Initial commit after restructure
This commit is contained in:
Daniel
331
intel/mdns.go
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331
intel/mdns.go
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@@ -0,0 +1,331 @@
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// Copyright Safing ICS Technologies GmbH. Use of this source code is governed by the AGPL license that can be found in the LICENSE file.
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package intel
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import (
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"errors"
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"fmt"
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"net"
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"github.com/Safing/safing-core/log"
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"strings"
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"sync"
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"time"
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"github.com/miekg/dns"
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)
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const (
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DNSClassMulticast = dns.ClassINET | 1<<15
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)
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var (
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multicast4Conn *net.UDPConn
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multicast6Conn *net.UDPConn
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unicast4Conn *net.UDPConn
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unicast6Conn *net.UDPConn
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questions = make(map[uint16]savedQuestion)
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questionsLock sync.Mutex
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)
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type savedQuestion struct {
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question dns.Question
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expires int64
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}
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func init() {
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go listenToMDNS()
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}
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func indexOfRR(entry *dns.RR_Header, list *[]dns.RR) int {
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for k, v := range *list {
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if entry.Name == v.Header().Name && entry.Rrtype == v.Header().Rrtype {
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return k
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}
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}
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return -1
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}
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func listenToMDNS() {
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var err error
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messages := make(chan *dns.Msg)
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multicast4Conn, err = net.ListenMulticastUDP("udp4", nil, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 251), Port: 5353})
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if err != nil {
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// TODO: retry after some time
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log.Warningf("intel(mdns): failed to create udp4 listen multicast socket: %s", err)
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} else {
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go listenForDNSPackets(multicast4Conn, messages)
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}
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multicast6Conn, err = net.ListenMulticastUDP("udp6", nil, &net.UDPAddr{IP: net.IP([]byte{0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfb}), Port: 5353})
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if err != nil {
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// TODO: retry after some time
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log.Warningf("intel(mdns): failed to create udp6 listen multicast socket: %s", err)
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} else {
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go listenForDNSPackets(multicast6Conn, messages)
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}
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unicast4Conn, err = net.ListenUDP("udp4", &net.UDPAddr{IP: net.IPv4zero, Port: 0})
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if err != nil {
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// TODO: retry after some time
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log.Warningf("intel(mdns): failed to create udp4 listen socket: %s", err)
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} else {
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go listenForDNSPackets(unicast4Conn, messages)
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}
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unicast6Conn, err = net.ListenUDP("udp6", &net.UDPAddr{IP: net.IPv6zero, Port: 0})
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if err != nil {
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// TODO: retry after some time
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log.Warningf("intel(mdns): failed to create udp6 listen socket: %s", err)
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} else {
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go listenForDNSPackets(unicast6Conn, messages)
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}
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for {
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select {
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case message := <-messages:
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// log.Tracef("intel: got net mdns message: %s", message)
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var question *dns.Question
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var saveFullRequest bool
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scavengedRecords := make(map[string]*dns.RR)
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var rrCache *RRCache
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// save every received response
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// if previous save was less than 2 seconds ago, add to response, else replace
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// pick out A and AAAA records and save seperately
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// continue if not response
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if !message.Response {
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// log.Tracef("intel: mdns message has no response, ignoring")
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continue
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}
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// continue if rcode is not success
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if message.Rcode != dns.RcodeSuccess {
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// log.Tracef("intel: mdns message has error, ignoring")
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continue
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}
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// continue if answer section is empty
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if len(message.Answer) == 0 {
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// log.Tracef("intel: mdns message has no answers, ignoring")
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continue
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}
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// continue if no question
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if len(message.Question) == 0 {
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questionsLock.Lock()
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savedQ, ok := questions[message.MsgHdr.Id]
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questionsLock.Unlock()
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if ok {
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question = &savedQ.question
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}
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} else {
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question = &message.Question[0]
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}
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if question != nil {
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// continue if class is not INTERNET
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if question.Qclass != dns.ClassINET && question.Qclass != DNSClassMulticast {
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// log.Tracef("intel: mdns question is not of class INET, ignoring")
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continue
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}
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saveFullRequest = true
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}
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// get entry from database
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if saveFullRequest {
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rrCache, err = GetRRCache(question.Name, dns.Type(question.Qtype))
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if err != nil || rrCache.Modified < time.Now().Add(-2*time.Second).Unix() || rrCache.Expires < time.Now().Unix() {
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rrCache = &RRCache{}
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}
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}
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for _, entry := range message.Answer {
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if strings.HasSuffix(entry.Header().Name, ".local.") || domainInScopes(entry.Header().Name, localReverseScopes) {
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if saveFullRequest {
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k := indexOfRR(entry.Header(), &rrCache.Answer)
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if k == -1 {
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rrCache.Answer = append(rrCache.Answer, entry)
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} else {
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rrCache.Answer[k] = entry
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}
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}
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switch entry.(type) {
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case *dns.A:
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scavengedRecords[fmt.Sprintf("%sA", entry.Header().Name)] = &entry
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case *dns.AAAA:
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scavengedRecords[fmt.Sprintf("%sAAAA", entry.Header().Name)] = &entry
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case *dns.PTR:
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if !strings.HasPrefix(entry.Header().Name, "_") {
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scavengedRecords[fmt.Sprintf("%sPTR", entry.Header().Name)] = &entry
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}
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}
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}
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}
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for _, entry := range message.Ns {
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if strings.HasSuffix(entry.Header().Name, ".local.") || domainInScopes(entry.Header().Name, localReverseScopes) {
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if saveFullRequest {
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k := indexOfRR(entry.Header(), &rrCache.Ns)
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if k == -1 {
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rrCache.Ns = append(rrCache.Ns, entry)
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} else {
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rrCache.Ns[k] = entry
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}
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}
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switch entry.(type) {
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case *dns.A:
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scavengedRecords[fmt.Sprintf("%sA", entry.Header().Name)] = &entry
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case *dns.AAAA:
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scavengedRecords[fmt.Sprintf("%sAAAA", entry.Header().Name)] = &entry
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case *dns.PTR:
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if !strings.HasPrefix(entry.Header().Name, "_") {
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scavengedRecords[fmt.Sprintf("%sPTR", entry.Header().Name)] = &entry
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}
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}
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}
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}
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// TODO: scan Extra for A and AAAA records and save them seperately
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for _, entry := range message.Extra {
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if strings.HasSuffix(entry.Header().Name, ".local.") || domainInScopes(entry.Header().Name, localReverseScopes) {
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if saveFullRequest {
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k := indexOfRR(entry.Header(), &rrCache.Extra)
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if k == -1 {
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rrCache.Extra = append(rrCache.Extra, entry)
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} else {
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rrCache.Extra[k] = entry
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}
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}
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switch entry.(type) {
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case *dns.A:
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scavengedRecords[fmt.Sprintf("%sA", entry.Header().Name)] = &entry
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case *dns.AAAA:
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scavengedRecords[fmt.Sprintf("%sAAAA", entry.Header().Name)] = &entry
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case *dns.PTR:
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if !strings.HasPrefix(entry.Header().Name, "_") {
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scavengedRecords[fmt.Sprintf("%sPTR", entry.Header().Name)] = &entry
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}
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}
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}
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}
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if saveFullRequest {
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rrCache.Clean(60)
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rrCache.CreateWithType(question.Name, dns.Type(question.Qtype))
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// log.Tracef("intel: mdns saved full reply to %s%s", question.Name, dns.Type(question.Qtype).String())
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}
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for k, v := range scavengedRecords {
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if saveFullRequest {
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if k == fmt.Sprintf("%s%s", question.Name, dns.Type(question.Qtype).String()) {
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continue
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}
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}
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rrCache = &RRCache{
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Answer: []dns.RR{*v},
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}
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rrCache.Clean(60)
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rrCache.Create(k)
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// log.Tracef("intel: mdns scavenged %s", k)
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}
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}
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cleanSavedQuestions()
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}
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}
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func listenForDNSPackets(conn *net.UDPConn, messages chan *dns.Msg) {
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buf := make([]byte, 65536)
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for {
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// log.Tracef("debug: listening...")
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n, err := conn.Read(buf)
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// n, _, err := conn.ReadFrom(buf)
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// n, _, err := conn.ReadFromUDP(buf)
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if err != nil {
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// log.Tracef("intel: failed to read packet: %s", err)
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continue
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}
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// log.Tracef("debug: read something...")
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message := new(dns.Msg)
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if err = message.Unpack(buf[:n]); err != nil {
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// log.Tracef("intel: failed to unpack message: %s", err)
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continue
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}
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// log.Tracef("debug: parsed message...")
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messages <- message
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}
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}
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func queryMulticastDNS(resolver *Resolver, fqdn string, qtype dns.Type) (*RRCache, error) {
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q := new(dns.Msg)
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q.SetQuestion(fqdn, uint16(qtype))
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// request unicast response
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// q.Question[0].Qclass |= 1 << 15
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q.RecursionDesired = false
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saveQuestion(q)
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questionsLock.Lock()
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defer questionsLock.Unlock()
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questions[q.MsgHdr.Id] = savedQuestion{
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question: q.Question[0],
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expires: time.Now().Add(10 * time.Second).Unix(),
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}
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buf, err := q.Pack()
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if err != nil {
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return nil, fmt.Errorf("failed to pack query: %s", err)
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}
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if unicast4Conn == nil && unicast6Conn == nil {
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return nil, errors.New("unicast mdns connections not initialized")
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}
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if unicast4Conn != nil && uint16(qtype) != dns.TypeAAAA {
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unicast4Conn.SetWriteDeadline(time.Now().Add(1 * time.Second))
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_, err = unicast4Conn.WriteToUDP(buf, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 251), Port: 5353})
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if err != nil {
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return nil, fmt.Errorf("failed to send query: %s", err)
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}
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}
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if unicast6Conn != nil && uint16(qtype) != dns.TypeA {
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unicast6Conn.SetWriteDeadline(time.Now().Add(1 * time.Second))
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_, err = unicast6Conn.WriteToUDP(buf, &net.UDPAddr{IP: net.IP([]byte{0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfb}), Port: 5353})
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if err != nil {
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return nil, fmt.Errorf("failed to send query: %s", err)
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}
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}
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time.Sleep(1 * time.Second)
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rrCache, err := GetRRCache(fqdn, qtype)
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if err == nil {
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return rrCache, nil
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}
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return nil, nil
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}
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func saveQuestion(q *dns.Msg) {
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questionsLock.Lock()
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defer questionsLock.Unlock()
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// log.Tracef("intel: saving mdns question id=%d, name=%s", q.MsgHdr.Id, q.Question[0].Name)
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questions[q.MsgHdr.Id] = savedQuestion{
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question: q.Question[0],
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expires: time.Now().Add(10 * time.Second).Unix(),
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}
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}
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func cleanSavedQuestions() {
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questionsLock.Lock()
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defer questionsLock.Unlock()
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now := time.Now().Unix()
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for k, v := range questions {
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if v.expires < now {
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delete(questions, k)
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}
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}
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}
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