src/stream_interface.c

/*
 * Functions managing stream_interface structures
 *
 * Copyright 2000-2012 Willy Tarreau <w@1wt.eu>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 */

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>

#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <common/compat.h>
#include <common/config.h>
#include <common/debug.h>
#include <common/standard.h>
#include <common/ticks.h>
#include <common/time.h>

#include <proto/buffers.h>
#include <proto/connection.h>
#include <proto/fd.h>
#include <proto/frontend.h>
#include <proto/sock_raw.h>
#include <proto/stream_interface.h>
#include <proto/task.h>

#include <types/pipe.h>

/* socket functions used when running a stream interface as a task */
static void stream_int_update(struct stream_interface *si);
static void stream_int_update_embedded(struct stream_interface *si);
static void stream_int_chk_rcv(struct stream_interface *si);
static void stream_int_chk_snd(struct stream_interface *si);

/* socket operations for embedded tasks */
struct sock_ops stream_int_embedded = {
	.update  = stream_int_update_embedded,
	.shutr   = NULL,
	.shutw   = NULL,
	.chk_rcv = stream_int_chk_rcv,
	.chk_snd = stream_int_chk_snd,
	.read    = NULL,
	.write   = NULL,
	.close   = NULL,
};

/* socket operations for external tasks */
struct sock_ops stream_int_task = {
	.update  = stream_int_update,
	.shutr   = NULL,
	.shutw   = NULL,
	.chk_rcv = stream_int_chk_rcv,
	.chk_snd = stream_int_chk_snd,
	.read    = NULL,
	.write   = NULL,
	.close   = NULL,
};

/*
 * This function only has to be called once after a wakeup event in case of
 * suspected timeout. It controls the stream interface timeouts and sets
 * si->flags accordingly. It does NOT close anything, as this timeout may
 * be used for any purpose. It returns 1 if the timeout fired, otherwise
 * zero.
 */
int stream_int_check_timeouts(struct stream_interface *si)
{
	if (tick_is_expired(si->exp, now_ms)) {
		si->flags |= SI_FL_EXP;
		return 1;
	}
	return 0;
}

/* to be called only when in SI_ST_DIS with SI_FL_ERR */
void stream_int_report_error(struct stream_interface *si)
{
	if (!si->err_type)
		si->err_type = SI_ET_DATA_ERR;

	si->ob->flags |= BF_WRITE_ERROR;
	si->ib->flags |= BF_READ_ERROR;
}

/*
 * Returns a message to the client ; the connection is shut down for read,
 * and the request is cleared so that no server connection can be initiated.
 * The buffer is marked for read shutdown on the other side to protect the
 * message, and the buffer write is enabled. The message is contained in a
 * "chunk". If it is null, then an empty message is used. The reply buffer does
 * not need to be empty before this, and its contents will not be overwritten.
 * The primary goal of this function is to return error messages to a client.
 */
void stream_int_retnclose(struct stream_interface *si, const struct chunk *msg)
{
	buffer_auto_read(si->ib);
	buffer_abort(si->ib);
	buffer_auto_close(si->ib);
	buffer_erase(si->ib);

	bi_erase(si->ob);
	if (likely(msg && msg->len))
		bo_inject(si->ob, msg->str, msg->len);

	si->ob->wex = tick_add_ifset(now_ms, si->ob->wto);
	buffer_auto_read(si->ob);
	buffer_auto_close(si->ob);
	buffer_shutr_now(si->ob);
}

/* default update function for scheduled tasks, not used for embedded tasks */
static void stream_int_update(struct stream_interface *si)
{
	DPRINTF(stderr, "%s: si=%p, si->state=%d ib->flags=%08x ob->flags=%08x\n",
		__FUNCTION__,
		si, si->state, si->ib->flags, si->ob->flags);

	if (!(si->flags & SI_FL_DONT_WAKE) && si->owner)
		task_wakeup(si->owner, TASK_WOKEN_IO);
}

/* default update function for embedded tasks, to be used at the end of the i/o handler */
static void stream_int_update_embedded(struct stream_interface *si)
{
	int old_flags = si->flags;

	DPRINTF(stderr, "%s: si=%p, si->state=%d ib->flags=%08x ob->flags=%08x\n",
		__FUNCTION__,
		si, si->state, si->ib->flags, si->ob->flags);

	if (si->state != SI_ST_EST)
		return;

	if ((si->ob->flags & (BF_OUT_EMPTY|BF_SHUTW|BF_HIJACK|BF_SHUTW_NOW)) == (BF_OUT_EMPTY|BF_SHUTW_NOW))
		si_shutw(si);

	if ((si->ob->flags & (BF_FULL|BF_SHUTW|BF_SHUTW_NOW|BF_HIJACK)) == 0)
		si->flags |= SI_FL_WAIT_DATA;

	/* we're almost sure that we need some space if the buffer is not
	 * empty, even if it's not full, because the applets can't fill it.
	 */
	if ((si->ib->flags & (BF_SHUTR|BF_OUT_EMPTY|BF_DONT_READ)) == 0)
		si->flags |= SI_FL_WAIT_ROOM;

	if (si->ob->flags & BF_WRITE_ACTIVITY) {
		if (tick_isset(si->ob->wex))
			si->ob->wex = tick_add_ifset(now_ms, si->ob->wto);
	}

	if (si->ib->flags & BF_READ_ACTIVITY ||
	    (si->ob->flags & BF_WRITE_ACTIVITY && !(si->flags & SI_FL_INDEP_STR))) {
		if (tick_isset(si->ib->rex))
			si->ib->rex = tick_add_ifset(now_ms, si->ib->rto);
	}

	/* save flags to detect changes */
	old_flags = si->flags;
	if (likely((si->ob->flags & (BF_SHUTW|BF_WRITE_PARTIAL|BF_FULL|BF_DONT_READ)) == BF_WRITE_PARTIAL &&
		   (si->ob->prod->flags & SI_FL_WAIT_ROOM)))
		si_chk_rcv(si->ob->prod);

	if (((si->ib->flags & (BF_READ_PARTIAL|BF_OUT_EMPTY)) == BF_READ_PARTIAL) &&
	    (si->ib->cons->flags & SI_FL_WAIT_DATA)) {
		si_chk_snd(si->ib->cons);
		/* check if the consumer has freed some space */
		if (!(si->ib->flags & BF_FULL))
			si->flags &= ~SI_FL_WAIT_ROOM;
	}

	/* Note that we're trying to wake up in two conditions here :
	 *  - special event, which needs the holder task attention
	 *  - status indicating that the applet can go on working. This
	 *    is rather hard because we might be blocking on output and
	 *    don't want to wake up on input and vice-versa. The idea is
	 *    to only rely on the changes the chk_* might have performed.
	 */
	if (/* check stream interface changes */
	    ((old_flags & ~si->flags) & (SI_FL_WAIT_ROOM|SI_FL_WAIT_DATA)) ||

	    /* changes on the production side */
	    (si->ib->flags & (BF_READ_NULL|BF_READ_ERROR)) ||
	    si->state != SI_ST_EST ||
	    (si->flags & SI_FL_ERR) ||
	    ((si->ib->flags & BF_READ_PARTIAL) &&
	     (!si->ib->to_forward || si->ib->cons->state != SI_ST_EST)) ||

	    /* changes on the consumption side */
	    (si->ob->flags & (BF_WRITE_NULL|BF_WRITE_ERROR)) ||
	    ((si->ob->flags & BF_WRITE_ACTIVITY) &&
	     ((si->ob->flags & BF_SHUTW) ||
	      si->ob->prod->state != SI_ST_EST ||
	      ((si->ob->flags & BF_OUT_EMPTY) && !si->ob->to_forward)))) {
		if (!(si->flags & SI_FL_DONT_WAKE) && si->owner)
			task_wakeup(si->owner, TASK_WOKEN_IO);
	}
	if (si->ib->flags & BF_READ_ACTIVITY)
		si->ib->flags &= ~BF_READ_DONTWAIT;
}

/*
 * This function performs a shutdown-read on a stream interface in a connected
 * or init state (it does nothing for other states). It either shuts the read
 * side or marks itself as closed. The buffer flags are updated to reflect the
 * new state. If the stream interface has SI_FL_NOHALF, we also forward the
 * close to the write side. If a control layer is defined, then it is supposed
 * to be a socket layer and file descriptors are then shutdown or closed
 * accordingly. If no control layer is defined, then the SI is supposed to be
 * an embedded one and the owner task is woken up if it exists. The function
 * does not disable polling on the FD by itself, it returns non-zero instead
 * if the caller needs to do so (except when the FD is deleted where this is
 * implicit).
 */
int stream_int_shutr(struct stream_interface *si)
{
	struct connection *conn = &si->conn;

	si->ib->flags &= ~BF_SHUTR_NOW;
	if (si->ib->flags & BF_SHUTR)
		return 0;
	si->ib->flags |= BF_SHUTR;
	si->ib->rex = TICK_ETERNITY;
	si->flags &= ~SI_FL_WAIT_ROOM;

	if (si->state != SI_ST_EST && si->state != SI_ST_CON)
		return 0;

	if (si->ob->flags & BF_SHUTW) {
		conn_data_close(&si->conn);
		if (conn->ctrl)
			fd_delete(si_fd(si));
		si->state = SI_ST_DIS;
		si->exp = TICK_ETERNITY;

		if (si->release)
			si->release(si);
	}
	else if (si->flags & SI_FL_NOHALF) {
		/* we want to immediately forward this close to the write side */
		return stream_int_shutw(si);
	}
	else if (conn->ctrl) {
		/* we want the caller to disable polling on this FD */
		return 1;
	}

	/* note that if the task exists, it must unregister itself once it runs */
	if (!conn->ctrl && !(si->flags & SI_FL_DONT_WAKE) && si->owner)
		task_wakeup(si->owner, TASK_WOKEN_IO);
	return 0;
}

/*
 * This function performs a shutdown-write on a stream interface in a connected or
 * init state (it does nothing for other states). It either shuts the write side
 * or marks itself as closed. The buffer flags are updated to reflect the new state.
 * It does also close everything if the SI was marked as being in error state. If
 * there is a data-layer shutdown, it is called. If a control layer is defined, then
 * it is supposed to be a socket layer and file descriptors are then shutdown or
 * closed accordingly. If no control layer is defined, then the SI is supposed to
 * be an embedded one and the owner task is woken up if it exists. The function
 * does not disable polling on the FD by itself, it returns non-zero instead if
 * the caller needs to do so (except when the FD is deleted where this is implicit).
 */
int stream_int_shutw(struct stream_interface *si)
{
	struct connection *conn = &si->conn;

	si->ob->flags &= ~BF_SHUTW_NOW;
	if (si->ob->flags & BF_SHUTW)
		return 0;
	si->ob->flags |= BF_SHUTW;
	si->ob->wex = TICK_ETERNITY;
	si->flags &= ~SI_FL_WAIT_DATA;

	switch (si->state) {
	case SI_ST_EST:
		/* we have to shut before closing, otherwise some short messages
		 * may never leave the system, especially when there are remaining
		 * unread data in the socket input buffer, or when nolinger is set.
		 * However, if SI_FL_NOLINGER is explicitly set, we know there is
		 * no risk so we close both sides immediately.
		 */
		if (si->flags & SI_FL_ERR) {
			/* quick close, the socket is already shut. Remove pending flags. */
			si->flags &= ~SI_FL_NOLINGER;
		} else if (si->flags & SI_FL_NOLINGER) {
			si->flags &= ~SI_FL_NOLINGER;
			if (conn->ctrl) {
				setsockopt(si_fd(si), SOL_SOCKET, SO_LINGER,
					   (struct linger *) &nolinger, sizeof(struct linger));
			}
			/* unclean data-layer shutdown */
			if (conn->data && conn->data->shutw)
				conn->data->shutw(conn, 0);
		} else {
			/* clean data-layer shutdown */
			if (conn->data && conn->data->shutw)
				conn->data->shutw(conn, 1);

			if (!(si->flags & SI_FL_NOHALF)) {
				/* We shutdown transport layer */
				if (conn->ctrl)
					shutdown(si_fd(si), SHUT_WR);

				if (!(si->ib->flags & (BF_SHUTR|BF_DONT_READ))) {
					/* OK just a shutw, but we want the caller
					 * to disable polling on this FD if exists.
					 */
					return !!conn->ctrl;
				}
			}
		}

		/* fall through */
	case SI_ST_CON:
		/* we may have to close a pending connection, and mark the
		 * response buffer as shutr
		 */
		conn_data_close(&si->conn);
		if (conn->ctrl)
			fd_delete(si_fd(si));
		/* fall through */
	case SI_ST_CER:
	case SI_ST_QUE:
	case SI_ST_TAR:
		si->state = SI_ST_DIS;

		if (si->release)
			si->release(si);
	default:
		si->flags &= ~SI_FL_WAIT_ROOM;
		si->ib->flags |= BF_SHUTR;
		si->ib->rex = TICK_ETERNITY;
		si->exp = TICK_ETERNITY;
	}

	/* note that if the task exists, it must unregister itself once it runs */
	if (!conn->ctrl && !(si->flags & SI_FL_DONT_WAKE) && si->owner)
		task_wakeup(si->owner, TASK_WOKEN_IO);
	return 0;
}

/* default chk_rcv function for scheduled tasks */
static void stream_int_chk_rcv(struct stream_interface *si)
{
	struct buffer *ib = si->ib;

	DPRINTF(stderr, "%s: si=%p, si->state=%d ib->flags=%08x ob->flags=%08x\n",
		__FUNCTION__,
		si, si->state, si->ib->flags, si->ob->flags);

	if (unlikely(si->state != SI_ST_EST || (ib->flags & BF_SHUTR)))
		return;

	if (ib->flags & (BF_FULL|BF_HIJACK|BF_DONT_READ)) {
		/* stop reading */
		if ((ib->flags & (BF_FULL|BF_HIJACK|BF_DONT_READ)) == BF_FULL)
			si->flags |= SI_FL_WAIT_ROOM;
	}
	else {
		/* (re)start reading */
		si->flags &= ~SI_FL_WAIT_ROOM;
		if (!(si->flags & SI_FL_DONT_WAKE) && si->owner)
			task_wakeup(si->owner, TASK_WOKEN_IO);
	}
}

/* default chk_snd function for scheduled tasks */
static void stream_int_chk_snd(struct stream_interface *si)
{
	struct buffer *ob = si->ob;

	DPRINTF(stderr, "%s: si=%p, si->state=%d ib->flags=%08x ob->flags=%08x\n",
		__FUNCTION__,
		si, si->state, si->ib->flags, si->ob->flags);

	if (unlikely(si->state != SI_ST_EST || (si->ob->flags & BF_SHUTW)))
		return;

	if (!(si->flags & SI_FL_WAIT_DATA) ||        /* not waiting for data */
	    (ob->flags & BF_OUT_EMPTY))              /* called with nothing to send ! */
		return;

	/* Otherwise there are remaining data to be sent in the buffer,
	 * so we tell the handler.
	 */
	si->flags &= ~SI_FL_WAIT_DATA;
	if (!tick_isset(ob->wex))
		ob->wex = tick_add_ifset(now_ms, ob->wto);

	if (!(si->flags & SI_FL_DONT_WAKE) && si->owner)
		task_wakeup(si->owner, TASK_WOKEN_IO);
}

/* Register an applet to handle a stream_interface as part of the stream
 * interface's owner task, which is returned. The SI will wake it up everytime
 * it is solicited. The task's processing function must call the applet's
 * function before returning. It must be deleted by the task handler using
 * stream_int_unregister_handler(), possibly from within the function itself.
 * It also pre-initializes applet.state to zero and the connection context
 * to NULL.
 */
struct task *stream_int_register_handler(struct stream_interface *si, struct si_applet *app)
{
	DPRINTF(stderr, "registering handler %p for si %p (was %p)\n", app, si, si->owner);

	stream_interface_prepare(si, &stream_int_embedded);
	si->conn.ctrl = NULL;
	set_target_applet(&si->target, app);
	si->release   = app->release;
	si->flags |= SI_FL_WAIT_DATA;
	return si->owner;
}

/* Register a function to handle a stream_interface as a standalone task. The
 * new task itself is returned and is assigned as si->owner. The stream_interface
 * pointer will be pointed to by the task's context. The handler can be detached
 * by using stream_int_unregister_handler().
 * FIXME: the code should be updated to ensure that we don't change si->owner
 * anymore as this is not needed. However, process_session still relies on it.
 */
struct task *stream_int_register_handler_task(struct stream_interface *si,
					      struct task *(*fct)(struct task *))
{
	struct task *t;

	DPRINTF(stderr, "registering handler %p for si %p (was %p)\n", fct, si, si->owner);

	stream_interface_prepare(si, &stream_int_task);
	si->conn.ctrl = NULL;
	clear_target(&si->target);
	si->release   = NULL;
	si->flags |= SI_FL_WAIT_DATA;

	t = task_new();
	si->owner = t;
	if (!t)
		return t;

	set_target_task(&si->target, t);

	t->process = fct;
	t->context = si;
	task_wakeup(si->owner, TASK_WOKEN_INIT);

	return t;
}

/* Unregister a stream interface handler. This must be called by the handler task
 * itself when it detects that it is in the SI_ST_DIS state. This function can
 * both detach standalone handlers and embedded handlers.
 */
void stream_int_unregister_handler(struct stream_interface *si)
{
	if (si->target.type == TARG_TYPE_TASK) {
		/* external handler : kill the task */
		task_delete(si->target.ptr.t);
		task_free(si->target.ptr.t);
	}
	si->release   = NULL;
	si->owner = NULL;
	clear_target(&si->target);
}

/* This callback is used to send a valid PROXY protocol line to a socket being
 * established. It returns a combination of FD_WAIT_* if it wants some polling
 * before being called again, otherwise it returns zero and removes itself from
 * the connection's flags (the bit is provided in <flag> by the caller).
 */
int conn_si_send_proxy(struct connection *conn, unsigned int flag)
{
	int fd = conn->t.sock.fd;
	struct stream_interface *si = container_of(conn, struct stream_interface, conn);
	struct buffer *b = si->ob;

	/* we might have been called just after an asynchronous shutw */
	if (b->flags & BF_SHUTW)
		goto out_error;

	/* If we have a PROXY line to send, we'll use this to validate the
	 * connection, in which case the connection is validated only once
	 * we've sent the whole proxy line. Otherwise we use connect().
	 */
	if (si->send_proxy_ofs) {
		int ret;

		/* The target server expects a PROXY line to be sent first.
		 * If the send_proxy_ofs is negative, it corresponds to the
		 * offset to start sending from then end of the proxy string
		 * (which is recomputed every time since it's constant). If
		 * it is positive, it means we have to send from the start.
		 */
		ret = make_proxy_line(trash, trashlen, &b->prod->addr.from, &b->prod->addr.to);
		if (!ret)
			goto out_error;

		if (si->send_proxy_ofs > 0)
			si->send_proxy_ofs = -ret; /* first call */

		/* we have to send trash from (ret+sp for -sp bytes) */
		ret = send(fd, trash + ret + si->send_proxy_ofs, -si->send_proxy_ofs,
			   (b->flags & BF_OUT_EMPTY) ? 0 : MSG_MORE);

		if (ret == 0)
			goto out_wait;

		if (ret < 0) {
			if (errno == EAGAIN)
				goto out_wait;
			goto out_error;
		}

		si->send_proxy_ofs += ret; /* becomes zero once complete */
		if (si->send_proxy_ofs != 0)
			goto out_wait;

		/* OK we've sent the whole line, we're connected */
	}

	/* The FD is ready now, simply return and let the connection handler
	 * notify upper layers if needed.
	 */
	if (conn->flags & CO_FL_WAIT_L4_CONN)
		conn->flags &= ~CO_FL_WAIT_L4_CONN;
	b->flags |= BF_WRITE_NULL;
	si->exp = TICK_ETERNITY;

 out_leave:
	conn->flags &= ~flag;
	return 0;

 out_error:
	/* Write error on the file descriptor. We mark the FD as STERROR so
	 * that we don't use it anymore. The error is reported to the stream
	 * interface which will take proper action. We must not perturbate the
	 * buffer because the stream interface wants to ensure transparent
	 * connection retries.
	 */

	conn->flags |= CO_FL_ERROR;
	fdtab[fd].ev &= ~FD_POLL_STICKY;
	conn_sock_stop_both(conn);
	goto out_leave;

 out_wait:
	conn_sock_stop_recv(conn);
	conn_sock_poll_send(conn);
	return FD_WAIT_WRITE;
}

/* function to be called on stream sockets after all I/O handlers */
void stream_sock_update_conn(struct connection *conn)
{
	int fd = conn->t.sock.fd;
	struct stream_interface *si = container_of(conn, struct stream_interface, conn);

	DPRINTF(stderr, "%s: si=%p, si->state=%d ib->flags=%08x ob->flags=%08x\n",
		__FUNCTION__,
		si, si->state, si->ib->flags, si->ob->flags);

	if (conn->flags & CO_FL_ERROR)
		si->flags |= SI_FL_ERR;

	/* check for recent connection establishment */
	if (unlikely(!(conn->flags & (CO_FL_WAIT_L4_CONN | CO_FL_WAIT_L6_CONN | CO_FL_CONNECTED)))) {
		si->exp = TICK_ETERNITY;
		si->ob->flags |= BF_WRITE_NULL;
	}

	/* process consumer side, only once if possible */
	if (fdtab[fd].ev & (FD_POLL_OUT | FD_POLL_ERR)) {
		if (si->ob->flags & BF_OUT_EMPTY) {
			if (((si->ob->flags & (BF_SHUTW|BF_HIJACK|BF_SHUTW_NOW)) == BF_SHUTW_NOW) &&
			    (si->state == SI_ST_EST))
				stream_int_shutw(si);
			conn_data_stop_send(conn);
			si->ob->wex = TICK_ETERNITY;
		}

		if ((si->ob->flags & (BF_FULL|BF_SHUTW|BF_SHUTW_NOW|BF_HIJACK)) == 0)
			si->flags |= SI_FL_WAIT_DATA;

		if (si->ob->flags & BF_WRITE_ACTIVITY) {
			/* update timeouts if we have written something */
			if ((si->ob->flags & (BF_OUT_EMPTY|BF_SHUTW|BF_WRITE_PARTIAL)) == BF_WRITE_PARTIAL)
				if (tick_isset(si->ob->wex))
					si->ob->wex = tick_add_ifset(now_ms, si->ob->wto);

			if (!(si->flags & SI_FL_INDEP_STR))
				if (tick_isset(si->ib->rex))
					si->ib->rex = tick_add_ifset(now_ms, si->ib->rto);

			if (likely((si->ob->flags & (BF_SHUTW|BF_WRITE_PARTIAL|BF_FULL|BF_DONT_READ)) == BF_WRITE_PARTIAL &&
			           (si->ob->prod->flags & SI_FL_WAIT_ROOM)))
				si_chk_rcv(si->ob->prod);
		}
	}

	/* process producer side, only once if possible */
	if (fdtab[fd].ev & (FD_POLL_IN | FD_POLL_HUP | FD_POLL_ERR)) {
		/* We might have some data the consumer is waiting for.
		 * We can do fast-forwarding, but we avoid doing this for partial
		 * buffers, because it is very likely that it will be done again
		 * immediately afterwards once the following data is parsed (eg:
		 * HTTP chunking).
		 */
		if (((si->ib->flags & (BF_READ_PARTIAL|BF_OUT_EMPTY)) == BF_READ_PARTIAL) &&
		    (si->ib->pipe /* always try to send spliced data */ ||
		     (si->ib->i == 0 && (si->ib->cons->flags & SI_FL_WAIT_DATA)))) {
			int last_len = si->ib->pipe ? si->ib->pipe->data : 0;

			si_chk_snd(si->ib->cons);

			/* check if the consumer has freed some space */
			if (!(si->ib->flags & BF_FULL) &&
			    (!last_len || !si->ib->pipe || si->ib->pipe->data < last_len))
				si->flags &= ~SI_FL_WAIT_ROOM;
		}

		if (si->flags & SI_FL_WAIT_ROOM) {
			conn_data_stop_recv(conn);
			si->ib->rex = TICK_ETERNITY;
		}
		else if ((si->ib->flags & (BF_SHUTR|BF_READ_PARTIAL|BF_FULL|BF_DONT_READ|BF_READ_NOEXP)) == BF_READ_PARTIAL) {
			if (tick_isset(si->ib->rex))
				si->ib->rex = tick_add_ifset(now_ms, si->ib->rto);
		}
	}

	/* wake the task up only when needed */
	if (/* changes on the production side */
	    (si->ib->flags & (BF_READ_NULL|BF_READ_ERROR)) ||
	    si->state != SI_ST_EST ||
	    (si->flags & SI_FL_ERR) ||
	    ((si->ib->flags & BF_READ_PARTIAL) &&
	     (!si->ib->to_forward || si->ib->cons->state != SI_ST_EST)) ||

	    /* changes on the consumption side */
	    (si->ob->flags & (BF_WRITE_NULL|BF_WRITE_ERROR)) ||
	    ((si->ob->flags & BF_WRITE_ACTIVITY) &&
	     ((si->ob->flags & BF_SHUTW) ||
	      si->ob->prod->state != SI_ST_EST ||
	      ((si->ob->flags & BF_OUT_EMPTY) && !si->ob->to_forward)))) {
		task_wakeup(si->owner, TASK_WOKEN_IO);
	}
	if (si->ib->flags & BF_READ_ACTIVITY)
		si->ib->flags &= ~BF_READ_DONTWAIT;
}

/*
 * Local variables:
 *  c-indent-level: 8
 *  c-basic-offset: 8
 * End:
 */