netdev - Re: [PATCH iproute2-next 2/7] iproute_lwtunnel: add options support for vxlan metadata

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Date:   Mon, 10 Feb 2020 14:09:17 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     network dev <netdev@...r.kernel.org>,
        Simon Horman <simon.horman@...ronome.com>,
        Pieter Jansen van Vuuren 
        <pieter.jansenvanvuuren@...ronome.com>
Subject: Re: [PATCH iproute2-next 2/7] iproute_lwtunnel: add options support
 for vxlan metadata

On Wed, Feb 5, 2020 at 8:22 PM Stephen Hemminger
<stephen@...workplumber.org> wrote:
>
> On Mon,  3 Feb 2020 13:39:53 +0800
> Xin Long <lucien.xin@...il.com> wrote:
>
> > +static void lwtunnel_print_vxlan_opts(struct rtattr *attr, char *opt)
> > +{
> > +     struct rtattr *tb[LWTUNNEL_IP_OPT_VXLAN_MAX + 1];
> > +     __u32 gbp;
> > +
> > +     parse_rtattr(tb, LWTUNNEL_IP_OPT_VXLAN_MAX, RTA_DATA(attr),
> > +                  RTA_PAYLOAD(attr));
> > +     gbp = rta_getattr_u32(tb[LWTUNNEL_IP_OPT_VXLAN_GBP]);
> > +     sprintf(opt, "%x", gbp);
> > +     print_string(PRINT_FP, "enc_opt", "\n  vxlan_opts %s ", opt);
>
> You need to handle single line mode and JSON.
>
> Proper way is something like:
>
>         print_nl();
>         print_0xhex(PRINT_ANY, "enc_opt", "  vxlan_opts %#x", gpb);
>
yeah, right, didn't notice that, thanks.

> Also, why the hex format, this is a an opaque user interface?
>

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |G|R|R|R|I|R|R|R|R|D|R|R|A|R|R|R|        Group Policy ID        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

This is the gbp field in vxlan header, defined in:

  https://tools.ietf.org/html/draft-smith-vxlan-group-policy-05

I think 'hex' makes it clearer than decimal to see which bit is set
for users, no?