[management, client] Add IPv6 overlay support (#5631)

proxy/internal/debug/handler.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"html/template"
 	"maps"
+	"net"
 	"net/http"
 	"slices"
 	"strconv"
@@ -527,13 +528,18 @@ func (h *Handler) handlePingTCP(w http.ResponseWriter, r *http.Request, accountI
 		}
 	}
 
+	network := "tcp"
+	if v := r.URL.Query().Get("ip_version"); v == "4" || v == "6" {
+		network += v
+	}
+
 	ctx, cancel := context.WithTimeout(r.Context(), timeout)
 	defer cancel()
 
-	address := fmt.Sprintf("%s:%d", host, port)
+	address := net.JoinHostPort(host, strconv.Itoa(port))
 	start := time.Now()
 
-	conn, err := client.Dial(ctx, "tcp", address)
+	conn, err := client.Dial(ctx, network, address)
 	if err != nil {
 		h.writeJSON(w, map[string]interface{}{
 			"success": false,
@@ -543,18 +549,22 @@ func (h *Handler) handlePingTCP(w http.ResponseWriter, r *http.Request, accountI
 		})
 		return
 	}
+
+	remote := conn.RemoteAddr().String()
 	if err := conn.Close(); err != nil {
 		h.logger.Debugf("close tcp ping connection: %v", err)
 	}
 
 	latency := time.Since(start)
-	h.writeJSON(w, map[string]interface{}{
+	resp := map[string]interface{}{
 		"success":    true,
 		"host":       host,
 		"port":       port,
+		"remote":     remote,
 		"latency_ms": latency.Milliseconds(),
 		"latency":    formatDuration(latency),
-	})
+	}
+	h.writeJSON(w, resp)
 }
 
 func (h *Handler) handleLogLevel(w http.ResponseWriter, r *http.Request, accountID types.AccountID) {