/*
 * Copyright 2006 Free Software Foundation, Inc.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Reap any leftover children possibly holding file descriptors.
 * 2006-11-30  Jan Kratochvil  <jan.kratochvil@redhat.com>
 */


#define _XOPEN_SOURCE 1
#define _XOPEN_SOURCE_EXTENDED 1
#define _BSD_SOURCE 1

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <dirent.h>
#include <unistd.h>
#include <errno.h>
#include <ctype.h>
#include <string.h>
#include <limits.h>
#include <fcntl.h>


static const char *progname;

static int spawn (char **argv, pid_t *child_pointer)
{
	pid_t child, child_got;
	int status;

	switch (child = fork ()) {
	case -1:
		perror ("fork(2)");
		exit (EXIT_FAILURE);
	case 0:
		/* Do not setpgrp(2) in the parent process as the process-group
		   is shared for the whole sh(1) pipeline we could be a part
		   of.  The process-group is set according to PID of the first
		   command in the pipeline.
		   We would rip even vi(1) in the case of:
		   	./orphanripper sh -c 'sleep 1&' | vi -
		   */
		if (setpgrp ()) {
			perror ("setpgrp");
			exit (EXIT_FAILURE);
		}
		execvp (argv[1], argv + 1);
		perror ("execvp(2)");
		exit (EXIT_FAILURE);
	default:
		break;
	}
	if (child != (child_got = waitpid (child, &status, 0))) {
		fprintf (stderr, "waitpid(%d)=%d: %m\n", (int) child,
			 (int) child_got);
		exit (EXIT_FAILURE);
	}
	if (!WIFEXITED (status)) {
		fprintf (stderr, "waitpid(2): !WIFEXITED(%d)\n", status);
		exit (EXIT_FAILURE);
	}

	if (child_pointer)
		*child_pointer = child;
	return WEXITSTATUS (status);
}

/* Detected commandline may look weird due to a race:
   Original command:
   	./orphanripper sh -c 'sleep 1&' &
   Correct output:
   	[1] 29610
   	./orphanripper: Killed -9 orphan PID 29612 (PGID 29611): sleep 1
   Raced output (sh(1) child still did not update its argv[]):
   	[1] 29613
   	./orphanripper: Killed -9 orphan PID 29615 (PGID 29614): sh -c sleep 1&
   We could delay a bit before ripping the children.  */
static const char *read_cmdline (pid_t pid)
{
	char cmdline_fname[32];
	static char cmdline[LINE_MAX];
	int fd;
	ssize_t got;
	char *s;

	if (snprintf (cmdline_fname, sizeof (cmdline_fname), "/proc/%d/cmdline",
		  (int) pid) < 0)
		return NULL;
	fd = open (cmdline_fname, O_RDONLY);
	if (fd == -1) {
		fprintf (stderr, "%s: open (\"%s\"): %m\n", progname,
			 cmdline_fname);
		return NULL;
	}
	got = read (fd, cmdline, sizeof (cmdline) - 1);
	if (got == -1)
		fprintf (stderr, "%s: read (\"%s\"): %m\n", progname,
			 cmdline_fname);
	if (close (fd))
		fprintf (stderr, "%s: close (\"%s\"): %m\n", progname,
			 cmdline_fname);
	if (got < 0)
		return NULL;
	/* Convert '\0' argument delimiters to spaces.  */
	for (s = cmdline; s < cmdline + got; s++)
		if (!*s)
			*s = ' ';
	/* Trim the trailing spaces (typically single '\0'->' ').  */
	while (s > cmdline && isspace (s[-1]))
		s--;
	*s = 0;
	return cmdline;
}

static void rip_pid (pid_t pid, pid_t pgid_child)
{
	pid_t pgid_pids;
	const char *cmdline;

	/* Don't shoot ourselves.  */
	if (pid == getpid())
		return;
	pgid_pids = getpgid (pid);
	/* Ignore errors (permissions? untested).  */
	if (pgid_pids == -1)
		return;
	/* Not a process of ours.  */
	if (pgid_pids != pgid_child)
		return;

	cmdline = read_cmdline (pid);
	if (!cmdline)
		cmdline = "<error>";
	fprintf (stderr, "%s: Killed -9 orphan PID %d (PGID %d): %s\n",
	         progname, (int) pid, (int) pgid_pids, cmdline);
	if (kill (pid, SIGKILL)) {
		fprintf (stderr, "%s: kill (%d, SIGKILL): %m\n", progname,
			 (int) pid);
		return;
	}
	/* Do not waitpid(2) as it cannot be our direct descendant and it gets
	   cleaned up by init(8).  */
#if 0
	pid_t pid_got;
	if (pid != (pid_got = waitpid (pid, NULL, 0))) {
		fprintf (stderr, "%s: waitpid (%d) != %d: %m\n", progname,
			 (int) pid, (int) pid_got);
		return;
	}
#endif
}

static void rip (pid_t pgid_child)
{
	DIR *dir;
	struct dirent *dirent;

	dir = opendir ("/proc");
	if (!dir) {
		perror ("opendir (\"/proc\")");
		exit (EXIT_FAILURE);
	}
	while ((errno = 0, dirent = readdir (dir))) {
		const char *cs;

		/* FIXME: POSIX portability.  */
		if (dirent->d_type != DT_DIR)
			continue;
		/* Check /^\d+$/:  */
		for (cs = dirent->d_name; *cs; cs++)
			if (!isdigit (*cs))
				break;
		if (cs == dirent->d_name || *cs)
			continue;
		rip_pid (atoi (dirent->d_name), pgid_child);
	}
	if (errno) {
		perror ("readdir (\"/proc\")");
		exit (EXIT_FAILURE);
	}
	if (closedir (dir)) {
		perror ("closedir (\"/proc\")");
		exit (EXIT_FAILURE);
	}

}

int main (int argc, char **argv)
{
	int rc;
	pid_t child;

	if (argc < 2
	    || !strcmp (argv[1], "-h")
	    || !strcmp (argv[1], "--help")) {
		fputs("Syntax: orphanripper <execvp(3) commandline>\n", stdout);
		exit (EXIT_FAILURE);
	}
	progname = argv[0];
	rc = spawn (argv, &child);
	rip (child);
	return rc;
}