Fix a detail I didn't catch during code review:

When WRW is used to send stuff to the backend 'req->t_resp' is not
an appropriate base for the timeouts.

bin/varnishd/cache/cache.h

@@ -889,7 +889,7 @@ int Pool_Task(struct pool *pp, struct pool_task *task, enum pool_how how);
 int WRW_Error(const struct worker *w);
 void WRW_Chunked(struct worker *w);
 void WRW_EndChunk(struct worker *w);
-void WRW_Reserve(struct worker *w, int *fd);
+void WRW_Reserve(struct worker *w, int *fd, double t0);
 unsigned WRW_Flush(struct worker *w);
 unsigned WRW_FlushRelease(struct worker *w);
 unsigned WRW_Write(struct worker *w, const void *ptr, int len);

bin/varnishd/cache/cache_esi_deliver.c

@@ -113,7 +113,7 @@ ved_include(struct sess *sp, const char *src, const char *host)
 	WS_Reset(sp->req->ws, sp_ws_wm);
 	WS_Reset(w->aws, wrk_ws_wm);	/* XXX ? */
 
-	WRW_Reserve(sp->wrk, &sp->fd);
+	WRW_Reserve(sp->wrk, &sp->fd, sp->req->t_resp);
 	if (sp->req->res_mode & RES_CHUNKED)
 		WRW_Chunked(sp->wrk);
 }

bin/varnishd/cache/cache_fetch.c

@@ -424,7 +424,7 @@ FetchHdr(struct sess *sp, int need_host_hdr, int sendbody)
 		VDI_AddHostHeader(wrk->busyobj->bereq, vc);
 
 	(void)VTCP_blocking(vc->fd);	/* XXX: we should timeout instead */
-	WRW_Reserve(wrk, &vc->fd);
+	WRW_Reserve(wrk, &vc->fd, sp->t_req);	/* XXX t_resp ? */
 	(void)http_Write(wrk, hp, 0);	/* XXX: stats ? */
 
 	/* Deal with any message-body the request might have */

bin/varnishd/cache/cache_pipe.c

@@ -78,7 +78,7 @@ PipeSession(struct sess *sp)
 	sp->wrk->busyobj->vbc = vc;		/* For panic dumping */
 	(void)VTCP_blocking(vc->fd);
 
-	WRW_Reserve(w, &vc->fd);
+	WRW_Reserve(w, &vc->fd, sp->t_req);
 	sp->wrk->acct_tmp.hdrbytes +=
 	    http_Write(w, sp->wrk->busyobj->bereq, 0);
 

bin/varnishd/cache/cache_response.c

@@ -237,7 +237,7 @@ RES_WriteObj(struct sess *sp)
 	req = sp->req;
 	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
 
-	WRW_Reserve(sp->wrk, &sp->fd);
+	WRW_Reserve(sp->wrk, &sp->fd, sp->req->t_resp);
 
 	if (req->obj->response == 200 &&
 	    req->http->conds &&

bin/varnishd/cache/cache_wrw.c

@@ -56,6 +56,7 @@ struct wrw {
 	ssize_t			liov;
 	ssize_t			cliov;
 	unsigned		ciov;	/* Chunked header marker */
+	double			t0;
 };
 
 /*--------------------------------------------------------------------
@@ -69,7 +70,7 @@ WRW_Error(const struct worker *wrk)
 }
 
 void
-WRW_Reserve(struct worker *wrk, int *fd)
+WRW_Reserve(struct worker *wrk, int *fd, double t0)
 {
 	struct wrw *wrw;
 	unsigned u;
@@ -93,6 +94,7 @@ WRW_Reserve(struct worker *wrk, int *fd)
 	wrw->liov = 0;
 	wrw->niov = 0;
 	wrw->wfd = fd;
+	wrw->t0 = t0;
 	wrk->wrw = wrw;
 }
 
@@ -176,8 +178,7 @@ WRW_Flush(struct worker *wrk)
 			 * counter to prevent slowlaris attacks
 			*/
 
-			if (VTIM_real() - wrk->sp->req->t_resp >
-			    cache_param->send_timeout) {
+			if (VTIM_real() - wrw->t0 > cache_param->send_timeout) {
 				WSL(wrk->vsl, SLT_Debug, *wrw->wfd,
 				    "Hit total send timeout, "
 				    "wrote = %zd/%zd; not retrying",