From 0c55cce6195612ce6ad5f3aee99ed31501595e3d Mon Sep 17 00:00:00 2001
From: Levente Meszaros <levy@omnetpp.org>
Date: Wed, 11 Dec 2024 17:01:00 +0100
Subject: [PATCH] all: Fixed #932.

Changed the Gptp header lookup to use a packet dissector to avoid mishandling fragmented packets.
---
 .../packet/dissector/PacketDissector.cc       |  8 +++++++
 .../common/packet/dissector/PacketDissector.h | 17 +++++++++++++
 src/inet/linklayer/ieee8021as/Gptp.cc         | 24 +++++++------------
 3 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/src/inet/common/packet/dissector/PacketDissector.cc b/src/inet/common/packet/dissector/PacketDissector.cc
index c82bf93d306..eb388a4e67a 100644
--- a/src/inet/common/packet/dissector/PacketDissector.cc
+++ b/src/inet/common/packet/dissector/PacketDissector.cc
@@ -83,6 +83,14 @@ void PacketDissector::ChunkBuilder::visitChunk(const Ptr<const Chunk>& chunk, co
     }
 }
 
+// ChunkFinder
+
+void PacketDissector::ChunkFinder::visitChunk(const Ptr<const Chunk>& chunk, const Protocol *protocol)
+{
+    if (this->protocol == protocol)
+        this->chunk = chunk;
+}
+
 // PduTreeBuilder
 
 void PacketDissector::PduTreeBuilder::startProtocolDataUnit(const Protocol *protocol)
diff --git a/src/inet/common/packet/dissector/PacketDissector.h b/src/inet/common/packet/dissector/PacketDissector.h
index 9c59bb88e59..a819735c66a 100644
--- a/src/inet/common/packet/dissector/PacketDissector.h
+++ b/src/inet/common/packet/dissector/PacketDissector.h
@@ -112,6 +112,23 @@ class INET_API PacketDissector
         virtual void visitChunk(const Ptr<const Chunk>& chunk, const Protocol *protocol) override;
     };
 
+    class INET_API ChunkFinder : public PacketDissector::ICallback {
+      protected:
+        const Protocol *protocol;
+        Ptr<const Chunk> chunk;
+
+      public:
+        ChunkFinder(const Protocol *protocol) : protocol(protocol) { }
+
+        const Ptr<const Chunk> getChunk() { return chunk; }
+
+        virtual bool shouldDissectProtocolDataUnit(const Protocol *protocol) override { return true; }
+        virtual void startProtocolDataUnit(const Protocol *protocol) override {}
+        virtual void endProtocolDataUnit(const Protocol *protocol) override {}
+        virtual void markIncorrect() override {}
+        virtual void visitChunk(const Ptr<const Chunk>& chunk, const Protocol *protocol) override;
+    };
+
     class INET_API PduTreeBuilder : public PacketDissector::ICallback {
       protected:
         bool isEndProtocolDataUnitCalled = false;
diff --git a/src/inet/linklayer/ieee8021as/Gptp.cc b/src/inet/linklayer/ieee8021as/Gptp.cc
index f2e93f83df3..92a8cd1b3da 100644
--- a/src/inet/linklayer/ieee8021as/Gptp.cc
+++ b/src/inet/linklayer/ieee8021as/Gptp.cc
@@ -5,18 +5,18 @@
 //           University of Rostock, Germany
 //
 
-#include "Gptp.h"
-
-#include "GptpPacket_m.h"
+#include "inet/linklayer/ieee8021as/Gptp.h"
 
 #include "inet/clock/model/SettableClock.h"
-#include "inet/common/IProtocolRegistrationListener.h"
 #include "inet/common/clock/ClockUserModuleBase.h"
+#include "inet/common/IProtocolRegistrationListener.h"
+#include "inet/common/packet/dissector/PacketDissector.h"
 #include "inet/linklayer/common/InterfaceTag_m.h"
 #include "inet/linklayer/common/MacAddress.h"
 #include "inet/linklayer/common/MacAddressTag_m.h"
 #include "inet/linklayer/ethernet/common/Ethernet.h"
 #include "inet/linklayer/ethernet/common/EthernetMacHeader_m.h"
+#include "inet/linklayer/ieee8021as/GptpPacket_m.h"
 #include "inet/networklayer/common/NetworkInterface.h"
 #include "inet/physicallayer/wired/ethernet/EthernetPhyHeader_m.h"
 
@@ -493,17 +493,11 @@ void Gptp::processPdelayRespFollowUp(Packet *packet, const GptpPdelayRespFollowU
 
 const GptpBase *Gptp::extractGptpHeader(Packet *packet)
 {
-    auto protocol = packet->getTag<PacketProtocolTag>()->getProtocol();
-    if (*protocol != Protocol::ethernetPhy)
-        return nullptr;
-
-    const auto& ethPhyHeader = packet->peekAtFront<physicallayer::EthernetPhyHeader>();
-    const auto& ethMacHeader = packet->peekDataAt<EthernetMacHeader>(ethPhyHeader->getChunkLength());
-    if (ethMacHeader->getTypeOrLength() != ETHERTYPE_GPTP)
-        return nullptr;
-
-    b offset = ethPhyHeader->getChunkLength() + ethMacHeader->getChunkLength();
-    return packet->peekDataAt<GptpBase>(offset).get();
+    PacketDissector::ChunkFinder chunkFinder(&Protocol::gptp);
+    PacketDissector packetDissector(ProtocolDissectorRegistry::getInstance(), chunkFinder);
+    packetDissector.dissectPacket(packet);
+    const auto& chunk = staticPtrCast<const GptpBase>(chunkFinder.getChunk());
+    return chunk != nullptr ? chunk.get() : nullptr;
 }
 
 void Gptp::receiveSignal(cComponent *source, simsignal_t simSignal, cObject *obj, cObject *details)