Discussion:
dual-stack setup on OpenBSD?
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Harald Dunkel
2017-06-18 08:56:19 UTC
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Hi folks,

I would like to run a single openvpn service in a dual-stack setup on
OpenBSD 6.1.

According to the man page there is a "multihome" support, but it doesn't
work in this case. The logfile on the client shows

Sat Jun 17 15:13:40 2017 OpenVPN 2.4.2 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Jun 17 2017
Sat Jun 17 15:13:40 2017 library versions: OpenSSL 1.0.2l 25 May 2017, LZO 2.08
Enter Private Key Password: ******
Sat Jun 17 15:13:43 2017 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
Sat Jun 17 15:13:43 2017 NOTE: the current --script-security setting may allow this configuration to call user-defined scripts
Sat Jun 17 15:13:43 2017 WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this
Sat Jun 17 15:13:43 2017 TCP/UDP: Preserving recently used remote address: [AF_INET6]2001:db80:13b0:ffff::60:1195
Sat Jun 17 15:13:43 2017 Socket Buffers: R=[212992->212992] S=[212992->212992]
Sat Jun 17 15:13:43 2017 setsockopt(IPV6_V6ONLY=0)
Sat Jun 17 15:13:43 2017 UDP link local (bound): [AF_INET6][undef]:1194
Sat Jun 17 15:13:43 2017 UDP link remote: [AF_INET6]2001:db80:13b0:ffff::60:1195
Sat Jun 17 15:13:44 2017 TCP/UDP: Incoming packet rejected from [AF_INET6]::ffff:5.145.xx.yy:1194[10], expected peer address: [AF_INET6]2001:db80:13b0:ffff::60:1195 (allow this incoming source address/port by removing --remote or adding --float)
Sat Jun 17 15:13:44 2017 or from peer address: [AF_INET]5.145.xx.yy:1195
Sat Jun 17 15:13:48 2017 TCP/UDP: Incoming packet rejected from [AF_INET6]::ffff:5.145.xx.yy:1194[10], expected peer address: [AF_INET6]2001:db80:13b0:ffff::60:1195 (allow this incoming source address/port by removing --remote or adding --float)
Sat Jun 17 15:13:48 2017 or from peer address: [AF_INET]5.145.xx.yy:1195
Sat Jun 17 15:13:51 2017 TCP/UDP: Incoming packet rejected from [AF_INET6]::ffff:5.145.xx.yy:1194[10], expected peer address: [AF_INET6]2001:db80:13b0:ffff::60:1195 (allow this incoming source address/port by removing --remote or adding --float)
Sat Jun 17 15:13:51 2017 or from peer address: [AF_INET]5.145.xx.yy:1195
Sat Jun 17 15:13:54 2017 TCP/UDP: Incoming packet rejected from [AF_INET6]::ffff:5.145.xx.yy:1194[10], expected peer address: [AF_INET6]2001:db80:13b0:ffff::60:1195 (allow this incoming source address/port by removing --remote or adding --float)
Sat Jun 17 15:13:54 2017 or from peer address: [AF_INET]5.145.xx.yy:1195
Sat Jun 17 15:13:56 2017 event_wait : Interrupted system call (code=4)
Sat Jun 17 15:13:56 2017 SIGINT[hard,] received, process exiting

"5.145.xx.yy" is the IPv4 address of the openvpn server.


Is there hope?

Regards
Harri
Gert Doering
2017-06-18 09:38:35 UTC
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Hi,
Post by Harald Dunkel
I would like to run a single openvpn service in a dual-stack setup on
OpenBSD 6.1.
According to the man page there is a "multihome" support, but it doesn't
work in this case. The logfile on the client shows
More interesting than the client log would be the server log...
Post by Harald Dunkel
Sat Jun 17 15:13:44 2017 TCP/UDP: Incoming packet rejected from [AF_INET6]::ffff:5.145.xx.yy:1194[10], expected peer address: [AF_INET6]2001:db80:13b0:ffff::60:1195 (allow this incoming source address/port by removing --remote or adding --float)
This basically means "the server is talking to you from its IPv4 address".
Post by Harald Dunkel
Is there hope?
Maybe, maybe not. I'm afraid, the answer is "no", because your problem
is likely not --multihome but "dual-stack".

OpenVPN's dual-stack handling on the server side today is "open a v6 socket
and make this a dual-stack socket", which some operating systems just do
not support - well, which *OpenBSD* does not support. So to get dual-stack
there, we need to open two listening sockets, which we can't do today.

One possible workaround might be to use pf(4) on the server to setup a
v6/v4 rdr NAT rule and have the firewall provide the "dual-stacking", but
I'm not sure it actually works - never tried.

But let's see the server logs first.

gert
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