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authorDarell Tan <darell.tan@gmail.com>2011-09-19 22:56:48 +0800
committerDarell Tan <darell.tan@gmail.com>2011-09-19 22:56:48 +0800
commit6746183446e9afed4816899ddad16da0b3b4908e (patch)
tree44e8e814f6cdff2885176554effeb3656e510e02
parent0379c23415e88831c30a6d9548296199ead4a6e3 (diff)
downloadmdns-repeater-6746183446e9afed4816899ddad16da0b3b4908e.tar.gz
mdns-repeater-6746183446e9afed4816899ddad16da0b3b4908e.zip
Write a pid file to prevent multiple instances.
-rw-r--r--mdns-repeater.c82
1 files changed, 77 insertions, 5 deletions
diff --git a/mdns-repeater.c b/mdns-repeater.c
index 8192146..3f59106 100644
--- a/mdns-repeater.c
+++ b/mdns-repeater.c
@@ -37,6 +37,7 @@
#define MDNS_ADDR "224.0.0.251"
#define MDNS_PORT 5353
+#define PIDFILE "/var/run/" PACKAGE ".pid"
struct if_sock {
const char *ifname; /* interface name */
@@ -57,6 +58,7 @@ void *pkt_data = NULL;
int foreground = 0;
int shutdown_flag = 0;
+char *pid_file = PIDFILE;
void log_message(int loglevel, char *fmt_str, ...) {
va_list ap;
@@ -211,7 +213,41 @@ static void mdns_repeater_shutdown(int sig) {
shutdown_flag = 1;
}
+static pid_t already_running() {
+ FILE *f;
+ int count;
+ pid_t pid;
+
+ f = fopen(pid_file, "r");
+ if (f != NULL) {
+ count = fscanf(f, "%d", &pid);
+ fclose(f);
+ if (count == 1) {
+ // see if pid exists (works on daemonized instances only)
+ if (getsid(pid) > 0)
+ return pid;
+ }
+ }
+
+ return -1;
+}
+
+static int write_pidfile() {
+ FILE *f;
+ int r;
+
+ f = fopen(pid_file, "w");
+ if (f != NULL) {
+ r = fprintf(f, "%d", getpid());
+ fclose(f);
+ return (r > 0);
+ }
+
+ return 0;
+}
+
static void daemonize() {
+ pid_t running_pid;
pid_t pid = fork();
if (pid < 0) {
log_message(LOG_ERR, "fork(): %m");
@@ -240,6 +276,16 @@ static void daemonize() {
exit(1);
}
}
+
+ // check for pid file
+ running_pid = already_running();
+ if (running_pid != -1) {
+ log_message(LOG_ERR, "already running as pid %d", running_pid);
+ exit(1);
+ } else if (! write_pidfile()) {
+ log_message(LOG_ERR, "unable to write pid file %s", pid_file);
+ exit(1);
+ }
}
static void show_help(const char *progname) {
@@ -252,6 +298,7 @@ static void show_help(const char *progname) {
"\n"
" flags:\n"
" -f runs in foreground for debugging\n"
+ " -p specifies the pid file path (default: " PIDFILE ")\n"
" -h shows this help\n"
"\n"
);
@@ -260,10 +307,16 @@ static void show_help(const char *progname) {
static int parse_opts(int argc, char *argv[]) {
int c;
int help = 0;
- while ((c = getopt(argc, argv, "hf")) != -1) {
+ while ((c = getopt(argc, argv, "hfp:")) != -1) {
switch (c) {
case 'h': help = 1; break;
case 'f': foreground = 1; break;
+ case 'p':
+ if (optarg[0] != '/')
+ fprintf(stderr, "pid file path must be absolute\n");
+ else
+ pid_file = optarg;
+ break;
case '?':
case ':':
@@ -285,7 +338,9 @@ static int parse_opts(int argc, char *argv[]) {
}
int main(int argc, char *argv[]) {
+ pid_t running_pid;
fd_set sockfd_set;
+ int r = 0;
parse_opts(argc, argv);
@@ -298,12 +353,21 @@ int main(int argc, char *argv[]) {
openlog(PACKAGE, LOG_PID | LOG_CONS, LOG_DAEMON);
if (! foreground)
daemonize();
+ else {
+ // check for pid file when running in foreground
+ running_pid = already_running();
+ if (running_pid != -1) {
+ fprintf(stderr, "already running as pid %d", running_pid);
+ exit(1);
+ }
+ }
// create receiving socket
server_sockfd = create_recv_sock();
if (server_sockfd < 0) {
log_message(LOG_ERR, "unable to create server socket");
- return 1;
+ r = 1;
+ goto end_main;
}
// create sending sockets
@@ -312,7 +376,8 @@ int main(int argc, char *argv[]) {
int sockfd = create_send_sock(server_sockfd, argv[i], &socks[num_socks]);
if (sockfd < 0) {
log_message(LOG_ERR, "unable to create socket for interface %s", argv[i]);
- return 1;
+ r = 1;
+ goto end_main;
}
num_socks++;
}
@@ -320,7 +385,8 @@ int main(int argc, char *argv[]) {
pkt_data = malloc(PACKET_SIZE);
if (pkt_data == NULL) {
log_message(LOG_ERR, "cannot malloc() packet buffer: %m");
- return 1;
+ r = 1;
+ goto end_main;
}
while (! shutdown_flag) {
@@ -384,6 +450,8 @@ int main(int argc, char *argv[]) {
log_message(LOG_INFO, "shutting down...");
+end_main:
+
if (pkt_data != NULL)
free(pkt_data);
@@ -393,7 +461,11 @@ int main(int argc, char *argv[]) {
for (i = 0; i < num_socks; i++)
close(socks[i].sockfd);
+ // remove pid file if it belongs to us
+ if (already_running() == getpid())
+ unlink(pid_file);
+
log_message(LOG_INFO, "exit.");
- return 0;
+ return r;
}