mirror of
https://github.com/firestar5683/StarPilot.git
synced 2026-11-09 22:13:43 +08:00
Danny
192 lines
6.2 KiB
Python
192 lines
6.2 KiB
Python
"""A pure python implementation of multicast DNS service discovery.
|
|
|
|
Licensed under LGPL-2.1-or-later; see COPYING for details. This file is
|
|
part of a continuously modified work; modification dates are recorded
|
|
in the project's git history.
|
|
"""
|
|
|
|
from __future__ import annotations
|
|
|
|
import re
|
|
import socket
|
|
|
|
_BROWSER_TIME = 10000 # ms
|
|
_CHECK_TIME = 500 # ms
|
|
_LISTENER_TIME = 200 # ms
|
|
_REGISTER_TIME = 225 # ms
|
|
_UNREGISTER_TIME = 125 # ms
|
|
_DUPLICATE_PACKET_SUPPRESSION_INTERVAL = 1000 # ms
|
|
# Per-listener bounded recency window. 16 is large enough to defeat
|
|
# the alternating-payload bypass (RFC 6762 §6.2, issue #1724 — even a
|
|
# rotation of a dozen distinct payloads still dedups), and small
|
|
# enough that the dict bookkeeping per miss stays cheap under a
|
|
# hostile flood.
|
|
_RECENT_PACKETS_MAX = 16
|
|
_DUPLICATE_QUESTION_INTERVAL = 999 # ms # Must be 1ms less than _DUPLICATE_PACKET_SUPPRESSION_INTERVAL
|
|
_CACHE_CLEANUP_INTERVAL = 10 # s
|
|
_LOADED_SYSTEM_TIMEOUT = 10 # s
|
|
_STARTUP_TIMEOUT = 9 # s must be lower than _LOADED_SYSTEM_TIMEOUT
|
|
_ONE_SECOND = 1000 # ms
|
|
|
|
# If the system is loaded or the event
|
|
# loop was blocked by another task that was doing I/O in the loop
|
|
# (shouldn't happen but it does in practice) we need to give
|
|
# a buffer timeout to ensure a coroutine can finish before
|
|
# the future times out
|
|
|
|
|
|
_MDNS_ADDR = "224.0.0.251"
|
|
_MDNS_ADDR6 = "ff02::fb"
|
|
_MDNS_PORT = 5353
|
|
_DNS_PORT = 53
|
|
_DNS_HOST_TTL = 120 # two minute for host records (A, SRV etc) as-per RFC6762
|
|
_DNS_OTHER_TTL = 4500 # 75 minutes for non-host records (PTR, TXT etc) as-per RFC6762
|
|
# Currently we enforce a minimum TTL for PTR records to avoid
|
|
# ServiceBrowsers generating excessive queries refresh queries.
|
|
# Apple uses a 15s minimum TTL, however we do not have the same
|
|
# level of rate limit and safe guards so we use 1/4 of the recommended value
|
|
_DNS_PTR_MIN_TTL = 1125
|
|
|
|
# Upper bound on the number of records the DNSCache will hold before it
|
|
# starts evicting the closest-to-expiration entry to make room for new
|
|
# arrivals. Bounds the memory a malicious LAN peer can force the cache
|
|
# to retain by multicasting many unique-name records.
|
|
_MAX_CACHE_RECORDS = 10000
|
|
|
|
# Upper bound on the number of entries QuestionHistory will hold between
|
|
# the periodic 10s cache-cleanup ticks. Bounds the memory a malicious LAN
|
|
# peer can force the duplicate-question-suppression history to retain by
|
|
# flooding distinct questions (RFC 6762 §7.3, defense-in-depth).
|
|
_MAX_QUESTION_HISTORY_ENTRIES = 10000
|
|
|
|
# Per-entry cap on the number of known-answer records QuestionHistory
|
|
# will retain. Each TC-deferred reassembly can carry up to ~12k records
|
|
# (~750 records/packet x _MAX_DEFERRED_PER_ADDR fragments), and the
|
|
# resulting set is stored by reference under each non-unicast question
|
|
# in the history dict; without a per-entry cap a LAN attacker can pin
|
|
# hundreds of MB across the _MAX_QUESTION_HISTORY_ENTRIES dimension.
|
|
# 256 is well above any RFC-realistic known-answer list for a single
|
|
# question; oversized payloads are dropped from the history (no
|
|
# suppression for that one query) rather than truncated, since a
|
|
# truncated stored set would over-suppress legitimate follow-up
|
|
# queries (`suppresses()` returns True when stored set is a subset of
|
|
# the incoming known-answers, so a smaller stored set matches more
|
|
# easily).
|
|
_MAX_KNOWN_ANSWERS_PER_HISTORY_ENTRY = 256
|
|
|
|
# Per-addr cap on the number of truncated (TC-bit) packets retained for
|
|
# RFC 6762 §18.5 reassembly. The spec anticipates only a handful of
|
|
# segments per truncated query; 16 is well above legitimate need and
|
|
# keeps the per-arrival dedup scan a constant-time cost under a flood.
|
|
_MAX_DEFERRED_PER_ADDR = 16
|
|
|
|
# Per-listener cap on the number of distinct addrs with in-flight
|
|
# TC-deferral state. Each entry can hold up to _MAX_DEFERRED_PER_ADDR
|
|
# packets of up to _MAX_MSG_ABSOLUTE bytes; 512 leaves headroom for a
|
|
# legitimate burst (LAN-wide power-resume / boot storm where many
|
|
# devices announce at once) while bounding worst-case memory at
|
|
# ~72 MB even when a peer floods with spoofed source IPs.
|
|
_MAX_DEFERRED_ADDRS = 512
|
|
|
|
_DNS_PACKET_HEADER_LEN = 12
|
|
|
|
_MAX_MSG_ABSOLUTE = 8966
|
|
_MAX_MSG_TYPICAL = 1460
|
|
|
|
# DNS header flag bits, RFC 1035 section 4.1.1 and RFC 6762 section 18
|
|
_FLAGS_AA = 0x0400
|
|
_FLAGS_AD = 0x0020
|
|
_FLAGS_CD = 0x0010
|
|
_FLAGS_QR_MASK = 0x8000
|
|
_FLAGS_QR_QUERY = 0x0000
|
|
_FLAGS_QR_RESPONSE = 0x8000
|
|
_FLAGS_RA = 0x0080
|
|
_FLAGS_RD = 0x0100
|
|
_FLAGS_TC = 0x0200
|
|
_FLAGS_Z = 0x0040
|
|
|
|
|
|
_CLASS_IN = 1
|
|
_CLASS_CS = 2
|
|
_CLASS_CH = 3
|
|
_CLASS_HS = 4
|
|
_CLASS_NONE = 254
|
|
_CLASS_ANY = 255
|
|
_CLASS_MASK = 0x7FFF
|
|
_CLASS_UNIQUE = 0x8000
|
|
_CLASS_IN_UNIQUE = _CLASS_IN | _CLASS_UNIQUE
|
|
|
|
_TYPE_A = 1
|
|
_TYPE_NS = 2
|
|
_TYPE_MD = 3
|
|
_TYPE_MF = 4
|
|
_TYPE_CNAME = 5
|
|
_TYPE_SOA = 6
|
|
_TYPE_MB = 7
|
|
_TYPE_MG = 8
|
|
_TYPE_MR = 9
|
|
_TYPE_NULL = 10
|
|
_TYPE_WKS = 11
|
|
_TYPE_PTR = 12
|
|
_TYPE_HINFO = 13
|
|
_TYPE_MINFO = 14
|
|
_TYPE_MX = 15
|
|
_TYPE_TXT = 16
|
|
_TYPE_AAAA = 28
|
|
_TYPE_SRV = 33
|
|
_TYPE_NSEC = 47
|
|
_TYPE_ANY = 255
|
|
|
|
|
|
# Wire values mapped to short human readable names, used only for reprs
|
|
# and debug logging; _type_label and _class_label in _dns.py supply the
|
|
# unknown-value fallback. Sorted by mnemonic.
|
|
_CLASSES = {
|
|
_CLASS_ANY: "any",
|
|
_CLASS_CH: "ch",
|
|
_CLASS_CS: "cs",
|
|
_CLASS_HS: "hs",
|
|
_CLASS_IN: "in",
|
|
_CLASS_NONE: "none",
|
|
}
|
|
_TYPES = {
|
|
_TYPE_A: "a",
|
|
_TYPE_AAAA: "aaaa",
|
|
_TYPE_ANY: "any",
|
|
_TYPE_CNAME: "cname",
|
|
_TYPE_HINFO: "hinfo",
|
|
_TYPE_MB: "mb",
|
|
_TYPE_MD: "md",
|
|
_TYPE_MF: "mf",
|
|
_TYPE_MG: "mg",
|
|
_TYPE_MINFO: "minfo",
|
|
_TYPE_MR: "mr",
|
|
_TYPE_MX: "mx",
|
|
_TYPE_NS: "ns",
|
|
_TYPE_NSEC: "nsec",
|
|
_TYPE_NULL: "null",
|
|
_TYPE_PTR: "ptr",
|
|
_TYPE_SOA: "soa",
|
|
_TYPE_SRV: "srv",
|
|
_TYPE_TXT: "txt",
|
|
_TYPE_WKS: "wks",
|
|
}
|
|
|
|
_ADDRESS_RECORD_TYPES = {_TYPE_A, _TYPE_AAAA}
|
|
|
|
_HAS_A_TO_Z = re.compile(r"[A-Za-z]")
|
|
_HAS_ONLY_A_TO_Z_NUM_HYPHEN = re.compile(r"^[A-Za-z0-9\-]+$")
|
|
_HAS_ONLY_A_TO_Z_NUM_HYPHEN_UNDERSCORE = re.compile(r"^[A-Za-z0-9\-\_]+$")
|
|
_HAS_ASCII_CONTROL_CHARS = re.compile(r"[\x00-\x1f\x7f]")
|
|
|
|
_EXPIRE_REFRESH_TIME_PERCENT = 75
|
|
|
|
_LOCAL_TRAILER = ".local."
|
|
_TCP_PROTOCOL_LOCAL_TRAILER = "._tcp.local."
|
|
_NONTCP_PROTOCOL_LOCAL_TRAILER = "._udp.local."
|
|
|
|
# https://datatracker.ietf.org/doc/html/rfc6763#section-9
|
|
_SERVICE_TYPE_ENUMERATION_NAME = "_services._dns-sd._udp.local."
|
|
|
|
_IPPROTO_IPV6 = socket.IPPROTO_IPV6
|