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Merge pull request #676 from mirokuratczyk/discovery
Discovery enhancements
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,166 @@ | ||
| /* | ||
| * Copyright (c) 2024, Psiphon Inc. | ||
| * All rights reserved. | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU General Public License as published by | ||
| * the Free Software Foundation, either version 3 of the License, or | ||
| * (at your option) any later version. | ||
| * | ||
| * This program 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 General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
| * | ||
| */ | ||
|
|
||
| package server | ||
|
|
||
| import ( | ||
| "net" | ||
| "sync" | ||
|
|
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| "github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/errors" | ||
| "github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/parameters" | ||
| "github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/server/discovery" | ||
| ) | ||
|
|
||
| const ( | ||
| DISCOVERY_STRATEGY_CLASSIC = "classic" | ||
| DISCOVERY_STRATEGY_CONSISTENT = "consistent" | ||
| ) | ||
|
|
||
| // Discovery handles the discovery step of the "handshake" API request. It's | ||
| // safe for concurrent usage. | ||
| type Discovery struct { | ||
| support *SupportServices | ||
| currentStrategy string | ||
| discovery *discovery.Discovery | ||
|
|
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| sync.RWMutex | ||
| } | ||
|
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| func makeDiscovery(support *SupportServices) *Discovery { | ||
| return &Discovery{ | ||
| support: support, | ||
| } | ||
| } | ||
|
|
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| // Start starts discovery. | ||
| func (d *Discovery) Start() error { | ||
|
|
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| err := d.reload(false) | ||
| if err != nil { | ||
| return errors.Trace(err) | ||
| } | ||
|
|
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| return nil | ||
| } | ||
|
|
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| // reload reinitializes the underlying discovery component. If reloadedTactics | ||
| // is set and the target discovery strategy has not changed, then the | ||
| // underlying discovery component is not reinitialized. | ||
| func (d *Discovery) reload(reloadedTactics bool) error { | ||
|
|
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| // Determine which discovery strategy to use. Assumes no GeoIP targeting | ||
| // for the ServerDiscoveryStrategy tactic. | ||
|
|
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| p, err := d.support.ServerTacticsParametersCache.Get(NewGeoIPData()) | ||
| if err != nil { | ||
| return errors.Trace(err) | ||
| } | ||
|
|
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| strategy := "" | ||
| if !p.IsNil() { | ||
| strategy = p.String(parameters.ServerDiscoveryStrategy) | ||
| } | ||
| if strategy == "" { | ||
| // No tactics are configured; default to consistent discovery. | ||
| strategy = DISCOVERY_STRATEGY_CONSISTENT | ||
| } | ||
|
|
||
| // Do not reinitialize underlying discovery component if only tactics have | ||
| // been reloaded and the discovery strategy has not changed. | ||
| if reloadedTactics && d.support.discovery.currentStrategy == strategy { | ||
| return nil | ||
| } | ||
|
|
||
| // Initialize new discovery strategy. | ||
| // TODO: do not reinitialize discovery if the discovery strategy and | ||
| // discovery servers have not changed. | ||
| var discoveryStrategy discovery.DiscoveryStrategy | ||
| if strategy == DISCOVERY_STRATEGY_CONSISTENT { | ||
| discoveryStrategy, err = discovery.NewConsistentHashingDiscovery() | ||
| if err != nil { | ||
| return errors.Trace(err) | ||
| } | ||
| } else if strategy == DISCOVERY_STRATEGY_CLASSIC { | ||
| discoveryStrategy, err = discovery.NewClassicDiscovery( | ||
| d.support.Config.DiscoveryValueHMACKey) | ||
| if err != nil { | ||
| return errors.Trace(err) | ||
| } | ||
| } else { | ||
| return errors.Tracef("unknown strategy %s", strategy) | ||
| } | ||
|
|
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| // Initialize and set underlying discovery component. Replaces old | ||
| // component if discovery is already initialized. | ||
|
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| oldDiscovery := d.discovery | ||
|
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| discovery := discovery.MakeDiscovery( | ||
| d.support.PsinetDatabase.GetDiscoveryServers(), | ||
| discoveryStrategy) | ||
|
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| discovery.Start() | ||
|
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| d.Lock() | ||
|
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| d.discovery = discovery | ||
| d.currentStrategy = strategy | ||
|
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| d.Unlock() | ||
|
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| // Ensure resources used by previous underlying discovery component are | ||
| // cleaned up. | ||
| // Note: a more efficient impementation would not recreate the underlying | ||
| // discovery instance if the discovery strategy has not changed, but | ||
| // instead would update the underlying set of discovery servers if the set | ||
| // of discovery servers has changed. | ||
| if oldDiscovery != nil { | ||
| oldDiscovery.Stop() | ||
| } | ||
|
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| log.WithTraceFields( | ||
| LogFields{"discovery_strategy": strategy}).Infof("reloaded discovery") | ||
|
|
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| return nil | ||
| } | ||
|
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| // Stop stops discovery and cleans up underlying resources. | ||
| func (d *Discovery) Stop() { | ||
| d.discovery.Stop() | ||
| } | ||
|
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| // DiscoverServers selects new encoded server entries to be "discovered" by | ||
| // the client, using the client's IP address as the input into the discovery | ||
| // algorithm. | ||
| func (d *Discovery) DiscoverServers(clientIP net.IP) []string { | ||
|
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| d.RLock() | ||
| defer d.RUnlock() | ||
|
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| servers := d.discovery.SelectServers(clientIP) | ||
|
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| encodedServerEntries := make([]string, 0) | ||
|
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| for _, server := range servers { | ||
| encodedServerEntries = append(encodedServerEntries, server.EncodedServerEntry) | ||
| } | ||
|
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| return encodedServerEntries | ||
| } |
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