Domain patterns in --address, --server and --local have, for many years,
matched complete labels only, so
--server=/google.com/1.2.3.4
will apply to google.com and www.google.com but NOT supergoogle.com
This commit introduces an optional '*' at the LHS of the domain string which
changes this behaviour so as to include substring matches _within_ labels. So,
--server=/*google.com/1.2.3.4
applies to google.com, www.google.com AND supergoogle.com.
For reasons unknown, I (srk) assumed that the orginal
substring domain matching algorithm was still in use,
where example.com would match eg. sexample.com
In fact the far more sensible label-based match, where
example.com (or .example.com) matches example.com and
www.example.com, but not sexample.com, has been in use
since release 2.22. This commit implements the 2.22 to 2.85
behaviour in the new domain-search code.
Thanks to Kevin Darbyshire-Bryant for spotting my mistake.
The optimisation based on the assumption that
"try now points to the last domain that sorts before the query"
fails in the specific edge case that the query sorts before
_any_ of the server domains. Handle this case.
Thanks to Xingcong Li for finding a test case for this bug.
In the specific case of configuring an A record for a domain
address=/example.com/1.2.3.4
queries for *example.com for any other type will now return
NOERR, and not the previous erroneous NXDOMAIN. The same thing
applies for
address=/example.com/::1:2:3:4
address=/example.com/#
This used to have a global limit, but that has a problem when using
different servers for different upstream domains. Queries which are
routed by domain to an upstream server which is not responding will
build up and trigger the limit, which breaks DNS service for all other
domains which could be handled by other servers. The change is to make
the limit per server-group, where a server group is the set of servers
configured for a particular domain. In the common case, where only
default servers are declared, there is no effective change.
This should be largely transparent, but it drastically
improves performance and reduces memory foot-print when
configuring large numbers domains of the form
local=/adserver.com/
or
local=/adserver.com/#
Lookup times now grow as log-to-base-2 of the number of domains,
rather than greater than linearly, as before.
The change makes multiple addresses associated with a domain work
address=/example.com/1.2.3.4
address=/example.com/5.6.7.8
It also handles multiple upstream servers for a domain better; using
the same try/retry alogrithms as non domain-specific servers. This
also applies to DNSSEC-generated queries.
Finally, some of the oldest and gnarliest code in dnsmasq has had
a significant clean-up. It's far from perfect, but it _is_ better.
