fix(net): reset ARP state on link changes

Core/Src/main.c

@@ -27,6 +27,7 @@
 #include "ethernetif.h"
 #include "ch390_runtime.h"
 #include "lwip/init.h"
+#include "lwip/etharp.h"
 #include "lwip/timeouts.h"
 #include "tcp_client.h"
 #include "tcp_server.h"
@@ -41,6 +42,9 @@
 #define APP_TCP_TO_UART_CHUNK_SIZE  128u
 #define STACK_GUARD_WORD            0xA5A5A5A5u
 #define APP_HEALTH_CHECK_INTERVAL_MS 5000u
+#define APP_LINK_SETTLE_MS          1500u
+#define APP_ARP_ANNOUNCE_INTERVAL_MS 500u
+#define APP_ARP_ANNOUNCE_COUNT      3u
 /* USER CODE END PD */
 
 /* Private variables ---------------------------------------------------------*/
@@ -51,6 +55,10 @@ volatile uint8_t g_uart1_rx_probe_byte = 0u;
 static uint8_t g_stack_guard_reported = 0u;
 static uint8_t g_mux_response_frame[272];
 static uint8_t g_links_started = 0u;
+static uint8_t g_link_was_up = 0u;
+static uint8_t g_arp_announces_sent = 0u;
+static uint32_t g_link_up_tick = 0u;
+static uint32_t g_last_arp_announce_tick = 0u;
 /* USER CODE END PV */
 
 /* Private function prototypes -----------------------------------------------*/
@@ -198,10 +206,25 @@ static void App_ConfigureLinks(const device_config_t *cfg)
 static void App_StartLinksIfNeeded(void)
 {
     int any_failed;
+    uint32_t now;
 
     if ((g_links_started != 0u) || !netif_is_link_up(&ch390_netif)) {
         return;
     }
+    now = HAL_GetTick();
+    if ((uint32_t)(now - g_link_up_tick) < APP_LINK_SETTLE_MS) {
+        return;
+    }
+
+    while (g_arp_announces_sent < APP_ARP_ANNOUNCE_COUNT) {
+        if ((g_arp_announces_sent != 0u) &&
+            ((uint32_t)(now - g_last_arp_announce_tick) < APP_ARP_ANNOUNCE_INTERVAL_MS)) {
+            return;
+        }
+        (void)etharp_gratuitous(&ch390_netif);
+        g_arp_announces_sent++;
+        g_last_arp_announce_tick = now;
+    }
 
     any_failed = 0;
     for (uint8_t i = 0; i < TCP_SERVER_INSTANCE_COUNT; ++i) {
@@ -243,6 +266,36 @@ static void App_StopLinksIfNeeded(void)
     g_links_started = 0u;
 }
 
+static void App_HandleLinkTransition(void)
+{
+    uint8_t link_up = netif_is_link_up(&ch390_netif) ? 1u : 0u;
+
+    if (link_up == g_link_was_up) {
+        return;
+    }
+
+    g_link_was_up = link_up;
+    if (link_up != 0u) {
+        g_link_up_tick = HAL_GetTick();
+        g_arp_announces_sent = 0u;
+        g_last_arp_announce_tick = 0u;
+        etharp_cleanup_netif(&ch390_netif);
+        SEGGER_RTT_WriteString(0, "NET link up, settling before TCP start\r\n");
+    } else {
+        for (uint8_t i = 0; i < TCP_CLIENT_INSTANCE_COUNT; ++i) {
+            (void)tcp_client_disconnect(i);
+        }
+        for (uint8_t i = 0; i < TCP_SERVER_INSTANCE_COUNT; ++i) {
+            (void)tcp_server_stop(i);
+        }
+        etharp_cleanup_netif(&ch390_netif);
+        g_links_started = 0u;
+        g_arp_announces_sent = 0u;
+        g_last_arp_announce_tick = 0u;
+        SEGGER_RTT_WriteString(0, "NET link down, cleared TCP and ARP state\r\n");
+    }
+}
+
 static void App_Init(void)
 {
     const device_config_t *cfg;
@@ -648,10 +701,13 @@ static void App_Poll(void)
     ethernetif_poll();
     ethernetif_check_link();
     sys_check_timeouts();
+    App_HandleLinkTransition();
     App_StopLinksIfNeeded();
     App_StartLinksIfNeeded();
     tcp_server_poll();
+    if (g_links_started != 0u) {
         tcp_client_poll();
+    }
     uart_trans_poll();
     StackGuard_Check();
     config_poll();

MDK-ARM/keil-build-viewer-record.txt

@@ -5,7 +5,7 @@
       3958          0        591          8       1240          0   config.o
          8          0          0          0          0          0   def.o
        124          0          0          0          0          0   dma.o
-      1772          0          0          1        240          0   etharp.o
+      1816          0          0          1        240          0   etharp.o
        238          0         12          0          0          0   ethernet.o
        178          0          0          0         48          0   ethernetif.o
        246          0          0          0          0          0   flash_param.o
@@ -17,7 +17,7 @@
        778          0          0          2          0          0   ip4.o
         46          0          4          0          0          0   ip4_addr.o
         44          0          0          0         12          0   iwdg.o
-      3264          0        300         12        272          0   main.o
+      3532          0        300         20        272          0   main.o
        828          0          0         12       4115          0   mem.o
        196          0        244         32       6464          0   memp.o
        582          0          0         12          0          0   netif.o
@@ -57,8 +57,8 @@ Memory Map of the image
 
 	Load Region LR_IROM1 
 
-		Execution Region ER_IROM1 (Exec base: 0x08000000, Size: 0x0000DFA0, Max: 0x00010000, END)
+		Execution Region ER_IROM1 (Exec base: 0x08000000, Size: 0x0000E0B8, Max: 0x00010000, END)
 
-		Execution Region RW_IRAM1 (Exec base: 0x20000000, Size: 0x00004FD8, Max: 0x00005000, END)
+		Execution Region RW_IRAM1 (Exec base: 0x20000000, Size: 0x00004FE0, Max: 0x00005000, END)
 
 Image component sizes