HedongGao opened a new pull request, #17698:
URL: https://github.com/apache/nuttx/pull/17698
## Summary
According to RFC768 page 2, length feild is the length in octets of this
user datagram including this header and the data.
So, Check the length field with the real user data, return error if it
failed.
## Impact
Without modification function, it will not have an impact on legitimate
messages.
## Testing
Enable the CONFIG_EXAMPLE_UDP compilation option, set up the SIM
environment, and run a UDP server on the SIM side.
As a UDP client, the host sends messages to the server, including 5 valid
UDP length messages and 5 invalid UDP length messages. It can be seen that the
messages with incorrect lengths are discarded by the server, while the messages
with correct lengths are received by the server.
`
from scapy.all import Ether, IP, UDP, sendp
import random
SRC_MAC = "fa:b1:d9:6d:a0:d3"
DST_MAC = "42:e1:c4:3f:48:dd"
SRC_IP = "10.0.1.1"
DST_IP = "10.0.1.2"
DST_PORT = 8888
SRC_PORT = random.randint(1024, 65535)
TOTAL_PACKETS = 10
ERROR_PACKETS = 5
def generate_udp_packet(is_normal: bool, data: bytes) -> Ether:
real_udp_length = 8 + len(data)
if not is_normal:
error_offset = random.choice([-1, 1]) * random.randint(5, 10)
udp_length = real_udp_length + error_offset
udp_length = max(8, udp_length)
else:
udp_length = real_udp_length
ether = Ether(src=SRC_MAC, dst=DST_MAC)
ip = IP(src=SRC_IP, dst=DST_IP)
udp = UDP(
sport=SRC_PORT,
dport=DST_PORT,
len=udp_length
)
packet = ether / ip / udp / data
return packet
if __name__ == "__main__":
for i in range(TOTAL_PACKETS):
data = f"TestPacket_{i+1}".encode("utf-8")
is_normal = i >= ERROR_PACKETS
packet = generate_udp_packet(is_normal, data)
sendp(packet, iface="eth0", verbose=1)
real_length = 8 + len(data)
udp_length = packet[UDP].len
status = "Normal" if is_normal else "Abnormal"
print(f"Sending {i+1}th packet | Status: {status} | Actual UDP
length: {real_length} | Header length field: {udp_length}")
`
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