[openbeosnetteam] Re: Interfaces

"Waldemar Kornewald" <wkornew@xxxxxxx> wrote:
> On 7/12/06, Axel Dörfler <axeld@xxxxxxxxxxxxxxxx> wrote:
> > > I was talking about the ethernet interface, not the PPP 
> > > interface. As
> > > long as the ethernet interface is down I can't send any packets. 
> > > As
> > > long as the ethernet interface is unconfigured (no IP) it's down.
> > > Thus, I can't send PPPoE packets over ethernet interfaces that 
> > > don't
> > > have an IP address, so I have to assign some address like
> > > "192.168.0.1" just to be able to use PPPoE over that ethernet
> > > interface.
> > You're still managing to confuse me :-)
> Heh, we can chat about it some day, if you want. :)

I'm confident that we manage it this way, too :-))

> > You never send PPPoE packets over an ethernet interface. You only 
> > send
> > them over an ethernet device. And it's absolutely correct that 
> > those
> > packets are rejected if the PPP interface (and therefore the 
> > ethernet
> > device) is down.
> > The way I think, when the IFF_AUTOUP flag is set, the interface 
> > will
> > try to "up" itself (which will also "up" the ethernet device) 
> > before
> > rejecting the packet, though.
> But how can the PPP interface "up" the ethernet interface if it
> doesn't know which IP address to use for the ethernet interface
> (192.168.0.1 or 192.168.0.2 or DHCP or maybe something totally
> different)? The current netstack doesn't have any configuration 
> files,
> so just doing an "up" on an ethernet interface won't work.

Argl. Again, there is *NO* ethernet *interface* involved. And the 
actual ethernet device will be brought up automatically by the stack as 
soon as the PPP interface is brought up - as the PPP interface is using 
that net_device.
When you set the IFF_UP flag, the stack tries to bring up the 
datalink_protocols, and only if that fails, it will reject the IFF_UP 
flag: since PPPoE is a datalink_protocol, it will forward the "up" to 
the next layer (the ethernet framing module), and if that succeeded, it 
can try to create a PPP session. If that fails, it would "down" the 
next layer again, and report failure which let's the stack reject the 
IFF_UP flag.

Bye,
   Axel.

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