lib/nat: Add a nat package and service to track mappings on multiple IGDs

lib/nat/registry.go

@@ -0,0 +1,30 @@
+// Copyright (C) 2015 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package nat
+
+import (
+	"time"
+)
+
+type DiscoverFunc func(renewal, timeout time.Duration) []Device
+
+var providers []DiscoverFunc
+
+func Register(provider DiscoverFunc) {
+	providers = append(providers, provider)
+}
+
+func discoverAll(renewal, timeout time.Duration) map[string]Device {
+	nats := make(map[string]Device)
+	for _, discoverFunc := range providers {
+		discoveredNATs := discoverFunc(renewal, timeout)
+		for _, discoveredNAT := range discoveredNATs {
+			nats[discoveredNAT.ID()] = discoveredNAT
+		}
+	}
+	return nats
+}