[Commotion-dev] Preventing Commotion nodes from handing out DHCP?

[Will Hawkins]

You all beat me to it!

I think that Josh made an excellent, easy suggestion. In fact, it is so good and obvious that my planned response now looks silly. 

Since Josh's suggestion will do the trick, feel free to stop reading. But, if you're interested here's how I was going to respond:

I pulled up the function that sets the interface information for a Commotion Plug type interface. That's in /lib/network/commotion.sh. You can view the file through the web here: https://github.com/opentechinstitute/commotion-openwrt/blob/master/commotionfeed/commotionbase/files/lib/network/commotion.sh 

Check down to line 519. We need to change the parameters to udhcpc (stored in the variable $dhcpopts). The existing options (-q -n) tell udhcpc to attempt to obtain a dhcp lease and a) exit immediately after a lease is obtained and b) exit and return failure if a lease cannot be obtained. In your case, the desired behavior is be for udhcpc to continuously ask for a lease until it gets one and then continue to refresh that lease periodically. To do that we just let udhcpc do its default behavior by removing those options entirely. Line 519 becomes
local dhcpopts=""

That's not enough, though. We need to also tell remainder of the function to execute the code for case 0 (which means that udhcpc successfully got a lease) no matter what. The "easiest" way to do that would be to change line 530 to look like:
case "0" in

With these changes, the behavior would be 

1) plug interface comes up,
2) udhcpc asks for an IP address and 
3) the plug interface never acts as a dhcp server. 

In essence, this is exactly what Josh's suggestion accomplishes. I will defer to Josh on the implications for his suggestion w.r.t. to olsrd. There may be some special "stuff" that has to happen for networks on the plug interfaces to get into hna for olsrd. 

I hope that this was helpful and not rambling. Please keep us posted tomorrow if you need help. We'll be around on IRC, etc.

Will


On Tuesday, May 14, 2013 21:37 EDT, Josh King <jking at chambana.net> wrote: 
 
> Hi Preston,
> 
> I do not have a node in front of me at the moment so I can't tell for
> certain (I am referencing my home router, which is running a different
> version of OpenWRT), but you should be able to set this fairly easily
> through the LuCI admin interface. In the admin interface, just go to
> Network->Interfaces->Plug. There should be a dropdown menu for
> "Protocol." Switch it to "DHCP Client," and click "Switch Protocol."
> This will remove the ethernet interface from Commotion's configuration,
> and instead it will just be a normal DHCP interface. Is the node
> intended to advertise that interface as a gateway?
> 
> On 05/14/2013 04:52 PM, Preston Rhea wrote:
> > Hello dev team,
> > 
> > Tomorrow, we are going up the Visitation Rectory steeple in Red Hook
> > to install a co-ordinated distribution layer and Commotion layer
> > co-location site. BKFiber will install some stock 5GHz and 900MHz
> > equipment at the top of the steeple, we'll put two Commotion
> > NanoStations in the middle of the steeple, and all will be connected
> > by a Ubiquiti ToughSwitch.
> > 
> > The issue: we want the Commotion nodes to not interfere with DHCP
> > leases. Those should all be left up to the BKfiber infrastructure - we
> > need to ensure that the Commotion nodes can only receive, never give
> > out, DHCP leases. This is in line with our multi-layer approach, with
> > a Commotion community-managed layer hanging off of a
> > professionally-managed distribution layer. So even if the power goes
> > out, this should always be the case when the power comes back on.
> > 
> > The question: What exactly should I do to make this happen on the
> > Commotion nodes? If you can email a precise solution, it will A: help
> > me since I will be in the steeple all day, and B: help us turn it into
> > nice documentation for the future.
> > 
> > Thanks!
> > 
> > Preston
> > 
> > 
> > --
> > Preston Rhea
> > Program Associate, Open Technology Institute
> > New America Foundation
> > +1-202-570-9770
> > Twitter: @prestonrhea
> > 
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> > 
>