Re: [lwip-devel] Adding a static route table in LwIP

[Daniel Gutson]

On Thu, May 21, 2015 at 12:59 PM, Ivan Delamer <address@hidden> wrote:
> Hi Pradip,
>
> I think a static IPv6 route table is a nice feature to have. I think some
> people have implemented something similar for IPv4. Also someone has
> implemented a NAT.

Hi all.

Sorry if my question/suggestion is completely out of place. Please
note that I'm not a telecommunications expert,
but a user (of real time and embedded systems which use LwIP).

Would adding this as a plug-in be a good idea?
Or more specifically: would an extension mechanism where features like
this one could be added
aside of the core library? Of course I don't mean dynamic loading, but
just to provide a set of hooks
placed in the right places so extensions could register callbacks.

Could that make sense? The first step would be to add the appropriate
hooks (then refactor this feature
and possible other features such as NAT as well, so they can be
written as opt-in extensions?).
The main purpose would be neat maintainability.

Please let me know. If this happens to make sense, we could see how to
collaborate.

Thanks!

   Daniel.


>
> I would recommend that you implement this in a separate file than nd6,
> instead of using lots of conditional blocks.
>
> neighbour discovery is usually called from netif->output_ip6, what you can
> do is: in your implementation of this function, before calling nd6 you can
> check with your static routing table for the next hop.
>
> You might have to hack ip6_route() like you propose if you need to use a
> static router.
>
> But all of this seems really similar to me to the current routing system,
> except we don't have an API for adding static entries. What I would do is
> simply expose some of the nd6 methods (make them non-static) and add your
> routers and next-hop entries. You might have to periodically refresh your
> routers' invalidation timers, but that is anyways a good idea.
>
> This is how I do it in a project where I manually enter the router address.
>
> Cheers
> Ivan
>
>
>
>
>> Date: Wed, 20 May 2015 17:20:08 -0700
>> From: pradip de <address@hidden>
>> To: address@hidden
>> Subject: [lwip-devel] Adding a static route table in LwIP
>> Message-ID:
>>
>> <address@hidden>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Hi,
>> As part of my current project, I am working on an LwIP enhancement of
>> adding a static route table and wanted to share in this forum and get
>> feedback.
>>
>> The static route table entry would have a prefix, a netif and an optional
>> gateway.
>> The APIs would look something like:
>>
>> 1) s8_t ip6_add_route_entry (struct ip6_prefix *ip6_prefix, struct netif
>> *netif, ip6_addr_t *gateway);
>>
>> 2) err_t ip6_remove_route_entry (struct ip6_prefix *ip6_prefix);
>>
>> 3) s8_t ip6_find_route_entry (ip6_addr_t *ip6_dest_addr);
>>
>> When adding a route entry, if a gateway is passed, then it would be added
>> to the default router list with the neighbor cache netif entry pointing to
>> the netif passed. I believe neighbor discovery performed every second
>> would
>> send router solicitations to fetch the link address for that entry.
>> A route lookup using ip6_find_route_entry would be invoked from within
>> ip6_route before the check to find a default router.
>> Currently, only a netcmp of the entire 64 bit prefix is done for matching
>> prefixes. However, in this enhancement, a prefix match up to a specific
>> prefix byte boundary would be made possible and a longest prefix match
>> performed.
>> All of these changes would be encapsulated within a conditional
>> compilation
>> flag.
>>
>> Please let me know if there are any concerns around this feature or any
>> suggestions in this regard.
>>
>> Thanks,
>> Pradip
>
>
>
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Daniel F. Gutson
Chief Engineering Officer, SPD

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