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nip/k8s/document_root_sslip.io/index.html
Brian Cunnie 8d55c534fc Make way for k-v.io HTML website
To make room for the k-v.io HTML website, we rename the `document_root`
of the sslip.io website to the more explicit `document_root_sslip.io`.
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<h3 id="sslip.io">sslip.io</h3>
<p>Operational Status: <a href="https://ci.nono.io/teams/main/pipelines/sslip.io"><img src=
"https://ci.nono.io/api/v1/pipelines/sslip.io/jobs/dns-servers/badge" alt="ci.nono.io"></a> <sup><a href=
"#status" class="alert-link">[Status]</a></sup></p>
<p><em>sslip.io</em> is a DNS (<a href="https://en.wikipedia.org/wiki/Domain_Name_System">Domain Name System</a>)
service that, when queried with a hostname with an embedded IP address, returns that IP address. It was inspired
by <a href="http://xip.io">xip.io</a>, which was created by <a href="https://github.com/sstephenson">Sam
Stephenson</a>.</p>
<p>Here are some examples:</p>
<table class="table">
<thead>
<tr class="header">
<th>Hostname / URL</th>
<th>IP Address</th>
<th>Notes</th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td>
<a href="https://104.155.144.4.sslip.io">https://104.155.144.4.sslip.io</a>
</td>
<td>104.155.144.4</td>
<td>dot separators, sslip.io website mirror (IPv4)</td>
</tr>
<tr class="even">
<td>
<a href="https://52-0-56-137.sslip.io">https://52-0-56-137.sslip.io</a>
</td>
<td>52.0.56.137</td>
<td>dash separators, sslip.io website mirror (IPv4)</td>
</tr>
<tr class="odd">
<td>www.192.168.0.1.sslip.io</td>
<td>192.168.0.1</td>
<td>subdomain</td>
</tr>
<tr class="even">
<td>www.192-168-0-1.sslip.io</td>
<td>192.168.0.1</td>
<td>subdomain + dashes</td>
</tr>
<tr class="odd">
<td>
<a href="https://www-78-46-204-247.sslip.io">https://www-78-46-204-247.sslip.io</a>
</td>
<td>78.46.204.247</td>
<td>dash prefix, sslip.io website mirror (IPv4)</td>
</tr>
<tr class="even">
<td>--1.sslip.io</td>
<td>::1</td>
<td>IPv6 — always use dashes, never dots</td>
</tr>
<tr class="odd">
<td>
<a href="https://2a01-4f8-c17-b8f--2.sslip.io">https://2a01-4f8-c17-b8f--2.sslip.io</a>
</td>
<td>2a01:4f8:c17:b8f::2</td>
<td>sslip.io website mirror (IPv6)</td>
</tr>
</tbody>
</table>
<h3 id="branding">Branding / White Label / Custom Domains</h3>
<p>sslip.io can be used to brand your own site (you dont need to use the sslip.io domain). For example, say you
own the domain “example.com”, and you want your subdomain, “xip.example.com” to have xip.io-style features. To
accomplish this, set the following three DNS servers as NS records for the subdomain “xip.example.com”</p>
<div class="alert alert-warning" role="alert">
2021-11-27 FYI (for your information), we've switched to using our own nameservers (sslip.io) instead of the
old nono.io nameservers. <b>You don't need to change anything.</b> Don't worry if you're pointing to the old
nameservers—they'll continue to work properly. In fact, under the hood they are the same nameservers; the
change is merely cosmetic: we've created sslip.io DNS records for them.
</div>
<table class="table">
<thead>
<tr class="header">
<th>hostname</th>
<th>IP address</th>
<th>Location</th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td><code>ns-aws.sslip.io.</code></td>
<td>52.0.56.137<br>
2600:1f18:aaf:6900::a</td>
<td>USA</td>
</tr>
<tr class="even">
<td><code>ns-gce.sslip.io.</code></td>
<td>104.155.144.4</td>
<td>USA</td>
</tr>
<tr class="odd">
<td><code>ns-azure.sslip.io.</code></td>
<td>52.187.42.158</td>
<td>Singapore</td>
</tr>
</tbody>
</table>
<p>Lets test it from the command line using <code>dig</code>:</p>
<pre><code>dig @ns-gce.sslip.io. 169-254-169-254.xip.example.com +short</code></pre>
<p>Yields, hopefully: <sup><a href="#timeout" class="alert-link">[connection timed out]</a></sup></p>
<pre><code>169.254.169.254</code></pre>
<h3 id="server">But I Want My Own DNS Server!</h3>
<p>If you want to run your own DNS server, it's simple: you can compile from <a href=
"https://github.com/cunnie/sslip.io/tree/main/bosh-release/src/sslip.io-dns-server">source</a> or you can use one
of our <a href="https://github.com/cunnie/sslip.io/releases">pre-built binaries</a>. In the following example, we
install & run our server within a docker container:</p>
<pre>
docker run -it --rm fedora
curl -L https://github.com/cunnie/sslip.io/releases/download/2.5.2/sslip.io-dns-server-linux-amd64 -o dns-server
chmod +x dns-server
./dns-server 2&gt; dns-server.log &
dnf install -y bind-utils
dig @localhost 127-0-0-1.sslip.io +short # returns "127.0.0.1"</pre>
<h3 id="tls">TLS</h3>
<p>You can acquire TLS certificates for your externally-accessible hosts from certificate authorities (CAs) such
as Let's Encrypt. The easiest mechanism to acquire a certificate would be to use the <a href=
"https://letsencrypt.org/docs/challenge-types/#http-01-challenge">HTTP-01 challenge</a>. It requires, at a
minimum, a web server running on your machine. The <a href="https://caddyserver.com/">Caddy</a> web server is one
of the most popular examples. For example, if you had a webserver with the IP address 52.0.56.137, you could
obtain a TLS certificate for "52.0.56.137.sslip.io", or "www.52.0.56.137.sslip.io", or
"prod.www-52-0-56-137.sslip.io".</p>
<div class="alert alert-warning" role="alert">
<b>2021-02-12 Let's Encrypt Rate Limits</b> If your request for an "sslip.io" certificate is <a href=
"https://letsencrypt.org/docs/rate-limits/">rate-limited</a>, please open a <a href=
"https://github.com/cunnie/sslip.io/issues/new/choose">GitHub issue</a> and we'll request a rate-limit
increase.
</div>
<p>If you have procured a wildcard certificate for your branded / white label / custom sslip.io-style subdomain,
you may install it on your machines for TLS-verified connections.</p>
<div class="alert alert-warning" data-role="alert">
<p>When using a TLS wildcard certificate in conjunction with your branded sslip.io style subdomain, you must
<b>use dashes not dots</b> as separators. For example, if you have the TLS certificate for
<i>*.xip.example.com</i>, you could browse to https://www-52-0-56-137.xip.example.com/ but not
https://www.52.0.56.137.xip.example.com/.</p>
</div>
<p>if you're interested in acquiring a wildcard certificate for your sslip.io domain, e.g.
"*.52-0-56-137.sslip.io", the procedure is described <a href=
"https://github.com/cunnie/sslip.io/blob/main/docs/wildcard.md">here</a>.</p>
<h3 id="experimental">Experimental Features</h3>
<p>Experimental features can change; don't depend on them.</p>
<h4 id="whatismyip">Determining Your External IP Address via DNS Lookup</h4>
<p>You can use sslip.io's DNS servers (<code>ns.sslip.io</code>) to determine your public IP address by querying
the <code>TXT</code> record of <code>ip.sslip.io</code>:</p>
<pre>
dig @ns.sslip.io txt ip.sslip.io +short # sample reply "2607:fb90:464:ae1e:ed60:29c:884c:4b52"
dig @ns.sslip.io txt ip.sslip.io +short -4 # forces IPv4 lookup; sample reply "172.58.35.231"
dig @ns.sslip.io txt ip.sslip.io +short -6 # forces IPv6 lookup; sample reply "2607:fb90:464:ae1e:ed60:29c:884c:4b52"</pre>
<div class="alert alert-warning" role="alert">
When querying for your IP address, always <b>include the sslip.io nameserver</b> (e.g. <i>@ns.sslip.io</i>). If
omitted, you won't get your IP address; instead, you'll get the IP address of your upstream nameserver.
</div>
<p>This feature was inspired by Google's DNS lookup, i.e. <code>dig txt o-o.myaddr.l.google.com @8.8.8.8
+short</code>. There are also popular HTTP-based services for determining your public IP address:</p>
<ul>
<li>
<a href="http://icanhazip.com/">icanhazip.com</a> (<a href=
"https://major.io/2021/06/06/a-new-future-for-icanhazip/">backstory</a>)
</li>
<li>
<a href="http://ipify.org/">ipify.org</a>
</li>
<li>
<a href="http://ip4.me/">ip4.me</a>
</li>
<li>
<a href="http://curlmyip.org/">curlmyip.org</a>
</li>
<li>
<a href="http://ifconfig.co/">ifconfig.co</a>
</li>
<li>
<a href="http://ipinfo.io/">ipinfo.io</a> (commercial)
</li>
</ul>
<p>A big advantage of using DNS queries instead of HTTP queries is bandwidth: querying
<code>ns-aws.sslip.io</code> requires a mere 592 bytes spread over 2 packets; Querying <a href=
"https://icanhazip.com/">https://icanhazip.com/</a> requires 8692 bytes spread out over 34 packets—over 14 times
as much! Admittedly bandwidth usage is a bigger concern for the one hosting the service than the one using the
service.</p><!--
<h4 id="key-value-store"><code>k-v.io</code>: (key-value) read/write/delete TXTs</h4>
<p>We enable special behavior under the <code>k-v.io</code> domain: it can be treated as a key-value store, the
subdomain being the key, and the TXT record being the value.</p>
<p>For example, to write ("put") the value "12.0.1" to the key "macos-version" on the
<code>ns-gce.sslip.io.</code> nameserver, you'd use the following <code>dig</code> command:</p>
<pre><code class="lang-shell">dig @ns-gce.sslip.io. txt put.12.0.1.macos-version.k-v.io</code>.
</pre>
<p>To read ("get") the value back, you'd write the following <code>dig</code> command:</p>
<pre><code class="lang-shell">dig @ns-gce.sslip.io. txt get.macos-version.k-v.io.</code>
</pre>
<p>Since "get" is the default behavior, you don't need to include it in the domain name:</p>
<pre><code class="lang-shell">dig @ns-gce.sslip.io. txt macos-version.k-v.io.</code>
</pre>
<p>Finally, when you're done with the key-value, you can "delete" it:</p>
<pre><code class="lang-shell">dig @ns-gce.sslip.io. txt delete.macos-version.k-v.io.
</code></pre>
<p><code class="lang-shell">Notes:</code></p>
<ul>
<li>Keys are case-insensitive (to accommodate DNS convention). In other words,
<code>KEY.k-v.io</code> and <code>key.k-v.io</code> return the same TXT record.</code></li>
<li>Values are case-sensitive. <code>put.CamelCase.style.k-v.io</code> sets the TXT record to "CamelCase".</li>
<li><code>put</code> requests will return the TXT record being put; i.e. <code>put.hello.world.k-v.io</code>
returns one TXT record of one string, <code>hello</code>.</li>
<li><code>delete</code> requests will return the TXT record being deleted; i.e.
<code>delete.world.k-v.io</code> returns one TXT record of one string, <code>hello</code>. If the TXT record
does not exist, no TXT records will be returned.</li>
<li>Values are limited to 63 bytes to mitigate using the sslip.io servers in a <a href=
"https://us-cert.cisa.gov/ncas/alerts/TA13-088A">DNS amplification attack</a>.
</li>
<li>Values are not persistent: if the server is restarted, all values disappear. Poof.</li>
<li>Values are not consistent. If a value is set in <code>ns-aws.sslip.io</code>, it does not propagate to
<code>ns-gce.sslip.io</code> nor <code>ns-azure.sslip.io</code>.</li>
</ul>
-->
<h4 id="version">Determining The Server Version of Software</h4>You can determine the server version of the
sslip.io software by querying the TXT record of <code>version.status.sslip.io</code>:
<pre>
dig @ns-gce.nono.io version.status.sslip.io txt +short
"2.4.1"
"2022/01/20-08:11:07-0800"
"14ef9a0"
</pre>
<p>The first number, ("2.4.1"), is the version of the sslip.io DNS software, and is most relevant. The other two
numbers are the date compiled and the most recent git hash, but those values can differ across servers due to the
manner in which the software is deployed.</p>
<h4 id="metrics">Server Metrics</h4>You can retrieve metrics from a given server by querying the TXT records of
<code>metrics.status.sslip.io</code>
<pre>
dig @ns-aws.sslip.io metrics.status.sslip.io txt +short
"Uptime (seconds): 13486"
"Key-value store: etcd"
"Blocklist: 2022-02-26 10:54:21-08 2,1"
"Queries: 550488"
"Queries/second: 40.8"
"AnsQueries: 149974"
"AnsQueries/second: 11.1"
"AnsA: 113520"
"AnsAAAA: 7993"
"Source IP TXT: 12"
"Version TXT: 5"
"DNS-01 challenge: 39"
</pre>
<h5>Explanation of Metrics</h5>
<dl>
<dt>Uptime</dt>
<dd>The time since the DNS server has been started, in seconds</dd>
<dt>Key-value store</dt>
<dd>This can be one of two values: "builtin" and "etcd". "builtin" means any changes to key/value are limited
to that specific DNS server. "etcd" means changes are propagated to all servers whose key-value store is
"etcd"</dd>
<dt>Blocklist</dt>
<dd>
The first value ("2022-02-26 10:54:21-08") is the date the blocklist was last downloaded. The following two
numbers are the number of string matches that are blocked (e.g. "raiffeisen" is a string that is blocked if
it appears in the queried hostname) and the number of CIDR matches that are blocked (e.g. "43.134.66.67/24"
is blocked). The blocklist can be found <a href=
"https://github.com/cunnie/sslip.io/blob/main/etc/blocklist.txt">here</a>
</dd>
<dt>Queries</dt>
<dd>The raw number of DNS queries that the server has responded to since starting operation</dd>
<dt>Queries/second</dt>
<dd>The raw number of DNS queries that the server has responded to since starting operation divided by the
number of seconds</dd>
<dt>AnsQueries</dt>
<dd>The number of queries we responded to with at least one record in the answer section. Note that the number
of answered queries is typically a third or fourth the size of the overall queries. This is normal. One reason
for this disparity is that often both the IPv4 (A) and IPv6 (AAAA) records will be checked, but only one reply
will have a record in the answer section . For example, browsing to "127.0.0.1.sslip.io" generates two lookups,
one with an answer (IPv4), and one without (IPv6). Another reason is that lookups follow a chain, e.g. looking
up "127.0.0.1.sslip.io" may generate up to four queries for A records ("1.sslip.io", "0.1.sslip.io",
"0.0.1.sslip.io" and "127.0.0.1.sslip.io"), only the last of which returns a record in the answer section.
Pro-tip: if you want to shave milliseconds off name resolution, use dashes not dots in your hostname (e.g.
"10-9-9-30.sslip.io" instead of "10.9.9.30.sslip.io")</dd>
<dt>AnsQueries/second</dt>
<dd>The raw number of DNS queries that the server has responded to with at least one record in the answer
section since starting operation divided by the number of seconds</dd>
<dt>AnsA</dt>
<dd>The number of responses which included an A (IPv4) record since starting operation (e.g. "dig
127.0.0.1.sslip.io")</dd>
<dt>AnsAAAA</dt>
<dd>The number of responses which included an AAAA (IPv6) record since starting operation (e.g. "dig
--1.sslip.io aaaa")</dd>
<dt>Source IP TXT</dt>
<dd>The number of responses which included a TXT record of the querier's IP address since starting operation
(e.g. "dig @ns.sslip.io ip.sslip.io txt")</dd>
<dt>Version TXT</dt>
<dd>The number of responses which included a TXT record of the DNS's servers version since starting operation
(e.g. "dig @ns-azure.sslip.io version.status.sslip.io txt")</dd>
<dt>DNS-01 Challenge</dt>
<dd>The number of responses which included a delegation of the NS (nameserver). This lookup is used for
generating wildcard certificates from Let's Encrypt. Technically this is not a "successful" query in that we
don't return a record in the ANSWER section, but we do return an NS record in the AUTHORITY section. (e.g. "dig
@ns-gce.sslip.io _acme-challenge.192.168.0.1.sslip.io. soa")</dd>
</dl>
<h3 id="related">Related Services</h3>
<ul>
<li>
<a href="http://xip.io/">xip.io</a>: the inspiration for sslip.io. Sadly, this appears to be no longer
maintained after <a href="https://twitter.com/sstephenson/status/1388146129284603906">Sam Stephenson left
Basecamp</a>.
</li>
<li>
<a href="http://nip.io">nip.io</a>: similar to xip.io, but the PowerDNS backend is written in elegant Python
</li>
<li>
<a href="https://github.com/Corollarium/localtls">localtls</a>: A DNS server + webserver to provide TLS to on
local addresses.
</li>
</ul>
<hr>
<h4 id="footnotes">Footnotes</h4>
<p><a id="status"><sup>[Status]</sup></a> A status of “build failing” rarely means the system is failing. Its
more often an indication that when the servers were last checked (currently every six hours), the CI (continuous
integration) <a href="https://ci.nono.io/teams/main/pipelines/sslip.io">server</a> had difficulty reaching one of
the three sslip.io nameservers. Thats normal. <sup><a href="#timeout" class="alert-link">[connection timed
out]</a></sup></p>
<p><a id="timeout"><sup>[connection timed out]</sup></a></p>
<p>DNS runs over <a href="https://en.wikipedia.org/wiki/User_Datagram_Protocol">UDP</a> which has no guaranteed
delivery, and its not uncommon for the packets to get lost in transmission. DNS clients are programmed to
seamlessly query a different server when that happens. Thats why DNS, by fiat, requires at least two nameservers
(for redundancy). From <a href="https://tools.ietf.org/html/rfc1034">IETF (Internet Engineering Task Force) RFC
(Request for Comment) 1034</a>:</p>
<blockquote>
<p>A given zone will be available from several name servers to insure its availability in spite of host or
communication link failure. By administrative fiat, we require every zone to be available on at least two
servers, and many zones have more redundancy than that.</p>
</blockquote>
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