Re: [ECOS] Re: Disable IPv6 at startup?

[Sergei Gavrikov <sergei dot gavrikov at gmail dot com>]

On Thu, 1 Mar 2012, Grant Edwards wrote:

> On 2012-03-01, Sergei Gavrikov wrote:
> > On Wed, 29 Feb 2012, Grant Edwards wrote:
> >
> > [snip]
> >
> >> OK, I've come up with something I like a little better.  The only
> >> change it requires to the network stack is that ip6_init2() needs to
> >> be globally visible (ip6_init already is, so I don't see the harm in
> >> making ip6_init2 visible).  If ip6_init2 is visible, then you can
> >> disable ipv6 support with this code:
> >> 
> >> static void init_noop(void* dummy)
> >> {
> >> }
> >> 
> >> static void disable_ipv6(void)
> >> {
> >>   extern void cyg_net_add_domain(void *);
> >>   extern void ip6_init2(void *);
> >>   extern char inet6domain[];
> >>   extern struct init_tab_entry __NET_INIT_TAB__[], __NET_INIT_TAB_END__;
> >>   struct init_tab_entry *init_entry;
> >> 
> >>   for (init_entry = __NET_INIT_TAB__; init_entry != &__NET_INIT_TAB_END__;  init_entry++) 
> >>       if ((init_entry->fun == cyg_net_add_domain && init_entry->data == (void*)inet6domain) ||
> >>           (init_entry->fun == ip6_init2))
> >>           init_entry->fun = init_noop;
> >> }
> 
> In case anybody is wondering, ip6_init() is called via the domain
> startup code via a pointer that's present in the "struct domain"
> initializer for inet6domain. Disabling the call to
> cyg_net_add_domain(&inet6domain) as shown above is what prevents
> ip6_init() from being called.
> 
> > IMHO, it is neat solution. Thanks for usage example. BTW, the KAME's
> > successors had declared ip6_init2() as you suggest:
> >
> >   http://ftp.fr.openbsd.org/pub/OpenBSD/src/sys/netinet6/ip6_input.c
> >
> > Please, submit the patch.
> 
> OK, will do.  I noticed after that last post that ip6_init is renamed
> to cyg_ip6_init by one of the include files.

Yes, I'm seeing that was entered in a merge/fix patch from Kelvin Lawson
in 2011. But there is also

  include/sys/param.h:224:#define ip6_init cyg_ip6_init

> I assume I should do the same thing for ip6_init2 if it's going to be
> global?

I have doubt.  May be to change a scope of the function in ip6_input.c
will be enough for the case?  As for me I would not propagate the
definition {cyg_,}ip6_init2 in the headers.  Though, may be I wrong
here. I would stop on your first proposal:

 -static void ...
 +void ...

Sergei

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