Provides an optional resolver mechanism for Firefox that allows running
together with or instead of the native resolver.
TRR offers resolving of host names using a dedicated DNS-over-HTTPS server
(HTTPS is required, HTTP/2 is preferable).
DNS-over-HTTPS (DOH) allows DNS resolves with enhanced privacy, secure
transfers and improved performance.
To keep the failure rate at a minimum, the TRR system manages a dynamic
persistent blacklist for host names that can't be resolved with DOH but works
with the native resolver. Blacklisted entries will not be retried over DOH for
a couple of days. "localhost" and names in the ".local" TLD will not be
resolved via DOH.
TRR is preffed OFF by default and you need to set a URI for an available DOH
server to be able to use it. Since the URI for DOH is set with a name itself,
it may have to use the native resolver for bootstrapping. (Optionally, the
user can set the IP address of the DOH server in a pref to avoid the required
initial native resolve.)
When TRR starts up, it will first verify that it works by checking a
"confirmation" domain name. This confirmation domain is a pref by default set
to "example.com". TRR will also by default await the captive-portal detection
to raise its green flag before getting activated.
All prefs for TRR are under the "network.trr" hierarchy.
The DNS-over-HTTPS spec: https://tools.ietf.org/html/draft-ietf-doh-dns-over-https-03
MozReview-Commit-ID: GuuU6vjTjlm
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extra : rebase_source : 53fcca757334090ac05fec540ef29d109d5ceed3
