This commit simplifies the cachedb rrset statistics in two ways:
- Introduce new rdtypecounter arithmetics, allowing bitwise
operations.
- Remove the special DLV statistic counter.
New rdtypecounter arithmetics
-----------------------------
"The rdtypecounter arithmetics is a brain twister". Replace the
enum counters with some defines. A rdtypecounter is now 8 bits for
RRtypes and 3 bits for flags:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | | | | S |NX| RRType |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
If the 8 bits for RRtype are all zero, this is an Other RRtype.
Bit 7 is the NXRRSET (NX) flag and indicates whether this is a
positive (0) or a negative (1) RRset.
Then bit 5 and 6 mostly tell you if this counter is for an active,
stale, or ancient RRtype:
S = 0x00 means Active
S = 0x01 means Stale
S = 0x10 means Ancient
Since a counter cannot be stale and ancient at the same time, we
treat S = 0x11 as a special case to deal with NXDOMAIN counters.
S = 0x11 indicates an NXDOMAIN counter and in this case the RRtype
field signals the expiry of this cached item:
RRType = 0 means Active
RRType = 1 means Stale
RRType = 2 means Ancient
This also removes counting the DLV RRtype separately. Since we have
deprecated the lookaside validation it makes no sense to keep this
special statistic counter.
Having the decrement/increment logic in stats makes the code hard
to follow. Remove it here and adjust the unit test. The caller
will be responsible for maintaining the correct increments and
decrements for statistics counters (in the following commit).
