Add a OF_IMSCAND flag at set it when we create the object, and replace

the duplicated test for :status, Last-Modified and ETag.

bin/varnishd/cache/cache_fetch.c

@@ -397,6 +397,7 @@ vbf_stp_startfetch(struct worker *wrk, struct busyobj *bo)
 static enum fetch_step
 vbf_stp_fetch(struct worker *wrk, struct busyobj *bo)
 {
+	char *p;
 
 	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
 	CHECK_OBJ_NOTNULL(bo, BUSYOBJ_MAGIC);
@@ -483,6 +484,11 @@ vbf_stp_fetch(struct worker *wrk, struct busyobj *bo)
 	if (bo->do_gzip || bo->do_gunzip)
 		ObjSetFlag(bo->vfc, OF_CHGGZIP, 1);
 
+	if (http_IsStatus(bo->beresp, 200) && (
+	    http_GetHdr(bo->beresp, H_Last_Modified, &p) ||
+	    http_GetHdr(bo->beresp, H_ETag, &p)))
+		ObjSetFlag(bo->vfc, OF_IMSCAND, 1);
+
 	if (bo->htc.body_status != BS_NONE)
 		V1F_Setup_Fetch(bo);
 
@@ -865,8 +871,7 @@ VBF_Fetch(struct worker *wrk, struct req *req, struct objcore *oc,
 		oldobj = ObjGetObj(oldoc, &wrk->stats);
 		CHECK_OBJ_NOTNULL(oldobj, OBJECT_MAGIC);
 
-		if (http_GetHdr(oldobj->http, H_Last_Modified, NULL) ||
-		   http_GetHdr(oldobj->http, H_ETag, NULL)) {
+		if (ObjCheckFlag(oldoc, &req->wrk->stats, OF_IMSCAND)) {
 			assert(oldoc->refcnt > 0);
 			HSH_Ref(oldoc);
 			bo->ims_obj = oldobj;

include/tbl/obj_attr.h

@@ -45,6 +45,7 @@ OBJ_ATTR(LASTMODIFIED,	lastmodified)
 /* upper, lower, val */
 OBJ_FLAG(GZIPED,	gziped,		(1<<1))
 OBJ_FLAG(CHGGZIP,	chggzip,	(1<<2))
+OBJ_FLAG(IMSCAND,	imscand,	(1<<3))
 #endif
 
 /*lint -restore */