Summary: mDNS: does not respond to probes via multicast
Project: lwIP - A Lightweight TCP/IP stack
Submitted by: jasperv
Submitted on: Wed 14 Nov 2018 04:48:56 PM CET
Severity: 3 - Normal
Item Group: Faulty Behaviour
Assigned to: None
Discussion Lock: Any
Planned Release: None
lwIP version: git head
The mDNS responder only responds to a probe query via unicast because
according to the RFC, a probe should have the QU bit on.
At the moment the QU bit is ignored and a probe is always answered via unicast
(is easier, no multicast timeout issues).
After more testing we found that not all implementations follow the RFC's
should (avahi-daemon for example). Avahi sends it's probe messages with the QM
flag. This can easily be seen when publishing a service via avahi-publish.
This commit adds support for multicast probe answering with the needed