//
//  PacketTunnelProvider+FileDescriptor.swift
//  YggdrasilNetworkExtension
//
//  Created by Neil on 06/06/2023.
//

import Foundation

extension PacketTunnelProvider {
    
    // SPDX-License-Identifier: MIT
    // Copyright © 2018-2023 WireGuard LLC. All Rights Reserved.
    // Original source location: https://github.com/WireGuard/wireguard-apple/blob/2fec12a6e1f6e3460b6ee483aa00ad29cddadab1/Sources/WireGuardKit/WireGuardAdapter.swift#L60-L90
    internal var tunnelFileDescriptor: Int32? {
        var ctlInfo = ctl_info()
        withUnsafeMutablePointer(to: &ctlInfo.ctl_name) {
            $0.withMemoryRebound(to: CChar.self, capacity: MemoryLayout.size(ofValue: $0.pointee)) {
                _ = strcpy($0, "com.apple.net.utun_control")
            }
        }
        for fd: Int32 in 0...1024 {
            var addr = sockaddr_ctl()
            var ret: Int32 = -1
            var len = socklen_t(MemoryLayout.size(ofValue: addr))
            withUnsafeMutablePointer(to: &addr) {
                $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                    ret = getpeername(fd, $0, &len)
                }
            }
            if ret != 0 || addr.sc_family != AF_SYSTEM {
                continue
            }
            if ctlInfo.ctl_id == 0 {
                ret = ioctl(fd, CTLIOCGINFO, &ctlInfo)
                if ret != 0 {
                    continue
                }
            }
            if addr.sc_id == ctlInfo.ctl_id {
                return fd
            }
        }
        return nil
    }
    
}