Add external address tracker object

cmd/syncthing/externaladdr.go

@@ -0,0 +1,107 @@
+// 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 main
+
+import (
+	"fmt"
+	"net"
+	"net/url"
+
+	"github.com/syncthing/syncthing/lib/config"
+)
+
+type externalAddr struct {
+	upnpSvc *upnpSvc
+	cfg     *config.Wrapper
+}
+
+func newExternalAddr(upnpSvc *upnpSvc, cfg *config.Wrapper) *externalAddr {
+	return &externalAddr{
+		upnpSvc: upnpSvc,
+		cfg:     cfg,
+	}
+}
+
+// ExternalAddresses returns a list of addresses that are our best guess for
+// where we are reachable from the outside. As a special case, we may return
+// one or more addresses with an empty IP address (0.0.0.0 or ::) and just
+// port number - this means that the outside address of a NAT gateway should
+// be substituted.
+func (e *externalAddr) ExternalAddresses() []string {
+	var addrs []string
+
+	// Grab our listen addresses from the config. Unspecified ones are passed
+	// on verbatim (to be interpreted by a global discovery server or local
+	// discovery peer). Public addresses are passed on verbatim. Private
+	// addresses are filtered.
+	for _, addrStr := range e.cfg.Options().ListenAddress {
+		addrURL, err := url.Parse(addrStr)
+		if err != nil {
+			l.Infoln("Listen address", addrStr, "is invalid:", err)
+			continue
+		}
+		addr, err := net.ResolveTCPAddr("tcp", addrURL.Host)
+		if err != nil {
+			l.Infoln("Listen address", addrStr, "is invalid:", err)
+			continue
+		}
+
+		if addr.IP == nil || addr.IP.IsUnspecified() {
+			// Address like 0.0.0.0:22000 or [::]:22000 or :22000; include as is.
+			addrs = append(addrs, "tcp://"+addr.String())
+		} else if isPublicIPv4(addr.IP) || isPublicIPv6(addr.IP) {
+			// A public address; include as is.
+			addrs = append(addrs, "tcp://"+addr.String())
+		}
+	}
+
+	// Get an external port mapping from the upnpSvc, if it has one. If so,
+	// add it as another unspecified address.
+	if e.upnpSvc != nil {
+		if port := e.upnpSvc.ExternalPort(); port != 0 {
+			addrs = append(addrs, fmt.Sprintf("tcp://:%d", port))
+		}
+	}
+
+	l.Infoln("External addresses:", addrs)
+
+	return addrs
+}
+
+func isPublicIPv4(ip net.IP) bool {
+	ip = ip.To4()
+	if ip == nil {
+		// Not an IPv4 address (IPv6)
+		return false
+	}
+
+	// IsGlobalUnicast below only checks that it's not link local or
+	// multicast, and we want to exclude private (NAT:ed) addresses as well.
+	rfc1918 := []net.IPNet{
+		{IP: net.IP{10, 0, 0, 0}, Mask: net.IPMask{255, 0, 0, 0}},
+		{IP: net.IP{172, 16, 0, 0}, Mask: net.IPMask{255, 240, 0, 0}},
+		{IP: net.IP{192, 168, 0, 0}, Mask: net.IPMask{255, 255, 0, 0}},
+	}
+	for _, n := range rfc1918 {
+		if n.Contains(ip) {
+			return false
+		}
+	}
+
+	return ip.IsGlobalUnicast()
+}
+
+func isPublicIPv6(ip net.IP) bool {
+	if ip.To4() != nil {
+		// Not an IPv6 address (IPv4)
+		// (To16() returns a v6 mapped v4 address so can't be used to check
+		// that it's an actual v6 address)
+		return false
+	}
+
+	return ip.IsGlobalUnicast()
+}