaces, as shown in the example below.

Note: this additional module is currently only implemented for platforms that have Apple's Network package available (i.e. Apple's platforms, not Linux or Windows).

import NetworkInterfaceInfo
import NetworkInterfaceChangeMonitoring

for try await change in NetworkInterface.changes() {
    switch change.nature {
    case .added:
        print("New network interface: \(change.interface)")
    case .modified(let modificationNature):
        if modificationNature.contains(.address) {
            print("Address changed to \(change.interface.address).")
        }
    case .removed:
        // etc
    }
}

Note: you still need to explicitly import NetworkInterfaceInfo in order to access the changes method and otherwise use NetworkInterface et al.

This monitoring functionality is in a separate module so that you don't pay the cost of it if you don't need it.

Important: monitoring for network interface changes relies on Apple's NWPathMonitor class. Generally that notices changes virtually immediately, but sometimes it is delayed - up to minute(s) later. This might be worked around in a future version of this library, but for now at least be aware of that annoying uncertainty and consider taking steps to work around it (e.g. polling NetworkInterface.all instead, if you need a clear latency upper bound).