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tcp: (merges !367) Stop to merge items whose m_lost values are different

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This commit is contained in:
Xiuchao Wu
2020-08-13 14:33:18 +01:00
committed by Tom Henderson
parent f0e34da5eb
commit ee70f4502b
2 changed files with 33 additions and 2 deletions
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4
src/internet/model/tcp-tx-buffer.cc
View File

@@ -312,8 +312,8 @@ TcpTxBuffer::GetTransmittedSegment (uint32_t numBytes, const SequenceNumber32 &s
next++;
if (next != m_sentList.end ())
{
// Next is not sacked... there is the possibility to merge
if (! (*next)->m_sacked)
// Next is not sacked and have the same value for m_lost ... there is the possibility to merge
if ((! (*next)->m_sacked) && ((*it)->m_lost == (*next)->m_lost))
{
s = std::min(s, (*it)->m_packet->GetSize () + (*next)->m_packet->GetSize ());
}

31
src/internet/test/tcp-tx-buffer-test.cc
View File

@@ -50,6 +50,9 @@ private:
void TestTransmittedBlock ();
/** \brief Test the generation of the "next" block */
void TestNextSeg ();
/** \brief Test the logic of merging items in GetTransmittedSegment()
* which is triggered by CopyFromSequence()*/
void TestMergeItemsWhenGetTransmittedSegment ();
/** \brief Callback to provide a value of receiver window */
uint32_t GetRWnd (void) const;
};
@@ -85,6 +88,16 @@ TcpTxBufferTestCase::DoRun ()
Simulator::Schedule (Seconds (0.0),
&TcpTxBufferTestCase::TestNextSeg, this);
/*
* Case for transmitted block:
* -> transmitted packets are marked differently for m_lost under some scenarios
* -> packets could be small than MSS when socket buffer is not a multiple of MSS.
* -> during retransmission, the sender tries to send a full segment but it
* should stop to merge items when they have different values for m_lost.
*/
Simulator::Schedule (Seconds (0.0),
&TcpTxBufferTestCase::TestMergeItemsWhenGetTransmittedSegment, this);
Simulator::Run ();
Simulator::Destroy ();
}
@@ -351,6 +364,24 @@ TcpTxBufferTestCase::TestNewBlock ()
"Size is different than expected");
}
void
TcpTxBufferTestCase::TestMergeItemsWhenGetTransmittedSegment ()
{
TcpTxBuffer txBuf;
SequenceNumber32 head (1);
txBuf.SetHeadSequence (head);
txBuf.SetSegmentSize (2000);
txBuf.Add(Create<Packet> (2000));
txBuf.CopyFromSequence (1000, SequenceNumber32(1));
txBuf.CopyFromSequence (1000, SequenceNumber32(1001));
txBuf.MarkHeadAsLost();
// GetTransmittedSegment() will be called and handle the case that two items
// have different m_lost value.
txBuf.CopyFromSequence (2000, SequenceNumber32(1));
}
void
TcpTxBufferTestCase::TestTransmittedBlock ()
{