filter local addresses (for WAN) and localhost addresses (for LAN)

dht.go

@@ -157,6 +157,10 @@ type IpfsDHT struct {
 
 	// configuration variables for tests
 	testAddressUpdateProcessing bool
+
+	// addrFilter is used to filter the addresses we put into the peer store.
+	// Mostly used to filter out localhost and local addresses.
+	addrFilter func([]ma.Multiaddr) []ma.Multiaddr
 }
 
 // Assert that IPFS assumptions about interfaces aren't broken. These aren't a
@@ -301,6 +305,7 @@ func makeDHT(ctx context.Context, h host.Host, cfg dhtcfg.Config) (*IpfsDHT, err
 		queryPeerFilter:        cfg.QueryPeerFilter,
 		routingTablePeerFilter: cfg.RoutingTable.PeerFilter,
 		rtPeerDiversityFilter:  cfg.RoutingTable.DiversityFilter,
+		addrFilter:             cfg.AddressFilter,
 
 		fixLowPeersChan: make(chan struct{}, 1),
 
@@ -884,5 +889,8 @@ func (dht *IpfsDHT) maybeAddAddrs(p peer.ID, addrs []ma.Multiaddr, ttl time.Dura
 	if p == dht.self || dht.host.Network().Connectedness(p) == network.Connected {
 		return
 	}
+	if dht.addrFilter != nil {
+		addrs = dht.addrFilter(addrs)
+	}
 	dht.peerstore.AddAddrs(p, addrs, ttl)
 }

dht_options.go

@@ -7,13 +7,13 @@ import (
 
 	dhtcfg "github.com/libp2p/go-libp2p-kad-dht/internal/config"
 	"github.com/libp2p/go-libp2p-kad-dht/providers"
-	"github.com/libp2p/go-libp2p/core/peer"
-	"github.com/libp2p/go-libp2p/core/protocol"
-
 	"github.com/libp2p/go-libp2p-kbucket/peerdiversity"
 	record "github.com/libp2p/go-libp2p-record"
+	"github.com/libp2p/go-libp2p/core/peer"
+	"github.com/libp2p/go-libp2p/core/protocol"
 
 	ds "github.com/ipfs/go-datastore"
+	ma "github.com/multiformats/go-multiaddr"
 )
 
 // ModeOpt describes what mode the dht should operate in
@@ -337,3 +337,13 @@ func OptimisticProvideJobsPoolSize(size int) Option {
 		return nil
 	}
 }
+
+// AddressFilter allows to configure the address filtering function.
+// This function is run before addresses are added to the peerstore.
+// It is most useful to avoid adding localhost / local addresses.
+func AddressFilter(f func([]ma.Multiaddr) []ma.Multiaddr) Option {
+	return func(c *dhtcfg.Config) error {
+		c.AddressFilter = f
+		return nil
+	}
+}

dual/dual.go

@@ -1,4 +1,4 @@
-// Package dual provides an implementaiton of a split or "dual" dht, where two parallel instances
+// Package dual provides an implementation of a split or "dual" dht, where two parallel instances
 // are maintained for the global internet and the local LAN respectively.
 package dual
 
@@ -19,6 +19,7 @@ import (
 	"github.com/libp2p/go-libp2p/core/protocol"
 	"github.com/libp2p/go-libp2p/core/routing"
 	ma "github.com/multiformats/go-multiaddr"
+	manet "github.com/multiformats/go-multiaddr/net"
 
 	"github.com/hashicorp/go-multierror"
 )
@@ -101,6 +102,8 @@ func New(ctx context.Context, h host.Host, options ...Option) (*DHT, error) {
 			dht.QueryFilter(dht.PublicQueryFilter),
 			dht.RoutingTableFilter(dht.PublicRoutingTableFilter),
 			dht.RoutingTablePeerDiversityFilter(dht.NewRTPeerDiversityFilter(h, maxPrefixCountPerCpl, maxPrefixCount)),
+			// filter out all private addresses
+			dht.AddressFilter(func(addrs []ma.Multiaddr) []ma.Multiaddr { return ma.FilterAddrs(addrs, manet.IsPublicAddr) }),
 		),
 	)
 	if err != nil {
@@ -111,6 +114,10 @@ func New(ctx context.Context, h host.Host, options ...Option) (*DHT, error) {
 			dht.ProtocolExtension(LanExtension),
 			dht.QueryFilter(dht.PrivateQueryFilter),
 			dht.RoutingTableFilter(dht.PrivateRoutingTableFilter),
+			// filter out localhost IP addresses
+			dht.AddressFilter(func(addrs []ma.Multiaddr) []ma.Multiaddr {
+				return ma.FilterAddrs(addrs, func(a ma.Multiaddr) bool { return !manet.IsIPLoopback(a) })
+			}),
 		),
 	)
 	if err != nil {

internal/config/config.go

@@ -13,6 +13,7 @@ import (
 	"github.com/libp2p/go-libp2p/core/host"
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/libp2p/go-libp2p/core/protocol"
+	ma "github.com/multiformats/go-multiaddr"
 )
 
 // DefaultPrefix is the application specific prefix attached to all DHT protocols by default.
@@ -58,6 +59,7 @@ type Config struct {
 	}
 
 	BootstrapPeers func() []peer.AddrInfo
+	AddressFilter  func([]ma.Multiaddr) []ma.Multiaddr
 
 	// test specific Config options
 	DisableFixLowPeers          bool