A TCP retry to the server that just answered can only return the same
rcode, and when that server accepted the connection and never answered,
the query ran the full 10s dnsQueryTimeout and the client got nothing.
An upstream rcode now ends the UDP/TCP race when it arrives, and the
client gets it once every resolver has had udpRaceTimeout to answer
instead of waiting for all of them to report. tcpQueryTimeout is also
set on the conn, since a context cannot interrupt a blocked read, and a
new dns_query_fwd_udp_read_ctx_done counter separates query teardown
from upstream read errors.
Fixes#20826
Signed-off-by: Brendan Creane <bcreane@gmail.com>
Brendan Creane
b62885dd02