Fix a multithreading issue in writing pcap files #204
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When there are separate threads that are sending and receiving packets, both threads may try to write the packet data to the pcap file. This causes the packet to get interleaved, thus basically making it corrupted and unable to be read by tcpdump, wireshark, etc. This is happening due to a missing lock on `self.cvar`. Fix it by wrapping the write call in the `send` method and the initial assignment in `start_pcap` method with a lock on `self.cvar`. Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>
jafingerhut
approved these changes
Jan 22, 2024
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Looks like very low risk changes to me, in that the changes simply add acquisition of the lock asociated with self.cvar in more places than it was before.
Testing that these are the only places useful to add with self.cvar would require a lot more careful investigation of the entire class definitions, which I have not done.
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When there are separate threads that are sending and receiving packets, both threads may try to write the packet data to the pcap file. This causes the packet to get interleaved, thus basically making it corrupted and unable to be read by tcpdump, wireshark, etc.
This is happening due to a missing lock on
self.cvar. Fix it by wrapping the write call in thesendmethod and the initial assignment instart_pcapmethod with a lock onself.cvar.