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https://github.com/ethereum/go-ethereum.git
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42c013f2af
randomServers drew indices with rand.Intn into a dedup map, bounded by len(serverList)*2 iterations. When n approaches the number of configured servers, repeated random collisions can exhaust the iteration budget before n unique servers are collected, so the function sometimes returns fewer servers than requested even though enough exist. For example, with 2 configured servers and requestLimit==3 (capped to 2), the four allowed draws can collide and yield only a single server. If that server is down, ExternalIP fails without ever trying the other. Replace the sampling loop with rand.Perm, which produces a uniform permutation of all indices in one pass. Slicing the first n entries always yields exactly min(n, len(serverList)) distinct servers, with no probabilistic shortfall.
138 lines
3.3 KiB
Go
138 lines
3.3 KiB
Go
// Copyright 2025 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 nat
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import (
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_ "embed"
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"errors"
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"fmt"
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"math/rand"
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"net"
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"strings"
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"time"
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"github.com/ethereum/go-ethereum/log"
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stunV3 "github.com/pion/stun/v3"
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)
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//go:embed stun-list.txt
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var stunDefaultServers string
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const requestLimit = 3
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var errSTUNFailed = errors.New("STUN requests failed")
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type stun struct {
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serverList []string
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}
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func newSTUN(serverAddr string) (Interface, error) {
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s := new(stun)
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if serverAddr == "" {
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s.serverList = strings.Split(stunDefaultServers, "\n")
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} else {
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_, err := net.ResolveUDPAddr("udp", serverAddr)
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if err != nil {
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return nil, err
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}
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s.serverList = []string{serverAddr}
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}
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return s, nil
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}
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func (s stun) String() string {
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if len(s.serverList) == 1 {
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return fmt.Sprintf("stun:%s", s.serverList[0])
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}
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return "stun"
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}
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func (s stun) MarshalText() ([]byte, error) {
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return []byte(s.String()), nil
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}
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func (stun) SupportsMapping() bool {
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return false
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}
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func (stun) AddMapping(protocol string, extport, intport int, name string, lifetime time.Duration) (uint16, error) {
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return uint16(extport), nil
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}
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func (stun) DeleteMapping(string, int, int) error {
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return nil
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}
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func (s *stun) ExternalIP() (net.IP, error) {
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for _, server := range s.randomServers(requestLimit) {
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ip, err := s.externalIP(server)
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if err != nil {
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log.Debug("STUN request failed", "server", server, "err", err)
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continue
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}
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return ip, nil
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}
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return nil, errSTUNFailed
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}
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func (s *stun) randomServers(n int) []string {
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n = min(n, len(s.serverList))
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list := make([]string, 0, n)
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for _, index := range rand.Perm(len(s.serverList))[:n] {
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list = append(list, s.serverList[index])
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}
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return list
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}
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func (s *stun) externalIP(server string) (net.IP, error) {
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_, _, err := net.SplitHostPort(server)
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if err != nil {
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server += fmt.Sprintf(":%d", stunV3.DefaultPort)
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}
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log.Trace("Attempting STUN binding request", "server", server)
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conn, err := stunV3.Dial("udp", server)
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if err != nil {
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return nil, err
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}
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defer conn.Close()
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message, err := stunV3.Build(stunV3.TransactionID, stunV3.BindingRequest)
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if err != nil {
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return nil, err
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}
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var responseError error
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var mappedAddr stunV3.XORMappedAddress
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err = conn.Do(message, func(event stunV3.Event) {
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if event.Error != nil {
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responseError = event.Error
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return
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}
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if err := mappedAddr.GetFrom(event.Message); err != nil {
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responseError = err
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}
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})
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if err != nil {
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return nil, err
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}
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if responseError != nil {
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return nil, responseError
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}
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log.Trace("STUN returned IP", "server", server, "ip", mappedAddr.IP)
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return mappedAddr.IP, nil
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}
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