Add -m to force cache-miss measurement in dnseval (Closes #41)
Using `-m` causes dnseval to add a random hostname prefix to the given domain name (format is "_dnseval_RANDOM_."). This will cause NXDOMAIN and the query fails, but we do measure the response time anyway.
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63
dnseval.py
63
dnseval.py
@ -33,6 +33,8 @@ import signal
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import socket
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import sys
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import time
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import random
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import string
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from statistics import stdev
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import dns.rdatatype
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@ -67,10 +69,11 @@ def usage():
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print("""%s version %s
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usage: %s [-h] [-f server-list] [-c count] [-t type] [-w wait] hostname
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-h --help show this help
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-f --file dns server list to use (default: system resolvers)
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-c --count number of requests to send (default: 10)
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-w --wait maximum wait time for a reply (default: 2)
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-h --help Show this help
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-f --file DNS server list to use (default: system resolvers)
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-c --count Number of requests to send (default: 10)
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-m --cache-miss Force cache miss measurement by prepending a random hostname
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-w --wait Maximum wait time for a reply (default: 2)
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-t --type DNS request record type (default: A)
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-T --tcp Use TCP instead of UDP
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-e --edns Disable EDNS0 (Default: Enabled)
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@ -137,7 +140,13 @@ def flags_to_text(flags):
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return ' '.join(text_flags)
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def dnsping(host, server, dnsrecord, timeout, count, use_tcp=False, use_edns=False):
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def random_string(min_length=5, max_length=10):
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char_set = string.ascii_letters + string.digits
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length = random.randint(min_length, max_length)
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return ''.join(map(lambda unused: random.choice(char_set), range(length)))
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def dnsping(host, server, dnsrecord, timeout, count, use_tcp=False, use_edns=False, force_miss=False):
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resolver = dns.resolver.Resolver()
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resolver.nameservers = [server]
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resolver.timeout = timeout
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@ -156,12 +165,25 @@ def dnsping(host, server, dnsrecord, timeout, count, use_tcp=False, use_edns=Fal
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if shutdown: # user pressed CTRL+C
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break
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try:
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answers = resolver.query(host, dnsrecord, tcp=use_tcp,
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if force_miss:
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fqdn = "_dnseval_%s_.%s" % (random_string(), host)
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print(fqdn)
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else:
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fqdn = host
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stime = time.perf_counter()
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answers = resolver.query(fqdn, dnsrecord, tcp=use_tcp,
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raise_on_no_answer=False) # todo: response validation in future
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except (dns.resolver.NoNameservers, dns.resolver.NoAnswer):
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break
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except dns.resolver.Timeout:
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pass
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except dns.resolver.NXDOMAIN:
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etime = time.perf_counter()
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if force_miss:
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elapsed = (etime - stime) * 1000 # convert to milliseconds
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response_times.append(elapsed)
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else:
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elapsed = answers.response.time * 1000 # convert to milliseconds
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response_times.append(elapsed)
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@ -210,13 +232,15 @@ def main():
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fromfile = False
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use_tcp = False
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use_edns = True
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force_miss = False
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verbose = False
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color_mode = False
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hostname = 'wikipedia.org'
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try:
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opts, args = getopt.getopt(sys.argv[1:], "hf:c:t:w:TevC",
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["help", "file=", "count=", "type=", "wait=", "tcp", "edns", "verbose", "color"])
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opts, args = getopt.getopt(sys.argv[1:], "hf:c:t:w:TevCm",
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["help", "file=", "count=", "type=", "wait=", "tcp", "edns", "verbose", "color",
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"force-miss"])
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except getopt.GetoptError as err:
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print(err)
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usage()
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@ -236,6 +260,8 @@ def main():
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fromfile = True
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elif o in ("-w", "--wait"):
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waittime = int(a)
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elif o in ("-m", "--cache-miss"):
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force_miss = True
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elif o in ("-t", "--type"):
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dnsrecord = a
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elif o in ("-T", "--tcp"):
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@ -282,25 +308,29 @@ def main():
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ipaddress.ip_address(server)
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except ValueError: # so it is not a valid IPv4 or IPv6 address, so try to resolve host name
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try:
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s = socket.getaddrinfo(server, port=None)[1][4][0]
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resolver = socket.getaddrinfo(server, port=None)[1][4][0]
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except OSError:
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print('Error: cannot resolve hostname:', server)
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s = None
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resolver = None
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except:
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pass
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else:
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s = server
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resolver = server
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if not s:
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if not resolver:
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continue
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try:
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(s, r_avg, r_min, r_max, r_stddev, r_lost_percent, flags, ttl, answers) = dnsping(hostname, s,
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(resolver, r_avg, r_min, r_max, r_stddev, r_lost_percent, flags, ttl, answers) = dnsping(
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hostname,
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resolver,
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dnsrecord,
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waittime,
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count,
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use_tcp=use_tcp,
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use_edns=use_edns)
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use_edns=use_edns,
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force_miss=force_miss
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)
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except dns.resolver.NXDOMAIN:
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print('%-15s NXDOMAIN' % server)
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continue
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@ -308,7 +338,7 @@ def main():
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print('%s: %s' % (server, e))
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continue
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s = server.ljust(width + 1)
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resolver = server.ljust(width + 1)
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text_flags = flags_to_text(flags)
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s_ttl = str(ttl)
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@ -320,7 +350,8 @@ def main():
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else:
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l_color = color.N
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print("%s %-8.3f %-8.3f %-8.3f %-8.3f %s%%%-3d%s %-8s %21s" % (
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s, r_avg, r_min, r_max, r_stddev, l_color, r_lost_percent, color.N, s_ttl, text_flags), flush=True)
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resolver, r_avg, r_min, r_max, r_stddev, l_color, r_lost_percent, color.N, s_ttl, text_flags),
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flush=True)
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if verbose and hasattr(answers, 'response'):
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ans_index = 1
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for answer in answers.response.answer:
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