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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: child.c,v 1.14 2009/10/27 23:59:42 deraadt Exp $	*/

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "defs.h"

/*
 * Functions for rdist related to children
 */

#include <sys/types.h>
#include <sys/wait.h>
#if	defined(NEED_SYS_SELECT_H)
#include <sys/select.h>
#endif	/* NEED_SYS_SELECT_H */

typedef enum _PROCSTATE {
    PSrunning,
    PSdead
} PROCSTATE;

/*
 * Structure for child rdist processes mainted by the parent
 */
struct _child {
	char	       *c_name;			/* Name of child */
	int		c_readfd;		/* Read file descriptor */
	pid_t		c_pid;			/* Process ID */
	PROCSTATE       c_state;		/* Running? */
	struct _child  *c_next;			/* Next entry */
};
typedef struct _child CHILD;

static CHILD	       *childlist = NULL;	/* List of children */
int     		activechildren = 0;	/* Number of active children */
extern int		maxchildren;		/* Max active children */
static int 		needscan = FALSE;	/* Need to scan children */

static void removechild(CHILD *);
static CHILD *copychild(CHILD *);
static void addchild(CHILD *);
static void readchild(CHILD *);
static pid_t waitproc(int *, int);
static void reap(int);
static void childscan(void);

/*
 * Remove a child that has died (exited) 
 * from the list of active children
 */
static void
removechild(CHILD *child)
{
	CHILD *pc, *prevpc;

	debugmsg(DM_CALL, "removechild(%s, %d, %d) start",
		 child->c_name, child->c_pid, child->c_readfd);

	/*
	 * Find the child in the list
	 */
	for (pc = childlist, prevpc = NULL; pc != NULL; 
	     prevpc = pc, pc = pc->c_next)
		if (pc == child) 
			break;

	if (pc == NULL)
		error("RemoveChild called with bad child %s %d %d",
		      child->c_name, child->c_pid, child->c_readfd);
	else {
		/*
		 * Remove the child
		 */
#if	defined(POSIX_SIGNALS)
		sigset_t set;

		sigemptyset(&set);
		sigaddset(&set, SIGCHLD);
		sigprocmask(SIG_BLOCK, &set, NULL);
#else	/* !POSIX_SIGNALS */
		int oldmask;

		oldmask = sigblock(sigmask(SIGCHLD));
#endif	/* POSIX_SIGNALS */

		if (prevpc != NULL)
			prevpc->c_next = pc->c_next;
		else
			childlist = pc->c_next;

#if	defined(POSIX_SIGNALS)
		sigprocmask(SIG_UNBLOCK, &set, NULL);
#else
		sigsetmask(oldmask);
#endif	/* POSIX_SIGNALS */

		(void) free(child->c_name);
		--activechildren;
		(void) close(child->c_readfd);
		(void) free(pc);
	}

	debugmsg(DM_CALL, "removechild() end");
}

/*
 * Create a totally new copy of a child.
 */
static CHILD *
copychild(CHILD *child)
{
	CHILD *newc;

	newc = (CHILD *) xmalloc(sizeof(CHILD));

	newc->c_name = xstrdup(child->c_name);
	newc->c_readfd = child->c_readfd;
	newc->c_pid = child->c_pid;
	newc->c_state = child->c_state;
	newc->c_next = NULL;

	return(newc);
}

/*
 * Add a child to the list of children.
 */			
static void
addchild(CHILD *child)
{
	CHILD *pc;

	debugmsg(DM_CALL, "addchild() start\n");

	pc = copychild(child);
	pc->c_next = childlist;
	childlist = pc;

	++activechildren;

	debugmsg(DM_MISC,
		 "addchild() created '%s' pid %d fd %d (active=%d)\n",
		 child->c_name, child->c_pid, child->c_readfd, activechildren);
}

/*
 * Read input from a child process.
 */
static void
readchild(CHILD *child)
{
	char rbuf[BUFSIZ];
	int amt;

	debugmsg(DM_CALL, "[readchild(%s, %d, %d) start]", 
		 child->c_name, child->c_pid, child->c_readfd);

	/*
	 * Check that this is a valid child.
	 */
	if (child->c_name == NULL || child->c_readfd <= 0) {
		debugmsg(DM_MISC, "[readchild(%s, %d, %d) bad child]",
			 child->c_name, child->c_pid, child->c_readfd);
		return;
	}

	/*
	 * Read from child and display the result.
	 */
	while ((amt = read(child->c_readfd, rbuf, sizeof(rbuf))) > 0) {
		/* XXX remove these debug calls */
		debugmsg(DM_MISC, "[readchild(%s, %d, %d) got %d bytes]", 
			 child->c_name, child->c_pid, child->c_readfd, amt);

		(void) xwrite(fileno(stdout), rbuf, amt);

		debugmsg(DM_MISC, "[readchild(%s, %d, %d) write done]",
			 child->c_name, child->c_pid, child->c_readfd);
	}

	debugmsg(DM_MISC, "readchild(%s, %d, %d) done: amt = %d errno = %d\n",
		 child->c_name, child->c_pid, child->c_readfd, amt, errno);

	/* 
	 * See if we've reached EOF 
	 */
	if (amt == 0)
		debugmsg(DM_MISC, "readchild(%s, %d, %d) at EOF\n",
			 child->c_name, child->c_pid, child->c_readfd);
}

/*
 * Wait for processes to exit.  If "block" is true, then we block
 * until a process exits.  Otherwise, we return right away.  If
 * a process does exit, then the pointer "statval" is set to the
 * exit status of the exiting process, if statval is not NULL.
 */
static pid_t
waitproc(int *statval, int block)
{
	WAIT_ARG_TYPE status;
	pid_t pid;
	int exitval;

	debugmsg(DM_CALL, "waitproc() %s, active children = %d...\n", 
		 (block) ? "blocking" : "nonblocking", activechildren);

#if	WAIT_TYPE == WAIT_WAITPID
	pid = waitpid(-1, &status, (block) ? 0 : WNOHANG);
#else
#if	WAIT_TYPE == WAIT_WAIT3
	pid = wait3(&status, (block) ? 0 : WNOHANG, NULL);
#endif	/* WAIT_WAIT3 */
#endif	/* WAIT_WAITPID */

#if	defined(WEXITSTATUS)
	exitval = WEXITSTATUS(status);
#else
	exitval = status.w_retcode;
#endif	/* defined(WEXITSTATUS) */

	if (pid > 0 && exitval != 0) {
		nerrs++;
		debugmsg(DM_MISC, 
			 "Child process %d exited with status %d.\n",
			 pid, exitval);
	}

	if (statval)
		*statval = exitval;

	debugmsg(DM_CALL, "waitproc() done (activechildren = %d)\n", 
		 activechildren);

	return(pid);
}

/*
 * Check to see if any children have exited, and if so, read any unread
 * input and then remove the child from the list of children.
 */
static void
reap(int dummy)
{
	CHILD *pc;
	int save_errno = errno;
	int status = 0;
	pid_t pid;

	debugmsg(DM_CALL, "reap() called\n");

	/*
	 * Reap every child that has exited.  Break out of the
	 * loop as soon as we run out of children that have
	 * exited so far.
	 */
	for ( ; ; ) {
		/*
		 * Do a non-blocking check for exiting processes
		 */
		pid = waitproc(&status, FALSE);
		debugmsg(DM_MISC, 
			 "reap() pid = %d status = %d activechildren=%d\n",
			 pid, status, activechildren);

		/*
		 * See if a child really exited
		 */
		if (pid == 0)
			break;
		if (pid < 0) {
			if (errno != ECHILD)
				error("Wait failed: %s", SYSERR);
			break;
		}

		/*
		 * Find the process (pid) and mark it as dead.
		 */
		for (pc = childlist; pc; pc = pc->c_next)
			if (pc->c_pid == pid) {
				needscan = TRUE;
				pc->c_state = PSdead;
			}

	}

	/*
	 * Reset signals
	 */
	(void) signal(SIGCHLD, reap);

	debugmsg(DM_CALL, "reap() done\n");
	errno = save_errno;
}

/*
 * Scan the children list to find the child that just exited, 
 * read any unread input, then remove it from the list of active children.
 */
static void
childscan(void)
{
	CHILD *pc, *nextpc;
	
	debugmsg(DM_CALL, "childscan() start");

	for (pc = childlist; pc; pc = nextpc) {
		nextpc = pc->c_next;
		if (pc->c_state == PSdead) {
			readchild(pc);
			removechild(pc);
		}
	}

	needscan = FALSE;
	debugmsg(DM_CALL, "childscan() end");
}

/*
#if	defined HAVE_SELECT
 *
 * Wait for children to send output for us to read.
 *
#else	!HAVE_SELECT
 *
 * Wait up for children to exit.
 *
#endif
 */
void
waitup(void)
{
#if	defined(HAVE_SELECT)
	int count;
	CHILD *pc;
	fd_set *rchildfdsp = NULL;
	int rchildfdsn = 0;
	size_t bytes;

	debugmsg(DM_CALL, "waitup() start\n");

	if (needscan)
		childscan();

	if (activechildren <= 0)
		return;

	/*
	 * Settup which children we want to select() on.
	 */
	for (pc = childlist; pc; pc = pc->c_next)
		if (pc->c_readfd > rchildfdsn)
			rchildfdsn = pc->c_readfd;
	bytes = howmany(rchildfdsn+1, NFDBITS) * sizeof(fd_mask);
	if ((rchildfdsp = (fd_set *)malloc(bytes)) == NULL)
		return;

	memset(rchildfdsp, 0, bytes);
	for (pc = childlist; pc; pc = pc->c_next)
		if (pc->c_readfd > 0) {
			debugmsg(DM_MISC, "waitup() select on %d (%s)\n",
				 pc->c_readfd, pc->c_name);
			FD_SET(pc->c_readfd, rchildfdsp);
		}

	/*
	 * Actually call select()
	 */
	/* XXX remove debugmsg() calls */
	debugmsg(DM_MISC, "waitup() Call select(), activechildren=%d\n", 
		 activechildren);

	count = select(rchildfdsn+1, (SELECT_FD_TYPE *) rchildfdsp, 
		       NULL, NULL, NULL);

	debugmsg(DM_MISC, "waitup() select returned %d activechildren = %d\n", 
		 count, activechildren);

	/*
	 * select() will return count < 0 and errno == EINTR when
	 * there are no active children left.
	 */
	if (count < 0) {
		if (errno != EINTR)
			error("Select failed reading children input: %s", 
			      SYSERR);
		free(rchildfdsp);
		return;
	}

	/*
	 * This should never happen.
	 */
	if (count == 0) {
		error("Select returned an unexpected count of 0.");
		free(rchildfdsp);
		return;
	}

	/*
	 * Go through the list of children and read from each child
	 * which select() detected as ready for reading.
	 */
	for (pc = childlist; pc && count > 0; pc = pc->c_next) {
		/* 
		 * Make sure child still exists 
		 */
		if (pc->c_name && kill(pc->c_pid, 0) < 0 && 
		    errno == ESRCH) {
			debugmsg(DM_MISC, 
				 "waitup() proc %d (%s) died unexpectedly!",
				 pc->c_pid, pc->c_name);
			pc->c_state = PSdead;
			needscan = TRUE;
		}

		if (pc->c_name == NULL ||
		    !FD_ISSET(pc->c_readfd, rchildfdsp))
			continue;

		readchild(pc);
		--count;
	}
	free(rchildfdsp);

#else	/* !defined(HAVE_SELECT) */

	/*
	 * The non-select() version of waitproc()
	 */
	debugmsg(DM_CALL, "waitup() start\n");

	if (waitproc(NULL, TRUE) > 0)
		--activechildren;

#endif	/* defined(HAVE_SELECT) */
	debugmsg(DM_CALL, "waitup() end\n");
}

/*
 * Spawn (create) a new child process for "cmd".
 */
int
spawn(struct cmd *cmd, struct cmd *cmdlist)
{
	pid_t pid;
	int fildes[2];
	char *childname = cmd->c_name;

	if (pipe(fildes) < 0) {
		error("Cannot create pipe for %s: %s", childname, SYSERR);
		return(-1);
	}

	pid = fork();
	if (pid == (pid_t)-1) {
		error("Cannot spawn child for %s: fork failed: %s", 
		      childname, SYSERR);
		return(-1);
	} else if (pid > 0) {
		/*
		 * Parent
		 */
		static CHILD newchild;

#if	defined(FORK_MISSES)
		/*
		 * XXX Some OS's have a bug where fork does not
		 * always return properly to the parent
		 * when a number of forks are done very quicky.
		 */
		sleep(2);
#endif	/* FORK_MISSES */

		/* Receive notification when the child exits */
		(void) signal(SIGCHLD, reap);

		/* Settup the new child */
		newchild.c_next = NULL;
		newchild.c_name = childname;
		newchild.c_readfd = fildes[PIPE_READ];
		newchild.c_pid = pid;
		newchild.c_state = PSrunning;

		/* We're not going to write to the child */
		(void) close(fildes[PIPE_WRITE]);

		/* Set non-blocking I/O */
		if (setnonblocking(newchild.c_readfd, TRUE) < 0) {
			error("Set nonblocking I/O failed: %s", SYSERR);
			return(-1);
		}

		/* Add new child to child list */
		addchild(&newchild);

		/* Mark all other entries for this host as assigned */
		markassigned(cmd, cmdlist);

		debugmsg(DM_CALL,
			 "spawn() Forked child %d for host %s active = %d\n",
			 pid, childname, activechildren);
		return(pid);
	} else {
		/* 
		 * Child 
		 */

		/* We're not going to read from our parent */
		(void) close(fildes[PIPE_READ]);

		/* Make stdout and stderr go to PIPE_WRITE (our parent) */
		if (dup2(fildes[PIPE_WRITE], (int)fileno(stdout)) < 0) {
			error("Cannot duplicate stdout file descriptor: %s", 
			      SYSERR);
			return(-1);
		}
		if (dup2(fildes[PIPE_WRITE], (int)fileno(stderr)) < 0) {
			error("Cannot duplicate stderr file descriptor: %s", 
			      SYSERR);
			return(-1);
		}

		return(0);
	}
}


/*
 * Enable or disable non-blocking I/O mode.
 *
 * Code is from INN by Rich Salz.
 */
#if	NBIO_TYPE == NBIO_IOCTL
#include <sys/ioctl.h>

int
setnonblocking(int fd, int flag)
{
	int state;

	state = flag ? 1 : 0;
	return(ioctl(fd, FIONBIO, (char *)&state));
}

#endif	/* NBIO_IOCTL */


#if	NBIO_TYPE == NBIO_FCNTL
int
setnonblocking(int fd, int flag)
{
	int	mode;

	if ((mode = fcntl(fd, F_GETFL, 0)) < 0)
		return(-1);
	if (flag)
		mode |= FNDELAY;
	else
		mode &= ~FNDELAY;
	return(fcntl(fd, F_SETFL, mode));
}
#endif	/* NBIO_FCNTL */