[sctp] fix import warning for crc32c

The crc32c package renamed the `crc32` function to `crc32c` as in
release 2.1. It is also no longer necessary to set `CRC32C_SW_MODE`
since release 2.0.

setup.py

@@ -21,7 +21,7 @@
     "aioice>=0.7.0,<0.8.0",
     "av>=8.0.0,<9.0.0",
     "cffi>=1.0.0",
-    "crc32c",
+    "crc32c>=2.1",
     "cryptography>=2.2",
     'dataclasses; python_version < "3.7"',
     "pyee>=6.0.0",

src/aiortc/rtcsctptransport.py

@@ -22,20 +22,14 @@
     no_type_check,
 )
 
+from crc32c import crc32c
 from pyee import AsyncIOEventEmitter
 
 from .exceptions import InvalidStateError
 from .rtcdatachannel import RTCDataChannel, RTCDataChannelParameters
 from .rtcdtlstransport import RTCDtlsTransport
 from .utils import random32, uint16_add, uint16_gt, uint32_gt, uint32_gte
 
-try:
-    from crc32c import crc32
-except ImportError:  # pragma: no cover
-    os.environ["CRC32C_SW_MODE"] = "1"
-    from crc32c import crc32
-
-
 logger = logging.getLogger("sctp")
 
 # local constants
@@ -406,7 +400,7 @@ def parse_packet(data: bytes) -> Tuple[int, int, int, List[Any]]:
 
     # verify checksum
     checksum = unpack_from("<L", data, 8)[0]
-    if checksum != crc32(data[0:8] + b"\x00\x00\x00\x00" + data[12:]):
+    if checksum != crc32c(data[0:8] + b"\x00\x00\x00\x00" + data[12:]):
         raise ValueError("SCTP packet has invalid checksum")
 
     chunks = []
@@ -426,7 +420,7 @@ def serialize_packet(
 ) -> bytes:
     header = pack("!HHL", source_port, destination_port, verification_tag)
     data = bytes(chunk)
-    checksum = crc32(header + b"\x00\x00\x00\x00" + data)
+    checksum = crc32c(header + b"\x00\x00\x00\x00" + data)
     return header + pack("<L", checksum) + data
 
 

stubs/crc32c.pyi

@@ -1 +1 @@
-def crc32(data: bytes) -> int: ...
+def crc32c(data: bytes) -> int: ...