Remove transaction from list before callback call (#50)

In some callbacks, secure session might be removed and transactions been
freed. That leads to double freeing, and reading from freed pointer.
Transaction is now removed from list before calling callback to avoid
that.

source/coap_message_handler.c

@@ -81,14 +81,24 @@ static coap_transaction_t *transaction_create(void)
 
     return this;
 }
+
+static void transaction_free(coap_transaction_t *this)
+{
+    if (!this) {
+        return;
+    }
+
+    if (this->data_ptr) {
+        ns_dyn_mem_free(this->data_ptr);
+    }
+    ns_dyn_mem_free(this);
+}
+
 void transaction_delete(coap_transaction_t *this)
 {
     if (this) {
         ns_list_remove(&request_list, this);
-        if(this->data_ptr){
-            ns_dyn_mem_free(this->data_ptr);
-        }
-        ns_dyn_mem_free(this);
+        transaction_free(this);
     }
 
     return;
@@ -99,11 +109,12 @@ void transactions_delete_all(uint8_t *address_ptr, uint16_t port)
     coap_transaction_t *transaction = transaction_find_by_address(address_ptr, port);
 
     while (transaction) {
+        ns_list_remove(&request_list, transaction);
         if (transaction->resp_cb) {
             transaction->resp_cb(transaction->service_id, address_ptr, port, NULL);
         }
         sn_coap_protocol_delete_retransmission(coap_service_handle->coap, transaction->msg_id);
-        transaction_delete(transaction);
+        transaction_free(transaction);
         transaction = transaction_find_by_address(address_ptr, port);
     }
 }
@@ -113,17 +124,22 @@ static int8_t coap_rx_function(sn_coap_hdr_s *resp_ptr, sn_nsdl_addr_s *address_
     coap_transaction_t *this = NULL;
     (void)address_ptr;
     (void)param;
-    tr_warn("transaction was not handled");
+    tr_warn("transaction was not handled %d", resp_ptr->msg_id);
     if (!resp_ptr) {
         return -1;
     }
     if( resp_ptr->token_ptr ){
         this = transaction_find_client_by_token(resp_ptr->token_ptr);
     }
-    if (this && this->resp_cb) {
+    if (!this) {
+        return 0;
+    }
+
+    ns_list_remove(&request_list, this);
+    if (this->resp_cb) {
         this->resp_cb(this->service_id, address_ptr->addr_ptr, address_ptr->port, NULL);
     }
-    transaction_delete(this);
+    transaction_free(this);
     return 0;
 }
 
@@ -250,11 +266,12 @@ int16_t coap_message_handler_coap_msg_process(coap_msg_handler_t *handle, int8_t
             return -1;
         }
         tr_debug("Service %d, response received", this->service_id);
+        ns_list_remove(&request_list, this);
         if (this->resp_cb) {
             this->resp_cb(this->service_id, (uint8_t *)source_addr_ptr, port, coap_message);
         }
         sn_coap_parser_release_allocated_coap_msg_mem(handle->coap, coap_message);
-        transaction_delete(this);
+        transaction_free(this);
     }
 
     return 0;