From d62ee95689e1e8c6fa4b395adfc8c0fcbca96b6f Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@tele2.at>
Date: Thu, 16 Aug 2018 00:10:03 +0200
Subject: [PATCH] Implement simple log rotation

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
---
 syslogd/backend.h |  2 ++
 syslogd/logfile.c | 68 ++++++++++++++++++++++++++++++++++++++---------
 syslogd/main.c    | 10 +++++++
 3 files changed, 68 insertions(+), 12 deletions(-)

diff --git a/syslogd/backend.h b/syslogd/backend.h
index 9f26a54..b5e238a 100644
--- a/syslogd/backend.h
+++ b/syslogd/backend.h
@@ -26,6 +26,8 @@ typedef struct log_backend_t {
 	void (*cleanup)(struct log_backend_t *log);
 
 	int (*write)(struct log_backend_t *log, const syslog_msg_t *msg);
+
+	void (*rotate)(struct log_backend_t *log);
 } log_backend_t;
 
 
diff --git a/syslogd/logfile.c b/syslogd/logfile.c
index 0fe9c9b..5f0f98a 100644
--- a/syslogd/logfile.c
+++ b/syslogd/logfile.c
@@ -85,6 +85,22 @@ typedef struct {
 } log_backend_file_t;
 
 
+static int logfile_open(logfile_t *file)
+{
+	file->fd = open(file->filename, O_WRONLY | O_CREAT, 0640);
+	if (file->fd < 0) {
+		perror(file->filename);
+		return -1;
+	}
+
+	if (lseek(file->fd, 0, SEEK_END)) {
+		close(file->fd);
+		return -1;
+	}
+
+	return 0;
+}
+
 static logfile_t *logfile_create(const char *filename)
 {
 	logfile_t *file = calloc(1, sizeof(*file) + strlen(filename) + 1);
@@ -96,21 +112,12 @@ static logfile_t *logfile_create(const char *filename)
 
 	strcpy(file->filename, filename);
 
-	file->fd = open(file->filename, O_WRONLY | O_CREAT, 0640);
-	if (file->fd < 0) {
-		perror(file->filename);
-		goto fail;
+	if (logfile_open(file)) {
+		free(file);
+		return NULL;
 	}
 
-	if (lseek(file->fd, 0, SEEK_END))
-		goto fail_fd;
-
 	return file;
-fail_fd:
-	close(file->fd);
-fail:
-	free(file);
-	return NULL;
 }
 
 static int logfile_write(logfile_t *file, const syslog_msg_t *msg)
@@ -119,6 +126,9 @@ static int logfile_write(logfile_t *file, const syslog_msg_t *msg)
 	char timebuf[32];
 	struct tm tm;
 
+	if (file->fd < 0 && logfile_open(file) != 0)
+		return -1;
+
 	lvl_str = enum_to_name(levels, msg->level);
 	if (lvl_str == NULL)
 		return -1;
@@ -133,6 +143,30 @@ static int logfile_write(logfile_t *file, const syslog_msg_t *msg)
 	return 0;
 }
 
+static int logfile_rotate(logfile_t *f)
+{
+	char timebuf[32];
+	char *filename;
+	struct tm tm;
+	time_t now;
+
+	now = time(NULL);
+	gmtime_r(&now, &tm);
+	strftime(timebuf, sizeof(timebuf), "%FT%T", &tm);
+
+	filename = alloca(strlen(f->filename) + strlen(timebuf) + 2);
+	sprintf(filename, "%s.%s", f->filename, timebuf);
+
+	if (rename(f->filename, filename)) {
+		perror(filename);
+		return -1;
+	}
+
+	close(f->fd);
+	logfile_open(f);
+	return 0;
+}
+
 /*****************************************************************************/
 
 static int file_backend_init(log_backend_t *log)
@@ -210,11 +244,21 @@ static int file_backend_write(log_backend_t *backend, const syslog_msg_t *msg)
 	return logfile_write(f, msg);
 }
 
+static void file_backend_rotate(log_backend_t *backend)
+{
+	log_backend_file_t *log = (log_backend_file_t *)backend;
+	logfile_t *f;
+
+	for (f = log->list; f != NULL; f = f->next)
+		logfile_rotate(f);
+}
+
 log_backend_file_t filebackend = {
 	.base = {
 		.init = file_backend_init,
 		.cleanup = file_backend_cleanup,
 		.write = file_backend_write,
+		.rotate = file_backend_rotate,
 	},
 	.list = NULL,
 };
diff --git a/syslogd/main.c b/syslogd/main.c
index 8f11906..6b4937e 100644
--- a/syslogd/main.c
+++ b/syslogd/main.c
@@ -34,6 +34,7 @@
 
 
 static volatile sig_atomic_t syslog_run = 1;
+static volatile sig_atomic_t syslog_rotate = 0;
 
 
 static void sighandler(int signo)
@@ -43,6 +44,9 @@ static void sighandler(int signo)
 	case SIGTERM:
 		syslog_run = 0;
 		break;
+	case SIGHUP:
+		syslog_rotate = 1;
+		break;
 	default:
 		break;
 	}
@@ -57,6 +61,7 @@ static void signal_setup(void)
 
 	sigaction(SIGINT, &act, NULL);
 	sigaction(SIGTERM, &act, NULL);
+	sigaction(SIGHUP, &act, NULL);
 }
 
 static int handle_data(int fd)
@@ -91,6 +96,11 @@ int main(void)
 		goto out;
 
 	while (syslog_run) {
+		if (syslog_rotate) {
+			logmgr->rotate(logmgr);
+			syslog_rotate = 0;
+		}
+
 		handle_data(sfd);
 	}