Update MDNS library with query support

[mikee47]

Add Basic_Mdns sample to demonstrate usage

TODO:

• Why are queries not visible in Wireshark? AP must be disabled.
• Add support for list of queries - at present only one question may be posed
• Add support for queries so that callback can provide responder functionality
• Move into separate library submodule (it's optional and will likely grow)

[mikee47]

Like the SSDP server the Finder requires two UDP ports, one to listen and another to send. Few things to note here:

• Callback gets all incoming messages, not just the requested ones
• The responder will almost certainly not work whilst a Finder instances is active
• Only one query is supported at present. This should be expanded to provide a list of queries

The responder part should be rewritten along the same lines as the finder, sharing common code, etc. That will provide a common code base for all architectures and provide more flexiblility. (Another PR)

[slaff]

@mikee47 Can you check the failing CI build?

[mikee47]

Yep, just reverting some changes which don't work on ancient compiler.
Also testing on ESP8266... looks OK.

[mikee47]

OK, so running on ESP8266 responses come in OK but cannot see the outgoing queries in Wireshark. I'm using the SSDP server code as a reference and failing to spot the problem!

[slaff]

@mikee47 Ping me when this PR is ready for testing.

[mikee47]

@slaff OK ready for testing.

[mikee47]

@slaff This has grown a little, perhaps it should be in a separate library?

[mikee47]

I've been unable to get discovery working in host emulator under Linux. Likely I need to adjust the bridge configuration - any ideas?

[mikee47]

NB. Working in WSL2, so perhaps related. Here's my network info:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: bond0: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether c6:fe:c6:79:8a:2e brd ff:ff:ff:ff:ff:ff
3: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 5e:37:df:54:df:d3 brd ff:ff:ff:ff:ff:ff
4: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:15:5d:8f:24:53 brd ff:ff:ff:ff:ff:ff
    inet 172.29.167.48/20 brd 172.29.175.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::215:5dff:fe8f:2453/64 scope link
       valid_lft forever preferred_lft forever
5: sit0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN group default qlen 1000
    link/sit 0.0.0.0 brd 0.0.0.0
6: tap0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether ba:a8:68:07:08:fe brd ff:ff:ff:ff:ff:ff
    inet 192.168.13.1/24 scope global tap0
       valid_lft forever preferred_lft forever
    inet6 fe80::b8a8:68ff:fe07:8fe/64 scope link
       valid_lft forever preferred_lft forever

[slaff]

@mikee47 This PR looks good to me. Do you plan to add more changes or I should merge it as it is?

[mikee47]

@slaff All done thanks

[mikee47]

@slaff Spotted one minor bug in the code, further updates will arrive in responder

[slaff]

Spotted one minor bug in the code, further updates will arrive in responder

Ping me when ready.

[mikee47]

@slaff OK rebased/tidied, plus relevant commits from the responder branch.