On Tue, 7 Jun 2016 16:31:21 +0100 Stuart Henderson <[email protected]> wrote: > On 2016/06/07 14:39, Gerhard Roth wrote: > > > > Now I get an IP address from my provider, I want something like this: > > > > > > > > inet 10.75.178.41 --> 10.75.178.42 netmask 0xfffffffc > > > > > > > > But if I used SIOCAIFADDR I would get this instead: > > > > > > > > inet 0.0.0.1 --> 0.0.0.2 netmask 0xff000000 > > > > inet 10.75.178.41 --> 10.75.178.42 netmask 0xfffffffc > > > > > > > > And deleting the old one first seems more racy. > > > > > > Why? > > > > Because either there is a time without any IP address or there > > is one with two addresses. Neither seems right. > > Is there a problem to have no address? That is what happens with > gif(4), tun(4) etc, even with ethernet interfaces, when they don't > have a particular address configured on them. > > There doesn't seem a particular problem with dhclient removing > the old address before it adds a new one.. > > > See above. That's the current OpenBSD model for PPP. > > There are several models :-) > > The 0.0.0.1 thing is a specific hack for sppp/pppoe which has > "magic" values of 0.0.0.0 and 0.0.0.1 and a way to request a > specific hardcoded address. This is because *both* sides > propose addresses via IPCP (they are "equal" peers as far > as configuration is concerned), they have to agree and can > NAK each other. > > It's not the only way though, even for PPP; ppp(4) doesn't use > this mechanism, it has separate configuration for pppd instead. > When we had ppp(8), that didn't, either. > > As far as I understand MBIM addressing is driven from the "mobile > network" side, we just set the address they are telling us to use > without a way to propose our own address. If that's correct then > we don't need a way to set "our side's" address at all, or have > a way to tie down the remote side's address, so address > configuration can be a lot simpler than any PPP interface.
I not sure if it is possible to send packets from an interface that has no addresses assigned to it. And then, the MBIM standard says nothing about the network segment. My provider just gives me some non-routable 10.x.x.x IP, but I think that it would be totally legal to assign some public IPv4 address to me. In that case it is mandatory that we assign this address to our local interface. > > > > But when you lose the connection with the network or you manually set > > > the interface down, this IP address once given to you by the provider > > > is no longer yours and must not be used anymore. > > The same can apply in other cases (wifi, wired ethernet etc) too, > but we don't do anything to remove it from those interfaces (though > it's easy enough to remove using ifstated if needed). For WiFi and Ethernet it is dhclient that will remove the old addresses.
