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

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Message-ID: <CAPpH65wMUeRM05UNdwQqHOCUtxwbxVArsqbY=Yi-PP=cnxxc0w@mail.gmail.com>
Date:   Fri, 2 Aug 2019 19:30:39 +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 Fri, Aug 2, 2019 at 5:49 PM Stephen Hemminger
<stephen@...workplumber.org> wrote:
>
> On Fri, 2 Aug 2019 13:14:15 +0200
> Andrea Claudi <aclaudi@...hat.com> wrote:
>
> > 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?
>
> JSON has several ways to represent the same type of flag value.
> Since JSON always has key/value. Null is used to indicate something is present and
> in that case the value is unnecessary, which is what the null field was meant for.
>

Thanks for the clarification, Stephen.
I'll submit a v2 with print_null and I'll fix cases similar to the one
you highlighted above in subsequent patches.