OpenVPN

Kernel

Device Drivers  --->
    [*] Network device support  --->
        [*] Network core driver support
        <*>   Universal TUN/TAP device driver support

USE flags

Emerge

Install the OpenVPN package:

Also consider installing net-dns/openresolv.

Server side

If this is the first time setting up an openvpn server, we will need to create a PKI (Public Key Infrastructure) from scratch.

Write a server-side openvpn configuration.

tls-server

# server binding port
port 12112

# openvpn protocol, could be tcp / udp / tcp6 / udp6
proto udp

# tun/tap device
dev tun0

# keys configuration, use generated keys
ca example/ca.crt
cert example/example.crt
key example/example.key
dh example/dh2048.pem

# optional tls-auth key to secure identifying
# tls-auth example/ta.key 0

# OpenVPN 'virtual' network infomation, network and mask
server 10.100.0.0 255.255.255.0

# persistent device and key settings
persist-key
persist-tun
ifconfig-pool-persist ipp.txt

# pushing route tables
push "route 192.168.1.0 255.255.255.0"
# push "dhcp-option DNS 192.168.1.1"

# connection
keepalive 10 120
comp-lzo

user nobody
group nobody

# logging
status openvpn-status.log
log /etc/openvpn/openvpn.log
verb 4

Start openvpn server, run

Client side

Copy the necessary key files to client, via a secure way (such as SSH), including

• ca.crt
• client1.crt (in this example)
• client1.key (in this example)
• ta.key (if using tls-auth)

Write a client-side openvpn configuration file:

# specify client-side
client

# tun/tap device
dev tun0

# protocol, according to server
proto udp

# server address
remote address.to.server 12112

# connection
comp-lzo
resolv-retry 30
nobind

# persistent device and keys
persist-key
persist-tun

# keys settings
ca example/ca.crt
cert example/client1.crt
key example/client1.key

# optional tls-auth
# tls-auth exmaple/ta.key 1

# pull dns settings from the server
script-security 2

# These scripts are defaults within the service script. To specify custom scripts,
# use /etc/openvpn/${SVCNAME}- {up,down}.sh as suggested by the service script.
# If you use systemd, SVCNAME will not get set automatically.
# Add `setenv SVCNAME my_svc_name` to set it, where my_svc_name is determined by
# /etc/openvpn/client/my_svc_name.conf
up /etc/openvpn/up.sh
down /etc/openvpn/down.sh

# logging
log /etc/openvpn/openvpn.log
verb 4

To automatically provide username and password, or just username with the password still prompted, add the following option, where auth is the file name containing 1 line with a username, or 2 lines with a username and password.

auth-user-pass /etc/openvpn/auth

To start client, run

OpenRC

systemd

If all goes well, this would give you a working OpenVPN server and client connection.

Syslog

Assuming that syslog is enabled, OpenVPN's output is available, along with other services, on syslog.

Additionally, you can send signal to have it displaying status.

Using OpenRC

Now create your config as /etc/openvpn/EXAMPLE.conf

Using systemd

Due to dependencies server and client operations are separated into two units.

Create your server config as /etc/openvpn/server/EXAMPLE.conf

Create your client config as /etc/openvpn/client/EXAMPLE.conf

You can then create more tunnels by replacing EXAMPLE with more names. Each one has its own configuration and can be stopped and started individually. The default is simply to use openvpn.conf and not symlink the service. You can of course use both methods.

/etc/resolv.conf doesn't get updated

Ensure that the option up and down on the configuration file points to the right path for the script.

Also, dhcpcd is known to overwrite pre-existing file when service is ran (e.g. either automatically called by other script, or manually called thru net-misc/netifrc).

In most cases, the conflict between different network programs can be resolved by installing net-dns/openresolv. The configuration would work out-of-box. Most networking scripts (including Gentoo's OpenVPN up & down script; along with dhcpcd) would regard its presence.

If disabling dhcpcd's resolv.conf update is necessary (most likely not), add the line below to /etc/dhcpcd.conf:

nohook resolv.conf