I'm having an issue with IPv6 state tracking, I think.

I run a fully dual-stacked environment.
pfSense 2.1-RELEASE acts as the gateway between two subnets (two VLANs, but I don't think that makes any difference here). In IPv4, one subnet ("A") is publicly-routable address space, the other ("B") is RFC1918.
In IPv6, both subnets are publicly-routable address space.
I have a management workstation on subnet A that needs to reach servers in subnet B.

I've added two static routes on the router for subnet A, one IPv4, one IPv6, pointing to pfSense as the next-hop. I've disabled automatic outbound NAT, and modified the three automatically-generated rules to have Destination NOT subnet A, in other words, I don't NAT between subnets A and B, only between B and the outside world (via A). There are no port forwards in place.
On the WAN interface, I have four rules:
    1. allow all IPv6 to WAN interface
    2. allow all IPv4 to WAN interface
    3. allow all IPv6 from A to B
    4. allow all IPv4 from A to B

That's it - the simplest possible configuration I could come up with for this role. (Incidentally, the reason I'm using pfSense at all is because the two routers for subnet A provide non-stateful HA, which makes NAT quite problematic.)

What I see is that when I ssh from A to B using IPv4, everything works fine. The session shows up in the firewall state table as expected, and performs as expected. If I ssh from A to B using IPv6, however, the session connects, I log in, and after a short while, the ssh session stalls. The session does NOT show up in the state table, ever, even while it's still working properly. I can restart the SSH session immediately, and it again will work for a while, failing after ~50 packets have been exchanged.

I've run simultaneous packet captures on the pfSense WAN and LAN interfaces, but they show me nothing of interest. I looked at filter.log, but it's so noisy I didn't get any value out of it yet.

Any ideas or thoughts? How can my session work in the first place without a state table entry, why does it die after ~50-100 packets? Why is only IPv6 affected? Have I missed something fundamental?

--
-Adam Thompson
 [email protected]

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