From 889d83fbdcceadfa2ec6dd64997ed8d0289d5a64 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>
---
 frontend/csi/plugin.go      |  9 +++++++--
 frontend/csi/plugin_test.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/frontend/csi/plugin.go b/frontend/csi/plugin.go
index 2d4bb7a23..6fb866577 100644
--- a/frontend/csi/plugin.go
+++ b/frontend/csi/plugin.go
@@ -5,6 +5,7 @@ package csi
 import (
 	"context"
 	"fmt"
+	"net"
 	"os"
 	"runtime"
 	"strings"
@@ -42,6 +43,10 @@ const (
 	CSIAllInOne   = "allInOne"
 )
 
+func controllerRestURL(host, port string) string {
+	return "https://" + net.JoinHostPort(host, port)
+}
+
 type Plugin struct {
 	orchestrator  core.Orchestrator
 	activatedChan chan struct{}
@@ -262,7 +267,7 @@ func NewNodePlugin(
 		hostname = tridentconfig.ServerCertName
 	}
 
-	restURL := "https://" + hostname + ":" + port
+	restURL := controllerRestURL(hostname, port)
 	p.restClient, err = controllerAPI.CreateTLSRestClient(restURL, caCert, clientCert, clientKey)
 	if err != nil {
 		return nil, err
@@ -354,7 +359,7 @@ func NewAllInOnePlugin(
 			break
 		}
 	}
-	restURL := "https://" + tridentconfig.ServerCertName + ":" + port
+	restURL := controllerRestURL(tridentconfig.ServerCertName, port)
 	p.restClient, err = controllerAPI.CreateTLSRestClient(restURL, caCert, clientCert, clientKey)
 	if err != nil {
 		return nil, err
diff --git a/frontend/csi/plugin_test.go b/frontend/csi/plugin_test.go
index ffde05caa..8ba43481c 100644
--- a/frontend/csi/plugin_test.go
+++ b/frontend/csi/plugin_test.go
@@ -37,6 +37,40 @@ import (
 	"github.com/netapp/trident/utils/osutils"
 )
 
+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",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.Equal(t, tc.expected, controllerRestURL(tc.host, tc.port))
+		})
+	}
+}
+
 func TestNewControllerPlugin(t *testing.T) {
 	testCases := []struct {
 		name          string