How to support QUIC with ipfw

[Michael Sierchio]

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.

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