def mtu_path_is_safe(host, ipversion=None):
"""
Using tracepath, check to see if the MTU along the path to 'host'
gets any narrower than what it is locally.
Set 'ipversion' to 4 or 6 to force a particular IP version. If
not provided, the function will try to figure it out using the
resolver.
Returns a tuple of (boolean, status message).
"""
assert ipversion in [4, 6, None], "Invalid IP version"
if ipversion is None:
(ipversion, message) = ip_addr_version(host)
if ipversion is None:
return (False, message)
assert ipversion is not None, "No ip version; cannot proceed."
if ipversion == 6:
tracepath = "tracepath6"
else:
tracepath = "tracepath"
status, stdout, stderr = run_program([tracepath, host], timeout=30)
if status != 0:
return (False, "Error: %s" % (stderr.strip()))
mtu_match = re.compile("^.*pmtu ([0-9]+)")
mtus = []
for line in stdout.split("\n"):
matches = mtu_match.match(line)
if matches is not None:
mtu = int(matches.groups()[0])
mtus.append(mtu)
if not mtus:
return (False, "Found no MTU information in trace to %s" % (host))
if len(mtus) == 1:
return (False, "Found only one MTU in trace to %s" % (host))
initial_mtu = mtus[0]
last_low_mtu = initial_mtu
drops = []
for mtu in mtus[1:]:
if mtu < last_low_mtu:
drops.append(str(mtu))
last_low_mtu = mtu
if drops:
return "MTU along path drops from %d to %s" % (initial_mtu,
" to ".join(drops))
return (True, "%d+" % (initial_mtu))
def mtu_path_is_safe(host):
"""
Using tracepath, check to see if the MTU along the path to 'host'
gets any narrower than what it is locally.
Returns a tuple of (boolean, status message).
"""
status, stdout, stderr = run_program(["tracepath", host], timeout=30)
if status != 0:
return (False, "Error: %s" % (stderr.strip()))
mtu_match = re.compile("^.*pmtu ([0-9]+)")
mtus = []
for line in stdout.split("\n"):
matches = mtu_match.match(line)
if matches is not None:
mtu = int(matches.groups()[0])
mtus.append(mtu)
if not mtus:
return (False, "Found no MTU information in trace to %s" % (host))
if len(mtus) == 1:
return (False, "Found only one MTU in trace to %s" % (host))
initial_mtu = mtus[0]
last_low_mtu = initial_mtu
drops = []
for mtu in mtus[1:]:
if mtu < last_low_mtu:
drops.append(str(mtu))
last_low_mtu = mtu
if drops:
return "MTU along path drops from %d to %s" % (initial_mtu,
" to ".join(drops))
return (True, "%d+" % (initial_mtu))
from program import parse_commands, run_program
lines = [l.strip() for l in open('input8').readlines()]
commands = parse_commands(lines)
acc, _ = run_program(commands)
print('Part 1:', acc)
for idx, (cmd, _) in enumerate(commands):
if cmd == 'nop':
commands[idx][0] = 'jmp'
elif cmd == 'jmp':
commands[idx][0] = 'nop'
acc, terminated = run_program(commands)
if terminated:
print('Part 2:', acc)
break
commands[idx][0] = cmd