This Caddy module implements a DNSLink resolver that routes requests to different reverse proxies based on the content of _dnslink TXT records.

More information about the DNSLink specification can be found here: https://dnslink.dev

• Looks up _dnslink.<host> TXT records.
• Parses dnslink=<value>.
• Matches the value against configured prefixes.
• Rewrites the request path by prepending the DNSLink value.
• Proxies the request to the configured upstream.
• Caches DNS lookups.

To build Caddy with this module, use xcaddy:

xcaddy build \
    --with github.com/o8is/caddy-dnslink

To build with local changes:

xcaddy build \
    --with github.com/o8is/caddy-dnslink=.

You can use the pre-built image ghcr.io/o8is/caddy-dnslink.

To run the image with your own Caddyfile, mount it as a volume:

docker run -d \
    -p 80:80 \
    -p 443:443 \
    -v $(pwd)/Caddyfile:/etc/caddy/Caddyfile \
    ghcr.io/o8is/caddy-dnslink

To create a custom Docker image with your Caddyfile baked in, you can copy the Caddy binary from the image:

FROM ghcr.io/o8is/caddy-dnslink AS source

FROM caddy:2.7.5

COPY --from=source /usr/bin/caddy /usr/bin/caddy
COPY Caddyfile /etc/caddy/Caddyfile

Then build and run your custom image:

docker build -t my-caddy-dnslink .
docker run -d -p 80:80 -p 443:443 my-caddy-dnslink

If you want to build the image yourself:

docker build -t caddy-dnslink .

{
    order dnslink before reverse_proxy
}

:80 {
    dnslink {
        proxies {
            # prefix [replacement] upstream
            /swarm   /bzz varnish:8080
            /arweave /    ar:4000
            /ipfs         ipfs:8080
        }
        cache_ttl 5m
    }
}

{
    "handler": "dnslink",
    "upstreams": {
        "/swarm": "varnish:8080",
        "/arweave": "ar:4000",
        "/ipfs": "ipfs:8080"
    },
    "replacements": {
        "/swarm": "/bzz",
        "/arweave": "/"
    },
    "cache_ttl": 300000000000
}

1. A request comes in for example.com.
2. The module looks up TXT _dnslink.example.com.
3. Suppose it returns dnslink=/swarm/1234....
4. The module checks if /swarm is in the proxies list.
5. It finds varnish:8080.
6. It rewrites the request path to /bzz/1234... (plus the original path).
7. It proxies the request to varnish:8080.