IMPORTANT If you haven’t yet read Calling BSD Sockets from Swift, do that first.
Sometimes you need to get information about the local network interfaces on the device. All Apple platforms support the getifaddrs routine, which returns the list of network interfaces and their addresses. However, it works in terms of struct sockaddr values, which are hard to use from Swift. Here’s an example of how you might use the QSockAddr primitives to return strings instead:
extension QSockAddr {
/// Returns a list of interfaces that have an associated IPv4 or IPv6
/// address.
///
/// Equivalent to the `getifaddrs` BSD Sockets call.
///
/// The list is in the same order as that returned by `getifaddrs`.
/// ```
public static func interfaceNamesAndAddresses() -> [(name: String, address: String)] {
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 [] }
defer { freeifaddrs(addrList) }
return sequence(first: first, next: { $0.pointee.ifa_next })
.compactMap { addr in
guard
let name = addr.pointee.ifa_name,
let sa = addr.pointee.ifa_addr,
[AF_INET, AF_INET6].contains(CInt(sa.pointee.sa_family)),
let (address, _) = try? QSockAddr.fromSockAddr(sa: sa, saLen: socklen_t(sa.pointee.sa_len))
else { return nil }
return (String(cString: name), address)
}
}
}
And once you have this primitive, you can add wrappers to get just the names, just the addresses, or the addresses grouped by the interface:
extension QSockAddr {
public static func interfaceNames() -> [String] {
interfaceNamesAndAddresses()
.map { $0.name }
}
public static func interfaceAddresses() -> [String] {
interfaceNamesAndAddresses()
.map { $0.address }
}
public static func addressesByInterface() -> [String: [String]] {
interfaceNamesAndAddresses()
.reduce(into: [:]) { soFar, i in
soFar[i.name, default: []].append(i.address)
}
}
}
Note If you’re targeting macOS you have a lot more options in this space. Most notably, System Configuration framework has a dynamic store API that returns detailed information about the Mac’s network state.
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
