The cursed river that helps your IPv4-only clients exit the underworld to the IPv6-only future

$\color{#789922}\text{>have old ass computer which can only do IPv4}$
$\color{#789922}\text{>maybe am vintage collector and like SGI}$ $\color{#789922}\text{workstations, they are beautiful}$
$\color{#789922}\text{>the world has moved to IPv6, can't browse}$ $\color{#789922}\text{4chan on your old machine}$
$\color{#789922}\text{>old ass computer sends A-record DNS query}$ $\color{#789922}\text{to Styx}$
$\color{#789922}\text{>styx finds glorious AAAA-record, and uses it}$ $\color{#789922}\text{to plot a course out of the underworld}$
$\color{#789922}\text{>styx returns the entry point of this course as a}$ $\color{#789922}\text{valid IPv4 address in your chosen translation subnet}$
$\color{#789922}\text{>tayga ferries packets from the underworld}$ $\color{#789922}\text{to the modern world and back along this course}$
$\color{#789922}\text{>client browses 4chan from IRIX happily}$

• You setup styx as a CLAT (client-side translator), to provide native IPV4 support for your legacy clients in an IPv6 world
• styx provides DNS services to clients over IPv4, and also launches tayga to provide v4->v6 packet translation
• When the client requests an A record, and an AAAA record is available, styx pulls an unused IPv4 out of the translation pool (Default pool is 10.0.0.0/8, but you can use any IPv4 CIDR range) and returns this address to the client
• At the same time, a new mapping is added in tayga which maps this new IPv4 to the result IPv6 address
• Example: you browse to google.com (returns AAAA 2a00:1450:4026:801::200e). styx returns 10.0.0.1 to the client, then adds map 10.0.0.1 2a200:1450:4026:801::200e to tayga.
• This mapping session persists indefinitely, and will be re-used if any subsequent DNS queries result in IPv6 address 2a00:1450:4026:801::200e
• Currently these entries never time out, maybe I should fix that

You need the latest main of tayga as well as this repository.

Instructions on Debian (you may need sudo, idk):

#install dependencies
apt install git golang-go build-essential
#make + install tayga
git clone https://github.com/apalrd/tayga
cd tayga
make
make install
#make + install styx
cd ..
git clone https://github.com/apalrd/styx46
cd styx46
make
#copy config example to running config
cp styx.yaml.example styx.yaml
#edit the config for your setup

#run it
./styx

styx assumes that IPv6 connectivity is already working, possibly including nat64 (default prefix is 64:ff9b::/96). nat64 is not strictly needed if all of your desired services support IPv6 already. You must have an IPv6 default gateway and must not have an IPv4 default gateway (styx will become the local gateway). styx will enable IP forwarding, and proxy ND for each of the addresses behind the CLAT. This may disable accept_ra depending on your distribution, in which case you may need to re-enable it: echo "2" > /proc/sys/net/ipv6/conf/eth0/accept_ra (if your upstream connectivity is via eth0).