From: Roy Marples <roy@marples.name>
Date: Sun, 13 May 2007 12:28:54 +0000 (+0000)
Subject: flock the pidfile and stop writing the parent pid to it so we're more robst.
X-Git-Tag: v3.2.3~259
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=438263e0571dc945a5bf85445e4904c0f853cce6;p=thirdparty%2Fdhcpcd.git

flock the pidfile and stop writing the parent pid to it so we're more robst.
---

diff --git a/ChangeLog b/ChangeLog
index cfacbff8..6ea14c64 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,4 @@
+flock the pidfile and stop writing the parent pid to it so we're more robst.
 Enable DHCP_INFORM support via the -S option (requires -s ipaddr too)
 Use the DUID stored to create an RFC 4361 conformant client identifier
 if none is specified instead of just using the MAC address.
diff --git a/client.c b/client.c
index 59cadf90..d32f6298 100644
--- a/client.c
+++ b/client.c
@@ -19,12 +19,16 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#ifdef __linux__
+# define _XOPEN_SOURCE 500 /* needed for pwrite */
+#endif
+
 #include <sys/types.h>
 #include <sys/select.h>
 #include <sys/time.h>
 #include <arpa/inet.h>
 #ifdef __linux__
-#include <netinet/ether.h>
+# include <netinet/ether.h>
 #endif
 #include <errno.h>
 #include <fcntl.h>
@@ -39,14 +43,14 @@
 #include "config.h"
 #include "common.h"
 #ifdef ENABLE_ARP
-#include "arp.h"
+# include "arp.h"
 #endif
 #include "client.h"
 #include "configure.h"
 #include "dhcp.h"
 #include "dhcpcd.h"
 #ifdef ENABLE_INFO
-#include "info.h"
+# include "info.h"
 #endif
 #include "interface.h"
 #include "logger.h"
@@ -98,18 +102,32 @@
 	memset (dhcp, 0, sizeof (dhcp_t)); \
 }
 
-static int daemonise (const char *pidfile)
+static bool daemonise (int *pidfd)
 {
+	char pid[16];
+
 	logger (LOG_DEBUG, "forking to background");
 
 	if (daemon (0, 0) < 0) {
 		logger (LOG_ERR, "daemon: %s", strerror (errno));
-		return -1;
+		return (false);
 	}
 
-	make_pid (pidfile);
+	if (ftruncate (*pidfd, 0) == -1) {
+		logger (LOG_ERR, "ftruncate: %s", strerror (errno));
+		return (false);
+	}
+
+	snprintf (pid, sizeof (pid), "%u", getpid());
+	if (pwrite (*pidfd, pid, strlen(pid), 0) != (ssize_t) strlen (pid)) {
+		logger (LOG_ERR, "pwrite: %s", strerror (errno));
+		return (false);
+	}
+	
+	close (*pidfd);
+	*pidfd = -1;
 
-	return 0;
+	return (true);
 }
 
 static unsigned long random_xid (void)
@@ -138,7 +156,7 @@ static unsigned long random_xid (void)
 
 /* This state machine is based on the one from udhcpc
    written by Russ Dill */
-int dhcp_run (const options_t *options)
+int dhcp_run (const options_t *options, int *pidfd)
 {
 	interface_t *iface;
 	int mode = SOCKET_CLOSED;
@@ -374,7 +392,7 @@ int dhcp_run (const options_t *options)
 								iface->start_uptime = uptime ();
 
 								if (! daemonised && options->daemonise) {
-									if ((daemonise (options->pidfile)) < 0) {
+									if ((daemonise (pidfd)) < 0) {
 										retval = -1;
 										goto eexit;
 									}
@@ -639,7 +657,7 @@ int dhcp_run (const options_t *options)
 						}
 
 						if (! daemonised && options->daemonise) {
-							if ((daemonise (options->pidfile)) < 0 ) {
+							if ((daemonise (pidfd)) < 0 ) {
 								retval = EXIT_FAILURE;
 								goto eexit;
 							}
diff --git a/client.h b/client.h
index 88c460e1..406c8b79 100644
--- a/client.h
+++ b/client.h
@@ -24,6 +24,6 @@
 
 #include "dhcpcd.h"
 
-int dhcp_run (const options_t *options);
+int dhcp_run (const options_t *options, int *pidfd);
 
 #endif
diff --git a/dhcpcd.c b/dhcpcd.c
index 5f264413..09e4b43e 100644
--- a/dhcpcd.c
+++ b/dhcpcd.c
@@ -24,6 +24,7 @@
 #define _POSIX_SOURCE
 #endif
 
+#include <sys/file.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <arpa/inet.h>
@@ -76,19 +77,6 @@ static pid_t read_pid(const char *pidfile)
 	return pid;
 }
 
-void make_pid (const char *pidfile)
-{
-	FILE *fp;
-
-	if ((fp = fopen (pidfile, "w")) == NULL) {
-		logger (LOG_ERR, "fopen `%s': %s", pidfile, strerror (errno));
-		return;
-	}
-
-	fprintf (fp, "%u\n", getpid ());
-	fclose (fp);
-}
-
 static void usage ()
 {
 	printf ("usage: "PACKAGE" [-adknpEGHMNRSY] [-c script] [-h hostame] [-i classID]\n"
@@ -108,6 +96,7 @@ int main(int argc, char **argv)
 	pid_t pid;
 	int debug = 0;
 	int i;
+	int pidfd;
 
 	const struct option longopts[] = {
 		{"arp",         no_argument,        NULL, 'a'},
@@ -404,10 +393,23 @@ int main(int argc, char **argv)
 		exit (EXIT_FAILURE);
 	}
 
-	make_pid (options.pidfile);
+	pidfd = open (options.pidfile,
+				  O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, 0660);
+	if (pidfd == -1) {
+		logger (LOG_ERR, "open `%s': %s", options.pidfile, strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+
+	/* Lock the file so that only one instance of dhcpcd runs on an interface */
+	if (flock (pidfd, LOCK_EX | LOCK_NB) == -1) {
+		logger (LOG_ERR, "flock `%s': %s", options.pidfile, strerror (errno));
+		exit (EXIT_FAILURE);
+	}
 
 	logger (LOG_INFO, PACKAGE " " VERSION " starting");
-	if (dhcp_run (&options)) {
+	if (dhcp_run (&options, &pidfd)) {
+		if (pidfd > -1)
+			close (pidfd);
 		unlink (options.pidfile);
 		exit (EXIT_FAILURE);
 	}
diff --git a/dhcpcd.h b/dhcpcd.h
index ff17bbc1..6b7af2d9 100644
--- a/dhcpcd.h
+++ b/dhcpcd.h
@@ -71,6 +71,4 @@ typedef struct options_t {
 	char pidfile[PATH_MAX];
 } options_t;
 
-void make_pid (const char *pidfile);
-
 #endif