lib: rewrite zlog lock-free & TLS-buffered

This is a full rewrite of the "back end" logging code.  It now uses a
lock-free list to iterate over logging targets, and the targets
themselves are as lock-free as possible.  (syslog() may have a hidden
internal mutex in the C library;  the file/fd targets use a single
write() call which should ensure atomicity kernel-side.)

Note that some functionality is lost in this patch:
- Solaris printstack() backtraces are ditched (unlikely to come back)
- the `log-filter` machinery is gone (re-added in followup commit)
- `terminal monitor` is temporarily stubbed out.  The old code had a
  race condition with VTYs going away.  It'll likely come back rewritten
  and with vtysh support.
- The `zebra_ext_log` hook is gone.  Instead, it's now much easier to
  add a "proper" logging target.

v2: TLS buffer to get some actual performance

Signed-off-by: David Lamparter <equinox@diac24.net>

2 files changed, 18 insertions, 3 deletions

diff --git a/watchfrr/watchfrr.c b/watchfrr/watchfrr.c
index 05e6651229..d6d8f77243 100644
--- a/watchfrr/watchfrr.c
+++ b/watchfrr/watchfrr.c
@@ -27,6 +27,7 @@
 #include "command.h"
 #include "libfrr.h"
 #include "lib_errors.h"
+#include "zlog_targets.h"
 
 #include <getopt.h>
 #include <sys/un.h>
@@ -1369,11 +1370,10 @@ int main(int argc, char **argv)
 
 	frr_config_fork();
 
-	zlog_set_level(ZLOG_DEST_MONITOR, ZLOG_DISABLED);
 	if (watchfrr_di.daemon_mode)
-		zlog_set_level(ZLOG_DEST_SYSLOG, MIN(gs.loglevel, LOG_DEBUG));
+		zlog_syslog_set_prio_min(MIN(gs.loglevel, LOG_DEBUG));
 	else
-		zlog_set_level(ZLOG_DEST_STDOUT, MIN(gs.loglevel, LOG_DEBUG));
+		zlog_aux_init(NULL, MIN(gs.loglevel, LOG_DEBUG));
 
 	frr_run(master);
 
diff --git a/watchfrr/watchfrr_vty.c b/watchfrr/watchfrr_vty.c
index c06cb89382..eda4f5d516 100644
--- a/watchfrr/watchfrr_vty.c
+++ b/watchfrr/watchfrr_vty.c
@@ -23,6 +23,7 @@
 
 #include "memory.h"
 #include "log.h"
+#include "log_vty.h"
 #include "vty.h"
 #include "command.h"
 
@@ -134,6 +135,19 @@ DEFUN (show_watchfrr,
 	return CMD_SUCCESS;
 }
 
+/* we don't have the other logging commands since watchfrr only accepts
+ * log config through command line options
+ */
+DEFUN_NOSH (show_logging,
+	    show_logging_cmd,
+	    "show logging",
+	    SHOW_STR
+	    "Show current logging configuration\n")
+{
+	log_show_syslog(vty);
+	return CMD_SUCCESS;
+}
+
 #ifndef VTYSH_EXTRACT_PL
 #include "watchfrr/watchfrr_vty_clippy.c"
 #endif
@@ -190,4 +204,5 @@ void watchfrr_vty_init(void)
 
 	install_element(CONFIG_NODE, &show_debugging_watchfrr_cmd);
 	install_element(VIEW_NODE, &show_watchfrr_cmd);
+	install_element(VIEW_NODE, &show_logging_cmd);
 }