BOSH release: 2.2.2: ip.sslip.io TXT returns IP

Our documentation was wrong; our homepage said to get the origin IP
address by querying the TXT record of the root, i.e. `dig
@ns-aws.nono.io txt . +short`; however, our code worked differently: it
returned the origin IP when the `.ip` TLD was queried.

The new behavior is that it returns the origin IP when `ip.sslip.io.` is
queried, and the documentation now reflects that behavior.

Also, that behavior is marked "experimental" to give us leeway to
change.

[fixes #11]

bin/make_all

@@ -4,7 +4,7 @@
 #
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
 cd $DIR/../src/sslip.io-dns-server
-ldflags="-X xip/xip.VersionSemantic=2.2.1 \
+ldflags="-X xip/xip.VersionSemantic=2.2.2 \
          -X xip/xip.VersionDate=$(date +%Y/%m/%d-%H:%M:%S%z) \
          -X xip/xip.VersionGitHash=$(git rev-parse --short HEAD)"
 export GOOS GOARCH

bosh-release/.final_builds/packages/sslip.io-dns-server/index.yml

@@ -3,6 +3,10 @@ builds:
     version: 037e9cbd3401e13b101d8345ed35dd9f11e677d1a8ad32f61bd390c732b1f9b6
     blobstore_id: d07828f0-f4ff-4966-7a52-fa25d3eba096
     sha1: sha256:3b5eacdc0776df52ba6a4ecc73b3bc2f3f705cc09c26eecf0547a73405f62e71
+  0abc8073d5bd4d8907e6ca0c3b61cfa8aa4638accfc76b47b5681b0a01a882a5:
+    version: 0abc8073d5bd4d8907e6ca0c3b61cfa8aa4638accfc76b47b5681b0a01a882a5
+    blobstore_id: ceaecfb8-3e3a-4c72-617f-3707fea7d76e
+    sha1: sha256:341159072960b7d64e2cec964061f18bbbf300be5b8f343fe1dd2e6a6584b560
   11ca4e8219df8887655a3aa2c81c3008a2179b9259ca9e735e51aeb1cc874efb:
     version: 11ca4e8219df8887655a3aa2c81c3008a2179b9259ca9e735e51aeb1cc874efb
     blobstore_id: 19c01669-1c49-425d-4563-ed07fc743ef7

bosh-release/packages/sslip.io-dns-server/packaging

@@ -5,9 +5,9 @@ source /var/vcap/packages/golang-1-linux/bosh/compile.env
 mkdir src ${BOSH_INSTALL_TARGET}/bin
 mv sslip.io-dns-server/{go.*,main.go,xip} src/
 cd src/
-ldflags="-X xip/xip.VersionSemantic=2.2.1 \
+ldflags="-X xip/xip.VersionSemantic=2.2.2 \
          -X xip/xip.VersionDate=$(date +%Y/%m/%d-%H:%M:%S%z) \
-         -X xip/xip.VersionGitHash=5227199"
+         -X xip/xip.VersionGitHash=30d2c8a"
 go build \
     -ldflags="$ldflags" \
     -o ${BOSH_INSTALL_TARGET}/bin/sslip.io-dns-server

bosh-release/releases/sslip.io/index.yml

@@ -27,6 +27,8 @@ builds:
     version: 2.2.0
   9d4b45ca-7a96-44c8-61dc-35f5b7f20b97:
     version: 1.2.2
+  a843b20d-5cb5-498a-63d6-28d9fc42b724:
+    version: 2.2.2
   aee53e95-768b-426f-64a1-0d74d458a0a6:
     version: 1.1.2
   d1f0f246-7316-49b9-7620-e9900d9e791e:

bosh-release/releases/sslip.io/sslip.io-2.2.2.yml

@@ -0,0 +1,23 @@
+name: sslip.io
+version: 2.2.2
+commit_hash: 5da6511
+uncommitted_changes: false
+jobs:
+- name: sslip.io-dns-server
+  version: 308acb7c186a042bc2ca4c28b83c9fe7589a64c48ab6a11869c442bcaea8fdf9
+  fingerprint: 308acb7c186a042bc2ca4c28b83c9fe7589a64c48ab6a11869c442bcaea8fdf9
+  sha1: sha256:6ca6f2c11816a82ecb3cf9300ea59369977cbaa7c39eddca35628a7c6b9b5b45
+  packages:
+  - sslip.io-dns-server
+packages:
+- name: golang-1-linux
+  version: 92655dbac2d36906f0d761ab03f2eb6bfa9a22730d8f1591a1acb7a6de875ed4
+  fingerprint: 92655dbac2d36906f0d761ab03f2eb6bfa9a22730d8f1591a1acb7a6de875ed4
+  sha1: sha256:e09c7eb7e88462113fdf2095d1ab0d4b9aed0dfd26cdda19744a47f006f6fe7c
+  dependencies: []
+- name: sslip.io-dns-server
+  version: 0abc8073d5bd4d8907e6ca0c3b61cfa8aa4638accfc76b47b5681b0a01a882a5
+  fingerprint: 0abc8073d5bd4d8907e6ca0c3b61cfa8aa4638accfc76b47b5681b0a01a882a5
+  sha1: sha256:341159072960b7d64e2cec964061f18bbbf300be5b8f343fe1dd2e6a6584b560
+  dependencies:
+  - golang-1-linux

bosh-release/src/sslip.io-dns-server/integration_test.go

@@ -113,11 +113,11 @@ var _ = Describe("sslip.io-dns-server", func() {
 				"@127.0.0.1 version.sslip.io txt +short",
 				`\A"dev"\n"today"\n"xxx"\n\z`,
 				`TypeTXT version.sslip.io. \? \["dev"\], \["today"\], \["xxx"\]`),
-			Entry(`TXT is the querier's IPv4 address and the TLD is "ip."`,
-				"@127.0.0.1 blah.blah.ip txt +short",
+			Entry(`TXT is the querier's IPv4 address and the domain "ip.sslip.io"`,
+				"@127.0.0.1 ip.sslip.io txt +short",
 				`127.0.0.1`,
-				`TypeTXT blah.blah.ip. \? \["127.0.0.1"\]`),
-			Entry(`TXT is the querier's IPv4 address and the TLD is NOT "ip."`,
+				`TypeTXT ip.sslip.io. \? \["127.0.0.1"\]`),
+			Entry(`TXT is the querier's IPv4 address and the domain is NOT "ip.sslip.io"`,
 				"@127.0.0.1 example.com txt +short",
 				`\A\z`,
 				`TypeTXT example.com. \? nil, SOA example.com. briancunnie.gmail.com. 2021080200 900 900 1800 300\n$`),
@@ -128,13 +128,13 @@ var _ = Describe("sslip.io-dns-server", func() {
 			cmd := exec.Command("ping6", "-c", "1", "::1")
 			err := cmd.Run() // if the command succeeds, we have IPv6
 			if err == nil {
-				It("returns a TXT of the querier's IPv6 address when there are no custom/acme records", func() {
-					digCmd = exec.Command("dig", "@::1", "ip.", "txt", "+short")
+				It("returns a TXT of the querier's IPv6 address when querying ip.sslip.io", func() {
+					digCmd = exec.Command("dig", "@::1", "ip.sslip.io", "txt", "+short")
 					digSession, err = Start(digCmd, GinkgoWriter, GinkgoWriter)
 					Expect(err).ToNot(HaveOccurred())
 					Eventually(digSession, 1).Should(Exit(0))
 					Eventually(string(digSession.Out.Contents())).Should(MatchRegexp(`::1`))
-					Eventually(serverSession.Err).Should(Say(`TypeTXT ip\. \? \["::1"\]`))
+					Eventually(serverSession.Err).Should(Say(`TypeTXT ip\.sslip\.io\. \? \["::1"\]`))
 					Expect(digSession).To(Exit())
 				})
 			}

bosh-release/src/sslip.io-dns-server/xip/xip.go

@@ -26,7 +26,9 @@ type DomainCustomization struct {
 	AAAA  []dnsmessage.AAAAResource
 	CNAME dnsmessage.CNAMEResource
 	MX    []dnsmessage.MXResource
-	TXT   []dnsmessage.TXTResource
+	TXT   func(string) ([]dnsmessage.TXTResource, error)
+	// Unlike the other record types, TXT is a function in order to enable more complex behavior
+	// e.g. IP address of the query's source
 }
 
 type DomainCustomizations map[string]DomainCustomization
@@ -41,7 +43,6 @@ var (
 	// https://stackoverflow.com/questions/53497/regular-expression-that-matches-valid-ipv6-addresses
 	ipv6RE           = regexp.MustCompile(`(^|[.-])(([0-9a-fA-F]{1,4}-){7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}-){1,7}-|([0-9a-fA-F]{1,4}-){1,6}-[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}-){1,5}(-[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}-){1,4}(-[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}-){1,3}(-[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}-){1,2}(-[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}-((-[0-9a-fA-F]{1,4}){1,6})|-((-[0-9a-fA-F]{1,4}){1,7}|-)|fe80-(-[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]+|--(ffff(-0{1,4})?-)?((25[0-5]|(2[0-4]|1?[0-9])?[0-9])\.){3}(25[0-5]|(2[0-4]|1?[0-9])?[0-9])|([0-9a-fA-F]{1,4}-){1,4}-((25[0-5]|(2[0-4]|1?[0-9])?[0-9])\.){3}(25[0-5]|(2[0-4]|1?[0-9])?[0-9]))($|[.-])`)
 	dns01ChallengeRE = regexp.MustCompile(`(?i)_acme-challenge\.`)
-	ipDomainRE       = regexp.MustCompile(`(^|\.)ip\.$`)
 	nsAws, _         = dnsmessage.NewName("ns-aws.nono.io.")
 	nsAzure, _       = dnsmessage.NewName("ns-azure.nono.io.")
 	nsGce, _         = dnsmessage.NewName("ns-gce.nono.io.")
@@ -80,12 +81,14 @@ var (
 					MX:   mx2,
 				},
 			},
-			// Although multiple TXT records with multiple strings are allowed, we're sticking
-			// with a multiple TXT records with a single string apiece because that's what ProtonMail requires
-			// and that's what google.com does.
-			TXT: []dnsmessage.TXTResource{
-				{TXT: []string{"protonmail-verification=ce0ca3f5010aa7a2cf8bcc693778338ffde73e26"}}, // ProtonMail verification; don't delete
-				{TXT: []string{"v=spf1 include:_spf.protonmail.ch mx ~all"}},                        // Sender Policy Framework
+			TXT: func(_ string) ([]dnsmessage.TXTResource, error) {
+				// Although multiple TXT records with multiple strings are allowed, we're sticking
+				// with a multiple TXT records with a single string apiece because that's what ProtonMail requires
+				// and that's what google.com does.
+				return []dnsmessage.TXTResource{
+					{TXT: []string{"protonmail-verification=ce0ca3f5010aa7a2cf8bcc693778338ffde73e26"}}, // ProtonMail verification; don't delete
+					{TXT: []string{"v=spf1 include:_spf.protonmail.ch mx ~all"}},
+				}, nil // Sender Policy Framework
 			},
 		},
 		// a global nameserver for sslip.io, a conglomeration of ns-{aws,azure,gce}.nono.io
@@ -120,11 +123,17 @@ var (
 				CNAME: dkim3,
 			},
 		},
+		// Special-purpose TXT records
+		"ip.sslip.io.": {
+			TXT: ipSslipIo,
+		},
 		"version.sslip.io.": {
-			TXT: []dnsmessage.TXTResource{
-				{TXT: []string{VersionSemantic}}, // e.g. "2.2.1'
-				{TXT: []string{VersionDate}},     // e.g. "2021/10/03-15:08:54+0100"
-				{TXT: []string{VersionGitHash}},  // e.g. "9339c0d"
+			TXT: func(_ string) ([]dnsmessage.TXTResource, error) {
+				return []dnsmessage.TXTResource{
+					{TXT: []string{VersionSemantic}}, // e.g. "2.2.1'
+					{TXT: []string{VersionDate}},     // e.g. "2021/10/03-15:08:54+0100"
+					{TXT: []string{VersionGitHash}},  // e.g. "9339c0d"
+				}, nil
 			},
 		},
 	}
@@ -214,8 +223,7 @@ func QueryResponse(queryBytes []byte, sourceAddr net.IP) (responseBytes []byte,
 	return responseBytes, logMessage, nil
 }
 
-func processQuestion(q dnsmessage.Question, response *Response, sourceAddr net.IP) (logMessage string, _ error) {
-	var err error
+func processQuestion(q dnsmessage.Question, response *Response, sourceAddr net.IP) (logMessage string, err error) {
 	logMessage = q.Type.String() + " " + q.Name.String() + " ? "
 	if IsAcmeChallenge(q.Name.String()) { // thanks @NormanR
 		// delegate everything to its stripped (remove "_acme-challenge.") address, e.g.
@@ -431,10 +439,9 @@ func processQuestion(q dnsmessage.Question, response *Response, sourceAddr net.I
 				return logMessage + "nil, NS " + strings.Join(logMessages, ", "), nil
 			}
 			var txts []dnsmessage.TXTResource
-			txts = TXTResources(q.Name.String())
-			if len(txts) == 0 && ipDomainRE.MatchString(q.Name.String()) {
-				// If there are no custom txt resources & TLD is `ip.`, return the source IP addr
-				txts = []dnsmessage.TXTResource{{TXT: []string{sourceAddr.String()}}}
+			txts, err = TXTResources(q.Name.String(), sourceAddr.String())
+			if err != nil {
+				return "", err
 			}
 			response.Answers = append(response.Answers,
 				// 1 or more TXT records via Customizations
@@ -680,11 +687,11 @@ func NSResources(fqdnString string) []dnsmessage.NSResource {
 }
 
 // TXTResources returns TXT records from Customizations
-func TXTResources(fqdnString string) []dnsmessage.TXTResource {
-	if domain, ok := Customizations[strings.ToLower(fqdnString)]; ok {
-		return domain.TXT
+func TXTResources(fqdn, querier string) ([]dnsmessage.TXTResource, error) {
+	if domain, ok := Customizations[strings.ToLower(fqdn)]; ok {
+		return domain.TXT(querier)
 	}
-	return nil
+	return nil, nil
 }
 
 func SOAAuthority(name dnsmessage.Name) (dnsmessage.ResourceHeader, dnsmessage.SOAResource) {
@@ -711,6 +718,11 @@ func SOAResource(name dnsmessage.Name) dnsmessage.SOAResource {
 	}
 }
 
+// when TXT for "ip.sslip.io" is queried, return the IP address of the querier
+func ipSslipIo(sourceIP string) ([]dnsmessage.TXTResource, error) {
+	return []dnsmessage.TXTResource{{TXT: []string{sourceIP}}}, nil
+}
+
 // soaLogMessage returns an easy-to-read string for logging SOA Answers/Authorities
 func soaLogMessage(soaResource dnsmessage.SOAResource) string {
 	return soaResource.NS.String() + " " +

bosh-release/src/sslip.io-dns-server/xip/xip_test.go

@@ -148,30 +148,40 @@ var _ = Describe("Xip", func() {
 	})
 
 	Describe("TXTResources()", func() {
-		It("returns an empty array", func() {
+		It("returns an empty array for a random domain", func() {
 			randomDomain := random8ByteString() + ".com."
-			txts := xip.TXTResources(randomDomain)
+			txts, err := xip.TXTResources(randomDomain, "9.9.9.9")
+			Expect(err).To(Not(HaveOccurred()))
 			Expect(len(txts)).To(Equal(0))
 		})
 		When("queried for the sslip.io domain", func() {
 			It("returns mail-related TXT resources for the sslip.io domain", func() {
 				domain := "ssLip.iO."
-				txts := xip.TXTResources(domain)
+				txts, err := xip.TXTResources(domain, "8.8.8.8")
 				Expect(err).To(Not(HaveOccurred()))
 				Expect(len(txts)).To(Equal(2))
 				Expect(txts[0].TXT[0]).To(MatchRegexp("protonmail-verification="))
 				Expect(txts[1].TXT[0]).To(MatchRegexp("v=spf1"))
 			})
 		})
-		When("a domain has been customized", func() { // Unnecessary, but confirms Golang's behavior for me, a doubting Thomas
+		When("a random domain has been customized w/out any TXT defaults", func() { // Unnecessary, but confirms Golang's behavior for me, a doubting Thomas
 			customizedDomain := random8ByteString() + ".com."
 			xip.Customizations[customizedDomain] = xip.DomainCustomization{}
 			It("returns no TXT resources", func() {
-				txts := xip.TXTResources(customizedDomain)
+				txts, err := xip.TXTResources(customizedDomain, "1.1.1.1")
+				Expect(err).To(Not(HaveOccurred()))
 				Expect(len(txts)).To(Equal(0))
 			})
 			delete(xip.Customizations, customizedDomain) // clean-up
 		})
+		When(`the domain "ip.sslip.io" is queried`, func() {
+			It("returns the IP address of the querier", func() {
+				txts, err := xip.TXTResources("ip.sslip.io.", "1.1.1.1")
+				Expect(err).To(Not(HaveOccurred()))
+				Expect(len(txts)).To(Equal(1))
+				Expect(txts[0].TXT[0]).To(MatchRegexp("^1.1.1.1$"))
+			})
+		})
 	})
 
 	Describe("NameToA()", func() {

docs/DEVELOPER.md

@@ -4,16 +4,18 @@ These instructions are meant primarily for me when deploying a new BOSH release;
 they might not make sense unless you're on my workstation.
 
 ```zsh
-export OLD_VERSION=2.2.0
-export VERSION=2.2.1
+export OLD_VERSION=2.2.1
+export VERSION=2.2.2
 cd ~/workspace/sslip.io
 git pull -r --autostash
 # update the version number for the TXT record for version.sslip.io
 sed -i '' "s/$OLD_VERSION/$VERSION/g" \
   bin/make_all \
   bosh-release/packages/sslip.io-dns-server/packaging
 # update the download instructions on the website
-sed -i '' "s~/$OLD_VERSION/~/$VERSION/~g" k8s/document_root/index.html
+sed -i '' "s~/$OLD_VERSION/~/$VERSION/~g" \
+  k8s/document_root/index.html \
+  k8s/Dockerfile-sslip.io-dns-server
 # update the git hash for the TXT record for version.sslip.io for BOSH release
 sed -i '' "s/VersionGitHash=[0-9a-fA-F]*/VersionGitHash=$(git rev-parse --short HEAD)/g" \
   bosh-release/packages/sslip.io-dns-server/packaging
@@ -44,12 +46,12 @@ dig a _Acme-ChallengE.127-0-0-1.sslip.io @$IP | grep "^127"
 echo "127-0-0-1.sslip.io.	604800	IN	A	127.0.0.1"
 dig +short sSlIp.Io
 echo 78.46.204.247
-dig @ns-aws.nono.io txt . +short | tr -d '"'
+dig @$IP txt ip.sslip.io +short | tr -d '"'
 curl curlmyip.org; echo
 dig @$IP txt version.sslip.io +short | grep $VERSION
 echo "\"$VERSION\""
 git add -p
-git ci -vm"BOSH release: 2.2.0: TXT records return IP addrs"
+git ci -vm"BOSH release: 2.2.2: TXT records return IP addrs"
 bosh upload-blobs
 bosh create-release \
   --final \

k8s/Dockerfile-sslip.io-dns-server

@@ -26,7 +26,7 @@ LABEL maintainer="brian.cunnie@gmail.com"
 RUN apk update && apk add bind-tools
 
 ARG TARGETARCH # amd64, arm64 (so I can run on AWS graviton2)
-RUN wget https://github.com/cunnie/sslip.io/releases/download/2.2.1/sslip.io-dns-server-linux-$TARGETARCH \
+RUN wget https://github.com/cunnie/sslip.io/releases/download/2.2.2/sslip.io-dns-server-linux-$TARGETARCH \
     -O /usr/sbin/sslip.io-dns-server; \
   chmod 755 /usr/sbin/sslip.io-dns-server
 

k8s/document_root/index.html

@@ -50,7 +50,7 @@ <h3 id="sslip.io">sslip.io</h3>
       "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
+      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>
       <div class="alert alert-success" role="alert">
@@ -160,7 +160,7 @@ <h3 id="server">But I Want My Own DNS Server!</h3>
       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/2.2.1/sslip.io-dns-server-linux-amd64 -o dns-server
+curl -L https://github.com/cunnie/sslip.io/releases/download/2.2.2/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
@@ -190,15 +190,21 @@ <h3 id="tls">TLS</h3>
       <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/master/docs/wildcard.md">here</a>.</p>
-      <h3 id="whatismyip">Determining Your External IP Address via DNS Lookup</h3>
+      <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-aws.nono.io</code>, <code>ns-azure.nono.io</code>,
-      <code>ns-gce.nono.io</code>) to determine your public IP address by querying the <code>TXT</code> record of the
-      root domain. If you're curious about your public IPv6 address, use the DNS server <code>ns-aws.nono.io</code>,
-      for it has both IPv4 and IPv6 addresses:</p>
+      <code>ns-gce.nono.io</code>) to determine your public IP address by querying the <code>TXT</code> record of
+      <code>ip.sslip.io</code>. If you're curious about your public IPv6 address, use the DNS server
+      <code>ns-aws.nono.io</code>, for it has both IPv4 and IPv6 addresses:</p>
       <pre>
-dig @ns-aws.nono.io txt . +short    # sample reply "2607:fb90:464:ae1e:ed60:29c:884c:4b52"
-dig @ns-aws.nono.io txt . +short -4 # forces IPv4 lookup; sample reply "172.58.35.231"
-dig @ns-aws.nono.io txt . +short -6 # forces IPv6 lookup; sample reply "2607:fb90:464:ae1e:ed60:29c:884c:4b52"</pre>
+dig @ns-aws.nono.io txt ip.sslip.io +short    # sample reply "2607:fb90:464:ae1e:ed60:29c:884c:4b52"
+dig @ns-aws.nono.io txt ip.sslip.io +short -4 # forces IPv4 lookup; sample reply "172.58.35.231"
+dig @ns-aws.nono.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-aws.nono.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>
@@ -227,6 +233,17 @@ <h3 id="whatismyip">Determining Your External IP Address via DNS Lookup</h3>
       "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="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.sslip.io</code>:
+      <pre>
+dig @ns-aws.nono.io txt version.sslip.io +short
+            "2.2.1"
+            "2021/10/06-05:17:18-0700"
+            "7bef649"
+</pre>
+      <p>The first number, ("2.2.1"), 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>
       <h3 id="related">Related Services</h3>
       <ul>
         <li>