now this seem to build.

Makefile.am

@@ -2,13 +2,12 @@ ACLOCAL_AMFLAGS = -I m4
 
 lib_LTLIBRARIES = libmodentropy.la
 
-libmodentropy_la_SOURCES = mod_entropy.c mod_entropy_get_entropy_bits.c \
-			   mod_entropy_add_entropy.c
+libmodentropy_la_SOURCES = mod_entropy.c
 libmodentropy_la_LDFLAGS = -lrt -lm
 
 install: libmodentropy.la
-	apxs -i -a -n entropy libmodentropy.la
+	@APXS@ -i -a -n entropy libmodentropy.la
 
 ## Define that an include directory is required.
-#INCLUDES = -I@apache_dir@/include -I/usr/include/apr-1
+INCLUDES = -I@AP_INCLUDE@ -I@APR_INCLUDE@
 

configure.ac

@@ -1,6 +1,7 @@
 AC_PREREQ([2.68])
 
 AC_INIT([mod_entropy], [0.1.0], [Georg Hopp <georg@steffers.org])
+LT_INIT
 AM_INIT_AUTOMAKE
 
 AC_CONFIG_SRCDIR([mod_entropy.c])
@@ -9,7 +10,7 @@ AC_CONFIG_MACRO_DIR([m4])
 
 #AM_SILENT_RULES([yes])
 AC_COPYRIGHT([Copyright © 2012 Georg Hopp])
-AC_REVISION([$Revision: 0.02 $])
+AC_REVISION([$Revision: 0.01 $])
 
 # Checks for programs.
 AC_PROG_CC
@@ -20,25 +21,32 @@ AC_CHECK_LIB([m], [log])
 AC_CHECK_LIB([rt], [clock_gettime])
 AC_CHECK_LIB([aprutil], [apr_palloc])
 
-# apache apxs linking                                                                     
+# apache apxs
 AC_SUBST(APXS)
 AC_CHECK_PROGS(APXS, apxs)
 
 if test -z "$APXS"; then
-  AC_MSG_WARN([[apxs missing]])                                                           
+  AC_MSG_ERROR([[apxs missing]])
 fi
                                                                                           
-AC_SUBST(MODULEDIR)                                                                       
-AC_MSG_CHECKING(apache module directory)                                                  
-if test -x "$APXS"; then                                                                  
-  MODULEDIR=`${APXS} -q LIBEXECDIR`                                                       
-else                                                                                      
-  MODULEDIR=/usr/local/lib                                                                
-fi                                                                                        
-AC_MSG_RESULT($MODULEDIR)                     
+# apache include dir
+AC_SUBST(AP_INCLUDE)
+AC_MSG_CHECKING(apache include directory)
+AP_INCLUDE=$(${APXS} -q INCLUDEDIR)
+AC_MSG_RESULT($AP_INCLUDE)
+
+# apr-1
+AC_SUBST(APR1)
+AC_CHECK_PROGS(APR1, apr-1-config)
+
+# apr-1 include dir
+AC_SUBST(APR_INCLUDE)
+AC_MSG_CHECKING(apr-1 include directory)
+APR_INCLUDE=$(${APR1} --includedir)
+AC_MSG_RESULT($APR_INCLUDE)
 
 # Checks for header files.
-AC_CHECK_HEADERS([fcntl.h sys/ioctl.h])
+AC_CHECK_HEADERS([fcntl.h sys/ioctl.h linux/random.h])
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_TYPE_SIZE_T

mod_entropy.c

@@ -13,11 +13,15 @@
  */
 #define _POSIX_C_SOURCE 199309L
 
-#include <apache2/httpd.h>
-#include <apache2/http_core.h>
-#include <apr-1/apu.h>
-#include <apr-1/apr_general.h>
-#include <apr-1/apr_sha1.h>
+#include "httpd.h"
+#include "http_core.h"
+#include "http_connection.h"
+#include "http_config.h"
+#include "http_core.h"
+#include "http_log.h"
+#include "apu.h"
+#include "apr_general.h"
+#include "apr_sha1.h"
 
 #include <time.h>
 #include <math.h>
@@ -127,8 +131,8 @@ entropy_filter_in(
 	 */
 	apr_sha1_update(
 			&sha1_ctx,
-			connection->client_ip,
-			strlen(connection->client_ip));
+			connection->remote_ip,
+			strlen(connection->remote_ip));
 
 	/**
 	 * add request line to sha1