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New asynchronous, caching DNS resolver for reverse resolutions
Add nodes for the remote side of connections iff we have a DNS reverse resolution for the IP.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| package endpoint | ||
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| import ( | ||
| "net" | ||
| "time" | ||
|
|
||
| "github.com/bluele/gcache" | ||
| ) | ||
|
|
||
| const ( | ||
| RAddrCacheLen = 500 // Default cache length | ||
|
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| raddrBacklog = 1000 | ||
| rAddrCacheExpiration = 30 * time.Minute | ||
| ) | ||
|
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| // ReverseResolver is a caching, reverse resolver | ||
| type ReverseResolver struct { | ||
| addresses chan string | ||
| cache gcache.Cache | ||
| } | ||
|
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| // NewReverseResolver starts a new reverse resolver that | ||
| // performs reverse resolutions and caches the result. | ||
| func NewReverseResolver(cacheLen int) *ReverseResolver { | ||
| r := ReverseResolver{ | ||
| addresses: make(chan string, raddrBacklog), | ||
| cache: gcache.New(cacheLen).LRU().Expiration(rAddrCacheExpiration).Build(), | ||
| } | ||
|
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| go r.run() | ||
| return &r | ||
| } | ||
|
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| // Get the reverse resolution for an IP address | ||
| // Note: it returns one of the possible names that can be obtained for that IP | ||
| func (r *ReverseResolver) Get(address string) (string, error) { | ||
| val, err := r.cache.Get(address) | ||
| if err == nil { | ||
| return val.(string), nil | ||
| } | ||
|
|
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| if err == gcache.NotFoundKeyError { | ||
| // we trigger a asynchronous reverse resolution when not cached | ||
| select { | ||
| case r.addresses <- address: | ||
| default: | ||
| } | ||
| } | ||
| return "", err | ||
| } | ||
|
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| func (r *ReverseResolver) run() { | ||
| throttle := time.Tick(time.Second / 10) | ||
| for address := range r.addresses { | ||
| <-throttle // rate limit our DNS resolutions | ||
| names, err := net.LookupAddr(address) | ||
| if err != nil { | ||
| continue | ||
| } | ||
| if len(names) > 0 { | ||
| r.cache.Set(address, names[0]) | ||
| } | ||
| } | ||
| } | ||
|
|
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| // Stop the async reverse resolver | ||
| func (r *ReverseResolver) Stop() { | ||
| close(r.addresses) | ||
| } |
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