pcap: preserve malformed 802.11 captures

Fall back to a single whole-PSDU Radiotap record when A-MPDU parsing fails or produces no MPDU ranges. This prevents damaged, unusual, and delimiter-only PSDUs from disappearing from capture output and keeps recorder counters aligned with written observations.

Preserve established FCS presence when computed-FCS validation cannot serialize the preceding payload, without guessing FCS provenance from untyped byte chunks or fabricating a BADFCS result.

Extend the focused recorder tests to verify complete PSDU byte retention for malformed and empty aggregates, retain normal aggregate splitting, and cover the FCS serialization-failure path.

Author: mgonzalezlopezudc

src/inet/linklayer/ieee80211/pcap/Ieee80211RadiotapPcapCaptureAdapter.cc

@@ -217,11 +217,11 @@ FcsMetadata getIeee80211FcsMetadata(const Packet *packet, b frontOffset, b backO
     auto endOffset = packet->getDataLength() - backOffset;
     if (endOffset - frontOffset < B(4))
         return {};
+    FcsMetadata metadata;
     try {
         auto trailer = dynamicPtrCast<const ieee80211::Ieee80211MacTrailer>(packet->peekDataAt(endOffset - B(4), B(4)));
         if (trailer == nullptr)
-            return {};
-        FcsMetadata metadata;
+            return metadata;
         metadata.isPresent = true;
         switch (trailer->getFcsMode()) {
             case FCS_DECLARED_INCORRECT:
@@ -239,7 +239,7 @@ FcsMetadata getIeee80211FcsMetadata(const Packet *packet, b frontOffset, b backO
         return metadata;
     }
     catch (cRuntimeError&) {
-        return {};
+        return metadata;
     }
 }
 
@@ -461,9 +461,7 @@ std::vector<PcapCaptureRecord> Ieee80211RadiotapPcapCaptureAdapter::createRecord
 
     std::vector<MpduRange> mpduRanges;
     auto ampduParseResult = getIeee80211AmpduMpduRanges(packet, frontOffset, backOffset, mpduRanges);
-    if (ampduParseResult == AmpduParseResult::INVALID)
-        return {};
-    if (ampduParseResult == AmpduParseResult::VALID) {
+    if (ampduParseResult == AmpduParseResult::VALID && !mpduRanges.empty()) {
         std::vector<PcapCaptureRecord> records;
         records.reserve(mpduRanges.size());
         auto ampduReference = makeAmpduReference(packet);

tests/unit/PcapRecorderIeee80211Ampdu_1.test

@@ -149,6 +149,14 @@ static uint32_t readBigEndianUint32(const std::vector<uint8_t>& bytes, size_t of
     return value;
 }
 
+static void requireWholePacketRecord(const std::vector<uint8_t>& record, const Packet& packet)
+{
+    auto radiotapLength = readUint16(record, 2);
+    auto packetBytes = packet.peekData<BytesChunk>()->getBytes();
+    REQUIRE(record.size() == radiotapLength + packetBytes.size());
+    REQUIRE(std::equal(packetBytes.begin(), packetBytes.end(), record.begin() + radiotapLength));
+}
+
 %activity:
 
 auto recorder = check_and_cast<TestablePcapRecorder *>(getModuleByPath("recorder"));
@@ -207,7 +215,8 @@ Packet onlyEofPadding("onlyEofPadding");
 appendZeroLengthDelimiter(onlyEofPadding);
 appendZeroLengthDelimiter(onlyEofPadding);
 recorder->writeIeee80211(&onlyEofPadding, DIRECTION_INBOUND);
-REQUIRE(writer->records.empty());
+REQUIRE(writer->records.size() == 1);
+requireWholePacketRecord(writer->records.front(), onlyEofPadding);
 
 writer->records.clear();
 Packet malformed("malformed");
@@ -216,7 +225,8 @@ auto malformedDelimiter = makeShared<Ieee80211MpduSubframeHeader>();
 malformedDelimiter->setLength(100);
 malformed.insertAtBack(malformedDelimiter);
 recorder->writeIeee80211(&malformed, DIRECTION_INBOUND);
-REQUIRE(writer->records.empty());
+REQUIRE(writer->records.size() == 1);
+requireWholePacketRecord(writer->records.front(), malformed);
 
 writer->records.clear();
 Packet trailingPadding("trailingPadding");

tests/unit/PcapRecorderRadiotapHtVht_1.test

@@ -3,6 +3,7 @@ Test legacy Rate, HT MCS, VHT, and FCS Radiotap fields without fabricating unsup
 
 %includes:
 #include "inet/common/packet/chunk/BytesChunk.h"
+#include "inet/common/packet/chunk/FieldsChunk.h"
 #include "inet/common/ProtocolTag_m.h"
 #include "inet/common/checksum/Checksum.h"
 #include "inet/linklayer/ieee80211/mac/Ieee80211Frame_m.h"
@@ -21,6 +22,16 @@ using namespace inet::physicallayer;
 
 #define REQUIRE(...) do { if (!(__VA_ARGS__)) throw cRuntimeError("REQUIRE failed at line %d: %s", __LINE__, #__VA_ARGS__); } while (false)
 
+class UnserializableFieldsChunk : public FieldsChunk
+{
+  public:
+    UnserializableFieldsChunk() { setChunkLength(B(4)); }
+    UnserializableFieldsChunk(const UnserializableFieldsChunk& other) = default;
+
+    virtual UnserializableFieldsChunk *dup() const override { return new UnserializableFieldsChunk(*this); }
+    virtual const Ptr<Chunk> dupShared() const override { return makeShared<UnserializableFieldsChunk>(*this); }
+};
+
 static uint16_t readUint16(const std::vector<uint8_t>& bytes, size_t offset)
 {
     return bytes.at(offset) | bytes.at(offset + 1) << 8;
@@ -166,6 +177,14 @@ declaredIncorrect.insertAtBack(incorrectTrailer);
 auto declaredIncorrectHeader = createRadiotapHeader(adapter, declaredIncorrect);
 REQUIRE(declaredIncorrectHeader.at(8) == 0x50);
 
+Packet unserializablePayload("unserializablePayload");
+unserializablePayload.insertAtBack(makeShared<UnserializableFieldsChunk>());
+auto unserializablePayloadTrailer = makeShared<Ieee80211MacTrailer>();
+unserializablePayloadTrailer->setFcsMode(FCS_COMPUTED);
+unserializablePayload.insertAtBack(unserializablePayloadTrailer);
+auto unserializablePayloadHeader = createRadiotapHeader(adapter, unserializablePayload);
+REQUIRE(unserializablePayloadHeader.at(8) == 0x10); // typed FCS remains present when payload comparison fails
+
 EV << "Legacy, HT, VHT, and FCS Radiotap fields tested successfully.\n";
 
 %contains: stdout