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Avoid race conditions in DNSSnooper's cached domains #2637

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merged 4 commits into from
Jun 23, 2017
Merged

Avoid race conditions in DNSSnooper's cached domains #2637

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4139494
Avoid race conditions in DNSSnooper's cached domains
Jun 22, 2017
22a31fc
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Jun 22, 2017
9778be7
Use a global lock instead
Jun 23, 2017
4006040
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Jun 23, 2017
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13 changes: 10 additions & 3 deletions probe/endpoint/dns_snooper_linux_amd64.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"encoding/binary"
"fmt"
"math"
"sync"
"time"

log "github.com/Sirupsen/logrus"
Expand All @@ -23,8 +24,11 @@ const (

// DNSSnooper is a snopper of DNS queries
type DNSSnooper struct {
stop chan struct{}
pcapHandle *pcap.Handle
stop chan struct{}
pcapHandle *pcap.Handle
// gcache is goroutine-safe, but the
// values cached values aren't

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reverseDNSMutex sync.RWMutex
reverseDNSCache gcache.Cache
decodingErrorCounts map[string]uint64 // for limiting
}
Expand Down Expand Up @@ -101,10 +105,11 @@ func (s *DNSSnooper) CachedNamesForIP(ip string) []string {
if err != nil {
return result
}

s.reverseDNSMutex.RLock()
for domain := range domains.(map[string]struct{}) {
result = append(result, domain)
}
s.reverseDNSMutex.RUnlock()

return result
}
Expand Down Expand Up @@ -272,7 +277,9 @@ func (s *DNSSnooper) processDNSMessage(dns *layers.DNS) {
s.reverseDNSCache.Set(ip, map[string]struct{}{newDomain: {}})
} else {
// TODO: Be smarter about the expiration of entries with pre-existing associated domains
s.reverseDNSMutex.Lock()
existingDomains.(map[string]struct{})[newDomain] = struct{}{}
s.reverseDNSMutex.Unlock()
}
}
}