Bugzilla – Bug 595
PHY may start receive packet inside SIFS
Last modified: 2009-06-26 09:26:37 UTC
Created attachment 467 [details] Proposed fix PHY passes information to DcfManager about PHY events, and DCF manager must catch situation, when PHY starts to transmit and m_rxing is true. This may occur only after the following steps: 1. PHY has started to receive a packet inside SIFS. 2. MacLow has started to transmit an ACK frame (or any other frame) when SIFS has expired. 3. PHY has started to transmit this ACK frame and has cancelled previously started receiving: if (m_state->IsStateSync ()) { m_endSyncEvent.Cancel (); } and has not tell anything to DcfManager. 4. IsBusy method of DcfManager decides that the medium is busy (because m_rxing was not unset) 5. Next transmission causes collision at DcfManager layer due to IsBusy () (see DcfManager::RequestAccess) The idea to solve this problem is to check m_rxing flag when running DcfManager::NotifyTxStartNow (see patch)
this looks right, but, as usual for changes to the Dcf code, I would like to see an associated testcase. Could you do this for me ?
OK
Created attachment 475 [details] Testcace added Added a test which cheks that RX inside SIFS was managed properly.
changeset 9b07308116ed
Created attachment 490 [details] NS_ASSERT fixed Fixed NS_ASSERT: '<' replaced with '<='
This assert has failed, but after replacing '<' with '<=' everything has become OK. this assert was added, because cancel RX may occur only when we cancel RX inside SIFS
changeset e66fc1287031