How can I get a real IP address from DNS query in Swift?
Your code retrieves the address as a "socket address" structure. getnameinfo() can be used to convert the address into a numerical IP string
(code recycled from https://stackoverflow.com/a/25627545/1187415,
now updated to Swift 2):
let host = CFHostCreateWithName(nil,"www.google.com").takeRetainedValue()
CFHostStartInfoResolution(host, .Addresses, nil)
var success: DarwinBoolean = false
if let addresses = CFHostGetAddressing(host, &success)?.takeUnretainedValue() as NSArray?,
let theAddress = addresses.firstObject as? NSData {
var hostname = [CChar](count: Int(NI_MAXHOST), repeatedValue: 0)
if getnameinfo(UnsafePointer(theAddress.bytes), socklen_t(theAddress.length),
&hostname, socklen_t(hostname.count), nil, 0, NI_NUMERICHOST) == 0 {
if let numAddress = String.fromCString(hostname) {
print(numAddress)
}
}
}
Output (example): 173.194.112.147
Note also the usage of takeRetainedValue() in the first line, because CFHostCreateWithName() has "Create" in its name the therefore returns a (+1) retained
object.
Update for Swift 3/Xcode 8:
let host = CFHostCreateWithName(nil,"www.google.com" as CFString).takeRetainedValue()
CFHostStartInfoResolution(host, .addresses, nil)
var success: DarwinBoolean = false
if let addresses = CFHostGetAddressing(host, &success)?.takeUnretainedValue() as NSArray?,
let theAddress = addresses.firstObject as? NSData {
var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
if getnameinfo(theAddress.bytes.assumingMemoryBound(to: sockaddr.self), socklen_t(theAddress.length),
&hostname, socklen_t(hostname.count), nil, 0, NI_NUMERICHOST) == 0 {
let numAddress = String(cString: hostname)
print(numAddress)
}
}
Or, to get all IP addresses for the host:
let host = CFHostCreateWithName(nil,"www.google.com" as CFString).takeRetainedValue()
CFHostStartInfoResolution(host, .addresses, nil)
var success: DarwinBoolean = false
if let addresses = CFHostGetAddressing(host, &success)?.takeUnretainedValue() as NSArray? {
for case let theAddress as NSData in addresses {
var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
if getnameinfo(theAddress.bytes.assumingMemoryBound(to: sockaddr.self), socklen_t(theAddress.length),
&hostname, socklen_t(hostname.count), nil, 0, NI_NUMERICHOST) == 0 {
let numAddress = String(cString: hostname)
print(numAddress)
}
}
}
How to perform DNS query on iOS
Figured out a change in this snippet makes it working
if (result == TRUE) {
NSMutableArray *tempDNS = [[NSMutableArray alloc] init];
for(int i = 0; i < CFArrayGetCount(addresses); i++){
struct sockaddr_in* remoteAddr;
CFDataRef saData = (CFDataRef)CFArrayGetValueAtIndex(addresses, i);
remoteAddr = (struct sockaddr_in*)CFDataGetBytePtr(saData);
if(remoteAddr != NULL){
// Extract the ip address
//const char *strIP41 = inet_ntoa(remoteAddr->sin_addr);
NSString *strDNS =[NSString stringWithCString:inet_ntoa(remoteAddr->sin_addr) encoding:NSASCIIStringEncoding];
NSLog(@"RESOLVED %d:<%@>", i, strDNS);
[tempDNS addObject:strDNS];
}
}
}
Swift - Get device's WIFI IP Address
According to several SO threads (e.g. What exactly means iOS networking interface name? what's pdp_ip ? what's ap?), the WiFi interface on an iOS device always has then name "en0".
Your code (which seems to be what I answered at How to get Ip address in swift :) retrieves a list of the IP addresses of all running network interfaces. It can easily be modified to return only the IP address
of the "en0" interface, and actually that is what I originally had
answered at that thread (and this is just a Swift translation of the
answer to how to get ip address of iphone programmatically):
// Return IP address of WiFi interface (en0) as a String, or `nil`
func getWiFiAddress() -> String? {
var address : String?
// Get list of all interfaces on the local machine:
var ifaddr : UnsafeMutablePointer<ifaddrs> = nil
if getifaddrs(&ifaddr) == 0 {
// For each interface ...
var ptr = ifaddr
while ptr != nil {
defer { ptr = ptr.memory.ifa_next }
let interface = ptr.memory
// Check for IPv4 or IPv6 interface:
let addrFamily = interface.ifa_addr.memory.sa_family
if addrFamily == UInt8(AF_INET) || addrFamily == UInt8(AF_INET6) {
// Check interface name:
if let name = String.fromCString(interface.ifa_name) where name == "en0" {
// Convert interface address to a human readable string:
var hostname = [CChar](count: Int(NI_MAXHOST), repeatedValue: 0)
getnameinfo(interface.ifa_addr, socklen_t(interface.ifa_addr.memory.sa_len),
&hostname, socklen_t(hostname.count),
nil, socklen_t(0), NI_NUMERICHOST)
address = String.fromCString(hostname)
}
}
}
freeifaddrs(ifaddr)
}
return address
}
Usage:
if let addr = getWiFiAddress() {
print(addr)
} else {
print("No WiFi address")
}
Update for Swift 3: In addition to adopting the code to the
many changes in Swift 3,
iterating over all interfaces can now use the new generalizedsequence() function:
Do NOT forget to add #include <ifaddrs.h> in your bridging header
// Return IP address of WiFi interface (en0) as a String, or `nil`
func getWiFiAddress() -> String? {
var address : String?
// Get list of all interfaces on the local machine:
var ifaddr : UnsafeMutablePointer<ifaddrs>?
guard getifaddrs(&ifaddr) == 0 else { return nil }
guard let firstAddr = ifaddr else { return nil }
// For each interface ...
for ifptr in sequence(first: firstAddr, next: { $0.pointee.ifa_next }) {
let interface = ifptr.pointee
// Check for IPv4 or IPv6 interface:
let addrFamily = interface.ifa_addr.pointee.sa_family
if addrFamily == UInt8(AF_INET) || addrFamily == UInt8(AF_INET6) {
// Check interface name:
let name = String(cString: interface.ifa_name)
if name == "en0" {
// Convert interface address to a human readable string:
var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
getnameinfo(interface.ifa_addr, socklen_t(interface.ifa_addr.pointee.sa_len),
&hostname, socklen_t(hostname.count),
nil, socklen_t(0), NI_NUMERICHOST)
address = String(cString: hostname)
}
}
}
freeifaddrs(ifaddr)
return address
}
For those of you who came looking for more than the WIFI IP you could modify this code a little
func getAddress(for network: Network) -> String? {
var address: String?
// Get list of all interfaces on the local machine:
var ifaddr: UnsafeMutablePointer<ifaddrs>?
guard getifaddrs(&ifaddr) == 0 else { return nil }
guard let firstAddr = ifaddr else { return nil }
// For each interface ...
for ifptr in sequence(first: firstAddr, next: { $0.pointee.ifa_next }) {
let interface = ifptr.pointee
// Check for IPv4 or IPv6 interface:
let addrFamily = interface.ifa_addr.pointee.sa_family
if addrFamily == UInt8(AF_INET) || addrFamily == UInt8(AF_INET6) {
// Check interface name:
let name = String(cString: interface.ifa_name)
if name == network.rawValue {
// Convert interface address to a human readable string:
var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
getnameinfo(interface.ifa_addr, socklen_t(interface.ifa_addr.pointee.sa_len),
&hostname, socklen_t(hostname.count),
nil, socklen_t(0), NI_NUMERICHOST)
address = String(cString: hostname)
}
}
}
freeifaddrs(ifaddr)
return address
}
enum Network: String {
case wifi = "en0"
case cellular = "pdp_ip0"
//... case ipv4 = "ipv4"
//... case ipv6 = "ipv6"
}
Then we have access to the cellular IP as well.
guard let wifiIp = getAddress(for: .wifi) else { return }
&
guard let cellularIp = getAddress(for: .cellular) else { return }
iOS: How to specify DNS to be used to resolve hostname to IP address?
Here the code from my blogpost, that was already mentioned above, just slightly adapted to use IPv6.
Adapt setup_dns_server
First we could start with the changes to setup_dns_server:
void setup_dns_server(res_state res, const char *dns_server) {
struct in6_addr addr;
inet_pton(AF_INET6, dns_server, &addr);
res->_u._ext.ext->nsaddrs[0].sin6.sin6_addr = addr;
res->_u._ext.ext->nsaddrs[0].sin6.sin6_family = AF_INET6;
res->_u._ext.ext->nsaddrs[0].sin6.sin6_port = htons(NS_DEFAULTPORT);
res->nscount = 1;
}
Add __res_state_ext
This wouldn't compile because of a missing struct __res_state_ext. This structure is unfortunately in a private header file.
But the definition of that one can be take from here:
https://opensource.apple.com/source/libresolv/libresolv-65/res_private.h.auto.html :
struct __res_state_ext {
union res_sockaddr_union nsaddrs[MAXNS];
struct sort_list {
int af;
union {
struct in_addr ina;
struct in6_addr in6a;
} addr, mask;
} sort_list[MAXRESOLVSORT];
char nsuffix[64];
char bsuffix[64];
char nsuffix2[64];
};
The struct can be added e.g. at the top of the file.
Adapt resolveHost
The changes here include the longer buffer for ip (INET6_ADDRSTRLEN). res_ninit moved from setup_dns_server into this method and is matched now with a res_ndestroy.
+ (NSString *)resolveHost:(NSString *)host usingDNSServer:(NSString *)dnsServer {
struct __res_state res;
char ip[INET6_ADDRSTRLEN];
memset(ip, '\0', sizeof(ip));
res_ninit(&res);
setup_dns_server(&res, [dnsServer cStringUsingEncoding:NSASCIIStringEncoding]);
query_ip(&res, [host cStringUsingEncoding:NSUTF8StringEncoding], ip);
res_ndestroy(&res);
return [[NSString alloc] initWithCString:ip encoding:NSASCIIStringEncoding];
}
Retrieving IPv6 addresses
The changes above are already sufficient if you just want to use a IPv6 address for your DNS server. So in query_ip there are no changes necessary if you still want to retrieve the IPv4 addresses.
In case you would like to retrieve IPv6 addresses from the DNS server also, you can do this:
void query_ip(res_state res, const char *host, char ip[]) {
u_char answer[NS_PACKETSZ];
int len = res_nquery(res, host, ns_c_in, ns_t_aaaa, answer, sizeof(answer));
ns_msg handle;
ns_initparse(answer, len, &handle);
if(ns_msg_count(handle, ns_s_an) > 0) {
ns_rr rr;
if(ns_parserr(&handle, ns_s_an, 0, &rr) == 0) {
inet_ntop(AF_INET6, ns_rr_rdata(rr), ip, INET6_ADDRSTRLEN);
}
}
}
Please note: we use here ns_t_aaaa to get AAAA resource records (quad-A record), because in DNS this specifies the mapping between IPv6 address and hostname. For many hosts, there is no such quad-A record, meaning you can just reach them via IPv4.
Call
You would call it e.g. like so:
NSString *resolved = [ResolveUtil resolveHost:@"www.google.com" usingDNSServer:@"2001:4860:4860::8888"];
NSLog(@"%@", resolved);
The result would the look like this:
Disclaimer
These are just simple example calls, that demonstrate the basic usage of the functions. There is no error handling.
How to get Ip address in swift
As it turned out in the discussion, OP needs the interface address on a Mac and not on an iOS device as I thought initially. The code referenced in the question checks for the
interface name "en0", which is the WiFi interface on the iPhone. On a Mac it makes more
sense to check for any "up-and-running" interface instead.
Therefore I have rewritten the answer. It is now a Swift translation of the code in
Detect any connected network.
getifaddrs() is defined in <ifaddrs.h>, which is not included by default.
Therefore you have to create a bridging header and add
#include <ifaddrs.h>
The following function returns
an array with the names of all local "up-and-running" network interfaces.
func getIFAddresses() -> [String] {
var addresses = [String]()
// Get list of all interfaces on the local machine:
var ifaddr : UnsafeMutablePointer<ifaddrs> = nil
if getifaddrs(&ifaddr) == 0 {
// For each interface ...
var ptr = ifaddr
while ptr != nil {
defer { ptr = ptr.memory.ifa_next }
let flags = Int32(ptr.memory.ifa_flags)
let addr = ptr.memory.ifa_addr.memory
// Check for running IPv4, IPv6 interfaces. Skip the loopback interface.
if (flags & (IFF_UP|IFF_RUNNING|IFF_LOOPBACK)) == (IFF_UP|IFF_RUNNING) {
if addr.sa_family == UInt8(AF_INET) || addr.sa_family == UInt8(AF_INET6) {
// Convert interface address to a human readable string:
var hostname = [CChar](count: Int(NI_MAXHOST), repeatedValue: 0)
if (getnameinfo(ptr.memory.ifa_addr, socklen_t(addr.sa_len), &hostname, socklen_t(hostname.count),
nil, socklen_t(0), NI_NUMERICHOST) == 0) {
if let address = String.fromCString(hostname) {
addresses.append(address)
}
}
}
}
}
freeifaddrs(ifaddr)
}
return addresses
}
Update for Swift 3: In addition to adopting the code to the
many changes in Swift 3,
iterating over all interfaces can now use the new generalizedsequence() function:
func getIFAddresses() -> [String] {
var addresses = [String]()
// Get list of all interfaces on the local machine:
var ifaddr : UnsafeMutablePointer<ifaddrs>?
guard getifaddrs(&ifaddr) == 0 else { return [] }
guard let firstAddr = ifaddr else { return [] }
// For each interface ...
for ptr in sequence(first: firstAddr, next: { $0.pointee.ifa_next }) {
let flags = Int32(ptr.pointee.ifa_flags)
let addr = ptr.pointee.ifa_addr.pointee
// Check for running IPv4, IPv6 interfaces. Skip the loopback interface.
if (flags & (IFF_UP|IFF_RUNNING|IFF_LOOPBACK)) == (IFF_UP|IFF_RUNNING) {
if addr.sa_family == UInt8(AF_INET) || addr.sa_family == UInt8(AF_INET6) {
// Convert interface address to a human readable string:
var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
if (getnameinfo(ptr.pointee.ifa_addr, socklen_t(addr.sa_len), &hostname, socklen_t(hostname.count),
nil, socklen_t(0), NI_NUMERICHOST) == 0) {
let address = String(cString: hostname)
addresses.append(address)
}
}
}
}
freeifaddrs(ifaddr)
return addresses
}
iOS: Resolve DNS SRV records
After trying various things, I finally was able to make this work. As mentioned in comments by @Paulw11, the library DNS did not send the actual DNS request and hence I was not getting the desired result.
Option 1:
I finally decided to integrate the Objective-C example provided by Apple into my Swift application. To do so,
- I added the SRVResolver.h and SRVResolver.m into my project
- Created a bridging header file and added:
//
// Use this file to import your target's public headers that you would like to expose to Swift.
//
#include "SRVResolver.h"
- Added
libresolv.tbdin Link Binary With Libraries section under target's Build Phases
Now in my ViewController.swift I was able to use it as follows to get the priority, weight and hostname values:
let url = "_registration._tcp.gateway.zeeotp.com"
print("Starting discovery")
let resolver = SRVResolver.init(srvName: url)
assert(resolver != nil)
resolver?.delegate = self
resolver?.start()
while !(resolver!.isFinished) {
RunLoop.current.run(mode: .default, before: Date.distantFuture)
}
if(resolver?.error == nil) {
for result in resolver?.results ?? [] {
let dataArray = result as! NSDictionary;
for (key, value) in dataArray { // loop through data items
print("\(key) -> \(value)")
}
}
} else {
print("Error: \(String(describing: resolver?.error))")
}
Option: 2
I also found an external library NioDNS that allows us to do some DNS operations. Using this library also I was able to retrieve the SRV records. In my ViewController.swift I added the following code:
import NIO
import DNSClient
let loop: MultiThreadedEventLoopGroup!
do {
loop = MultiThreadedEventLoopGroup(numberOfThreads: 1)
let client = try DNSClient.connect(on: loop).wait()
let records = try client.getSRVRecords(from: url).wait()
for record in records {
print(record.resource.weight)
print(record.resource.priority)
print(record.resource.domainName.string)
}
} catch {
print("Error: \(error)")
}
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