Fetch thread reference count and keep cached request bodies

With this patch fetch threads will for completely cached request bodies
keep a reference to it for the entire duration of the fetch. This extends
the retry window of backend requests with request body beyond the
BOS_REQ_DONE point.

Patch by: Poul-Henning Kamp

bin/varnishd/cache/cache.h

@@ -401,6 +401,7 @@ struct busyobj {
 	struct http		*bereq0;
 	struct http		*bereq;
 	struct http		*beresp;
+	struct objcore		*bereq_body;
 	struct objcore		*stale_oc;
 	struct objcore		*fetch_objcore;
 

bin/varnishd/cache/cache_fetch.c

@@ -241,6 +241,12 @@ vbf_stp_mkbereq(struct worker *wrk, struct busyobj *bo)
 	if (bo->req->req_body_status == REQ_BODY_NONE) {
 		bo->req = NULL;
 		ObjSetState(bo->wrk, bo->fetch_objcore, BOS_REQ_DONE);
+	} else if (bo->req->req_body_status == REQ_BODY_CACHED) {
+		AN(bo->req->body_oc);
+		bo->bereq_body = bo->req->body_oc;
+		HSH_Ref(bo->bereq_body);
+		bo->req = NULL;
+		ObjSetState(bo->wrk, bo->fetch_objcore, BOS_REQ_DONE);
 	}
 	return (F_STP_STARTFETCH);
 }
@@ -969,6 +975,8 @@ vbf_fetch_thread(struct worker *wrk, void *priv)
 	VCL_TaskLeave(bo->privs);
 	http_Teardown(bo->bereq);
 	http_Teardown(bo->beresp);
+	if (bo->bereq_body != NULL)
+		HSH_DerefObjCore(bo->wrk, &bo->bereq_body, 0);
 
 	if (bo->fetch_objcore->boc->state == BOS_FINISHED) {
 		AZ(bo->fetch_objcore->flags & OC_F_FAILED);

bin/varnishd/http1/cache_http1_fetch.c

@@ -104,7 +104,14 @@ V1F_SendReq(struct worker *wrk, struct busyobj *bo, uint64_t *ctr_hdrbytes,
 	/* Deal with any message-body the request might (still) have */
 	i = 0;
 
-	if (bo->req != NULL &&
+	if (bo->bereq_body != NULL) {
+		if (do_chunked)
+			V1L_Chunked(wrk);
+		(void)ObjIterate(bo->wrk, bo->bereq_body,
+		    bo, vbf_iter_req_body, 0);
+		if (do_chunked)
+			V1L_EndChunk(wrk);
+	} else if (bo->req != NULL &&
 	    (bo->req->req_body_status == REQ_BODY_CACHED || !onlycached)) {
 		if (do_chunked)
 			V1L_Chunked(wrk);