Don't spin if accept() fails because it is out of file descriptors,

instead set a flag that skips the listening socket from the poll()
event loop. The flag is cleared whenever a file descriptor is closed
allowing accept() to be retried.
Explained by deraadt@

aucat/file.c

@@ -73,6 +73,7 @@ struct timespec file_ts;
 struct filelist file_list;
 struct timo *timo_queue;
 unsigned timo_abstime;
+int file_slowaccept = 0;
 #ifdef DEBUG
 long long file_wtime, file_utime;
 #endif

aucat/file.h

@@ -68,6 +68,7 @@ struct file {
 LIST_HEAD(filelist,file);
 
 extern struct filelist file_list;
+extern int file_slowaccept;
 
 #ifdef DEBUG
 extern long long file_wtime, file_utime;

aucat/listen.c

@@ -175,6 +175,8 @@ listen_pollfd(struct file *file, struct pollfd *pfd, int events)
 {
 	struct listen *f = (struct listen *)file;
 
+	if (file_slowaccept)
+		return 0;
 	pfd->fd = f->fd;
 	pfd->events = POLLIN;
 	return 1;
@@ -190,10 +192,13 @@ listen_revents(struct file *file, struct pollfd *pfd)
 
 	if (pfd->revents & POLLIN) {
 		caddrlen = sizeof(caddrlen);
-		sock = accept(f->fd, &caddr, &caddrlen);
-		if (sock < 0) {
-			/* XXX: should we kill the socket here ? */
-			perror("accept");
+		while ((sock = accept(f->fd, &caddr, &caddrlen)) < 0) {
+			if (errno == EINTR)
+				continue;
+			if (errno == ENFILE || errno == EMFILE)
+				file_slowaccept = 1;
+			else
+				perror("accept");
 			return 0;
 		}
 		if (fcntl(sock, F_SETFL, O_NONBLOCK) < 0) {

aucat/pipe.c

@@ -139,6 +139,7 @@ pipe_close(struct file *file)
 	struct pipe *f = (struct pipe *)file;
 
 	close(f->fd);
+	file_slowaccept = 0;
 }
 
 off_t