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

[Ivan Delamer]

> Date: Tue, 26 May 2015 17:06:48 -0700
> From: pradip de <address@hidden>
> To: address@hidden
> Subject: Re: [lwip-devel] Adding a static route table in LwIP
> Message-ID:
>         <address@hidden>
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>
> Hi Ivan,
>
> Thanks again for the suggestion.
>
> The LWIP_HOOK_IP6_ROUTE seems like a callback to higher level
> implementation of a routing function. Sure it could be used for a 
> static
> route check as well. However, the purpose of this hook is only to 
> return an
> outgoing netif, correct?
>
> But what if the static route entry has a gateway that needs to be 
> picked up
> during selection of a next hop. There needs to be logic in 
> nd6_get_next_hop
> code that looks up the static route table to fetch the gateway as the
> neighbor to send to.
>
> For some reason it seems to me that a static route table is a basic 
> feature
> and could be a separate part(albeit within conditional compilation 
> flags)
> of the core IP6 routing mechanism instead of as a plugin or hook. 
> Plugins
> or hooks are probably apt for hooking up advanced or sophisticated 
> routing
> functions.
>
> Thanks,
>
> Pradip

Yes, LWIP_HOOK_IP6_ROUTE would check your static route table and return 
the suitable netif. Based on netif selection, the stack would select a 
suitable source address.

In your netif->output_ip6 function, you resolve the next hop. Take a 
look at ethip6_output(), you can use it as a template. You could insert 
your static route lookup code before the nd6_get_next_hop_entry() call. 
You don't need to use ethip6_output(), you can choose your own 
implementation when you add your netif.

Because static routing can be done in so many ways, I believe it should 
remain separate from ND6. We aim to be RFC compliant. I don't know that 
we could come up with a static route module that would satisfy everyone.

My suggestion is that you post your work on Savannah as a patch, so 
that other people can benefit from it. If we see enough interest over 
time, and it proves stable, we can look at adding it to the master 
branch. That's actually how the IPv6 code started, as an optional patch. 
We may also create a development branch for this if we have several 
developers working on it.

Cheers
Ivan