fix(usbip): Try to handle UNLINK behavior

components/USBIP/usbip_defs.h

@@ -189,6 +189,7 @@ typedef struct
 typedef struct
 {
     int32_t status;
+    uint8_t padding[24]; // Linux only. For usbip-win, it ignores this field.
 } __attribute__((packed)) usbip_stage2_header_ret_unlink;
 
 /**

main/DAP_handle.c

@@ -1,10 +1,11 @@
 /**
  * @file DAP_handle.c
  * @brief Handle DAP packets and transaction push
- * @version 0.4
+ * @version 0.5
  * @change: 2020.02.04 first version
  *          2020.11.11 support WinUSB mode
  *          2021.02.17 support SWO
+ *          2021.10.03 try to handle unlink behavior
  *
  * @copyright Copyright (c) 2021
  *
@@ -266,3 +267,37 @@ int fast_reply(uint8_t *buf, uint32_t length)
     }
     return 0;
 }
+
+void handle_dap_unlink()
+{
+    // `USBIP_CMD_UNLINK` means calling `usb_unlink_urb()` or `usb_kill_urb()`.
+    // Note that execution of an URB is inherently an asynchronous operation, and there may be
+    // synchronization problems in the following solutions.
+
+    // One of the reasons this happens is that the host wants to abort the URB transfer operation
+    // as soon as possible. USBIP network fluctuations will also cause this error, but I don't know
+    // whether this is the main reason.
+
+    // Unlink may be applied to zero length URB of "DIR_IN", or a URB containing data.
+    // In the case of unlink, for the new "DIR_IN" request, it may always return an older response,
+    // which will lead to panic. This code is a compromise for eliminating the lagging response
+    // caused by UNLINK. It will clean up the buffers that may have data for return to the host.
+    // In general, we assume that there is at most one piece of data that has not yet been returned.
+    if (dap_respond > 0)
+    {
+        DapPacket_t *item;
+        size_t packetSize = 0;
+        item = (DapPacket_t *)xRingbufferReceiveUpTo(dap_dataOUT_handle, &packetSize,
+                                                     pdMS_TO_TICKS(10), DAP_HANDLE_SIZE);
+        if (packetSize == DAP_HANDLE_SIZE)
+        {
+            if (xSemaphoreTake(data_response_mux, portMAX_DELAY) == pdTRUE)
+            {
+                --dap_respond;
+                xSemaphoreGive(data_response_mux);
+            }
+
+            vRingbufferReturnItem(dap_dataOUT_handle, (void *)item);
+        }
+    }
+}

main/DAP_handle.h

@@ -6,6 +6,7 @@
 void handle_dap_data_request(usbip_stage2_header *header, uint32_t length);
 void handle_dap_data_response(usbip_stage2_header *header);
 void handle_swo_trace_response(usbip_stage2_header *header);
+void handle_dap_unlink();
 
 int fast_reply(uint8_t *buf, uint32_t length);
 

main/usbip_server.c

@@ -375,8 +375,10 @@ void send_stage2_submit_data_fast(usbip_stage2_header *req_header, const void *c
 static void handle_unlink(usbip_stage2_header *header)
 {
     os_printf("s2 handling cmd unlink...\r\n");
+    handle_dap_unlink();
     send_stage2_unlink(header);
 }
+
 static void send_stage2_unlink(usbip_stage2_header *req_header)
 {
 
@@ -385,7 +387,11 @@ static void send_stage2_unlink(usbip_stage2_header *req_header)
 
     memset(&(req_header->u.ret_unlink), 0, sizeof(usbip_stage2_header_ret_unlink));
 
-    // req_header.u.ret_unlink.status = 0;
+    // To be more precise, the value is `-ECONNRESET`, but usbip-win only cares if it is a
+    // non zero value. A non-zero value indicates that our UNLINK operation was "successful",
+    // but the host driver's may behave differently, or may even ignore this state. For consistent
+    // behavior, we use non-zero value here. See also comments regarding `handle_dap_unlink()`.
+    req_header->u.ret_unlink.status = -1;
 
     pack(req_header, sizeof(usbip_stage2_header));
 

sdkconfig

@@ -278,18 +278,18 @@ CONFIG_LWIP_MAX_LISTENING_TCP=8
 CONFIG_LWIP_TCP_MAXRTX=12
 CONFIG_LWIP_TCP_SYNMAXRTX=6
 CONFIG_LWIP_TCP_MSS=1460
-CONFIG_LWIP_TCP_TMR_INTERVAL=250
+CONFIG_LWIP_TCP_TMR_INTERVAL=100
 CONFIG_LWIP_TCP_MSL=60000
 CONFIG_LWIP_TCP_SND_BUF_DEFAULT=11680
 CONFIG_LWIP_TCP_WND_DEFAULT=10240
 CONFIG_LWIP_TCP_RECVMBOX_SIZE=16
 CONFIG_LWIP_TCP_QUEUE_OOSEQ=y
-# CONFIG_LWIP_TCP_SACK_OUT is not set
+CONFIG_LWIP_TCP_SACK_OUT=y
 # CONFIG_LWIP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES is not set
 CONFIG_LWIP_TCP_OVERSIZE_MSS=y
 # CONFIG_LWIP_TCP_OVERSIZE_QUARTER_MSS is not set
 # CONFIG_LWIP_TCP_OVERSIZE_DISABLE is not set
-CONFIG_LWIP_TCP_RTO_TIME=3000
+CONFIG_LWIP_TCP_RTO_TIME=1500
 CONFIG_LWIP_MAX_UDP_PCBS=4
 CONFIG_LWIP_UDP_RECVMBOX_SIZE=6
 CONFIG_LWIP_TCPIP_TASK_STACK_SIZE=4096