From 8c6b2f155a8e047476706219fc22935fef0f2a08 Mon Sep 17 00:00:00 2001
From: Maximilian Rink <github@maxrink.de>
Date: Mon, 13 Jul 2026 09:53:14 +0200
Subject: [PATCH] Fix CSI controller URL for IPv6 service hosts

Build the CSI controller REST endpoint with net.JoinHostPort so IPv6 service hosts from Kubernetes environment variables are bracketed correctly while preserving IPv4 and DNS host behavior.

Add unit coverage for IPv6, IPv4, and DNS controller hosts.

Fixes #1164

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: Maximilian Rink <github@maxrink.de>
---
 main.go      |  3 ++-
 main_test.go | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/main.go b/main.go
index def5d36bc..d8c8701a5 100644
--- a/main.go
+++ b/main.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"math"
 	"math/rand"
+	"net"
 	"os"
 	"os/signal"
 	"path/filepath"
@@ -348,7 +349,7 @@ func controllerRestURL() string {
 	if hostname == "" {
 		hostname = config.ServerCertName
 	}
-	return "https://" + hostname + ":" + port
+	return "https://" + net.JoinHostPort(hostname, port)
 }
 
 func main() {
diff --git a/main_test.go b/main_test.go
index 0610a43ef..121e29c00 100644
--- a/main_test.go
+++ b/main_test.go
@@ -31,6 +31,46 @@ func TestMain(m *testing.M) {
 	os.Exit(m.Run())
 }
 
+func TestControllerRestURL(t *testing.T) {
+	testCases := []struct {
+		name     string
+		host     string
+		port     string
+		expected string
+	}{
+		{
+			name:     "IPv6 address",
+			host:     "2001:db8::1",
+			port:     "34571",
+			expected: "https://[2001:db8::1]:34571",
+		},
+		{
+			name:     "IPv4 address",
+			host:     "192.0.2.10",
+			port:     "34571",
+			expected: "https://192.0.2.10:34571",
+		},
+		{
+			name:     "DNS name",
+			host:     "trident-csi",
+			port:     "34571",
+			expected: "https://trident-csi:34571",
+		},
+		{
+			name:     "defaults",
+			expected: "https://trident-csi:34571",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Setenv("TRIDENT_CSI_SERVICE_HOST", tc.host)
+			t.Setenv("TRIDENT_CSI_SERVICE_PORT", tc.port)
+			assert.Equal(t, tc.expected, controllerRestURL())
+		})
+	}
+}
+
 func TestMain_processCommandLineArgs_QPS(t *testing.T) {
 	type parameters struct {
 		k8sApiQPS         float64