Wiznet makers

📝 Summary: Network Issues / Questions for LWIP and Wiznet

Context:

User SteveSpencer is using MicroPython on Wiznet-equipped boards (e.g. W5100S-EVB-PICO) with RP2040 (Pico) for projects.

They also use Pico W / Pico 2 W boards as comparators. 

The issue arises around DHCP behavior—specifically the setting of a hostname in DHCP requests, and processing of hostname returned by the DHCP server.

🔍 What the Discussion Found

LWIP & Native Wiznet Stack Configuration

It was confirmed that MicroPython builds for Wiznet boards have LWIP enabled. 

However, even with LWIP enabled, some DHCP options—especially “hostname” (DHCP option 12)—are not included in DHCP request packets. 

Lack of Hostname Handling

The board does not set a hostname in DHCP discover/message.

It also does not process the hostname supplied by the DHCP server when IP is assigned. Users using dnsmasq with dhcp-host entries (to assign hostnames via DHCP) saw that their Wiznet board wasn’t recognized by this hostname in the LAN.

A Proposed Fix / Workaround

SteveSpencer edited extmod/network_wiznet5k.c in the MicroPython source: added a line netif_set_hostname(&self->netif, mod_network_hostname_data); just before dhcp_start(&self->netif). This forces setting the hostname in LWIP before DHCP starts. 

After this change, the hostname appears in DHCP server / LAN as expected. 

Broader Observations and Limitations

The issue isn't unique to the Wiznet-stack; similar behavior is seen on Pico W / Pico 2 W. So some of this may be limitations or bugs in LWIP or how MicroPython builds enable/distribute certain features. 

There was talk of upcoming code changes: Wiznet is preparing a newer “WIZNET6K” driver / update, which may improve matching behavior, or provide clearer build options to toggle between the onboard (native) IP stack vs the LWIP stack. 

✔ Key Takeaways & Implications

For Users / Developers:

If hostname in network / LAN discovery matters, current behavior (without patch) may cause confusion — the device won’t appear under the expected name.

Static or custom DNS / DHCP setups (e.g. with dnsmasq) may depend on the hostname being set properly; so this bug or missing behavior affects usability in managed LANs.

Workarounds exist via modifying the MicroPython driver; users who are comfortable building firmware or custom drivers can apply them.

For WIZnet / MicroPython / Firmware Teams:

There's a visible gap: although LWIP is enabled, not all DHCP options are properly handled or forwarded (hostname option is missing).

Opportunity to officially patch or include the hostname behavior in future releases.

Clarity in builds / configuration: enabling LWIP, enabling DHCP option12 (hostname), controlling which stack is used should be clearly documented / exposed.

The “WIZNET6K” updates mentioned may present a chance to address these issues systematically.