openvpn/TODO.IPv6

known issues for IPv6 payload support in OpenVPN
-----------------------------------------------

1.) "--topology subnet" doesn't work together with IPv6 payload on FreeBSD
    (verified for FreeBSD server, Linux/ifconfig client, problems 
    with ICMP6 neighbor solicitations from BSD not being answered by Linux)

2.) NetBSD IPv6 support doesn't work
    ("connected" route is not auto-created, "route-ipv6" adding fails)

    * fixed, 3.1.10 *

3.) route deletion for IPv6 routes is not yet done

    * fixed for configured routes, 3.1.10 *
    * missing for manual-ifconfig-connected (NetBSD, Darwin, Win32)

4.) do "ifconfig tun0 inet6 unplumb"  or "ifconfig tun0 destroy" for
    Solaris, *BSD, ... at program termination time, to clean up leftovers
    (unless tunnel persistance is desired).

    For Solaris, only the "ipv6 tun0" is affected, for the *BSDs all tun0
    stay around.

4a.) deconfigure IPv6 on tun interface on session termination, otherwise
    one could end up with something like this (on NetBSD):

tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1500
        inet 10.9.0.18 -> 10.9.0.17 netmask 0xffffffff
        inet6 fe80::a00:20ff:fece:d299%tun0 ->  prefixlen 64 scopeid 0x3
        inet6 2001:608:4:eff::2000:3 ->  prefixlen 64
        inet6 2001:608:4:eff::1:3 ->  prefixlen 64

    (pool was changed, previous address still active on tun0, breakage)

    * semi-fixed for NetBSD, 28.2.10, always do tun0 destroy / tun0 create
      before actual ifconfig -- tunnel still lingers after OpenVPN quits

4b.) verify this - on FreeBSD, tun0 is auto-destroyed if created by
     opening /dev/tun (and lingers if created by "ifconfig tun0 create")

     -> use for persistant tunnels on not-linux?

5.) add new option "ifconfig-ipv6-push"
    (per-client static IPv6 assignment, -> radiusplugin, etc)

    * implemented, 14.1.10 *

6.) add new option "route-ipv6-gateway"

7.) add "full" gateway handling for IPv6 in route.c 
    (right now, the routes are just sent down the tun interface, if the
    operating system in questions supports that, without care for the
    gateway address - which does not work for gateways that are supposed
    to point elsewhere.  Also, it doesn't work for TAP interfaces.

8.) full IPv6 support for TAP interfaces 
    (main issue should be routes+gateway - and testing :-) )

    test 2010/09/24: TAP itself works on linux/ifconfig+iproute2, but 
    route-via-tap doesn't work at all (route points to "tap0" which fails)

17:51:14.075412 fe:ab:6e:c5:53:71 > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: 2001:608:4:a053::1:0 > ff02::1:ff00:1: ICMP6, neighbor solicitation, who has 2001:608:4:a001::1, length 32

    how is iroute-via-tap supposed to work??

9.) verify that iroute-ipv6 and route-ipv6 interact in the same way as
    documented for iroute/route:

    A's subnet, OpenVPN must push this route to all clients
    EXCEPT for A, since the subnet is already owned by A.
    OpenVPN accomplishes this by not
    not pushing a route to a client
    if it matches one of the client's iroutes.

10.) extend "ifconfig-ipv6" to handle specification of /netbits, pushing
    of /netbits, and correctly ifconfig'ing this
    (default, if not specified: /64)

11.) do not add ipv6-routes if tun-ipv6 is not set - complain instead

     * done * 12.1.10

12.) handle incoming [::] and [fe80:...] packets in tun-p2mp MULTI mode
     (most likely those are DAD packets)
     silently ignore DAD?  
        Or accept-and-forward iff (multicast && client2client)?
     handle NS/NA

13.) from Martin List-Petersen:

	One thing, and I guess this requires modifications in
	network-manager-openvpn: It also works, BUT ignores "push
	route-ipv6-gateway" and "push route-ipv6 ...." (obviously routes pushed
	from the server) entirely.

14.) from ##openvpn-discussion:

	new features should be #ifdef'ed

	(check whether this is feasible at all)

15.) IPv6 related environment variables

	- document all of them in openvpn.8
	- make sure that all existing IPv4 stuff has IPv6 counterparts

16.) OpenBSD
	- implement ifconfig/route for IPv6
	- revert ifconfig/open_tun order to "normal" (separate commit!!!)
	  (openvpn-devel, Subject: OpenBSD)
	- test

17.) client-option (Elwood)
	- ignore-v6-push-options yes/no
	- ignore-v6-route-push  ("as for IPv4 routes")

18.) fail-save?  "what if 'ip -6 addr add' fails" -> fail, or fallback to v4?
	(-> recomment setting "ignore-v6-push-options yes")

19.) safety check: if connecting over IPv6 (v6 transport) and the pushed
     route-ipv6 network encompasses the server IPv6 address, make sure 
     we at least log a warning (until we can fiddle with external routing
     to make this work correctly).

20.) show "route add" / "route delete" commands for IPv6 in log file
     (we show the "ifconfig" commands, so why not the routes?)

     2010-08-07: this is a null-feature - it's already there, but with
                 different debug level (M_INFO vs. D_ROUTE) so user 
                 didn't notice

21.) enable ipv6-only server operations
      - decouple ipv6 pool handling from ipv4 pool
      - make sure Rest of OpenVPN doesn't assume "there will always be IPv4"

22.) implement --learn-address for IPv6

23.) FreeBSD 8 seems to require explicit setting of the "ifconfig" IPv6
     route, while FreeBSD 6+7 don't --> more testing, and code fix

     workaround for the time being: just add

	server-ipv6 2001:608:4:a051::/64
	route-ipv6 2001:608:4:a051::/64

    to the config

    (problem + workaround applies both to tun and tap style devices)