[EMCAL-1048] Treat faulty memory size reported by RDH

In case the memory size in the RDH reported is larger
then the raw payload size forward the current positon
to payload size or offsetToNext - whatever is smaller,
before raising the error.

In case the trailer is incomplete the page cannot be trusted,
likely because it is overwritten in memory. The marker must
be forwarded and an exception is thrown.

Author: mfasDa

Detectors/EMCAL/reconstruction/include/EMCALReconstruction/RawReaderMemory.h

@@ -148,11 +148,10 @@ class RawReaderMemory
   /// Rewind stream to the first entry
   void init();
 
-  /// \brief Check whether the current page is accepted
-  /// \param page Raw page to check
-  /// \return True if the page is accepted, false otherwise
-  bool acceptPage(const char* page) const;
-
+  /// \brief Decode raw header words
+  /// \param headerwords Headerwords
+  /// \return Decoded RDH
+  /// \throw RawDecodingError with code HEADER_DECODING if the payload does not correspond to an expected header
   o2::header::RDHAny decodeRawHeader(const void* headerwords);
 
  private:

Detectors/EMCAL/reconstruction/src/RawReaderMemory.cxx

@@ -8,11 +8,13 @@
 // In applying this license CERN does not waive the privileges and immunities
 // granted to it by virtue of its status as an Intergovernmental Organization
 // or submit itself to any jurisdiction.
-
+#include <iostream>
 #include <sstream>
 #include <string>
 #include "EMCALReconstruction/RawReaderMemory.h"
 #include "DetectorsRaw/RDHUtils.h"
+#include "Headers/RAWDataHeader.h"
+#include "Headers/DAQID.h"
 
 using namespace o2::emcal;
 
@@ -35,6 +37,16 @@ o2::header::RDHAny RawReaderMemory::decodeRawHeader(const void* payloadwords)
   if (headerversion < RDHDecoder::getVersion<o2::header::RDHLowest>() || headerversion > RDHDecoder::getVersion<o2::header::RDHHighest>()) {
     throw RawDecodingError(RawDecodingError::ErrorType_t::HEADER_DECODING, mCurrentFEE);
   }
+  if (!RDHDecoder::checkRDH(payloadwords, false, true)) {
+    // Header size != to 64 and 0 in reserved words indicate that the header is a fake header
+    throw RawDecodingError(RawDecodingError::ErrorType_t::HEADER_DECODING, mCurrentFEE);
+  }
+  if (RDHDecoder::getVersion(payloadwords) >= 6) {
+    // If header version is >= 6 check that the source ID is EMCAL
+    if (RDHDecoder::getSourceID(payloadwords) != o2::header::DAQID::EMC) {
+      throw RawDecodingError(RawDecodingError::ErrorType_t::HEADER_DECODING, mCurrentFEE);
+    }
+  }
   return {*reinterpret_cast<const o2::header::RDHAny*>(payloadwords)};
 }
 
@@ -117,9 +129,31 @@ void RawReaderMemory::nextPage(bool doResetPayload)
   }
   if (mCurrentPosition + RDHDecoder::getMemorySize(mRawHeader) > mRawMemoryBuffer.size()) {
     // Payload incomplete
+    // Set to offset to next or buffer size, whatever is smaller
+    if (mCurrentPosition + RDHDecoder::getOffsetToNext(mRawHeader) < mRawMemoryBuffer.size()) {
+      mCurrentPosition += RDHDecoder::getOffsetToNext(mRawHeader);
+      if (mCurrentPosition + 64 < mRawMemoryBuffer.size()) {
+        // check if the page continues with a RDH
+        // if next page is not a header decodeRawHeader will throw a RawDecodingError
+        auto nextheader = decodeRawHeader(mRawMemoryBuffer.data() + mCurrentPosition);
+        if (RDHDecoder::getVersion(nextheader) != RDHDecoder::getVersion(mRawHeader)) {
+          // Next header has different header version - clear indication that it is a fake header
+          throw RawDecodingError(RawDecodingError::ErrorType_t::HEADER_DECODING, mCurrentFEE);
+        }
+      }
+    } else {
+      mCurrentPosition = mRawMemoryBuffer.size();
+    }
+    // RDHDecoder::printRDH(mRawHeader);
     throw RawDecodingError(RawDecodingError::ErrorType_t::PAYLOAD_DECODING, mCurrentFEE);
   } else if (mCurrentPosition + RDHDecoder::getHeaderSize(mRawHeader) > mRawMemoryBuffer.size()) {
     // Start position of the payload is outside the payload range
+    // Set to offset to next or buffer size, whatever is smaller
+    if (mCurrentPosition + RDHDecoder::getOffsetToNext(mRawHeader) < mRawMemoryBuffer.size()) {
+      mCurrentPosition += RDHDecoder::getOffsetToNext(mRawHeader);
+    } else {
+      mCurrentPosition = mRawMemoryBuffer.size();
+    }
     throw RawDecodingError(RawDecodingError::ErrorType_t::PAGE_START_INVALID, mCurrentFEE);
   } else {
     mRawBuffer.readFromMemoryBuffer(gsl::span<const char>(mRawMemoryBuffer.data() + mCurrentPosition + RDHDecoder::getHeaderSize(mRawHeader), RDHDecoder::getMemorySize(mRawHeader) - RDHDecoder::getHeaderSize(mRawHeader)));
@@ -154,6 +188,13 @@ void RawReaderMemory::nextPage(bool doResetPayload)
             mMinorErrors.emplace_back(RawDecodingError::ErrorType_t::TRAILER_INCOMPLETE, mCurrentFEE);
           }
         } catch (RCUTrailer::Error& e) {
+          // We must forward the position in such cases in order to not end up in an infinity loop
+          if (mCurrentPosition + RDHDecoder::getOffsetToNext(mRawHeader) < mRawMemoryBuffer.size()) {
+            mCurrentPosition += RDHDecoder::getOffsetToNext(mRawHeader);
+          } else {
+            mCurrentPosition = mRawMemoryBuffer.size();
+          }
+          // Page is not consistent - must be skipped
           throw RawDecodingError(RawDecodingError::ErrorType_t::TRAILER_DECODING, mCurrentFEE);
         }
       } else {