multi: add automatic network address discovery.

This discovers the network address(es) of the daemon
through connected outbound peers. The address(es)
discovered are advertised to subsequent connecting peers.

addrmgr/addrmanager.go

@@ -1013,19 +1013,44 @@ func (a *AddrManager) AddLocalAddress(na *wire.NetAddress, priority AddressPrior
 	return nil
 }
 
+// HasLocalAddress asserts if the manager has the provided local address.
+func (a *AddrManager) HasLocalAddress(na *wire.NetAddress) bool {
+	key := NetAddressKey(na)
+	a.lamtx.Lock()
+	_, ok := a.localAddresses[key]
+	a.lamtx.Unlock()
+	return ok
+}
+
+const (
+	// Unreachable represents a publicly unreachable connection state
+	// between two addresses.
+	Unreachable = 0
+
+	// Default represents the default connection state between
+	// two addresses.
+	Default = iota
+
+	// Teredo represents a connection state between two RFC4380 addresses.
+	Teredo
+
+	// Ipv6Weak represents a weak IPV6 connection state between two
+	// addresses.
+	Ipv6Weak
+
+	// Ipv4 represents an IPV4 connection state between two addreses.
+	Ipv4
+
+	// Ipv6Strong represents a connection state between two IPV6 addresses.
+	Ipv6Strong
+
+	// Private reprsents a connection state connect between two Tor addresses.
+	Private
+)
+
 // getReachabilityFrom returns the relative reachability of the provided local
 // address to the provided remote address.
 func getReachabilityFrom(localAddr, remoteAddr *wire.NetAddress) int {
-	const (
-		Unreachable = 0
-		Default     = iota
-		Teredo
-		Ipv6Weak
-		Ipv4
-		Ipv6Strong
-		Private
-	)
-
 	if !IsRoutable(remoteAddr) {
 		return Unreachable
 	}
@@ -1130,6 +1155,15 @@ func (a *AddrManager) GetBestLocalAddress(remoteAddr *wire.NetAddress) *wire.Net
 	return bestAddress
 }
 
+// IsPeerNaValid asserts if the the provided local address is routable
+// and reachable from the peer that suggested it.
+func (a *AddrManager) IsPeerNaValid(localAddr, remoteAddr *wire.NetAddress) bool {
+	net := getNetwork(localAddr)
+	reach := getReachabilityFrom(localAddr, remoteAddr)
+	return (net == IPv4Address && reach == Ipv4) || (net == IPv6Address &&
+		(reach == Ipv6Weak || reach == Ipv6Strong || reach == Teredo))
+}
+
 // New returns a new Decred address manager.
 // Use Start to begin processing asynchronous address updates.
 // The address manager uses lookupFunc for necessary DNS lookups.

addrmgr/network.go

@@ -118,6 +118,33 @@ func isOnionCatTor(na *wire.NetAddress) bool {
 	return onionCatNet.Contains(na.IP)
 }
 
+// NetworkAddress type is used to classify a network address.
+type NetworkAddress int
+
+const (
+	LocalAddress NetworkAddress = iota
+	IPv4Address
+	IPv6Address
+	OnionAddress
+)
+
+// getNetwork returns the network address type of the provided network address.
+func getNetwork(na *wire.NetAddress) NetworkAddress {
+	switch {
+	case isLocal(na):
+		return LocalAddress
+
+	case isIPv4(na):
+		return IPv4Address
+
+	case isOnionCatTor(na):
+		return OnionAddress
+
+	default:
+		return IPv6Address
+	}
+}
+
 // isRFC1918 returns whether or not the passed address is part of the IPv4
 // private network address space as defined by RFC1918 (10.0.0.0/8,
 // 172.16.0.0/12, or 192.168.0.0/16).

config.go

@@ -129,6 +129,7 @@ type config struct {
 	OnionProxyUser       string        `long:"onionuser" description:"Username for onion proxy server"`
 	OnionProxyPass       string        `long:"onionpass" default-mask:"-" description:"Password for onion proxy server"`
 	NoOnion              bool          `long:"noonion" description:"Disable connecting to tor hidden services"`
+	NoDiscoverIP         bool          `long:"nodiscoverip" description:"Disable automatic network address discovery"`
 	TorIsolation         bool          `long:"torisolation" description:"Enable Tor stream isolation by randomizing user credentials for each connection."`
 	TestNet              bool          `long:"testnet" description:"Use the test network"`
 	SimNet               bool          `long:"simnet" description:"Use the simulation test network"`

server.go

@@ -128,6 +128,11 @@ type peerState struct {
 	persistentPeers map[int32]*serverPeer
 	banned          map[string]time.Time
 	outboundGroups  map[string]int
+
+	// suggestions represents public network address suggestions from outbound
+	// peers.
+	suggestions    map[addrmgr.NetworkAddress]map[string]int32
+	suggestionsMtx sync.Mutex
 }
 
 // ConnectionsWithIP returns the number of connections with the given IP.
@@ -177,6 +182,46 @@ func (ps *peerState) forAllPeers(closure func(sp *serverPeer)) {
 	ps.forAllOutboundPeers(closure)
 }
 
+// ResolveLocalAddress picks the best suggested network address from available
+// options, per the network interface key provided. The best suggestion, if
+// found, is added as a local address.
+func (ps *peerState) ResolveLocalAddress(netKey addrmgr.NetworkAddress, addrMgr *addrmgr.AddrManager, services wire.ServiceFlag, port uint16) {
+	ps.suggestionsMtx.Lock()
+	count := len(ps.suggestions[netKey])
+	if count == 0 {
+		ps.suggestionsMtx.Unlock()
+		return
+	}
+
+	var bestSuggestion string
+	var bestTally int32
+	for suggestion, tally := range ps.suggestions[netKey] {
+		switch {
+		case bestSuggestion == "", tally > bestTally:
+			bestSuggestion = suggestion
+			bestTally = tally
+		}
+	}
+	ps.suggestionsMtx.Unlock()
+
+	// A valid best address suggestion must have at least two outbound peers
+	// concluding on the same result.
+	if bestTally < 2 {
+		return
+	}
+
+	na, err := addrMgr.HostToNetAddress(bestSuggestion, port, services)
+	if err != nil {
+		amgrLog.Errorf("unable to generate network address using host %v: "+
+			"%v", bestSuggestion, err)
+		return
+	}
+
+	if !addrMgr.HasLocalAddress(na) {
+		addrMgr.AddLocalAddress(na, addrmgr.ManualPrio)
+	}
+}
+
 // server provides a Decred server for handling communications to and from
 // Decred peers.
 type server struct {
@@ -252,6 +297,10 @@ type serverPeer struct {
 	// The following chans are used to sync blockmanager and server.
 	txProcessed    chan struct{}
 	blockProcessed chan struct{}
+
+	// peerNa is network address of the peer connected to.
+	peerNa    *wire.NetAddress
+	peerNaMtx sync.Mutex
 }
 
 // newServerPeer returns a new serverPeer instance. The peer needs to be set by
@@ -440,6 +489,12 @@ func (sp *serverPeer) OnVersion(p *peer.Peer, msg *wire.MsgVersion) *wire.MsgRej
 		addrManager.Good(remoteAddr)
 	}
 
+	if !sp.Inbound() {
+		sp.peerNaMtx.Lock()
+		sp.peerNa = &msg.AddrYou
+		sp.peerNaMtx.Unlock()
+	}
+
 	// Choose whether or not to relay transactions.
 	sp.setDisableRelayTx(msg.DisableRelayTx)
 
@@ -1359,6 +1414,68 @@ func (s *server) handleAddPeerMsg(state *peerState, sp *serverPeer) bool {
 		} else {
 			state.outboundPeers[sp.ID()] = sp
 		}
+
+		// Fetch the suggested public ip from the outbound peer if
+		// there are no prevailing conditions to disable automatic
+		// network address discovery.
+		//
+		// The conditions to disable automatic network address
+		// discovery are:
+		//	- If there is a proxy set (--proxy, --onion).
+		//	- If automatic network address discovery is explicitly
+		//		disabled (--nodiscoverip).
+		//	- If there is an external ip explicitly set (--externalip).
+		//	- If listening has been disabled (--nolisten, listen
+		//	disabled because of --connect, etc).
+		//	- If Universal Plug and Play is enabled (--upnp).
+		//	- If the active network is simnet or regnet.
+		if (cfg.Proxy != "" || cfg.OnionProxy != "") ||
+			cfg.NoDiscoverIP || len(cfg.ExternalIPs) > 0 ||
+			(cfg.DisableListen || len(cfg.Listeners) == 0) || cfg.Upnp ||
+			activeNetParams.Name == simNetParams.Name ||
+			activeNetParams.Name == regNetParams.Name {
+			return true
+		}
+
+		sp.peerNaMtx.Lock()
+		na := sp.peerNa
+		sp.peerNaMtx.Unlock()
+
+		if na == nil {
+			return true
+		}
+
+		if !s.addrManager.IsPeerNaValid(na, sp.NA()) {
+			return true
+		}
+
+		port, err := strconv.ParseUint(activeNetParams.DefaultPort, 10, 16)
+		if err != nil {
+			srvrLog.Errorf("unabled to parse active network port: %v", err)
+			return true
+		}
+
+		id := na.IP.String()
+		switch {
+		case na.IP.To4() != nil:
+			state.suggestionsMtx.Lock()
+			state.suggestions[addrmgr.IPv4Address][id]++
+			state.suggestionsMtx.Unlock()
+
+			state.ResolveLocalAddress(addrmgr.IPv4Address, s.addrManager,
+				s.services, uint16(port))
+
+		case na.IP.To16() != nil:
+			state.suggestionsMtx.Lock()
+			state.suggestions[addrmgr.IPv6Address][id]++
+			state.suggestionsMtx.Unlock()
+
+			state.ResolveLocalAddress(addrmgr.IPv6Address, s.addrManager,
+				s.services, uint16(port))
+
+		default:
+			return true
+		}
 	}
 
 	return true
@@ -1767,6 +1884,10 @@ func (s *server) peerHandler() {
 		outboundPeers:   make(map[int32]*serverPeer),
 		banned:          make(map[string]time.Time),
 		outboundGroups:  make(map[string]int),
+		suggestions: map[addrmgr.NetworkAddress]map[string]int32{
+			addrmgr.IPv4Address: make(map[string]int32),
+			addrmgr.IPv6Address: make(map[string]int32),
+		},
 	}
 
 	if !cfg.DisableDNSSeed {