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