Re: [lwip-users] 2 netifs and using netif_set_default() problems

[address@hidden]

Am 28.01.2019 um 19:16 schrieb Sergio R. Caprile:
> So, so far:
>
> When switching default interface with connections open, traffic stops
> going out on the former default interface (A) but starts going out on
> the new one (B), but using the former address (addrA):
> Default interface is A, traffic is going from addrA to addrX outside the
> local network, default interface is switched to B, and then I can see
> Ethernet frames on B with the addrA, being sent to the default gateway
> (on B).
>
> The point is... Being that lwIP does not route, is it allowed to call
> netif_set_default() with connections open ? Is there anything else to
> check/prevent ? (in addition to properly dropping connections and
> starting them again as on an address change)
> Simon, guys ?

Well, lwIP *does* route: it sends packets to a default route if the 
destination IP is outside of the subnets of all the netifs.

So as long as you have a default gateway set on both netifs and that 
gateway can route to the wherever you want to connect (route, not NAT!), 
the remote host won't even notice: the packet's IP addresses will remain 
the same, they will only take a different route to the destination.

Of course, that's different with NAT gateways. You won't want to switch 
to/from such a gateway by switching default netifs, as here, your 
externally visible IP will change...

Regards,
Simon