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Reduce dns protocol attributes and add slots #987

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Merged
bdraco merged 2 commits into from
Sep 19, 2021
Merged

Reduce dns protocol attributes and add slots #987

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efd3619
Reduce DNSIncoming attributes and add slots
bdraco Sep 19, 2021
0f4767e
slots for outgoing as well
bdraco Sep 19, 2021
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53 changes: 42 additions & 11 deletions zeroconf/_protocol.py
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Original file line number Diff line number Diff line change
Expand Up @@ -87,14 +87,30 @@ class DNSIncoming(DNSMessage, QuietLogger):

"""Object representation of an incoming DNS packet"""

__slots__ = (
'offset',
'data',
'data_len',
'name_cache',
'questions',
'_answers',
'id',
'num_questions',
'num_answers',
'num_authorities',
'num_additionals',
'valid',
'now',
'scope_id',
)

def __init__(self, data: bytes, scope_id: Optional[int] = None, now: Optional[float] = None) -> None:
"""Constructor from string holding bytes of packet"""
super().__init__(0)
self.offset = 0
self.data = data
self.data_len = len(data)
self.name_cache: Dict[int, List[str]] = {}
self.seen_pointers: Set[int] = set()
self.questions: List[DNSQuestion] = []
self._answers: List[DNSRecord] = []
self.id = 0
Expand Down Expand Up @@ -162,10 +178,9 @@ def read_header(self) -> None:

def read_questions(self) -> None:
"""Reads questions section of packet"""
for _ in range(self.num_questions):
name = self.read_name()
type_, class_ = self.unpack(b'!HH', 4)
self.questions.append(DNSQuestion(name, type_, class_))
self.questions = [
DNSQuestion(self.read_name(), *self.unpack(b'!HH', 4)) for _ in range(self.num_questions)
]

def read_character_string(self) -> bytes:
"""Reads a character string from the packet"""
Expand Down Expand Up @@ -278,14 +293,14 @@ def read_bitmap(self, end: int) -> List[int]:
def read_name(self) -> str:
"""Reads a domain name from the packet."""
labels: List[str] = []
self.seen_pointers.clear()
self.offset = self._decode_labels_at_offset(self.offset, labels)
seen_pointers: Set[int] = set()
self.offset = self._decode_labels_at_offset(self.offset, labels, seen_pointers)
name = ".".join(labels) + "."
if len(name) > MAX_NAME_LENGTH:
raise IncomingDecodeError(f"DNS name {name} exceeds maximum length of {MAX_NAME_LENGTH}")
return name

def _decode_labels_at_offset(self, off: int, labels: List[str]) -> int:
def _decode_labels_at_offset(self, off: int, labels: List[str], seen_pointers: Set[int]) -> int:
# This is a tight loop that is called frequently, small optimizations can make a difference.
while off < self.data_len:
length = self.data[off]
Expand All @@ -307,12 +322,12 @@ def _decode_labels_at_offset(self, off: int, labels: List[str]) -> int:
raise IncomingDecodeError(f"DNS compression pointer at {off} points to {link} beyond packet")
if link == off:
raise IncomingDecodeError(f"DNS compression pointer at {off} points to itself")
if link in self.seen_pointers:
if link in seen_pointers:
raise IncomingDecodeError(f"DNS compression pointer at {off} was seen again")
self.seen_pointers.add(link)
seen_pointers.add(link)
linked_labels = self.name_cache.get(link, [])
if not linked_labels:
self._decode_labels_at_offset(link, linked_labels)
self._decode_labels_at_offset(link, linked_labels, seen_pointers)
self.name_cache[link] = linked_labels
labels.extend(linked_labels)
if len(labels) > MAX_DNS_LABELS:
Expand All @@ -326,6 +341,22 @@ class DNSOutgoing(DNSMessage):

"""Object representation of an outgoing packet"""

__slots__ = (
'finished',
'id',
'multicast',
'packets_data',
'names',
'data',
'size',
'allow_long',
'state',
'questions',
'answers',
'authorities',
'additionals',
)

def __init__(self, flags: int, multicast: bool = True, id_: int = 0) -> None:
super().__init__(flags)
self.finished = False
Expand Down