From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [RFC PATCH 08/12] bpf: add devmap, a map for storing net device references Date: Sat, 8 Jul 2017 20:57:50 +0200 Message-ID: <20170708205750.152ca83e@redhat.com> References: <20170707172115.9984.53461.stgit@john-Precision-Tower-5810> <20170707173712.9984.13243.stgit@john-Precision-Tower-5810> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, davem@davemloft.net, andy@greyhouse.net, daniel@iogearbox.net, ast@fb.com, brouer@redhat.com To: John Fastabend Return-path: Received: from mx1.redhat.com ([209.132.183.28]:44562 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753079AbdGHS56 (ORCPT ); Sat, 8 Jul 2017 14:57:58 -0400 In-Reply-To: <20170707173712.9984.13243.stgit@john-Precision-Tower-5810> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 07 Jul 2017 10:37:12 -0700 John Fastabend wrote: > Device map (devmap) is a BPF map, primarily useful for networking > applications, that uses a key to lookup a reference to a netdevice. > > The map provides a clean way for BPF programs to build virtual port > to physical port maps. Additionally, it provides a scoping function > for the redirect action itself allowing multiple optimizations. Future > patches will leverage the map to provide batching at the XDP layer. > > Another optimization/feature, that is not yet implemented, would be > to support multiple netdevices per key to support efficient multicast > and broadcast support. [...] > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 74ea96e..06073ba 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -1294,6 +1294,14 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id) > func_id != BPF_FUNC_current_task_under_cgroup) > goto error; > break; > + /* devmap returns a pointer to a live net_device ifindex that we cannot > + * allow to be modified from bpf side. So do not allow lookup elemnts ^^^^^^^ Spelling of elements > + * for now. > + */ > + case BPF_MAP_TYPE_DEVMAP: > + if (func_id == BPF_FUNC_map_lookup_elem) > + goto error; > + break; Reviewer notice this limitation from the bpf_prog side. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer