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Merge pull request safing#463 from safing/fix/dns-request-flooding
Improve nameserver and performance when in failing network condition
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,135 @@ | ||
| package nameserver | ||
|
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| import ( | ||
| "sync" | ||
| "time" | ||
|
|
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| "github.com/safing/portmaster/netenv" | ||
| "github.com/safing/portmaster/resolver" | ||
| ) | ||
|
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| type failingQuery struct { | ||
| // Until specifies until when the query should be regarded as failing. | ||
| Until time.Time | ||
|
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| // Keep specifies until when the failing status shall be kept. | ||
| Keep time.Time | ||
|
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| // Times specifies how often this query failed. | ||
| Times int | ||
|
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| // Err holds the error the query failed with. | ||
| Err error | ||
| } | ||
|
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| const ( | ||
| failingDelay = 900 * time.Millisecond | ||
| failingBaseDuration = 900 * time.Millisecond | ||
| failingFactorDuration = 500 * time.Millisecond | ||
| failingMaxDuration = 30 * time.Second | ||
| failingKeepAddedDuration = 10 * time.Second | ||
| ) | ||
|
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| var ( | ||
| failingQueries = make(map[string]*failingQuery) | ||
| failingQueriesLock sync.RWMutex | ||
| failingQueriesNetworkChangedFlag = netenv.GetNetworkChangedFlag() | ||
| ) | ||
|
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| func checkIfQueryIsFailing(q *resolver.Query) (failingErr error, failingUntil *time.Time) { | ||
| // If the network changed, reset the failed queries. | ||
| if failingQueriesNetworkChangedFlag.IsSet() { | ||
| failingQueriesNetworkChangedFlag.Refresh() | ||
|
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| failingQueriesLock.Lock() | ||
| defer failingQueriesLock.Unlock() | ||
|
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| // Compiler optimized map reset. | ||
| for key, _ := range failingQueries { | ||
| delete(failingQueries, key) | ||
| } | ||
|
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| return nil, nil | ||
| } | ||
|
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| failingQueriesLock.RLock() | ||
| defer failingQueriesLock.RUnlock() | ||
|
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| // Quickly return if map is empty. | ||
| if len(failingQueries) == 0 { | ||
| return nil, nil | ||
| } | ||
|
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| // Check if query failed recently. | ||
| failing, ok := failingQueries[q.ID()] | ||
| if !ok { | ||
| return nil, nil | ||
| } | ||
|
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| // Check if failing query should still be regarded as failing. | ||
| if time.Now().After(failing.Until) { | ||
| return nil, nil | ||
| } | ||
|
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| // Return failing error and until when it's valid. | ||
| return failing.Err, &failing.Until | ||
| } | ||
|
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| func addFailingQuery(q *resolver.Query, err error) { | ||
| // Check if we were given an error. | ||
| if err == nil { | ||
| return | ||
| } | ||
|
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| // Exclude reverse and mDNS queries, as they fail _often_ and are usually not | ||
| // retried quickly. | ||
| // if strings.HasSuffix(q.FQDN, ".in-addr.arpa.") || | ||
| // strings.HasSuffix(q.FQDN, ".ip6.arpa.") || | ||
| // strings.HasSuffix(q.FQDN, ".local.") { | ||
| // return | ||
| // } | ||
|
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| failingQueriesLock.Lock() | ||
| defer failingQueriesLock.Unlock() | ||
|
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| failing, ok := failingQueries[q.ID()] | ||
| if !ok { | ||
| failing = &failingQuery{Err: err} | ||
| failingQueries[q.ID()] = failing | ||
| } | ||
|
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| // Calculate fail duration. | ||
| // Initial fail duration will be at 900ms, perfect for a normal retry after 1s, | ||
| // but not any earlier. | ||
| failDuration := failingBaseDuration + time.Duration(failing.Times)*failingFactorDuration | ||
| if failDuration > failingMaxDuration { | ||
| failDuration = failingMaxDuration | ||
| } | ||
|
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| // Update failing query. | ||
| failing.Times++ | ||
| failing.Until = time.Now().Add(failDuration) | ||
| failing.Keep = failing.Until.Add(failingKeepAddedDuration) | ||
| } | ||
|
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| func cleanFailingQueries(maxRemove, maxMiss int) { | ||
| failingQueriesLock.Lock() | ||
| defer failingQueriesLock.Unlock() | ||
|
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| now := time.Now() | ||
| for key, failing := range failingQueries { | ||
| if now.After(failing.Keep) { | ||
| delete(failingQueries, key) | ||
|
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| maxRemove-- | ||
| if maxRemove == 0 { | ||
| return | ||
| } | ||
| } else { | ||
| maxMiss-- | ||
| if maxMiss == 0 { | ||
| return | ||
| } | ||
| } | ||
| } | ||
| } |
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