---
layout: post
title: "Internet sharing (ipv4 and ipv6) on archlinux using dnsmasq"
date: 2014-02-08 20:02:22 +0100
comments: true
categories:
- arch
- dhcp
- ipv6 router advertisement
- network
---

**Update:** Added adhoc wlan network

A guide to connect with a different machine using a ethernet cable for
internet sharing or just transferring files:

1. Install dnsmasq and iproute2

    $ pacman -S dnsmasq iproute2

2. Copy over the configuration files at the end of the article and edit the
   */etc/conf.d/share-internet@\<device\>* to match your network setup. (where
   \<device\> is your network device)

3. Start the sharing service with systemd

   $ sudo systemctl start internet-sharing@<device>.service

After that the other machine can connect via dhcp. It will get an ipv4
address from the **10.20.0.0/24** subnet and a ipv6 address from the **fd21:30c2:dd2f::**
subnet. Your host will be reachable via **10.20.0.1** or **fd21:30c2:dd2f::1**.
Thanks to ipv6 router advertising, an AAAA record for each host is automatically set based on the hostname.
This means if your hostname is *foo*, all members of the network can just connect
to it using the address *foo*. You should disable the share-internet.service, if
you don't need it. Otherwise you might mess up network setups, if you connect to a
network with the device on which the dhcp service is running.

Happy networking!

{% include_code /etc/systemd/system/share-internet.service lang:ini share-internet/share-internet.service %}

{% include_code /etc/dnsmasq.conf lang:ini share-internet/dnsmasq.conf %}

Ethernet to Wlan:

{% include_code /etc/conf.d/share-internet@enp0s25 lang:bash share-internet/share-internet@enp0s25 %}

Wlan to Ethernet:

If you have luck and your wifi driver is capable of the infrastructure mode,
you should take a look at hostadp, in my case I have to create an adhoc network.
To enable the adhoc network:

   $ sudo systemctl enable wireless-adhoc@\<device\>.service

{% include_code /etc/conf.d/share-internet@wlp3s0 lang:bash share-internet/share-internet@wlp3s0 %}

{% include_code /etc/systemd/system/wireless-adhoc@.service lang:ini share-internet/wireless-adhoc@.service %}

{% include_code /etc/wpa_supplicant/wpa_supplicant-adhoc-wlp3s0.conf lang:bash share-internet/wpa_supplicant-adhoc-wlp3s0.conf %}