This commit does some plumbing work to allow defining alternative
resolvers with different names that can be used to query different
upstream DNS servers.
This is most useful when implement DNSBLs where you might have a custom
DNS server configured with one or more RBL zones that is reserved purely
for RBL lookups.
The plumbing introduces a more regular syntax for defining one of the
various implementations of the Resolver trait, as well as a new
Aggregate resolver impl that can query across multiple Resolvers until a
query is satisfied.
This allows some interesting and powerful configurations, such as
loading a static zone file into memory to query it directly, and/or
blending that together with querying either the system or some other
upstream DNS server as a fallback.
The various lookup functions (except for MX!) have been updated to
accept an optional alternate resolver name, so that they work together
with the above.
A new rbl_lookup function is also provided as a convenience for querying
the most common form of RBLS.
ptr_host and reverse_ip are two string utility functions that are likely
not going to be widely used, but are very convenient to have when you
do have a usecase that requires it!
closes: https://github.com/KumoCorp/kumomta/issues/269
We've been hoping that mkdocs-material will ship the much anticipated
search enhancements for some time, but it's time to recognize that
we need to do something to improve the search results with how
things work right now.
This is a big commit that changes the titles of the various pages
from the code-annotated synopsis to just the name of the function.
This makes it much easier now to match things like `kumo.reject`
directly, but `reject` remains awkward to find.
I think this is the best that we can do at this time.
A few functions have been annotated with the `status: deprecated` to
show as deprecated in the toc/nav (shows with a little trash can next
to the name).
This commit does two things:
* Migrate the limit of 128 concurrent lookups from the shaping code
and into the general mx lookup code
* Adjust the mx lookup implementation to run inside the cache
getter, which applies thundering herd protection to the lookup.
These together will constrain the amount of queries being sent
to the upstream dns resolver and reduce the chances of it being
overwhelmed, especially if we are doing duplicate queries from
multiple concurrent contexts simultaneously.
This is why slow DNS often expanded to 3-4x as long as the expected
timeout value; we make a handful of calls in succession, assuming
that the cache was effective in an earlier stage.
We now cache errors for 5 minutes by default, and it can be configured
as desired.
refs: https://github.com/KumoCorp/kumomta/issues/325
This function returns MX information, including the computed site_name.
Update the queue example to show how to use it to populate the SITE_OF
map used in that example.
This commit switches to using the `Name` type under the covers to ensure
that we use canonical names for our cache keys.
Wez Furlong
kayozaki
ncai