P2P: try to limit the connection number per IP address (#1623)

** by default, MaxPeersPerIp is same as MaxPeers
 ** no restriction on TrustedNode
 ** add test case: TestOptionMaxPeersPerIp

cmd/geth/main.go

@@ -132,6 +132,7 @@ var (
 		utils.PruneAncientDataFlag,
 		utils.ListenPortFlag,
 		utils.MaxPeersFlag,
+		utils.MaxPeersPerIPFlag,
 		utils.MaxPendingPeersFlag,
 		utils.MiningEnabledFlag,
 		utils.MinerThreadsFlag,

cmd/geth/usage.go

@@ -176,6 +176,7 @@ var AppHelpFlagGroups = []flags.FlagGroup{
 			utils.DNSDiscoveryFlag,
 			utils.ListenPortFlag,
 			utils.MaxPeersFlag,
+			utils.MaxPeersPerIPFlag,
 			utils.MaxPendingPeersFlag,
 			utils.NATFlag,
 			utils.NoDiscoverFlag,

cmd/utils/flags.go

@@ -702,6 +702,13 @@ var (
 		Usage: "Maximum number of network peers (network disabled if set to 0)",
 		Value: node.DefaultConfig.P2P.MaxPeers,
 	}
+
+	MaxPeersPerIPFlag = cli.IntFlag{
+		Name:  "maxpeersperip",
+		Usage: "Maximum number of network peers from a single IP address, (default used if set to <= 0, which is same as MaxPeers)",
+		Value: node.DefaultConfig.P2P.MaxPeersPerIP,
+	}
+
 	MaxPendingPeersFlag = cli.IntFlag{
 		Name:  "maxpendpeers",
 		Usage: "Maximum number of pending connection attempts (defaults used if set to 0)",
@@ -1282,6 +1289,15 @@ func SetP2PConfig(ctx *cli.Context, cfg *p2p.Config) {
 			cfg.MaxPeers = lightPeers
 		}
 	}
+	// if max peers per ip is not set, use max peers
+	if cfg.MaxPeersPerIP <= 0 {
+		cfg.MaxPeersPerIP = cfg.MaxPeers
+	}
+	// flag like: `--maxpeersperip 10` could override the setting in config.toml
+	if ctx.GlobalIsSet(MaxPeersPerIPFlag.Name) {
+		cfg.MaxPeersPerIP = ctx.GlobalInt(MaxPeersPerIPFlag.Name)
+	}
+
 	if !(lightClient || lightServer) {
 		lightPeers = 0
 	}

eth/backend.go

@@ -656,7 +656,7 @@ func (s *Ethereum) Start() error {
 		maxPeers -= s.config.LightPeers
 	}
 	// Start the networking layer and the light server if requested
-	s.handler.Start(maxPeers)
+	s.handler.Start(maxPeers, s.p2pServer.MaxPeersPerIP)
 	return nil
 }
 

eth/handler.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"math"
 	"math/big"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -140,6 +141,9 @@ type handler struct {
 	maliciousVoteMonitor *monitor.MaliciousVoteMonitor
 	chain                *core.BlockChain
 	maxPeers             int
+	maxPeersPerIP        int
+	peersPerIP           map[string]int
+	peerPerIPLock        sync.Mutex
 
 	downloader   *downloader.Downloader
 	blockFetcher *fetcher.BlockFetcher
@@ -186,6 +190,7 @@ func newHandler(config *handlerConfig) (*handler, error) {
 		chain:                  config.Chain,
 		peers:                  config.PeerSet,
 		merger:                 config.Merger,
+		peersPerIP:             make(map[string]int),
 		whitelist:              config.Whitelist,
 		directBroadcast:        config.DirectBroadcast,
 		diffSync:               config.DiffSync,
@@ -387,11 +392,30 @@ func (h *handler) runEthPeer(peer *eth.Peer, handler eth.Handler) error {
 		}
 	}
 	// Ignore maxPeers if this is a trusted peer
-	if !peer.Peer.Info().Network.Trusted {
+	peerInfo := peer.Peer.Info()
+	if !peerInfo.Network.Trusted {
 		if reject || h.peers.len() >= h.maxPeers {
 			return p2p.DiscTooManyPeers
 		}
 	}
+
+	remoteAddr := peerInfo.Network.RemoteAddress
+	indexIP := strings.LastIndex(remoteAddr, ":")
+	if indexIP == -1 {
+		// there could be no IP address, such as a pipe
+		peer.Log().Debug("runEthPeer", "no ip address, remoteAddress", remoteAddr)
+	} else if !peerInfo.Network.Trusted {
+		remoteIP := remoteAddr[:indexIP]
+		h.peerPerIPLock.Lock()
+		if num, ok := h.peersPerIP[remoteIP]; ok && num >= h.maxPeersPerIP {
+			h.peerPerIPLock.Unlock()
+			peer.Log().Info("The IP has too many peers", "ip", remoteIP, "maxPeersPerIP", h.maxPeersPerIP,
+				"name", peerInfo.Name, "Enode", peerInfo.Enode)
+			return p2p.DiscTooManyPeers
+		}
+		h.peersPerIP[remoteIP] = h.peersPerIP[remoteIP] + 1
+		h.peerPerIPLock.Unlock()
+	}
 	peer.Log().Debug("Ethereum peer connected", "name", peer.Name())
 
 	// Register the peer locally
@@ -626,11 +650,32 @@ func (h *handler) unregisterPeer(id string) {
 	if err := h.peers.unregisterPeer(id); err != nil {
 		logger.Error("Ethereum peer removal failed", "err", err)
 	}
+
+	peerInfo := peer.Peer.Info()
+	remoteAddr := peerInfo.Network.RemoteAddress
+	indexIP := strings.LastIndex(remoteAddr, ":")
+	if indexIP == -1 {
+		// there could be no IP address, such as a pipe
+		peer.Log().Debug("unregisterPeer", "name", peerInfo.Name, "no ip address, remoteAddress", remoteAddr)
+	} else if !peerInfo.Network.Trusted {
+		remoteIP := remoteAddr[:indexIP]
+		h.peerPerIPLock.Lock()
+		if h.peersPerIP[remoteIP] <= 0 {
+			peer.Log().Error("unregisterPeer without record", "name", peerInfo.Name, "remoteAddress", remoteAddr)
+		} else {
+			h.peersPerIP[remoteIP] = h.peersPerIP[remoteIP] - 1
+			logger.Debug("unregisterPeer", "name", peerInfo.Name, "connectNum", h.peersPerIP[remoteIP])
+			if h.peersPerIP[remoteIP] == 0 {
+				delete(h.peersPerIP, remoteIP)
+			}
+		}
+		h.peerPerIPLock.Unlock()
+	}
 }
 
-func (h *handler) Start(maxPeers int) {
+func (h *handler) Start(maxPeers int, maxPeersPerIP int) {
 	h.maxPeers = maxPeers
-
+	h.maxPeersPerIP = maxPeersPerIP
 	// broadcast transactions
 	h.wg.Add(1)
 	h.txsCh = make(chan core.NewTxsEvent, txChanSize)

eth/handler_diff_test.go

@@ -96,7 +96,7 @@ func newTestBackendWithGenerator(blocks int) *testBackend {
 		BloomCache: 1,
 		Merger:     consensus.NewMerger(rawdb.NewMemoryDatabase()),
 	})
-	handler.Start(100)
+	handler.Start(100, 100)
 
 	txconfig := core.DefaultTxPoolConfig
 	txconfig.Journal = "" // Don't litter the disk with test journals

eth/handler_eth_test.go

@@ -20,6 +20,8 @@ import (
 	"fmt"
 	"math/big"
 	"math/rand"
+	"strconv"
+	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -148,8 +150,8 @@ func testForkIDSplit(t *testing.T, protocol uint) {
 			BloomCache: 1,
 		})
 	)
-	ethNoFork.Start(1000)
-	ethProFork.Start(1000)
+	ethNoFork.Start(1000, 1000)
+	ethProFork.Start(1000, 1000)
 
 	// Clean up everything after ourselves
 	defer chainNoFork.Stop()
@@ -928,3 +930,109 @@ func testBroadcastMalformedBlock(t *testing.T, protocol uint) {
 		}
 	}
 }
+
+func TestOptionMaxPeersPerIP(t *testing.T) {
+	t.Parallel()
+
+	handler := newTestHandler()
+	defer handler.close()
+	var (
+		genesis       = handler.chain.Genesis()
+		head          = handler.chain.CurrentBlock()
+		td            = handler.chain.GetTd(head.Hash(), head.NumberU64())
+		wg            = sync.WaitGroup{}
+		maxPeersPerIP = handler.handler.maxPeersPerIP
+		uniPort       = 1000
+	)
+
+	tryFunc := func(tryNum int, ip1 string, ip2 string, trust bool, doneCh chan struct{}) {
+		// Create a source peer to send messages through and a sink handler to receive them
+		p2pSrc, p2pSink := p2p.MsgPipe()
+		defer p2pSrc.Close()
+		defer p2pSink.Close()
+
+		peer1 := p2p.NewPeerPipe(enode.ID{0}, "", nil, p2pSrc)
+		peer1.UpdateTestRemoteAddr(ip1 + strconv.Itoa(uniPort))
+		peer2 := p2p.NewPeerPipe(enode.ID{byte(uniPort)}, "", nil, p2pSink)
+		peer2.UpdateTestRemoteAddr(ip2 + strconv.Itoa(uniPort))
+		if trust {
+			peer2.UpdateTrustFlagTest()
+		}
+		uniPort++
+
+		src := eth.NewPeer(eth.ETH66, peer1, p2pSrc, handler.txpool)
+		sink := eth.NewPeer(eth.ETH66, peer2, p2pSink, handler.txpool)
+		defer src.Close()
+		defer sink.Close()
+
+		wg.Add(1)
+		go func(num int) {
+			err := handler.handler.runEthPeer(sink, func(peer *eth.Peer) error {
+				wg.Done()
+				<-doneCh
+				return nil
+			})
+			// err is nil, connection ok and it is closed by the doneCh
+			if err == nil {
+				if trust || num <= maxPeersPerIP {
+					return
+				}
+				// if num > maxPeersPerIP and not trust, should report: p2p.DiscTooManyPeers
+				t.Errorf("current num is %d, maxPeersPerIP is %d, should failed", num, maxPeersPerIP)
+				return
+			}
+			wg.Done()
+			if trust {
+				t.Errorf("trust node should not failed, num is %d, maxPeersPerIP is %d, but failed:%s", num, maxPeersPerIP, err)
+			}
+			// err should be p2p.DiscTooManyPeers and num > maxPeersPerIP
+			if err == p2p.DiscTooManyPeers && num > maxPeersPerIP {
+				return
+			}
+
+			t.Errorf("current num is %d, maxPeersPerIP is %d, but failed:%s", num, maxPeersPerIP, err)
+		}(tryNum)
+
+		if err := src.Handshake(1, td, head.Hash(), genesis.Hash(), forkid.NewIDWithChain(handler.chain), forkid.NewFilter(handler.chain), nil); err != nil {
+			t.Fatalf("failed to run protocol handshake")
+		}
+		// make sure runEthPeer execute one by one.
+		wg.Wait()
+	}
+
+	// case 1: normal case
+	doneCh1 := make(chan struct{})
+	for tryNum := 1; tryNum <= maxPeersPerIP+2; tryNum++ {
+		tryFunc(tryNum, "1.2.3.11:", "1.2.3.22:", false, doneCh1)
+	}
+	close(doneCh1)
+
+	// case 2: once the previous connection was unregisterred, new connections with same IP can be accepted.
+	doneCh2 := make(chan struct{})
+	for tryNum := 1; tryNum <= maxPeersPerIP+2; tryNum++ {
+		tryFunc(tryNum, "1.2.3.11:", "1.2.3.22:", false, doneCh2)
+	}
+	close(doneCh2)
+
+	// case 3: ipv6 address, like: [2001:db8::1]:80
+	doneCh3 := make(chan struct{})
+	for tryNum := 1; tryNum <= maxPeersPerIP+2; tryNum++ {
+		tryFunc(tryNum, "[2001:db8::11]:", "[2001:db8::22]:", false, doneCh3)
+	}
+	close(doneCh3)
+
+	// case 4: same as case 2, but for ipv6
+	doneCh4 := make(chan struct{})
+	for tryNum := 1; tryNum <= maxPeersPerIP+2; tryNum++ {
+		tryFunc(tryNum, "[2001:db8::11]:", "[2001:db8::22]:", false, doneCh4)
+	}
+	close(doneCh4)
+
+	// case 5: test trust node
+	doneCh5 := make(chan struct{})
+	for tryNum := 1; tryNum <= maxPeersPerIP+2; tryNum++ {
+		tryFunc(tryNum, "[2001:db8::11]:", "[2001:db8::22]:", true, doneCh5)
+	}
+	close(doneCh5)
+
+}

eth/handler_test.go

@@ -177,7 +177,7 @@ func newTestHandlerWithBlocks(blocks int) *testHandler {
 		Sync:       downloader.SnapSync,
 		BloomCache: 1,
 	})
-	handler.Start(1000)
+	handler.Start(1000, 3)
 
 	return &testHandler{
 		db:       db,

node/defaults.go

@@ -47,9 +47,10 @@ var DefaultConfig = Config{
 	WSModules:           []string{"net", "web3"},
 	GraphQLVirtualHosts: []string{"localhost"},
 	P2P: p2p.Config{
-		ListenAddr: ":30303",
-		MaxPeers:   50,
-		NAT:        nat.Any(),
+		ListenAddr:    ":30303",
+		MaxPeers:      50,
+		MaxPeersPerIP: 0, // by default, it will be same as MaxPeers
+		NAT:           nat.Any(),
 	},
 }
 

p2p/peer.go

@@ -116,8 +116,9 @@ type Peer struct {
 	disc     chan DiscReason
 
 	// events receives message send / receive events if set
-	events   *event.Feed
-	testPipe *MsgPipeRW // for testing
+	events         *event.Feed
+	testPipe       *MsgPipeRW // for testing
+	testRemoteAddr string     // for testing
 }
 
 // NewPeer returns a peer for testing purposes.
@@ -203,9 +204,23 @@ func (p *Peer) RunningCap(protocol string, versions []uint) bool {
 
 // RemoteAddr returns the remote address of the network connection.
 func (p *Peer) RemoteAddr() net.Addr {
+	if len(p.testRemoteAddr) > 0 {
+		if addr, err := net.ResolveTCPAddr("tcp", p.testRemoteAddr); err == nil {
+			return addr
+		}
+		log.Warn("RemoteAddr", "invalid testRemoteAddr", p.testRemoteAddr)
+	}
 	return p.rw.fd.RemoteAddr()
 }
 
+func (p *Peer) UpdateTestRemoteAddr(addr string) { // test purpose only
+	p.testRemoteAddr = addr
+}
+
+func (p *Peer) UpdateTrustFlagTest() { // test purpose only
+	p.rw.set(trustedConn, true)
+}
+
 // LocalAddr returns the local address of the network connection.
 func (p *Peer) LocalAddr() net.Addr {
 	return p.rw.fd.LocalAddr()

p2p/server.go

@@ -81,6 +81,10 @@ type Config struct {
 	// connected. It must be greater than zero.
 	MaxPeers int
 
+	// MaxPeersPerIP is the maximum number of peers that can be
+	// connected from a single IP. It must be greater than zero.
+	MaxPeersPerIP int `toml:",omitempty"`
+
 	// MaxPendingPeers is the maximum number of peers that can be pending in the
 	// handshake phase, counted separately for inbound and outbound connections.
 	// Zero defaults to preset values.