Re: [riot-devel] RIOT+ULAs: no router entry

[smlng]

Hi Alex, and all,

> Am 29.04.2016 um 17:25 schrieb Alexander Aring :
> 
> Routers are indicated by the "forwarding" setting. radvd silent warns
> about that if this isn't set for interfaces with RA advert is on, so far I
> know you need to increase the debug level for that.
> 
> I simple set:
> 
> echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
> 
> this will set forwarding for all interfaces.
> 
> Some code explaining:
> 
> See http://lxr.free-electrons.com/source/net/ipv6/ndisc.c#L838
> 
> this is at function when NS is received, the routeri flag will be set when
> forwarding is enabled.
> 
> Maybe this solves all your current issues. :-)

Yep, thanks - that did the trick. 

I wonder why it isn't sufficient to set 'echo 1 > 
/proc/sys/net/ipv6/conf/lowpan0/forwarding' on that specific lowpan interface? 
I tried it, but `radvd` still complains (debug level 5) that forwarding is 0. 
However, it works by enabling it for all IPv6 interfaces as you suggested.

> 
>> I'm running latest Raspbian with Kernel 'Linux raspberrypi 4.1.19+' and 
>> wpan-tools from github on the RasPi.
>> 
> 
> I would better use bluetooth-next, if possible. With all recent patches
> you could also try to use 6CO in radvd.

mhm, I'm using default Raspbian with RPI-Linux+DTS-overlay 'at86rf233' as it is 
cause a fast and easy setup - and until now, this was sufficient for my test 
cases ...

Best,
 Sebastian

[mail]: s...@mlng.net
[code]: https://github.com/smlng

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Re: [riot-devel] RIOT+ULAs: no router entry

[Alexander Aring]

On Fri, Apr 29, 2016 at 04:58:04PM +0200, smlng wrote:
> Hi Alex,
> hi all,
> 
> over the last days I did some more extensive tests and enabled/added some 
> debug output in RIOT, and I got close to the root cause of the problem. 
> 
> TL;DR: 
> - Linux does not set the router flag in its NAs
> - but it should when `radvd` is running (or `radvd` should enable it). 
> - RIOT behaves correctly, according to RFC-4861 7.2.4.
> 
> 
> 
> Now the slightly longer version; I quickly recap my setup:
> 
> - a RasPi with OpenLabs transceiver, and `radvd` (linux-wpan version from 
> github)
> - Atmel samr21-xpro running RIOT with `gnrc_networking` example 
> (2016.04-branch)
> - `radvd` announces a ULA-prefix (though ULA doesn't matter, could global as 
> well)
> 
> I observed the following behavior:
> 
> - RIOT send RS on boot, `radvd` on RasPi replies with RA (incl. PIO, ABRO, 
> SLLAO)
> - RIOT parse RA, generates IP from prefix, adds NCE for router with router 
> flag set
> - RIOT send NS for RasPi/routers link-local address -> RasPi replies with NA
> - RIOT parses NA, but router flag not set -> unset router flag in NCE of 
> router
> - hence no more router in cache -> no ping or data transfer via 
> non-link-local (e.g. ULA) IPs 
> 
> so my question @alex and @linux-wpan: can I manually set/enable the routers 
> flag for NAs in Linux Kernel? Or somehow _convince_ `radvd` to do so on 
> startup?

Routers are indicated by the "forwarding" setting. radvd silent warns
about that if this isn't set for interfaces with RA advert is on, so far I
know you need to increase the debug level for that.

I simple set:

echo 1 > /proc/sys/net/ipv6/conf/all/forwarding

this will set forwarding for all interfaces.

Some code explaining:

See http://lxr.free-electrons.com/source/net/ipv6/ndisc.c#L838

this is at function when NS is received, the routeri flag will be set when
forwarding is enabled.

Maybe this solves all your current issues. :-)

> I'm running latest Raspbian with Kernel 'Linux raspberrypi 4.1.19+' and 
> wpan-tools from github on the RasPi.
> 

I would better use bluetooth-next, if possible. With all recent patches
you could also try to use 6CO in radvd.

btw: the radvd wants to accept my patches for 6lowpan 6CO stuff, but
basic 6LoWPAN-ND (first short address support for NA/NS) will be added
and short-address handling will not work with RIOT, but that's another
issue...

- Alex
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