Hi, On Sat, Jun 09, 2018 at 03:01:18PM -0400, Michael Richardson wrote: > > Alexander Aring <aring@xxxxxxxxxxxx> wrote: > > Futhermore user space programs e.g. radvd will do 6lowpan specific > > handling on 6lowpan dev->type, it will not work either on tun > > devices. > > > I know that wpantund from NestLabs do this switch, I am very > > curious about the reason but I think they do it because the name > > is 6LoWPAN. But wpantund is just a SLIP like protocol with > > additional radio/foo commands. > > How do they change it then, and what does it do? They change it with the ioctl() of tun characte device, see [0]. What it does, it just changing the interface type to something else, also there is no check at all that Linux has this interface type. User space software e.g. radvd [1] will evaluate this type and doing specific handling. Obviously changing it to 6LoWPAN and using this code will confuse everything, because the handling makes only sense for a 6LoWPAN Linux interface which actually also use the 6LoWPAN subsystem. They just using tun as all other to feed a IPv6 stack on a remote microcontroller e.g. openthread, contiki, riot. via slip. (wpantund also allow some radio, foo configuration). > It totally seems like broken behaviour. Maybe it's not even intentional. > Maybe they are just foobar. > They simple don't know what they doing... somebody thought 6LoWPAN need to be 6LoWPAN, but they actually don't use the 6LoWPAN handling inside the kernel. _Except_ they doing out of tree stuff which I don't believe. According to [0] it also works with tun default (I suppsoe raw IPv6), because ifdef. And they should not change it because they don't use in-kernel 6LoWPAN functionality. I really think that this tun/tap feature makes a lot of trouble for some type changes. I probably introduce lowpan_dev pointer to netdevice and then check if it's really a 6LoPWAN interface, a dev->type will not garantuee anymore you have a 6LoWPAN interface. At least in user space it's not possible to have a check if you really have a 6LoWPAN interface. - Alex [0] https://github.com/openthread/wpantund/blob/master/src/util/tunnel.c#L180 [1] https://github.com/reubenhwk/radvd/blob/master/device-linux.c#L75 -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
