#include <u.h>#include <libc.h>#include <auth.h> /* *  become the authenticated user */intauth_chuid(AuthInfo *ai, char *ns){	int rv, fd; 	if(ai == nil || ai->cap == nil || ai->cap[0] == 0){		werrstr("no capability");		return -1;	} 	/* change uid */	fd = open("/dev/capuse", OCEXEC|OWRITE);	if(fd < 0){		werrstr("opening /dev/capuse: %r");		return -1;	}	rv = write(fd, ai->cap, strlen(ai->cap));	close(fd);	if(rv < 0){		werrstr("writing %s to /dev/capuse: %r", ai->cap);		return -1;	} 	/* get a link to factotum as new user */	fd = open("/srv/factotum", ORDWR);	if(fd >= 0){		if(mount(fd, -1, "/mnt", MREPL, "") == -1)			close(fd);	} 	/* set up new namespace */	return newns(ai->cuid, ns);}