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Update mDNS server handler

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This commit is contained in:
Alex X
2025-02-25 16:16:38 +03:00
parent effff6f88d
commit c50738005d
2 changed files with 126 additions and 112 deletions
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pkg/mdns/server.go
+101 -96
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@@ -20,7 +20,11 @@ func Serve(service string, entries []*ServiceEntry) error {
}
func (b *Browser) Serve(entries []*ServiceEntry) error {
var msg dns.Msg
names := make(map[string]*ServiceEntry, len(entries))
for _, entry := range entries {
name := entry.name() + "." + b.Service
names[name] = entry
}
buf := make([]byte, 1500)
for {
@@ -29,129 +33,130 @@ func (b *Browser) Serve(entries []*ServiceEntry) error {
break
}
if err = msg.Unpack(buf[:n]); err != nil {
var req dns.Msg // request
if err = req.Unpack(buf[:n]); err != nil {
continue
}
if !HasQuestionPTP(&msg, b.Service) {
// skip messages without Questions
if req.Question == nil {
continue
}
remoteIP := addr.(*net.UDPAddr).IP
localIP := MatchLocalIP(remoteIP)
localIP := b.MatchLocalIP(remoteIP)
// skip messages from unknown networks (can be docker network)
if localIP == nil {
continue
}
answer, err := NewDNSAnswer(entries, b.Service, localIP).Pack()
var res dns.Msg // response
for _, q := range req.Question {
if q.Qtype != dns.TypePTR || q.Qclass != dns.ClassINET {
continue
}
if q.Name == ServiceDNSSD {
AppendDNSSD(&res, b.Service)
} else if q.Name == b.Service {
for _, entry := range entries {
AppendEntry(&res, entry, b.Service, localIP)
}
} else if entry, ok := names[q.Name]; ok {
AppendEntry(&res, entry, b.Service, localIP)
}
}
if res.Answer == nil {
continue
}
res.MsgHdr.Response = true
res.MsgHdr.Authoritative = true
data, err := res.Pack()
if err != nil {
continue
}
for _, send := range b.Sends {
_, _ = send.WriteTo(answer, MulticastAddr)
_, _ = send.WriteTo(data, MulticastAddr)
}
}
return nil
}
func HasQuestionPTP(msg *dns.Msg, name string) bool {
for _, q := range msg.Question {
if q.Qtype == dns.TypePTR && q.Name == name {
return true
func (b *Browser) MatchLocalIP(remote net.IP) net.IP {
for _, ipn := range b.Nets {
if ipn.Contains(remote) {
return ipn.IP
}
}
return false
return nil
}
func NewDNSAnswer(entries []*ServiceEntry, service string, ip net.IP) *dns.Msg {
msg := dns.Msg{
MsgHdr: dns.MsgHdr{
Response: true,
Authoritative: true,
func AppendDNSSD(msg *dns.Msg, service string) {
msg.Answer = append(
msg.Answer,
&dns.PTR{
Hdr: dns.RR_Header{
Name: ServiceDNSSD, // _services._dns-sd._udp.local.
Rrtype: dns.TypePTR, // 12
Class: dns.ClassINET, // 1
Ttl: 4500,
},
Ptr: service, // _home-assistant._tcp.local.
},
}
for _, entry := range entries {
ptrName := entry.name() + "." + service
srvName := entry.name() + ".local."
msg.Answer = append(
msg.Answer,
&dns.PTR{
Hdr: dns.RR_Header{
Name: service,
Rrtype: dns.TypePTR,
Class: dns.ClassINET,
Ttl: 4500,
},
Ptr: ptrName,
},
)
msg.Extra = append(
msg.Extra,
&dns.TXT{
Hdr: dns.RR_Header{
Name: ptrName,
Rrtype: dns.TypeTXT,
Class: ClassCacheFlush,
Ttl: 4500,
},
Txt: entry.TXT(),
},
&dns.SRV{
Hdr: dns.RR_Header{
Name: ptrName,
Rrtype: dns.TypeSRV,
Class: ClassCacheFlush,
Ttl: 120,
Rdlength: 0,
},
Port: entry.Port,
Target: srvName,
},
&dns.A{
Hdr: dns.RR_Header{
Name: srvName,
Rrtype: dns.TypeA,
Class: ClassCacheFlush,
Ttl: 120,
Rdlength: 0,
},
A: ip,
},
)
}
return &msg
)
}
func MatchLocalIP(remote net.IP) net.IP {
intfs, err := net.Interfaces()
if err != nil {
return nil
}
func AppendEntry(msg *dns.Msg, entry *ServiceEntry, service string, ip net.IP) {
ptrName := entry.name() + "." + service
srvName := entry.name() + ".local."
for _, intf := range intfs {
if intf.Flags&net.FlagUp == 0 || intf.Flags&net.FlagLoopback != 0 {
continue
}
addrs, err := intf.Addrs()
if err != nil {
continue
}
for _, addr := range addrs {
switch v := addr.(type) {
case *net.IPNet:
if local := v.IP.To4(); local != nil && v.Contains(remote) {
return local
}
}
}
}
return nil
msg.Answer = append(
msg.Answer,
&dns.PTR{
Hdr: dns.RR_Header{
Name: service, // _home-assistant._tcp.local.
Rrtype: dns.TypePTR, // 12
Class: dns.ClassINET, // 1
Ttl: 4500,
},
Ptr: ptrName, // Home\ Assistant._home-assistant._tcp.local.
},
)
msg.Extra = append(
msg.Extra,
&dns.TXT{
Hdr: dns.RR_Header{
Name: ptrName, // Home\ Assistant._home-assistant._tcp.local.
Rrtype: dns.TypeTXT, // 16
Class: ClassCacheFlush, // 32769
Ttl: 4500,
},
Txt: entry.TXT(),
},
&dns.SRV{
Hdr: dns.RR_Header{
Name: ptrName, // Home\ Assistant._home-assistant._tcp.local.
Rrtype: dns.TypeSRV, // 33
Class: ClassCacheFlush, // 32769
Ttl: 120,
},
Port: entry.Port, // 8123
Target: srvName, // 963f1fa82b7142809711cebe7c826322.local.
},
&dns.A{
Hdr: dns.RR_Header{
Name: srvName, // 963f1fa82b7142809711cebe7c826322.local.
Rrtype: dns.TypeA, // 1
Class: ClassCacheFlush, // 32769
Ttl: 120,
},
A: ip,
},
)
}