/*
 * Copyright (c) 1995
 *	A.R. Gordon (andrew.gordon@net-tel.co.uk).  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed for the FreeBSD project
 * 4. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY ANDREW GORDON 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 AUTHOR 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 "lockd.h"

#include <sys/param.h>	/* for MAXHOSTNAMELEN	*/
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>


#define	CLIENT_CACHE_SIZE	64	/* No. of client sockets cached	*/
#define	CLIENT_CACHE_LIFETIME	120	/* In seconds			*/


/* log_from_addr ----------------------------------------------------------- */
/*
   Purpose:	Log name of function called and source address
   Returns:	Nothing
   Notes:	Extracts the source address from the transport handle
		passed in as part of the called procedure specification
*/

static void log_from_addr(char *fun_name, struct svc_req *req)
{
  struct sockaddr_in *addr;
  struct hostent *host;
  char hostname_buf[40];

  addr = svc_getcaller(req->rq_xprt);
  host = gethostbyaddr((char *)&(addr->sin_addr), addr->sin_len, AF_INET);
  if (host)
  {
    strncpy(hostname_buf, host->h_name, sizeof(hostname_buf) -1);
    hostname_buf[sizeof(hostname_buf) -1] = '\0';
  }
  else	/* No hostname available - print raw address	*/
  {
    strcpy(hostname_buf, inet_ntoa(addr->sin_addr));
  }

  syslog(LOG_DEBUG, "%s from %s", fun_name, hostname_buf);
}


/* get_client -------------------------------------------------------------- */
/*
   Purpose:	Get a CLIENT* for making RPC calls to lockd on given host
   Returns:	CLIENT* pointer, from clnt_udp_create, or NULL if error
   Notes:	Creating a CLIENT* is quite expensive, involving a
		conversation with the remote portmapper to get the
		port number.  Since a given client is quite likely
		to make several locking requests in succession, it is
		desirable to cache the created CLIENT*.

		Since we are using UDP rather than TCP, there is no cost
		to the remote system in keeping these cached indefinitely.
		Unfortunately there is a snag: if the remote system
		reboots, the cached portmapper results will be invalid,
		and we will never detect this since all of the xxx_msg()
		calls return no result - we just fire off a udp packet
		and hope for the best.

		We solve this by discarding cached values after two
		minutes, regardless of whether they have been used
		in the meanwhile (since a bad one might have been used
		plenty of times, as the host keeps retrying the request
		and we keep sending the reply back to the wrong port).

		Given that the entries will always expire in the order
		that they were created, there is no point in a LRU
		algorithm for when the cache gets full - entries are
		always re-used in sequence.
*/

static CLIENT *clnt_cache_ptr[CLIENT_CACHE_SIZE];
static long clnt_cache_time[CLIENT_CACHE_SIZE];	/* time entry created	*/
static struct in_addr clnt_cache_addr[CLIENT_CACHE_SIZE];
static int clnt_cache_next_to_use = 0;

static CLIENT *get_client(struct sockaddr_in *host_addr)
{
  CLIENT *client;
  int sock_no;
  struct timeval retry_time, time_now;
  int i;

  gettimeofday(&time_now, NULL);

  /* Search for the given client in the cache, zapping any expired	*/
  /* entries that we happen to notice in passing.			*/
  for (i = 0; i < CLIENT_CACHE_SIZE; i++)
  {
    client = clnt_cache_ptr[i];
    if (client &&
      ((clnt_cache_time[i] + CLIENT_CACHE_LIFETIME) < time_now.tv_sec))
    {
      /* Cache entry has expired.					*/
      if (debug_level > 3) syslog(LOG_DEBUG, "Expired CLIENT* in cache");
      clnt_cache_time[i] = 0L;
      clnt_destroy(client);
      clnt_cache_ptr[i] = NULL;
      client = NULL;
    }

    if (client && !memcmp(&clnt_cache_addr[i], &host_addr->sin_addr,
      sizeof(struct in_addr)))
    {
      /* Found it!							*/
      if (debug_level > 3) syslog(LOG_DEBUG, "Found CLIENT* in cache");
      return (client);
    }
  }

  /* Not found in cache.  Free the next entry if it is in use		*/
  if (clnt_cache_ptr[clnt_cache_next_to_use])
  {
    clnt_destroy(clnt_cache_ptr[clnt_cache_next_to_use]);
    clnt_cache_ptr[clnt_cache_next_to_use] = NULL;
  }

  /* Create the new client handle					*/

  sock_no = RPC_ANYSOCK;
  retry_time.tv_sec = 5;
  retry_time.tv_usec = 0;
  host_addr->sin_port = 0;	/* Force consultation with portmapper	*/
  client = clntudp_create(host_addr, NLM_PROG, NLM_VERS, retry_time, &sock_no);
  if (!client)
  {
    syslog(LOG_ERR, clnt_spcreateerror("clntudp_create"));
    syslog(LOG_ERR, "Unable to return result to %s",
      inet_ntoa(host_addr->sin_addr));
    return NULL;
  }

  /* Success - update the cache entry					*/
  clnt_cache_ptr[clnt_cache_next_to_use] = client;
  clnt_cache_addr[clnt_cache_next_to_use] = host_addr->sin_addr;
  clnt_cache_time[clnt_cache_next_to_use] = time_now.tv_sec;
  if (++clnt_cache_next_to_use > CLIENT_CACHE_SIZE)
    clnt_cache_next_to_use = 0;

  /* Disable the default timeout, so we can specify our own in calls	*/
  /* to clnt_call(). [note that the timeout is a different concept	*/
  /* from the retry period set in clnt_udp_create() above.]		*/
  retry_time.tv_sec = -1;
  retry_time.tv_usec = -1;
  clnt_control(client, CLSET_TIMEOUT, &retry_time);

  if (debug_level > 3) syslog(LOG_DEBUG, "Created CLIENT* for %s",
      inet_ntoa(host_addr->sin_addr));
  return client;
}


/* transmit_result --------------------------------------------------------- */
/*
   Purpose:	Transmit result for nlm_xxx_msg pseudo-RPCs
   Returns:	Nothing - we have no idea if the datagram got there
   Notes:	clnt_call() will always fail (with timeout) as we are
		calling it with timeout 0 as a hack to just issue a datagram
		without expecting a result
*/

static void transmit_result(int opcode, nlm_res *result, struct svc_req *req)
{
  static char dummy;
  struct sockaddr_in *addr;
  CLIENT *cli;
  int success;
  struct timeval timeo;

  addr = svc_getcaller(req->rq_xprt);
  if (cli = get_client(addr))
  {
    timeo.tv_sec = 0;		/* No timeout - not expecting response	*/
    timeo.tv_usec = 0;

    success = clnt_call(cli, opcode, xdr_nlm_res, result, xdr_void,
      &dummy, timeo);

    if (debug_level > 2) syslog(LOG_DEBUG, "clnt_call returns %d\n", success);
  }
}

/* ------------------------------------------------------------------------- */
/*
   Functions for Unix<->Unix locking (ie. monitored locking, with rpc.statd
   involved to ensure reclaim of locks after a crash of the "stateless"
   server.

   These all come in two flavours - nlm_xxx() and nlm_xxx_msg().
   The first are standard RPCs with argument and result.
   The nlm_xxx_msg() calls implement exactly the same functions, but
   use two pseudo-RPCs (one in each direction).  These calls are NOT
   standard use of the RPC protocol in that they do not return a result
   at all (NB. this is quite different from returning a void result).
   The effect of this is to make the nlm_xxx_msg() calls simple unacknowledged
   datagrams, requiring higher-level code to perform retries.

   Despite the disadvantages of the nlm_xxx_msg() approach (some of which
   are documented in the comments to get_client() above), this is the
   interface used by all current commercial NFS implementations
   [Solaris, SCO, AIX etc.].  This is presumed to be because these allow
   implementations to continue using the standard RPC libraries, while
   avoiding the block-until-result nature of the library interface.

   No client implementations have been identified so far that make use
   of the true RPC version (early SunOS releases would be a likely candidate
   for testing).
*/


/* nlm_test ---------------------------------------------------------------- */
/*
   Purpose:	Test whether a specified lock would be granted if requested
   Returns:	nlm_granted (or error code)
   Notes:
*/

nlm_testres *nlm_test_1_svc(nlm_testargs *arg, struct svc_req *rqstp)
{
  static nlm_testres res;
  if (debug_level) log_from_addr("nlm_test", rqstp);

  /* Copy the cookie from the argument into the result.  Note that this	*/
  /* is slightly hazardous, as the structure contains a pointer to a	*/
  /* malloc()ed buffer that will get freed by the caller.  However, the	*/
  /* main function transmits the result before freeing the argument	*/
  /* so it is in fact safe.						*/
  res.cookie = arg->cookie;
  res.stat.stat = nlm_granted;
  return (&res);
}

void *nlm_test_msg_1_svc(nlm_testargs *arg, struct svc_req *rqstp)
{
  nlm_testres res;
  static char dummy;
  struct sockaddr_in *addr;
  CLIENT *cli;
  int success;
  struct timeval timeo;

  if (debug_level) log_from_addr("nlm_test_msg", rqstp);

  res.cookie = arg->cookie;
  res.stat.stat = nlm_granted;

  /* nlm_test has different result type to the other operations, so	*/
  /* can't use transmit_result() in this case				*/
  addr = svc_getcaller(rqstp->rq_xprt);
  if (cli = get_client(addr))
  {
    timeo.tv_sec = 0;		/* No timeout - not expecting response	*/
    timeo.tv_usec = 0;

    success = clnt_call(cli, NLM_TEST_RES, xdr_nlm_testres, &res, xdr_void,
      &dummy, timeo);

    if (debug_level > 2) syslog(LOG_DEBUG, "clnt_call returns %d\n", success);
  }
  return (NULL);
}

/* nlm_lock ---------------------------------------------------------------- */
/*
   Purposes:	Establish a lock
   Returns:	granted, denied or blocked
   Notes:	*** grace period support missing
*/

nlm_res *nlm_lock_1_svc(nlm_lockargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;
  if (debug_level) log_from_addr("nlm_lock", rqstp);

  /* copy cookie from arg to result.  See comment in nlm_test_1()	*/
  res.cookie = arg->cookie;

  res.stat.stat = nlm_granted;
  return (&res);
}

void *nlm_lock_msg_1_svc(nlm_lockargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;

  if (debug_level) log_from_addr("nlm_lock_msg", rqstp);

  res.cookie = arg->cookie;
  res.stat.stat = nlm_granted;
  transmit_result(NLM_LOCK_RES, &res, rqstp);

  return (NULL);
}

/* nlm_cancel -------------------------------------------------------------- */
/*
   Purpose:	Cancel a blocked lock request
   Returns:	granted or denied
   Notes:
*/

nlm_res *nlm_cancel_1_svc(nlm_cancargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;
  if (debug_level) log_from_addr("nlm_cancel", rqstp);

  /* copy cookie from arg to result.  See comment in nlm_test_1()	*/
  res.cookie = arg->cookie;

  /* Since at present we never return 'nlm_blocked', there can never be	*/
  /* a lock to cancel, so this call always fails.			*/
  res.stat.stat = nlm_denied;
  return (&res);
}

void *nlm_cancel_msg_1_svc(nlm_cancargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;
  if (debug_level) log_from_addr("nlm_cancel_msg", rqstp);

  res.cookie = arg->cookie;
  /* Since at present we never return 'nlm_blocked', there can never be	*/
  /* a lock to cancel, so this call always fails.			*/
  res.stat.stat = nlm_denied;
  transmit_result(NLM_CANCEL_RES, &res, rqstp);
  return (NULL);
}

/* nlm_unlock -------------------------------------------------------------- */
/*
   Purpose:	Release an existing lock
   Returns:	Always granted, unless during grace period
   Notes:	"no such lock" error condition is ignored, as the
		protocol uses unreliable UDP datagrams, and may well
		re-try an unlock that has already succeeded.
*/

nlm_res *nlm_unlock_1_svc(nlm_unlockargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;
  if (debug_level) log_from_addr("nlm_unlock", rqstp);

  res.stat.stat= nlm_granted;
  res.cookie = arg->cookie;

  return (&res);
}

void *nlm_unlock_msg_1_svc(nlm_unlockargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;
  if (debug_level) log_from_addr("nlm_unlock_msg", rqstp);

  res.stat.stat = nlm_granted;
  res.cookie = arg->cookie;

  transmit_result(NLM_UNLOCK_RES, &res, rqstp);
  return (NULL);
}

/* ------------------------------------------------------------------------- */
/*
   Client-side pseudo-RPCs for results.  Note that for the client there
   are only nlm_xxx_msg() versions of each call, since the 'real RPC'
   version returns the results in the RPC result, and so the client
   does not normally receive incoming RPCs.

   The exception to this is nlm_granted(), which is genuinely an RPC
   call from the server to the client - a 'call-back' in normal procedure
   call terms.
*/

/* nlm_granted ------------------------------------------------------------- */
/*
   Purpose:	Receive notification that formerly blocked lock now granted
   Returns:	always success ('granted')
   Notes:	
*/

nlm_res *nlm_granted_1_svc(nlm_testargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;
  if (debug_level) log_from_addr("nlm_granted", rqstp);

  /* copy cookie from arg to result.  See comment in nlm_test_1()	*/
  res.cookie = arg->cookie;

  res.stat.stat = nlm_granted;
  return (&res);
}

void *nlm_granted_msg_1_svc(nlm_testargs *arg, struct svc_req *rqstp)
{
  nlm_res res;
  if (debug_level) log_from_addr("nlm_granted_msg", rqstp);

  res.cookie = arg->cookie;
  res.stat.stat = nlm_granted;
  transmit_result(NLM_GRANTED_RES, &res, rqstp);
  return (NULL);
}

/* nlm_test_res ------------------------------------------------------------ */
/*
   Purpose:	Accept result from earlier nlm_test_msg() call
   Returns:	Nothing
*/

void *nlm_test_res_1_svc(nlm_testres *arg, struct svc_req *rqstp)
{
  if (debug_level) log_from_addr("nlm_test_res", rqstp);
  return (NULL);
}

/* nlm_lock_res ------------------------------------------------------------ */
/*
   Purpose:	Accept result from earlier nlm_lock_msg() call
   Returns:	Nothing
*/

void *nlm_lock_res_1_svc(nlm_res *arg, struct svc_req *rqstp)
{
  if (debug_level) log_from_addr("nlm_lock_res", rqstp);

  return (NULL);
}

/* nlm_cancel_res ---------------------------------------------------------- */
/*
   Purpose:	Accept result from earlier nlm_cancel_msg() call
   Returns:	Nothing
*/

void *nlm_cancel_res_1_svc(nlm_res *arg, struct svc_req *rqstp)
{
  if (debug_level) log_from_addr("nlm_cancel_res", rqstp);
  return (NULL);
}

/* nlm_unlock_res ---------------------------------------------------------- */
/*
   Purpose:	Accept result from earlier nlm_unlock_msg() call
   Returns:	Nothing
*/

void *nlm_unlock_res_1_svc(nlm_res *arg, struct svc_req *rqstp)
{
  if (debug_level) log_from_addr("nlm_unlock_res", rqstp);
  return (NULL);
}

/* nlm_granted_res --------------------------------------------------------- */
/*
   Purpose:	Accept result from earlier nlm_granted_msg() call
   Returns:	Nothing
*/

void *nlm_granted_res_1_svc(nlm_res *arg, struct svc_req *rqstp)
{
  if (debug_level) log_from_addr("nlm_granted_res", rqstp);
  return (NULL);
}

/* ------------------------------------------------------------------------- */
/*
   Calls for PCNFS locking (aka non-monitored locking, no involvement
   of rpc.statd).

   These are all genuine RPCs - no nlm_xxx_msg() nonsense here.
*/


/* nlm_share --------------------------------------------------------------- */
/*
   Purpose:	Establish a DOS-style lock
   Returns:	success or failure
   Notes:	Blocking locks are not supported - client is expected
		to retry if required.
*/

nlm_shareres *nlm_share_3_svc(nlm_shareargs *arg, struct svc_req *rqstp)
{
  static nlm_shareres res;
  if (debug_level) log_from_addr("nlm_share", rqstp);

  res.cookie = arg->cookie;
  res.stat = nlm_granted;
  res.sequence = 1234356;	/* X/Open says this field is ignored?	*/
  return (&res);
}

/* nlm_unshare ------------------------------------------------------------ */
/*
   Purpose:	Release a DOS-style lock
   Returns:	nlm_granted, unless in grace period
   Notes:
*/

nlm_shareres *nlm_unshare_3_svc(nlm_shareargs *arg, struct svc_req *rqstp)
{
  static nlm_shareres res;
  if (debug_level) log_from_addr("nlm_unshare", rqstp);

  res.cookie = arg->cookie;
  res.stat = nlm_granted;
  res.sequence = 1234356;	/* X/Open says this field is ignored?	*/
  return (&res);
}

/* nlm_nm_lock ------------------------------------------------------------ */
/*
   Purpose:	non-monitored version of nlm_lock()
   Returns:	as for nlm_lock()
   Notes:	These locks are in the same style as the standard nlm_lock,
		but the rpc.statd should not be called to establish a
		monitor for the client machine, since that machine is
		declared not to be running a rpc.statd, and so would not
		respond to the statd protocol.
*/

nlm_res *nlm_nm_lock_3_svc(nlm_lockargs *arg, struct svc_req *rqstp)
{
  static nlm_res res;
  if (debug_level) log_from_addr("nlm_nm_lock", rqstp);

  /* copy cookie from arg to result.  See comment in nlm_test_1()	*/
  res.cookie = arg->cookie;
  res.stat.stat = nlm_granted;
  return (&res);
}

/* nlm_free_all ------------------------------------------------------------ */
/*
   Purpose:	Release all locks held by a named client
   Returns:	Nothing
   Notes:	Potential denial of service security problem here - the
		locks to be released are specified by a host name, independent
		of the address from which the request has arrived.
		Should probably be rejected if the named host has been
		using monitored locks.
*/

void *nlm_free_all_3_svc(nlm_notify *arg, struct svc_req *rqstp)
{
  static char dummy;

  if (debug_level) log_from_addr("nlm_free_all", rqstp);
  return (&dummy);
}