iOS触发本地网络权限弹框

自iOS14之后增加的本地网络权限的弹框.
info.plist键中添加

Privacy - Local Network Usage Description

而触发需要本地网络的流量产生才可以。
根据官网解释：

Currently there is no way to explicitly trigger the local network privacy alert (r. 69157424). However, you can bring it up implicitly by sending dummy traffic to a local network address. The code below shows one way to do this. It finds all IPv4 and IPv6 addresses associated with broadcast-capable network interfaces and sends a UDP datagram to each one. This should trigger the local network privacy alert, assuming the alert hasn’t already been displayed for your app.
目前没有办法明确触发本地网络隐私警报（r.69157424）。但是，您可以通过向本地网络地址发送虚拟流量来隐式地调出它。下面的代码展示了一种方法。它查找与支持广播的网络接口相关联的所有IPv4和IPv6地址，并向每个地址发送UDP数据报。假设您的应用程序尚未显示警报，这应该会触发本地网络隐私警报。

根据官方资料，总结了Swift&OC两种触发代码

Swift：

import Foundation
/// Does a best effort attempt to trigger the local network privacy alert.
///
/// It works by sending a UDP datagram to the discard service (port 9) of every
/// IP address associated with a broadcast-capable interface. This should
/// trigger the local network privacy alert, assuming the alert hasn’t already
/// been displayed for this app.
///
/// This code takes a ‘best effort’. It handles errors by ignoring them. As
/// such, there’s guarantee that it’ll actually trigger the alert.
///
/// - note: iOS devices don’t actually run the discard service. I’m using it
/// here because I need a port to send the UDP datagram to and port 9 is
/// always going to be safe (either the discard service is running, in which
/// case it will discard the datagram, or it’s not, in which case the TCP/IP
/// stack will discard it).
///
/// There should be a proper API for this (r. 69157424).
///
/// For more background on this, see [Triggering the Local Network Privacy Alert](https://developer.apple.com/forums/thread/663768).
func triggerLocalNetworkPrivacyAlert() {
    let sock4 = socket(AF_INET, SOCK_DGRAM, 0)
    guard sock4 >= 0 else { return }
    defer { close(sock4) }
    let sock6 = socket(AF_INET6, SOCK_DGRAM, 0)
    guard sock6 >= 0 else { return }
    defer { close(sock6) }
    
    let addresses = addressesOfDiscardServiceOnBroadcastCapableInterfaces()
    var message = [UInt8]("!".utf8)
    for address in addresses {
        address.withUnsafeBytes { buf in
            let sa = buf.baseAddress!.assumingMemoryBound(to: sockaddr.self)
            let saLen = socklen_t(buf.count)
            let sock = sa.pointee.sa_family == AF_INET ? sock4 : sock6
            _ = sendto(sock, &message, message.count, MSG_DONTWAIT, sa, saLen)
        }
    }
}
/// Returns the addresses of the discard service (port 9) on every
/// broadcast-capable interface.
///
/// Each array entry is contains either a `sockaddr_in` or `sockaddr_in6`.
private func addressesOfDiscardServiceOnBroadcastCapableInterfaces() -> [Data] {
    var addrList: UnsafeMutablePointer<ifaddrs>? = nil
    let err = getifaddrs(&addrList)
    guard err == 0, let start = addrList else { return [] }
    defer { freeifaddrs(start) }
    return sequence(first: start, next: { $0.pointee.ifa_next })
        .compactMap { i -> Data? in
            guard
                (i.pointee.ifa_flags & UInt32(bitPattern: IFF_BROADCAST)) != 0,
                let sa = i.pointee.ifa_addr
            else { return nil }
            var result = Data(UnsafeRawBufferPointer(start: sa, count: Int(sa.pointee.sa_len)))
            switch CInt(sa.pointee.sa_family) {
            case AF_INET:
                result.withUnsafeMutableBytes { buf in
                    let sin = buf.baseAddress!.assumingMemoryBound(to: sockaddr_in.self)
                    sin.pointee.sin_port = UInt16(9).bigEndian
                }
            case AF_INET6:
                result.withUnsafeMutableBytes { buf in
                    let sin6 = buf.baseAddress!.assumingMemoryBound(to: sockaddr_in6.self)
                    sin6.pointee.sin6_port = UInt16(9).bigEndian
                }
            default:
                return nil
            }
            return result
        }
}

OC:

#include <ifaddrs.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
/// Returns the addresses of the discard service (port 9) on every
/// broadcast-capable interface.
///
/// Each array entry contains either a `sockaddr_in` or `sockaddr_in6`.
static NSArray<NSData *> * addressesOfDiscardServiceOnBroadcastCapableInterfaces(void) {
    struct ifaddrs * addrList = NULL;
    int err = getifaddrs(&addrList);
    if (err != 0) {
        return @[];
    }
    NSMutableArray<NSData *> * result = [NSMutableArray array];
    for (struct ifaddrs * cursor = addrList; cursor != NULL; cursor = cursor->ifa_next) {
        if ( (cursor->ifa_flags & IFF_BROADCAST) &&
             (cursor->ifa_addr != NULL)
           ) {
            switch (cursor->ifa_addr->sa_family) {
            case AF_INET: {
                struct sockaddr_in sin = *(struct sockaddr_in *) cursor->ifa_addr;
                sin.sin_port = htons(9);
                NSData * addr = [NSData dataWithBytes:&sin length:sizeof(sin)];
                [result addObject:addr];
            } break;
            case AF_INET6: {
                struct sockaddr_in6 sin6 = *(struct sockaddr_in6 *) cursor->ifa_addr;
                sin6.sin6_port = htons(9);
                NSData * addr = [NSData dataWithBytes:&sin6 length:sizeof(sin6)];
                [result addObject:addr];
            } break;
            default: {
                // do nothing
            } break;
            }
        }
    }
    freeifaddrs(addrList);
    return result;
}
/// Does a best effort attempt to trigger the local network privacy alert.
///
/// It works by sending a UDP datagram to the discard service (port 9) of every
/// IP address associated with a broadcast-capable interface interface. This
/// should trigger the local network privacy alert, assuming the alert hasn’t
/// already been displayed for this app.
///
/// This code takes a ‘best effort’. It handles errors by ignoring them. As
/// such, there’s guarantee that it’ll actually trigger the alert.
///
/// - note: iOS devices don’t actually run the discard service. I’m using it
/// here because I need a port to send the UDP datagram to and port 9 is
/// always going to be safe (either the discard service is running, in which
/// case it will discard the datagram, or it’s not, in which case the TCP/IP
/// stack will discard it).
///
/// There should be a proper API for this (r. 69157424).
///
/// For more background on this, see [Triggering the Local Network Privacy Alert](https://developer.apple.com/forums/thread/663768).
extern void triggerLocalNetworkPrivacyAlertObjC(void) {
    int sock4 = socket(AF_INET, SOCK_DGRAM, 0);
    int sock6 = socket(AF_INET6, SOCK_DGRAM, 0);
    
    if ((sock4 >= 0) && (sock6 >= 0)) {
        char message = '!';
        NSArray<NSData *> * addresses = addressesOfDiscardServiceOnBroadcastCapableInterfaces();
        for (NSData * address in addresses) {
            int sock = ((const struct sockaddr *) address.bytes)->sa_family == AF_INET ? sock4 : sock6;
            (void) sendto(sock, &message, sizeof(message), MSG_DONTWAIT, address.bytes, (socklen_t) address.length);
        }
    }
    
    // If we failed to open a socket, the descriptor will be -1 and it’s safe to
    // close that (it’s guaranteed to fail with `EBADF`).
    close(sock4);
    close(sock6);
}

附:官方本地网络隐私常见问题

• FAQ-1 什么是本地网络？

• FAQ-2 哪些操作需要本地网络访问？

• FAQ-3 哪些操作需要多播授权？

• FAQ-4 我需要多播授权吗？

• FAQ-5 我已被授予多播授权；我如何启用它？

• FAQ-6 App Clips可以访问本地网络吗？

• FAQ-7 本地网络隐私如何与应用程序扩展配合使用？

• FAQ-8 如何明确触发本地网络隐私警报？

• FAQ-9 我如何判断我是否获得了本地网络访问权限？

• FAQ-10 我如何使用不满意的原因属性？

• FAQ-11 我需要本地网络使用说明属性吗？

• FAQ-12 我可以在模拟器上测试吗？

• FAQ-13 一旦我的应用程序显示本地网络隐私警报，我如何重置其状态以便它再次显示？

• FAQ-14 如何将我的多点连接服务类型映射到Bonjour服务属性中的条目？

• FAQ-15我的应用程序意外地显示本地网络隐私警报。有办法找到原因吗？