在Mac OS X上以编程方式查找DNS服务器设置

Question

我有一些跨平台的DNS客户端代码，我用来做端到端的SMTP，在windows上，我可以通过在注册表中查找当前的DNS服务器ip地址。在Mac上，我可能可以使用第一个答案中提到的SystemConfiguration框架，但是具体的方法还不是很明显。

例如，SCDynamicStoreCopyDHCPInfo会返回一些动态DHCP相关数据，但不会返回DNS服务器地址。

Answer 1

也可以从/etc/resolv.conf获取它们

Answer 2

我知道你已经很久没有需要这个了，但是没有什么比一个老的未解决的答案更糟糕的了。由于权限问题，您无法从"/etc/resolv.conf“访问它们。经过多次搜索，幸运的是，我发现可以通过res_ninit()函数获得它。

// Get native iOS System Resolvers
res_ninit(&_res);
res_state res = &_res;

for (int i = 0; i < res->nscount; i++) {
  sa_family_t family = res->nsaddr_list[i].sin_family;
  int port = ntohs(res->nsaddr_list[i].sin_port);
  if (family == AF_INET) { // IPV4 address
    char str[INET_ADDRSTRLEN]; // String representation of address
    inet_ntop(AF_INET, & (res->nsaddr_list[i].sin_addr.s_addr), str, INET_ADDRSTRLEN);
  } else if (family == AF_INET6) { // IPV6 address
    char str[INET6_ADDRSTRLEN]; // String representation of address
    inet_ntop(AF_INET6, &(res->nsaddr_list [i].sin_addr.s_addr), str, INET6_ADDRSTRLEN);
  }
}
res_ndestroy(res);

Answer 3

我知道现在回答这个问题已经很晚了，但对其他人可能会有所帮助。

此代码将有助于完成此任务。

SCPreferencesRef prefsDNS = SCPreferencesCreate(NULL, CFSTR("DNSSETTING"), NULL);
CFArrayRef services = SCNetworkServiceCopyAll(prefsDNS);
long servicesCount = CFArrayGetCount(services);
for (long i = 0; i < servicesCount; i++) {
    const SCNetworkServiceRef service = (const SCNetworkServiceRef)CFArrayGetValueAtIndex(services, i);
    CFStringRef interfaceServiceID = SCNetworkServiceGetServiceID(service);
    CFStringRef primaryservicepath = CFStringCreateWithFormat(NULL,NULL,CFSTR("State:/Network/Service/%@/DNS"),interfaceServiceID);
    SCDynamicStoreRef dynRef = SCDynamicStoreCreate(kCFAllocatorSystemDefault, CFSTR("DNSSETTING"), NULL, NULL);
    CFPropertyListRef propList = SCDynamicStoreCopyValue(dynRef,primaryservicepath);
    if (propList) {
        CFDictionaryRef dict = (CFDictionaryRef)propList;
        CFArrayRef addresses = (CFArrayRef)CFDictionaryGetValue(dict, CFSTR("ServerAddresses"));
        long addressesCount = CFArrayGetCount(addresses);
        for (long j = 0; j < addressesCount; j++) {
            CFStringRef address = (CFStringRef)CFArrayGetValueAtIndex(addresses, j);
            // Print address
            CFShow(address);
        }
        CFRelease(propList);
    }
    CFRelease(dynRef);
    CFRelease(primaryservicepath);
}
CFRelease(services);
CFRelease(prefsDNS);