Incomplete UDP support for binding to wildcard address
I am using kresd by virtue of running Turris OS, and the default behavior is to bind to 0.0.0.0 (with no way to turn it off https://gitlab.labs.nic.cz/turris/turris-os-packages/issues/196).
If I send an UDP request on interface A with a destination IP matching the address assigned to interface B, the answer has as source IP the address assigned to interface A. The result is that the answer is dropped by any sane client. TCP works without problem.
This strongly suggests knot-resolver is not implementing IP_PKTINFO in its UDP handler to retrieve the correct source IP when binding to ANY. https://blog.powerdns.com/2012/10/08/on-binding-datagram-udp-sockets-to-the-any-addresses/
Interestingly, Knot does this correctly instead. https://github.com/CZ-NIC/knot/blob/2efb723feb03f3a0354f7945b8b89a966a83464b/src/knot/server/udp-handler.c