logging: Add ability to save/print current log filters

This enables the persistent configuration of let's say
'log filter imsi 012345678' for a given log file in the config
file.

include/osmocom/core/logging.h

@@ -95,6 +95,17 @@ struct log_target;
 typedef int log_filter(const struct log_context *ctx,
 		       struct log_target *target);
 
+struct log_info;
+struct vty;
+
+typedef void log_print_filters(struct vty *vty,
+			       const struct log_info *info,
+			       const struct log_target *tgt);
+
+typedef void log_save_filters(struct vty *vty,
+			      const struct log_info *info,
+			      const struct log_target *tgt);
+
 /*! \brief Logging configuration, passed to \ref log_init */
 struct log_info {
 	/* \brief filter callback function */
@@ -106,6 +117,11 @@ struct log_info {
 	unsigned int num_cat;
 	/*! \brief total number of user categories (not library) */
 	unsigned int num_cat_user;
+
+	/* \brief filter saving function */
+	log_save_filters *save_fn;
+	/* \brief filter saving function */
+	log_print_filters *print_fn;
 };
 
 /*! \brief Type of logging target */

src/Makefile.am

@@ -1,6 +1,6 @@
 # This is _NOT_ the library release version, it's an API version.
 # Please read Chapter 6 "Library interface versions" of the libtool documentation before making any modification
-LIBVERSION=4:0:0
+LIBVERSION=5:0:0
 
 AM_CFLAGS = -Wall $(all_includes) -I$(top_srcdir)/include -I$(top_builddir)/include
 

src/vty/logging_vty.c

@@ -252,7 +252,9 @@ static void vty_print_logtarget(struct vty *vty, const struct log_info *info,
 		tgt->filter_map & LOG_FILTER_ALL ? "Enabled" : "Disabled",
 		VTY_NEWLINE);
 
-	/* FIXME: print application specific filters */
+	/* print application specific filters */
+	if (info->print_fn)
+		info->print_fn(vty, info, tgt);
 }
 
 #define SHOW_LOG_STR "Show current logging configuration\n"
@@ -617,7 +619,9 @@ static int config_write_log_single(struct vty *vty, struct log_target *tgt)
 
 	vty_out(vty, "  logging filter all %u%s",
 		tgt->filter_map & LOG_FILTER_ALL ? 1 : 0, VTY_NEWLINE);
-	/* FIXME: how to do this for filters outside of libosmocore? */
+	/* save filters outside of libosmocore, i.e. in app code */
+	if (osmo_log_info->save_fn)
+		osmo_log_info->save_fn(vty, osmo_log_info, tgt);
 
 	vty_out(vty, "  logging color %u%s", tgt->use_color ? 1 : 0,
 		VTY_NEWLINE);