teamd: add an option to force log output to stdout, stderr or syslog

By default, libdaemon prints the logs to stderr, and switches to syslog
if the precess daemonizes.

When some users, e.g. NetworkManager, run teamd foreground, the logs printed
in syslog will as coming from NetworkManager, with mixed NetworkManager's
own debug logs, which makes people feel a mess and hard to debug.

Add option -l to support force teamd log output to stdout, stderr or
syslog. Also add a global env TEAM_LOG_OUTPUT, which could be used for
old version compatibility.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>

Author: liuhangbin

man/teamd.8

@@ -69,6 +69,9 @@ Use the specified PID file.
 .B "\-g, \-\-debug"
 Turns on debugging messages. Repeating the option increases verbosity.
 .TP
+.B "\-l, \-\-log-output"
+Force teamd log output to stdout, stderr or syslog.
+.TP
 .B "\-r, \-\-force-recreate"
 Force team device recreation in case it already exists.
 .TP

teamd/teamd.c

@@ -107,6 +107,7 @@ static void print_help(const struct teamd_context *ctx) {
             "                             file will be ignored)\n"
             "    -p --pid-file=FILE       Use the specified PID file\n"
             "    -g --debug               Increase verbosity\n"
+            "    -l --log-output          Force teamd log output to stdout, stderr or syslog\n"
             "    -r --force-recreate      Force team device recreation in case it\n"
             "                             already exists\n"
             "    -o --take-over           Take over the device if it already exists\n"
@@ -140,6 +141,7 @@ static int parse_command_line(struct teamd_context *ctx,
 		{ "config",		required_argument,	NULL, 'c' },
 		{ "pid-file",		required_argument,	NULL, 'p' },
 		{ "debug",		no_argument,		NULL, 'g' },
+		{ "log-output",		required_argument,	NULL, 'l' },
 		{ "force-recreate",	no_argument,		NULL, 'r' },
 		{ "take-over",		no_argument,		NULL, 'o' },
 		{ "no-quit-destroy",	no_argument,		NULL, 'N' },
@@ -152,7 +154,7 @@ static int parse_command_line(struct teamd_context *ctx,
 		{ NULL, 0, NULL, 0 }
 	};
 
-	while ((opt = getopt_long(argc, argv, "hdkevf:c:p:groNt:nDZ:Uu",
+	while ((opt = getopt_long(argc, argv, "hdkevf:c:p:gl:roNt:nDZ:Uu",
 				  long_options, NULL)) >= 0) {
 
 		switch(opt) {
@@ -191,6 +193,10 @@ static int parse_command_line(struct teamd_context *ctx,
 		case 'g':
 			ctx->debug++;
 			break;
+		case 'l':
+			free(ctx->log_output);
+			ctx->log_output = strdup(optarg);
+			break;
 		case 'r':
 			ctx->force_recreate = true;
 			break;
@@ -1494,6 +1500,16 @@ static int teamd_start(struct teamd_context *ctx, enum teamd_exit_code *p_ret)
 	/* Child */
 	}
 
+	ctx->log_output = ctx->log_output ? : getenv("TEAM_LOG_OUTPUT");
+	if (ctx->log_output) {
+		if (strcmp(ctx->log_output, "stdout") == 0)
+			daemon_log_use = DAEMON_LOG_STDOUT;
+		else if (strcmp(ctx->log_output, "stderr") == 0)
+			daemon_log_use = DAEMON_LOG_STDERR;
+		else if (strcmp(ctx->log_output, "syslog") == 0)
+			daemon_log_use = DAEMON_LOG_SYSLOG;
+	}
+
 	if (daemon_close_all(-1) < 0) {
 		teamd_log_err("Failed to close all file descriptors.");
 		daemon_retval_send(errno);

teamd/teamd.h

@@ -99,6 +99,7 @@ struct teamd_context {
 	enum teamd_command		cmd;
 	bool				daemonize;
 	unsigned int			debug;
+	char *				log_output;
 	bool				force_recreate;
 	bool				take_over;
 	bool				no_quit_destroy;