tcp: Get the number of bytes SACKed out of the option processing

src/internet/model/tcp-socket-base.cc

@@ -1506,7 +1506,7 @@ TcpSocketBase::IsTcpOptionEnabled (uint8_t kind) const
 }
 
 void
-TcpSocketBase::ReadOptions (const TcpHeader &tcpHeader, bool &scoreboardUpdated)
+TcpSocketBase::ReadOptions (const TcpHeader &tcpHeader, uint32_t *bytesSacked)
 {
   NS_LOG_FUNCTION (this << tcpHeader);
   TcpHeader::TcpOptionList::const_iterator it;
@@ -1520,7 +1520,7 @@ TcpSocketBase::ReadOptions (const TcpHeader &tcpHeader, bool &scoreboardUpdated)
       switch (option->GetKind ())
         {
         case TcpOption::SACK:
-          scoreboardUpdated = ProcessOptionSack (option);
+          *bytesSacked = ProcessOptionSack (option);
           break;
         default:
           continue;
@@ -1680,8 +1680,8 @@ TcpSocketBase::ReceivedAck (Ptr<Packet> packet, const TcpHeader& tcpHeader)
   // RFC 6675, Section 5, 1st paragraph:
   // Upon the receipt of any ACK containing SACK information, the
   // scoreboard MUST be updated via the Update () routine (done in ReadOptions)
-  bool scoreboardUpdated = false;
-  ReadOptions (tcpHeader, scoreboardUpdated);
+  uint32_t bytesSacked = 0;
+  ReadOptions (tcpHeader, &bytesSacked);
 
   SequenceNumber32 ackNumber = tcpHeader.GetAckNumber ();
   SequenceNumber32 oldHeadSequence = m_txBuffer->HeadSequence ();
@@ -1704,7 +1704,7 @@ TcpSocketBase::ReceivedAck (Ptr<Packet> packet, const TcpHeader& tcpHeader)
 
   // RFC 6675 Section 5: 2nd, 3rd paragraph and point (A), (B) implementation
   // are inside the function ProcessAck
-  ProcessAck (ackNumber, scoreboardUpdated, oldHeadSequence);
+  ProcessAck (ackNumber, (bytesSacked > 0), oldHeadSequence);
 
   // If there is any data piggybacked, store it into m_rxBuffer
   if (packet->GetSize () > 0)
@@ -3946,14 +3946,13 @@ TcpSocketBase::AddOptionWScale (TcpHeader &header)
                static_cast<int> (m_rcvWindShift));
 }
 
-bool
+uint32_t
 TcpSocketBase::ProcessOptionSack (const Ptr<const TcpOption> option)
 {
   NS_LOG_FUNCTION (this << option);
 
   Ptr<const TcpOptionSack> s = DynamicCast<const TcpOptionSack> (option);
-  TcpOptionSack::SackList list = s->GetSackList ();
-  return m_txBuffer->Update (list);
+  return m_txBuffer->Update (s->GetSackList ());
 }
 
 void

src/internet/model/tcp-socket-base.h

@@ -1051,10 +1051,9 @@ protected:
    * Timestamp and Window scale are managed in other pieces of code.
    *
    * \param tcpHeader Header of the segment
-   * \param scoreboardUpdated indicates if the scoreboard was updated due to a
-   * SACK option
+   * \param [out] bytesSacked Number of bytes SACKed, or 0
    */
-  void ReadOptions (const TcpHeader &tcpHeader, bool &scoreboardUpdated);
+  void ReadOptions (const TcpHeader &tcpHeader, uint32_t *bytesSacked);
 
   /**
    * \brief Return true if the specified option is enabled
@@ -1106,9 +1105,9 @@ protected:
    * \brief Read the SACK option
    *
    * \param option SACK option from the header
-   * \returns true in case of an update to the SACKed blocks
+   * \returns the number of bytes sacked by this option
    */
-  bool ProcessOptionSack (const Ptr<const TcpOption> option);
+  uint32_t ProcessOptionSack(const Ptr<const TcpOption> option);
 
   /**
    * \brief Add the SACK PERMITTED option to the header

src/internet/model/tcp-tx-buffer.cc

@@ -746,23 +746,23 @@ TcpTxBuffer::DiscardUpTo (const SequenceNumber32& seq)
   ConsistencyCheck ();
 }
 
-bool
+uint32_t
 TcpTxBuffer::Update (const TcpOptionSack::SackList &list)
 {
   NS_LOG_FUNCTION (this);
   NS_LOG_INFO ("Updating scoreboard, got " << list.size () << " blocks to analyze");
 
-  bool modified = false;
+  uint32_t bytesSacked = 0;
 
   for (auto option_it = list.begin (); option_it != list.end (); ++option_it)
     {
       PacketList::iterator item_it = m_sentList.begin ();
       SequenceNumber32 beginOfCurrentPacket = m_firstByteSeq;
 
-      if (m_firstByteSeq + m_sentSize < (*option_it).first && !modified)
+      if (m_firstByteSeq + m_sentSize < (*option_it).first)
         {
           NS_LOG_INFO ("Not updating scoreboard, the option block is outside the sent list");
-          return false;
+          return bytesSacked;
         }
 
       while (item_it != m_sentList.end ())
@@ -794,6 +794,7 @@ TcpTxBuffer::Update (const TcpOptionSack::SackList &list)
 
                   (*item_it)->m_sacked = true;
                   m_sackedOut += (*item_it)->m_packet->GetSize ();
+                  bytesSacked += (*item_it)->m_packet->GetSize ();
 
                   if (m_highestSack.first == m_sentList.end()
                       || m_highestSack.second <= beginOfCurrentPacket + pktSize)
@@ -806,7 +807,6 @@ TcpTxBuffer::Update (const TcpOptionSack::SackList &list)
                                ", found in the sackboard, sacking, current highSack: " <<
                                m_highestSack.second);
                 }
-              modified = true;
             }
           else if (beginOfCurrentPacket + pktSize > (*option_it).second)
             {
@@ -822,9 +822,9 @@ TcpTxBuffer::Update (const TcpOptionSack::SackList &list)
         }
     }
 
-  if (modified)
+  if (bytesSacked > 0)
     {
-      NS_ASSERT_MSG (modified && m_highestSack.first != m_sentList.end(), "Buffer status: " << *this);
+      NS_ASSERT_MSG (m_highestSack.first != m_sentList.end(), "Buffer status: " << *this);
       UpdateLostCount ();
     }
 
@@ -833,7 +833,7 @@ TcpTxBuffer::Update (const TcpOptionSack::SackList &list)
   //NS_ASSERT (list.size () == 0 || modified);   // Assert for duplicated SACK or
                                                  // impossiblity to map the option into the sent blocks
   ConsistencyCheck ();
-  return modified;
+  return bytesSacked;
 }
 
 void

src/internet/model/tcp-tx-buffer.h

@@ -267,9 +267,9 @@ public:
   /**
    * \brief Update the scoreboard
    * \param list list of SACKed blocks
-   * \returns true in case of an update
+   * \returns the number of bytes newly sacked by the list of blocks
    */
-  bool Update (const TcpOptionSack::SackList &list);
+  uint32_t Update (const TcpOptionSack::SackList &list);
 
   /**
    * \brief Check if a segment is lost