lib: add `monitor:<fd>` command line log target

This provides direct raw log output with full metadata directly at
startup regardless of configuration details.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/log_vty.c b/lib/log_vty.c
index 682c9ea372..ef33a39d4a 100644
--- a/lib/log_vty.c
+++ b/lib/log_vty.c
@@ -427,6 +427,22 @@ void command_setup_early_logging(const char *dest, const char *level)
 		set_log_file(&zt_file_cmdline, NULL, sep, nlevel);
 		return;
 	}
+	if (strcmp(type, "monitor") == 0 && sep) {
+		struct zlog_live_cfg cfg = {};
+		unsigned long fd;
+		char *endp;
+
+		sep++;
+		fd = strtoul(sep, &endp, 10);
+		if (!*sep || *endp) {
+			fprintf(stderr, "invalid monitor fd \"%s\"\n", sep);
+			exit(1);
+		}
+
+		zlog_live_open_fd(&cfg, nlevel, fd);
+		zlog_live_disown(&cfg);
+		return;
+	}
 
 	fprintf(stderr, "invalid log target \"%s\" (\"%s\")\n", type, dest);
 	exit(1);