[PATCH] passt, log: Call __openlog() earlier, log to stderr until we detach

[Stefano Brivio <sbrivio@redhat.com>]

Paul reports that, with commit 15001b39ef1d ("conf: set the log level
much earlier"), early messages aren't reported to standard error
anymore.

The reason is that, once the log mask is changed from LOG_EARLY, we
don't force logging to stderr, and this mechanism was abused to have
early errors on stderr. Now that we drop LOG_EARLY earlier on, this
doesn't work anymore.

Call __openlog() as soon as we know the mode we're running as, using
LOG_PERROR. Then, once we detach, if we're not running from an
interactive terminal and logging to standard error is not forced,
drop LOG_PERROR from the options.

While at it, make sure we don't print messages to standard error
reporting that we couldn't log to the system logger, if we didn't
open a connection yet. That's expected.

Reported-by: Paul Holzinger <pholzing@redhat.com>
Fixes: 15001b39ef1d ("conf: set the log level much earlier")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 log.c   |  2 +-
 passt.c | 14 +++++++-------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/log.c b/log.c
index eafaca2..bdd31b4 100644
--- a/log.c
+++ b/log.c
@@ -174,7 +174,7 @@ void passt_vsyslog(int pri, const char *format, va_list ap)
 	if (log_opt & LOG_PERROR)
 		fprintf(stderr, "%s", buf + prefix_len);
 
-	if (send(log_sock, buf, n, 0) != n)
+	if (log_sock >= 0 && send(log_sock, buf, n, 0) != n)
 		fprintf(stderr, "Failed to send %i bytes to syslog\n", n);
 }
 
diff --git a/passt.c b/passt.c
index f430648..e4cb11e 100644
--- a/passt.c
+++ b/passt.c
@@ -225,6 +225,8 @@ int main(int argc, char **argv)
 	strncpy(argv0, argv[0], PATH_MAX - 1);
 	name = basename(argv0);
 	if (strstr(name, "pasta")) {
+		__openlog(log_name = "pasta", LOG_PERROR, LOG_DAEMON);
+
 		sa.sa_handler = pasta_child_handler;
 		if (sigaction(SIGCHLD, &sa, NULL)) {
 			die("Couldn't install signal handlers: %s",
@@ -237,18 +239,16 @@ int main(int argc, char **argv)
 		}
 
 		c.mode = MODE_PASTA;
-		log_name = "pasta";
 	} else if (strstr(name, "passt")) {
+		__openlog(log_name = "passt", LOG_PERROR, LOG_DAEMON);
+
 		c.mode = MODE_PASST;
-		log_name = "passt";
 	} else {
 		exit(EXIT_FAILURE);
 	}
 
 	madvise(pkt_buf, TAP_BUF_BYTES, MADV_HUGEPAGE);
 
-	__openlog(log_name, 0, LOG_DAEMON);
-
 	c.epollfd = epoll_create1(EPOLL_CLOEXEC);
 	if (c.epollfd == -1) {
 		perror("epoll_create1");
@@ -269,9 +269,6 @@ int main(int argc, char **argv)
 	conf(&c, argc, argv);
 	trace_init(c.trace);
 
-	if (c.force_stderr || isatty(fileno(stdout)))
-		__openlog(log_name, LOG_PERROR, LOG_DAEMON);
-
 	pasta_netns_quit_init(&c);
 
 	tap_sock_init(&c);
@@ -314,6 +311,9 @@ int main(int argc, char **argv)
 	if (isolate_prefork(&c))
 		die("Failed to sandbox process, exiting");
 
+	if (!c.force_stderr && !isatty(fileno(stdout)))
+		__openlog(log_name, 0, LOG_DAEMON);
+
 	if (!c.foreground)
 		__daemon(pidfile_fd, devnull_fd);
 	else
-- 
@@ -225,6 +225,8 @@ int main(int argc, char **argv)
 	strncpy(argv0, argv[0], PATH_MAX - 1);
 	name = basename(argv0);
 	if (strstr(name, "pasta")) {
+		__openlog(log_name = "pasta", LOG_PERROR, LOG_DAEMON);
+
 		sa.sa_handler = pasta_child_handler;
 		if (sigaction(SIGCHLD, &sa, NULL)) {
 			die("Couldn't install signal handlers: %s",
@@ -237,18 +239,16 @@ int main(int argc, char **argv)
 		}
 
 		c.mode = MODE_PASTA;
-		log_name = "pasta";
 	} else if (strstr(name, "passt")) {
+		__openlog(log_name = "passt", LOG_PERROR, LOG_DAEMON);
+
 		c.mode = MODE_PASST;
-		log_name = "passt";
 	} else {
 		exit(EXIT_FAILURE);
 	}
 
 	madvise(pkt_buf, TAP_BUF_BYTES, MADV_HUGEPAGE);
 
-	__openlog(log_name, 0, LOG_DAEMON);
-
 	c.epollfd = epoll_create1(EPOLL_CLOEXEC);
 	if (c.epollfd == -1) {
 		perror("epoll_create1");
@@ -269,9 +269,6 @@ int main(int argc, char **argv)
 	conf(&c, argc, argv);
 	trace_init(c.trace);
 
-	if (c.force_stderr || isatty(fileno(stdout)))
-		__openlog(log_name, LOG_PERROR, LOG_DAEMON);
-
 	pasta_netns_quit_init(&c);
 
 	tap_sock_init(&c);
@@ -314,6 +311,9 @@ int main(int argc, char **argv)
 	if (isolate_prefork(&c))
 		die("Failed to sandbox process, exiting");
 
+	if (!c.force_stderr && !isatty(fileno(stdout)))
+		__openlog(log_name, 0, LOG_DAEMON);
+
 	if (!c.foreground)
 		__daemon(pidfile_fd, devnull_fd);
 	else
-- 
2.39.2