From 58d3bde8db95c62c6565862c28e4cc22a4efb92c Mon Sep 17 00:00:00 2001
From: Stefano Avallone <stavallo@unina.it>
Date: Wed, 11 Oct 2023 18:02:15 +0200
Subject: [PATCH] wifi: CTS after ICF cannot be sent if main PHY is switching
 or operating on another link

This situation may occur when an aux PHY is not TX capable.
---
 .../model/eht/eht-frame-exchange-manager.cc   | 25 +++++++++++++++++++
 .../model/eht/eht-frame-exchange-manager.h    |  3 +++
 src/wifi/model/eht/emlsr-manager.cc           |  6 +++++
 src/wifi/model/he/he-frame-exchange-manager.h |  6 ++---
 4 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/src/wifi/model/eht/eht-frame-exchange-manager.cc b/src/wifi/model/eht/eht-frame-exchange-manager.cc
index e7182fe1a..631a8002a 100644
--- a/src/wifi/model/eht/eht-frame-exchange-manager.cc
+++ b/src/wifi/model/eht/eht-frame-exchange-manager.cc
@@ -576,6 +576,31 @@ EhtFrameExchangeManager::SendMuRts(const WifiTxParameters& txParams)
     HeFrameExchangeManager::SendMuRts(txParams);
 }
 
+void
+EhtFrameExchangeManager::SendCtsAfterMuRts(const WifiMacHeader& muRtsHdr,
+                                           const CtrlTriggerHeader& trigger,
+                                           double muRtsSnr)
+{
+    NS_LOG_FUNCTION(this << muRtsHdr << trigger << muRtsSnr);
+
+    NS_ASSERT(m_staMac);
+    if (auto emlsrManager = m_staMac->GetEmlsrManager())
+    {
+        auto mainPhy = m_staMac->GetDevice()->GetPhy(emlsrManager->GetMainPhyId());
+
+        // an aux PHY that is not TX capable may get a TXOP, release the channel and request
+        // the main PHY to switch channel. Shortly afterwards, the AP MLD may send an ICF, thus
+        // when the main PHY is scheduled to send the CTS, the main PHY may be switching channel
+        // or may be operating on another link
+        if (mainPhy->IsStateSwitching() || m_mac->GetLinkForPhy(mainPhy) != m_linkId)
+        {
+            NS_LOG_DEBUG("Main PHY is switching or operating on another link, abort sending CTS");
+            return;
+        }
+    }
+    HeFrameExchangeManager::SendCtsAfterMuRts(muRtsHdr, trigger, muRtsSnr);
+}
+
 void
 EhtFrameExchangeManager::CtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts, const WifiTxVector& txVector)
 {
diff --git a/src/wifi/model/eht/eht-frame-exchange-manager.h b/src/wifi/model/eht/eht-frame-exchange-manager.h
index bfb953610..cdd276c95 100644
--- a/src/wifi/model/eht/eht-frame-exchange-manager.h
+++ b/src/wifi/model/eht/eht-frame-exchange-manager.h
@@ -104,6 +104,9 @@ class EhtFrameExchangeManager : public HeFrameExchangeManager
     void ForwardPsduMapDown(WifiConstPsduMap psduMap, WifiTxVector& txVector) override;
     void SendMuRts(const WifiTxParameters& txParams) override;
     void CtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts, const WifiTxVector& txVector) override;
+    void SendCtsAfterMuRts(const WifiMacHeader& muRtsHdr,
+                           const CtrlTriggerHeader& trigger,
+                           double muRtsSnr) override;
     void TransmissionSucceeded() override;
     void TransmissionFailed() override;
     void NotifyChannelReleased(Ptr<Txop> txop) override;
diff --git a/src/wifi/model/eht/emlsr-manager.cc b/src/wifi/model/eht/emlsr-manager.cc
index 9ec3ed5f6..4b0ee2dc9 100644
--- a/src/wifi/model/eht/emlsr-manager.cc
+++ b/src/wifi/model/eht/emlsr-manager.cc
@@ -518,6 +518,12 @@ EmlsrManager::SwitchMainPhy(uint8_t linkId,
     NS_ASSERT_MSG(mainPhy != m_staMac->GetWifiPhy(linkId),
                   "Main PHY is already operating on link " << +linkId);
 
+    if (mainPhy->IsStateSwitching())
+    {
+        NS_LOG_DEBUG("Main PHY is already switching, ignore new switching request");
+        return;
+    }
+
     // find the link on which the main PHY is operating
     auto currMainPhyLinkId = m_staMac->GetLinkForPhy(mainPhy);
     NS_ASSERT_MSG(currMainPhyLinkId, "Current link ID for main PHY not found");
diff --git a/src/wifi/model/he/he-frame-exchange-manager.h b/src/wifi/model/he/he-frame-exchange-manager.h
index 60e857ea6..a11e63c92 100644
--- a/src/wifi/model/he/he-frame-exchange-manager.h
+++ b/src/wifi/model/he/he-frame-exchange-manager.h
@@ -219,9 +219,9 @@ class HeFrameExchangeManager : public VhtFrameExchangeManager
      * \param trigger the MU-RTS Trigger Frame header
      * \param muRtsSnr the SNR of the MU-RTS in linear scale
      */
-    void SendCtsAfterMuRts(const WifiMacHeader& muRtsHdr,
-                           const CtrlTriggerHeader& trigger,
-                           double muRtsSnr);
+    virtual void SendCtsAfterMuRts(const WifiMacHeader& muRtsHdr,
+                                   const CtrlTriggerHeader& trigger,
+                                   double muRtsSnr);
 
     /**
      * \return the mode used to transmit a CTS after an MU-RTS.