netdev - Re: [PATCH iproute2] ip route: Make name of protocol 0 consistent

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Date:   Tue, 7 Feb 2017 13:40:35 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     David Ahern <dsa@...ulusnetworks.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] ip route: Make name of protocol 0 consistent

On Mon, 6 Feb 2017 16:03:35 -0700
David Ahern <dsa@...ulusnetworks.com> wrote:

> On 2/6/17 3:01 PM, Stephen Hemminger wrote:
> > On Thu,  2 Feb 2017 09:22:06 -0800
> > David Ahern <dsa@...ulusnetworks.com> wrote:
> >   
> >> iproute2 can inconsistently show the name of protocol 0 if a route with
> >> a custom protocol is added. For example:
> >>   dsa@...tman:~$ ip -6 ro ls table all | egrep 'proto none|proto unspec'
> >>   local ::1 dev lo  table local  proto none  metric 0  pref medium
> >>   local fe80::225:90ff:fecb:1c18 dev lo  table local  proto none  metric 0  pref medium
> >>   local fe80::92e2:baff:fe5c:da5d dev lo  table local  proto none  metric 0  pref medium
> >>
> >> protocol 0 is pretty printed as "none". Add a route with a custom protocol:
> >>   dsa@...tman:~$ sudo ip -6 ro add  2001:db8:200::1/128 dev eth0 proto 123
> >>
> >> And now display has switched from "none" to "unspec":
> >>   dsa@...tman:~$ ip -6 ro ls table all | egrep 'proto none|proto unspec'
> >>   local ::1 dev lo  table local  proto unspec  metric 0  pref medium
> >>   local fe80::225:90ff:fecb:1c18 dev lo  table local  proto unspec  metric 0  pref medium
> >>   local fe80::92e2:baff:fe5c:da5d dev lo  table local  proto unspec  metric 0  pref medium
> >>
> >> The rt_protos file has the id to name mapping as "unspec" while
> >> rtnl_rtprot_tab[0] has "none". The presence of a custom protocol id
> >> triggers reading the rt_protos file and overwriting the string in
> >> rtnl_rtprot_tab. All of this is logic from 2004 and earlier.
> >>
> >> The simplest change to achieve consistency is to update the rt_protos
> >> file to use "none" instead of "unspec".
> >>
> >> Signed-off-by: David Ahern <dsa@...ulusnetworks.com>
> >> ---
> >>  etc/iproute2/rt_protos | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/etc/iproute2/rt_protos b/etc/iproute2/rt_protos
> >> index 82cf9c46cf6f..21af85b9d7e1 100644
> >> --- a/etc/iproute2/rt_protos
> >> +++ b/etc/iproute2/rt_protos
> >> @@ -1,7 +1,7 @@
> >>  #
> >>  # Reserved protocols.
> >>  #
> >> -0	unspec
> >> +0	none
> >>  1	redirect
> >>  2	kernel
> >>  3	boot  
> > 
> > This doesn't look like a good solution, you loose the value of unspec.
> > 
> > Just to clarify. You added a custom protocol value to netlink.
> > And then you are using upstream iproute2 source to display the value.  
> 
> no. I am saying the string displayed for protocol '0' is changing. This
> is all within iproute2 code and files; it has 2 strings for protocol 0:
> 
> lib/rt_names.c:
> static char *rtnl_rtprot_tab[256] = {
>         [RTPROT_UNSPEC]   = "none",
> 
> and the rt_protos file above shows "unspec"
> 
> The presence of a custom protocol triggers the rt_protos file to be read:
> 
> const char *rtnl_rtprot_n2a(int id, char *buf, int len)
> {
>         if (id < 0 || id >= 256) {
>                 snprintf(buf, len, "%u", id);
>                 return buf;
>         }
>         if (!rtnl_rtprot_tab[id]) {
>                 if (!rtnl_rtprot_init)
>                         rtnl_rtprot_initialize();
> 
> 
> Reading the file changes the string in rtnl_rtprot_tab for
> RTPROT_UNSPEC. Both string values -- "none" and "unspec" come from
> iproute2, so my point is that string is inconsistent within iproute2.

Why not change the value in the table rtnl_rtprot_tab to be unspec this would
make the command consistent with the value in the header file.