Audit changes.

hub/app.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"vppn/hub/api"
 
+	"git.crumpington.com/lib/go/keyedmutex"
 	"git.crumpington.com/lib/go/webutil"
 )
 
@@ -28,6 +29,9 @@ type App struct {
 	mux      *http.ServeMux
 	tmpl     map[string]*template.Template
 	insecure bool
+
+	// Per-remote address sign-in serialization lock.
+	signInLock keyedmutex.KeyedMutex[string]
 }
 
 func NewApp(conf Config) (*App, error) {
@@ -37,10 +41,11 @@ func NewApp(conf Config) (*App, error) {
 	}
 
 	app := &App{
-		api:      api,
-		mux:      http.NewServeMux(),
-		tmpl:     webutil.ParseTemplateSet(templateFuncs, templateFS),
-		insecure: conf.Insecure,
+		api:        api,
+		mux:        http.NewServeMux(),
+		tmpl:       webutil.ParseTemplateSet(templateFuncs, templateFS),
+		insecure:   conf.Insecure,
+		signInLock: keyedmutex.New[string](),
 	}
 
 	app.registerRoutes()