From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Lau Subject: Re: [PATCH bpf-next] filter: add BPF_ADJ_ROOM_DATA mode to bpf_skb_adjust_room() Date: Fri, 9 Nov 2018 18:51:32 +0000 Message-ID: <20181109185131.7f7osxg2tfp2xapx@kafai-mbp.dhcp.thefacebook.com> References: <20181108151137.3975-1-nicolas.dichtel@6wind.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: "ast@kernel.org" , "daniel@iogearbox.net" , "davem@davemloft.net" , "netdev@vger.kernel.org" To: Nicolas Dichtel Return-path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:52644 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727961AbeKJEdu (ORCPT ); Fri, 9 Nov 2018 23:33:50 -0500 In-Reply-To: <20181108151137.3975-1-nicolas.dichtel@6wind.com> Content-Language: en-US Content-ID: <59559B372EF2374EBF78D414EF8F1A6F@namprd15.prod.outlook.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Nov 08, 2018 at 04:11:37PM +0100, Nicolas Dichtel wrote: > This new mode enables to add or remove an l2 header in a programmatic way > with cls_bpf. > For example, it enables to play with mpls headers. >=20 > Signed-off-by: Nicolas Dichtel > --- > include/uapi/linux/bpf.h | 3 ++ > net/core/filter.c | 54 ++++++++++++++++++++++++++++++++++ > tools/include/uapi/linux/bpf.h | 3 ++ > 3 files changed, 60 insertions(+) >=20 > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 852dc17ab47a..47407fd5162b 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -1467,6 +1467,8 @@ union bpf_attr { > * > * * **BPF_ADJ_ROOM_NET**: Adjust room at the network layer > * (room space is added or removed below the layer 3 header). > + * * **BPF_ADJ_ROOM_DATA**: Adjust room at the beginning of the > + * packet (room space is added or removed below skb->data). > * > * All values for *flags* are reserved for future usage, and must > * be left at zero. > @@ -2408,6 +2410,7 @@ enum bpf_func_id { > /* Mode for BPF_FUNC_skb_adjust_room helper. */ > enum bpf_adj_room_mode { > BPF_ADJ_ROOM_NET, > + BPF_ADJ_ROOM_DATA, > }; > =20 > /* Mode for BPF_FUNC_skb_load_bytes_relative helper. */ > diff --git a/net/core/filter.c b/net/core/filter.c > index e521c5ebc7d1..e699849b269d 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -2884,6 +2884,58 @@ static int bpf_skb_adjust_net(struct sk_buff *skb,= s32 len_diff) > return ret; > } > =20 > +static int bpf_skb_data_shrink(struct sk_buff *skb, u32 len) > +{ > + unsigned short hhlen =3D skb->dev->header_ops ? > + skb->dev->hard_header_len : 0; > + int ret; > + > + ret =3D skb_unclone(skb, GFP_ATOMIC); > + if (unlikely(ret < 0)) > + return ret; > + > + __skb_pull(skb, len); > + skb_reset_mac_header(skb); > + skb_reset_network_header(skb); > + skb->network_header +=3D hhlen; > + skb_reset_transport_header(skb); hmm...why transport_header does not need +=3D hhlen here while network_header does? > + return 0; > +} > + > +static int bpf_skb_data_grow(struct sk_buff *skb, u32 len) > +{ > + unsigned short hhlen =3D skb->dev->header_ops ? > + skb->dev->hard_header_len : 0; > + int ret; > + > + ret =3D skb_cow(skb, len); > + if (unlikely(ret < 0)) > + return ret; > + > + skb_push(skb, len); > + skb_reset_mac_header(skb); > + return 0; > +} > + > +static int bpf_skb_adjust_data(struct sk_buff *skb, s32 len_diff) > +{ > + u32 len_diff_abs =3D abs(len_diff); > + bool shrink =3D len_diff < 0; > + int ret; > + > + if (unlikely(len_diff_abs > 0xfffU)) > + return -EFAULT; > + > + if (shrink && len_diff_abs >=3D skb_headlen(skb)) > + return -EFAULT; > + > + ret =3D shrink ? bpf_skb_data_shrink(skb, len_diff_abs) : > + bpf_skb_data_grow(skb, len_diff_abs); > + > + bpf_compute_data_pointers(skb); > + return ret; > +} > + > BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, > u32, mode, u64, flags) > { > @@ -2891,6 +2943,8 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, s= kb, s32, len_diff, > return -EINVAL; > if (likely(mode =3D=3D BPF_ADJ_ROOM_NET)) > return bpf_skb_adjust_net(skb, len_diff); > + if (likely(mode =3D=3D BPF_ADJ_ROOM_DATA)) > + return bpf_skb_adjust_data(skb, len_diff); > =20 > return -ENOTSUPP; > } > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bp= f.h > index 852dc17ab47a..47407fd5162b 100644 > --- a/tools/include/uapi/linux/bpf.h > +++ b/tools/include/uapi/linux/bpf.h > @@ -1467,6 +1467,8 @@ union bpf_attr { > * > * * **BPF_ADJ_ROOM_NET**: Adjust room at the network layer > * (room space is added or removed below the layer 3 header). > + * * **BPF_ADJ_ROOM_DATA**: Adjust room at the beginning of the > + * packet (room space is added or removed below skb->data). > * > * All values for *flags* are reserved for future usage, and must > * be left at zero. > @@ -2408,6 +2410,7 @@ enum bpf_func_id { > /* Mode for BPF_FUNC_skb_adjust_room helper. */ > enum bpf_adj_room_mode { > BPF_ADJ_ROOM_NET, > + BPF_ADJ_ROOM_DATA, > }; > =20 > /* Mode for BPF_FUNC_skb_load_bytes_relative helper. */ > --=20 > 2.18.0 >=20