dhcp/bugfix-dhcp-4.2.5-check-dhclient-pid.patch

--- a/client/dhclient.c	2019-01-25 14:34:46.996000000 +0800
+++ b/client/dhclient.c	2019-01-25 14:34:16.382000000 +0800
@@ -114,6 +114,8 @@
 
 int bootp_broadcast_always = 0;
 
+int buf_size = 128;
+
 extern struct option *default_requested_options[];
 
 void run_stateless(int exit_mode, u_int16_t port);
@@ -143,6 +143,7 @@ static void dhclient_ddns_cb_free(dhcp_ddns_cb_t *ddns_cb,
                                    char* file, int line);
 #endif /* defined NSUPDATE */

+static int check_dhclient_pid(pid_t pid);

 /*!
  *
@@ -682,7 +686,8 @@
 			e = fscanf(pidfd, "%ld\n", &temp);
 			oldpid = (pid_t)temp;
 
-			if (e != 0 && e != EOF && oldpid) {
+			if (e != 0 && e != EOF) {
+			 if (oldpid && check_dhclient_pid(oldpid)) {
 				if (kill(oldpid, SIGTERM) == 0) {
 					log_info("Killed old client process");
 					(void) unlink(path_dhclient_pid);
@@ -698,6 +703,7 @@
 					log_info("Removed stale PID file");
 					(void) unlink(path_dhclient_pid);
 				}
+				 }
 			}
 			fclose(pidfd);
 		} else {
@@ -738,7 +744,7 @@
 						oldpid = (pid_t)temp;
 
 						if (e != 0 && e != EOF) {
-							if (oldpid) {
+							if (oldpid && check_dhclient_pid(oldpid)) {
 								if (kill(oldpid, SIGTERM) == 0)
 									unlink(path_dhclient_pid);
 							}
@@ -6045,3 +6051,27 @@
 		log_error("dhcp4o6_stop: send(): %m");
 }
 #endif /* DHCPv6 && DHCP4o6 */
+
+static int check_dhclient_pid(pid_t pid) {
+	char proc_pid_path[buf_size];
+	char task_name[buf_size];
+
+	memset(proc_pid_path, 0, buf_size);
+	memset(task_name, 0, buf_size);
+
+	snprintf(proc_pid_path, buf_size - 1, "/proc/%d/comm", pid);
+
+	FILE* fp = fopen(proc_pid_path, "r");
+	if(fp != NULL) {
+		if( fgets(task_name, buf_size, fp) == NULL ) {
+			fclose(fp);
+			return 0;
+		 }
+		fclose(fp);
+		if(strncmp(task_name, "dhclient", 8) == 0) {
+			return 1;
+		}
+	}
+
+	 return 0;
+}