From 25224fb536488ae63e6addd2c9005bc2b8dc126a Mon Sep 17 00:00:00 2001
From: Rainer Gerhards <rgerhards@adiscon.com>
Date: Wed, 21 Feb 2024 09:31:00 +0100
Subject: [PATCH] omfile: do not carry out actual action when writing to
 /dev/null

In some use cases omfile is configured to write to /dev/null. This seems
primarily be done because of statistics gathering but maybe some other
scenarios. We now add conditional logic to not do any actual omfile
action when the target file is /dev/null.

Note: this check only works on static file names. When /dev/null is
evaluated as part of dynafile, it will be handled just in the regular
case like before this patch.
---
 tools/omfile.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/omfile.c b/tools/omfile.c
index 1702a30399..cf464cd1c1 100644
--- a/tools/omfile.c
+++ b/tools/omfile.c
@@ -17,7 +17,7 @@
  * pipes. These have been moved to ompipe, to reduced the entanglement
  * between the two different functionalities. -- rgerhards
  *
- * Copyright 2007-2023 Adiscon GmbH.
+ * Copyright 2007-2024 Adiscon GmbH.
  *
  * This file is part of rsyslog.
  *
@@ -139,6 +139,7 @@ typedef struct _instanceData {
 	strm_t	*pStrm;		/* our output stream */
 	short nInactive;	/* number of minutes not writen (STATIC files only) */
 	char	bDynamicName;	/* 0 - static name, 1 - dynamic name (with properties) */
+	int	isDevNull;	/* do we "write" to /dev/null? - if so, do nothing */
 	int	fCreateMode;	/* file creation mode for open() */
 	int	fDirCreateMode;	/* creation mode for mkdir() */
 	int	bCreateDirs;	/* auto-create directories? */
@@ -1081,6 +1082,11 @@ BEGINcommitTransaction
 	instanceData *__restrict__ const pData = pWrkrData->pData;
 	unsigned i;
 CODESTARTcommitTransaction
+
+	if(pData->isDevNull) {
+		goto terminate;
+	}
+
 	pthread_mutex_lock(&pData->mutWrite);
 
 	for(i = 0 ; i < nParams ; ++i) {
@@ -1105,6 +1111,8 @@ CODESTARTcommitTransaction
 		iRet = (pData->bDynamicName && runModConf->bDynafileDoNotSuspend) ?
 			RS_RET_OK : RS_RET_SUSPENDED;
 	}
+
+terminate:
 ENDcommitTransaction
 
 
@@ -1135,6 +1143,7 @@ setInstParamDefaults(instanceData *__restrict__ const pData)
 	pData->useCryprov = 0;
 	pData->iCloseTimeout = -1;
 	pData->iSizeLimit = 0;
+	pData->isDevNull = 0;
 	pData->pszSizeLimitCmd = NULL;
 }
 
@@ -1378,6 +1387,10 @@ CODESTARTnewActInst
 		ABORT_FINALIZE(RS_RET_MISSING_CNFPARAMS);
 	}
 
+	if(!strcmp((const char*) pData->fname, "/dev/null")) {
+		pData->isDevNull = 1;
+	}
+
 	if(pData->sigprovName != NULL) {
 		initSigprov(pData, lst);
 	}