Re: [v6ops] [OPSEC] [IPv6] Why folks are blocking IPv6 extension headers? (Episode 1000 and counting) (Linux DoS)

[Tom Herbert <[e-mail]>]

On Mon, May 22, 2023 at 10:09 AM Ole Troan
<otroan=[e-mail]> wrote:
>
> Nalini,
>
> >
> > Once bugs are fixed, then we need to consider carefully what BCP around EHs should be done, taking into account various common topologies as well as devices such as proxies and load balancers.  I mention those in particular as what we have found points to those devices in particular as posing problems rather than transit networks.
>
> I look at load balancers as an extension of the application (or network function).

Ole,

If you're talking about a transparent proxy or a transparent stateful
device in the network, I  tend to view those devices as potentially
invasive and harmful to an application as opposed to an extension of
the application. Think of all the problems we've had with stateful
middleboxes and all the hacks we need in networking stacks to work
around them...

> Unless the application had a particular use for a extension header I would not implement it.

So you only run one application in your network? :-) Even if you
polled every user in the network about every application they're
running and found they don't currently use a certain protocol, what
happens the next day when one of your customers wants to use the
banned protocol?

> And that’s with an implementors hat on. Writing custom load-balancers for network services.
> What would you even do with EHs through a load balancer? Provide ALGs for EHs containing addresses inside of them? It would have to be on a case by case basis.

Why would a load balancer care about EH? In the worst case, don't you
just need to parse over the extension headers to find the transport
layer headers for load balancing (note RFC8200 allow intermediate
nodes to not process HBH options).

Tom

>
>
> > Of course, our testing to date is absolute lack of transmission rather than lack of transmission based on EH length or type.  We felt that was the logical first step.
>
> O.