clear up my confusion

the code is correct in varnish-cache, the VDP_bytes(req, VDP_NULL, ...) calls do not return.

This reverts commit ff7d20a2.

src/foreign/from_cache_esi_deliver.c

@@ -105,35 +105,23 @@ vped_pretend_gzip_bytes(struct req *req, enum vdp_action act, void **priv,
 	while (l > 0) {
 		if (l >= 65535) {
 			lx = 65535;
-			if (VDP_bytes(req, VDP_FLUSH, buf1, sizeof buf1))
+			if (VDP_bytes(req, VDP_NULL, buf1, sizeof buf1))
 				return (-1);
 		} else {
 			lx = (uint16_t)l;
 			buf2[0] = 0;
 			vle16enc(buf2 + 1, lx);
 			vle16enc(buf2 + 3, ~lx);
-			if (VDP_bytes(req, VDP_FLUSH, buf2, sizeof buf2))
+			if (VDP_bytes(req, VDP_NULL, buf2, sizeof buf2))
 				return (-1);
 		}
-		if (VDP_bytes(req, VDP_FLUSH, p, lx))
+		if (VDP_bytes(req, VDP_NULL, p, lx))
 			return (-1);
 		l -= lx;
 		p += lx;
 	}
-	/*
-	 * https://github.com/varnishcache/varnish-cache/issues/3028
-	 *
-	 * the original code has VDP_NULL above, and this flush from below, how
-	 * can this possibly work? who guarantees that our stackframe is still
-	 * intact when we get called the next time?
-	 *
-	 * XXX revisit
-	 */
-#ifdef ORIGINAL_CODE
 	/* buf1 & buf2 is local, have to flush */
-	//return (VDP_bytes(req, VDP_FLUSH, NULL, 0));
-#endif
-	return (0);
+	return (VDP_bytes(req, VDP_FLUSH, NULL, 0));
 }
 
 const struct vdp vped_pretend_gz = {