From bab0d65514f822097fc7f4b24ad9b8f80621c70c Mon Sep 17 00:00:00 2001
From: Wade Simmons <wsimmons@slack-corp.com>
Date: Tue, 8 Apr 2025 12:02:20 -0400
Subject: [PATCH] populate default Build version if missing

Use the Go module information built into the binary if the Build var
wasn't set during the build.

This means if you install via a specific tag, you get:

    go install github.com/slackhq/nebula/cmd/nebula@v1.9.5

    $ nebula -version
    Version: 1.9.5

And if you install master, you get:

    go install github.com/slackhq/nebula/cmd/nebula@master

    $ nebula -version
    Version: 1.9.5-0.20250408154034-18279ed17b10
---
 cmd/nebula-cert/main.go    | 18 ++++++++++++++++++
 cmd/nebula-service/main.go | 13 +++++++++++++
 cmd/nebula/main.go         | 13 +++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/cmd/nebula-cert/main.go b/cmd/nebula-cert/main.go
index c88626f..82ad2fe 100644
--- a/cmd/nebula-cert/main.go
+++ b/cmd/nebula-cert/main.go
@@ -5,10 +5,28 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"runtime/debug"
+	"strings"
 )
 
+// A version string that can be set with
+//
+//	-ldflags "-X main.Build=SOMEVERSION"
+//
+// at compile-time.
 var Build string
 
+func init() {
+	if Build == "" {
+		info, ok := debug.ReadBuildInfo()
+		if !ok {
+			return
+		}
+
+		Build = strings.TrimPrefix(info.Main.Version, "v")
+	}
+}
+
 type helpError struct {
 	s string
 }
diff --git a/cmd/nebula-service/main.go b/cmd/nebula-service/main.go
index 8d0eaa1..9a17b94 100644
--- a/cmd/nebula-service/main.go
+++ b/cmd/nebula-service/main.go
@@ -4,6 +4,8 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"runtime/debug"
+	"strings"
 
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
@@ -18,6 +20,17 @@ import (
 // at compile-time.
 var Build string
 
+func init() {
+	if Build == "" {
+		info, ok := debug.ReadBuildInfo()
+		if !ok {
+			return
+		}
+
+		Build = strings.TrimPrefix(info.Main.Version, "v")
+	}
+}
+
 func main() {
 	serviceFlag := flag.String("service", "", "Control the system service.")
 	configPath := flag.String("config", "", "Path to either a file or directory to load configuration from")
diff --git a/cmd/nebula/main.go b/cmd/nebula/main.go
index 5cf0a02..ffdc15b 100644
--- a/cmd/nebula/main.go
+++ b/cmd/nebula/main.go
@@ -4,6 +4,8 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"runtime/debug"
+	"strings"
 
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula"
@@ -18,6 +20,17 @@ import (
 // at compile-time.
 var Build string
 
+func init() {
+	if Build == "" {
+		info, ok := debug.ReadBuildInfo()
+		if !ok {
+			return
+		}
+
+		Build = strings.TrimPrefix(info.Main.Version, "v")
+	}
+}
+
 func main() {
 	configPath := flag.String("config", "", "Path to either a file or directory to load configuration from")
 	configTest := flag.Bool("test", false, "Test the config and print the end result. Non zero exit indicates a faulty config")