running out of mbufs?

[Marko Zec]

On Monday 08 August 2005 12:32, Andre Oppermann wrote:
> Dave+Seddon wrote:
> > BTW, I'd be interested to know people's thoughts on multiple IP
> > stacks on FreeBSD.  It would be really cool to be able to give a
> > jail it's own IP stack bound to a VLAN interface.  It could then be
> > like a VRF on Cisco.
>
> There is a patch doing that for FreeBSD 4.x.  However while
> interesting it is not the way to go.  You don't want to have multiple
> parallel stacks but just multiple routing tables and interface groups
> one per jail. This gives you the same functionality as Cisco VRF but 
> is far less intrusive to the kernel.


Andre,

the stack virtualization framework for 4.x is based precisely on 
introducing multiple routing tables and interface groups.  In order to 
cleanly implement support for multiple independent interface groups, 
one has to touch both the link and network layers, not forgetting the 
ARP stuff... and in no time you have ended up with a huge and intrusive 
diff against the original network stack code.

So I see no point in pretending we could get such a functionality for 
free, i.e. with only a negligible intrusiveness to the kernel code.  A 
more appropriate question would be whether the potential benefits of 
having multiple stack state instances could outweight the trouble and 
damage associated with the scope of required modifications to the 
kernel code tree.  Only if we could get an affirmative answer to that 
question it would make sense to start thinking / debating on the most 
appropriate methodology to (re)implement the multiple stacks framework.

Cheers,

Marko