* filter.[ch]: dlsym error()

src/filter.c

@@ -91,6 +91,8 @@ f2b_filter_create(f2b_config_section_t *config, const char *file) {
     goto cleanup;
   if ((*(void **) (&filter->append)  = dlsym(filter->h, "append"))  == NULL)
     goto cleanup;
+  if ((*(void **) (&filter->error)   = dlsym(filter->h, "error"))   == NULL)
+    goto cleanup;
   if ((*(void **) (&filter->ready)   = dlsym(filter->h, "ready"))   == NULL)
     goto cleanup;
   if ((*(void **) (&filter->match)   = dlsym(filter->h, "match"))   == NULL)

src/filter.h

@@ -16,6 +16,7 @@ typedef struct f2b_filter_t {
   void *(*create)  (const char *id);
   bool  (*config)  (void *cfg, const char *key, const char *value);
   bool  (*append)  (void *cfg, const char *pattern);
+  char *(*error)   (void *cfg);
   bool  (*ready)   (void *cfg);
   bool  (*match)   (void *cfg, const char *line, char *buf, size_t buf_size);
   void  (*destroy) (void *cfg);