Unable to establish HE gif0 tunnel

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I updated a border gateway yesterday from a Feb 23 kernel to a May 2
version kernel/world, and lost my connectivity to my gif0 HE tunnel.

I've been using the following in /etc/rc.conf successfully for some time
to establish the tunnel:

# Hurricane Electric v6 tunnel
ipv6_enable="YES"
gif_interfaces="gif0"
gifconfig_gif0="[MY V4 ADDRESS] [HE V4 ADDRESS]"
ifconfig_gif0="inet6 [MY V6 ENDPOINT] [HE V6 ENDPOINT] prefixlen 128"
ipv6_defaultrouter="[HE V6 ENDPOINT]"

# v6 gateway
ipv6_gateway_enable="YES"
ipv6_network_interfaces="internal"
ipv6_prefix_internal="[MY V6 /64 prefix]
rtadvd_interfaces="internal"

Two problems:

* That seems to configure the tunnel, but it appears as 'tentative'.
* the v6 EUI64 address on interface internal is not assigned as before

gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1280
        tunnel inet [MY V4 ADDRESS --> [HE V4 ADDRESS]
        inet6 fe80::211:2fff:fe46:6347%gif0 prefixlen 64 tentative
scopeid 0x8
        inet6 [MY V6 ENDPOINT] --> [HE V6 ENDPOINT] prefixlen 128 tentative
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
        options=1<ACCEPT_REV_ETHIP_VER>

connectivity to HE's v4 endpoint is fine, but I get nada for my own
addresses:
$ ping6 2001:470:a:bd::2
PING6(56=40+8+8 bytes) fe80::202:b3ff:fe97:59f%internal --> 2001:470:a:bd::2
^C
- --- 2001:470:a:bd::2 ping6 statistics ---
3 packets transmitted, 0 packets received, 100.0% packet loss

[root_at_hellfire src]$ ping6 2001:470:a:bd::1
ping6: UDP connect: Can't assign requested address

Destroying and recreating gif0 manually has no effect -- same results.

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