netdev - Re: [PATCH iproute2-next] ip tunnel: add json output

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Message-ID: <CAPpH65wSxeXGQc+r+7W_LRZR=vjnL2bXfub1U10vt-Gni67+kQ@mail.gmail.com>
Date:   Fri, 2 Aug 2019 13:14:15 +0200
From:   Andrea Claudi <aclaudi@...hat.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     linux-netdev <netdev@...r.kernel.org>,
        David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH iproute2-next] ip tunnel: add json output

On Thu, Aug 1, 2019 at 5:16 PM Stephen Hemminger
<stephen@...workplumber.org> wrote:
>
> On Thu,  1 Aug 2019 12:12:58 +0200
> Andrea Claudi <aclaudi@...hat.com> wrote:
>
> > Add json support on iptunnel and ip6tunnel.
> > The plain text output format should remain the same.
> >
> > Signed-off-by: Andrea Claudi <aclaudi@...hat.com>
> > ---
> >  ip/ip6tunnel.c | 82 +++++++++++++++++++++++++++++++--------------
> >  ip/iptunnel.c  | 90 +++++++++++++++++++++++++++++++++-----------------
> >  ip/tunnel.c    | 42 +++++++++++++++++------
> >  3 files changed, 148 insertions(+), 66 deletions(-)
> >
> > diff --git a/ip/ip6tunnel.c b/ip/ip6tunnel.c
> > index d7684a673fdc4..f2b9710c1320f 100644
> > --- a/ip/ip6tunnel.c
> > +++ b/ip/ip6tunnel.c
> > @@ -71,57 +71,90 @@ static void usage(void)
> >  static void print_tunnel(const void *t)
> >  {
> >       const struct ip6_tnl_parm2 *p = t;
> > -     char s1[1024];
> > -     char s2[1024];
> > +     SPRINT_BUF(b1);
> >
> >       /* Do not use format_host() for local addr,
> >        * symbolic name will not be useful.
> >        */
> > -     printf("%s: %s/ipv6 remote %s local %s",
> > -            p->name,
> > -            tnl_strproto(p->proto),
> > -            format_host_r(AF_INET6, 16, &p->raddr, s1, sizeof(s1)),
> > -            rt_addr_n2a_r(AF_INET6, 16, &p->laddr, s2, sizeof(s2)));
> > +     open_json_object(NULL);
> > +     print_string(PRINT_ANY, "ifname", "%s: ", p->name);
>
> Print this using color for interface name?

Thanks for the suggestion, I can do the same also for remote and local
addresses?

>
>
> > +     snprintf(b1, sizeof(b1), "%s/ipv6", tnl_strproto(p->proto));
> > +     print_string(PRINT_ANY, "mode", "%s ", b1);
> > +     print_string(PRINT_ANY,
> > +                  "remote",
> > +                  "remote %s ",
> > +                  format_host_r(AF_INET6, 16, &p->raddr, b1, sizeof(b1)));
> > +     print_string(PRINT_ANY,
> > +                  "local",
> > +                  "local %s",
> > +                  rt_addr_n2a_r(AF_INET6, 16, &p->laddr, b1, sizeof(b1)));
> > +
> >       if (p->link) {
> >               const char *n = ll_index_to_name(p->link);
> >
> >               if (n)
> > -                     printf(" dev %s", n);
> > +                     print_string(PRINT_ANY, "link", " dev %s", n);
> >       }
> >
> >       if (p->flags & IP6_TNL_F_IGN_ENCAP_LIMIT)
> > -             printf(" encaplimit none");
> > +             print_bool(PRINT_ANY,
> > +                        "ip6_tnl_f_ign_encap_limit",
> > +                        " encaplimit none",
> > +                        true);
>
> For flags like this, print_null is more typical JSON than a boolean
> value. Null is better for presence flag. Bool is better if both true and
> false are printed.

Using print_null json JSON output becomes:

  {
    "ifname": "gre2",
    "mode": "gre/ipv6",
    "remote": "fd::1",
    "local": "::",
    "ip6_tnl_f_ign_encap_limit": null,
    "hoplimit": 64,
    "tclass": "0x00",
    "flowlabel": "0x00000",
    "flowinfo": "0x00000000",
    "flags": []
  }

Which seems a bit confusing to me (what does the "null" value means?).
Using print_null we also introduce an inconsistency with the JSON
output of ip/link_gre6.c and ip/link_ip6tnl.c.
I would prefer to use print_bool and print out
ip6_tnl_f_ign_encap_limit both when true and false, patching both
files above to do the same. WDYT?