[lwip-devel] [bug #58142] mDNS: RFC violation after recent changes - affecting probing

[David GIRAULT]

Follow-up Comment #1, bug #58142 (project lwip):

Hi jasper,


> However, for tiebreaking to work correctly in all
> cases, the Authority Section must contain all the records and
> proposed rdata being probed for uniqueness.

The key word here is uniqueness. Since the TXT record don't require uniqueness
in the network, it should not be used during tiebreaking.

Perhaps I have misunderstood the RFC, but BCT always fails for the `WINNING
SIMULTANEOUS PROBES` tests without this fix.

May be PROBE tiebreaking checks in lwIP should not use this function at all.

You may revert this commit, but a better fix must be added to replace it.

Perhaps removing the TXT record after the call to
`mdns_define_probe_rrs_to_send` in `mdns_handle_probe_tiebreaking` ?

BCT never have TXT record in it's conflicting probe, even if one exist in the
probe sent by lwIP. It may be a BCT bug since according the Apple
mDNSResponder source code I've just check, the TXT record is typed
`kDNSRecordTypeUnique` like the SRV record and is included in probe sent.

Additionnaly, you should try using the dnssd daemon from Apple instead of
Avahi ;-). RFC6762 is an Apple RFC, and reference implementation is in
mDNSResponder which was open-source. See here:
https://opensource.apple.com/tarballs/mDNSResponder/.

Regards,
David

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