sslip.io is a DNS server that maps specially-crafted DNS A records to IP addresses (e.g. "127-0-0-1.sslip.io" maps to 127.0.0.1). It is similar to, and inspired by, xip.io.

If you'd like to use sslip.io as a service, refer to the website (sslip.io) for more information. This README targets developers; the website targets users.

src/ contains the source code to the DNS server.
ci/ contains the Concourse continuous integration (CI) pipeline and task.
spec/ contains the tests for the production nameservers. To run the tests locally:
```
DOMAIN=sslip.io rspec --format documentation --color spec/
```
k8s/document_root/ contains the HTML content of the sslip.io website. Please run tidy -im -w 120 k8s/document_root/index.html before submitting pull requests.
bosh-release/ contains the BOSH release. BOSH is the mechanism we use to deploy the servers, and the sslip.io BOSH release is a packaging of the DNS server (analogous to a .msi, .pkg, .deb or .rpm)
conf/sslip.io+nono.io.yml (deprecated) contains the PowerDNS's pipe backend's configuration in YAML format for use with BOSH. The pdns_pipe key is the pipe backend script, and pdns_pipe_conf is its configuration file.

DNS Server

The DNS server is written in Golang and is not configurable without modifying the source:

it binds to port 53 (you can't change it)
it only binds to UDP (no TCP, sorry)
if the hostname queried doesn't match, it doesn't return an Answer section; instead, it returns an Authorities section with an SOA.
The SOA record is hard-coded with the exception of the MNAME (primary master name server) record, which is set to the queried hostname (e.g. dig big.apple.com @localhost would have an SOA with an MNAME record of big.apple.com..
The NS records are hard-coded
The MX records are hard-coded with the exception of sslip.io itself, which has custom MX records to enable email delivery.
There are no TXT records, or SRV. If those records (or any other unknown ones) are queried, the server returns no Answers but an Authorities section with the SOA

To run the unit tests:

cd src
go get github.com/onsi/ginkgo/ginkgo
go get github.com/onsi/gomega/...
ginkgo -r .

To run the server on, say, a Mac, you must first start the server:

cd src
go run main.go

And then, in another window, run a query, e.g.:

dig +short 127.0.0.1.sslip.io @localhost

Which will return the expected IP address:

127.0.0.1

You will also see a log message in the server window, similar to the following:

2020/11/22 03:45:44 ::1.62302 TypeA 127.0.0.1.sslip.io. ? 127.0.0.1

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