Hi Alex, aahringo@xxxxxxxxxx wrote on Sat, 11 Jun 2022 08:23:41 -0400: > Hi, > > On Thu, Jun 9, 2022 at 11:52 AM Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > > > > Hi Alexander, > > > > aahringo@xxxxxxxxxx wrote on Wed, 8 Jun 2022 21:56:53 -0400: > > > > > Hi, > > > > > > On Wed, Jun 8, 2022 at 9:47 AM Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > > > > > > > > Hi Alex, > > > > > > > > > > 3. coordinator (any $TYPE specific) userspace software > > > > > > > > > > > > May the main argument. Some coordinator specific user space daemon > > > > > > does specific type handling (e.g. hostapd) maybe because some library > > > > > > is required. It is a pain to deal with changing roles during the > > > > > > lifetime of an interface and synchronize user space software with it. > > > > > > We should keep in mind that some of those handlings will maybe be > > > > > > moved to user space instead of doing it in the kernel. I am fine with > > > > > > the solution now, but keep in mind to offer such a possibility. > > > > > > > > > > > > I think the above arguments are probably the same why wireless is > > > > > > doing something similar and I would avoid running into issues or it's > > > > > > really difficult to handle because you need to solve other Linux net > > > > > > architecture handling at first. > > > > > > > > > > Yep. > > > > > > > > The spec makes a difference between "coordinator" and "PAN > > > > coordinator", which one is the "coordinator" interface type supposed to > > > > picture? I believe we are talking about being a "PAN coordinator", but > > > > I want to be sure that we are aligned on the terms. > > > > > > > > > > I think it depends what exactly the difference is. So far I see for > > > address filtering it should be the same. Maybe this is an interface > > > option then? > > > > The difference is that the PAN coordinator can decide to eg. refuse an > > association, while the other coordinators, are just FFDs with no > > specific decision making capability wrt the PAN itself, but have some > > routing capabilities available for the upper layers. > > > > As I said, if there is a behaviour "it can do xxx, but the spec > doesn't give more information about it" this smells for me like things > moving into the user space. This can also be done e.g. by a filtering > mechanism, _just_ the user will configure how this filtering will look > like. > > > The most I look into this, the less likely it is that the Linux stack > > will drive an RFD. Do you think it's worth supporting them? Because if > > we don't: > > * NODE == FFD which acts as coordinator > > * COORD == FFD which acts as the PAN coordinator > > > > I thought that this is a kind of "transceiver type capability " e.g. I > can imagine if it's only a "RFD" transceiver then you would be e.g. > not able to set the address filter to coordinator capability. However > I think that will never happen for a SoftMAC transceiver because why > not adding a little bit silicon to provide that? People also can > always have a co-processor and run the transceiver in promiscuous > mode. E.g. atusb (which makes this transceiver poweful, because we > have control over the firmware). > > For me node != coord, because the address filtering is different. As I > mentioned in another mail "coordinator" vs "PAN coordinator" as > described is what the user is doing here on top of it. > > > > > > > > > You are mixing things here with "role in the network" and what > > > > > > > > the transceiver capability (RFD, FFD) is, which are two > > > > > > > > different things. > > > > > > > > > > > > > > I don't think I am, however maybe our vision differ on what an > > > > > > > interface should be. > > > > > > > > > > > > > > > You should use those defines and the user needs to create a new > > > > > > > > interface type and probably have a different extended address > > > > > > > > to act as a coordinator. > > > > > > > > > > > > > > Can't we just simply switch from coordinator to !coordinator > > > > > > > (that's what I currently implemented)? Why would we need the user > > > > > > > to create a new interface type *and* to provide a new address? > > > > > > > > > > > > > > Note that these are real questions that I am asking myself. I'm > > > > > > > fine adapting my implementation, as long as I get the main idea. > > > > > > > > > > > > > > > > > > > See above. > > > > > > > > > > That's okay for me. I will adapt my implementation to use the > > > > > interface thing. In the mean time additional details about what a > > > > > coordinator interface should do differently (above question) is > > > > > welcome because this is not something I am really comfortable with. > > > > > > > > I've updated the implementation to use the IFACE_COORD interface and it > > > > works fine, besides one question below. > > > > > > > > Also, I read the spec once again (soon I'll sleep with it) and > > > > actually what I extracted is that: > > > > > > > > * A FFD, when turned on, will perform a scan, then associate to any PAN > > > > it found (algorithm is beyond the spec) or otherwise create a PAN ID > > > > and start its own PAN. In both cases, it finishes its setup by > > > > starting to send beacons. > > > > > > > > > > What does it mean "algorithm is beyond the spec" - build your own? > > > > This is really what is in the spec, I suppose it means "do what you > > want in your use case". > > > > What I have in mind: when a device is powered on and detects two PANs, > > well, it can join whichever it wants, but perhaps we should make the > > decision based on the LQI information we have (the closer the better). > > > > As I said in the other mail, this smells more and more for me to move > this handling to user space. The kernel therefore supports operations > to trigger the necessary steps (scan/assoc/etc.) > > > > > * A RFD will behave more or less the same, without the PAN creation > > > > possibility of course. RFD-RX and RFD-TX are not required to support > > > > any of that, I'll assume none of the scanning features is suitable > > > > for them. > > > > > > > > I have a couple of questions however: > > > > > > > > - Creating an interface (let's call it wpancoord) out of wpan0 means > > > > that two interfaces can be used in different ways and one can use > > > > wpan0 as a node while using wpancoord as a PAN coordinator. Is that > > > > really allowed? How should we prevent this from happening? > > > > > > > > > > When the hardware does not support it, it should be forbidden. As most > > > transceivers have only one address filter it should be forbidden > > > then... but there exists a way to indeed have such a setup (which you > > > probably don't need to think about). It's better to forbid something > > > now, with the possibility later allowing it. So it should not break > > > any existing behaviour. > > > > Done, thanks to the pointer you gave in the other mail. > > > > > > > > > - Should the device always wait for the user(space) to provide the PAN > > > > to associate to after the scan procedure right after the > > > > add_interface()? (like an information that must be provided prior to > > > > set the interface up?) > > > > > > > > - How does an orphan FFD should pick the PAN ID for a PAN creation? > > > > Should we use a random number? Start from 0 upwards? Start from > > > > 0xfffd downwards? Should the user always provide it? > > > > > > > > > > I think this can be done all with some "fallback strategies" (build > > > your own) if it's not given as a parameter. > > > > Ok, In case no PAN is found, and at creation no PAN ID is provided, we > > can default to 0. > > > > See me for other mails. (user space job) > > > > > - Should an FFD be able to create its own PAN on demand? Shall we > > > > allow to do that at the creation of the new interface? > > > > > > > > > > I thought the spec said "or otherwise"? That means if nothing can be > > > found, create one? > > > > Ok, so we assume this is only at startup, fine. But then how to handle > > the set_pan_id() call? I believe we can forbid any set_pan_id() command > > to be run while the interface is up. That would ease the handling. > > Unless I am missing something? > > > > See my other mails (user space job). Ok then, I'll go with the following constraints in mind: SCAN (passive/active) (all devices) - All devices are allowed to perform scans. - The user decides when a scan must be performed, there is no limitation on when to do a scan (but the interface must be up for physical reasons). PAN ID - The user is responsible to set the PAN ID. - Like several other parameters, the PAN ID can only be changed if the iface is down. Which means the user might need to do: link up > scan > link down > set params > link up BEACON - Coordinator interfaces only can send beacons. - Beacons can only be sent when part of a PAN (PAN ID != 0xffff). - The choice of the beacon interval is up to the user, at any moment. OTHER PARAMETERS - The choice of the channel (page, etc) is free until the device is associated to another, then it becomes fixed. ASSOCIATION (to be done) - Device association/disassociation procedure is requested by the user. - Accepting new associations is up to the user (coordinator only). - If the device has no parent (was not associated to any device) it is PAN coordinator and has additional rights regarding associations. Thanks, Miquèl
