From 4a34c7731b2c9a1c0f172ba97fb76796781a37d9 Mon Sep 17 00:00:00 2001
From: Mark Glines <mark@glines.org>
Date: Fri, 27 Mar 2026 12:56:11 -0400
Subject: [PATCH] Use the right syntax for binding to an IPv6 address

If the bind address parses as a valid IPv6 address, put it in brackets, like
"[::]:9997".  Without those brackets, net.Listen() will fail later on, with an
error like:

> listen tcp: address :::9997: too many colons in address

Fixes: #691
---
 config/config.go      |  6 +++++-
 config/config_test.go | 10 ++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/config/config.go b/config/config.go
index 4b104b99f..f960cb9c9 100644
--- a/config/config.go
+++ b/config/config.go
@@ -727,7 +727,11 @@ type APIServer struct {
 
 // BindAddress returns a host:port string.
 func (a *APIServer) BindAddress() string {
-	return fmt.Sprintf("%s:%d", a.Bind, a.Port)
+	bind := a.Bind
+	if ip := net.ParseIP(bind); ip != nil && ip.To4() == nil {
+		bind = fmt.Sprintf("[%s]", bind)
+	}
+	return fmt.Sprintf("%s:%d", bind, a.Port)
 }
 
 // Validate validates the API server config
diff --git a/config/config_test.go b/config/config_test.go
index d6b7e88af..4cd1c819f 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -267,6 +267,16 @@ func TestAPIBindAddress(t *testing.T) {
 	err := cfg.Validate()
 	require.Nil(t, err)
 	require.Equal(t, cfg.BindAddress(), "0.0.0.0:9998")
+
+	cfg.Bind = "::"
+	err = cfg.Validate()
+	require.Nil(t, err)
+	require.Equal(t, cfg.BindAddress(), "[::]:9998")
+
+	cfg.Bind = "1:2:3::4"
+	err = cfg.Validate()
+	require.Nil(t, err)
+	require.Equal(t, cfg.BindAddress(), "[1:2:3::4]:9998")
 }
 
 func TestDatabaseConfig(t *testing.T) {