add 'exists()' script function to check if variable exists

grammar/grammar.y

@@ -8,7 +8,7 @@
  * PRI filter) are very hard to beat in ease of use, at least for simpler
  * cases.
  *
- * Copyright 2011-2016 Rainer Gerhards and Adiscon GmbH.
+ * Copyright 2011-2020 Rainer Gerhards and Adiscon GmbH.
  *
  * This file is part of the rsyslog runtime library.
  *
@@ -55,6 +55,7 @@ extern int yyerror(const char*);
 	struct cnfexpr *expr;
 	struct cnfarray *arr;
 	struct cnffunc *func;
+	struct cnffuncexists *exists;
 	struct cnffparamlst *fparams;
 	struct cnfitr *itr;
 }
@@ -74,6 +75,7 @@ extern int yyerror(const char*);
 %token RESET
 %token UNSET
 %token CONTINUE
+%token EXISTS
 %token <cnfstmt> CALL
 %token <cnfstmt> CALL_INDIRECT
 %token <s> LEGACY_ACTION
@@ -217,6 +219,7 @@ expr:	  expr AND expr			{ $$ = cnfexprNew(AND, $1, $3); }
 	| expr '%' expr			{ $$ = cnfexprNew('%', $1, $3); }
 	| '(' expr ')'			{ $$ = $2; }
 	| '-' expr %prec UMINUS		{ $$ = cnfexprNew('M', NULL, $2); }
+	| EXISTS '(' VAR ')'		{ $$ = (struct cnfexpr*) cnffuncexistsNew($3); }
 	| FUNC '(' ')'			{ $$ = (struct cnfexpr*) cnffuncNew($1, NULL); }
 	| FUNC '(' fparams ')'		{ $$ = (struct cnfexpr*) cnffuncNew($1, $3); }
 	| NUMBER			{ $$ = (struct cnfexpr*) cnfnumvalNew($1); }

grammar/lexer.l

@@ -314,6 +314,7 @@ int fileno(FILE *stream);
 					        "escaped, problem string is: %s",
 						yytext); }
 <EXPR>[ \t\n]			{ cnfPrintToken(yytext); }
+<EXPR>"exists"			{ cnfPrintToken(yytext); return EXISTS; } /* special case function (see rainerscript.c) */
 <EXPR>[a-z][a-z0-9_]*		{ cnfPrintToken(yytext); yylval.estr = es_newStrFromCStr(yytext, yyleng);
 				  return FUNC; }
 <EXPR>.				{ cnfPrintToken(yytext); parser_errmsg("invalid character '%s' in expression "

grammar/rainerscript.c

@@ -142,6 +142,7 @@ tokenToString(const int token)
 	case 'V': tokstr ="V"; break;
 	case 'F': tokstr ="F"; break;
 	case 'A': tokstr ="A"; break;
+	case S_FUNC_EXISTS: tokstr ="exists()"; break;
 	default: snprintf(tokbuf, sizeof(tokbuf), "%c[%d]", token, token);
 		 tokstr = tokbuf; break;
 	}
@@ -2750,6 +2751,27 @@ doFuncCall(struct cnffunc *__restrict__ const func, struct svar *__restrict__ co
 	}
 }
 
+
+/* Perform the special "exists()" function to check presence of a variable.
+ */
+static int ATTR_NONNULL()
+evalFuncExists(struct cnffuncexists *__restrict__ const fexists, void *__restrict__ const usrptr)
+{
+	int r = 0;
+	rsRetVal localRet;
+
+	if(fexists->prop.id == PROP_CEE        ||
+	   fexists->prop.id == PROP_LOCAL_VAR  ||
+	   fexists->prop.id == PROP_GLOBAL_VAR   ) {
+		localRet = msgCheckVarExists((smsg_t*)usrptr, &fexists->prop);
+		if(localRet == RS_RET_OK) {
+			r = 1;
+		}
+	}
+
+	return r;
+}
+
 static void
 evalVar(struct cnfvar *__restrict__ const var, void *__restrict__ const usrptr,
 	struct svar *__restrict__ const ret)
@@ -3352,6 +3374,10 @@ cnfexprEval(const struct cnfexpr *__restrict__ const expr,
 	case 'F':
 		doFuncCall((struct cnffunc*) expr, ret, usrptr, pWti);
 		break;
+	case S_FUNC_EXISTS:
+		ret->datatype = 'N';
+		ret->d.n = evalFuncExists((struct cnffuncexists*) expr, usrptr);
+		break;
 	default:
 		ret->datatype = 'N';
 		ret->d.n = 0ll;
@@ -3887,6 +3913,10 @@ cnfexprPrint(struct cnfexpr *expr, int indent)
 		dbgprintf("NOT\n");
 		cnfexprPrint(expr->r, indent+1);
 		break;
+	case S_FUNC_EXISTS:
+		doIndent(indent);
+		dbgprintf("exists(%s)\n", ((struct cnffuncexists*)expr)->varname);
+		break;
 	case 'S':
 		doIndent(indent);
 		cstrPrint("string '", ((struct cnfstringval*)expr)->estr);
@@ -5197,6 +5227,23 @@ cnffuncNew_prifilt(int fac)
 }
 
 
+/* The check-if-variable exists "exists($!var)" is a special beast and as such
+ * also needs special code (we must not evaluate the var but need its name).
+ */
+struct cnffuncexists * ATTR_NONNULL()
+cnffuncexistsNew(const char *const varname)
+{
+	struct cnffuncexists* f_exists;
+
+	if((f_exists = malloc(sizeof(struct cnffuncexists))) != NULL) {
+		f_exists->nodetype = S_FUNC_EXISTS;
+		f_exists->varname = varname;
+		msgPropDescrFill(&f_exists->prop, (uchar*)varname, strlen(varname));
+	}
+	return f_exists;
+}
+
+
 /* returns 0 if everything is OK and config parsing shall continue,
  * and 1 if things are so wrong that config parsing shall be aborted.
  */

grammar/rainerscript.h

@@ -97,13 +97,13 @@ struct nvlst {
  * be the sole foundation for the AST.
  *
  * nodetypes (list not yet complete)
+ * A - (string) array
  * F - function
  * N - number
  * P - fparamlst
  * R - rule
  * S - string
  * V - var
- * A - (string) array
  * ... plus the S_* #define's below:
  */
 #define S_STOP 4000
@@ -118,6 +118,7 @@ struct nvlst {
 #define S_FOREACH 4009
 #define S_RELOAD_LOOKUP_TABLE 4010
 #define S_CALL_INDIRECT 4011
+#define S_FUNC_EXISTS 4012 /* special case function which must get varname only */
 
 enum cnfFiltType { CNFFILT_NONE, CNFFILT_PRI, CNFFILT_PROP, CNFFILT_SCRIPT };
 const char* cnfFiltType2str(const enum cnfFiltType filttype);
@@ -262,6 +263,12 @@ struct cnffunc {
 } __attribute__((aligned (8)));
 
 
+struct cnffuncexists {
+	unsigned nodetype;
+	const char *varname;
+	msgPropDescr_t prop;
+} __attribute__((aligned (8)));
+
 struct scriptFunct {
 	const char *fname;
 	unsigned short minParams;
@@ -354,6 +361,7 @@ struct cnfnumval* cnfnumvalNew(long long val);
 struct cnfstringval* cnfstringvalNew(es_str_t *estr);
 struct cnfvar* cnfvarNew(char *name);
 struct cnffunc * cnffuncNew(es_str_t *fname, struct cnffparamlst* paramlst);
+struct cnffuncexists * cnffuncexistsNew(const char *varname);
 struct cnffparamlst * cnffparamlstNew(struct cnfexpr *expr, struct cnffparamlst *next);
 int cnfDoInclude(const char *name, const int optional);
 int cnfparamGetIdx(struct cnfparamblk *params, const char *name);

runtime/msg.c

@@ -567,7 +567,7 @@ getRcvFromIP(smsg_t * const pM)
 
 /* map a property name (string) to a property ID */
 rsRetVal
-propNameToID(uchar *pName, propid_t *pPropID)
+propNameToID(const uchar *const pName, propid_t *const pPropID)
 {
 	DEFiRet;
 
@@ -4838,7 +4838,8 @@ jsonPathFindNext(struct json_object *root, uchar *namestart, uchar **name, uchar
 }
 
 static rsRetVal
-jsonPathFindParent(struct json_object *jroot, uchar *name, uchar *leaf, struct json_object **parent, int bCreate)
+jsonPathFindParent(struct json_object *jroot, uchar *name, uchar *leaf, struct json_object **parent,
+	const int bCreate)
 {
 	uchar *namestart;
 	DEFiRet;
@@ -4876,28 +4877,53 @@ jsonMerge(struct json_object *existing, struct json_object *json)
 
 /* find a JSON structure element (field or container doesn't matter).  */
 rsRetVal
-jsonFind(struct json_object *jroot, msgPropDescr_t *pProp, struct json_object **jsonres)
+jsonFind(smsg_t *const pMsg, msgPropDescr_t *pProp, struct json_object **jsonres)
 {
 	uchar *leaf;
 	struct json_object *parent;
 	struct json_object *field;
+	struct json_object **jroot = NULL;
+	pthread_mutex_t *mut = NULL;
 	DEFiRet;
 
-	if(jroot == NULL) {
+	CHKiRet(getJSONRootAndMutex(pMsg, pProp->id, &jroot, &mut));
+	pthread_mutex_lock(mut);
+
+	if(*jroot == NULL) {
 		field = NULL;
 		goto finalize_it;
 	}
 
 	if(!strcmp((char*)pProp->name, "!")) {
-		field = jroot;
+		field = *jroot;
+	} else if(!strcmp((char*)pProp->name, ".")) {
+		field = *jroot;
 	} else {
 		leaf = jsonPathGetLeaf(pProp->name, pProp->nameLen);
-		CHKiRet(jsonPathFindParent(jroot, pProp->name, leaf, &parent, 0));
+		CHKiRet(jsonPathFindParent(*jroot, pProp->name, leaf, &parent, 0));
 		if(jsonVarExtract(parent, (char*)leaf, &field) == FALSE)
 			field = NULL;
 	}
 	*jsonres = field;
 
+finalize_it:
+	if(mut != NULL)
+		pthread_mutex_unlock(mut);
+	RETiRet;
+}
+
+/* check if JSON variable exists (works on terminal var and container) */
+rsRetVal ATTR_NONNULL()
+msgCheckVarExists(smsg_t *const pMsg, msgPropDescr_t *pProp)
+{
+	struct json_object *jsonres = NULL;
+	DEFiRet;
+
+	CHKiRet(jsonFind(pMsg, pProp, &jsonres));
+	if(jsonres == NULL) {
+		iRet = RS_RET_NOT_FOUND;
+	}
+
 finalize_it:
 	RETiRet;
 }

runtime/msg.h

@@ -229,16 +229,17 @@ void getInputName(const smsg_t * const pM, uchar **ppsz, int *const plen);
 int getHOSTNAMELen(smsg_t *pM);
 uchar *getProgramName(smsg_t *pM, sbool bLockMutex);
 uchar *getRcvFrom(smsg_t *pM);
-rsRetVal propNameToID(uchar *pName, propid_t *pPropID);
+rsRetVal propNameToID(const uchar *pName, propid_t *pPropID);
 uchar *propIDToName(propid_t propID);
+rsRetVal ATTR_NONNULL() msgCheckVarExists(smsg_t *const pMsg, msgPropDescr_t *pProp);
 rsRetVal msgGetJSONPropJSON(smsg_t *pMsg, msgPropDescr_t *pProp, struct json_object **pjson);
 rsRetVal msgGetJSONPropJSONorString(smsg_t * const pMsg, msgPropDescr_t *pProp, struct json_object **pjson,
 uchar **pcstr);
 rsRetVal getJSONPropVal(smsg_t *pMsg, msgPropDescr_t *pProp, uchar **pRes, rs_size_t *buflen,
 unsigned short *pbMustBeFreed);
 rsRetVal msgSetJSONFromVar(smsg_t *pMsg, uchar *varname, struct svar *var, int force_reset);
 rsRetVal msgDelJSON(smsg_t *pMsg, uchar *varname);
-rsRetVal jsonFind(struct json_object *jroot, msgPropDescr_t *pProp, struct json_object **jsonres);
+rsRetVal jsonFind(smsg_t *const pMsg, msgPropDescr_t *pProp, struct json_object **jsonres);
 
 rsRetVal msgPropDescrFill(msgPropDescr_t *pProp, uchar *name, int nameLen);
 void msgPropDescrDestruct(msgPropDescr_t *pProp);

template.c

@@ -285,7 +285,7 @@ tplToJSON(struct template *pTpl, smsg_t *pMsg, struct json_object **pjson, struc
 	DEFiRet;
 
 	if(pTpl->bHaveSubtree){
-		if(jsonFind(pMsg->json, &pTpl->subtree, pjson) != RS_RET_OK)
+		if(jsonFind(pMsg, &pTpl->subtree, pjson) != RS_RET_OK)
 			*pjson = NULL;
 		if(*pjson == NULL) {
 			/* we need to have a root object! */

tests/Makefile.am

@@ -422,6 +422,12 @@ TESTS +=  \
 	rscript_parse_json.sh \
 	rscript_previous_action_suspended.sh \
 	rscript_str2num_negative.sh \
+	rscript_exists-yes.sh \
+	rscript_exists-yes2.sh \
+	rscript_exists-not1.sh \
+	rscript_exists-not2.sh \
+	rscript_exists-not3.sh \
+	rscript_exists-not4.sh \
 	rscript-config_enable-on.sh \
 	config_output-o-option.sh \
 	rs-cnum.sh \
@@ -1715,6 +1721,12 @@ EXTRA_DIST= \
 	rscript_backticks_empty_envvar-vg.sh \
 	rscript_previous_action_suspended.sh \
 	rscript_str2num_negative.sh \
+	rscript_exists-yes.sh \
+	rscript_exists-yes2.sh \
+	rscript_exists-not1.sh \
+	rscript_exists-not2.sh \
+	rscript_exists-not3.sh \
+	rscript_exists-not4.sh \
 	rs-cnum.sh \
 	rs-int2hex.sh \
 	rs-substring.sh \

tests/rscript_exists-not1.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# add 2020-10-02 by Rainer Gerhards, released under ASL 2.0
+. ${srcdir:=.}/diag.sh init
+generate_conf
+add_conf '
+template(name="outfmt" type="string" string="%!result%\n")
+# ensure that in this test there is NO variable define at all
+if $msg contains "msgnum" then {
+	if exists($!p1!p2!val) then
+		set $!result = "on";
+	else
+		set $!result = "off";
+	action(type="omfile" file="'$RSYSLOG_OUT_LOG'" template="outfmt")
+	}
+'
+startup
+injectmsg 0 1
+shutdown_when_empty
+wait_shutdown
+export EXPECTED='off'
+cmp_exact
+exit_test

tests/rscript_exists-not2.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# add 2020-10-02 by Rainer Gerhards, released under ASL 2.0
+. ${srcdir:=.}/diag.sh init
+generate_conf
+add_conf '
+template(name="outfmt" type="string" string="%!result%\n")
+set $!somevar = "test"; # this makes matters a bit more complicated
+if $msg contains "msgnum" then {
+	if exists($!p1!p2!val) then
+		set $!result = "on";
+	else
+		set $!result = "off";
+	action(type="omfile" file="'$RSYSLOG_OUT_LOG'" template="outfmt")
+	}
+'
+startup
+injectmsg 0 1
+shutdown_when_empty
+wait_shutdown
+export EXPECTED='off'
+cmp_exact
+exit_test

tests/rscript_exists-not3.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# add 2020-10-02 by Rainer Gerhards, released under ASL 2.0
+. ${srcdir:=.}/diag.sh init
+generate_conf
+add_conf '
+template(name="outfmt" type="string" string="%!result%\n")
+# ensure that in this test there is NO variable define at all
+if $msg contains "msgnum" then {
+	if exists($.p1!p2!val) then
+		set $!result = "on";
+	else
+		set $!result = "off";
+	action(type="omfile" file="'$RSYSLOG_OUT_LOG'" template="outfmt")
+	}
+'
+startup
+injectmsg 0 1
+shutdown_when_empty
+wait_shutdown
+export EXPECTED='off'
+cmp_exact
+exit_test

tests/rscript_exists-not4.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# add 2020-10-02 by Rainer Gerhards, released under ASL 2.0
+. ${srcdir:=.}/diag.sh init
+generate_conf
+add_conf '
+template(name="outfmt" type="string" string="%!result%\n")
+set $.somevar = "test"; # this makes matters a bit more complicated
+if $msg contains "msgnum" then {
+	if not exists($.p1!p2!val) then
+		set $!result = "off";
+	else
+		set $!result = "on";
+	action(type="omfile" file="'$RSYSLOG_OUT_LOG'" template="outfmt")
+	}
+'
+startup
+injectmsg 0 1
+shutdown_when_empty
+wait_shutdown
+export EXPECTED='off'
+cmp_exact
+exit_test