Re: [B.A.T.M.A.N.] Implement DAT for IPv6

[Antonio Quartulli <ordex@autistici.org>]

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On Fri, Mar 01, 2013 at 12:59:18PM +0200, Mihail Costea wrote:
> Hi,
> 
> I've started implementing DAT for IPv6 and I have a few questions
> regarding the design.
> I've already implemented a snooping mechanism for Network Solicitation
> package, but now I have to add it to the ipv6 distributed table.
> I'm also a beginner in kernel programming so any help would be useful.
> 
> From what I've seen there is a lot of code in distributed-arp-table.c
> that could be used for ipv6 distributed table.

yeah, I think that the table handling and DHT primitives can be reused for IPv6
(they were designed on purpose).

> A problem in using that code, from what I've seen, is the fact that
> <struct batadv_dat_entry > has a field for ip with only 32 bits
> (__be32).

Yes, here a way to generalise the structure is needed.

> 
> So I was thinking to make it more general by:
> 1. transforming that into a pointer (unsigned char *ip) and add a
> field size which will represent the total size of the ip.
> The ip itself would be allocated dynamically.
> 2. use a union with both _be32 / struct in6_addr. In this case the
> problem is that if we use ipv4 then all the other space for struct
> in6_addr would be wasted.

correct. and for point 2) I think we waste a not negligible amount of memory..

> 
> The second problem from what I've seen in the code is that the
> batadv_priv->dat field is hardcoded.
> For ipv6 we would need a new field to memorize the table, but I don't
> think it's a really hard problem to solve in order to make it general.
> 

I did not get the problem with the dat field?
Can't you use the same table to store both IPv4 and IPv6? The DHT is made to
store general data, so I think (with the suggestions you wrote above) that you
should be able to use one table only.

> This solution would be to avoid code duplicate. Off course, I could
> still write all the code in parallel just for IPv6, but I think that a
> common base would be useful.
> 

Re-use code is definitely the way to go :) easy maintenance later, one single
point for bug-fixing and code has been tested already (so it should work[tm] as
expected :-))

> Thanks,

no worries :)

Cheers,

-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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