wifi: Establish block ack agreement with all GCR member STAs prior to a groupcast transmission

src/wifi/model/ht/ht-frame-exchange-manager.cc

@@ -11,8 +11,10 @@
 #include "ht-configuration.h"
 
 #include "ns3/abort.h"
+#include "ns3/ap-wifi-mac.h"
 #include "ns3/assert.h"
 #include "ns3/ctrl-headers.h"
+#include "ns3/gcr-manager.h"
 #include "ns3/log.h"
 #include "ns3/mgt-action-headers.h"
 #include "ns3/recipient-block-ack-agreement.h"
@@ -134,6 +136,43 @@ HtFrameExchangeManager::NeedSetupBlockAck(Mac48Address recipient, uint8_t tid)
     return establish;
 }
 
+std::optional<Mac48Address>
+HtFrameExchangeManager::NeedSetupGcrBlockAck(const WifiMacHeader& header)
+{
+    NS_ASSERT(m_mac->GetTypeOfStation() == AP && m_apMac->UseGcr(header));
+    const auto& groupAddress = header.GetAddr1();
+
+    const auto tid = header.GetQosTid();
+    auto qosTxop = m_mac->GetQosTxop(tid);
+    const auto maxMpduSize =
+        m_mpduAggregator->GetMaxAmpduSize(groupAddress, tid, WIFI_MOD_CLASS_HT);
+    WifiContainerQueueId queueId{WIFI_QOSDATA_QUEUE, WIFI_GROUPCAST, groupAddress, tid};
+
+    for (const auto& recipients =
+             m_apMac->GetGcrManager()->GetMemberStasForGroupAddress(groupAddress);
+         const auto& nextRecipient : recipients)
+    {
+        if (auto agreement =
+                qosTxop->GetBaManager()->GetAgreementAsOriginator(nextRecipient, tid, groupAddress);
+            agreement && !agreement->get().IsReset())
+        {
+            continue;
+        }
+
+        const auto packets = qosTxop->GetWifiMacQueue()->GetNPackets(queueId);
+        const auto establish =
+            ((qosTxop->GetBlockAckThreshold() > 0 && packets >= qosTxop->GetBlockAckThreshold()) ||
+             (maxMpduSize > 0 && packets > 1));
+        NS_LOG_FUNCTION(this << groupAddress << +tid << establish);
+        if (establish)
+        {
+            return nextRecipient;
+        }
+    }
+
+    return std::nullopt;
+}
+
 bool
 HtFrameExchangeManager::SendAddBaRequest(Mac48Address dest,
                                          uint8_t tid,
@@ -356,6 +395,17 @@ HtFrameExchangeManager::SendDelbaFrame(Mac48Address addr,
     m_mac->GetQosTxop(tid)->Queue(Create<WifiMpdu>(packet, hdr));
 }
 
+uint16_t
+HtFrameExchangeManager::GetBaAgreementStartingSequenceNumber(const WifiMacHeader& header)
+{
+    // if the peeked MPDU has been already transmitted, use its sequence number
+    // as the starting sequence number for the BA agreement, otherwise use the
+    // next available sequence number
+    return header.IsRetry()
+               ? header.GetSequenceNumber()
+               : m_txMiddle->GetNextSeqNumberByTidAndAddress(header.GetQosTid(), header.GetAddr1());
+}
+
 bool
 HtFrameExchangeManager::StartFrameExchange(Ptr<QosTxop> edca, Time availableTime, bool initialFrame)
 {
@@ -384,20 +434,26 @@ HtFrameExchangeManager::StartFrameExchange(Ptr<QosTxop> edca, Time availableTime
     if (hdr.IsQosData() && !hdr.GetAddr1().IsGroup() &&
         NeedSetupBlockAck(hdr.GetAddr1(), hdr.GetQosTid()))
     {
-        // if the peeked MPDU has been already transmitted, use its sequence number
-        // as the starting sequence number for the BA agreement, otherwise use the
-        // next available sequence number
-        uint16_t startingSeq =
-            (hdr.IsRetry()
-                 ? hdr.GetSequenceNumber()
-                 : m_txMiddle->GetNextSeqNumberByTidAndAddress(hdr.GetQosTid(), hdr.GetAddr1()));
         return SendAddBaRequest(hdr.GetAddr1(),
                                 hdr.GetQosTid(),
-                                startingSeq,
+                                GetBaAgreementStartingSequenceNumber(hdr),
                                 edca->GetBlockAckInactivityTimeout(),
                                 true,
                                 availableTime);
     }
+    else if (IsGcr(m_mac, hdr))
+    {
+        if (const auto addbaRecipient = NeedSetupGcrBlockAck(hdr))
+        {
+            return SendAddBaRequest(addbaRecipient.value(),
+                                    hdr.GetQosTid(),
+                                    GetBaAgreementStartingSequenceNumber(hdr),
+                                    edca->GetBlockAckInactivityTimeout(),
+                                    true,
+                                    availableTime,
+                                    hdr.GetAddr1());
+        }
+    }
 
     // Use SendDataFrame if we can try aggregation
     if (hdr.IsQosData() && !hdr.GetAddr1().IsGroup() && !peekedItem->IsFragment() &&

src/wifi/model/ht/ht-frame-exchange-manager.h

@@ -281,6 +281,15 @@ class HtFrameExchangeManager : public QosFrameExchangeManager
      */
     virtual bool SendDataFrame(Ptr<WifiMpdu> peekedItem, Time availableTime, bool initialFrame);
 
+    /**
+     * Retrieve the starting sequence number for a BA agreement to be established.
+     *
+     * @param header the MAC header of the next data packet selected for transmission once the BA
+     * agreement is established. \return the starting sequence number for a BA agreement to be
+     * established
+     */
+    uint16_t GetBaAgreementStartingSequenceNumber(const WifiMacHeader& header);
+
     /**
      * A Block Ack agreement needs to be established with the given recipient for the
      * given TID if it does not already exist (or exists and is in state RESET) and:
@@ -295,6 +304,21 @@ class HtFrameExchangeManager : public QosFrameExchangeManager
      */
     virtual bool NeedSetupBlockAck(Mac48Address recipient, uint8_t tid);
 
+    /**
+     * A Block Ack agreement needs to be established prior to the transmission of a groupcast data
+     * packet using the GCR service if it does not already exist (or exists and is in state RESET)
+     * for all member STAs and:
+     *
+     * - the number of packets in the groupcast queue reaches the BlockAckThreshold value OR
+     * - MPDU aggregation is enabled and there is more than one groupcast packet in the queue OR
+     * - the station is a VHT station
+     *
+     * @param header the MAC header of the next groupcast data packet selected for transmission.
+     * @return the recipient of the ADDBA frame if a Block Ack agreement needs to be established,
+     * std::nullopt otherwise.
+     */
+    virtual std::optional<Mac48Address> NeedSetupGcrBlockAck(const WifiMacHeader& header);
+
     /**
      * Sends an ADDBA Request to establish a block ack agreement with STA
      * addressed by <i>recipient</i> for TID <i>tid</i>.