l2cap: Fix double disconnect issue

It might happen that we get into situation that host will try to
disconnect same channel couple times e.g when receiveing many
corrupted packets.

This patch make sure that host will send l2cap disconnect command only
once.

Author: rymanluk

nimble/host/src/ble_l2cap_priv.h

@@ -105,6 +105,7 @@ typedef int ble_l2cap_tx_fn(struct ble_hs_conn *conn,
                             struct ble_l2cap_chan *chan);
 
 #define BLE_L2CAP_CHAN_F_TXED_MTU       0x01    /* We have sent our MTU. */
+#define BLE_L2CAP_CHAN_F_DISCONNECTING  0x02    /* We have sent L2CAP Disconnect. */
 
 SLIST_HEAD(ble_l2cap_chan_list, ble_l2cap_chan);
 

nimble/host/src/ble_l2cap_sig.c

@@ -1640,6 +1640,10 @@ ble_l2cap_sig_disconnect(struct ble_l2cap_chan *chan)
     struct ble_l2cap_sig_proc *proc;
     int rc;
 
+    if (chan->flags & BLE_L2CAP_CHAN_F_DISCONNECTING) {
+        return 0;
+    }
+
     proc = ble_l2cap_sig_proc_alloc();
     if (proc == NULL) {
         return BLE_HS_ENOMEM;
@@ -1661,6 +1665,10 @@ ble_l2cap_sig_disconnect(struct ble_l2cap_chan *chan)
     req->scid = htole16(chan->scid);
 
     rc = ble_l2cap_sig_tx(proc->conn_handle, txom);
+    /* Mark channel as disconnecting */
+    if (rc == 0) {
+        chan->flags |= BLE_L2CAP_CHAN_F_DISCONNECTING;
+    }
 
 done:
     ble_l2cap_sig_process_status(proc, rc);