IPv6 dual stack problem

mcchen

My server is running OpenVPN 2.3.6 x64 on Windows 8.1.

I'm trying to create a dual stack OpenVPN Server that will accept connections on both IPv6 and IPv4. I've added "proto udp6" to the server config file and I can connect successfully over IPv6. The problem is that doing this makes the server listen only on IPv6 and not on IPv4. My understanding was that "proto udp6" should create a dual stack configuration and listen on both UDP4 and UDP6. However, I can only seem to do one or the other and not both at the same time.

Is there some other config that I'm missing or is this a bug/limitation in OpenVPN?

Traffic

At this time .. AFAIK .. OpenVPN requires IPv4 End points.

Have you read this:
https://community.openvpn.net/openvpn/wiki/Openvpn23ManPage#lbAQ

Perhaps you would care to post your configs and logs.

mcchen

I'm not doing IPv6 inside the tunnel, only outside the tunnel. From reading this:

https://community.openvpn.net/openvpn/wiki/IPv6

it should be a simple one line config. And it does work, I can connect fine over IPv6. The server just somehow doesn't listen on the IPv4 port simultaneously, which it is supposed to do I think?

Looking at the log, it seems to only configure to listen on IPv6 and I can also see this with netstat.

My config and log posted below.

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#                                               #
# This file is for the server side              #
# of a many-clients <-> one-server              #
# OpenVPN configuration.                        #
#                                               #
# OpenVPN also supports                         #
# single-machine <-> single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#                                               #
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#                                               #
# Comments are preceded with '#' or ';'         #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 14700

# TCP or UDP server?
;proto tcp
;proto udp
proto udp6

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one.  On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca "C:\\Program Files\\OpenVPN\\config\\ca.crt"
cert "C:\\Program Files\\OpenVPN\\config\\server.crt"
key "C:\\Program Files\\OpenVPN\\config\\server.key"  # This file should be kept secret
crl-verify "C:\\Program Files\\OpenVPN\\config\\crl.pem"

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh1024.pem 1024
# Substitute 2048 for 1024 if you are using
# 2048 bit keys. 
dh "C:\\Program Files\\OpenVPN\\config\\dh2048.pem"

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.0 255.255.255.0

# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses.  You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.10.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"
push "route 192.168.147.0 255.255.255.0"

# Dummy default gateway to work around Windows 'unidentified network'/'unknown network'
# also allow windows clients to keep firewall enabled and use openvpn
;route-metric 512
;route 0.0.0.0 0.0.0.0

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
;push "redirect-gateway def1 bypass-dhcp"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
;push "dhcp-option DNS 208.67.222.222"
;push "dhcp-option DNS 208.67.220.220"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
;client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
tls-auth "C:\\Program Files\\OpenVPN\\config\\ta.key" 0 # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
;cipher BF-CBC        # Blowfish (default)
cipher AES-128-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES

# Enable compression on the VPN link.
# If you enable it here, you must also
# enable it in the client config file.
comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nobody

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         openvpn.log
;log-append  openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

Mon Feb 02 20:12:54 2015 OpenVPN 2.3.6 x86_64-w64-mingw32 [SSL (OpenSSL)] [LZO] [PKCS11] [IPv6] built on Dec  1 2014
Mon Feb 02 20:12:54 2015 library versions: OpenSSL 1.0.1j 15 Oct 2014, LZO 2.08
Mon Feb 02 20:12:54 2015 Diffie-Hellman initialized with 2048 bit key
Mon Feb 02 20:12:54 2015 Control Channel Authentication: using 'C:\Program Files\OpenVPN\config\ta.key' as a OpenVPN static key file
Mon Feb 02 20:12:54 2015 Outgoing Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication
Mon Feb 02 20:12:54 2015 Incoming Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication
Mon Feb 02 20:12:54 2015 Socket Buffers: R=[65536->65536] S=[65536->65536]
Mon Feb 02 20:12:54 2015 do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0
Mon Feb 02 20:12:54 2015 open_tun, tt->ipv6=0
Mon Feb 02 20:12:54 2015 TAP-WIN32 device [Local Area Connection 2] opened: \\.\Global\{8377B37A-1C4A-4524-8509-0AFD168476F1}.tap
Mon Feb 02 20:12:54 2015 TAP-Windows Driver Version 9.21 
Mon Feb 02 20:12:54 2015 Notified TAP-Windows driver to set a DHCP IP/netmask of 10.8.0.1/255.255.255.252 on interface {8377B37A-1C4A-4524-8509-0AFD168476F1} [DHCP-serv: 10.8.0.2, lease-time: 31536000]
Mon Feb 02 20:12:54 2015 Sleeping for 10 seconds...
Mon Feb 02 20:13:04 2015 Successful ARP Flush on interface [5] {8377B37A-1C4A-4524-8509-0AFD168476F1}
Mon Feb 02 20:13:04 2015 C:\WINDOWS\system32\route.exe ADD 10.8.0.0 MASK 255.255.255.0 10.8.0.2
Mon Feb 02 20:13:04 2015 ROUTE: CreateIpForwardEntry succeeded with dwForwardMetric1=20 and dwForwardType=4
Mon Feb 02 20:13:04 2015 Route addition via IPAPI succeeded [adaptive]
Mon Feb 02 20:13:04 2015 UDPv6 link local (bound): [undef]
Mon Feb 02 20:13:04 2015 UDPv6 link remote: [undef]
Mon Feb 02 20:13:04 2015 MULTI: multi_init called, r=256 v=256
Mon Feb 02 20:13:04 2015 IFCONFIG POOL: base=10.8.0.4 size=62, ipv6=0
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-vp13,10.8.0.4', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-sp,10.8.0.8', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-n7fhd,10.8.0.12', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-n4,10.8.0.16', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='ad-tablet,10.8.0.20', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='ad-phone,10.8.0.24', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='changeme,10.8.0.28', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='nexus9,10.8.0.32', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-ao725,10.8.0.36', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-tcb2,10.8.0.40', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-n6,10.8.0.44', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 ifconfig_pool_read(), in='gc-n5,10.8.0.48', TODO: IPv6
Mon Feb 02 20:13:04 2015 succeeded -> ifconfig_pool_set()
Mon Feb 02 20:13:04 2015 IFCONFIG POOL LIST
Mon Feb 02 20:13:04 2015 gc-vp13,10.8.0.4
Mon Feb 02 20:13:04 2015 gc-sp,10.8.0.8
Mon Feb 02 20:13:04 2015 gc-n7fhd,10.8.0.12
Mon Feb 02 20:13:04 2015 gc-n4,10.8.0.16
Mon Feb 02 20:13:04 2015 ad-tablet,10.8.0.20
Mon Feb 02 20:13:04 2015 ad-phone,10.8.0.24
Mon Feb 02 20:13:04 2015 changeme,10.8.0.28
Mon Feb 02 20:13:04 2015 nexus9,10.8.0.32
Mon Feb 02 20:13:04 2015 gc-ao725,10.8.0.36
Mon Feb 02 20:13:04 2015 gc-tcb2,10.8.0.40
Mon Feb 02 20:13:04 2015 gc-n6,10.8.0.44
Mon Feb 02 20:13:04 2015 gc-n5,10.8.0.48
Mon Feb 02 20:13:04 2015 Initialization Sequence Completed

Traffic

mcchen wroteI'm not doing IPv6 inside the tunnel, only outside the tunnel. From reading this:

https://community.openvpn.net/openvpn/wiki/IPv6

mcchen wrote'm trying to create a dual stack OpenVPN Server that will accept connections on both IPv6 and IPv4. I've added "proto udp6" to the server config file and I can connect successfully over IPv6. The problem is that doing this makes the server listen only on IPv6 and not on IPv4.

Looks like one or the other for now .. keep up with the source on git 8-)

You can always run another server for IPv4

mcchen

Yeah, after doing some more research I found that OpenVPN only listens on IPv4 and IPv6 simultaneously on certain operating systems (Linux, FreeBSD, and NetBSD). Otherwise, you need to run separate instances. I did that on Windows and it wasn't too much of a pain to configure that and it works fine.

Sounds like there are some major IPv6 changes in the upcoming 2.4 release, so perhaps this will be improved on in the future.