How to support QUIC with ipfw

[Matt Joras]

Hi Michael,

On Sun, Apr 11, 2021 at 2:27 PM Michael Sierchio <kudzu at tenebras.com> wrote:
>
> On Sun, Apr 11, 2021 at 2:20 PM Matt Joras <mjoras at freebsd.org> wrote:
>
> > Hi Michael,
> >
> > On Sun, Apr 11, 2021, 1:25 PM Michael Sierchio <kudzu at tenebras.com> wrote:
> >
> >> Hi, all.  I noticed my firewall was dropping what seemed to be unsolicited
> >> UDP connections from Google and Facebook, but this turned out to be QUIC
> >> traffic. The traffic can be initiated by the browser (or other supporting
> >> software) or the server.  The problem is that dynamic rules generally
> >> don't
> >> cut it – udp traffic here is predominantly NTP and DNS, and the dynamic
> >> rule lifetime for UDP is very short (3-6 s).  And of course they don't
> >> work
> >> at all for traffic initiated by the server side.
> >>
> >
> > QUIC connections aren't initiated by the server. The browser is initiating
> > these connections. I'm not an ipfw user, the best generic firewall strategy
> > would be to have some sort of flow tracking for ~30s for UDP flows
> > associated with tuples originating on the client for remote port 443. 443
> > will cover the vast majority of Internet cases, as QUIC is only being used
> > at scale for HTTP/3.
> >
> >
> Hej, Matt. Thanks. That's a solution that occurred to me, but it means a
> ton of dynamic rules will get instantiated for ephemeral DNS lookups – 3
> seconds is a very long time for a conversation with a DNS server, because
> it has probably recursed from the root zone all the way to the A record in
> a fraction of that time.  30 seconds is forever – well, since UDP doesn't
> have an analogue to a FIN or RST, the rule doesn't go away when the
> conversation does.

Is it not possible to do the dynamic rule instantiation for select UDP
ports, i.e. 443? That may cause issues if DNS-over-HTTP/3 becomes a
thing, but at least for now it would exclude DNS.

>
> I'll get some metrics on it. Thanks again.
>
>
> --
>
> "Well," Brahmā said, "even after ten thousand explanations, a fool is no
> wiser, but an intelligent person requires only two thousand five hundred."
>
> - The Mahābhārata

Matt Joras