lwIP Integration

Overview

Use this skill to integrate lwIP by separating hardware Ethernet/Wi-Fi drivers, netif glue, memory pools, threading model, and protocol configuration. A successful port proves link, IP configuration, packet RX/TX, and resource stability under load.

When To Use

Use this skill when:

• The user wants to add or debug lwIP on bare metal, FreeRTOS, RT-Thread, Zephyr, vendor SDKs, or custom network drivers.
• The issue involves lwipopts.h, sys_arch, netif, DHCP, TCP/UDP, pbufs, memory pools, packet loss, or hard faults in networking.
• The target uses Ethernet, Wi-Fi, PPP, SLIP, or a vendor network interface.

Do not use this skill when the physical link or board interface is not proven. Use hardware-interface-debug first for PHY, RMII/MII, clocks, or wiring issues. For FreeRTOS-native TCP/IP, use freertos-plus-tcp-integration. For MQTT over lwIP, use mqtt-embedded-integration after basic connectivity works.

First Questions

Ask for:

• MCU/SoC, network interface, PHY/module, RTOS, and lwIP version.
• Driver source: vendor SDK, custom MAC driver, Wi-Fi module, or simulator.
• Threading model: NO_SYS raw API, tcpip_thread, socket/netconn API, or RTOS integration.
• lwipopts.h, memory sizes, pbuf pool settings, and enabled protocols.
• Current symptom: no link, no IP, DHCP timeout, ping fails, TCP stalls, memory exhaustion, or crash.
• Packet/log evidence: link status, IP address, ARP, ping, Wireshark, counters, or asserts.

Integration Checklist

1. Confirm link before IP.

Verify PHY/module link, MAC address, link callbacks, and carrier status before debugging DHCP or TCP.

1. Confirm netif glue.

netif_add, input path, output path, MTU, flags, hostname, and link/status callbacks must match the driver.

1. Match threading model.

Do not call raw API from arbitrary threads. Use tcpip callbacks or socket/netconn APIs according to configuration.

1. Size memory deliberately.

Check MEM_SIZE, MEMP_NUM_*, PBUF_POOL_SIZE, TCP windows, mailbox sizes, and stack sizes.

1. Implement OS abstraction if needed.

For RTOS ports, sys_arch must provide semaphores, mutexes, mailboxes, timeouts, and critical sections.

1. Verify with layered tests.

Link, static IP, ARP, ping, UDP echo, TCP connect, sustained transfer, and reconnect.

Common Failures

• DHCP fails because link callback never reports up.
• Ping fails because ARP output path or MAC address is wrong.
• TCP stalls because pbufs or mailboxes are exhausted.
• Random crashes from raw API calls outside tcpip_thread.
• Cache/DMA incoherency corrupts RX/TX buffers.
• Stack overflow in tcpip_thread or network driver task.

Verification

Before claiming lwIP works:

• State interface, RTOS mode, API style, and IP configuration.
• Confirm link status, MAC address, IP address, gateway, and netmask.
• Confirm ping or UDP/TCP test with counters.
• Report memory pool usage or at least configured pool sizes.
• If DMA/cache is involved, state cache maintenance policy.

Example

User:

lwIP DHCP 一直拿不到 IP。

Agent:

1. Asks for PHY link status, netif setup, lwipopts.h, RTOS mode, and DHCP logs.
2. Confirms link callback and RX path before changing DHCP settings.
3. Tests static IP ping to separate driver/link problems from DHCP problems.