/* tcps_sess.c
 *
 * This implements a session of the tcpsrv object. For general
 * comments, see header of tcpsrv.c.
 *
 * NOTE: read comments in module-template.h to understand how this file
 *       works!
 *
 * File begun on 2008-03-01 by RGerhards (extracted from tcpsrv.c)
 *
 * Copyright 2007, 2008 Rainer Gerhards and Adiscon GmbH.
 *
 * This file is part of rsyslog.
 *
 * Rsyslog 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.
 *
 * Rsyslog 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 Rsyslog.  If not, see <http://www.gnu.org/licenses/>.
 *
 * A copy of the GPL can be found in the file "COPYING" in this distribution.
 */

#include "config.h"
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdarg.h>
#include <ctype.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#if HAVE_FCNTL_H
#include <fcntl.h>
#endif
#include "rsyslog.h"
#include "syslogd.h"
#include "module-template.h"
#include "net.h"
#include "tcpsrv.h"
#include "tcps_sess.h"
#include "obj.h"
#include "errmsg.h"


/* static data */
DEFobjStaticHelpers
DEFobjCurrIf(errmsg)

/* Standard-Constructor
 */
BEGINobjConstruct(tcps_sess) /* be sure to specify the object type also in END macro! */
		pThis->sock = -1; /* no sock */
		pThis->iMsg = 0; /* just make sure... */
		pThis->bAtStrtOfFram = 1; /* indicate frame header expected */
		pThis->eFraming = TCP_FRAMING_OCTET_STUFFING; /* just make sure... */
ENDobjConstruct(tcps_sess)


/* ConstructionFinalizer
 */
static rsRetVal
tcps_sessConstructFinalize(tcps_sess_t __attribute__((unused)) *pThis)
{
	DEFiRet;
RUNLOG_VAR("%p", pThis->objData.pszName);
	ISOBJ_TYPE_assert(pThis, tcps_sess);
	if(pThis->pSrv->OnSessConstructFinalize != NULL) {
		CHKiRet(pThis->pSrv->OnSessConstructFinalize(&pThis->pUsr));
	}

finalize_it:
	RETiRet;
}


/* destructor for the tcps_sess object */
BEGINobjDestruct(tcps_sess) /* be sure to specify the object type also in END and CODESTART macros! */
CODESTARTobjDestruct(tcps_sess)
RUNLOG_VAR("%p", pThis->objData.pszName);
	if(pThis->pSrv->pOnSessDestruct != NULL) {
		pThis->pSrv->pOnSessDestruct(&pThis->pUsr);
	}
	/* now destruct our own properties */
	if(pThis->fromHost != NULL)
		free(pThis->fromHost);
	close(pThis->sock);
ENDobjDestruct(tcps_sess)


/* debugprint for the tcps_sess object */
BEGINobjDebugPrint(tcps_sess) /* be sure to specify the object type also in END and CODESTART macros! */
CODESTARTobjDebugPrint(tcps_sess)
ENDobjDebugPrint(tcps_sess)


/* set property functions */
static rsRetVal
SetHost(tcps_sess_t *pThis, uchar *pszHost)
{
	DEFiRet;

	ISOBJ_TYPE_assert(pThis, tcps_sess);
RUNLOG_VAR("%p", pThis->objData.pszName);

	if(pThis->fromHost != NULL) {
		free(pThis->fromHost);
		pThis->fromHost = NULL;
	}
	
	if((pThis->fromHost = strdup((char*)pszHost)) == NULL)
		ABORT_FINALIZE(RS_RET_OUT_OF_MEMORY);

finalize_it:
	RETiRet;
}

static rsRetVal
SetSock(tcps_sess_t *pThis, int sock)
{
	DEFiRet;
	ISOBJ_TYPE_assert(pThis, tcps_sess);
	pThis->sock = sock;
	RETiRet;
}

static rsRetVal
SetMsgIdx(tcps_sess_t *pThis, int idx)
{
	DEFiRet;
	ISOBJ_TYPE_assert(pThis, tcps_sess);
	pThis->iMsg = idx;
	RETiRet;
}


/* set out parent, the tcpsrv object */
static rsRetVal
SetTcpsrv(tcps_sess_t *pThis, tcpsrv_t *pSrv)
{
	DEFiRet;
RUNLOG_VAR("%p", pThis->objData.pszName);
	ISOBJ_TYPE_assert(pThis, tcps_sess);
	ISOBJ_TYPE_assert(pSrv, tcpsrv);
	pThis->pSrv = pSrv;
RUNLOG_VAR("%p", pThis->objData.pszName);
	RETiRet;
}


static rsRetVal
SetUsrP(tcps_sess_t *pThis, void *pUsr)
{
	DEFiRet;
	pThis->pUsr = pUsr;
	RETiRet;
}


/* This should be called before a normal (non forced) close
 * of a TCP session. This function checks if there is any unprocessed
 * message left in the TCP stream. Such a message is probably a
 * fragement. If evrything goes well, we must be right at the
 * beginnig of a new frame without any data received from it. If
 * not, there is some kind of a framing error. I think I remember that
 * some legacy syslog/TCP implementations have non-LF terminated
 * messages at the end of the stream. For now, we allow this behaviour.
 * Later, it should probably become a configuration option.
 * rgerhards, 2006-12-07
 */
static rsRetVal
PrepareClose(tcps_sess_t *pThis)
{
	DEFiRet;

	ISOBJ_TYPE_assert(pThis, tcps_sess);
	
	if(pThis->bAtStrtOfFram == 1) {
		/* this is how it should be. There is no unprocessed
		 * data left and such we have nothing to do. For simplicity
		 * reasons, we immediately return in that case.
		 */
		 FINALIZE;
	}

	/* we have some data left! */
	if(pThis->eFraming == TCP_FRAMING_OCTET_COUNTING) {
		/* In this case, we have an invalid frame count and thus
		 * generate an error message and discard the frame.
		 */
		errmsg.LogError(NO_ERRCODE, "Incomplete frame at end of stream in session %d - "
			    "ignoring extra data (a message may be lost).\n",
			    pThis->sock);
		/* nothing more to do */
	} else { /* here, we have traditional framing. Missing LF at the end
		 * of message may occur. As such, we process the message in
		 * this case.
		 */
		dbgprintf("Extra data at end of stream in legacy syslog/tcp message - processing\n");
		parseAndSubmitMessage(pThis->fromHost, pThis->msg,
			              pThis->iMsg, MSG_PARSE_HOSTNAME);
		pThis->bAtStrtOfFram = 1;
	}

finalize_it:
	RETiRet;
}


/* Closes a TCP session and marks its slot in the session
 * table as unused. No attention is paid to the return code
 * of close, so potential-double closes are not detected.
 */
static rsRetVal
Close(tcps_sess_t *pThis)
{
	DEFiRet;

	ISOBJ_TYPE_assert(pThis, tcps_sess);
	close(pThis->sock);
	pThis->sock = -1;
	free(pThis->fromHost);
	pThis->fromHost = NULL; /* not really needed, but... */

	RETiRet;
}


/* Processes the data received via a TCP session. If there
 * is no other way to handle it, data is discarded.
 * Input parameter data is the data received, iLen is its
 * len as returned from recv(). iLen must be 1 or more (that
 * is errors must be handled by caller!). iTCPSess must be
 * the index of the TCP session that received the data.
 * rgerhards 2005-07-04
 * Changed this functions interface. We now return a status of
 * what shall happen with the session. This is information for
 * the caller. If 1 is returned, the session should remain open
 * and additional data be accepted. If we return 0, the TCP
 * session is to be closed by the caller. This functionality is
 * needed in order to support framing errors, from which there
 * is no recovery possible other than session termination and
 * re-establishment. The need for this functionality thus is
 * primarily rooted in support for -transport-tls I-D framing.
 * rgerhards, 2006-12-07
 * And another change while generalizing. We now return either
 * RS_RET_OK, which means the session should be kept open
 * or anything else, which means it must be closed.
 * rgerhards, 2008-03-01
 */
static rsRetVal
DataRcvd(tcps_sess_t *pThis, char *pData, size_t iLen)
{
	DEFiRet;
	register int iMsg;
	char *pMsg;
	char *pEnd;

	ISOBJ_TYPE_assert(pThis, tcps_sess);
	assert(pData != NULL);
	assert(iLen > 0);

	 /* We now copy the message to the session buffer. As
	  * it looks, we need to do this in any case because
	  * we might run into multiple messages inside a single
	  * buffer. Of course, we could think about optimizations,
	  * but as this code is to be replaced by liblogging, it
	  * probably doesn't make so much sense...
	  * rgerhards 2005-07-04
	  *
	  * Algo:
	  * - copy message to buffer until the first LF is found
	  * - printline() the buffer
	  * - continue with copying
	  */
	iMsg = pThis->iMsg; /* copy for speed */
	pMsg = pThis->msg; /* just a shortcut */
	pEnd = pData + iLen; /* this is one off, which is intensional */

	while(pData < pEnd) {
		/* Check if we are at a new frame */
		if(pThis->bAtStrtOfFram) {
			/* we need to look at the message and detect
			 * the framing mode used
			 *//*
			 * Contrary to -transport-tls, we accept leading zeros in the message
			 * length. We do this in the spirit of "Be liberal in what you accept,
			 * and conservative in what you send". We expect that including leading
			 * zeros could be a common coding error.
			 * rgerhards, 2006-12-07
			 * The chairs of the IETF syslog-sec WG have announced that it is
			 * consensus to do the octet count on the SYSLOG-MSG part only. I am
			 * now changing the code to reflect this. Hopefully, it will not change
			 * once again (there can no compatibility layer programmed for this).
			 * To be on the save side, I just comment the code out. I mark these
			 * comments with "IETF20061218".
			 * rgerhards, 2006-12-19
			 */
			if(isdigit((int) *pData)) {
				int iCnt;	/* the frame count specified */
				pThis->eFraming = TCP_FRAMING_OCTET_COUNTING;
				/* in this mode, we have OCTET-COUNT SP MSG - so we now need
				 * to extract the OCTET-COUNT and the SP and then extract
				 * the msg.
				 */
				iCnt = 0;
				/* IETF20061218 int iNbrOctets = 0; / * number of octets already consumed */
				while(isdigit((int) *pData)) {
					iCnt = iCnt * 10 + *pData - '0';
					/* IETF20061218 ++iNbrOctets; */
					++pData;
				}
				dbgprintf("TCP Message with octet-counter, size %d.\n", iCnt);
				if(*pData == ' ') {
					++pData;	/* skip over SP */
					/* IETF20061218 ++iNbrOctets; */
				} else {
					/* TODO: handle "invalid frame" case */
					errmsg.LogError(NO_ERRCODE, "Framing Error in received TCP message: "
					            "delimiter is not SP but has ASCII value %d.\n",
						    *pData);
					return(0); /* unconditional error exit */
				}
				/* IETF20061218 pThis->iOctetsRemain = iCnt - iNbrOctets; */
				pThis->iOctetsRemain = iCnt;
				if(pThis->iOctetsRemain < 1) {
					/* TODO: handle the case where the octet count is 0 or negative! */
					dbgprintf("Framing Error: invalid octet count\n");
					errmsg.LogError(NO_ERRCODE, "Framing Error in received TCP message: "
					            "invalid octet count %d.\n",
				 		    pThis->iOctetsRemain);
					return(0); /* unconditional error exit */
				}
			} else {
				pThis->eFraming = TCP_FRAMING_OCTET_STUFFING;
				/* No need to do anything else here in this case */
			}
			pThis->bAtStrtOfFram = 0; /* done frame header */
		}
	
		/* now copy message until end of record */

		if(iMsg >= MAXLINE) {
			/* emergency, we now need to flush, no matter if
			 * we are at end of message or not...
			 */
			parseAndSubmitMessage(pThis->fromHost, pMsg, iMsg, MSG_PARSE_HOSTNAME);
			iMsg = 0;
			/* we might think if it is better to ignore the rest of the
		 	 * message than to treat it as a new one. Maybe this is a good
			 * candidate for a configuration parameter...
			 * rgerhards, 2006-12-04
			 */
		}

		if(*pData == '\n' &&
		   pThis->eFraming == TCP_FRAMING_OCTET_STUFFING) { /* record delemiter? */
			parseAndSubmitMessage(pThis->fromHost, pMsg, iMsg, MSG_PARSE_HOSTNAME);
			iMsg = 0;
			pThis->bAtStrtOfFram = 1;
			++pData;
		} else {
			/* IMPORTANT: here we copy the actual frame content to the message! */
			*(pMsg + iMsg++) = *pData++;
		}

		if(pThis->eFraming == TCP_FRAMING_OCTET_COUNTING) {
			/* do we need to find end-of-frame via octet counting? */
			pThis->iOctetsRemain--;
			if(pThis->iOctetsRemain < 1) {
				/* we have end of frame! */
				parseAndSubmitMessage(pThis->fromHost, pMsg, iMsg, MSG_PARSE_HOSTNAME);
				iMsg = 0;
				pThis->bAtStrtOfFram = 1;
			}
		}
	}

	pThis->iMsg = iMsg; /* persist value */

	return(1);	/* successful return */
	RETiRet;
}


/* queryInterface function
 * rgerhards, 2008-02-29
 */
BEGINobjQueryInterface(tcps_sess)
CODESTARTobjQueryInterface(tcps_sess)
	if(pIf->ifVersion != tcps_sessCURR_IF_VERSION) { /* check for current version, increment on each change */
		ABORT_FINALIZE(RS_RET_INTERFACE_NOT_SUPPORTED);
	}

	/* ok, we have the right interface, so let's fill it
	 * Please note that we may also do some backwards-compatibility
	 * work here (if we can support an older interface version - that,
	 * of course, also affects the "if" above).
	 */
	pIf->DebugPrint = tcps_sessDebugPrint;
	pIf->Construct = tcps_sessConstruct;
	pIf->ConstructFinalize = tcps_sessConstructFinalize;
	pIf->Destruct = tcps_sessDestruct;

	pIf->PrepareClose = PrepareClose;
	pIf->Close = Close;
	pIf->DataRcvd = DataRcvd;

	pIf->SetUsrP = SetUsrP;
	pIf->SetTcpsrv = SetTcpsrv;
	pIf->SetHost = SetHost;
	pIf->SetSock = SetSock;
	pIf->SetMsgIdx = SetMsgIdx;
finalize_it:
ENDobjQueryInterface(tcps_sess)


/* Initialize our class. Must be called as the very first method
 * before anything else is called inside this class.
 * rgerhards, 2008-02-29
 */
BEGINObjClassInit(tcps_sess, 1, OBJ_IS_CORE_MODULE) /* class, version - CHANGE class also in END MACRO! */
RUNLOG_STR("initializing tcps_sess class");
	/* request objects we use */
	CHKiRet(objUse(errmsg, CORE_COMPONENT));

	/* set our own handlers */
	OBJSetMethodHandler(objMethod_DEBUGPRINT, tcps_sessDebugPrint);
	OBJSetMethodHandler(objMethod_CONSTRUCTION_FINALIZER, tcps_sessConstructFinalize);
ENDObjClassInit(tcps_sess)



/* vim:set ai:
 */