Socket recvfrom buffer too small for receiving responses to large ICMP echo requests #40
Description
Issue
In icmplib/sockets.py, the response buffer allocated by the receive method isn't big enough, when the echo request payload_size is greater than 996 bytes.
response = self._sock.recvfrom(1024)
Using examples/ping.py for testing:
-
On Ubuntu (root), the calculated
bytes_receivedvalue is incorrect, asresponseis truncated. -
On Windows 10, the
self._sock.recvfrom(1024)triggers the below exception, which is swallowed within theicmplib/ping.pypingmethod by:except ICMPLibError: passICMPLibError: [WinError 10040] A message sent on a datagram socket was larger than the internal message buffer or some other network limit, or the buffer used to receive a datagram into was smaller than the datagram itself
The flow on effect is that RTTs aren't calculated, and the
host.is_aliveis incorrectly set toFalse,
Fix
Simply allocating a buffer that can hold the max possible ICMP packet size (i.e. IPv4 max packet size) seems to work:
response = self._sock.recvfrom(65535)
Example
(Windows), sending 3 pings:
(venv_icmplib) D:\icmplib\examples>python ping.py
ICMP payload size: 996
host.address: 10.0.0.2
host.min_rtt: 1.0
host.avg_rtt: 1.0
host.max_rtt: 1.279
host.rtts: [1.2786388397216797, 0.9996891021728516, 0.9996891021728516]
host.packets_sent: 3
host.packets_received: 3
host.packet_loss 0.0
host.jitter: 0.139
host.is_alive: True
(venv_icmplib) D:\icmplib\examples>python ping.py
ICMP payload size: 997
host.address: 10.0.0.2
host.min_rtt: 0.0
host.avg_rtt: 0.0
host.max_rtt: 0.0
host.rtts: []
host.packets_sent: 3
host.packets_received: 0
host.packet_loss 1.0
host.jitter: 0.0
host.is_alive: False
This is a nice tool, hope this helps!