rate limiting of accept() in various cases. Testing by jmatthew. there

maybe still be a corner case where it needs one more file descriptor
beyond the limit..

4 files changed, 72 insertions, 19 deletions

diff --git a/usr.sbin/ldapd/conn.c b/usr.sbin/ldapd/conn.c
index 6936086c221..e2ed882015e 100644
--- a/usr.sbin/ldapd/conn.c
+++ b/usr.sbin/ldapd/conn.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: conn.c,v 1.8 2010/11/10 08:00:54 martinh Exp $ */
+/*	$OpenBSD: conn.c,v 1.9 2012/04/11 08:31:37 deraadt Exp $ */
 
 /*
  * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
@@ -48,6 +48,7 @@ void
 conn_close(struct conn *conn)
 {
 	struct search	*search, *next;
+	struct listener *l = conn->listener;
 
 	log_debug("closing connection %d", conn->fd);
 
@@ -67,6 +68,13 @@ conn_close(struct conn *conn)
 	if (conn->bev != NULL)
 		bufferevent_free(conn->bev);
 	close(conn->fd);
+
+	/* Some file descriptors are available again. */
+	if (evtimer_pending(&l->evt, NULL)) {
+		evtimer_del(&l->evt);
+		event_add(&l->ev, NULL);
+	}
+
 	free(conn->binddn);
 	free(conn->pending_binddn);
 	free(conn);
@@ -239,7 +247,7 @@ conn_err(struct bufferevent *bev, short why, void *data)
 }
 
 void
-conn_accept(int fd, short why, void *data)
+conn_accept(int fd, short event, void *data)
 {
 	int			 afd;
 	socklen_t		 addrlen;
@@ -248,10 +256,24 @@ conn_accept(int fd, short why, void *data)
 	struct sockaddr_storage	 remote_addr;
 	char			 host[128];
 
+	event_add(&l->ev, NULL);
+	if ((event & EV_TIMEOUT))
+		return;
+
 	addrlen = sizeof(remote_addr);
 	afd = accept(fd, (struct sockaddr *)&remote_addr, &addrlen);
 	if (afd == -1) {
-		log_warn("accept");
+		/*
+		 * Pause accept if we are out of file descriptors, or
+		 * libevent will haunt us here too.
+		 */
+		if (errno == ENFILE || errno == EMFILE) {
+			struct timeval evtpause = { 1, 0 };
+
+			event_del(&l->ev);
+			evtimer_add(&l->evt, &evtpause);
+		} else if (errno != EWOULDBLOCK && errno != EINTR)
+			log_warn("conn_accept");
 		return;
 	}
 
@@ -272,8 +294,7 @@ conn_accept(int fd, short why, void *data)
 
 	if ((conn = calloc(1, sizeof(*conn))) == NULL) {
 		log_warn("malloc");
-		close(afd);
-		return;
+		goto giveup;
 	}
 	conn->ber.fd = -1;
 	conn->s_l = l;
@@ -288,9 +309,8 @@ conn_accept(int fd, short why, void *data)
 		    conn_err, conn);
 		if (conn->bev == NULL) {
 			log_warn("conn_accept: bufferevent_new");
-			close(afd);
 			free(conn);
-			return;
+			goto giveup;
 		}
 		bufferevent_enable(conn->bev, EV_READ);
 		bufferevent_settimeout(conn->bev, 0, 60);
@@ -303,6 +323,14 @@ conn_accept(int fd, short why, void *data)
 		conn->s_flags |= F_SECURE;
 
 	++stats.conns;
+	return;
+giveup:
+	close(afd);
+	/* Some file descriptors are available again. */
+	if (evtimer_pending(&l->evt, NULL)) {
+		evtimer_del(&l->evt);
+		event_add(&l->ev, NULL);
+	}
 }
 
 struct conn *
diff --git a/usr.sbin/ldapd/control.c b/usr.sbin/ldapd/control.c
index b32a5b1df79..74676e9f84b 100644
--- a/usr.sbin/ldapd/control.c
+++ b/usr.sbin/ldapd/control.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: control.c,v 1.6 2010/09/01 17:34:15 martinh Exp $	*/
+/*	$OpenBSD: control.c,v 1.7 2012/04/11 08:31:37 deraadt Exp $	*/
 
 /*
  * Copyright (c) 2010 Martin Hedenfalk <martin@bzero.se>
@@ -42,7 +42,7 @@
 struct ctl_connlist ctl_conns;
 
 struct ctl_conn	*control_connbyfd(int);
-void		 control_close(int);
+void		 control_close(int, struct control_sock *);
 static void	 control_imsgev(struct imsgev *iev, int code, struct imsg *imsg);
 
 void
@@ -102,9 +102,10 @@ control_listen(struct control_sock *cs)
 	if (listen(cs->cs_fd, CONTROL_BACKLOG) == -1)
 		fatal("control_listen: listen");
 
-	event_set(&cs->cs_ev, cs->cs_fd, EV_READ | EV_PERSIST,
+	event_set(&cs->cs_ev, cs->cs_fd, EV_READ,
 	    control_accept, cs);
 	event_add(&cs->cs_ev, NULL);
+	evtimer_set(&cs->cs_evt, control_accept, cs);
 }
 
 void
@@ -112,6 +113,8 @@ control_cleanup(struct control_sock *cs)
 {
 	if (cs->cs_name == NULL)
 		return;
+	event_del(&cs->cs_ev);
+	event_del(&cs->cs_evt);
 	(void)unlink(cs->cs_name);
 }
 
@@ -125,10 +128,23 @@ control_accept(int listenfd, short event, void *arg)
 	struct sockaddr_un	 sun;
 	struct ctl_conn		*c;
 
+	event_add(&cs->cs_ev, NULL);
+	if ((event & EV_TIMEOUT))
+		return;
+
 	len = sizeof(sun);
 	if ((connfd = accept(listenfd,
 	    (struct sockaddr *)&sun, &len)) == -1) {
-		if (errno != EWOULDBLOCK && errno != EINTR)
+		/*
+		 * Pause accept if we are out of file descriptors, or
+		 * libevent will haunt us here too.
+		 */
+		if (errno == ENFILE || errno == EMFILE) {
+			struct timeval evtpause = { 1, 0 };
+
+			event_del(&cs->cs_ev);
+			evtimer_add(&cs->cs_evt, &evtpause);
+		} else if (errno != EWOULDBLOCK && errno != EINTR)
 			log_warn("control_accept");
 		return;
 	}
@@ -159,7 +175,7 @@ control_connbyfd(int fd)
 }
 
 void
-control_close(int fd)
+control_close(int fd, struct control_sock *cs)
 {
 	struct ctl_conn	*c;
 
@@ -171,6 +187,13 @@ control_close(int fd)
 	log_debug("close control fd %i", c->iev.ibuf.fd);
 	TAILQ_REMOVE(&ctl_conns, c, entry);
 	imsgev_clear(&c->iev);
+
+	/* Some file descriptors are available again. */
+	if (evtimer_pending(&cs->cs_evt, NULL)) {
+		evtimer_del(&cs->cs_evt);
+		event_add(&cs->cs_ev, NULL);
+	}
+
 	free(c);
 }
 
@@ -220,7 +243,7 @@ control_imsgev(struct imsgev *iev, int code, struct imsg *imsg)
 	}
 
 	if (code != IMSGEV_IMSG) {
-		control_close(fd);
+		control_close(fd, cs);
 		return;
 	}
 
@@ -229,7 +252,7 @@ control_imsgev(struct imsgev *iev, int code, struct imsg *imsg)
 	case IMSG_CTL_STATS:
 		if (send_stats(iev) == -1) {
 			log_debug("%s: failed to send statistics", __func__);
-			control_close(fd);
+			control_close(fd, cs);
 		}
 		break;
 	case IMSG_CTL_LOG_VERBOSE:
diff --git a/usr.sbin/ldapd/ldapd.h b/usr.sbin/ldapd/ldapd.h
index d76e6f8ff45..b976ac60459 100644
--- a/usr.sbin/ldapd/ldapd.h
+++ b/usr.sbin/ldapd/ldapd.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ldapd.h,v 1.21 2010/11/10 08:00:54 martinh Exp $ */
+/*	$OpenBSD: ldapd.h,v 1.22 2012/04/11 08:31:37 deraadt Exp $ */
 
 /*
  * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
@@ -200,6 +200,7 @@ struct listener {
 	int			 port;
 	int			 fd;
 	struct event		 ev;
+	struct event		 evt;
 	char			 ssl_cert_name[PATH_MAX];
 	struct ssl		*ssl;
 	void			*ssl_ctx;
@@ -209,8 +210,7 @@ TAILQ_HEAD(listenerlist, listener);
 
 /* An LDAP client connection.
  */
-struct conn
-{
+struct conn {
 	TAILQ_ENTRY(conn)	 next;
 	int			 fd;
 	struct bufferevent	*bev;
@@ -323,6 +323,7 @@ extern  struct ctl_connlist ctl_conns;
 struct control_sock {
 	const char		*cs_name;
 	struct event		 cs_ev;
+	struct event		 cs_evt;
 	int			 cs_fd;
 	int			 cs_restricted;
 };
diff --git a/usr.sbin/ldapd/ldape.c b/usr.sbin/ldapd/ldape.c
index e799205be94..433bb2ad64f 100644
--- a/usr.sbin/ldapd/ldape.c
+++ b/usr.sbin/ldapd/ldape.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ldape.c,v 1.15 2012/04/01 16:20:00 deraadt Exp $ */
+/*	$OpenBSD: ldape.c,v 1.16 2012/04/11 08:31:37 deraadt Exp $ */
 
 /*
  * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
@@ -418,8 +418,9 @@ ldape(struct passwd *pw, char *csockpath, int pipe_parent2ldap[2])
 
 		fd_nonblock(l->fd);
 
-		event_set(&l->ev, l->fd, EV_READ|EV_PERSIST, conn_accept, l);
+		event_set(&l->ev, l->fd, EV_READ, conn_accept, l);
 		event_add(&l->ev, NULL);
+		evtimer_set(&l->evt, conn_accept, l);
 
 		ssl_setup(conf, l);
 	}