/* 
   Unix SMB/CIFS implementation.
   process incoming packets - main loop
   Copyright (C) Andrew Tridgell 1992-2003
   Copyright (C) James J Myers 2003 <myersjj@samba.org>
   
   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 2 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"


/*
  send an oplock break request to a client
*/
BOOL req_send_oplock_break(struct tcon_context *conn, uint16_t fnum, uint8 level)
{
	struct request_context *req;

	req = init_smb_request(conn->smb);

	req_setup_reply(req, 8, 0);
	
	SCVAL(req->out.hdr,HDR_COM,SMBlockingX);
	SSVAL(req->out.hdr,HDR_TID,conn->cnum);
	SSVAL(req->out.hdr,HDR_PID,0xFFFF);
	SSVAL(req->out.hdr,HDR_UID,0);
	SSVAL(req->out.hdr,HDR_MID,0xFFFF);
	SCVAL(req->out.hdr,HDR_FLG,0);
	SSVAL(req->out.hdr,HDR_FLG2,0);

	SSVAL(req->out.vwv, VWV(0), SMB_CHAIN_NONE);
	SSVAL(req->out.vwv, VWV(1), 0);
	SSVAL(req->out.vwv, VWV(2), fnum);
	SCVAL(req->out.vwv, VWV(3), LOCKING_ANDX_OPLOCK_RELEASE);
	SCVAL(req->out.vwv, VWV(3)+1, level);
	SIVAL(req->out.vwv, VWV(4), 0);
	SSVAL(req->out.vwv, VWV(6), 0);
	SSVAL(req->out.vwv, VWV(7), 0);

	req_send_reply(req);
	return True;
}

/****************************************************************************
receive a SMB request from the wire, forming a request_context from the result
****************************************************************************/
static struct request_context *receive_smb_request(struct server_context *smb)
{
	ssize_t len, len2;
	char header[4];
	struct request_context *req;

	len = read_data(smb->socket.fd, header, 4);
	if (len != 4) {
		return NULL;
	}

	len = smb_len(header);

	req = init_smb_request(smb);

	GetTimeOfDay(&req->request_time);
	req->chained_fnum = -1;
	
	/* allocate the incoming buffer at the right size */
	req->in.buffer = talloc(req->mem_ctx, len + NBT_HDR_SIZE);

	/* fill in the already received header */
	memcpy(req->in.buffer, header, 4);

	len2 = read_data(smb->socket.fd, req->in.buffer + NBT_HDR_SIZE, len);
	if (len2 != len) {
		return NULL;
	}

	/* fill in the rest of the req->in structure */
	req->in.size = len + NBT_HDR_SIZE;
	req->in.allocated = req->in.size;
	req->in.hdr = req->in.buffer + NBT_HDR_SIZE;
	req->in.vwv = req->in.hdr + HDR_VWV;
	req->in.wct = CVAL(req->in.hdr, HDR_WCT);
	if (req->in.vwv + VWV(req->in.wct) <= req->in.buffer + req->in.size) {
		req->in.data = req->in.vwv + VWV(req->in.wct) + 2;
		req->in.data_size = SVAL(req->in.vwv, VWV(req->in.wct));

		/* the bcc length is only 16 bits, but some packets
		   (such as SMBwriteX) can be much larger than 64k. We
		   detect this by looking for a large non-chained NBT
		   packet (at least 64k bigger than what is
		   specified). If it is detected then the NBT size is
		   used instead of the bcc size */
		if (req->in.data_size + 0x10000 <= 
		    req->in.size - PTR_DIFF(req->in.data, req->in.buffer) &&
		    (req->in.wct < 1 || SVAL(req->in.vwv, VWV(0)) == SMB_CHAIN_NONE)) {
			/* its an oversized packet! fun for all the family */
			req->in.data_size = req->in.size - PTR_DIFF(req->in.data,req->in.buffer);
		}
	}

	return req;
}

/*
  setup the user_ctx element of a request
*/
static void setup_user_context(struct request_context *req)
{
	struct user_context *ctx;

	ctx = talloc(req->mem_ctx, sizeof(*ctx));
	ctx->vuid = SVAL(req->in.hdr, HDR_UID);
	ctx->vuser = get_valid_user_struct(req->smb, ctx->vuid);

	req->user_ctx = ctx;
}


/*
These flags determine some of the permissions required to do an operation 

Note that I don't set NEED_WRITE on some write operations because they
are used by some brain-dead clients when printing, and I don't want to
force write permissions on print services.
*/
#define AS_USER (1<<0)
#define NEED_WRITE (1<<1)
#define TIME_INIT (1<<2)
#define CAN_IPC (1<<3)
#define AS_GUEST (1<<5)
#define USE_MUTEX (1<<7)

/* 
   define a list of possible SMB messages and their corresponding
   functions. Any message that has a NULL function is unimplemented -
   please feel free to contribute implementations!
*/
static const struct smb_message_struct
{
	const char *name;
	void (*fn)(struct request_context *);
	int flags;
}
 smb_messages[256] = {
/* 0x00 */ { "SMBmkdir",reply_mkdir,AS_USER | NEED_WRITE},
/* 0x01 */ { "SMBrmdir",reply_rmdir,AS_USER | NEED_WRITE},
/* 0x02 */ { "SMBopen",reply_open,AS_USER },
/* 0x03 */ { "SMBcreate",reply_mknew,AS_USER},
/* 0x04 */ { "SMBclose",reply_close,AS_USER | CAN_IPC },
/* 0x05 */ { "SMBflush",reply_flush,AS_USER},
/* 0x06 */ { "SMBunlink",reply_unlink,AS_USER | NEED_WRITE },
/* 0x07 */ { "SMBmv",reply_mv,AS_USER | NEED_WRITE },
/* 0x08 */ { "SMBgetatr",reply_getatr,AS_USER},
/* 0x09 */ { "SMBsetatr",reply_setatr,AS_USER | NEED_WRITE},
/* 0x0a */ { "SMBread",reply_read,AS_USER},
/* 0x0b */ { "SMBwrite",reply_write,AS_USER | CAN_IPC },
/* 0x0c */ { "SMBlock",reply_lock,AS_USER},
/* 0x0d */ { "SMBunlock",reply_unlock,AS_USER},
/* 0x0e */ { "SMBctemp",reply_ctemp,AS_USER },
/* 0x0f */ { "SMBmknew",reply_mknew,AS_USER}, 
/* 0x10 */ { "SMBchkpth",reply_chkpth,AS_USER},
/* 0x11 */ { "SMBexit",reply_exit,0},
/* 0x12 */ { "SMBlseek",reply_lseek,AS_USER},
/* 0x13 */ { "SMBlockread",reply_lockread,AS_USER},
/* 0x14 */ { "SMBwriteunlock",reply_writeunlock,AS_USER},
/* 0x15 */ { NULL, NULL, 0 },
/* 0x16 */ { NULL, NULL, 0 },
/* 0x17 */ { NULL, NULL, 0 },
/* 0x18 */ { NULL, NULL, 0 },
/* 0x19 */ { NULL, NULL, 0 },
/* 0x1a */ { "SMBreadbraw",reply_readbraw,AS_USER},
/* 0x1b */ { "SMBreadBmpx",reply_readbmpx,AS_USER},
/* 0x1c */ { "SMBreadBs",NULL,0 },
/* 0x1d */ { "SMBwritebraw",reply_writebraw,AS_USER},
/* 0x1e */ { "SMBwriteBmpx",reply_writebmpx,AS_USER},
/* 0x1f */ { "SMBwriteBs",reply_writebs,AS_USER},
/* 0x20 */ { "SMBwritec",NULL,0},
/* 0x21 */ { NULL, NULL, 0 },
/* 0x22 */ { "SMBsetattrE",reply_setattrE,AS_USER | NEED_WRITE },
/* 0x23 */ { "SMBgetattrE",reply_getattrE,AS_USER },
/* 0x24 */ { "SMBlockingX",reply_lockingX,AS_USER },
/* 0x25 */ { "SMBtrans",reply_trans,AS_USER | CAN_IPC },
/* 0x26 */ { "SMBtranss",NULL,AS_USER | CAN_IPC},
/* 0x27 */ { "SMBioctl",reply_ioctl,0},
/* 0x28 */ { "SMBioctls",NULL,AS_USER},
/* 0x29 */ { "SMBcopy",reply_copy,AS_USER | NEED_WRITE },
/* 0x2a */ { "SMBmove",NULL,AS_USER | NEED_WRITE },
/* 0x2b */ { "SMBecho",reply_echo,0},
/* 0x2c */ { "SMBwriteclose",reply_writeclose,AS_USER},
/* 0x2d */ { "SMBopenX",reply_open_and_X,AS_USER | CAN_IPC },
/* 0x2e */ { "SMBreadX",reply_read_and_X,AS_USER | CAN_IPC },
/* 0x2f */ { "SMBwriteX",reply_write_and_X,AS_USER | CAN_IPC },
/* 0x30 */ { NULL, NULL, 0 },
/* 0x31 */ { NULL, NULL, 0 },
/* 0x32 */ { "SMBtrans2", reply_trans2, AS_USER | CAN_IPC },
/* 0x33 */ { "SMBtranss2", reply_transs2, AS_USER},
/* 0x34 */ { "SMBfindclose", reply_findclose,AS_USER},
/* 0x35 */ { "SMBfindnclose", reply_findnclose, AS_USER},
/* 0x36 */ { NULL, NULL, 0 },
/* 0x37 */ { NULL, NULL, 0 },
/* 0x38 */ { NULL, NULL, 0 },
/* 0x39 */ { NULL, NULL, 0 },
/* 0x3a */ { NULL, NULL, 0 },
/* 0x3b */ { NULL, NULL, 0 },
/* 0x3c */ { NULL, NULL, 0 },
/* 0x3d */ { NULL, NULL, 0 },
/* 0x3e */ { NULL, NULL, 0 },
/* 0x3f */ { NULL, NULL, 0 },
/* 0x40 */ { NULL, NULL, 0 },
/* 0x41 */ { NULL, NULL, 0 },
/* 0x42 */ { NULL, NULL, 0 },
/* 0x43 */ { NULL, NULL, 0 },
/* 0x44 */ { NULL, NULL, 0 },
/* 0x45 */ { NULL, NULL, 0 },
/* 0x46 */ { NULL, NULL, 0 },
/* 0x47 */ { NULL, NULL, 0 },
/* 0x48 */ { NULL, NULL, 0 },
/* 0x49 */ { NULL, NULL, 0 },
/* 0x4a */ { NULL, NULL, 0 },
/* 0x4b */ { NULL, NULL, 0 },
/* 0x4c */ { NULL, NULL, 0 },
/* 0x4d */ { NULL, NULL, 0 },
/* 0x4e */ { NULL, NULL, 0 },
/* 0x4f */ { NULL, NULL, 0 },
/* 0x50 */ { NULL, NULL, 0 },
/* 0x51 */ { NULL, NULL, 0 },
/* 0x52 */ { NULL, NULL, 0 },
/* 0x53 */ { NULL, NULL, 0 },
/* 0x54 */ { NULL, NULL, 0 },
/* 0x55 */ { NULL, NULL, 0 },
/* 0x56 */ { NULL, NULL, 0 },
/* 0x57 */ { NULL, NULL, 0 },
/* 0x58 */ { NULL, NULL, 0 },
/* 0x59 */ { NULL, NULL, 0 },
/* 0x5a */ { NULL, NULL, 0 },
/* 0x5b */ { NULL, NULL, 0 },
/* 0x5c */ { NULL, NULL, 0 },
/* 0x5d */ { NULL, NULL, 0 },
/* 0x5e */ { NULL, NULL, 0 },
/* 0x5f */ { NULL, NULL, 0 },
/* 0x60 */ { NULL, NULL, 0 },
/* 0x61 */ { NULL, NULL, 0 },
/* 0x62 */ { NULL, NULL, 0 },
/* 0x63 */ { NULL, NULL, 0 },
/* 0x64 */ { NULL, NULL, 0 },
/* 0x65 */ { NULL, NULL, 0 },
/* 0x66 */ { NULL, NULL, 0 },
/* 0x67 */ { NULL, NULL, 0 },
/* 0x68 */ { NULL, NULL, 0 },
/* 0x69 */ { NULL, NULL, 0 },
/* 0x6a */ { NULL, NULL, 0 },
/* 0x6b */ { NULL, NULL, 0 },
/* 0x6c */ { NULL, NULL, 0 },
/* 0x6d */ { NULL, NULL, 0 },
/* 0x6e */ { NULL, NULL, 0 },
/* 0x6f */ { NULL, NULL, 0 },
/* 0x70 */ { "SMBtcon",reply_tcon,USE_MUTEX},
/* 0x71 */ { "SMBtdis",reply_tdis,0},
/* 0x72 */ { "SMBnegprot",reply_negprot,USE_MUTEX},
/* 0x73 */ { "SMBsesssetupX",reply_sesssetup,USE_MUTEX},
/* 0x74 */ { "SMBulogoffX", reply_ulogoffX, 0}, /* ulogoff doesn't give a valid TID */
/* 0x75 */ { "SMBtconX",reply_tcon_and_X,USE_MUTEX},
/* 0x76 */ { NULL, NULL, 0 },
/* 0x77 */ { NULL, NULL, 0 },
/* 0x78 */ { NULL, NULL, 0 },
/* 0x79 */ { NULL, NULL, 0 },
/* 0x7a */ { NULL, NULL, 0 },
/* 0x7b */ { NULL, NULL, 0 },
/* 0x7c */ { NULL, NULL, 0 },
/* 0x7d */ { NULL, NULL, 0 },
/* 0x7e */ { NULL, NULL, 0 },
/* 0x7f */ { NULL, NULL, 0 },
/* 0x80 */ { "SMBdskattr",reply_dskattr,AS_USER},
/* 0x81 */ { "SMBsearch",reply_search,AS_USER},
/* 0x82 */ { "SMBffirst",reply_search,AS_USER},
/* 0x83 */ { "SMBfunique",reply_search,AS_USER},
/* 0x84 */ { "SMBfclose",reply_fclose,AS_USER},
/* 0x85 */ { NULL, NULL, 0 },
/* 0x86 */ { NULL, NULL, 0 },
/* 0x87 */ { NULL, NULL, 0 },
/* 0x88 */ { NULL, NULL, 0 },
/* 0x89 */ { NULL, NULL, 0 },
/* 0x8a */ { NULL, NULL, 0 },
/* 0x8b */ { NULL, NULL, 0 },
/* 0x8c */ { NULL, NULL, 0 },
/* 0x8d */ { NULL, NULL, 0 },
/* 0x8e */ { NULL, NULL, 0 },
/* 0x8f */ { NULL, NULL, 0 },
/* 0x90 */ { NULL, NULL, 0 },
/* 0x91 */ { NULL, NULL, 0 },
/* 0x92 */ { NULL, NULL, 0 },
/* 0x93 */ { NULL, NULL, 0 },
/* 0x94 */ { NULL, NULL, 0 },
/* 0x95 */ { NULL, NULL, 0 },
/* 0x96 */ { NULL, NULL, 0 },
/* 0x97 */ { NULL, NULL, 0 },
/* 0x98 */ { NULL, NULL, 0 },
/* 0x99 */ { NULL, NULL, 0 },
/* 0x9a */ { NULL, NULL, 0 },
/* 0x9b */ { NULL, NULL, 0 },
/* 0x9c */ { NULL, NULL, 0 },
/* 0x9d */ { NULL, NULL, 0 },
/* 0x9e */ { NULL, NULL, 0 },
/* 0x9f */ { NULL, NULL, 0 },
/* 0xa0 */ { "SMBnttrans", reply_nttrans, AS_USER | CAN_IPC },
/* 0xa1 */ { "SMBnttranss", reply_nttranss, AS_USER | CAN_IPC },
/* 0xa2 */ { "SMBntcreateX", reply_ntcreate_and_X, AS_USER | CAN_IPC },
/* 0xa3 */ { NULL, NULL, 0 },
/* 0xa4 */ { "SMBntcancel", reply_ntcancel, 0 },
/* 0xa5 */ { "SMBntrename", reply_ntrename, 0 },
/* 0xa6 */ { NULL, NULL, 0 },
/* 0xa7 */ { NULL, NULL, 0 },
/* 0xa8 */ { NULL, NULL, 0 },
/* 0xa9 */ { NULL, NULL, 0 },
/* 0xaa */ { NULL, NULL, 0 },
/* 0xab */ { NULL, NULL, 0 },
/* 0xac */ { NULL, NULL, 0 },
/* 0xad */ { NULL, NULL, 0 },
/* 0xae */ { NULL, NULL, 0 },
/* 0xaf */ { NULL, NULL, 0 },
/* 0xb0 */ { NULL, NULL, 0 },
/* 0xb1 */ { NULL, NULL, 0 },
/* 0xb2 */ { NULL, NULL, 0 },
/* 0xb3 */ { NULL, NULL, 0 },
/* 0xb4 */ { NULL, NULL, 0 },
/* 0xb5 */ { NULL, NULL, 0 },
/* 0xb6 */ { NULL, NULL, 0 },
/* 0xb7 */ { NULL, NULL, 0 },
/* 0xb8 */ { NULL, NULL, 0 },
/* 0xb9 */ { NULL, NULL, 0 },
/* 0xba */ { NULL, NULL, 0 },
/* 0xbb */ { NULL, NULL, 0 },
/* 0xbc */ { NULL, NULL, 0 },
/* 0xbd */ { NULL, NULL, 0 },
/* 0xbe */ { NULL, NULL, 0 },
/* 0xbf */ { NULL, NULL, 0 },
/* 0xc0 */ { "SMBsplopen",reply_printopen,AS_USER },
/* 0xc1 */ { "SMBsplwr",reply_printwrite,AS_USER},
/* 0xc2 */ { "SMBsplclose",reply_printclose,AS_USER},
/* 0xc3 */ { "SMBsplretq",reply_printqueue,AS_USER},
/* 0xc4 */ { NULL, NULL, 0 },
/* 0xc5 */ { NULL, NULL, 0 },
/* 0xc6 */ { NULL, NULL, 0 },
/* 0xc7 */ { NULL, NULL, 0 },
/* 0xc8 */ { NULL, NULL, 0 },
/* 0xc9 */ { NULL, NULL, 0 },
/* 0xca */ { NULL, NULL, 0 },
/* 0xcb */ { NULL, NULL, 0 },
/* 0xcc */ { NULL, NULL, 0 },
/* 0xcd */ { NULL, NULL, 0 },
/* 0xce */ { NULL, NULL, 0 },
/* 0xcf */ { NULL, NULL, 0 },
/* 0xd0 */ { "SMBsends",reply_sends,AS_GUEST},
/* 0xd1 */ { "SMBsendb",NULL,AS_GUEST},
/* 0xd2 */ { "SMBfwdname",NULL,AS_GUEST},
/* 0xd3 */ { "SMBcancelf",NULL,AS_GUEST},
/* 0xd4 */ { "SMBgetmac",NULL,AS_GUEST},
/* 0xd5 */ { "SMBsendstrt",reply_sendstrt,AS_GUEST},
/* 0xd6 */ { "SMBsendend",reply_sendend,AS_GUEST},
/* 0xd7 */ { "SMBsendtxt",reply_sendtxt,AS_GUEST},
/* 0xd8 */ { NULL, NULL, 0 },
/* 0xd9 */ { NULL, NULL, 0 },
/* 0xda */ { NULL, NULL, 0 },
/* 0xdb */ { NULL, NULL, 0 },
/* 0xdc */ { NULL, NULL, 0 },
/* 0xdd */ { NULL, NULL, 0 },
/* 0xde */ { NULL, NULL, 0 },
/* 0xdf */ { NULL, NULL, 0 },
/* 0xe0 */ { NULL, NULL, 0 },
/* 0xe1 */ { NULL, NULL, 0 },
/* 0xe2 */ { NULL, NULL, 0 },
/* 0xe3 */ { NULL, NULL, 0 },
/* 0xe4 */ { NULL, NULL, 0 },
/* 0xe5 */ { NULL, NULL, 0 },
/* 0xe6 */ { NULL, NULL, 0 },
/* 0xe7 */ { NULL, NULL, 0 },
/* 0xe8 */ { NULL, NULL, 0 },
/* 0xe9 */ { NULL, NULL, 0 },
/* 0xea */ { NULL, NULL, 0 },
/* 0xeb */ { NULL, NULL, 0 },
/* 0xec */ { NULL, NULL, 0 },
/* 0xed */ { NULL, NULL, 0 },
/* 0xee */ { NULL, NULL, 0 },
/* 0xef */ { NULL, NULL, 0 },
/* 0xf0 */ { NULL, NULL, 0 },
/* 0xf1 */ { NULL, NULL, 0 },
/* 0xf2 */ { NULL, NULL, 0 },
/* 0xf3 */ { NULL, NULL, 0 },
/* 0xf4 */ { NULL, NULL, 0 },
/* 0xf5 */ { NULL, NULL, 0 },
/* 0xf6 */ { NULL, NULL, 0 },
/* 0xf7 */ { NULL, NULL, 0 },
/* 0xf8 */ { NULL, NULL, 0 },
/* 0xf9 */ { NULL, NULL, 0 },
/* 0xfa */ { NULL, NULL, 0 },
/* 0xfb */ { NULL, NULL, 0 },
/* 0xfc */ { NULL, NULL, 0 },
/* 0xfd */ { NULL, NULL, 0 },
/* 0xfe */ { NULL, NULL, 0 },
/* 0xff */ { NULL, NULL, 0 }
};

/****************************************************************************
return a string containing the function name of a SMB command
****************************************************************************/
static const char *smb_fn_name(uint8 type)
{
	const char *unknown_name = "SMBunknown";

	if (smb_messages[type].name == NULL)
		return unknown_name;

	return smb_messages[type].name;
}


/****************************************************************************
 Do a switch on the message type and call the specific reply function for this 
message. Unlike earlier versions of Samba the reply functions are responsible
for sending the reply themselves, rather than returning a size to this function
The reply functions may also choose to delay the processing by pushing the message
onto the message queue
****************************************************************************/
static void switch_message(int type, struct request_context *req)
{
	int flags;
	uint16_t session_tag;
	struct server_context *smb = req->smb;

	type &= 0xff;

	errno = 0;

	if (smb_messages[type].fn == NULL) {
		DEBUG(0,("Unknown message type %d!\n",type));
		reply_unknown(req);
		return;
	}

	flags = smb_messages[type].flags;

	/* In share mode security we must ignore the vuid. */
	session_tag = (lp_security() == SEC_SHARE) ? 
		UID_FIELD_INVALID : 
		SVAL(req->in.hdr,HDR_UID);

	req->conn = conn_find(req->smb, SVAL(req->in.hdr,HDR_TID));

	/* setup the user context for this request */
	setup_user_context(req);

	/* Ensure this value is replaced in the incoming packet. */
	SSVAL(req->in.hdr,HDR_UID,session_tag);

	if (req->user_ctx) {
		req->user_ctx->vuid = session_tag;
	}
	DEBUG(3,("switch message %s (task_id %d)\n",smb_fn_name(type), smb->model_ops->get_id(req)));

	/* does this protocol need to be run as root? */
	if (!(flags & AS_USER)) {
		change_to_root_user();
	}
	
	/* does this protocol need a valid tree connection? */
	if ((flags & AS_USER) && !req->conn) {
		req_reply_error(req, NT_STATUS_NETWORK_NAME_DELETED);
		return;
	}

	/* see if the vuid is valid */
	if ((flags & AS_USER) && !req->user_ctx->vuser) {
		if (!(flags & AS_GUEST)) {
			req_reply_error(req, NT_STATUS_DOS(ERRSRV, ERRbaduid));
			return;
		}
	}

	/* does this protocol need to be run as the connected user? */
#if HACK_REWRITE
	if ((flags & AS_USER) && !change_to_user(req->conn,session_tag)) {
		if (!(flags & AS_GUEST)) {
			req_reply_error(req, NT_STATUS_ACCESS_DENIED);
			return;
		}

		/* we'll run it as guest */
		flags &= ~AS_USER;
	}
#endif

	/* this code is to work around a bug is MS client 3 without
	   introducing a security hole - it needs to be able to do
	   print queue checks as guest if it isn't logged in properly */
	if (flags & AS_USER) {
		flags &= ~AS_GUEST;
	}
	
	/* does it need write permission? */
	if ((flags & NEED_WRITE) && !CAN_WRITE(req->conn)) {
		req_reply_error(req, NT_STATUS_ACCESS_DENIED);
		return;
	}
	
	/* ipc services are limited */
	if (req->conn && req->conn->type == NTVFS_IPC && (flags & AS_USER) && !(flags & CAN_IPC)) {
		req_reply_error(req, NT_STATUS_ACCESS_DENIED);
		return;
	}
	
	/* load service specific parameters */
	if (req->conn && !set_current_service(req->conn,(flags & AS_USER)?True:False)) {
		req_reply_error(req, NT_STATUS_ACCESS_DENIED);
		return;
	}
	
	/* does this protocol need to be run as guest? */
#if HACK_REWRITE
	if ((flags & AS_GUEST) && 
	    !change_to_guest()) {
		req_reply_error(req, NT_STATUS_ACCESS_DENIED);
		return;
	}
#endif
	/* THREAD TESTING: use mutex to serialize calls to critical functions with global state */
	if (flags & USE_MUTEX) {
		MUTEX_LOCK_BY_ID(MUTEX_SMBD);
	}
	smb_messages[type].fn(req);
	if (flags & USE_MUTEX) {
		MUTEX_UNLOCK_BY_ID(MUTEX_SMBD);
	}
}


/****************************************************************************
 Construct a reply to the incoming packet.
****************************************************************************/
static void construct_reply(struct request_context *req)
{
	uint8 type = CVAL(req->in.hdr,HDR_COM);

	/* see if its a special NBT packet */
	if (CVAL(req->in.buffer,0) != 0) {
		reply_special(req);
		return;
	}

	/* Make sure this is an SMB packet */	
	if (memcmp(req->in.hdr,"\377SMB",4) != 0) {
		DEBUG(2,("Non-SMB packet of length %d. Terminating connection\n", 
			 req->in.size));
		exit_server(req->smb, "Non-SMB packet");
		return;
	}

	if (NBT_HDR_SIZE + MIN_SMB_SIZE + 2*req->in.wct > req->in.size) {
		DEBUG(2,("Invalid SMB word count %d\n", req->in.wct));
		exit_server(req->smb, "Invalid SMB packet");
		return;
	}

	if (NBT_HDR_SIZE + MIN_SMB_SIZE + 2*req->in.wct + req->in.data_size > req->in.size) {
		DEBUG(2,("Invalid SMB buffer length count %d\n", req->in.data_size));
		exit_server(req->smb, "Invalid SMB packet");
		return;
	}


	req->smbpid = SVAL(req->in.hdr,HDR_PID);	
	req->flags = CVAL(req->in.hdr, HDR_FLG);
	req->flags2 = SVAL(req->in.hdr, HDR_FLG2);

	if (!req_signing_check_incoming(req)) {
		req_reply_error(req, NT_STATUS_ACCESS_DENIED);
		return;
	}

	switch_message(type, req);
}


/*
  we call this when first first part of a possibly chained request has been completed
  and we need to call the 2nd part, if any
*/
void chain_reply(struct request_context *req)
{
	uint16_t chain_cmd, chain_offset;
	char *vwv, *data;
	uint16_t wct;
	uint16_t data_size;

	if (req->in.wct < 2 || req->out.wct < 2) {
		req_reply_dos_error(req, ERRSRV, ERRerror);
		return;
	}

	chain_cmd    = CVAL(req->in.vwv, VWV(0));
	chain_offset = SVAL(req->in.vwv, VWV(1));

	if (chain_cmd == SMB_CHAIN_NONE) {
		/* end of chain */
		SSVAL(req->out.vwv, VWV(0), SMB_CHAIN_NONE);
		SSVAL(req->out.vwv, VWV(1), 0);
		req_send_reply(req);
		return;
	}

	if (chain_offset + req->in.hdr >= req->in.buffer + req->in.size) {
		goto error;
	}

	wct = CVAL(req->in.hdr, chain_offset);
	vwv = req->in.hdr + chain_offset + 1;

	if (vwv + VWV(wct) + 2 > req->in.buffer + req->in.size) {
		goto error;
	}

	data_size = SVAL(vwv, VWV(wct));
	data = vwv + VWV(wct) + 2;

	if (data + data_size > req->in.buffer + req->in.size) {
		goto error;
	}

	/* all seems legit */
	req->in.vwv = vwv;
	req->in.wct = wct;
	req->in.data = data;
	req->in.data_size = data_size;
	req->in.ptr = data;

	req->chain_count++;

	SSVAL(req->out.vwv, VWV(0), chain_cmd);
	SSVAL(req->out.vwv, VWV(1), req->out.size - NBT_HDR_SIZE);

	/* the current request in the chain might have used an async reply,
	   but that doesn't mean the next element needs to */
	ZERO_STRUCT(req->async);
	req->control_flags &= ~REQ_CONTROL_ASYNC;

	switch_message(chain_cmd, req);
	return;

error:
	SSVAL(req->out.vwv, VWV(0), SMB_CHAIN_NONE);
	SSVAL(req->out.vwv, VWV(1), 0);
	req_reply_dos_error(req, ERRSRV, ERRerror);
}


/*
  close the socket and shutdown a server_context
*/
void server_terminate(struct server_context *smb)
{
	close(smb->socket.fd);
	event_remove_fd_all(smb->events, smb->socket.fd);

	conn_close_all(smb);

	talloc_destroy(smb->mem_ctx);
}


/*
  called when a SMB socket becomes readable
*/
void smbd_read_handler(struct event_context *ev, struct fd_event *fde, 
		       time_t t, uint16_t flags)
{
	struct request_context *req;
	struct server_context *smb = fde->private;
	
	req = receive_smb_request(smb);
	if (!req) {
		smb->model_ops->terminate_connection(smb, "receive error");
		return;
	}

	construct_reply(req);

	/* free up temporary memory */
	lp_talloc_free();
}


/*
  process a message from an SMB socket while still processing a
  previous message this is used by backends who need to ensure that
  new messages from clients are still processed while they are
  performing long operations
*/
void smbd_process_async(struct server_context *smb)
{
	struct request_context *req;
	
	req = receive_smb_request(smb);
	if (!req) {
		smb->model_ops->terminate_connection(smb, "receive error");
		return;
	}

	construct_reply(req);
}


/*
  initialise a server_context from a open socket and register a event handler
  for reading from that socket
*/
void init_smbsession(struct event_context *ev, struct model_ops *model_ops, int fd,
		     void (*read_handler)(struct event_context *, struct fd_event *, time_t, uint16_t))
{
	struct server_context *smb;
	TALLOC_CTX *mem_ctx;
	struct fd_event fde;
	char *socket_addr;

	set_socket_options(fd,"SO_KEEPALIVE");
	set_socket_options(fd, lp_socket_options());

	mem_ctx = talloc_init("server_context");

	smb = talloc_p(mem_ctx, struct server_context);
	if (!smb) return;

	ZERO_STRUCTP(smb);

	smb->mem_ctx = mem_ctx;
	smb->socket.fd = fd;
	smb->pid = getpid();

	sub_set_context(&smb->substitute);

	/* set an initial client name based on its IP address. This will be replaced with
	   the netbios name later if it gives us one */
	socket_addr = get_socket_addr(smb->mem_ctx, fd);
	sub_set_remote_machine(socket_addr);
	smb->socket.client_addr = socket_addr;

	/* now initialise a few default values associated with this smb socket */
	smb->negotiate.max_send = 0xFFFF;

	/* this is the size that w2k uses, and it appears to be important for
	   good performance */
	smb->negotiate.max_recv = lp_max_xmit();

	smb->negotiate.zone_offset = get_time_zone(time(NULL));

	smb->users.next_vuid = VUID_OFFSET;
	
	smb->events = ev;
	smb->model_ops = model_ops;

	conn_init(smb);

	/* setup a event handler for this socket. We are initially
	   only interested in reading from the socket */
	fde.fd = fd;
	fde.handler = read_handler;
	fde.private = smb;
	fde.flags = EVENT_FD_READ;

	event_add_fd(ev, &fde);

	/* setup the DCERPC server subsystem */
	dcesrv_init_context(&smb->dcesrv);
}