To report a security issue (segfault, buffer overflow, infinite loop, arbitrary code execution etc) please send an e-mail to security@tcpdump.org, do not use the bug tracker!
To report a non-security problem (failure to compile, failure to capture packets properly, missing support for a network interface type or DLT) please check first that it reproduces with the latest stable release of libpcap. If it does, please check that the problem reproduces with the current git master branch of libpcap. If it does (and it is not a security-related problem, otherwise see above), please navigate to https://github.com/the-tcpdump-group/libpcap/issues and check if the problem has already been reported. If it has not, please open a new issue and provide the following details:
Please note that if you know exactly how to solve the problem and the solution would not be too intrusive, it would be best to contribute some development time and open a pull request instead.
Still not sure how to do? Feel free to subscribe to the mailing list tcpdump-workers@lists.tcpdump.org and ask!