基于STM32F769+RTOS+LwIP的Web服务器故障排查求助

Hey there, let's break down your problems step by step and work through fixes for each one:

1. Thread Priority Misalignment (Likely Root Cause) #

Your suspicion about thread priorities is spot-on—LwIP's core tcpip_thread needs top priority to handle low-level packet processing, otherwise higher-priority threads can starve it of CPU time, leading to all sorts of network weirdness. Here's how to adjust:

• Set tcpip_thread to osPriorityRealtime (or at least osPriorityHigh—make sure it's higher than your Web and DHCP threads)
• Demote your Web server thread to osPriorityNormal
• Keep DHCP thread at osPriorityBelowNormal or bump it to osPriorityNormal
• Also, double-check your ETH interrupt priority: it should be higher than all RTOS threads (e.g., set NVIC priority grouping to 4, ETH interrupt priority to 0/1) to ensure packet data gets handed off to tcpip_thread immediately.

2. DHCP Success Rate Issues #

If priority fixes don't resolve the 50% success rate, dig deeper into DHCP client behavior:

• Add debug prints to track DHCP state transitions (e.g., DHCP_DISCOVER, DHCP_OFFER, DHCP_ACK) to see where failures happen
• Increase DHCP retry counts and timeout values in your configuration (e.g., bump retry attempts from 3 to 5)
• Use a packet sniffer (like Wireshark) on your local network to verify:
  • Is the STM32 sending DHCP Discover packets?
  • Is your router sending DHCP Offer/ACK packets in response?

3. Ping Works Then Dies + accept() Never Executes #

This is almost always a sign that tcpip_thread isn't processing incoming packets properly. Try these checks:

• Validate Socket Setup: Confirm bind() returns 0 (success) and listen(sock, 2) is called with a valid backlog value (at least 1).
• LwIP Memory Configuration: In lwipopts.h, ensure these values are sufficient:
  • MEM_SIZE = 16384 (or higher)
  • MEMP_NUM_PBUF = 64
  • MEMP_NUM_TCP_PCB = 8
    Low memory will prevent new TCP connections from being created, leaving accept() blocked forever.
• Thread Stack Size: Your Web server thread needs enough stack space—increase it to 2048 bytes (default Cube values are often too small for socket operations).
• Packet Sniffer Check: Capture network traffic to see if HTTP SYN packets are reaching your STM32's IP. If you see SYNs but no SYN-ACK responses, tcpip_thread isn't handling the packets due to priority or resource issues.

4. Static IP Ping Failure #

Static IP issues usually boil down to misconfiguration or initialization order:

• Verify your static IP, subnet mask, and gateway are in the same network segment as your router/PC
• Double-check your initialization flow:

  // After tcpip_init()
  ip_addr_t ipaddr, netmask, gw;
  IP4_ADDR(&ipaddr, 192, 168, 1, 100); // Your static IP
  IP4_ADDR(&netmask, 255, 255, 255, 0);
  IP4_ADDR(&gw, 192, 168, 1, 1);
  netif_set_addr(&gnetif, &ipaddr, &netmask, &gw);
  netif_set_up(&gnetif);
  netif_set_default(&gnetif);
  

• Confirm the Ethernet PHY is linked: call HAL_ETH_GetLinkState(&heth) and ensure it returns HAL_ETH_LINK_STATE_UP
• If ping still fails, manually add an ARP entry for your gateway to rule out ARP resolution issues.

Quick Pro Tip #

Since 90% of your code comes from the official Cube example, compare your configuration files (lwipopts.h, FreeRTOSConfig.h, ETH init code) side-by-side with the original example. Small tweaks to memory sizes, priority values, or initialization steps are often the culprit.

内容的提问来源于stack exchange，提问作者xtrinch