/***********************************************************/
/*
 *
 *  The telnet DAEMON
 *
 *  Author: 17,may 2001
 *
 *   WORK: fernando.ruiz@ctv.es 
 *   HOME: correo@fernando-ruiz.com
 *
 * After start the net you can start this daemon.
 * It uses the previously inited pseudo-terminales (pty.c)
 * getting a new terminal with getpty(). This function
 * gives a terminal name passing a opened socket like parameter.
 *
 * With register_telnetd() you add a new command in the shell to start
 * this daemon interactively. (Login in /dev/console of course)
 * 
 * Sorry but OOB is not still implemented. (This is the first version)
 *
 * Till Straumann <strauman@slac.stanford.edu>
 *  - made the 'shell' interface more generic, i.e. it is now
 *    possible to have 'telnetd' run an arbitrary 'shell'
 *    program.
 */

/*
                      LICENSE INFORMATION

RTEMS is free software; you can redistribute it and/or modify it under
terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.  RTEMS 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 RTEMS; see
file COPYING. If not, write to the Free Software Foundation, 675
Mass Ave, Cambridge, MA 02139, USA.

As a special exception, including RTEMS header files in a file,
instantiating RTEMS generics or templates, or linking other files
with RTEMS objects to produce an executable application, does not
by itself cause the resulting executable application to be covered
by the GNU General Public License. This exception does not
however invalidate any other reasons why the executable file might be
covered by the GNU Public License.
*/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems.h>
#include <rtems/error.h>
#include <rtems/pty.h>
#include <rtems/shell.h>
#include <rtems/telnetd.h>
#include <rtems/bspIo.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <syslog.h>

#include <rtems/userenv.h>
#include <rtems/error.h>
#include <rtems/rtems_bsdnet.h>

#define PARANOIA

extern char *telnet_get_pty(int socket);
extern int   telnet_pty_initialize();
extern int   telnet_pty_finalize();

struct shell_args {
	char	*devname;
	void	*arg;
	char	peername[16];
	char	delete_myself;
};

typedef union uni_sa {
	struct sockaddr_in	sin;
	struct sockaddr     sa;
} uni_sa;

static int sockpeername(int sock, char *buf, int bufsz);

static int initialize_telnetd();

void * telnetd_dflt_spawn(const char *name, unsigned priority, unsigned stackSize, void (*fn)(void*), void *fnarg);

/***********************************************************/
rtems_id            telnetd_task_id      =0;
uint32_t		    telnetd_stack_size   =32000;
rtems_task_priority telnetd_task_priority=0;
int					telnetd_dont_spawn   =0;
void				(*telnetd_shell)(char *, void*)=0;
void				*telnetd_shell_arg	 =0;
void *				(*telnetd_spawn_task)(const char *, unsigned, unsigned, void (*)(void*), void *) = telnetd_dflt_spawn;

static char *grab_a_Connection(int des_socket, uni_sa *srv, char *peername, int sz)
{
char		*rval = 0;
#if 0
socklen_t	
#else
/* 4.6 doesn't have socklen_t */
uint32_t
#endif
			size_adr = sizeof(srv->sin);
int			acp_sock;

	acp_sock = accept(des_socket,&srv->sa,&size_adr);

	if (acp_sock<0) {
		perror("telnetd:accept");
		goto bailout;
	};

	if ( !(rval=telnet_get_pty(acp_sock)) ) {
		syslog( LOG_DAEMON | LOG_ERR, "telnetd: unable to obtain PTY");
		/* NOTE: failing 'do_get_pty()' closed the socket */
		goto bailout;
	}

	if (sockpeername(acp_sock, peername, sz))
		strncpy(peername, "<UNKNOWN>", sz);

#ifdef PARANOIA
	syslog(LOG_DAEMON | LOG_INFO,
			"telnetd: accepted connection from %s on %s",
			peername,
			rval);
#endif

bailout:

	return rval;
}


static void release_a_Connection(char *devname, char *peername, FILE **pstd, int n)
{

#ifdef PARANOIA
	syslog( LOG_DAEMON | LOG_INFO,
			"telnetd: releasing connection from %s on %s",
			peername,
			devname );
#endif

	while (--n>=0)
		if (pstd[n]) fclose(pstd[n]);

}

static int sockpeername(int sock, char *buf, int bufsz)
{
uni_sa	peer;
#if 0
socklen_t	
#else
/* 4.6 doesn't have socklen_t */
uint32_t
#endif
		len  = sizeof(peer.sin);

int		rval = sock < 0;

	if ( !rval)
		rval = getpeername(sock, &peer.sa, &len);

	if ( !rval )
		rval = !inet_ntop( AF_INET, &peer.sin.sin_addr, buf, bufsz );

	return rval;
}

#if 1
#define INSIDE_TELNETD
#include "check_passwd.c"
#else
#define check_passwd(arg) 0
#endif


static void
spawned_shell(void *arg);

/***********************************************************/
static void
rtems_task_telnetd(void *task_argument)
{
int					des_socket;
uni_sa				srv;
char				*devname;
char				peername[16];
int					i=1;
int					size_adr;
struct shell_args	*arg;

	if ((des_socket=socket(PF_INET,SOCK_STREAM,0))<0) {
		perror("telnetd:socket");
		telnetd_task_id=0;
		rtems_task_delete(RTEMS_SELF);
	};
	setsockopt(des_socket,SOL_SOCKET,SO_KEEPALIVE,&i,sizeof(i));

	memset(&srv,0,sizeof(srv));
	srv.sin.sin_family=AF_INET;
	srv.sin.sin_port=htons(23);
	size_adr=sizeof(srv.sin);
	if ((bind(des_socket,&srv.sa,size_adr))<0) {
		perror("telnetd:bind");
	        close(des_socket);
		telnetd_task_id=0;
		rtems_task_delete(RTEMS_SELF);
	};
	if ((listen(des_socket,5))<0) {
		perror("telnetd:listen");
	        close(des_socket);
		telnetd_task_id=0;
		rtems_task_delete(RTEMS_SELF);
	};

	/* we don't redirect stdio as this probably
	 * was started from the console anyways..
	 */
	do {
	  devname = grab_a_Connection(des_socket, &srv, peername, sizeof(peername));

	  if ( !devname ) {
		/* if something went wrong, sleep for some time */
		sleep(10);
		continue;
	  }
	  if ( telnetd_dont_spawn ) {
		if ( 0 == check_passwd(peername) )
			telnetd_shell(devname, telnetd_shell_arg);
	  } else {
		arg = malloc( sizeof(*arg) );

		arg->devname = devname;
		arg->arg = telnetd_shell_arg;
		strncpy(arg->peername, peername, sizeof(arg->peername));

		if ( !telnetd_spawn_task(&devname[5], telnetd_task_priority, telnetd_stack_size, spawned_shell, arg) ) {

			FILE *dummy;

			if ( telnetd_spawn_task != telnetd_dflt_spawn ) {
				fprintf(stderr,"Telnetd: Unable to spawn child task\n");
			}

			/* hmm - the pty driver slot can only be
			 * released by opening and subsequently
			 * closing the PTY - this also closes
			 * the underlying socket. So we mock up
			 * a stream...
			 */

			if ( !(dummy=fopen(devname,"r+")) )
				perror("Unable to dummy open the pty, losing a slot :-(");
			release_a_Connection(devname, peername, &dummy, 1);
			free(arg);
			sleep(2); /* don't accept connections too fast */
  		}
	  }
	} while(1);
	/* TODO: how to free the connection semaphore? But then - 
	 *       stopping the daemon is probably only needed during
	 *       development/debugging.
	 *       Finalizer code should collect all the connection semaphore
	 *       counts and eventually clean up...
	 */
	close(des_socket);
	telnetd_task_id=0;
}
/***********************************************************/
static int initialize_telnetd(void) {
	
	if (telnetd_task_id         ) return RTEMS_RESOURCE_IN_USE;
	if (telnetd_stack_size<=0   ) telnetd_stack_size   =32000;

	if ( !telnetd_spawn_task("TNTD", telnetd_task_priority, RTEMS_MINIMUM_STACK_SIZE, rtems_task_telnetd, 0) ) {
		return -1;	
	}
	return 0;
}

/***********************************************************/
int startTelnetd(void (*cmd)(char *, void *), void *arg, int dontSpawn, int stack, int priority)
{
	rtems_status_code	sc;

	printf("This is rtems-telnetd (modified by Till Straumann)\n");
	printf("$Id$\n");
	printf("Release $Name$\n");

	if ( !telnetd_shell && !cmd ) {
		fprintf(stderr,"startTelnetd(): setup error - NO SHELL; bailing out\n");
		return 1;
	}

	if (telnetd_task_id) {
		fprintf(stderr,"ERROR:telnetd already started\n");
		return 1;
	};

	if ( !telnet_pty_initialize() ) {
		fprintf(stderr,"PTY driver probably not properly registered\n");
		return 1;
	}

	if (cmd)
		telnetd_shell = cmd;
	telnetd_shell_arg     = arg;
	telnetd_stack_size    = stack;
	if ( !priority ) {
		priority = rtems_bsdnet_config.network_task_priority;
	}
	if ( priority < 2 )
		priority=100;
	telnetd_task_priority = priority;
	telnetd_dont_spawn    = dontSpawn;

	sc=initialize_telnetd();
        if (sc!=RTEMS_SUCCESSFUL) return sc;
	printf("rtems_telnetd() started with stacksize=%u,priority=%d\n",
                        (unsigned)telnetd_stack_size,(int)telnetd_task_priority);
	return 0;
}

/* utility wrapper */
static void
spawned_shell(void *targ)
{
rtems_status_code	sc;
FILE				*nstd[3]={0};
FILE				*ostd[3]={ stdin, stdout, stderr };
int					i=0;
struct shell_args	*arg = targ;

	sc=rtems_libio_set_private_env();

	/* newlib hack/workaround. Before we change stdin/out/err we must make
         * sure the internal data are initialized (fileno(stdout) has this sideeffect).
	 * This should probably be done from RTEMS' libc support layer...
	 * (T.S., newlibc-1.13; 2005/10)
         */

	fileno(stdout);

	if (RTEMS_SUCCESSFUL != sc) {
		rtems_error(sc,"rtems_libio_set_private_env");
		goto cleanup;
	}

	/* redirect stdio */
	for (i=0; i<3; i++) {
		if ( !(nstd[i]=fopen(arg->devname,"r+")) ) {
			perror("unable to open stdio");
			goto cleanup;
		}
	}

	stdin  = nstd[0];
	stdout = nstd[1];
	stderr = nstd[2];



#if 0
printk("STDOUT is now %x (%x) (FD %i/%i)\n",stdout,nstd[1],fileno(stdout),fileno(nstd[1]));
printf("hello\n");
write(fileno(stdout),"hellofd\n",8);
#endif

	/* call their routine */
	if ( 0 == check_passwd(arg->peername) )
		telnetd_shell(arg->devname, arg->arg);

	stdin  = ostd[0];
	stdout = ostd[1];
	stderr = ostd[2];

cleanup:
	release_a_Connection(arg->devname, arg->peername, nstd, i);
	free(arg);
}

struct wrap_delete_args {
	void (*t)(void *);
	void           *a;
};

static rtems_task
wrap_delete(rtems_task_argument arg)
{
struct wrap_delete_args     *pwa = (struct wrap_delete_args *)arg;
register void              (*t)(void *) = pwa->t;
register void               *a   = pwa->a;

	/* free argument before calling function (which may never return if
	 * they choose to delete themselves)
	 */
	free(pwa);
	t(a);
	rtems_task_delete(RTEMS_SELF);
}

void *
telnetd_dflt_spawn(const char *name, unsigned int priority, unsigned int stackSize, void (*fn)(void *), void* fnarg)
{
rtems_status_code sc;
rtems_id          task_id;
char              nm[4] = {'X','X','X','X' };
struct wrap_delete_args *pwa = malloc(sizeof(*pwa));

		strncpy(nm, name, 4);

		if ( !pwa ) {
			perror("Telnetd: no memory\n");
			return 0;
		}

		pwa->t = fn;
		pwa->a = fnarg;

		if ((sc=rtems_task_create(
				rtems_build_name(nm[0], nm[1], nm[2], nm[3]),
				(rtems_task_priority)priority,
				stackSize,
				RTEMS_DEFAULT_MODES,
				RTEMS_DEFAULT_ATTRIBUTES | RTEMS_FLOATING_POINT,
				&task_id)) ||
			(sc=rtems_task_start(
				task_id,
				wrap_delete,
				(rtems_task_argument)pwa))) {
					free(pwa);
					rtems_error(sc,"Telnetd: spawning task failed");
					return 0;
		}
	return (void*)task_id;
}

/* convenience routines for CEXP (retrieve stdio descriptors
 * from reent structure)
 *
 */
#ifdef stdin
static __inline__ FILE *
_stdin(void)  { return stdin; }
#undef stdin
FILE *stdin(void)  { return _stdin(); }
#endif
#ifdef stdout
static __inline__ FILE *
_stdout(void) { return stdout; }
#undef stdout
FILE *stdout(void) { return _stdout(); }
#endif
#ifdef stderr
static __inline__ FILE *
_stderr(void) { return stderr; }
#undef stderr
FILE *stderr(void) { return _stderr(); }
#endif

/* MUST NOT USE stdin & friends below here !!!!!!!!!!!!! */