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Documentation for the new -addresses flag

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Brian Cunnie
2022-11-09 14:46:46 -08:00
parent 121103ae03
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README.md
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@@ -36,6 +36,33 @@ go get github.com/onsi/gomega/...
~/go/bin/ginkgo -r -p .
```
## Customizing Your Own Nameservers
You can customize your nameserver and address records (NS, A, and AAAA), which
can be particularly useful in an internetless (air-gapped) environment. This can
be done with a combination of the `-nameservers` flag and the `-addresses` flag.
For example, let's say you're the DNS admin for pivotal.io, and you'd like to
have a subdomain, "xip.pivotal.io", that does sslip.io-style lookups (e.g.
"127.0.0.1.xip.pivotal.io" would resolve to "127.0.0.1"). Let's say you have two
servers that you've set aside for this purpose:
- ns-sslip-0.pivotal.io, 10.8.8.8 (IPv4)
- ns-sslip-1.pivotal.io, fc88:: (IPv6)
First, you'd delegate the subdomain "xip.pivotal.io" to those nameservers, and
then you'd run the following command run on each of the two servers:
```bash
go run main.go \
-nameservers=ns-sslip-0.pivotal.io,ns-sslip-1.pivotal.io \
-addresses ns-sslip-0.pivotal.io=10.8.8.8,ns-sslip-1.pivotal.io=fc88::
```
**Note: These nameservers are not general-purpose nameservers; for example,
they won't look up google.com. They are not recursive.** Don't ever configure a
machine to point to these nameservers.
## Directory Structure
- `src/` contains the source code to the DNS server
@@ -56,23 +83,28 @@ go get github.com/onsi/gomega/...
## DNS Server
The DNS server is written in Golang and is not configurable without modifying
the source:
The DNS server is written in Golang and can be configured via flags passed to
the command line.
- it binds to port 53, but can be overridden on the command line with the
`-port`, e.g. `go run main.go -port 9553`
- it only binds to UDP (no TCP, sorry)
- The SOA record is hard-coded except the _MNAME_ (primary master name server)
record, which is set to the queried hostname (e.g. `dig big.apple.com
@ns-aws.nono.io` would return an SOA with an _MNAME_ record of
`big.apple.com.`
- The NS records default to `ns-aws.sslip.io`, `ns-azure.sslip.io`,
`ns-gce.sslip.io`; however, they can be overridden via the `-nameservers`
flag, e.g. `go run main.go -nameservers ns1.example.com,ns2.example.com`). If
you override the name servers, don't forget to set address records for the
new name servers. Exception: `_acme-challenge` records are handled
differently to accommodate the procurement of Let's Encrypt wildcard
certificates; you can read more about that procedure [here](docs/wildcard.md)
new name servers with the `-addresses` flag. Exception: `_acme-challenge`
records are handled differently to accommodate the procurement of Let's
Encrypt wildcard certificates; you can read more about that procedure
[here](docs/wildcard.md)
- You can add custom records via the `-addresses` flag; here's a typical
example where we set an IPv4 record & IPv6 record for a single host:
`-addresses
ns-aws.sslip.io.=52.0.56.137,ns-aws.sslip.io.=2600:1f18:aaf:6900::a`
- The SOA record is hard-coded except the _MNAME_ (primary master name server)
record, which is set to the queried hostname (e.g. `dig big.apple.com
@ns-aws.nono.io` would return an SOA with an _MNAME_ record of
`big.apple.com.`
- The MX records are hard-coded to the queried hostname with a preference of 0,
except `sslip.io` itself, which has custom MX records to enable email
delivery to ProtonMail