mDNS parser: skip a 'Record' on parse error

[asashnov]

Skipping an unknown Record is much better then ignoring the entire Message.

I'm not sure what caused the parse error. Sometimes it happens, sometime don't, maybe somehow interfere with my local avahi server and used cache in code.

I dumped the example of such UDP payload (QByteArray packet dump):
mDNS_UDP_packet.zip

But whatever the reason of parse error, it makes sense to proceed with records which parsed successfully. Otherwise mDNS browser will not show anything.

Here was my research, comparsion 'offset' in qmdns parser and offset the same records in WireShark:

Received message: QTime("23:00:03.420")
   no queries
   attached records:
    Record(PTR _unipro-laptimer._tcp.local.)4500
    Record(SRV unigo-12345._unipro-laptimer._tcp.local.)120
    Record(NSEC unigo-12345.local.)4500
    Record(? )146821888

44 bytes is difference between IP packet and UDP payload start.

PTR start: 3*16 + 8 - 44  = 12 - OK ( record 0 )
SRV start: 6*16 + 13 - 44 = 65 - OK ( record 1 )
NSEC start: 8*16 + 13 - 44 = 97 - OK ( record 2 )  - NSEC parsed incorrectly
A start: 10*16 + 3 - 44 = 119  : wrong in qmdnsentine: 113 (NSEC wasn't fully processed)