Subject: Re: [PATCH RESEND bpf-next 11/15] xdp: Add checksum level hint

From: Larysa Zaremba <[email-masked]>
Date: Mon, 15 May 2023 15:49:29 +0200

On Fri, May 12, 2023 at 11:34:21AM -0700, Stanislav Fomichev wrote:
> On 05/12, 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 <[email-masked]>
> > ---
> >  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                               | 12 ++++++++++++
> >  5 files changed, 20 insertions(+)
> > 
> > diff --git a/Documentation/networking/xdp-rx-metadata.rst b/Documentation/networking/xdp-rx-metadata.rst
> > index 73a78029c596..f74f0e283097 100644
> > --- a/Documentation/networking/xdp-rx-metadata.rst
> > +++ b/Documentation/networking/xdp-rx-metadata.rst
> > @@ -29,6 +29,9 @@ metadata is supported, this set will grow:
> >  .. kernel-doc:: net/core/xdp.c
> >     :identifiers: bpf_xdp_metadata_rx_stag
> >  
> > +.. 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 fdae37fe11f5..ddade3a15366 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -1657,6 +1657,7 @@ struct xdp_metadata_ops {
> >  			       enum xdp_rss_hash_type *rss_type);
> >  	int	(*xmo_rx_ctag)(const struct xdp_md *ctx, u16 *vlan_tag);
> >  	int	(*xmo_rx_stag)(const struct xdp_md *ctx, u16 *vlan_tag);
> > +	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 2db7439fc60f..0fbd25616241 100644
> > --- a/include/net/xdp.h
> > +++ b/include/net/xdp.h
> > @@ -393,6 +393,8 @@ void xdp_attachment_setup(struct xdp_attachment_info *info,
> >  			   bpf_xdp_metadata_rx_ctag) \
> >  	XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_STAG, \
> >  			   bpf_xdp_metadata_rx_stag) \
> > +	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 2c6b6e82cfac..8bd54fb4ac63 100644
> > --- a/kernel/bpf/offload.c
> > +++ b/kernel/bpf/offload.c
> > @@ -852,6 +852,8 @@ void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
> >  		p = ops->xmo_rx_ctag;
> >  	else if (func_id == bpf_xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_STAG))
> >  		p = ops->xmo_rx_stag;
> > +	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 eff21501609f..7dd45fd62983 100644
> > --- a/net/core/xdp.c
> > +++ b/net/core/xdp.c
> > @@ -762,6 +762,18 @@ __bpf_kfunc int bpf_xdp_metadata_rx_stag(const struct xdp_md *ctx, u16 *vlan_tag
> >  	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.
> 
> Let's maybe clarify what the level means here? For example, do we start
> counting from 0 or 1?

Sure, I'll add a comment that the meaning of level is the same as in skb, 
counting from 0.

> 
> > + *
> > + * Returns 0 on success (HW has checked the checksum) or ``-errno`` on error.
> > + */
> > +__bpf_kfunc int bpf_xdp_metadata_rx_csum_lvl(const struct xdp_md *ctx, u8 *csum_level)
> > +{
> > +	return -EOPNOTSUPP;
> > +}
> > +
> >  __diag_pop();
> >  
> >  BTF_SET8_START(xdp_metadata_kfunc_ids)
> > -- 
> > 2.35.3
> >