Undefined reference to 'DTLS_client_method'

Question

I'm currently trying to implement DTLS on android in order to encrypt UDP datagrams. For this, I built the openssl-android project available here, from this I got two shared libraries libssl.so and libcrypto.so which I renamed libsslx.so and libcryptox.so to avoid confusion with the included library in the android system.

Then I put these files (and so for the openssl header folder) into my android project under the jni folder with the following structure:

jni->|->includes--->openssl--->header files
     |
     |->precompiled-|->libcryptox.so
     |              |
     |              |->libsslx.so
     |
     |->Android.mk
     |
     |->security.cpp

Content of the Android.mk file:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := sslx
LOCAL_SRC_FILES := precompiled/libsslx.so
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/includes
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := cryptox
LOCAL_SRC_FILES := precompiled/libcryptox.so
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/includes
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE    := security
LOCAL_SRC_FILES := security.cpp
LOCAL_SHARED_LIBRARIES := sslx cryptox

include $(BUILD_SHARED_LIBRARY)

Content of the security.cpp file

1 #include <jni.h>
2 #include <string.h>
3 #include <sys/types.h>
4 #include <sys/socket.h>
5 #include <netinet/in.h>
6 #include <arpa/inet.h>

7 extern "C" {

8  #include "openssl/bio.h"
9  #include "openssl/ssl.h"
10 #include "openssl/err.h"

11 struct sockaddr_in dst;

12 static int const SOCKET_ERROR = 1000;
13 static int const SOCKET_CREATED = 1100;
14 static int const BIO_ERROR = 1200;
15 static int const BIO_CREATED = 1300;
16 static int const CTX_ERROR = 1400;
17 static int const CTX_CREATED = 1500;
18 static int const SSL_ERROR = 1600;
19 static int const SSL_CREATED = 1700;

20 void Java_ch_gt_gcservjni_TestOpenSSLJni_initOpenSSL(JNIEnv *pEnv, jobject jObj){
21      SSL_load_error_strings();
22      ERR_load_BIO_strings();
23          OpenSSL_add_all_algorithms();
24 }

25 jlong Java_ch_gt_gcservjni_TestOpenSSLJni_startConnection(JNIEnv *pEnv, jobject jObj, jstring jAddress, jint jPort){

26    char *address;

27      jclass clazz = pEnv->GetObjectClass(jObj);
28      jmethodID mid = pEnv->GetMethodID(clazz, "printMessage", "(I)V");
29      if(mid == 0) return -1;

30      address = 0;
31      if (jAddress) {
32          address = (char *)pEnv->GetStringUTFChars( jAddress, 0);
33          if (!jAddress) return 0;
34      }

    //Socket creation/////////////////////////////////////////////////////////////////////////////
35      int sock = 0;
36      int port = (int)jPort;

37      struct sockaddr_in addr;
38      addr.sin_addr.s_addr = htonl(INADDR_ANY);
39      addr.sin_port = htons(port);

40      sock = socket(PF_INET, SOCK_DGRAM, 0);
41      if(sock < 0){
42          pEnv->CallVoidMethod(jObj, mid, SOCKET_ERROR);
43      }else{
44          pEnv->CallVoidMethod(jObj, mid, SOCKET_CREATED);
45      }

    ///////////////////////////////////////////////////////////////////////////////////////////////

    //Basic IO functionalities initialisation//////////////////////////////////////////////////////
46      BIO* cnx = BIO_new_dgram(sock, BIO_NOCLOSE);
47      if(cnx == NULL){
48          pEnv->CallVoidMethod(jObj, mid, BIO_ERROR);
49      }else{
50          pEnv->CallVoidMethod(jObj, mid, BIO_CREATED);
51      }
    ///////////////////////////////////////////////////////////////////////////////////////////////

52      struct sockaddr_in dst;
53      struct sockaddr* d = (struct sockaddr*)&dst;

54      dst.sin_family = AF_INET;
55      dst.sin_port = htons(port);
56      dst.sin_addr.s_addr = inet_addr(address);

    //Set the BIO connection
57      int err = BIO_dgram_set_peer(cnx, d);

    //Initialisalisation of the Context///////////////////////////////////////////////////////////
58      SSL_CTX *ctx = SSL_CTX_new(DTLSv1_client_method());
59      if(ctx == NULL){
60          pEnv->CallVoidMethod(jObj, mid, CTX_ERROR);
61      }
62      else{
63          pEnv->CallVoidMethod(jObj, mid, CTX_CREATED);
64      }

65      SSL_CTX_set_read_ahead(ctx, 1);
66      SSL_CTX_set_cipher_list(ctx, "HIGH:MEDIUM:aNull");

67      SSL *ssl = SSL_new(ctx);
68      if(ssl == NULL){
69          pEnv->CallVoidMethod(jObj, mid, SSL_ERROR);
70      }
71      else{
72          pEnv->CallVoidMethod(jObj, mid, SSL_CREATED);
73      }

74      SSL_set_bio(ssl, cnx, cnx);
75      SSL_set_connect_state(ssl);
76      return 0;
77   }

78 }

And here's the problem, when I build this code, all the functions are OK except the most important one which is the DTLSv1_client_method() when I initialize the context object at the line 58.

The generated error is this one:

/Applications/eclipse_bundle_mac/android-ndk-r8d/toolchains/arm-linux-androideabi-      4.6/prebuilt/darwin-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: ./obj/local/armeabi/objs/security/security.o: in function Java_ch_gt_gcservjni_TestOpenSSLJni_startConnection:jni/security.cpp:107: error: undefined reference to 'DTLSv1_client_method'

So it seems that the function is not referenced in my builded library, I checked my header files, the DTLS functions are there, I checked at the android-config.mk file of the openssl-android project to see if the functions were not excluded from the buid result and I tried to see the content of the .so files without success, btw I'm working on Mac OS X.

Has anyone got experience about DTLS on android? I'll appreciate some help for this problem.

EDIT: I managed to get the content of my .so files with the arm-linux-androideabi-objdump tool and no trace of any DTLS function. It maybe comes from the openssl build process I did, but it's strange because DTLS wasn't discarded in android-config.mk.

Answer 1

Ok, it's solved by just picking another project for building openssl and change the shared library names in the .mk files localted in /apps /ssl and /crypto folders to avoid confusion like it is told in this topic.

You can find the project I used under this url