treewide: Suppress clang-tidy warning if we already use O_CLOEXEC

In pcap_init(), we should always open the packet capture file with
O_CLOEXEC, even if we're not running in foreground: O_CLOEXEC means
close-on-exec, not close-on-fork.

In logfile_init() and pidfile_open(), the fact that we pass a third
'mode' argument to open() seems to confuse the android-cloexec-open
checker in LLVM versions from 16 to 19 (at least).

The checker is suggesting to add O_CLOEXEC to 'mode', and not in
'flags', where we already have it.

Add a suppression for clang-tidy and a comment, and avoid repeating
those three times by adding a new helper, output_file_open().

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

conf.c

@@ -1194,7 +1194,11 @@ static void conf_open_files(struct ctx *c)
 	if (c->mode != MODE_PASTA && c->fd_tap == -1)
 		c->fd_tap_listen = tap_sock_unix_open(c->sock_path);
 
-	c->pidfile_fd = pidfile_open(c->pidfile);
+	if (*c->pidfile) {
+		c->pidfile_fd = output_file_open(c->pidfile, O_WRONLY);
+		if (c->pidfile_fd < 0)
+			die_perror("Couldn't open PID file %s", c->pidfile);
+	}
 }
 
 /**

log.c

@@ -416,8 +416,7 @@ void logfile_init(const char *name, const char *path, size_t size)
 	if (readlink("/proc/self/exe", exe, PATH_MAX - 1) < 0)
 		die_perror("Failed to read own /proc/self/exe link");
 
-	log_file = open(path, O_CREAT | O_TRUNC | O_APPEND | O_RDWR | O_CLOEXEC,
+	log_file = output_file_open(path, O_APPEND | O_RDWR);
-			S_IRUSR | S_IWUSR);
 	if (log_file == -1)
 		die_perror("Couldn't open log file %s", path);
 

pcap.c

@@ -158,18 +158,15 @@ void pcap_iov(const struct iovec *iov, size_t iovcnt, size_t offset)
  */
 void pcap_init(struct ctx *c)
 {
-	int flags = O_WRONLY | O_CREAT | O_TRUNC;
-
 	if (pcap_fd != -1)
 		return;
 
 	if (!*c->pcap)
 		return;
 
-	flags |= c->foreground ? O_CLOEXEC : 0;
+	pcap_fd = output_file_open(c->pcap, O_WRONLY);
-	pcap_fd = open(c->pcap, flags, S_IRUSR | S_IWUSR);
 	if (pcap_fd == -1) {
-		perror("open");
+		err_perror("Couldn't open pcap file %s", c->pcap);
 		return;
 	}
 

util.c

@@ -407,25 +407,20 @@ void pidfile_write(int fd, pid_t pid)
 }
 
 /**
- * pidfile_open() - Open PID file if needed
+ * output_file_open() - Open file for output, if needed
- * @path:	Path for PID file, empty string if no PID file is requested
+ * @path:	Path for output file
+ * @flags:	Flags for open() other than O_CREAT, O_TRUNC, O_CLOEXEC
  *
- * Return: descriptor for PID file, -1 if path is NULL, won't return on failure
+ * Return: file descriptor on success, -1 on failure with errno set by open()
  */
-int pidfile_open(const char *path)
+int output_file_open(const char *path, int flags)
 {
-	int fd;
+	/* We use O_CLOEXEC here, but clang-tidy as of LLVM 16 to 19 looks for
-
+	 * it in the 'mode' argument if we have one
-	if (!*path)
+	 */
-		return -1;
+	return open(path, O_CREAT | O_TRUNC | O_CLOEXEC | flags,
-
+		    /* NOLINTNEXTLINE(android-cloexec-open) */
-	if ((fd = open(path, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
+		    S_IRUSR | S_IWUSR);
-			     S_IRUSR | S_IWUSR)) < 0) {
-		perror("PID file open");
-		exit(EXIT_FAILURE);
-	}
-
-	return fd;
 }
 
 /**

util.h

@@ -193,7 +193,7 @@ char *line_read(char *buf, size_t len, int fd);
 void ns_enter(const struct ctx *c);
 bool ns_is_init(void);
 int open_in_ns(const struct ctx *c, const char *path, int flags);
-int pidfile_open(const char *path);
+int output_file_open(const char *path, int flags);
 void pidfile_write(int fd, pid_t pid);
 int __daemon(int pidfile_fd, int devnull_fd);
 int fls(unsigned long x);