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Use an explicit job state instead of avoid closing our side of the
socketpair and setting it to -1 to mark when the other side is
closed. This avoids closing it while the libevent bufferevent still has
it (it could try to add it to the polled set which some mechanisms don't
like). Fixes part a problem reported by Bruno Sutic.

/* $OpenBSD: job.c,v 1.36 2015/06/17 16:44:49 nicm Exp $ */

/*
 * Copyright (c) 2009 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 <sys/socket.h>

#include <fcntl.h>
#include <paths.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "tmux.h"

/*
 * Job scheduling. Run queued commands in the background and record their
 * output.
 */

void	job_callback(struct bufferevent *, short, void *);
void	job_write_callback(struct bufferevent *, void *);

/* All jobs list. */
struct joblist	all_jobs = LIST_HEAD_INITIALIZER(all_jobs);

/* Start a job running, if it isn't already. */
struct job *
job_run(const char *cmd, struct session *s, int cwd,
    void (*callbackfn)(struct job *), void (*freefn)(void *), void *data)
{
	struct job	*job;
	struct environ	 env;
	pid_t		 pid;
	int		 nullfd, out[2];

	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, out) != 0)
		return (NULL);

	environ_init(&env);
	environ_copy(&global_environ, &env);
	if (s != NULL)
		environ_copy(&s->environ, &env);
	server_fill_environ(s, &env);

	switch (pid = fork()) {
	case -1:
		environ_free(&env);
		close(out[0]);
		close(out[1]);
		return (NULL);
	case 0:		/* child */
		clear_signals(1);

		if (cwd != -1 && fchdir(cwd) != 0)
			chdir("/");

		environ_push(&env);
		environ_free(&env);

		if (dup2(out[1], STDIN_FILENO) == -1)
			fatal("dup2 failed");
		if (dup2(out[1], STDOUT_FILENO) == -1)
			fatal("dup2 failed");
		if (out[1] != STDIN_FILENO && out[1] != STDOUT_FILENO)
			close(out[1]);
		close(out[0]);

		nullfd = open(_PATH_DEVNULL, O_RDWR, 0);
		if (nullfd < 0)
			fatal("open failed");
		if (dup2(nullfd, STDERR_FILENO) == -1)
			fatal("dup2 failed");
		if (nullfd != STDERR_FILENO)
			close(nullfd);

		closefrom(STDERR_FILENO + 1);

		execl(_PATH_BSHELL, "sh", "-c", cmd, (char *) NULL);
		fatal("execl failed");
	}

	/* parent */
	environ_free(&env);
	close(out[1]);

	job = xmalloc(sizeof *job);
	job->state = JOB_RUNNING;

	job->cmd = xstrdup(cmd);
	job->pid = pid;
	job->status = 0;

	LIST_INSERT_HEAD(&all_jobs, job, lentry);

	job->callbackfn = callbackfn;
	job->freefn = freefn;
	job->data = data;

	job->fd = out[0];
	setblocking(job->fd, 0);

	job->event = bufferevent_new(job->fd, NULL, job_write_callback,
	    job_callback, job);
	bufferevent_enable(job->event, EV_READ|EV_WRITE);

	log_debug("run job %p: %s, pid %ld", job, job->cmd, (long) job->pid);
	return (job);
}

/* Kill and free an individual job. */
void
job_free(struct job *job)
{
	log_debug("free job %p: %s", job, job->cmd);

	LIST_REMOVE(job, lentry);
	free(job->cmd);

	if (job->freefn != NULL && job->data != NULL)
		job->freefn(job->data);

	if (job->pid != -1)
		kill(job->pid, SIGTERM);
	if (job->event != NULL)
		bufferevent_free(job->event);
	if (job->fd != -1)
		close(job->fd);

	free(job);
}

/* Called when output buffer falls below low watermark (default is 0). */
void
job_write_callback(unused struct bufferevent *bufev, void *data)
{
	struct job	*job = data;
	size_t		 len = EVBUFFER_LENGTH(EVBUFFER_OUTPUT(job->event));

	log_debug("job write %p: %s, pid %ld, output left %zu", job, job->cmd,
	    (long) job->pid, len);

	if (len == 0) {
		shutdown(job->fd, SHUT_WR);
		bufferevent_disable(job->event, EV_WRITE);
	}
}

/* Job buffer error callback. */
void
job_callback(unused struct bufferevent *bufev, unused short events, void *data)
{
	struct job	*job = data;

	log_debug("job error %p: %s, pid %ld", job, job->cmd, (long) job->pid);

	if (job->state == JOB_DEAD) {
		if (job->callbackfn != NULL)
			job->callbackfn(job);
		job_free(job);
	} else {
		bufferevent_disable(job->event, EV_READ);
		job->state = JOB_CLOSED;
	}
}

/* Job died (waitpid() returned its pid). */
void
job_died(struct job *job, int status)
{
	log_debug("job died %p: %s, pid %ld", job, job->cmd, (long) job->pid);

	job->status = status;

	if (job->state == JOB_CLOSED) {
		if (job->callbackfn != NULL)
			job->callbackfn(job);
		job_free(job);
	} else {
		job->pid = -1;
		job->state = JOB_DEAD;
	}
}