[Ns-developers] NS-3 promiscuous mode for NetDevice

[Tom Henderson]

Mathieu Lacage wrote:
> hi,
> 
> To summarize a lengthy discussion on irc, gustavo and I agreed that we
> might need to add couple of features to the NetDevice base class to
> support that use-case:
>   - allow the specification of a from address when sending a packet to a
> NetDevice
>   - allow the listener of a NetDevice to get the source and destination
> address of an incoming packet
>   - allow a NetDevice to be put into promiscuous mode
> 
> The details of the API needed to support that are not very complicated
> but they all depend on making a couple of decisions on API stability: it
> is possible to add the above features without breaking existing API by
> adding new methods but doing so would duplicate nearly-similar existing
> methods so, it is also possible to break the existing API and methods to
> make them handle this new case. Gustavo does not want to break the API
> because he does not want to make it harder to migrate from ns-3.1 to
> newer versions. I want to break it because I don't want to introduce
> cruft in our APIs. Tom, craig, opinions ?

I agree with Gustavo's point to look at the specifics, maybe 
side-by-side.  In general, I care about long term sanity of the APIs and 
I probably am less concerned at this moment about stability of an API 
that is public but may be practically internal from a user script level. 
  Also, I have less heartburn over an API change where the fix just 
requires user to look at the documentation and figure out why it didn't 
compile, rather than one that changes behavior subtly.

In this case, I was surprised to look at Gustavo's code and see the 
bridge functionality implemented within a special bridge device rather 
than on top of our usual devices.  Could we instead implement bridging 
as a function on top of existing devices, and would that avoid the need 
to break current API?

I also think that while we are on this exercise, it would be helpful to 
architecturally plan for how we are going to deal with adding VLANs and 
MPLS.

Tom