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When changing so that the client passes its stdout and stderr as well as
stdin up to the server, I forgot one essential point - the tmux server
could now be both the producer and consumer. This happens when tmux is
run inside tmux, as well as when piping tmux commands together.

So, using stdio(3) was a bad idea - if sufficient data was written, this
could block in write(2). When that happened and the server was both
producer and consumer, it deadlocks.

Change to use libevent bufferevents for the client stdin, stdout and
stderr instead. This is trivial enough for output but requires a
callback mechanism to trigger when stdin is finished.

This relies on the underlying polling mechanism for libevent to work
with whatever devices to which the user could redirect stdin, stdout or
stderr, hence the change to use poll(2) over kqueue(2) for tmux.

/* $OpenBSD: server-fn.c,v 1.40 2010/07/24 20:11:59 nicm Exp $ */

/*
 * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>

#include <string.h>
#include <time.h>
#include <unistd.h>

#include "tmux.h"

struct session *server_next_session(struct session *);
void		server_callback_identify(int, short, void *);

void
server_fill_environ(struct session *s, struct environ *env)
{
	char		 tmuxvar[MAXPATHLEN], *term;
	u_int		 idx;

	if (session_index(s, &idx) != 0)
		fatalx("session not found");
	xsnprintf(tmuxvar, sizeof tmuxvar,
	    "%s,%ld,%u", socket_path, (long) getpid(), idx);
	environ_set(env, "TMUX", tmuxvar);

	term = options_get_string(&s->options, "default-terminal");
	environ_set(env, "TERM", term);
}

void
server_write_client(
    struct client *c, enum msgtype type, const void *buf, size_t len)
{
	struct imsgbuf	*ibuf = &c->ibuf;

	if (c->flags & CLIENT_BAD)
		return;
	log_debug("writing %d to client %d", type, c->ibuf.fd);
	imsg_compose(ibuf, type, PROTOCOL_VERSION, -1, -1, (void *) buf, len);
	server_update_event(c);
}

void
server_write_session(
    struct session *s, enum msgtype type, const void *buf, size_t len)
{
	struct client	*c;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL)
			continue;
		if (c->session == s)
			server_write_client(c, type, buf, len);
	}
}

void
server_redraw_client(struct client *c)
{
	c->flags |= CLIENT_REDRAW;
}

void
server_status_client(struct client *c)
{
	c->flags |= CLIENT_STATUS;
}

void
server_redraw_session(struct session *s)
{
	struct client	*c;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL)
			continue;
		if (c->session == s)
			server_redraw_client(c);
	}
}

void
server_redraw_session_group(struct session *s)
{
	struct session_group	*sg;

	if ((sg = session_group_find(s)) == NULL)
		server_redraw_session(s);
	else {
		TAILQ_FOREACH(s, &sg->sessions, gentry)
			server_redraw_session(s);
	}
}

void
server_status_session(struct session *s)
{
	struct client	*c;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL)
			continue;
		if (c->session == s)
			server_status_client(c);
	}
}

void
server_status_session_group(struct session *s)
{
	struct session_group	*sg;

	if ((sg = session_group_find(s)) == NULL)
		server_status_session(s);
	else {
		TAILQ_FOREACH(s, &sg->sessions, gentry)
			server_status_session(s);
	}
}

void
server_redraw_window(struct window *w)
{
	struct client	*c;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL)
			continue;
		if (c->session->curw->window == w)
			server_redraw_client(c);
	}
	w->flags |= WINDOW_REDRAW;
}

void
server_redraw_window_borders(struct window *w)
{
	struct client	*c;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL)
			continue;
		if (c->session->curw->window == w)
			c->flags |= CLIENT_BORDERS;
	}
}

void
server_status_window(struct window *w)
{
	struct session	*s;
	u_int		 i;

	/*
	 * This is slightly different. We want to redraw the status line of any
	 * clients containing this window rather than any where it is the
	 * current window.
	 */

	for (i = 0; i < ARRAY_LENGTH(&sessions); i++) {
		s = ARRAY_ITEM(&sessions, i);
		if (s != NULL && session_has(s, w) != NULL)
			server_status_session(s);
	}
}

void
server_lock(void)
{
	struct client	*c;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL)
			continue;
		server_lock_client(c);
	}
}

void
server_lock_session(struct session *s)
{
	struct client	*c;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session == NULL || c->session != s)
			continue;
		server_lock_client(c);
	}
}

void
server_lock_client(struct client *c)
{
	const char		*cmd;
	size_t			 cmdlen;
	struct msg_lock_data	 lockdata;

	if (c->flags & CLIENT_SUSPENDED)
		return;

	cmd = options_get_string(&c->session->options, "lock-command");
	cmdlen = strlcpy(lockdata.cmd, cmd, sizeof lockdata.cmd);
	if (cmdlen >= sizeof lockdata.cmd)
		return;

	tty_stop_tty(&c->tty);
	tty_raw(&c->tty, tty_term_string(c->tty.term, TTYC_SMCUP));
	tty_raw(&c->tty, tty_term_string(c->tty.term, TTYC_CLEAR));

	c->flags |= CLIENT_SUSPENDED;
	server_write_client(c, MSG_LOCK, &lockdata, sizeof lockdata);
}

void
server_kill_window(struct window *w)
{
	struct session	*s;
	struct winlink	*wl;
	u_int		 i;

	for (i = 0; i < ARRAY_LENGTH(&sessions); i++) {
		s = ARRAY_ITEM(&sessions, i);
		if (s == NULL || session_has(s, w) == NULL)
			continue;
		while ((wl = winlink_find_by_window(&s->windows, w)) != NULL) {
			if (session_detach(s, wl)) {
				server_destroy_session_group(s);
				break;
			} else
				server_redraw_session_group(s);
		}
	}
}

int
server_link_window(struct session *src, struct winlink *srcwl,
    struct session *dst, int dstidx, int killflag, int selectflag, char **cause)
{
	struct winlink		*dstwl;
	struct session_group	*srcsg, *dstsg;

	srcsg = session_group_find(src);
	dstsg = session_group_find(dst);
	if (src != dst && srcsg != NULL && dstsg != NULL && srcsg == dstsg) {
		xasprintf(cause, "sessions are grouped");
		return (-1);
	}

	dstwl = NULL;
	if (dstidx != -1)
		dstwl = winlink_find_by_index(&dst->windows, dstidx);
	if (dstwl != NULL) {
		if (dstwl->window == srcwl->window)
			return (0);
		if (killflag) {
			/*
			 * Can't use session_detach as it will destroy session
			 * if this makes it empty.
			 */
			dstwl->flags &= ~WINLINK_ALERTFLAGS;
			winlink_stack_remove(&dst->lastw, dstwl);
			winlink_remove(&dst->windows, dstwl);

			/* Force select/redraw if current. */
			if (dstwl == dst->curw) {
				selectflag = 1;
				dst->curw = NULL;
			}
		}
	}

	if (dstidx == -1)
		dstidx = -1 - options_get_number(&dst->options, "base-index");
	dstwl = session_attach(dst, srcwl->window, dstidx, cause);
	if (dstwl == NULL)
		return (-1);

	if (selectflag)
		session_select(dst, dstwl->idx);
	server_redraw_session_group(dst);

	return (0);
}

void
server_unlink_window(struct session *s, struct winlink *wl)
{
	if (session_detach(s, wl))
		server_destroy_session_group(s);
	else
		server_redraw_session_group(s);
}

void
server_destroy_pane(struct window_pane *wp)
{
	struct window	*w = wp->window;

	if (wp->fd != -1) {
		close(wp->fd);
		bufferevent_free(wp->event);
		wp->fd = -1;
	}

	if (options_get_number(&w->options, "remain-on-exit"))
		return;

	layout_close_pane(wp);
	window_remove_pane(w, wp);

	if (TAILQ_EMPTY(&w->panes))
		server_kill_window(w);
	else
		server_redraw_window(w);
}

void
server_destroy_session_group(struct session *s)
{
	struct session_group	*sg;

	if ((sg = session_group_find(s)) == NULL)
		server_destroy_session(s);
	else {
		TAILQ_FOREACH(s, &sg->sessions, gentry)
			server_destroy_session(s);
		TAILQ_REMOVE(&session_groups, sg, entry);
		xfree(sg);
	}
}

struct session *
server_next_session(struct session *s)
{
	struct session *s_loop, *s_out;
	u_int		i;

	s_out = NULL;
	for (i = 0; i < ARRAY_LENGTH(&sessions); i++) {
		s_loop = ARRAY_ITEM(&sessions, i);
		if (s_loop == s)
			continue;
		if (s_out == NULL ||
		    timercmp(&s_loop->activity_time, &s_out->activity_time, <))
			s_out = s_loop;
	}
	return (s_out);
}

void
server_destroy_session(struct session *s)
{
	struct client	*c;
	struct session	*s_new;
	u_int		 i;

	if (!options_get_number(&s->options, "detach-on-destroy"))
		s_new = server_next_session(s);
	else
		s_new = NULL;

	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
		c = ARRAY_ITEM(&clients, i);
		if (c == NULL || c->session != s)
			continue;
		if (s_new == NULL) {
			c->session = NULL;
			c->flags |= CLIENT_EXIT;
		} else {
			c->session = s_new;
			server_redraw_client(c);
		}
	}
	recalculate_sizes();
}

void
server_set_identify(struct client *c)
{
	struct timeval	tv;
	int		delay;

	delay = options_get_number(&c->session->options, "display-panes-time");
	tv.tv_sec = delay / 1000;
	tv.tv_usec = (delay % 1000) * 1000L;

	evtimer_del(&c->identify_timer);
	evtimer_set(&c->identify_timer, server_callback_identify, c);
	evtimer_add(&c->identify_timer, &tv);

	c->flags |= CLIENT_IDENTIFY;
	c->tty.flags |= (TTY_FREEZE|TTY_NOCURSOR);
	server_redraw_client(c);
}

void
server_clear_identify(struct client *c)
{
	if (c->flags & CLIENT_IDENTIFY) {
		c->flags &= ~CLIENT_IDENTIFY;
		c->tty.flags &= ~(TTY_FREEZE|TTY_NOCURSOR);
		server_redraw_client(c);
	}
}

/* ARGSUSED */
void
server_callback_identify(unused int fd, unused short events, void *data)
{
	struct client	*c = data;

	server_clear_identify(c);
}

void
server_update_event(struct client *c)
{
	short	events;

	events = 0;
	if (!(c->flags & CLIENT_BAD))
		events |= EV_READ;
	if (c->ibuf.w.queued > 0)
		events |= EV_WRITE;
	event_del(&c->event);
	event_set(&c->event, c->ibuf.fd, events, server_client_callback, c);
	event_add(&c->event, NULL);
}