Tested also with MP 1.23.0 : not resolved

On rp2 MDNS is enabled to be provided by lwip: https://github.com/micropython/micropython/blob/master/ports/rp2/lwip_inc/lwipopts.h#L35. Maybe you want to compile your own firmware with that flag disabled?

I am looking for a fix for this as well. I would prefer not to build my own custom firmware and use something like slimdns. I will have more of a look at the code to see why LWIP is not working once I get a working local build.

@felixdoerre

On rp2 MDNS is enabled to be provided by lwip: https://github.com/micropython/micropython/blob/master/ports/rp2/lwip_inc/lwipopts.h#L35. Maybe you want to compile your own firmware with that flag disabled?

But I think the point being made is that LWIP is not providing a working mDNS implementation on rp2 and yet is holding onto the port. Could that perhaps be a result of a build order of operations with the LWIP library and the rp2 lwipopts.h? Or some missing glue code?

It is fair if mDNS support is not yet implemented for the rp2 port. But it seems very much like a bug for rp2 lwipopts.h to define the following if mDNS support is not properly included/implemented in the fw:

#define LWIP_DNS_SUPPORT_MDNS_QUERIES   1
#define LWIP_MDNS_RESPONDER             1

I also notice that the following lines are not included in the rp2 mpconfigport.h file:

#ifndef MICROPY_HW_ENABLE_MDNS_QUERIES
#define MICROPY_HW_ENABLE_MDNS_QUERIES      (1)
#endif

#ifndef MICROPY_HW_ENABLE_MDNS_RESPONDER
#define MICROPY_HW_ENABLE_MDNS_RESPONDER    (1)
#endif

The ESP port has code in network_wlan.c that specifically calls mDNS initialization and provides some handling code. The rp2 port does not seem to have similar code.

@felixdoerre Looking over the codebase some more I think I might see the issue. In ports/rp2/main.c:125 there is this code:

    #if MICROPY_PY_LWIP
    // lwIP doesn't allow to reinitialise itself by subsequent calls to this function
    // because the system timeout list (next_timeout) is only ever reset by BSS clearing.
    // So for now we only init the lwIP stack once on power-up.
    lwip_init();
    #if LWIP_MDNS_RESPONDER
    mdns_resp_init();
    #endif
    #endif

Per the LWIP docs, the mdns_resp_init() opens the mDNS socket/port, but mDNS is not activated on a network interface until a call to mdns_resp_add_netif() which is not called anywhere that I can find. If accurate, RP2 basically has only a partial mDNS implementation and LWIP_MDNS_RESPONDER should probably be 0 by default until/unless a complete implementation is provided.

If someone can point me to where the netif is initialized in the RP2 port I am happy to build up a PR.

@dpgeorge any comment on the default behavior? Seems like mDNS should either be fully functional or disabled by default. Happy to contribute a PR if appropriate.

Should be fixed by f96417d (although looking up mDNS on the Pico W in AP mode might not work yet).