// Package fingerprint identifies DNS server software by sending a
// version.bind CHAOS TXT query to each server IP address.
//
// The Fingerprinter type caches results so repeated queries for the same IP
// are answered from memory without a network round-trip.
// FingerprintAll queries a list of IPs concurrently and returns a map of
// IP string → version string.  Servers that do not support version.bind, or
// that time out, map to the empty string.
package fingerprint