[Bug 1964] New: QoS/DSCP names false translated to ToS hex value

bugzilla-daemon at bugzilla.mindrot.org bugzilla-daemon at bugzilla.mindrot.org
Sun Dec 18 22:09:21 EST 2011


             Bug #: 1964
           Summary: QoS/DSCP names false translated to ToS hex value
    Classification: Unclassified
           Product: Portable OpenSSH
           Version: 5.9p1
          Platform: amd64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ssh
        AssignedTo: unassigned-bugs at mindrot.org
        ReportedBy: bugzilla.mindrot.org at pobox.madduck.net

The ToS field (8 bit) is partitioned as follows:

                            DSCP                                    ECN

The OpenSSH client currently translates DSCP classes directly into
their hex code and fills the entire ToS field with that. Instead, it
should bitshift the DSCP number by 2 bits to the left and OR it with
the ECN number.

E.g. class cs1 ("throughput", 0x08) becomes "000010|00". When
written directly into the ToS field, that yields a DSCP of 0x02,
which is undefined.

The 0x08 should only be written into the highest 6 bits, and the ToS
field should be 0x20 afterwards.

The same applies to class cs2 ("lowdelay", 0x10), which is written
as 00010000 (DSCP class 0x04, which is also undefined), when instead
it should be 0x40.

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