Ignore superfluous T38_FIELD_HDLC_SIG_END sent by some implementations

Ignore T38_FIELD_HDLC_SIG_END when received following a
T38_FIELD_HDLC_FCS_OK_SIG_END or T38_FIELD_HDLC_FCS_BAD_SIG_END

Author: pfournier

src/t31.c

@@ -643,8 +643,10 @@ static int process_rx_data(t38_core_state_t *t, void *user_data, int data_type,
         /*endif*/
         /* Some T.38 implementations send multiple T38_FIELD_HDLC_SIG_END messages, in IFP packets with
            incrementing sequence numbers, which are actually repeats. They get through to this point because
-           of the incrementing sequence numbers. We need to filter them here in a context sensitive manner. */
-        if (t->current_rx_data_type != data_type  ||  t->current_rx_field_type != field_type)
+           of the incrementing sequence numbers. Some others send T38_FIELD_HDLC_SIG_END following a
+           T38_FIELD_HDLC_FCS_OK_SIG_END or T38_FIELD_HDLC_FCS_BAD_SIG_END. We need to filter them here
+           in a context sensitive manner. */
+        if (t->current_rx_data_type != data_type  ||  (t->current_rx_field_type != field_type && t->current_rx_field_type != T38_FIELD_HDLC_FCS_OK_SIG_END && t->current_rx_field_type != T38_FIELD_HDLC_FCS_BAD_SIG_END))
         {
             /* WORKAROUND: At least some Mediatrix boxes have a bug, where they can send this message at the
                            end of non-ECM data. We need to tolerate this. We use the generic receive complete

src/t38_gateway.c

@@ -1308,8 +1308,10 @@ static int process_rx_data(t38_core_state_t *t, void *user_data, int data_type,
         /*endif*/
         /* Some T.38 implementations send multiple T38_FIELD_HDLC_SIG_END messages, in IFP packets with
            incrementing sequence numbers, which are actually repeats. They get through to this point because
-           of the incrementing sequence numbers. We need to filter them here in a context sensitive manner. */
-        if (t->current_rx_data_type != data_type  ||  t->current_rx_field_type != field_type)
+           of the incrementing sequence numbers. Some others send T38_FIELD_HDLC_SIG_END following a
+           T38_FIELD_HDLC_FCS_OK_SIG_END or T38_FIELD_HDLC_FCS_BAD_SIG_END. We need to filter them here
+           in a context sensitive manner. */
+        if (t->current_rx_data_type != data_type  ||  (t->current_rx_field_type != field_type && t->current_rx_field_type != T38_FIELD_HDLC_FCS_OK_SIG_END && t->current_rx_field_type != T38_FIELD_HDLC_FCS_BAD_SIG_END))
         {
             if (hdlc_buf->contents != (data_type | FLAG_DATA))
             {

src/t38_terminal.c

@@ -534,8 +534,10 @@ static int process_rx_data(t38_core_state_t *t, void *user_data, int data_type,
         /*endif*/
         /* Some T.38 implementations send multiple T38_FIELD_HDLC_SIG_END messages, in IFP packets with
            incrementing sequence numbers, which are actually repeats. They get through to this point because
-           of the incrementing sequence numbers. We need to filter them here in a context sensitive manner. */
-        if (t->current_rx_data_type != data_type  ||  t->current_rx_field_type != field_type)
+           of the incrementing sequence numbers. Some others send T38_FIELD_HDLC_SIG_END following a
+           T38_FIELD_HDLC_FCS_OK_SIG_END or T38_FIELD_HDLC_FCS_BAD_SIG_END. We need to filter them here
+           in a context sensitive manner. */
+        if (t->current_rx_data_type != data_type  ||  (t->current_rx_field_type != field_type && t->current_rx_field_type != T38_FIELD_HDLC_FCS_OK_SIG_END && t->current_rx_field_type != T38_FIELD_HDLC_FCS_BAD_SIG_END))
         {
             /* WORKAROUND: At least some Mediatrix boxes have a bug, where they can send this message at the
                            end of non-ECM data. We need to tolerate this. We use the generic receive complete