[Olsr-dev] [Battlemesh] OLSR src IP bug

Markus Kittenberger (spam-protected)
Sun Apr 3 20:03:29 CEST 2011

On Sun, Apr 3, 2011 at 7:31 PM, Juliusz Chroboczek <(spam-protected)>wrote:

> > but the olsrd routes did not specify the src ip (so it`s up to the kernel
> to
>  > choose *G)

> Neither does Babel, and Babel did apparently not have this issue.
but this "saved" bmx *G, see below what "saved" babel *G

> Babel dumps routes in the kernel by specifying:
>  - dest, plen;
>  - gateway;
>  - interface.
>  I suspect the main difference with OLSR is that it specifies the onlink

flag, asking the kernel not to apply any smarts to the route.  Is that
> correct?
only as side effect

as u have to specify a gateway to use the onlink flag afair*G

i tried with ip route add on the shell, and as soon if i used a gateway it
if i added onlink or not made no further difference (in this case)

and as babel specifies the gateway, even if gateway=destination, source
address for traffic routed with babel routes was choosen "correctly"

> > therefore olsrd will in future activate its srcip routing mode by default
> What if IP addresses change at runtime?
depends on olsrd configuration, if it has fixed interface/originator ip (in
olsrd.conf), it might just not care *G (as it will set its configured adress
itself, so infact/simplified user can`t change it any more *G)

if it uses primary interface address(es) (default), olsrd detects ip addr
changes anyways, via netlink in realtime,..
but yes it would mean rewriting all/many routes,.. (but afair it already
does this, cause an interface that changed primary address is handled as if
it went down and come up again,..)

other approach is (like babel) to rely on the somewhat
unexpected/unexplainable differences in kernel for routes having a gateway,
and hope they do what we want in all conditions,..

i don`t like both options to be honest,. *G

third approach is find out why kernel chooses which address in which
situation, and decide than what to do *GG

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