[9fans] file descriptor leak

[arisawa <arisawa@ar.aichi-u.ac.jp>]

Hello,

I have observed warning messages from dns server:
dns 30792: warning process exceeded 100 file descriptors
dns 30888: warning process exceeded 200 file descriptors
…

probably the file descriptor leak comes from dnresolve.c

udpquery(Query *qp, char *mntpt, int depth, int patient, int inns)
{
	…
			msg = system(open("/dev/null", ORDWR), "outside");
	…
}

char *
system(int fd, char *cmd)
{
	int pid, p, i;
	static Waitmsg msg;

	if((pid = fork()) == -1)
		sysfatal("fork failed: %r");
	else if(pid == 0){
		dup(fd, 0);
		close(fd);
		for (i = 3; i < 200; i++)
			close(i);		/* don't leak fds */
		execl("/bin/rc", "rc", "-c", cmd, nil);
		sysfatal("exec rc: %r");
	}
	for(p = waitpid(); p >= 0; p = waitpid())
		if(p == pid)
			return msg.msg;
	return "lost child";
}

fd is lost if pid > 0

my server is running on 9front. however both 9atom and bell-labs use same routine.

Kenji Arisawa