From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7B97C4321A for ; Tue, 11 Jun 2019 18:00:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CE3D2086D for ; Tue, 11 Jun 2019 18:00:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406748AbfFKSAg convert rfc822-to-8bit (ORCPT ); Tue, 11 Jun 2019 14:00:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39688 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406628AbfFKSAg (ORCPT ); Tue, 11 Jun 2019 14:00:36 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 94E903082E68; Tue, 11 Jun 2019 18:00:30 +0000 (UTC) Received: from carbon (ovpn-200-32.brq.redhat.com [10.40.200.32]) by smtp.corp.redhat.com (Postfix) with ESMTP id EA5131001B0F; Tue, 11 Jun 2019 18:00:22 +0000 (UTC) Date: Tue, 11 Jun 2019 20:00:21 +0200 From: Jesper Dangaard Brouer To: Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= Cc: netdev@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , David Miller , Jonathan Lemon , brouer@redhat.com Subject: Re: [PATCH bpf-next v3 2/3] bpf_xdp_redirect_map: Perform map lookup in eBPF helper Message-ID: <20190611200021.473138bc@carbon> In-Reply-To: <156026784011.26748.7290735899755011809.stgit@alrua-x1> References: <156026783994.26748.2899804283816365487.stgit@alrua-x1> <156026784011.26748.7290735899755011809.stgit@alrua-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Tue, 11 Jun 2019 18:00:35 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 11 Jun 2019 17:44:00 +0200 Toke Høiland-Jørgensen wrote: > From: Toke Høiland-Jørgensen > > The bpf_redirect_map() helper used by XDP programs doesn't return any > indication of whether it can successfully redirect to the map index it was > given. Instead, BPF programs have to track this themselves, leading to > programs using duplicate maps to track which entries are populated in the > devmap. > > This patch fixes this by moving the map lookup into the bpf_redirect_map() > helper, which makes it possible to return failure to the eBPF program. The > lower bits of the flags argument is used as the return code, which means > that existing users who pass a '0' flag argument will get XDP_ABORTED. > > With this, a BPF program can check the return code from the helper call and > react by, for instance, substituting a different redirect. This works for > any type of map used for redirect. > > Signed-off-by: Toke Høiland-Jørgensen > --- > include/linux/filter.h | 1 + > include/uapi/linux/bpf.h | 8 ++++++++ > net/core/filter.c | 26 ++++++++++++-------------- > 3 files changed, 21 insertions(+), 14 deletions(-) > > diff --git a/include/linux/filter.h b/include/linux/filter.h > index 43b45d6db36d..f31ae8b9035a 100644 > --- a/include/linux/filter.h > +++ b/include/linux/filter.h > @@ -580,6 +580,7 @@ struct bpf_skb_data_end { > struct bpf_redirect_info { > u32 ifindex; > u32 flags; > + void *item; > struct bpf_map *map; > struct bpf_map *map_to_flush; > u32 kern_flags; > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 7c6aef253173..9931cf02de19 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -3098,6 +3098,14 @@ enum xdp_action { > XDP_REDIRECT, > }; > > +/* Flags for bpf_xdp_redirect_map helper */ > + > +/* The lower flag bits will be the return code of bpf_xdp_redirect_map() helper > + * if the map lookup fails. > + */ > +#define XDP_REDIRECT_INVALID_MASK (XDP_ABORTED | XDP_DROP | XDP_PASS | XDP_TX) > +#define XDP_REDIRECT_ALL_FLAGS XDP_REDIRECT_INVALID_MASK > + Slightly confused about the naming of the define, see later. > /* user accessible metadata for XDP packet hook > * new fields must be added to the end of this structure > */ > diff --git a/net/core/filter.c b/net/core/filter.c > index 7a996887c500..dd43be497480 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -3608,17 +3608,13 @@ static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp, > struct bpf_redirect_info *ri) > { > u32 index = ri->ifindex; > - void *fwd = NULL; > + void *fwd = ri->item; > int err; > > ri->ifindex = 0; > + ri->item = NULL; > WRITE_ONCE(ri->map, NULL); > > - fwd = __xdp_map_lookup_elem(map, index); > - if (unlikely(!fwd)) { > - err = -EINVAL; > - goto err; > - } > if (ri->map_to_flush && unlikely(ri->map_to_flush != map)) > xdp_do_flush_map(); > > @@ -3655,18 +3651,13 @@ static int xdp_do_generic_redirect_map(struct net_device *dev, > { > struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); > u32 index = ri->ifindex; > - void *fwd = NULL; > + void *fwd = ri->item; > int err = 0; > > ri->ifindex = 0; > + ri->item = NULL; > WRITE_ONCE(ri->map, NULL); > > - fwd = __xdp_map_lookup_elem(map, index); > - if (unlikely(!fwd)) { > - err = -EINVAL; > - goto err; > - } > - > if (map->map_type == BPF_MAP_TYPE_DEVMAP) { > struct bpf_dtab_netdev *dst = fwd; > > @@ -3735,6 +3726,7 @@ BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, flags) > > ri->ifindex = ifindex; > ri->flags = flags; > + ri->item = NULL; > WRITE_ONCE(ri->map, NULL); > > return XDP_REDIRECT; > @@ -3753,9 +3745,15 @@ BPF_CALL_3(bpf_xdp_redirect_map, struct bpf_map *, map, u32, ifindex, > { > struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); > > - if (unlikely(flags)) > + if (unlikely(flags & ~XDP_REDIRECT_ALL_FLAGS)) > return XDP_ABORTED; > > + ri->item = __xdp_map_lookup_elem(map, ifindex); > + if (unlikely(!ri->item)) { > + WRITE_ONCE(ri->map, NULL); > + return (flags & XDP_REDIRECT_INVALID_MASK); Maybe I'm reading it wrong, but shouldn't the mask be called the "valid" mask? > + } > + > ri->ifindex = ifindex; > ri->flags = flags; > WRITE_ONCE(ri->map, map); > -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer