github.com/Steality/go-ethereum@v1.9.7/p2p/netutil/iptrack.go (about)

     1  // Copyright 2018 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package netutil
    18  
    19  import (
    20  	"time"
    21  
    22  	"github.com/ethereum/go-ethereum/common/mclock"
    23  )
    24  
    25  // IPTracker predicts the external endpoint, i.e. IP address and port, of the local host
    26  // based on statements made by other hosts.
    27  type IPTracker struct {
    28  	window          time.Duration
    29  	contactWindow   time.Duration
    30  	minStatements   int
    31  	clock           mclock.Clock
    32  	statements      map[string]ipStatement
    33  	contact         map[string]mclock.AbsTime
    34  	lastStatementGC mclock.AbsTime
    35  	lastContactGC   mclock.AbsTime
    36  }
    37  
    38  type ipStatement struct {
    39  	endpoint string
    40  	time     mclock.AbsTime
    41  }
    42  
    43  // NewIPTracker creates an IP tracker.
    44  //
    45  // The window parameters configure the amount of past network events which are kept. The
    46  // minStatements parameter enforces a minimum number of statements which must be recorded
    47  // before any prediction is made. Higher values for these parameters decrease 'flapping' of
    48  // predictions as network conditions change. Window duration values should typically be in
    49  // the range of minutes.
    50  func NewIPTracker(window, contactWindow time.Duration, minStatements int) *IPTracker {
    51  	return &IPTracker{
    52  		window:        window,
    53  		contactWindow: contactWindow,
    54  		statements:    make(map[string]ipStatement),
    55  		minStatements: minStatements,
    56  		contact:       make(map[string]mclock.AbsTime),
    57  		clock:         mclock.System{},
    58  	}
    59  }
    60  
    61  // PredictFullConeNAT checks whether the local host is behind full cone NAT. It predicts by
    62  // checking whether any statement has been received from a node we didn't contact before
    63  // the statement was made.
    64  func (it *IPTracker) PredictFullConeNAT() bool {
    65  	now := it.clock.Now()
    66  	it.gcContact(now)
    67  	it.gcStatements(now)
    68  	for host, st := range it.statements {
    69  		if c, ok := it.contact[host]; !ok || c > st.time {
    70  			return true
    71  		}
    72  	}
    73  	return false
    74  }
    75  
    76  // PredictEndpoint returns the current prediction of the external endpoint.
    77  func (it *IPTracker) PredictEndpoint() string {
    78  	it.gcStatements(it.clock.Now())
    79  
    80  	// The current strategy is simple: find the endpoint with most statements.
    81  	counts := make(map[string]int)
    82  	maxcount, max := 0, ""
    83  	for _, s := range it.statements {
    84  		c := counts[s.endpoint] + 1
    85  		counts[s.endpoint] = c
    86  		if c > maxcount && c >= it.minStatements {
    87  			maxcount, max = c, s.endpoint
    88  		}
    89  	}
    90  	return max
    91  }
    92  
    93  // AddStatement records that a certain host thinks our external endpoint is the one given.
    94  func (it *IPTracker) AddStatement(host, endpoint string) {
    95  	now := it.clock.Now()
    96  	it.statements[host] = ipStatement{endpoint, now}
    97  	if time.Duration(now-it.lastStatementGC) >= it.window {
    98  		it.gcStatements(now)
    99  	}
   100  }
   101  
   102  // AddContact records that a packet containing our endpoint information has been sent to a
   103  // certain host.
   104  func (it *IPTracker) AddContact(host string) {
   105  	now := it.clock.Now()
   106  	it.contact[host] = now
   107  	if time.Duration(now-it.lastContactGC) >= it.contactWindow {
   108  		it.gcContact(now)
   109  	}
   110  }
   111  
   112  func (it *IPTracker) gcStatements(now mclock.AbsTime) {
   113  	it.lastStatementGC = now
   114  	cutoff := now.Add(-it.window)
   115  	for host, s := range it.statements {
   116  		if s.time < cutoff {
   117  			delete(it.statements, host)
   118  		}
   119  	}
   120  }
   121  
   122  func (it *IPTracker) gcContact(now mclock.AbsTime) {
   123  	it.lastContactGC = now
   124  	cutoff := now.Add(-it.contactWindow)
   125  	for host, ct := range it.contact {
   126  		if ct < cutoff {
   127  			delete(it.contact, host)
   128  		}
   129  	}
   130  }