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Date: Tue, 4 Jul 2023 11:24:55 +0200
From: Larysa Zaremba <larysa.zaremba@...el.com>
To: John Fastabend <john.fastabend@...il.com>
CC: <bpf@...r.kernel.org>, <ast@...nel.org>, <daniel@...earbox.net>,
<andrii@...nel.org>, <martin.lau@...ux.dev>, <song@...nel.org>, <yhs@...com>,
<kpsingh@...nel.org>, <sdf@...gle.com>, <haoluo@...gle.com>,
<jolsa@...nel.org>, David Ahern <dsahern@...il.com>, Jakub Kicinski
<kuba@...nel.org>, Willem de Bruijn <willemb@...gle.com>, "Jesper Dangaard
Brouer" <brouer@...hat.com>, Anatoly Burakov <anatoly.burakov@...el.com>,
Alexander Lobakin <alexandr.lobakin@...el.com>, Magnus Karlsson
<magnus.karlsson@...il.com>, Maryam Tahhan <mtahhan@...hat.com>,
<xdp-hints@...-project.net>, <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 12/20] xdp: Add checksum level hint
On Mon, Jul 03, 2023 at 01:38:27PM -0700, John Fastabend wrote:
> Larysa Zaremba wrote:
> > Implement functionality that enables drivers to expose to XDP code,
> > whether checksums was checked and on what level.
> >
> > Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
> > ---
> > Documentation/networking/xdp-rx-metadata.rst | 3 +++
> > include/linux/netdevice.h | 1 +
> > include/net/xdp.h | 2 ++
> > kernel/bpf/offload.c | 2 ++
> > net/core/xdp.c | 21 ++++++++++++++++++++
> > 5 files changed, 29 insertions(+)
> >
> > diff --git a/Documentation/networking/xdp-rx-metadata.rst b/Documentation/networking/xdp-rx-metadata.rst
> > index ea6dd79a21d3..4ec6ddfd2a52 100644
> > --- a/Documentation/networking/xdp-rx-metadata.rst
> > +++ b/Documentation/networking/xdp-rx-metadata.rst
> > @@ -26,6 +26,9 @@ metadata is supported, this set will grow:
> > .. kernel-doc:: net/core/xdp.c
> > :identifiers: bpf_xdp_metadata_rx_vlan_tag
> >
> > +.. kernel-doc:: net/core/xdp.c
> > + :identifiers: bpf_xdp_metadata_rx_csum_lvl
> > +
> > An XDP program can use these kfuncs to read the metadata into stack
> > variables for its own consumption. Or, to pass the metadata on to other
> > consumers, an XDP program can store it into the metadata area carried
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index 4fa4380e6d89..569563687172 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -1660,6 +1660,7 @@ struct xdp_metadata_ops {
> > enum xdp_rss_hash_type *rss_type);
> > int (*xmo_rx_vlan_tag)(const struct xdp_md *ctx, u16 *vlan_tag,
> > __be16 *vlan_proto);
> > + int (*xmo_rx_csum_lvl)(const struct xdp_md *ctx, u8 *csum_level);
> > };
> >
> > /**
> > diff --git a/include/net/xdp.h b/include/net/xdp.h
> > index 89c58f56ffc6..61ed38fa79d1 100644
> > --- a/include/net/xdp.h
> > +++ b/include/net/xdp.h
> > @@ -391,6 +391,8 @@ void xdp_attachment_setup(struct xdp_attachment_info *info,
> > bpf_xdp_metadata_rx_hash) \
> > XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_VLAN_TAG, \
> > bpf_xdp_metadata_rx_vlan_tag) \
> > + XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_CSUM_LVL, \
> > + bpf_xdp_metadata_rx_csum_lvl) \
> >
> > enum {
> > #define XDP_METADATA_KFUNC(name, _) name,
> > diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
> > index 986e7becfd42..a133fb775f49 100644
> > --- a/kernel/bpf/offload.c
> > +++ b/kernel/bpf/offload.c
> > @@ -850,6 +850,8 @@ void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
> > p = ops->xmo_rx_hash;
> > else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_VLAN_TAG))
> > p = ops->xmo_rx_vlan_tag;
> > + else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_CSUM_LVL))
> > + p = ops->xmo_rx_csum_lvl;
> > out:
> > up_read(&bpf_devs_lock);
> >
> > diff --git a/net/core/xdp.c b/net/core/xdp.c
> > index f6262c90e45f..c666d3e0a26c 100644
> > --- a/net/core/xdp.c
> > +++ b/net/core/xdp.c
> > @@ -758,6 +758,27 @@ __bpf_kfunc int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx, u16 *vlan
> > return -EOPNOTSUPP;
> > }
> >
> > +/**
> > + * bpf_xdp_metadata_rx_csum_lvl - Get depth at which HW has checked the checksum.
> > + * @ctx: XDP context pointer.
> > + * @csum_level: Return value pointer.
> > + *
> > + * In case of success, csum_level contains depth of the last verified checksum.
> > + * If only the outermost checksum was verified, csum_level is 0, if both
> > + * encapsulation and inner transport checksums were verified, csum_level is 1,
> > + * and so on.
> > + * For more details, refer to csum_level field in sk_buff.
> > + *
> > + * Return:
> > + * * Returns 0 on success or ``-errno`` on error.
> > + * * ``-EOPNOTSUPP`` : device driver doesn't implement kfunc
> > + * * ``-ENODATA`` : Checksum was not validated
> > + */
> > +__bpf_kfunc int bpf_xdp_metadata_rx_csum_lvl(const struct xdp_md *ctx, u8 *csum_level)
>
> Istead of ENODATA should we return what would be put in the ip_summed field
> CHECKSUM_{NONE, UNNECESSARY, COMPLETE, PARTIAL}? Then sig would be,
>
> bpf_xdp_metadata_rx_csum_lvl(const struct xdp_md *ctx, u8 *type, u8 *lvl);
>
> or something like that? Or is the thought that its not really necessary?
> I don't have a strong preference but figured it was worth asking.
>
I see no value in returning CHECKSUM_COMPLETE without the actual checksum value.
Same with CHECKSUM_PARTIAL and csum_start. Returning those values too would
overcomplicate the function signature.
> > +{
> > + return -EOPNOTSUPP;
> > +}
> > +
> > __diag_pop();
> >
> > BTF_SET8_START(xdp_metadata_kfunc_ids)
> > --
> > 2.41.0
> >
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