net.c: Call nack handler for badly formatted response packet

If a response packet is received that is badly formatted, invoke the
nack handler (if defined) with COAP_NACK_BAD_RESPONSE so that the
requestor knows there is an issue, rather than timing out.

However, if the response packet is so badly formatted, or it is not
possible to find the requesting packet, then this nack event will not
trigger, but an event is triggered with COAP_EVENT_BAD_PACKET.

examples/coap-client.c

@@ -360,6 +360,7 @@ event_handler(coap_session_t *session COAP_UNUSED,
   case COAP_EVENT_XMIT_BLOCK_FAIL:
   case COAP_EVENT_SERVER_SESSION_NEW:
   case COAP_EVENT_SERVER_SESSION_DEL:
+  case COAP_EVENT_BAD_PACKET:
   default:
     break;
   }
@@ -381,6 +382,7 @@ nack_handler(coap_session_t *session COAP_UNUSED,
     quit = 1;
     break;
   case COAP_NACK_ICMP_ISSUE:
+  case COAP_NACK_BAD_RESPONSE:
   default:
     ;
   }

examples/coap-server.c

@@ -1645,6 +1645,7 @@ proxy_event_handler(coap_session_t *session,
   case COAP_EVENT_XMIT_BLOCK_FAIL:
   case COAP_EVENT_SERVER_SESSION_NEW:
   case COAP_EVENT_SERVER_SESSION_DEL:
+  case COAP_EVENT_BAD_PACKET:
   default:
     break;
   }
@@ -1788,6 +1789,7 @@ proxy_nack_handler(coap_session_t *session,
     remove_proxy_association(session, 1);
     break;
   case COAP_NACK_ICMP_ISSUE:
+  case COAP_NACK_BAD_RESPONSE:
   default:
     break;
   }

include/coap3/coap_event.h

@@ -91,7 +91,13 @@ typedef enum {
  * The session will still contain valid data when the event handler is
  * called.
  */
-  COAP_EVENT_SERVER_SESSION_DEL = 0x4002
+  COAP_EVENT_SERVER_SESSION_DEL = 0x4002,
+
+/*
+ * Received packet formatting errors
+ */
+  /** Triggered when badly formatted packet received */
+  COAP_EVENT_BAD_PACKET         = 0x5001
 
 } coap_event_t;
 

include/coap3/coap_io.h

@@ -71,7 +71,8 @@ typedef enum {
   COAP_NACK_NOT_DELIVERABLE,
   COAP_NACK_RST,
   COAP_NACK_TLS_FAILED,
-  COAP_NACK_ICMP_ISSUE
+  COAP_NACK_ICMP_ISSUE,
+  COAP_NACK_BAD_RESPONSE
 } coap_nack_reason_t;
 
 #endif /* COAP_IO_H_ */

man/coap_handler.txt.in

@@ -144,6 +144,7 @@ COAP_NACK_NOT_DELIVERABLE
 COAP_NACK_RST
 COAP_NACK_TLS_FAILED
 COAP_NACK_ICMP_ISSUE
+COAP_NACK_BAD_RESPONSE
 ----
 
 _sent_ can be NULL.  _mid_ can be used for determing which is the transmitting
@@ -217,6 +218,10 @@ COAP_EVENT_XMIT_BLOCK_FAIL    0x3002
  */
 COAP_EVENT_SERVER_SESSION_NEW 0x4001
 COAP_EVENT_SERVER_SESSION_DEL 0x4002
+/**
+ * Unrecognizable received packet events
+ */
+COAP_EVENT_BAD_PACKET         0x5001
 ----
 
 EXAMPLES

src/net.c

@@ -2054,6 +2054,7 @@ coap_handle_dgram(coap_context_t *ctx, coap_session_t *session,
     goto error;
 
   if (!coap_pdu_parse(session->proto, msg, msg_len, pdu)) {
+    coap_handle_event(session->context, COAP_EVENT_BAD_PACKET, session);
     coap_log(LOG_WARNING, "discard malformed PDU\n");
     goto error;
   }
@@ -3163,6 +3164,7 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
   coap_pdu_t *response;
   coap_opt_filter_t opt_filter;
   int is_ping_rst;
+  int packet_is_bad = 0;
 
   if (LOG_DEBUG <= coap_get_log_level()) {
     /* FIXME: get debug to work again **
@@ -3189,8 +3191,10 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
           /* Flush out any entries on session->delayqueue */
           coap_session_connected(session);
       }
-      if (coap_option_check_critical(session, pdu, &opt_filter) == 0)
+      if (coap_option_check_critical(session, pdu, &opt_filter) == 0) {
+        packet_is_bad = 1;
         goto cleanup;
+      }
 
 #if COAP_SERVER_SUPPORT
       /* if sent code was >= 64 the message might have been a
@@ -3271,6 +3275,7 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
       coap_remove_from_queue(&context->sendqueue, session, pdu->mid, &sent);
       /* check for unknown critical options */
       if (coap_option_check_critical(session, pdu, &opt_filter) == 0) {
+        packet_is_bad = 1;
         coap_send_rst(session, pdu);
         goto cleanup;
       }
@@ -3278,7 +3283,7 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
 
     case COAP_MESSAGE_CON:        /* check for unknown critical options */
       if (coap_option_check_critical(session, pdu, &opt_filter) == 0) {
-
+        packet_is_bad = 1;
         if (COAP_PDU_IS_REQUEST(pdu)) {
           response =
             coap_new_error_response(pdu, COAP_RESPONSE_CODE(402), &opt_filter);
@@ -3322,6 +3327,8 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
       if (context->ping_handler) {
         context->ping_handler(session, pdu, pdu->mid);
       }
+    } else {
+      packet_is_bad = 1;
     }
     coap_log(LOG_DEBUG, "dropped message with invalid code (%d.%02d)\n",
              COAP_RESPONSE_CLASS(pdu->code),
@@ -3345,6 +3352,16 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
   }
 
 cleanup:
+  if (packet_is_bad) {
+    if (sent) {
+      if (context->nack_handler) {
+        context->nack_handler(session, sent->pdu, COAP_NACK_BAD_RESPONSE, sent->id);
+      }
+    }
+    else {
+      coap_handle_event(context, COAP_EVENT_BAD_PACKET, session);
+    }
+  }
   coap_delete_node(sent);
 }