fix: harden tcp bridge reconnect handling

App/tcp_client.c

@@ -7,6 +7,8 @@
 
 #include "main.h"
 
+#include "SEGGER_RTT.h"
+
 #include "lwip/ip_addr.h"
 #include "lwip/pbuf.h"
 #include "lwip/tcp.h"
@@ -85,11 +87,15 @@ static err_t tcp_client_on_sent(void *arg, struct tcp_pcb *pcb, u16_t len)
 static void tcp_client_on_err(void *arg, err_t err)
 {
     tcp_client_ctx_t *ctx = (tcp_client_ctx_t *)arg;
-    (void)err;
+    if (ctx == NULL) {
+        return;
+    }
+
     ctx->pcb = NULL;
     ctx->status.state = TCP_CLIENT_STATE_DISCONNECTED;
     ctx->status.errors++;
     ctx->next_retry_ms = HAL_GetTick() + ctx->config.reconnect_interval_ms;
+    SEGGER_RTT_printf(0, "TCP client error=%d, reconnect scheduled\r\n", (int)err);
 }
 
 static err_t tcp_client_on_connected(void *arg, struct tcp_pcb *pcb, err_t err)
@@ -101,11 +107,17 @@ static err_t tcp_client_on_connected(void *arg, struct tcp_pcb *pcb, err_t err)
         ctx->status.state = TCP_CLIENT_STATE_DISCONNECTED;
         ctx->status.errors++;
         ctx->next_retry_ms = HAL_GetTick() + ctx->config.reconnect_interval_ms;
+        SEGGER_RTT_printf(0, "TCP client connect callback failed err=%d\r\n", (int)err);
         return err;
     }
 
     ctx->pcb = pcb;
     ctx->status.state = TCP_CLIENT_STATE_CONNECTED;
+    SEGGER_RTT_printf(0,
+                      "TCP client connected to %u.%u.%u.%u:%u\r\n",
+                      ctx->config.server_ip[0], ctx->config.server_ip[1],
+                      ctx->config.server_ip[2], ctx->config.server_ip[3],
+                      ctx->config.server_port);
     tcp_nagle_disable(pcb);
     tcp_arg(pcb, ctx);
     tcp_recv(pcb, tcp_client_on_recv);
@@ -147,6 +159,8 @@ int tcp_client_connect(void)
     pcb = tcp_new_ip_type(IPADDR_TYPE_V4);
     if (pcb == NULL) {
         g_client.status.errors++;
+        g_client.status.state = TCP_CLIENT_STATE_ERROR;
+        SEGGER_RTT_WriteString(0, "TCP client connect failed: no PCB\r\n");
         return -1;
     }
 
@@ -157,6 +171,7 @@ int tcp_client_connect(void)
             g_client.status.state = TCP_CLIENT_STATE_DISCONNECTED;
             g_client.status.errors++;
             g_client.next_retry_ms = HAL_GetTick() + g_client.config.reconnect_interval_ms;
+            SEGGER_RTT_printf(0, "TCP client bind failed err=%d\r\n", (int)err);
             return -1;
         }
     }
@@ -169,16 +184,24 @@ int tcp_client_connect(void)
 
     g_client.status.state = TCP_CLIENT_STATE_CONNECTING;
     tcp_arg(pcb, &g_client);
+    tcp_err(pcb, tcp_client_on_err);
     err = tcp_connect(pcb, &remote_addr, g_client.config.server_port, tcp_client_on_connected);
     if (err != ERR_OK) {
+        tcp_err(pcb, NULL);
         tcp_abort(pcb);
         g_client.status.state = TCP_CLIENT_STATE_DISCONNECTED;
         g_client.status.errors++;
         g_client.next_retry_ms = HAL_GetTick() + g_client.config.reconnect_interval_ms;
+        SEGGER_RTT_printf(0, "TCP client connect start failed err=%d\r\n", (int)err);
         return -1;
     }
 
     g_client.pcb = pcb;
+    SEGGER_RTT_printf(0,
+                      "TCP client connecting to %u.%u.%u.%u:%u\r\n",
+                      g_client.config.server_ip[0], g_client.config.server_ip[1],
+                      g_client.config.server_ip[2], g_client.config.server_ip[3],
+                      g_client.config.server_port);
     return 0;
 }
 
@@ -194,6 +217,7 @@ int tcp_client_disconnect(void)
     }
 
     g_client.status.state = TCP_CLIENT_STATE_DISCONNECTED;
+    SEGGER_RTT_WriteString(0, "TCP client disconnected\r\n");
     return 0;
 }
 
@@ -288,7 +312,11 @@ void tcp_client_poll(void)
 {
     uint32_t now;
 
-    if (!g_client.config.auto_reconnect || g_client.pcb != NULL) {
+    if (!g_client.config.auto_reconnect || tcp_client_is_connected()) {
+        return;
+    }
+
+    if ((g_client.pcb != NULL) && (g_client.status.state == TCP_CLIENT_STATE_CONNECTING)) {
         return;
     }
 
@@ -296,6 +324,9 @@ void tcp_client_poll(void)
     if (now >= g_client.next_retry_ms) {
         g_client.status.reconnect_count++;
         g_client.next_retry_ms = now + g_client.config.reconnect_interval_ms;
+        SEGGER_RTT_printf(0,
+                          "TCP client reconnect attempt %lu\r\n",
+                          g_client.status.reconnect_count);
         (void)tcp_client_connect();
     }
 }

App/tcp_server.c

@@ -8,6 +8,8 @@
 #include "lwip/pbuf.h"
 #include "lwip/tcp.h"
 
+#include "SEGGER_RTT.h"
+
 #include <string.h>
 
 typedef struct {
@@ -49,6 +51,7 @@ static err_t tcp_server_on_recv(void *arg, struct tcp_pcb *pcb, struct pbuf *p,
         }
         ctx->client_pcb = NULL;
         ctx->status.state = TCP_SERVER_STATE_LISTENING;
+        SEGGER_RTT_WriteString(0, "TCP server peer disconnected\r\n");
         return ERR_OK;
     }
 
@@ -85,6 +88,7 @@ static void tcp_server_on_err(void *arg, err_t err)
     ctx->client_pcb = NULL;
     ctx->status.state = TCP_SERVER_STATE_LISTENING;
     ctx->status.errors++;
+    SEGGER_RTT_printf(0, "TCP server connection error=%d\r\n", (int)err);
 }
 
 static err_t tcp_server_on_accept(void *arg, struct tcp_pcb *newpcb, err_t err)
@@ -103,6 +107,7 @@ static err_t tcp_server_on_accept(void *arg, struct tcp_pcb *newpcb, err_t err)
     ctx->client_pcb = newpcb;
     ctx->status.state = TCP_SERVER_STATE_CONNECTED;
     ctx->status.connections++;
+    SEGGER_RTT_WriteString(0, "TCP server client connected\r\n");
 
     tcp_nagle_disable(newpcb);
 
@@ -158,6 +163,7 @@ int tcp_server_start(void)
     tcp_arg(g_server.listen_pcb, &g_server);
     tcp_accept(g_server.listen_pcb, tcp_server_on_accept);
     g_server.status.state = TCP_SERVER_STATE_LISTENING;
+    SEGGER_RTT_printf(0, "TCP server listening on %u\r\n", g_server.config.port);
     return 0;
 }