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71 lines
1.4 KiB
71 lines
1.4 KiB
package main
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import (
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"net"
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"strings"
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"sync"
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"github.com/subgraph/fw-daemon/nfqueue"
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)
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type dnsCache struct {
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ipMap map[string]string
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lock sync.Mutex
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done chan struct{}
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}
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func NewDnsCache() *dnsCache {
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return &dnsCache{
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ipMap: make(map[string]string),
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done: make(chan struct{}),
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}
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}
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func (dc *dnsCache) processDNS(pkt *nfqueue.Packet) {
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dns := &dnsMsg{}
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if !dns.Unpack(pkt.Payload) {
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log.Warning("Failed to Unpack DNS message")
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return
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}
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if !dns.response {
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return
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}
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if len(dns.question) != 1 {
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log.Warning("Length of DNS Question section is not 1 as expected: %d", len(dns.question))
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return
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}
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q := dns.question[0]
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if q.Qtype == dnsTypeA {
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dc.processRecordA(q.Name, dns.answer)
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return
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}
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log.Info("Unhandled DNS message: %v", dns)
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}
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func (dc *dnsCache) processRecordA(name string, answers []dnsRR) {
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dc.lock.Lock()
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defer dc.lock.Unlock()
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for _, rr := range answers {
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switch rec := rr.(type) {
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case *dnsRR_A:
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ip := net.IPv4(byte(rec.A>>24), byte(rec.A>>16), byte(rec.A>>8), byte(rec.A)).String()
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if strings.HasSuffix(name, ".") {
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name = name[:len(name)-1]
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}
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dc.ipMap[ip] = name
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if !logRedact {
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log.Info("Adding %s: %s", name, ip)
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}
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default:
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log.Warning("Unexpected RR type in answer section of A response: %v", rec)
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}
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}
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}
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func (dc *dnsCache) Lookup(ip net.IP) string {
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dc.lock.Lock()
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defer dc.lock.Unlock()
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return dc.ipMap[ip.String()]
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}
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