IPv6 FTP problems

   For some time now, I've had problems getting IPv6 FTP working  
through my IPfilter (4.1) firewall.  I'm not quite sure what I've done  
wrong, but I'm sure a configuration setting could be adjusted to fix it.

   My router is a NetBSD 5.0_STABLE box, and was formerly a 4.0_STABLE  
box, both of which showed this problem for 4.0 and 5.0 boxes behind  
the firewall.  The router/firewall has an IPv6 tunnel out, and runs  
native IPv6 on the networks behind itself.

   When a machine tries to establish an FTP connection over IPv6, it  
works, until it attempts to start a transfer.  This evening, the FTP  
client explained:

229 Entering Extended Passive Mode (|||63935|)
150 Opening BINARY mode data connection for file.gz (208102 bytes).
   0% |                                   |     0        0.00 KiB/s     
--:-- ETA^C

   It never goes anywhere, and I interrupt it.  IPv4 connections to  
the same foreign host for the same file work, however.

   My ipnat.conf sets up mappings for the IPv4 networks I want to be  
able to FTP through the [internal] FTP proxy:

map vlan0 A.B.C.D/24 -> 0/32 proxy port ftp ftp/tcp
map vlan0 172.M.N.X/28 -> 0/32 proxy port ftp ftp/tcp

   Should I do something similar for IPv6?  I'm not NAT'ing IPv6,  
however, so I didn't assume I needed as much.  I think it's just a  
filtering issue.

   Is there some smarts needed to auto-open the returns for FTP data  
transfers for IPv6 through ipfilter?

   Thanks.  All pointers appreciated.

                         - Chris