screen_cast/ios/Receiver/Support/LocalAddress.swift

import Foundation
#if canImport(Darwin)
import Darwin
#endif

/// Finds the primary IPv4 address (e.g. on Wi-Fi) for the status overlay and
/// the `--peer` hint. Best-effort; the sender reaches us by IP over the LAN.
enum LocalAddress {
    static func primaryIPv4() -> String {
        var result = "unknown"
        var fallback = "unknown"
        var ptr: UnsafeMutablePointer<ifaddrs>?
        guard getifaddrs(&ptr) == 0 else { return result }
        defer { freeifaddrs(ptr) }

        var current = ptr
        while let iface = current {
            let next = iface.pointee.ifa_next
            current = next

            guard let sa = iface.pointee.ifa_addr else { continue }
            guard sa.pointee.sa_family == sa_family_t(AF_INET) else { continue }
            if Int32(iface.pointee.ifa_flags) & IFF_LOOPBACK == 0 {
                let inaddr = sa.assumingMemoryBound(to: sockaddr_in.self).pointee
                var host = [CChar](repeating: 0, count: Int(INET_ADDRSTRLEN))
                if inet_ntop(AF_INET, &inaddr.sin_addr, &host, socklen_t(INET_ADDRSTRLEN)) != nil {
                    let ip = String(cString: host)
                    if ip.hasPrefix("169.254") {
                        continue // link-local; prefer a routable address
                    }
                    fallback = ip
                    let name = String(cString: iface.pointee.ifa_name)
                    if name.hasPrefix("en") || name.hasPrefix("wlan") {
                        return ip // Wi-Fi / Ethernet: good enough for the hint
                    }
                }
            }
        }
        return fallback
    }
}