From f392502d9dcd6503af31789c7abaae47a0a84d28 Mon Sep 17 00:00:00 2001
From: Tommaso Pecorella <tommaso.pecorella@unifi.it>
Date: Wed, 4 Oct 2023 09:44:15 +0200
Subject: [PATCH] csma: use const on transmitted packets

---
 src/csma/model/csma-channel.cc    |  4 ++--
 src/csma/model/csma-channel.h     |  2 +-
 src/csma/model/csma-net-device.cc | 33 ++++++++++++++++---------------
 src/csma/model/csma-net-device.h  |  2 +-
 4 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/src/csma/model/csma-channel.cc b/src/csma/model/csma-channel.cc
index 2a0defc8c..af1e44a5b 100644
--- a/src/csma/model/csma-channel.cc
+++ b/src/csma/model/csma-channel.cc
@@ -191,7 +191,7 @@ CsmaChannel::TransmitStart(Ptr<const Packet> p, uint32_t srcId)
     }
 
     NS_LOG_LOGIC("switch to TRANSMITTING");
-    m_currentPkt = p->Copy();
+    m_currentPkt = p;
     m_currentSrc = srcId;
     m_state = TRANSMITTING;
     return true;
@@ -234,7 +234,7 @@ CsmaChannel::TransmitEnd()
                                            m_delay,
                                            &CsmaNetDevice::Receive,
                                            it->devicePtr,
-                                           m_currentPkt->Copy(),
+                                           m_currentPkt,
                                            m_deviceList[m_currentSrc].devicePtr);
         }
     }
diff --git a/src/csma/model/csma-channel.h b/src/csma/model/csma-channel.h
index da4e948da..92263545e 100644
--- a/src/csma/model/csma-channel.h
+++ b/src/csma/model/csma-channel.h
@@ -325,7 +325,7 @@ class CsmaChannel : public Channel
      * packet to have been transmitted on the channel if the channel is
      * free.)
      */
-    Ptr<Packet> m_currentPkt;
+    Ptr<const Packet> m_currentPkt;
 
     /**
      * Device Id of the source that is currently transmitting on the
diff --git a/src/csma/model/csma-net-device.cc b/src/csma/model/csma-net-device.cc
index bb0b93894..fded5253f 100644
--- a/src/csma/model/csma-net-device.cc
+++ b/src/csma/model/csma-net-device.cc
@@ -695,7 +695,7 @@ CsmaNetDevice::SetReceiveErrorModel(Ptr<ErrorModel> em)
 }
 
 void
-CsmaNetDevice::Receive(Ptr<Packet> packet, Ptr<CsmaNetDevice> senderDevice)
+CsmaNetDevice::Receive(Ptr<const Packet> packet, Ptr<CsmaNetDevice> senderDevice)
 {
     NS_LOG_FUNCTION(packet << senderDevice);
     NS_LOG_LOGIC("UID is " << packet->GetUid());
@@ -724,7 +724,9 @@ CsmaNetDevice::Receive(Ptr<Packet> packet, Ptr<CsmaNetDevice> senderDevice)
         return;
     }
 
-    if (m_receiveErrorModel && m_receiveErrorModel->IsCorrupt(packet))
+    Ptr<Packet> pktCopy = packet->Copy();
+
+    if (m_receiveErrorModel && m_receiveErrorModel->IsCorrupt(pktCopy))
     {
         NS_LOG_LOGIC("Dropping pkt due to error model ");
         m_phyRxDropTrace(packet);
@@ -735,16 +737,15 @@ CsmaNetDevice::Receive(Ptr<Packet> packet, Ptr<CsmaNetDevice> senderDevice)
     // Trace sinks will expect complete packets, not packets without some of the
     // headers.
     //
-    Ptr<Packet> originalPacket = packet->Copy();
 
     EthernetTrailer trailer;
-    packet->RemoveTrailer(trailer);
+    pktCopy->RemoveTrailer(trailer);
     if (Node::ChecksumEnabled())
     {
         trailer.EnableFcs(true);
     }
 
-    bool crcGood = trailer.CheckFcs(packet);
+    bool crcGood = trailer.CheckFcs(pktCopy);
     if (!crcGood)
     {
         NS_LOG_INFO("CRC error on Packet " << packet);
@@ -753,7 +754,7 @@ CsmaNetDevice::Receive(Ptr<Packet> packet, Ptr<CsmaNetDevice> senderDevice)
     }
 
     EthernetHeader header(false);
-    packet->RemoveHeader(header);
+    pktCopy->RemoveHeader(header);
 
     NS_LOG_LOGIC("Pkt source is " << header.GetSource());
     NS_LOG_LOGIC("Pkt destination is " << header.GetDestination());
@@ -767,16 +768,16 @@ CsmaNetDevice::Receive(Ptr<Packet> packet, Ptr<CsmaNetDevice> senderDevice)
     //
     if (header.GetLengthType() <= 1500)
     {
-        NS_ASSERT(packet->GetSize() >= header.GetLengthType());
-        uint32_t padlen = packet->GetSize() - header.GetLengthType();
+        NS_ASSERT(pktCopy->GetSize() >= header.GetLengthType());
+        uint32_t padlen = pktCopy->GetSize() - header.GetLengthType();
         NS_ASSERT(padlen <= 46);
         if (padlen > 0)
         {
-            packet->RemoveAtEnd(padlen);
+            pktCopy->RemoveAtEnd(padlen);
         }
 
         LlcSnapHeader llc;
-        packet->RemoveHeader(llc);
+        pktCopy->RemoveHeader(llc);
         protocol = llc.GetType();
     }
     else
@@ -811,12 +812,12 @@ CsmaNetDevice::Receive(Ptr<Packet> packet, Ptr<CsmaNetDevice> senderDevice)
     // hook and pass a copy up to the promiscuous callback.  Pass a copy to
     // make sure that nobody messes with our packet.
     //
-    m_promiscSnifferTrace(originalPacket);
+    m_promiscSnifferTrace(packet);
     if (!m_promiscRxCallback.IsNull())
     {
-        m_macPromiscRxTrace(originalPacket);
+        m_macPromiscRxTrace(packet);
         m_promiscRxCallback(this,
-                            packet,
+                            pktCopy,
                             protocol,
                             header.GetSource(),
                             header.GetDestination(),
@@ -830,9 +831,9 @@ CsmaNetDevice::Receive(Ptr<Packet> packet, Ptr<CsmaNetDevice> senderDevice)
     //
     if (packetType != PACKET_OTHERHOST)
     {
-        m_snifferTrace(originalPacket);
-        m_macRxTrace(originalPacket);
-        m_rxCallback(this, packet, protocol, header.GetSource());
+        m_snifferTrace(packet);
+        m_macRxTrace(packet);
+        m_rxCallback(this, pktCopy, protocol, header.GetSource());
     }
 }
 
diff --git a/src/csma/model/csma-net-device.h b/src/csma/model/csma-net-device.h
index ff72aad2a..af092bfa6 100644
--- a/src/csma/model/csma-net-device.h
+++ b/src/csma/model/csma-net-device.h
@@ -172,7 +172,7 @@ class CsmaNetDevice : public NetDevice
      * \param p a reference to the received packet
      * \param sender the CsmaNetDevice that transmitted the packet in the first place
      */
-    void Receive(Ptr<Packet> p, Ptr<CsmaNetDevice> sender);
+    void Receive(Ptr<const Packet> p, Ptr<CsmaNetDevice> sender);
 
     /**
      * Is the send side of the network device enabled?