netdev - Re: [PATCH v5 bpf-next 5/8] libbpf: add API to get XDP/XSK supported features

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Date:   Mon, 6 Feb 2023 23:55:02 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com, edumazet@...gle.com, hawk@...nel.org,
        toke@...hat.com, memxor@...il.com, alardam@...il.com,
        saeedm@...dia.com, anthony.l.nguyen@...el.com, gospo@...adcom.com,
        vladimir.oltean@....com, nbd@....name, john@...ozen.org,
        leon@...nel.org, simon.horman@...igine.com, aelior@...vell.com,
        christophe.jaillet@...adoo.fr, ecree.xilinx@...il.com,
        mst@...hat.com, bjorn@...nel.org, magnus.karlsson@...el.com,
        maciej.fijalkowski@...el.com, intel-wired-lan@...ts.osuosl.org,
        martin.lau@...ux.dev, sdf@...gle.com, gerhard@...leder-embedded.com
Subject: Re: [PATCH v5 bpf-next 5/8] libbpf: add API to get XDP/XSK supported
 features

> On Wed, Feb 1, 2023 at 2:25 AM Lorenzo Bianconi <lorenzo@...nel.org> wrote:
> >
> > Extend bpf_xdp_query routine in order to get XDP/XSK supported features
> > of netdev over route netlink interface.
> > Extend libbpf netlink implementation in order to support netlink_generic
> > protocol.
> >
> > Co-developed-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> > Co-developed-by: Marek Majtyka <alardam@...il.com>
> > Signed-off-by: Marek Majtyka <alardam@...il.com>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> >  tools/lib/bpf/libbpf.h  |  3 +-
> >  tools/lib/bpf/netlink.c | 96 +++++++++++++++++++++++++++++++++++++++++
> >  tools/lib/bpf/nlattr.h  | 12 ++++++
> >  3 files changed, 110 insertions(+), 1 deletion(-)
> >
> 
> [...]
> 
> > @@ -366,6 +433,10 @@ int bpf_xdp_query(int ifindex, int xdp_flags, struct bpf_xdp_query_opts *opts)
> >                 .ifinfo.ifi_family = AF_PACKET,
> >         };
> >         struct xdp_id_md xdp_id = {};
> > +       struct xdp_features_md md = {
> > +               .ifindex = ifindex,
> > +       };
> > +       __u16 id;
> >         int err;
> >
> >         if (!OPTS_VALID(opts, bpf_xdp_query_opts))
> > @@ -393,6 +464,31 @@ int bpf_xdp_query(int ifindex, int xdp_flags, struct bpf_xdp_query_opts *opts)
> >         OPTS_SET(opts, skb_prog_id, xdp_id.info.skb_prog_id);
> >         OPTS_SET(opts, attach_mode, xdp_id.info.attach_mode);
> >
> > +       if (!OPTS_HAS(opts, feature_flags))
> > +               return 0;
> > +
> > +       err = libbpf_netlink_resolve_genl_family_id("netdev", sizeof("netdev"), &id);
> > +       if (err < 0)
> > +               return libbpf_err(err);
> > +
> > +       memset(&req, 0, sizeof(req));
> > +       req.nh.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
> > +       req.nh.nlmsg_flags = NLM_F_REQUEST;
> > +       req.nh.nlmsg_type = id;
> > +       req.gnl.cmd = NETDEV_CMD_DEV_GET;
> > +       req.gnl.version = 2;
> > +
> > +       err = nlattr_add(&req, NETDEV_A_DEV_IFINDEX, &ifindex, sizeof(ifindex));
> > +       if (err < 0)
> > +               return err;
> 
> just noticed this, we need to use libbpf_err(err) here like in other
> error cases to set errno properly. Can you please send a follow up?

sure, I will post a fix.

Regards,
Lorenzo

> 
> > +
> > +       err = libbpf_netlink_send_recv(&req, NETLINK_GENERIC,
> > +                                      parse_xdp_features, NULL, &md);
> > +       if (err)
> > +               return libbpf_err(err);
> > +
> > +       opts->feature_flags = md.flags;
> > +
> >         return 0;
> >  }
> >
> 
> [...]
> 

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