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internet: read correct bits when deserializing IPv6 flow label

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On line 153, `m_flowLabel` is OR-ed into the LSBs of `vTcFl`, which is then written with `WriteHtonU32` into the buffer. On line 169, `vTcFl` is read out using `ReadNtohU32`, so the byte order should be the same as it was on line 153. However, currently `m_flowLabel` is being assigned the value of `vTcFl` masked by `0xfff00000`.

This commit changes line 177 to read the correct set of 20 bits to recover the original flow label.

One question: Right now, `SetFlowLabel` (and the other setters) don't check that the value is in range, and Serialize doesn't mask them. Should this be fixed? Right now, a large flow label would clobber the traffic class and version fields.
This commit is contained in:
Greg Steinbrecher
2021-11-04 00:55:07 +00:00
parent 80134a570d
commit 161c4fa2ce
1 changed files with 1 additions and 1 deletions
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2
src/internet/model/ipv6-header.cc
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@@ -194,7 +194,7 @@ uint32_t Ipv6Header::Deserialize (Buffer::Iterator start)
}
m_trafficClass = (uint8_t)((vTcFl >> 20) & 0x000000ff);
m_flowLabel = vTcFl & 0xfff00000;
m_flowLabel = vTcFl & 0xfffff;
m_payloadLength = i.ReadNtohU16 ();
m_nextHeader = i.ReadU8 ();
m_hopLimit = i.ReadU8 ();