Re-open ctrl_iface socket on some failure cases as a workaround

If wpa_supplicant ctrl_iface clients are misbehaving and refusing to
read replies or event messages from wpa_supplicant, the single socket
used in wpa_supplicant to send messages can reach the maximum send
buffer limit. When that happens, no more responses to any client can be
sent. Work around this by closed and reopening the socket in case such a
failure state is detected. This is obviously not desirable since it
breaks existing connected sockets, but is needed to avoid leaving
wpa_supplicant completely unable to respond to any client. Cleaner fix
for this may require more considerable changes in the ctrl_iface design
to move to connection oriented design to allow each client to be handled
separately and unreachability to be detected more reliably.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>

wpa_supplicant/ctrl_iface_unix.c

@@ -57,10 +57,17 @@ struct ctrl_iface_global_priv {
 };
 
 
-static void wpa_supplicant_ctrl_iface_send(const char *ifname, int sock,
+static void wpa_supplicant_ctrl_iface_send(struct wpa_supplicant *wpa_s,
+					   const char *ifname, int sock,
 					   struct dl_list *ctrl_dst,
 					   int level, const char *buf,
-					   size_t len);
+					   size_t len,
+					   struct ctrl_iface_priv *priv,
+					   struct ctrl_iface_global_priv *gp);
+static int wpas_ctrl_iface_reinit(struct wpa_supplicant *wpa_s,
+				  struct ctrl_iface_priv *priv);
+static int wpas_ctrl_iface_global_reinit(struct wpa_global *global,
+					 struct ctrl_iface_global_priv *priv);
 
 
 static int wpa_supplicant_ctrl_iface_attach(struct dl_list *ctrl_dst,
@@ -193,9 +200,30 @@ static void wpa_supplicant_ctrl_iface_receive(int sock, void *eloop_ctx,
 	if (reply) {
 		if (sendto(sock, reply, reply_len, 0, (struct sockaddr *) &from,
 			   fromlen) < 0) {
+			int _errno = errno;
 			wpa_dbg(wpa_s, MSG_DEBUG,
-				"ctrl_iface sendto failed: %s",
-				strerror(errno));
+				"ctrl_iface sendto failed: %d - %s",
+				_errno, strerror(_errno));
+			if (_errno == ENOBUFS || _errno == EAGAIN) {
+				/*
+				 * The socket send buffer could be full. This
+				 * may happen if client programs are not
+				 * receiving their pending messages. Close and
+				 * reopen the socket as a workaround to avoid
+				 * getting stuck being unable to send any new
+				 * responses.
+				 */
+				sock = wpas_ctrl_iface_reinit(wpa_s, priv);
+				if (sock < 0) {
+					wpa_dbg(wpa_s, MSG_DEBUG, "Failed to reinitialize ctrl_iface socket");
+				}
+			}
+			if (new_attached) {
+				wpa_dbg(wpa_s, MSG_DEBUG, "Failed to send response to ATTACH - detaching");
+				new_attached = 0;
+				wpa_supplicant_ctrl_iface_detach(
+					&priv->ctrl_dst, &from, fromlen);
+			}
 		}
 	}
 	os_free(reply_buf);
@@ -269,26 +297,27 @@ static void wpa_supplicant_ctrl_iface_msg_cb(void *ctx, int level, int global,
 	if (global != 2 && wpa_s->global->ctrl_iface) {
 		struct ctrl_iface_global_priv *priv = wpa_s->global->ctrl_iface;
 		if (!dl_list_empty(&priv->ctrl_dst)) {
-			wpa_supplicant_ctrl_iface_send(global ? NULL :
+			wpa_supplicant_ctrl_iface_send(wpa_s, global ? NULL :
 						       wpa_s->ifname,
 						       priv->sock,
 						       &priv->ctrl_dst,
-						       level, txt, len);
+						       level, txt, len, NULL,
+						       priv);
 		}
 	}
 
 	if (wpa_s->ctrl_iface == NULL)
 		return;
-	wpa_supplicant_ctrl_iface_send(NULL, wpa_s->ctrl_iface->sock,
+	wpa_supplicant_ctrl_iface_send(wpa_s, NULL, wpa_s->ctrl_iface->sock,
 				       &wpa_s->ctrl_iface->ctrl_dst,
-				       level, txt, len);
+				       level, txt, len, wpa_s->ctrl_iface,
+				       NULL);
 }
 
 
-struct ctrl_iface_priv *
-wpa_supplicant_ctrl_iface_init(struct wpa_supplicant *wpa_s)
+static int wpas_ctrl_iface_open_sock(struct wpa_supplicant *wpa_s,
+				     struct ctrl_iface_priv *priv)
 {
-	struct ctrl_iface_priv *priv;
 	struct sockaddr_un addr;
 	char *fname = NULL;
 	gid_t gid = 0;
@@ -298,16 +327,6 @@ wpa_supplicant_ctrl_iface_init(struct wpa_supplicant *wpa_s)
 	char *endp;
 	int flags;
 
-	priv = os_zalloc(sizeof(*priv));
-	if (priv == NULL)
-		return NULL;
-	dl_list_init(&priv->ctrl_dst);
-	priv->wpa_s = wpa_s;
-	priv->sock = -1;
-
-	if (wpa_s->conf->ctrl_interface == NULL)
-		return priv;
-
 	buf = os_strdup(wpa_s->conf->ctrl_interface);
 	if (buf == NULL)
 		goto fail;
@@ -483,18 +502,61 @@ havesock:
 	wpa_msg_register_cb(wpa_supplicant_ctrl_iface_msg_cb);
 
 	os_free(buf);
-	return priv;
+	return 0;
 
 fail:
-	if (priv->sock >= 0)
+	if (priv->sock >= 0) {
 		close(priv->sock);
-	os_free(priv);
+		priv->sock = -1;
+	}
 	if (fname) {
 		unlink(fname);
 		os_free(fname);
 	}
 	os_free(buf);
-	return NULL;
+	return -1;
+}
+
+
+struct ctrl_iface_priv *
+wpa_supplicant_ctrl_iface_init(struct wpa_supplicant *wpa_s)
+{
+	struct ctrl_iface_priv *priv;
+
+	priv = os_zalloc(sizeof(*priv));
+	if (priv == NULL)
+		return NULL;
+	dl_list_init(&priv->ctrl_dst);
+	priv->wpa_s = wpa_s;
+	priv->sock = -1;
+
+	if (wpa_s->conf->ctrl_interface == NULL)
+		return priv;
+
+	if (wpas_ctrl_iface_open_sock(wpa_s, priv) < 0) {
+		os_free(priv);
+		return NULL;
+	}
+
+	return priv;
+}
+
+
+static int wpas_ctrl_iface_reinit(struct wpa_supplicant *wpa_s,
+				  struct ctrl_iface_priv *priv)
+{
+	int res;
+
+	if (priv->sock <= 0)
+		return -1;
+
+	eloop_unregister_read_sock(priv->sock);
+	close(priv->sock);
+	priv->sock = -1;
+	res = wpas_ctrl_iface_open_sock(wpa_s, priv);
+	if (res < 0)
+		return -1;
+	return priv->sock;
 }
 
 
@@ -570,10 +632,13 @@ free_dst:
  *
  * Send a packet to all monitor programs attached to the control interface.
  */
-static void wpa_supplicant_ctrl_iface_send(const char *ifname, int sock,
+static void wpa_supplicant_ctrl_iface_send(struct wpa_supplicant *wpa_s,
+					   const char *ifname, int sock,
 					   struct dl_list *ctrl_dst,
 					   int level, const char *buf,
-					   size_t len)
+					   size_t len,
+					   struct ctrl_iface_priv *priv,
+					   struct ctrl_iface_global_priv *gp)
 {
 	struct wpa_ctrl_dst *dst, *next;
 	char levelstr[10];
@@ -609,31 +674,56 @@ static void wpa_supplicant_ctrl_iface_send(const char *ifname, int sock,
 	msg.msg_iov = io;
 	msg.msg_iovlen = idx;
 
-	idx = 0;
+	idx = -1;
 	dl_list_for_each_safe(dst, next, ctrl_dst, struct wpa_ctrl_dst, list) {
-		if (level >= dst->debug_level) {
-			wpa_hexdump(MSG_DEBUG, "CTRL_IFACE monitor send",
-				    (u8 *) dst->addr.sun_path, dst->addrlen -
-				    offsetof(struct sockaddr_un, sun_path));
-			msg.msg_name = (void *) &dst->addr;
-			msg.msg_namelen = dst->addrlen;
-			if (sendmsg(sock, &msg, MSG_DONTWAIT) < 0) {
-				int _errno = errno;
-				wpa_printf(MSG_INFO, "CTRL_IFACE monitor[%d]: "
-					   "%d - %s",
-					   idx, errno, strerror(errno));
-				dst->errors++;
-				if (dst->errors > 1000 ||
-				    (_errno != ENOBUFS && dst->errors > 10) ||
-				    _errno == ENOENT) {
-					wpa_supplicant_ctrl_iface_detach(
-						ctrl_dst, &dst->addr,
-						dst->addrlen);
-				}
-			} else
-				dst->errors = 0;
-		}
+		int _errno;
+
 		idx++;
+		if (level < dst->debug_level)
+			continue;
+
+		wpa_hexdump(MSG_DEBUG, "CTRL_IFACE monitor send",
+			    (u8 *) dst->addr.sun_path, dst->addrlen -
+			    offsetof(struct sockaddr_un, sun_path));
+		msg.msg_name = (void *) &dst->addr;
+		msg.msg_namelen = dst->addrlen;
+		if (sendmsg(sock, &msg, MSG_DONTWAIT) >= 0) {
+			dst->errors = 0;
+			idx++;
+			continue;
+		}
+
+		_errno = errno;
+		wpa_printf(MSG_INFO, "CTRL_IFACE monitor[%d]: %d - %s",
+			   idx, errno, strerror(errno));
+		dst->errors++;
+
+		if (dst->errors > 10 || _errno == ENOENT || _errno == EPERM) {
+			wpa_printf(MSG_INFO, "CTRL_IFACE: Detach monitor that cannot receive messages");
+			wpa_supplicant_ctrl_iface_detach(ctrl_dst, &dst->addr,
+							 dst->addrlen);
+		}
+
+		if (_errno == ENOBUFS || _errno == EAGAIN) {
+			/*
+			 * The socket send buffer could be full. This may happen
+			 * if client programs are not receiving their pending
+			 * messages. Close and reopen the socket as a workaround
+			 * to avoid getting stuck being unable to send any new
+			 * responses.
+			 */
+			if (priv)
+				sock = wpas_ctrl_iface_reinit(wpa_s, priv);
+			else if (gp)
+				sock = wpas_ctrl_iface_global_reinit(
+					wpa_s->global, gp);
+			else
+				break;
+			if (sock < 0) {
+				wpa_dbg(wpa_s, MSG_DEBUG,
+					"Failed to reinitialize ctrl_iface socket");
+			}
+		}
 	}
 }
 
@@ -752,24 +842,13 @@ static void wpa_supplicant_global_ctrl_iface_receive(int sock, void *eloop_ctx,
 }
 
 
-struct ctrl_iface_global_priv *
-wpa_supplicant_global_ctrl_iface_init(struct wpa_global *global)
+static int wpas_global_ctrl_iface_open_sock(struct wpa_global *global,
+					    struct ctrl_iface_global_priv *priv)
 {
-	struct ctrl_iface_global_priv *priv;
 	struct sockaddr_un addr;
 	const char *ctrl = global->params.ctrl_interface;
 	int flags;
 
-	priv = os_zalloc(sizeof(*priv));
-	if (priv == NULL)
-		return NULL;
-	dl_list_init(&priv->ctrl_dst);
-	priv->global = global;
-	priv->sock = -1;
-
-	if (ctrl == NULL)
-		return priv;
-
 	wpa_printf(MSG_DEBUG, "Global control interface '%s'", ctrl);
 
 #ifdef ANDROID
@@ -925,13 +1004,56 @@ havesock:
 				 wpa_supplicant_global_ctrl_iface_receive,
 				 global, priv);
 
-	return priv;
+	return 0;
 
 fail:
-	if (priv->sock >= 0)
+	if (priv->sock >= 0) {
 		close(priv->sock);
-	os_free(priv);
-	return NULL;
+		priv->sock = -1;
+	}
+	return -1;
+}
+
+
+struct ctrl_iface_global_priv *
+wpa_supplicant_global_ctrl_iface_init(struct wpa_global *global)
+{
+	struct ctrl_iface_global_priv *priv;
+
+	priv = os_zalloc(sizeof(*priv));
+	if (priv == NULL)
+		return NULL;
+	dl_list_init(&priv->ctrl_dst);
+	priv->global = global;
+	priv->sock = -1;
+
+	if (global->params.ctrl_interface == NULL)
+		return priv;
+
+	if (wpas_global_ctrl_iface_open_sock(global, priv) < 0) {
+		os_free(priv);
+		return NULL;
+	}
+
+	return priv;
+}
+
+
+static int wpas_ctrl_iface_global_reinit(struct wpa_global *global,
+					 struct ctrl_iface_global_priv *priv)
+{
+	int res;
+
+	if (priv->sock <= 0)
+		return -1;
+
+	eloop_unregister_read_sock(priv->sock);
+	close(priv->sock);
+	priv->sock = -1;
+	res = wpas_global_ctrl_iface_open_sock(global, priv);
+	if (res < 0)
+		return -1;
+	return priv->sock;
 }