# ISC DHCP Contributor's Guide So you found a bug in ISC DHCP or plan to develop an extension and want to send us a patch? Great! This page will explain how to contribute your changes smoothly. ## Writing a patch Before you start working on a patch or a new feature, it is a good idea to discuss it first with DHCP developers. You can post your questions to the [dhcp-workers](https://lists.isc.org/mailman/listinfo/dhcp-workers) or [dhcp-users](https://lists.isc.org/mailman/listinfo/dhcp-users) mailing lists. The dhcp-users is intended for users who are not interested in the internal workings or development details: it is OK to ask for feedback regarding new design or the best proposed solution to a certain problem. This is the best place to get user's feedback. The internal details, questions about the code and its internals are better asked on dhcp-workers. The dhcp-workers is a very low traffic list. OK, so you have written a patch? Great! Before you submit it, make sure that your code compiles. This may seem obvious, but there's more to it. You have surely checked that it compiles on your system, but ISC DHCP is a portable software. Besides Linux, it is compiled and used on relatively uncommon systems like OpenBSD. Will your code compile and work there? What about endianness? It is likely that you used a regular x86 architecture machine to write your patch, but the software is expected to run on many other architectures. For a complete list of systems we build on, you may take a look at the [Jenkins build farm report](https://jenkins.isc.org/view/isc-dhcp/). ## Running unit-tests One of the ground rules in all ISC projects is that every piece of code has to be tested. For newer projects, such as Kea, we require unit-test for almost every line of code. For older code, such as ISC DHCP, that was not developed with testability in mind, it's unfortunately impractical to require extensive unit-tests. Having said that, please think thoroughly if there is any way to develop unit-tests. The long term goal is to improve the situation. You should have also conducted some sort of system testing to verify that your changes do what you want. It would be extremely helpful if you can attach any configuration files (dhcpd and or dhclient), along with a step-by-step procedure to carry out the test(s). This will help us verify your changes as extend our own system tests. Building ISC DHCP code from the repository is slightly different than the release tarballs. One major difference is that it does not have BIND source bundled inside and those have to be downloaded separately. Fortunately, there's an easy to use script for that: ```bash sh util/bind.sh v4_4 ./configure --with-atf make ``` Make sure you have ATF (Automated Test Framework) installed in your system. For more information about ATF, please refer to /doc/devel/atf.dox. Note, running "make devel" in this directory will generate the documentation. To run the unit-tests, simply run: ```bash make check ``` If you happen to add new files or have modified any Makefile.am files, it is also a good idea to check if you haven't broken the distribution process: ```bash make distcheck ``` There are other useful switches which can be passed to configure. A complete list of all switches can be obtained with the command: ```bash ./configure --help ``` ## Create an issue Since you want to change something in ISC DHCP, there's a problem, deficiency or a missing feature. Quite often it is not clear why specific change is being made. The best way to explain it is to [create an issue here](https://gitlab.isc.org/isc-projects/dhcp/issues/new). We prefer the original submitter fill them as he or she has the best understanding of the purpose of the change and may have any extra information, e.g. "this patch fixes compilation issue on FreeBSD 10.1". If there there is no MR and no gitlab issue, we will create one. Depending on the subjective importance and urgency as perceived by the ISC engineer, the issue and/or MR will be assigned to one of the milestones. ## Merge Request (also known as sending your patch the right way) The first step in writing the patch or new feature should be to get the source code from our Git repository. The procedure is very easy and is [explained here](https://gitlab.isc.org/isc-projects/dhcp/wikis/gitlab-howto). While it is possible to provide a patch against the latest stable release, it makes the review process much easier if it is for latest code from the Git master branch. Since you won't get write access to the ISC DHCP repository, you should fork it and then commit your changes to your own repo. How you organize the work depends entirely on you, but it seems reasonable to create a branch rather than working on your master. Once you feel that your patch is ready, please commit your changes and push it to your copy of ISC DHCP repo. Then go to DHCP project and [submit a Merge Request](https://gitlab.isc.org/isc-projects/dhcp/merge_requests/new). TODO: I don't think this is necessary. If you can't access this link or don't see New Merge Request button on the [merge requests page](https://gitlab.isc.org/isc-projects/dhcp/merge_requests) or the link gives you 404 error, please ask on dhcp-users and someone will help you out. Once you submit it, someone from the DHCP development team will look at it and will get back to you. The dev team is very small, so it may take a while... ## If you really can't do MR on gitlab... Well, you are out of luck. There are other ways, but those are really awkward and the chances of your patch being ignored are really high. Anyway, here they are: - Create a ticket in the DHCP Gitlab (https://gitlab.isc.org/isc-projects/dhcp) and attach your patch to it. Sending a patch has a number of disadvantages. First, if you don't specify the base version against which it was created, one of ISC engineers will have to guess that or go through a series of trials and errors to find that out. If the code doesn't compile, the reviewer will not know if the patch is broken or maybe it was applied to incorrect base code. Another frequent problem is that it may be possible that the patch didn't include any new files you have added. - Send a patch to the dhcp-workers list. This is even worse, but still better than not getting the patch at all. The problem with this approach is that we don't know which version the patch was created against and there is no way to track it. So the chances of it being forgotten are high. Once a DHCP developer get to it, the first thing he/she will have to do is try to apply your patch, create a branch commit your changes and then open MR for it. ## Going through a review Once the MR is in the system, the action is on one of the ISC (and possibly other trusted) engineers. Sooner or later, one of ISC engineers will do the review. Here's the tricky part. One of ISC DHCP developers will review your patch, but it may not happen immediately. Unfortunately, developers are usually working under a tight schedule, so any extra unplanned review work may take a while sometimes. Having said that, we value external contributions very much and will do whatever we can to review patches in a timely manner. Don't get discouraged if your patch is not accepted after first review. To keep the code quality high, we use the same review processes for external patches as we do for internal code. It may take some cycles of review/updated patch submissions before the code is finally accepted. The nature of the review process is that it emphasizes areas that need improvement. If you are not used to the review process, you may get the impression that the feedback is negative. It is not: even the ISC developers seldom see reviews that say "All OK please merge". If we happen to have any comments that you as submitter are expected to address (and in the overwhelming majority of cases, we have), you will be asked to update your MR. It is not uncommon to see several rounds of such reviews, so this can get very complicated very quickly. Once the process is almost complete, the developer will likely ask you how you would like to be credited. The typical answers are by first and last name, by nickname, by company name or anonymously. Typically we will add a note to the ChangeLog and also set you as the author of the commit applying the patch and update the contributors section in the AUTHORS file. If the contributed feature is big or critical for whatever reason, it may also be mentioned in release notes. Sadly, we sometimes see patches that are submitted and then the submitter never responds to our comments or requests for an updated patch. Depending on the nature of the patch, we may either fix the outstanding issues on our own and get another ISC engineer to review them or the ticket may end up in our Outstanding milestone. When a new release is started, we go through the tickets in Outstanding, select a small number of them and move them to whatever the current milestone is. Keep that in mind if you plan to submit a patch and forget about it. We may accept it eventually, but it's much, much faster process if you participate in it. ## Extra steps If you are interested in knowing the results of more in-depth testing, you are welcome to visit the ISC Jenkins page: https://jenkins.isc.org This is a live result page with all tests being run on various systems. Besides basic unit-tests, we also have reports from valgrind (memory debugger), cppcheck and clang-analyzer (static code analyzers), Lettuce system tests and more. Although it is not possible for non ISC employees to run tests on that farm, it is possible that your contributed patch will end up there sooner or later. We also have ISC Forge tests running and other additional tests, but currently those test results are not publicly available.