| Some Information for Contributors |
| --------------------------------- |
| You want to contribute to Tcpdump, Thanks! |
| Please, read these lines. |
| |
| 1) Fork the Tcpdump repository on GitHub from |
| https://github.com/the-tcpdump-group/tcpdump |
| (See https://help.github.com/articles/fork-a-repo/) |
| |
| 2) Setup an optional Travis-CI build |
| You can setup a travis build for your fork. So, you can test your changes |
| on Linux and OSX before sending pull requests. |
| (See http://docs.travis-ci.com/user/getting-started/) |
| |
| 3) Clone your repository |
| git clone https://github.com/<username>/tcpdump.git |
| |
| 4) Do a 'touch .devel' in your working directory. |
| Currently, the effect is |
| a) add (via configure, in Makefile) some warnings options ( -Wall |
| -Wmissing-prototypes -Wstrict-prototypes, ...) to the compiler if it |
| supports these options, |
| b) have the Makefile support "make depend" and the configure script run it. |
| |
| 5) Configure and build |
| ./configure && make -s && make check |
| |
| 6) Add/update sample.pcap files |
| We use tests directory to do regression tests on the dissection of captured |
| packets, by running tcpdump against a savefile sample.pcap, created with -w |
| option and comparing the results with a text file sample.out giving the |
| expected results. |
| |
| 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 build by: |
| (cd tests && ../tcpdump -n -r sample.pcap tcpdump-options > sample.out) |
| |
| It is often useful to have test outputs with different verbosity levels |
| (none, -v, -vv, -vvv, etc.) depending on the code. |
| |
| 7) Test with 'make check' |
| Don't send a pull request if 'make check' gives failed tests. |
| |
| 8) Rebase your commits against upstream/master |
| (To keep linearity) |
| |
| 9) Initiate and send a pull request |
| (See https://help.github.com/articles/using-pull-requests/) |
| |
| Some remarks |
| ------------ |
| a) A thorough reading of some other printers code is useful. |
| |
| b) Put the normative reference if any as comments (RFC, etc.). |
| |
| c) Put the format of packets/headers/options as comments. |
| |
| d) The printer may receive incomplete packet in the buffer, truncated at any |
| random position, for example by capturing with '-s size' option. |
| Thus use ND_TTEST, ND_TTEST2, ND_TCHECK or ND_TCHECK2 for bound checking. |
| For ND_TCHECK2: |
| Define : static const char tstr[] = " [|protocol]"; |
| Define a label: trunc |
| Print with: ND_PRINT((ndo, "%s", tstr)); |
| 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. |
| |
| e) 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). |
| Print with: ND_PRINT((ndo, "%s", istr)); /* to print " (invalid)" */ |
| |
| f) Use 'struct tok' for indexed strings and print them with |
| tok2str() or bittok2str() (for flags). |
| |
| g) Avoid empty lines in output of printers. |
| |
| h) A commit message must have: |
| First line: Capitalized short summary in the imperative (70 chars or less) |
| |
| Body: Detailed explanatory text, if necessary. Fold it to approximately |
| 72 characters. There must be an empty line separating the summary from |
| the body. |
| |
| i) Avoid non-ASCII characters in code and commit messages. |
| |
| j) Use the style of the modified sources. |
| |
| k) Don't mix declarations and code |
| |
| l) Don't use // for comments |
| Not all C compilers accept C++/C99 comments by default. |
| |
| m) Avoid trailing tabs/spaces |