Read system-wide DNS servers

Add libresolv to podspec.

TunnelKit.podspec

@@ -23,6 +23,7 @@ Pod::Spec.new do |s|
                                     "APPLICATION_EXTENSION_API_ONLY" => "YES" }
         p.dependency "SwiftyBeaver"
         p.dependency "OpenSSL-Apple", "~> 1.1.0i.2"
+        p.libraries = "resolv"
     end
 
     s.subspec "AppExtension" do |p|

TunnelKit.xcodeproj/project.pbxproj

@@ -67,6 +67,12 @@
 		0E3B65772249254000EFF4DA /* tunnelbear.key in Resources */ = {isa = PBXBuildFile; fileRef = 0E3B65712249247E00EFF4DA /* tunnelbear.key */; };
 		0E3E0F212108A8CC00B371C1 /* SessionProxy+SessionReply.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0E3E0F202108A8CC00B371C1 /* SessionProxy+SessionReply.swift */; };
 		0E3E0F222108A8CC00B371C1 /* SessionProxy+SessionReply.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0E3E0F202108A8CC00B371C1 /* SessionProxy+SessionReply.swift */; };
+		0E411B9B2271F90700E0852C /* DNS.h in Headers */ = {isa = PBXBuildFile; fileRef = 0E411B992271F90700E0852C /* DNS.h */; };
+		0E411B9C2271F90700E0852C /* DNS.h in Headers */ = {isa = PBXBuildFile; fileRef = 0E411B992271F90700E0852C /* DNS.h */; };
+		0E411B9D2271F90700E0852C /* DNS.m in Sources */ = {isa = PBXBuildFile; fileRef = 0E411B9A2271F90700E0852C /* DNS.m */; };
+		0E411B9E2271F90700E0852C /* DNS.m in Sources */ = {isa = PBXBuildFile; fileRef = 0E411B9A2271F90700E0852C /* DNS.m */; };
+		0E411BA02271FA3300E0852C /* libresolv.tbd in Frameworks */ = {isa = PBXBuildFile; fileRef = 0E411B9F2271FA3300E0852C /* libresolv.tbd */; };
+		0E411BA22271FA3C00E0852C /* libresolv.tbd in Frameworks */ = {isa = PBXBuildFile; fileRef = 0E411BA12271FA3C00E0852C /* libresolv.tbd */; };
 		0E48AC642271ADA9009B1A98 /* PacketStream.h in Headers */ = {isa = PBXBuildFile; fileRef = 0E48AC622271ADA8009B1A98 /* PacketStream.h */; };
 		0E48AC652271ADA9009B1A98 /* PacketStream.h in Headers */ = {isa = PBXBuildFile; fileRef = 0E48AC622271ADA8009B1A98 /* PacketStream.h */; };
 		0E48AC662271ADA9009B1A98 /* PacketStream.m in Sources */ = {isa = PBXBuildFile; fileRef = 0E48AC632271ADA9009B1A98 /* PacketStream.m */; };
@@ -311,6 +317,10 @@
 		0E3B656E224923EC00EFF4DA /* tunnelbear.enc.1.ovpn */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = tunnelbear.enc.1.ovpn; sourceTree = "<group>"; };
 		0E3B65712249247E00EFF4DA /* tunnelbear.key */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = tunnelbear.key; sourceTree = "<group>"; };
 		0E3E0F202108A8CC00B371C1 /* SessionProxy+SessionReply.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "SessionProxy+SessionReply.swift"; sourceTree = "<group>"; };
+		0E411B992271F90700E0852C /* DNS.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = DNS.h; sourceTree = "<group>"; };
+		0E411B9A2271F90700E0852C /* DNS.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = DNS.m; sourceTree = "<group>"; };
+		0E411B9F2271FA3300E0852C /* libresolv.tbd */ = {isa = PBXFileReference; lastKnownFileType = "sourcecode.text-based-dylib-definition"; name = libresolv.tbd; path = Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/lib/libresolv.tbd; sourceTree = DEVELOPER_DIR; };
+		0E411BA12271FA3C00E0852C /* libresolv.tbd */ = {isa = PBXFileReference; lastKnownFileType = "sourcecode.text-based-dylib-definition"; name = libresolv.tbd; path = usr/lib/libresolv.tbd; sourceTree = SDKROOT; };
 		0E48AC622271ADA8009B1A98 /* PacketStream.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = PacketStream.h; sourceTree = "<group>"; };
 		0E48AC632271ADA9009B1A98 /* PacketStream.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = PacketStream.m; sourceTree = "<group>"; };
 		0E500EA522493B5B00CAE560 /* tunnelbear.enc.1.key */ = {isa = PBXFileReference; lastKnownFileType = text; path = tunnelbear.enc.1.key; sourceTree = "<group>"; };
@@ -435,6 +445,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				0E411BA22271FA3C00E0852C /* libresolv.tbd in Frameworks */,
 				B4C2A996F52241B77E7762BD /* Pods_TunnelKit_TunnelKit_iOS.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -443,6 +454,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				0E411BA02271FA3300E0852C /* libresolv.tbd in Frameworks */,
 				C20E3DDE8043C59193100CD3 /* Pods_TunnelKit_TunnelKit_macOS.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -645,6 +657,8 @@
 				0EFEB4352006D3C800F81029 /* DataPath.h */,
 				0EFEB44C2006D3C800F81029 /* DataPath.m */,
 				0EE7A79D20F6488400B42E6A /* DataPathCrypto.h */,
+				0E411B992271F90700E0852C /* DNS.h */,
+				0E411B9A2271F90700E0852C /* DNS.m */,
 				0E011F7C2196D97200BA59EE /* EndpointProtocol.swift */,
 				0EFEB4362006D3C800F81029 /* Errors.h */,
 				0EFEB44B2006D3C800F81029 /* Errors.m */,
@@ -709,6 +723,8 @@
 		1B27D1F0B446D5907FAF40E1 /* Frameworks */ = {
 			isa = PBXGroup;
 			children = (
+				0E411B9F2271FA3300E0852C /* libresolv.tbd */,
+				0E411BA12271FA3C00E0852C /* libresolv.tbd */,
 				276657B3FED3840178C53D6B /* Pods_TunnelKit_TunnelKit_iOS.framework */,
 				A23792F839E9B80C5EEB9D11 /* Pods_TunnelKit_TunnelKit_macOS.framework */,
 				BF76B5FEAAFD5056FFCC5DA2 /* Pods_TunnelKit_TunnelKitHost.framework */,
@@ -751,6 +767,7 @@
 				0E58BF502240F98F006FB157 /* CompressionAlgorithmNative.h in Headers */,
 				0E07596320EF733F00F38FD8 /* CryptoMacros.h in Headers */,
 				0EFEB46E2006D3C800F81029 /* TLSBox.h in Headers */,
+				0E411B9B2271F90700E0852C /* DNS.h in Headers */,
 				0E07596B20EF79AB00F38FD8 /* Crypto.h in Headers */,
 				0EFEB46B2006D3C800F81029 /* CryptoBox.h in Headers */,
 				0EFEB4592006D3C800F81029 /* Allocation.h in Headers */,
@@ -780,6 +797,7 @@
 				0E58BF512240F98F006FB157 /* CompressionAlgorithmNative.h in Headers */,
 				0E07596420EF733F00F38FD8 /* CryptoMacros.h in Headers */,
 				0EEC49EA20B5F7F6008FEB91 /* ZeroingData.h in Headers */,
+				0E411B9C2271F90700E0852C /* DNS.h in Headers */,
 				0E07596C20EF79AB00F38FD8 /* Crypto.h in Headers */,
 				0EEC49E120B5F7EA008FEB91 /* Allocation.h in Headers */,
 				0EEC49E320B5F7F6008FEB91 /* DataPath.h in Headers */,
@@ -1230,6 +1248,7 @@
 				0EBBF2F3208505D300E36B40 /* NEUDPInterface.swift in Sources */,
 				0EFEB4682006D3C800F81029 /* MSS.m in Sources */,
 				0E48AC662271ADA9009B1A98 /* PacketStream.m in Sources */,
+				0E411B9D2271F90700E0852C /* DNS.m in Sources */,
 				0EFEB45B2006D3C800F81029 /* TLSBox.m in Sources */,
 				0EFEB4792006D3C800F81029 /* TunnelKitProvider+Interaction.swift in Sources */,
 				0E58BF3922405410006FB157 /* minilzo.c in Sources */,
@@ -1299,6 +1318,7 @@
 				0EFEB49C2006D7F300F81029 /* Data+Manipulation.swift in Sources */,
 				0EBBF2F4208505D400E36B40 /* NEUDPInterface.swift in Sources */,
 				0E48AC672271ADA9009B1A98 /* PacketStream.m in Sources */,
+				0E411B9E2271F90700E0852C /* DNS.m in Sources */,
 				0EFEB4902006D7F300F81029 /* TunnelInterface.swift in Sources */,
 				0EFEB49E2006D7F300F81029 /* Allocation.m in Sources */,
 				0E58BF3A22405410006FB157 /* minilzo.c in Sources */,

TunnelKit/Sources/Core/DNS.h

@@ -0,0 +1,36 @@
+//
+//  DNS.h
+//  TunnelKit
+//
+//  Created by Davide De Rosa on 4/25/19.
+//  Copyright (c) 2019 Davide De Rosa. All rights reserved.
+//
+//  https://github.com/keeshux
+//
+//  This file is part of TunnelKit.
+//
+//  TunnelKit is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  TunnelKit is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface DNS : NSObject
+
+- (NSArray<NSString *> *)systemServers;
+    
+@end
+
+NS_ASSUME_NONNULL_END

TunnelKit/Sources/Core/DNS.m

@@ -0,0 +1,82 @@
+//
+//  DNS.m
+//  TunnelKit
+//
+//  Created by Davide De Rosa on 4/25/19.
+//  Copyright (c) 2019 Davide De Rosa. All rights reserved.
+//
+//  https://github.com/keeshux
+//
+//  This file is part of TunnelKit.
+//
+//  TunnelKit is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  TunnelKit is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+// adapted from: https://stackoverflow.com/questions/31256024/get-dns-server-ip-from-iphone-settings
+
+#import <resolv.h>
+#import <netdb.h>
+
+#import "DNS.h"
+
+@implementation DNS {
+    res_state _state;
+}
+
+- (instancetype)init
+{
+    if (self = [super init]) {
+        _state = malloc(sizeof(struct __res_state));
+        if (EXIT_SUCCESS != res_ninit(_state)) {
+            free(_state);
+            return nil;
+        }
+    }
+    return self;
+}
+    
+- (void)dealloc
+{
+    res_ndestroy(_state);
+    free(_state);
+}
+    
+- (NSArray<NSString *> *)systemServers
+{
+    NSMutableArray *addresses = [[NSMutableArray alloc] init];
+    
+    union res_sockaddr_union servers[NI_MAXSERV];
+    const int found = res_9_getservers(_state, servers, NI_MAXSERV);
+    char hostBuffer[NI_MAXHOST];
+
+    for (int i = 0; i < found; ++i) {
+        union res_sockaddr_union s = servers[i];
+        if (s.sin.sin_len <= 0) {
+            continue;
+        }
+        if (EXIT_SUCCESS == getnameinfo((struct sockaddr *)&s.sin,  // Pointer to your struct sockaddr
+                                        (socklen_t)s.sin.sin_len,   // Size of this struct
+                                        (char *)&hostBuffer,        // Pointer to hostname string
+                                        sizeof(hostBuffer),         // Size of this string
+                                        nil,                        // Pointer to service name string
+                                        0,                          // Size of this string
+                                        NI_NUMERICHOST)) {          // Flags given
+            [addresses addObject:[NSString stringWithUTF8String:hostBuffer]];
+        }
+    }
+    
+    return addresses;
+}
+
+@end

TunnelKit/Sources/Core/module.modulemap

@@ -49,6 +49,7 @@ module __TunnelKitNative {
     header "CompressionAlgorithmNative.h"
     header "DataPath.h"
     header "DataPathCrypto.h"
+    header "DNS.h"
     header "LZO.h"
     export *
 }

TunnelKitTests/DNSTests.swift

@@ -25,6 +25,7 @@
 
 import XCTest
 import TunnelKit
+import __TunnelKitNative
 
 class DNSTests: XCTestCase {
 
@@ -46,4 +47,8 @@ class DNSTests: XCTestCase {
         XCTAssertEqual(DNSResolver.string(fromIPv4: DNSResolver.ipv4(fromString: addr)!), addr)
         XCTAssertEqual(DNSResolver.ipv4(fromString: DNSResolver.string(fromIPv4: ip)), ip)
     }
+    
+    func testSystem() {
+        print("DNS: \(DNS().systemServers())")
+    }
 }