Re: [lwip-users] Routing and link up/down vs. netif up/down

[Fabian Koch]

Hey Simon,

> This is the first problem. A setup like this is not really supported in lwIP. 
> We do have additional hooks to enable this, but it's not meant to work 
> out-of-the-box.
I only found LWIP_HOOK_IP4_INPUT and LWIP_HOOK_IP4_ROUTE.

> In recent versions (or in git master only?) you can provide a routing hook 
> function to 
> help lwIP implement more sophisticated routing like you need here.
Yeah. That is already in 1.4.1 which we use.
But it only gives the destination. For what I had in mind, I'd also need the 
source IP or to be more precise, the IP that the sender was bound to.

> I'm just guessing you're trying to implement media redundancy this way...; 
> but one  could also be trying to implement link aggregation with that setup, 
> just for an example. This is why we don't really want to support it in the 
> core code.
Well yes and no. I don't decide how the customer will use the two interfaces.
But if he does attach them to the same subnet and wants to have cable 
redundancy, it should behave in a way that works at least similar to what a 
full fledged IP stack like the linux one would.

> Plus you have to pay attention that anything you change to make your 'two 
> netifs in
> one subnet' work doesn't break the default case of having two netifs each 
> in their own subnet.

Well that is why I start a discussion here. So I can take all that I don't know 
inot account ;o)

Cheers,
Fabian