#1374 configure: fix checking for DTLS_method

[Giulio Benetti]

configure: fix checking for DTLS_method

During checking of DTLS_method, the stub program is linked only with -ssl
libssl.a lacks some function from -lcrypto:
RAND_()
ERR_()
BUF_MEM_*()
etc.
and -lz:
- inflate()
- deflate()

Append -lcrypto and -lz to LIBS variable when checking DTLS_method.

[Bart Van Assche]

Since I would like to test this patch before applying it: on which operating system did you develop and test this patch?

[Giulio Benetti]

Hello,
this is a only workaround. It doesn't take into account autotools.

You can notice I don't touch configure.ac.
Anyway here is the log of a build failure with Buildroot:
http://autobuild.buildroot.net/results/e27/e2787d15f72949cbb347e8a1d344f5f80b4d7697/build-end.log

And here they're discussing a better patch:
https://patchwork.ozlabs.org/patch/967726/

So what I propose is something temporary before the one proposed on buildroot patchwork.

Kind regards

[Bart Van Assche]

How about this patch?

diff --git a/configure b/configure
index 6504a8e58a20..63d9b0cccc46 100755
--- a/configure
+++ b/configure
@@ -23197,7 +23197,7 @@ if ${ac_cv_lib_crypto_EVP_md5+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   ac_check_lib_save_LIBS=$LIBS
-LIBS="-lcrypto  $LIBS"
+LIBS="-lcrypto -lz $LIBS"
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */

@@ -23291,7 +23291,7 @@ _ACEOF
             LIBS="$netsnmp_save_LIBS"
         fi
         netsnmp_save_LIBS="$LIBS"
-        LIBS="-lssl"
+        LIBS="-lssl $LIBCRYPTO"
         for ac_func in TLS_method TLSv1_method DTLS_method DTLSv1_method                       SSL_library_init SSL_load_error_strings
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
diff --git a/configure.d/config_os_libs2 b/configure.d/config_os_libs2
index 4a1ad1551f95..c91b4818d556 100644
--- a/configure.d/config_os_libs2
+++ b/configure.d/config_os_libs2
@@ -306,7 +306,7 @@ if test "x$tryopenssl" != "xno" -a "x$tryopenssl" != "xinternal"; then
         LIBS="$netsnmp_save_LIBS"

         if test x$CRYPTO = x; then
-            AC_CHECK_LIB([crypto], [EVP_md5], [CRYPTO="crypto"])
+            AC_CHECK_LIB([crypto], [EVP_md5], [CRYPTO="crypto"], [], [-lz])
         fi

         if test x$CRYPTO != x; then
@@ -342,7 +342,7 @@ if test "x$tryopenssl" != "xno" -a "x$tryopenssl" != "xinternal"; then
             LIBS="$netsnmp_save_LIBS"
         fi
         netsnmp_save_LIBS="$LIBS"
-        LIBS="-lssl"
+        LIBS="-lssl $LIBCRYPTO"
         AC_CHECK_FUNCS([TLS_method TLSv1_method DTLS_method DTLSv1_method]dnl
                        [SSL_library_init SSL_load_error_strings])
         LIBS="$netsnmp_save_LIBS"

[Giulio Benetti]

Oh yes.
I've just realized somebody else took exactly that patch for Buildroot.
Here is mailing list mail:
http://buildroot-busybox.2317881.n4.nabble.com/PATCH-1-1-netsnmp-fix-static-build-with-openssl-td203429.html

So we can close this ticket!
Thank you.

[Bart Van Assche]

A version of this patch that also works for Windows has been pushed out. Please retest.

[Giulio Benetti]

Sorry, same problem as before, but we're almost there.
Now it's missing only zlib on "checking for DTLS_method"
I'm going to try to fix your patch too.

Here you have a Merge request for the same problem though:
https://sourceforge.net/p/net-snmp/code/merge-requests/17/

[Giulio Benetti]

Found the problem.
There was a mix of issues.
Going to send a patch for libz check in static linking.

[Giulio Benetti]

Here is the Merge Request:
https://sourceforge.net/p/net-snmp/code/merge-requests/18/

[Bart Van Assche]

Please retest with the latest master branch.

[Giulio Benetti]

And invert AC_CHECK_LIB like below too?
Because otherwise, with latest master we've got the same -lz dependency problem.

       if test x$CRYPTO = x; then
            AC_CHECK_LIB([crypto], [EVP_md5],
                         [CRYPTO="crypto"; LIBCRYPTO="-lcrypto -lz"], [
                AC_CHECK_LIB([crypto], [EVP_md5],
                         [CRYPTO="crypto"; LIBCRYPTO="-lcrypto"])], [], [-lz])
        else
            LIBCRYPTO="-l${CRYPTO}"
        fi

[Bart Van Assche]

No. I think that the root cause was not the order of the tests but caching of the test results. A change that clears the cached result has been checked in. Hence please retest with the latest master branch.

[Giulio Benetti]

I explained myself bad. I've already tried, but stil gives problem with DTLS.

So:
Build static with master and AC_CHECK_LIB() with -lz inverted works.
Now I'm going to compile without -lz, so let's see what happens

Any other idea?

[Giulio Benetti]

I mean I recompile Buildroot from scratch with same Architecture, static and without zlib package.
All with my latest patch inverting the testing of -lz.
So let's see if that rules(nested AC_CHECK_LIB()) works or not.
If I find it tries to link with -lz, there is something wrong, otherwise it should be ok.

[Giulio Benetti]

And of course my patch on top of latest commit of master you've pointed me.

[Giulio Benetti]

Pardon, you were right.
configure recognizes correctly EVP_md5 linking it with -lz
But still getting error:
The DTLS based transports require the libssl library from OpenSSL to be available and support DTLS

I dig more.

[Giulio Benetti]

Well, using AC_MSG_NOTICE() as logger, I've found the problem.
I open another Merge Request.
There shouldn't be other drawbacks.