fix: started with wireguard vpn in a namespace

Misc/wireguard-vpn-namespace.md

@@ -0,0 +1,107 @@
+# Creating a network namespace that uses wireguard vpn
+
+We will setup a network namespace that uses a wireguard vpn.
+IPv4 and IPv6 will be routed through the vpn.
+But it can also be used for IPv4 only or IPv6 only.
+
+Additionally we want to access an service in the namespace from the host.
+
+
+## Create the namespace
+
+```bash
+ip netns add vpn
+```
+
+### Add a loopback interface
+
+```bash
+ip -n vpn addr add 127.0.0.1/8 dev lo
+ip -n vpn addr add ::1/128 dev lo
+ip -n vpn link set lo up
+```
+
+Verify the loopback interface:
+
+```bash
+ip -n vpn addr show lo
+```
+
+## Create a wireguard interface
+
+```bash
+ip link add wg0 type wireguard
+ip link set wg0 netns vpn
+```
+
+### Configure the wireguard interface
+
+With `ip netns exec vpn` we can execute commands in the namespace.
+
+We use a `wg-quick` configuration to configure the wireguard interface.
+
+```bash
+ip netns exec vpn wg setconf wg0 <(wg-quick strip /etc/wireguard/wg0.conf)
+```
+
+### Add addresses
+
+Addresses in the wg-quick format (Address = ...) will be stripped by `wg-quick strip`.
+So they have to be added manually.
+
+```bash
+ip -n vpn address add 10.65.186.143/32 dev wg0
+ip -n vpn address add fd00:dead:beef:cafe::1/128 dev wg0
+```
+
+### Bring up the wireguard interface
+
+```bash
+ip -n vpn link set wg0 up
+```
+
+### Add a default v4 and v6 route
+
+```bash
+ip -n vpn route add default dev wg0
+ip -n vpn -6 route add default dev wg0
+```
+
+### Verify the wireguard interface
+
+```bash
+# show the interface
+ip -n vpn addr show wg0
+ip -n vpn route show
+
+# ping cloudflare
+ip netns exec vpn ping 1.1.1.1
+ip netns exec vpn ping 2606:4700:4700::1111
+```
+
+## Setup resolv.conf to prevent DNS leaks in the namespace
+
+```bash
+mkdir -p /etc/netns/vpn
+echo "nameserver <vpns dns server>" >> /etc/netns/vpn/resolv.conf
+```
+
+### Test DNS Server
+
+```bash
+# verify resolving
+ip netns exec vpn curl -4 https://ipv4.ipleak.net/json/
+ip netns exec vpn curl -6 https://ipv6.ipleak.net/json/
+
+# show which dns server is actually used
+session=$(openssl rand -hex 20)
+random=$(openssl rand -hex 10)
+ip netns exec vpn curl -4 -s "https://$session-$random.ipleak.net/dnsdetection/"
+ip netns exec vpn curl -6 -s "https://$session-$random.ipleak.net/dnsdetection/"
+```
+
+## Create a veth to connect the namespace to the host
+
+We will create veth interface pair to-ns-vpn in the root namespace and from-ns-vpn in the vpn namespace.
+
+```bash