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diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md new file mode 100644 index 0000000..26f226e --- /dev/null +++ b/CONTRIBUTING.md @@ -0,0 +1,191 @@ +# Some Information for Contributors +Thank you for considering to make a contribution to tcpdump! Please use the +guidelines below to achieve the best results and experience for everyone. + +## How to report bugs and other problems +**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, incorrect output in the +protocol printout, missing support for a particular protocol etc) please check +first that it reproduces with the latest stable release of tcpdump and the latest +stable release of libpcap. If it does, please check that the problem reproduces +with the current git master branch of tcpdump and the current git master branch of +libpcap. If it does (and it is not a security-related problem, otherwise see +above), please navigate to the +[bug tracker](https://github.com/the-tcpdump-group/tcpdump/issues) +and check if the problem has already been reported. If it has not, please open +a new issue and provide the following details: + +* tcpdump and libpcap version (`tcpdump --version`) +* operating system name and version and any other details that may be relevant + (`uname -a`, compiler name and version, CPU type etc.) +* custom `configure`/`cmake` flags, if any +* statement of the problem +* steps to reproduce + +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 to open a pull request instead as discussed below. + +Still not sure how to do? Feel free to +[subscribe to the mailing list](https://www.tcpdump.org/#mailing-lists) +and ask! + + +## How to add new code and to update existing code + +0) Check that there isn't a pull request already opened for the changes you + intend to make. + +1) [Fork](https://help.github.com/articles/fork-a-repo/) the Tcpdump + [repository](https://github.com/the-tcpdump-group/tcpdump). + +2) The easiest way to test your changes on multiple operating systems and + architectures is to let the upstream CI test your pull request (more on + this below). + +3) Setup your git working copy + ``` + git clone https://github.com/<username>/tcpdump.git + cd tcpdump + git remote add upstream https://github.com/the-tcpdump-group/tcpdump + git fetch upstream + ``` + +4) Do a `touch .devel` in your working directory. + Currently, the effect is + * add (via `configure`, in `Makefile`) some warnings options (`-Wall`, + `-Wmissing-prototypes`, `-Wstrict-prototypes`, ...) to the compiler if it + supports these options, + * have the `Makefile` support `make depend` and the `configure` script run it. + +5) Configure and build + ``` + ./configure && make -s && make check + ``` + +6) Add/update tests + The `tests` directory contains regression tests of the dissection of captured + packets. Those captured packets were saved running tcpdump with option + `-w sample.pcap`. Additional options, such as `-n`, are used to create relevant + and reproducible output; `-#` is used to indicate which particular packets + have output that differs. The tests are run with the `TZ` environment + variable set to `GMT0`, so that UTC, rather than the local time where the + tests are being run, is used when "local time" values are printed. The + actual test compares the current text output with the expected result + (`sample.out`) saved from a previous version. + + Any new/updated fields in a dissector must be present in a `sample.pcap` file + and the corresponding output file. + + Configuration is set in `tests/TESTLIST`. + Each line in this file has the following format: + ``` + test-name sample.pcap sample.out tcpdump-options + ``` + + The `sample.out` file can be produced as follows: + ``` + (cd tests && TZ=GMT0 ../tcpdump -# -n -r sample.pcap tcpdump-options > sample.out) + ``` + + Or, for convenience, use `./update-test.sh test-name` + + It is often useful to have test outputs with different verbosity levels + (none, `-v`, `-vv`, `-vvv`, etc.) depending on the code. + +7) Test using `make check` (current build options) and `./build_matrix.sh` + (a multitude of build options, build systems and compilers). If you can, + test on more than one operating system. Don't send a pull request until + all tests pass. + +8) Try to rebase your commits to keep the history simple. + ``` + git fetch upstream + git rebase upstream/master + ``` + (If the rebase fails and you cannot resolve, issue `git rebase --abort` + and ask for help in the pull request comment.) + +9) Once 100% happy, put your work into your forked repository using `git push`. + +10) [Initiate and send](https://help.github.com/articles/using-pull-requests/) + a pull request. + This will trigger the upstream repository CI tests. + + +## Code style and generic remarks +* A thorough reading of some other printers code is useful. + +* Put the normative reference if any as comments (RFC, etc.). + +* Put the format of packets/headers/options as comments if there is no + published normative reference. + +* The printer may receive incomplete packet in the buffer, truncated at any + random position, for example by capturing with `-s size` option. + If your code reads and decodes every byte of the protocol packet, then to + ensure proper and complete bounds checks it would be sufficient to read all + packet data using the `GET_*()` macros, typically: + ``` + GET_U_1(p) + GET_S_1(p) + GET_BE_U_n(p), n in { 2, 3, 4, 5, 6, 7, 8 } + GET_BE_S_n(p), n in { 2, 3, 4, 5, 6, 7, 8 } + ``` + If your code uses the macros above only on some packet data, then the gaps + would have to be bounds-checked using the `ND_TCHECK_*()` macros: + ``` + ND_TCHECK_n(p), n in { 1, 2, 3, 4, 5, 6, 7, 8, 16 } + ND_TCHECK_SIZE(p) + ND_TCHECK_LEN(p, l) + ``` + For the `ND_TCHECK_*` macros (if not already done): + * Assign: `ndo->ndo_protocol = "protocol";` + * Define: `ND_LONGJMP_FROM_TCHECK` before including `netdissect.h` + * Make sure that the intersection of `GET_*()` and `ND_TCHECK_*()` is minimal, + but at the same time their union covers all packet data in all cases. + + You can test the code via: + ``` + sudo ./tcpdump -s snaplen [-v][v][...] -i lo # in a terminal + sudo tcpreplay -i lo sample.pcap # in another terminal + ``` + You should try several values for snaplen to do various truncation. + +* Do invalid packet checks in code: Think that your code can receive in input + not only a valid packet but any arbitrary random sequence of octets (packet + * built malformed originally by the sender or by a fuzz tester, + * became corrupted in transit or for some other reason). + + Print with: `nd_print_invalid(ndo); /* to print " (invalid)" */` + +* Use `struct tok` for indexed strings and print them with + `tok2str()` or `bittok2str()` (for flags). + +* Avoid empty lines in output of printers. + +* A commit message must have: + ``` + First line: Capitalized short summary in the imperative (50 chars or less) + + If the commit concerns a protocol, the summary line must start with + "protocol: ". + + Body: Detailed explanatory text, if necessary. Fold it to approximately + 72 characters. There must be an empty line separating the summary from + the body. + ``` + +* Avoid non-ASCII characters in code and commit messages. + +* Use the style of the modified sources. + +* Don't mix declarations and code. + +* Don't use `//` for comments. + Not all C compilers accept C++/C99 comments by default. + +* Avoid trailing tabs/spaces |