Messages in this thread | | | Date | Mon, 23 Nov 2020 10:00:02 +0100 | From | Martin Schiller <> | Subject | Re: [PATCH net-next v4 2/5] net/lapb: support netdev events |
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On 2020-11-23 09:31, Xie He wrote: > On Sun, Nov 22, 2020 at 10:55 PM Martin Schiller <ms@dev.tdt.de> wrote: >> >> No, they aren't independent. The carrier can only be up if the device >> / >> interface is UP. And as far as I can see a NETDEV_CHANGE event will >> also >> only be generated on interfaces that are UP. >> >> So you can be sure, that if there is a NETDEV_CHANGE event then the >> device is UP. > > OK. Thanks for your explanation! > >> I removed the NETDEV_UP handling because I don't think it makes sense >> to implicitly try to establish layer2 (LAPB) if there is no carrier. > > As I understand, when the device goes up, the carrier can be either > down or up. Right? > > If this is true, when a device goes up and the carrier then goes up > after that, L2 will automatically connect, but if a device goes up and > the carrier is already up, L2 will not automatically connect. I think > it might be better to eliminate this difference in handling. It might > be better to make it automatically connect in both situations, or in > neither situations.
AFAIK the carrier can't be up before the device is up. Therefore, there will be a NETDEV_CHANGE event after the NETDEV_UP event.
This is what I can see in my tests (with the HDLC interface).
Is the behaviour different for e.g. lapbether?
> > If you want to go with the second way (auto connect in neither > situations), the next (3rd) patch of this series might be also not > needed. > > I just want to make the behavior of LAPB more consistent. I think we > should either make LAPB auto-connect in all situations, or make LAPB > wait for L3's instruction to connect in all situations. > >> And with the first X.25 connection request on that interface, it will >> be established anyway by x25_transmit_link(). >> >> I've tested it here with an HDLC WAN Adapter and it works as expected. >> >> These are also the ideal conditions for the already mentioned "on >> demand" scenario. The only necessary change would be to call >> x25_terminate_link() on an interface after clearing the last X.25 >> session. >> >> > On NETDEV_GOING_DOWN, we can also check the carrier status first and >> > if it is down, we don't need to call lapb_disconnect_request. >> >> This is not necessary because lapb_disconnect_request() checks the >> current state. And if the carrier is DOWN then the state should also >> be >> LAPB_STATE_0 and so lapb_disconnect_request() does nothing. > > Yes, I understand. I just thought adding this check might make the > code cleaner. But you are right.
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