dig txt version.sslip.io returns version

I needed a way of determining the version that a server was running. I
orginally considered a command-line argument, but then I thought, "Why
not create a DNS record for it? That way I can query running servers
without needing to ssh onto the machine."

The TXT record consists of three distinct strings: version, compile
date, and git hash.

```bash
dig txt version.sslip.io +short
    "2.2.1"
    "2021/10/03-15:08:54+0100"
    "6a928eb"
```

bin/make_all

@@ -4,12 +4,18 @@
 #
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
 cd $DIR/../src/sslip.io-dns-server
-
+ldflags="-X xip/xip.VersionSemantic=2.2.0 \
+         -X xip/xip.VersionDate=$(date +%Y/%m/%d-%H:%M:%S%z) \
+         -X xip/xip.VersionGitHash=$(git rev-parse --short HEAD)"
 export GOOS GOARCH
+
 # Bring in ARM64 for my AWS Graviton2 instance
 for GOARCH in amd64 arm64; do
   for GOOS in darwin linux freebsd; do
-    go build -o $DIR/sslip.io-dns-server-$GOOS-$GOARCH main.go
+    go build \
+      -ldflags="$ldflags" \
+      -o $DIR/sslip.io-dns-server-$GOOS-$GOARCH \
+      main.go
   done
 done
 

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

@@ -109,6 +109,10 @@ var _ = Describe("sslip.io-dns-server", func() {
 				"@localhost example.com srv +short",
 				`\A\z`,
 				`TypeSRV example.com. \? nil, SOA example.com. briancunnie.gmail.com. 2021080200 900 900 1800 300\n$`),
+			Entry(`TXT for version.sslip.io is the version number of the xip software (which gets overwritten during linking)`,
+				"@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",
 				`127.0.0.1`,

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

@@ -14,7 +14,7 @@ import (
 )
 
 // DomainCustomization is a value that is returned for a specific query.
-// The map key is the the domain in question, e.g. "sslip.io." (always include trailing dot).
+// The map key is the domain in question, e.g. "sslip.io." (always include trailing dot).
 // For example, when querying for MX records for "sslip.io", return the protonmail servers,
 // but when querying for MX records for generic queries, e.g. "127.0.0.1.sslip.io", return the
 // default (which happens to be no MX records).
@@ -51,12 +51,17 @@ var (
 		{NS: nsGce},
 	}
 
-	mbox, _        = dnsmessage.NewName("briancunnie.gmail.com.")
-	mx1, _         = dnsmessage.NewName("mail.protonmail.ch.")
-	mx2, _         = dnsmessage.NewName("mailsec.protonmail.ch.")
-	dkim1, _       = dnsmessage.NewName("protonmail.domainkey.dw4gykv5i2brtkjglrf34wf6kbxpa5hgtmg2xqopinhgxn5axo73a.domains.proton.ch.")
-	dkim2, _       = dnsmessage.NewName("protonmail2.domainkey.dw4gykv5i2brtkjglrf34wf6kbxpa5hgtmg2xqopinhgxn5axo73a.domains.proton.ch.")
-	dkim3, _       = dnsmessage.NewName("protonmail3.domainkey.dw4gykv5i2brtkjglrf34wf6kbxpa5hgtmg2xqopinhgxn5axo73a.domains.proton.ch.")
+	mbox, _  = dnsmessage.NewName("briancunnie.gmail.com.")
+	mx1, _   = dnsmessage.NewName("mail.protonmail.ch.")
+	mx2, _   = dnsmessage.NewName("mailsec.protonmail.ch.")
+	dkim1, _ = dnsmessage.NewName("protonmail.domainkey.dw4gykv5i2brtkjglrf34wf6kbxpa5hgtmg2xqopinhgxn5axo73a.domains.proton.ch.")
+	dkim2, _ = dnsmessage.NewName("protonmail2.domainkey.dw4gykv5i2brtkjglrf34wf6kbxpa5hgtmg2xqopinhgxn5axo73a.domains.proton.ch.")
+	dkim3, _ = dnsmessage.NewName("protonmail3.domainkey.dw4gykv5i2brtkjglrf34wf6kbxpa5hgtmg2xqopinhgxn5axo73a.domains.proton.ch.")
+
+	VersionSemantic = "dev"
+	VersionDate     = "today"
+	VersionGitHash  = "xxx"
+
 	Customizations = DomainCustomizations{
 		"sslip.io.": {
 			A: []dnsmessage.AResource{
@@ -115,6 +120,13 @@ var (
 				CNAME: dkim3,
 			},
 		},
+		"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"
+			},
+		},
 	}
 )
 

docs/DEVELOPER.md

@@ -6,9 +6,12 @@ they might not make sense unless you're on my workstation.
 ```zsh
 export OLD_VERSION=2.1.2
 export VERSION=2.2.0
-cd ~/go/src/github.com/cunnie/sslip.io
+cd ~/workspace/sslip.io
 git pull -r --autostash
-sed -i '' "s~/$OLD_VERSION/~/$VERSION/~g" k8s/document_root/index.html # update the download instructions on the website
+# update the version number for the TXT record for version.sslip.io
+sed -i '' "s/$OLD_VERSION/$VERSION/g" bin/make_all
+# update the download instructions on the website
+sed -i '' "s~/$OLD_VERSION/~/$VERSION/~g" k8s/document_root/index.html
 cd bosh-release/
 lpass show a # refresh LastPass token
 . ~/workspace/deployments/.envrc # set BOSH auth