/* 
   Unix SMB/CIFS implementation.

   packet handling for mailslot requests. 
   
   Copyright (C) Andrew Tridgell 2005
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
   This implements "Class 2 mailslots", i.e. the communication mechanism 
   used for all mailslot packets smaller than 425 bytes. 

   "Class 1 mailslots" (which use SMB) are used for messages larger 
   than 426 bytes and are supported on some systems. These are not implemented
   in Samba4 yet, as there don't appear to be any core services that use
   them.

   425 and 426-byte sized messages are not supported at all.
*/

#include "includes.h"
#include "lib/events/events.h"
#include "../lib/util/dlinklist.h"
#include "libcli/dgram/libdgram.h"
#include "lib/socket/socket.h"

/*
  destroy a mailslot handler
*/
static int dgram_mailslot_destructor(struct dgram_mailslot_handler *dgmslot)
{
	DLIST_REMOVE(dgmslot->dgmsock->mailslot_handlers, dgmslot);
	return 0;
}

/*
  start listening on a mailslot. talloc_free() the handle to stop listening
*/
struct dgram_mailslot_handler *dgram_mailslot_listen(struct nbt_dgram_socket *dgmsock,
						     const char *mailslot_name,
						     dgram_mailslot_handler_t handler,
						     void *private_data)
{
	struct dgram_mailslot_handler *dgmslot;

	dgmslot = talloc(dgmsock, struct dgram_mailslot_handler);
	if (dgmslot == NULL) return NULL;

	dgmslot->dgmsock = dgmsock;
	dgmslot->mailslot_name = talloc_strdup(dgmslot, mailslot_name);
	if (dgmslot->mailslot_name == NULL) {
		talloc_free(dgmslot);
		return NULL;
	}
	dgmslot->handler = handler;
	dgmslot->private_data = private_data;

	DLIST_ADD(dgmsock->mailslot_handlers, dgmslot);
	talloc_set_destructor(dgmslot, dgram_mailslot_destructor);

	TEVENT_FD_READABLE(dgmsock->fde);

	return dgmslot;
}

/*
  find the handler for a specific mailslot name
*/
struct dgram_mailslot_handler *dgram_mailslot_find(struct nbt_dgram_socket *dgmsock,
						   const char *mailslot_name)
{
	struct dgram_mailslot_handler *h;
	for (h=dgmsock->mailslot_handlers;h;h=h->next) {
		if (strcasecmp(h->mailslot_name, mailslot_name) == 0) {
			return h;
		}
	}
	return NULL;
}

/*
  check that a datagram packet is a valid mailslot request, and return the 
  mailslot name if it is, otherwise return NULL
*/
const char *dgram_mailslot_name(struct nbt_dgram_packet *packet)
{
	if (packet->msg_type != DGRAM_DIRECT_UNIQUE &&
	    packet->msg_type != DGRAM_DIRECT_GROUP &&
	    packet->msg_type != DGRAM_BCAST) {
		return NULL;
	}
	if (packet->data.msg.dgram_body_type != DGRAM_SMB) return NULL;
	if (packet->data.msg.body.smb.smb_command != SMB_TRANSACTION) return NULL;
	return packet->data.msg.body.smb.body.trans.mailslot_name;
}


/*
  create a temporary mailslot handler for a reply mailslot, allocating
  a new mailslot name using the given base name and a random integer extension
*/
struct dgram_mailslot_handler *dgram_mailslot_temp(struct nbt_dgram_socket *dgmsock,
						   const char *mailslot_name,
						   dgram_mailslot_handler_t handler,
						   void *private_data)
{
	char *name;
	int i;
	struct dgram_mailslot_handler *dgmslot;

	/* try a 100 times at most */
	for (i=0;i<100;i++) {
		name = talloc_asprintf(dgmsock, "%s%03u", 
				       mailslot_name,
				       generate_random() % 1000);
		if (name == NULL) return NULL;
		if (dgram_mailslot_find(dgmsock, name)) {
			talloc_free(name);
			continue;
		}
		dgmslot = dgram_mailslot_listen(dgmsock, name, handler, private_data);
		talloc_free(name);
		if (dgmslot != NULL) {
			return dgmslot;
		}
	}
	DEBUG(2,("Unable to create temporary mailslot from %s\n", mailslot_name));
	return NULL;
}


/*
  send a mailslot request
*/
NTSTATUS dgram_mailslot_send(struct nbt_dgram_socket *dgmsock,
			     enum dgram_msg_type msg_type,
			     const char *mailslot_name,
			     struct nbt_name *dest_name,
			     struct socket_address *dest,
			     struct nbt_name *src_name,
			     DATA_BLOB *request)
{
	TALLOC_CTX *tmp_ctx = talloc_new(dgmsock);
	struct nbt_dgram_packet packet;
	struct dgram_message *msg;
	struct dgram_smb_packet *smb;
	struct smb_trans_body *trans;
	struct socket_address *src;
	NTSTATUS status;

	if (dest->port == 0) {
		return NT_STATUS_INVALID_PARAMETER;
	}

	ZERO_STRUCT(packet);
	packet.msg_type = msg_type;
	packet.flags = DGRAM_FLAG_FIRST | DGRAM_NODE_NBDD;
	packet.dgram_id = generate_random() % UINT16_MAX;
	src = socket_get_my_addr(dgmsock->sock, tmp_ctx);
	if (!src) {
		return NT_STATUS_NO_MEMORY;
	}
	packet.src_addr = src->addr;
	packet.src_port = src->port;

	msg = &packet.data.msg;
	/* this length calculation is very crude - it should be based on gensize
	   calls */
	msg->length = 138 + strlen(mailslot_name) + request->length;
	msg->offset = 0;

	msg->source_name = *src_name;
	msg->dest_name = *dest_name;
	msg->dgram_body_type = DGRAM_SMB;

	smb = &msg->body.smb;
	smb->smb_command = SMB_TRANSACTION;

	trans = &smb->body.trans;
	trans->total_data_count = request->length;
	trans->timeout     = 1000;
	trans->data_count  = request->length;
	trans->data_offset = 70 + strlen(mailslot_name);
	trans->opcode      = 1; /* write mail slot */
	trans->priority    = 1;
	trans->_class      = 2;
	trans->mailslot_name = mailslot_name;
	trans->data = *request;

	status = nbt_dgram_send(dgmsock, &packet, dest);

	talloc_free(tmp_ctx);

	return status;
}

/*
  return the mailslot data portion from a mailslot packet
*/
DATA_BLOB dgram_mailslot_data(struct nbt_dgram_packet *dgram)
{
	struct smb_trans_body *trans = &dgram->data.msg.body.smb.body.trans;
	DATA_BLOB ret = trans->data;
	int pad = trans->data_offset - (70 + strlen(trans->mailslot_name));

	if (pad < 0 || pad > ret.length) {
		DEBUG(2,("Badly formatted data in mailslot - pad = %d\n", pad));
		return data_blob(NULL, 0);
	}
	ret.data += pad;
	ret.length -= pad;
	return ret;	
}