small workaround to make this module work on apache 2.2.x as well as 2.4.x

mod_entropy.c

@@ -70,15 +70,19 @@ entropy_filter_in(
 		apr_read_type_e      block,
 		apr_off_t            readbytes)
 {
-	apr_bucket   *  bucket;
-	apr_status_t    status;
-	request_rec  *  request    = filter->r;
-	conn_rec     *  connection = filter->c;
-	apr_sha1_ctx_t  sha1_ctx;
-	unsigned char  	digest[APR_SHA1_DIGESTSIZE];
+	apr_bucket     * bucket;
+	apr_status_t     status;
+	request_rec    * request    = filter->r;
+	conn_rec       * connection = filter->c;
+	apr_sha1_ctx_t   sha1_ctx;
+	unsigned char    digest[APR_SHA1_DIGESTSIZE];
+	ap_version_t     ap_version;
+	char           * remote_ip;
 
 	struct timespec ts;
 
+	ap_get_server_revision(&ap_version);
+
 	clock_gettime(CLOCK_REALTIME, &ts);
 
 	apr_sha1_init(&sha1_ctx);
@@ -94,10 +98,11 @@ entropy_filter_in(
 	/**
 	 * add client ip to sha1
 	 */
-	apr_sha1_update(
-			&sha1_ctx,
-			connection->remote_ip,
-			strlen(connection->remote_ip));
+	remote_ip = (ap_version.minor < 4)?
+		connection->remote_ip:
+		connection->client_ip;
+
+	apr_sha1_update(&sha1_ctx, remote_ip, strlen(remote_ip));
 
 	/**
 	 * add request line to sha1