I got the R7800 now. I already tried copying the tunnelbroker settings for Barrier Breaker. It didn't work. I have a /48, and tried it, didn't help.
It is configured it as follows:
Network:
config interface 'lan'
option type 'bridge'
option ifname 'eth1'
option proto 'static'
option netmask '255.255.255.0'
option ipaddr '192.168.1.1'
option dns '8.8.8.8 4.4.4.4'
option ip6assign '64'
config interface 'wan'
option ifname 'eth0'
option _orig_ifname 'eth0'
option _orig_bridge 'false'
option proto 'static'
option ipaddr '192.168.0.2'
option netmask '255.255.255.0'
option gateway '192.168.0.1'
# I can't put my cable modem in bridge mode
# but 6in4 works perfectly on a R6250 running tomato.
# It's firewall is completely off and all ports fwd to the R7900
option dns '208.67.222.222 208.67.220.220'
config interface 'wan6'
option _orig_ifname 'eth0'
option _orig_bridge 'false'
option proto '6in4'
option peeraddr 'x.x.x.x' #local PoP for tunnelbroker
option ip6prefix '2001:x:d:x::/64' #prefix per tunnelbroker
option ip6addr '2001:x:c:x::2/64' #Client IPv6 Address per tunnelbroker
# Server IPv6 Address per tunnelbroker doesn't get input anywhere
DHCP:
config dhcp 'lan'
option interface 'lan'
option ra 'server'
option leasetime '4h'
option start '2'
option limit '250'
list dns '2606:4700:4700::1111'
list dns '2620:fe::fe'
option dhcpv6 'server'
option ra_management '1'
Firewall (just to be safe)
config rule
option name 'Allow-Protocol-41-Tunnelbroker'
option src wan
option proto 41
option target ACCEPT
Here's the kicker. I can ping the ubuntu machine on my LAN via http://www.ipv6now.com.au/pingme.php. Some services that depend on IPv6 and are accessed by machines outside of my LAN also report the ubuntu box as up and running. Both of these increase the RX and TX counters in Luci's WAN6 status. When those services don't reach out to my machine, both counters don't increase, no matter what I do (router diag or ubuntu machine curl/ping6.
In diagnostics. IPv6 ping of lede-project.org returns
PING lede-project.org (2a03:b0c0:3:d0::1af1:1): 56 data bytes
ping6: sendto: Network unreachable
In the ubuntu box
$ ping6 ipv6.google.com
PING ipv6.google.com(lax28s10-in-x0e.1e100.net) 56 data bytes
From lax28s10-in-x0e.1e100.net icmp_seq=1 Destination unreachable: No route
Overall I've put over 12 hrs into this. I don't know what else to do. On the R7900 at least it would work for a while before stopping. On this one it just doesn't (for outbound requests, inbound seems to work fine)