p2p/netutil: add IPTracker

p2p/netutil/iptrack.go

@@ -0,0 +1,116 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package netutil
+
+import (
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+// IPTracker predicts the external endpoint, i.e. IP address and port, of the local host
+// based on statements made by other hosts.
+type IPTracker struct {
+	window        time.Duration
+	contactWindow time.Duration
+	minStatements int
+	clock         mclock.Clock
+	statements    map[string]ipStatement
+	contact       map[string]mclock.AbsTime
+	// TODO add DistinctNetSet for additional protection
+}
+
+type ipStatement struct {
+	endpoint string
+	time     mclock.AbsTime
+}
+
+// NewIPTracker creates an IP tracker.
+//
+// The window parameters configure the amount of past network events which are kept. The
+// minStatements parameter enforces a minimum number of statements which must be recorded
+// before any prediction is made. Higher values for these parameters decrease 'flapping' of
+// predictions as network conditions change. Window duration values should typically be in
+// the range of minutes.
+func NewIPTracker(window, contactWindow time.Duration, minStatements int) *IPTracker {
+	return &IPTracker{
+		window:        window,
+		contactWindow: contactWindow,
+		statements:    make(map[string]ipStatement),
+		minStatements: minStatements,
+		contact:       make(map[string]mclock.AbsTime),
+		clock:         mclock.System{},
+	}
+}
+
+// PredictFullConeNAT checks whether the local host is behind full cone NAT.
+func (it *IPTracker) PredictFullConeNAT() bool {
+	now := it.clock.Now()
+	it.gcContact(now)
+	it.gcStatements(now)
+	for host := range it.statements {
+		if _, ok := it.contact[host]; !ok {
+			return true
+		}
+	}
+	return false
+}
+
+// PredictEndpoint returns the current prediction of the external endpoint.
+func (it *IPTracker) PredictEndpoint() string {
+	it.gcStatements(it.clock.Now())
+
+	// The current strategy is simple: find the endpoint with most statements.
+	counts := make(map[string]int)
+	maxcount, max := 0, ""
+	for _, s := range it.statements {
+		c := counts[s.endpoint] + 1
+		counts[s.endpoint] = c
+		if c > maxcount && c >= it.minStatements {
+			maxcount, max = c, s.endpoint
+		}
+	}
+	return max
+}
+
+// AddStatement records that a certain host thinks our external endpoint is the one given.
+func (it *IPTracker) AddStatement(host, endpoint string) {
+	it.statements[host] = ipStatement{endpoint, it.clock.Now()}
+}
+
+// AddContact records that a packet containing endpoint information has been sent to a certain host.
+func (it *IPTracker) AddContact(host string) {
+	it.contact[host] = it.clock.Now()
+}
+
+func (it *IPTracker) gcStatements(now mclock.AbsTime) {
+	cutoff := now.Add(-it.window)
+	for host, s := range it.statements {
+		if s.time < cutoff {
+			delete(it.statements, host)
+		}
+	}
+}
+
+func (it *IPTracker) gcContact(now mclock.AbsTime) {
+	cutoff := now.Add(-it.contactWindow)
+	for host, ct := range it.contact {
+		if ct < cutoff {
+			delete(it.contact, host)
+		}
+	}
+}

p2p/netutil/iptrack_test.go

@@ -0,0 +1,85 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package netutil
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+const (
+	opStatement = iota
+	opContact
+	opPredict
+)
+
+type iptrackTestEvent struct {
+	op       int
+	time     int // absolute, in milliseconds
+	ip, from string
+}
+
+func TestIPTracker(t *testing.T) {
+	tests := map[string][]iptrackTestEvent{
+		"minStatements": {
+			{opPredict, 0, "", ""},
+			{opStatement, 0, "127.0.0.1", "127.0.0.2"},
+			{opPredict, 1000, "", ""},
+			{opStatement, 1000, "127.0.0.1", "127.0.0.3"},
+			{opPredict, 1000, "", ""},
+			{opStatement, 1000, "127.0.0.1", "127.0.0.4"},
+			{opPredict, 1000, "127.0.0.1", ""},
+		},
+		"window": {
+			{opStatement, 0, "127.0.0.1", "127.0.0.2"},
+			{opStatement, 2000, "127.0.0.1", "127.0.0.3"},
+			{opStatement, 3000, "127.0.0.1", "127.0.0.4"},
+			{opPredict, 10000, "127.0.0.1", ""},
+			{opPredict, 10001, "", ""}, // first statement expired
+			{opStatement, 10100, "127.0.0.1", "127.0.0.2"},
+			{opPredict, 10200, "127.0.0.1", ""},
+		},
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) { runIPTrackerTest(t, test) })
+	}
+}
+
+func runIPTrackerTest(t *testing.T, evs []iptrackTestEvent) {
+	var (
+		clock mclock.Simulated
+		it    = NewIPTracker(10*time.Second, 10*time.Second, 3)
+	)
+	it.clock = &clock
+	for i, ev := range evs {
+		evtime := time.Duration(ev.time) * time.Millisecond
+		clock.Run(evtime - time.Duration(clock.Now()))
+		switch ev.op {
+		case opStatement:
+			it.AddStatement(ev.from, ev.ip)
+		case opContact:
+			it.AddContact(ev.from)
+		case opPredict:
+			if pred := it.PredictEndpoint(); pred != ev.ip {
+				t.Errorf("op %d: wrong prediction %q, want %q", i, pred, ev.ip)
+			}
+		}
+	}
+}