/* mmsnmptrapd.c
 * This is a message modification module. It takes messages generated
 * from snmptrapd and modifies them so that the look like they
 * originated from the real originator.
 *
 * NOTE: read comments in module-template.h for details on the calling interface!
 *
 * File begun on 2011-05-05 by RGerhards
 *
 * Copyright 2011 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 "rsyslog.h"
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <signal.h>
#include <errno.h>
#include <unistd.h>
#include <libestr.h>
#include <libee/libee.h>
#include <liblognorm.h>
#include "conf.h"
#include "msg.h"
#include "syslogd-types.h"
#include "template.h"
#include "module-template.h"
#include "errmsg.h"
#include "cfsysline.h"
#include "unicode-helper.h"
#include "dirty.h"

MODULE_TYPE_OUTPUT
MODULE_TYPE_NOKEEP

static rsRetVal resetConfigVariables(uchar __attribute__((unused)) *pp, void __attribute__((unused)) *pVal);

/* static data */
DEFobjCurrIf(errmsg);

/* internal structures
 */
DEF_OMOD_STATIC_DATA

typedef struct _instanceData {
	uchar *pszTagName;
	uchar *pszTagID;	/* chaced: name plus trailig shlash (for compares) */
	int lenTagID;		/* cached length of tag ID, for performance reasons */
} instanceData;

typedef struct configSettings_s {
	uchar *pszTagName;	/**< name of tag start value that indicates snmptrapd initiated message */
} configSettings_t;
configSettings_t cs;

//TODO: enable for v6
#if 0
SCOPING_SUPPORT; /* must be set AFTER configSettings_t is defined */

BEGINinitConfVars		/* (re)set config variables to default values */
CODESTARTinitConfVars 
	cs.pszTagName = NULL;
	resetConfigVariables(NULL, NULL);
ENDinitConfVars
#endif


BEGINcreateInstance
CODESTARTcreateInstance
ENDcreateInstance


BEGINisCompatibleWithFeature
CODESTARTisCompatibleWithFeature
ENDisCompatibleWithFeature


BEGINfreeInstance
CODESTARTfreeInstance
	free(pData->pszTagName);
	free(pData->pszTagID);
ENDfreeInstance


BEGINdbgPrintInstInfo
CODESTARTdbgPrintInstInfo
	dbgprintf("mmsnmptrapd\n");
ENDdbgPrintInstInfo


BEGINtryResume
CODESTARTtryResume
ENDtryResume

/* get string up to the next SP or '/'. Stops at max size.
 * dst, lenDst (receive buffer) must be given. lenDst is
 * max length on entry and actual length on exit.
 */
static int
getTagComponent(uchar *tag, uchar *dst, int *lenDst)
{
	int end = *lenDst - 1; /* -1 for NUL-char! */
	int i;

	i = 0;
dbgprintf("XXXX: getTagComponent tag on input: '%s'(%p)\n", tag, tag);
	if(tag[i] != '/')
		goto done;
	++tag;
	while(i < end && tag[i] != '\0' && tag[i] != ' ' && tag[i] != '/') {
		dst[i] = tag[i];
		++i;
	}
	dst[i] = '\0';
dbgprintf("XXXX: getTagComponent dst on output: '%s', len %d\n", dst, i);
	*lenDst = i;
done:
	return i;
}


BEGINdoAction
	int lenTAG;
	int lenSever;
	int lenHost;
	msg_t *pMsg;
	uchar *pszTag;
	uchar pszSever[512];
	uchar pszHost[512];
CODESTARTdoAction
	pMsg = (msg_t*) ppString[0];
	dbgprintf("XXXX: mmsnmptrapd called with pMsg %p\n", pMsg);
	getTAG(pMsg, &pszTag, &lenTAG);
	if(strncmp((char*)pszTag, (char*)pData->pszTagID, pData->lenTagID)) {
		DBGPRINTF("tag '%s' not matching, mmsnmptrapd ignoring this message\n",
			  pszTag);
		FINALIZE;
	}

	lenSever = sizeof(pszSever);
dbgprintf("XXXX: pszTag: '%s', lenID %d\n", pszTag, pData->lenTagID);
	getTagComponent(pszTag+pData->lenTagID-1, pszSever, &lenSever);
	lenHost = sizeof(pszHost);
	getTagComponent(pszTag+pData->lenTagID+lenSever, pszHost, &lenHost);
	dbgprintf("XXXX: mmsnmptrapd sever '%s'(%d), host '%s'(%d)\n", pszSever, lenSever, pszHost,lenHost);

	if(pszHost[lenHost-1] == ':') {
		pszHost[lenHost-1] = '\0';
		--lenHost;
	}
	/* now apply new settings */
	MsgSetTAG(pMsg, pData->pszTagName, pData->lenTagID);
	MsgSetHOSTNAME(pMsg, pszHost, lenHost);
finalize_it:
ENDdoAction


BEGINparseSelectorAct
CODESTARTparseSelectorAct
CODE_STD_STRING_REQUESTparseSelectorAct(1)
	/* first check if this config line is actually for us */
	if(strncmp((char*) p, ":mmsnmptrapd:", sizeof(":mmsnmptrapd:") - 1)) {
		ABORT_FINALIZE(RS_RET_CONFLINE_UNPROCESSED);
	}

	/* ok, if we reach this point, we have something for us */
	p += sizeof(":mmsnmptrapd:") - 1; /* eat indicator sequence  (-1 because of '\0'!) */
	CHKiRet(createInstance(&pData));

	/* check if a non-standard template is to be applied */
	if(*(p-1) == ';')
		--p;
	/* we call the function below because we need to call it via our interface definition. However,
	 * the format specified (if any) is always ignored.
	 */
	CHKiRet(cflineParseTemplateName(&p, *ppOMSR, 0, OMSR_TPL_AS_MSG, (uchar*) "RSYSLOG_FileFormat"));

	/* finally build the instance */
	if(cs.pszTagName == NULL) {
		pData->pszTagName = (uchar*) strdup("snmptrapd:");
		pData->pszTagID = (uchar*) strdup("snmptrapd/");
	} else {
		int lenTag = ustrlen(cs.pszTagName);
		/* new tag value (with colon at the end) */
		CHKmalloc(pData->pszTagName = MALLOC(lenTag + 2));
		memcpy(pData->pszTagName, cs.pszTagName, lenTag);
		memcpy(pData->pszTagName+lenTag, ":", 2);
		/* tag ID for comparisions */
		CHKmalloc(pData->pszTagID = MALLOC(lenTag + 2));
		memcpy(pData->pszTagID, cs.pszTagName, lenTag);
		memcpy(pData->pszTagID+lenTag, "/", 2);
		free(cs.pszTagName); /* no longer needed */
	}
	pData->lenTagID = ustrlen(pData->pszTagID);

	/* all config vars auto-reset! */
	cs.pszTagName = NULL;
CODE_STD_FINALIZERparseSelectorAct
ENDparseSelectorAct


BEGINmodExit
CODESTARTmodExit
	objRelease(errmsg, CORE_COMPONENT);
ENDmodExit


BEGINqueryEtryPt
CODESTARTqueryEtryPt
CODEqueryEtryPt_STD_OMOD_QUERIES
ENDqueryEtryPt



/* Reset config variables for this module to default values.
 */
static rsRetVal resetConfigVariables(uchar __attribute__((unused)) *pp, void __attribute__((unused)) *pVal)
{
	DEFiRet;
	free(cs.pszTagName);
	cs.pszTagName = NULL;
	RETiRet;
}


BEGINmodInit()
	rsRetVal localRet;
	rsRetVal (*pomsrGetSupportedTplOpts)(unsigned long *pOpts);
	unsigned long opts;
	int bMsgPassingSupported;
CODESTARTmodInit
//TODO v6: add SCOPINGmodInit
	*ipIFVersProvided = CURR_MOD_IF_VERSION;
		/* we only support the current interface specification */
CODEmodInit_QueryRegCFSLineHdlr
	/* check if the rsyslog core supports parameter passing code */
	bMsgPassingSupported = 0;
	localRet = pHostQueryEtryPt((uchar*)"OMSRgetSupportedTplOpts",
			&pomsrGetSupportedTplOpts);
	if(localRet == RS_RET_OK) {
		/* found entry point, so let's see if core supports msg passing */
		CHKiRet((*pomsrGetSupportedTplOpts)(&opts));
		if(opts & OMSR_TPL_AS_MSG)
			bMsgPassingSupported = 1;
	} else if(localRet != RS_RET_ENTRY_POINT_NOT_FOUND) {
		ABORT_FINALIZE(localRet); /* Something else went wrong, not acceptable */
	}
	
	if(!bMsgPassingSupported) {
		DBGPRINTF("mmsnmptrapd: msg-passing is not supported by rsyslog core, "
			  "can not continue.\n");
		ABORT_FINALIZE(RS_RET_NO_MSG_PASSING);
	}

	CHKiRet(objUse(errmsg, CORE_COMPONENT));
	
	CHKiRet(omsdRegCFSLineHdlr((uchar *)"mmsnmptrapdtag", 0, eCmdHdlrInt,
				    NULL, &cs.pszTagName, STD_LOADABLE_MODULE_ID));
	CHKiRet(omsdRegCFSLineHdlr((uchar *)"resetconfigvariables", 1, eCmdHdlrCustomHandler,
				    resetConfigVariables, NULL, STD_LOADABLE_MODULE_ID));
ENDmodInit

/* vi:set ai:
 */