HACKING - quagga - Gitiles

 -*- mode: text; -*-
 $QuaggaId: Format:%an, %ai, %h$ $

 Contents:

 * GUIDELINES FOR HACKING ON QUAGGA
 * COMPILE-TIME CONDITIONAL CODE
 * COMMIT MESSAGE
 * HACKING THE BUILD SYSTEM
 * RELEASE PROCEDURE
 * SHARED LIBRARY VERSIONING
 * RELEASE PROCEDURE
 * TOOL VERSIONS
 * SHARED LIBRARY VERSIONING
 * PATCH SUBMISSION
 * PATCH APPLICATION
 * STABLE PLATFORMS AND DAEMONS
 * IMPORT OR UPDATE VENDOR SPECIFIC ROUTING PROTOCOLS

 GUIDELINES FOR HACKING ON QUAGGA

 [this is a draft in progress]

 GNU coding standards apply.  Indentation follows the result of
 invoking GNU indent (as of 2.2.8a) with no arguments.  Note that this
 uses tabs instead of spaces where possible for leading whitespace, and
 assumes that tabs are every 8 columns.  Do not attempt to redefine the
 location of tab stops.  Note also that some indentation does not
 follow GNU style.  This is a historical accident, and we generally
 only clean up whitespace when code is unmaintainable due to whitespace
 issues, as fewer changes from zebra lead to easier merges.

 For GNU emacs, use indentation style "gnu".

 For Vim, use the following lines (note that tabs are at 8, and that
 softtabstop sets the indentation level):

 set tabstop=8
 set softtabstop=2
 set shiftwidth=2
 set noexpandtab

 Be particularly careful not to break platforms/protocols that you
 cannot test.

 New code should have good comments, and changes to existing code
 should in many cases upgrade the comments when necessary for a
 reviewer to conclude that the change has no unintended consequences.

 Each file in the Git repository should have a git format-placeholder (like
 an RCS Id keyword), somewhere very near the top, commented out appropriately
 for the file type. The placeholder used for Quagga (replacing <dollar> with
 $) is:

 	$QuaggaId: <dollar>Format:%an, %ai, %h<dollar> $

 See line 2 of HACKING for an example;

 This placeholder string will be expanded out by the 'git archive' commands,
 wihch is used to generate the tar archives for snapshots and releases.

 Please document fully the proper use of a new function in the header file
 in which it is declared.  And please consult existing headers for
 documentation on how to use existing functions.  In particular, please consult
 these header files:

   lib/log.h	logging levels and usage guidance
   [more to be added]

 If changing an exported interface, please try to deprecate the interface in
 an orderly manner. If at all possible, try to retain the old deprecated
 interface as is, or functionally equivalent. Make a note of when the
 interface was deprecated and guard the deprecated interface definitions in
 the header file, ie:

 /* Deprecated: 20050406 */
 #if !defined(QUAGGA_NO_DEPRECATED_INTERFACES)
 #warning "Using deprecated <libname> (interface(s)|function(s))"
 ...
 #endif /* QUAGGA_NO_DEPRECATED_INTERFACES */

 To ensure that the core Quagga sources do not use the deprecated interfaces
 (you should update Quagga sources to use new interfaces, if applicable)
 while allowing external sources to continue to build. Deprecated interfaces
 should be excised in the next unstable cycle.

 Note: If you wish, you can test for GCC and use a function
 marked with the 'deprecated' attribute. However, you must provide the
 #warning for other compilers.

 If changing or removing a command definition, *ensure* that you properly
 deprecate it - use the _DEPRECATED form of the appropriate DEFUN macro. This
 is *critical*. Even if the command can no longer function, you *must* still
 implement it as a do-nothing stub. Failure to follow this causes grief for
 systems administrators. Deprecated commands should be excised in the next
 unstable cycle. A list of deprecated commands should be collated for each
 release.

 See also below regarding SHARED LIBRARY VERSIONING.

 COMPILE-TIME CONDITIONAL CODE

 Please think very carefully before making code conditional at compile time,
 as it increases maintenance burdens and user confusion. In particular,
 please avoid gratuitious --enable-.... switches to the configure script -
 typically code should be good enough to be in Quagga, or it shouldn't be
 there at all.

 When code must be compile-time conditional, try have the compiler make it
 conditional rather than the C pre-processor. I.e. this:

     if (SOME_SYMBOL)
       frobnicate();

 rather than:

   #ifdef SOME_SYMBOL
   frobnicate ();
   #endif /* SOME_SYMBOL */

 Note that the former approach requires ensuring that SOME_SYMBOL will be
 defined (watch your AC_DEFINEs).

 COMMIT MESSAGES

 The commit message should provide:

 * A suitable one-line summary as the very first line of the message, in the
   form:

   topic: high-level, one line summary

   Where topic would tend to be name of a subdirectory, and/or daemon, unless
   there's a more suitable topic (e.g. 'build').  This topic is used to
   organise change summaries in release announcements.

 * An optional introduction, discussing the general intent of the change.
 * A short description of each change made, preferably:
   * file by file
     * function by function (use of "ditto", or globs is allowed)

 to provide a short description of the general intent of the patch, in terms
 of the problem it solves and how it achieves it, to help reviewers
 understand.


 The reason for such itemised commit messages is to encourage the author to
 self-review every line of the patch, as well as provide reviewers an index
 of which changes are intended, along with a short description for each.
 Some discretion is obviously required.  A C-to-english description is not
 desireable.  For short patches, a per-function/file break-down may be
 redundant.  For longer patches, such a break-down may be essential.

 An example (where the general discussion is obviously somewhat redundant,
 given the one-line summary):

 zebra: Enhance frob FSM to detect loss of frob

 * (general) Add a new DOWN state to the frob state machine
    to allow the barinator to detect loss of frob.
 * frob.h: (struct frob) Add DOWN state flag.
 * frob.c: (frob_change) set/clear DOWN appropriately on state change.
 * bar.c: (barinate) Check frob for DOWN state.


 HACKING THE BUILD SYSTEM

 If you change or add to the build system (configure.ac, any Makefile.am,
 etc.), try to check that the following things still work:

 	- make dist
 	- resulting dist tarball builds
 	- out-of-tree builds

 The quagga.net site relies on make dist to work to generate snapshots. It
 must work. Common problems are to forget to have some additional file
 included in the dist, or to have a make rule refer to a source file without
 using the srcdir variable.

 RELEASE PROCEDURE

 * Tag the apppropriate commit with a release tag (follow existing
   conventions).
   [This enables recreating the release, and is just good CM practice.]

 * Create a fresh tar archive of the quagga.net repository, and do a test
   build:

     git-clone git:///code.quagga.net/quagga.git quagga
     git-archive --remote=git://code.quagga.net/quagga.git \
         --prefix=quagga-release/ master | tar -xf -
     cd quagga-release

     autoreconf -i
     ./configure
     make
     make dist

 The tarball which 'make dist' creates is the tarball to be released! The
 git-archive step ensures you're working with code corresponding to that in
 the official repository, and also carries out keyword expansion. If any
 errors occur, move tags as needed and start over from the fresh checkouts.
 Do not append to tarballs, as this has produced non-standards-conforming
 tarballs in the past.

 See also: http://wiki.quagga.net/index.php/Main/Processes

 [TODO: collation of a list of deprecated commands. Possibly can be scripted
 to extract from vtysh/vtysh_cmd.c]


 TOOL VERSIONS

 Require versions of support tools are listed in INSTALL.quagga.txt.
 Required versions should only be done with due deliberation, as it can
 cause environments to no longer be able to compile quagga.


 SHARED LIBRARY VERSIONING

 [this section is at the moment just gdt's opinion]

 Quagga builds several shared libaries (lib/libzebra, ospfd/libospf,
 ospfclient/libsopfapiclient).  These may be used by external programs,
 e.g. a new routing protocol that works with the zebra daemon, or
 ospfapi clients.  The libtool info pages (node Versioning) explain
 when major and minor version numbers should be changed.  These values
 are set in Makefile.am near the definition of the library.  If you
 make a change that requires changing the shared library version,
 please update Makefile.am.

 libospf exports far more than it should, and is needed by ospfapi
 clients.  Only bump libospf for changes to functions for which it is
 reasonable for a user of ospfapi to call, and please err on the side
 of not bumping.

 There is no support intended for installing part of zebra.  The core
 library libzebra and the included daemons should always be built and
 installed together.


 PATCH SUBMISSION

 * Send a clean diff against the 'master' branch of the quagga.git
   repository, in unified diff format, preferably with the '-p' argument to
   show C function affected by any chunk, and with the -w and -b arguments to
   minimise changes. E.g:

     git diff -up mybranch..remotes/quagga.net/master

   Or by using git-format-patch.

 *  Not doing so is a definite hindrance to patch application.

 * Include NEWS entries as appropriate.

 * Please, please include an appropriate commit message with any emailed
   patches. Doing so makes it easier to review a patch, and apply it.

 * Include only one semantic change or group of changes per patch.

 * Do not make gratuitous changes to whitespace. See the w and b arguments
   to diff.

 * State on which platforms and with what daemons the patch has been
   tested.  Understand that if the set of testing locations is small,
   and the patch might have unforeseen or hard to fix consequences that
   there may be a call for testers on quagga-dev, and that the patch
   may be blocked until test results appear.

   If there are no users for a platform on quagga-dev who are able and
   willing to verify -current occasionally, that platform may be
   dropped from the "should be checked" list.


 PATCH APPLICATION

 * Only apply patches that meet the submission guidelines.

 * If the patch might break something, issue a call for testing on the
   mailinglist.

 * Give an appropriate commit message (see above), and use the --author
   argument to git-commit, if required, to ensure proper attribution (you
   should still be listed as committer)

 * Immediately after commiting, double-check (with git-log and/or gitk). If
   there's a small mistake you can easily fix it with 'git commit --amend ..'

 * By committing a patch, you are responsible for fixing problems
   resulting from it (or backing it out).


 STABLE PLATFORMS AND DAEMONS

 The list of platforms that should be tested follow.  This is a list
 derived from what quagga is thought to run on and for which
 maintainers can test or there are people on quagga-dev who are able
 and willing to verify that -current does or does not work correctly.

   BSD (Free, Net or Open, any platform) # without capabilities
   GNU/Linux (any distribution, i386)
   Solaris (strict alignment, any platform)
   [future: NetBSD/sparc64]

 The list of daemons that are thought to be stable and that should be
 tested are:

   zebra
   bgpd
   ripd
   ospfd
   ripngd

 Daemons which are in a testing phase are

   ospf6d
   isisd
   watchquagga


 IMPORT OR UPDATE VENDOR SPECIFIC ROUTING PROTOCOLS

 The source code of Quagga is based on two vendors:

    zebra_org (http://www.zebra.org/)
    isisd_sf (http://isisd.sf.net/)

 To import code from further sources, e.g. for archival purposes without
 necessarily having to review and/or fix some changeset, create a branch from
 'master':

 	git checkout -b archive/foo master
 	<apply changes>
 	git commit -a "Joe Bar <joe@example.com>"
 	git push quagga archive/foo

 presuming 'quagga' corresponds to a file in your .git/remotes with
 configuration for the appropriate Quagga.net repository.
	-- mode: text; --
	$QuaggaId: Format:%an, %ai, %h$ $

	Contents:

	* GUIDELINES FOR HACKING ON QUAGGA
	* COMPILE-TIME CONDITIONAL CODE
	* COMMIT MESSAGE
	* HACKING THE BUILD SYSTEM
	* RELEASE PROCEDURE
	* SHARED LIBRARY VERSIONING
	* RELEASE PROCEDURE
	* TOOL VERSIONS
	* SHARED LIBRARY VERSIONING
	* PATCH SUBMISSION
	* PATCH APPLICATION
	* STABLE PLATFORMS AND DAEMONS
	* IMPORT OR UPDATE VENDOR SPECIFIC ROUTING PROTOCOLS

	GUIDELINES FOR HACKING ON QUAGGA

	[this is a draft in progress]

	GNU coding standards apply. Indentation follows the result of
	invoking GNU indent (as of 2.2.8a) with no arguments. Note that this
	uses tabs instead of spaces where possible for leading whitespace, and
	assumes that tabs are every 8 columns. Do not attempt to redefine the
	location of tab stops. Note also that some indentation does not
	follow GNU style. This is a historical accident, and we generally
	only clean up whitespace when code is unmaintainable due to whitespace
	issues, as fewer changes from zebra lead to easier merges.

	For GNU emacs, use indentation style "gnu".

	For Vim, use the following lines (note that tabs are at 8, and that
	softtabstop sets the indentation level):

	set tabstop=8
	set softtabstop=2
	set shiftwidth=2
	set noexpandtab

	Be particularly careful not to break platforms/protocols that you
	cannot test.

	New code should have good comments, and changes to existing code
	should in many cases upgrade the comments when necessary for a
	reviewer to conclude that the change has no unintended consequences.

	Each file in the Git repository should have a git format-placeholder (like
	an RCS Id keyword), somewhere very near the top, commented out appropriately
	for the file type. The placeholder used for Quagga (replacing <dollar> with
	$) is:

	$QuaggaId: <dollar>Format:%an, %ai, %h<dollar> $

	See line 2 of HACKING for an example;

	This placeholder string will be expanded out by the 'git archive' commands,
	wihch is used to generate the tar archives for snapshots and releases.

	Please document fully the proper use of a new function in the header file
	in which it is declared. And please consult existing headers for
	documentation on how to use existing functions. In particular, please consult
	these header files:

	lib/log.h logging levels and usage guidance
	[more to be added]

	If changing an exported interface, please try to deprecate the interface in
	an orderly manner. If at all possible, try to retain the old deprecated
	interface as is, or functionally equivalent. Make a note of when the
	interface was deprecated and guard the deprecated interface definitions in
	the header file, ie:

	/* Deprecated: 20050406 */
	#if !defined(QUAGGA_NO_DEPRECATED_INTERFACES)
	#warning "Using deprecated <libname> (interface(s)\|function(s))"
	...
	#endif /* QUAGGA_NO_DEPRECATED_INTERFACES */

	To ensure that the core Quagga sources do not use the deprecated interfaces
	(you should update Quagga sources to use new interfaces, if applicable)
	while allowing external sources to continue to build. Deprecated interfaces
	should be excised in the next unstable cycle.

	Note: If you wish, you can test for GCC and use a function
	marked with the 'deprecated' attribute. However, you must provide the
	#warning for other compilers.

	If changing or removing a command definition, ensure that you properly
	deprecate it - use the _DEPRECATED form of the appropriate DEFUN macro. This
	is critical. Even if the command can no longer function, you must still
	implement it as a do-nothing stub. Failure to follow this causes grief for
	systems administrators. Deprecated commands should be excised in the next
	unstable cycle. A list of deprecated commands should be collated for each
	release.

	See also below regarding SHARED LIBRARY VERSIONING.

	COMPILE-TIME CONDITIONAL CODE

	Please think very carefully before making code conditional at compile time,
	as it increases maintenance burdens and user confusion. In particular,
	please avoid gratuitious --enable-.... switches to the configure script -
	typically code should be good enough to be in Quagga, or it shouldn't be
	there at all.

	When code must be compile-time conditional, try have the compiler make it
	conditional rather than the C pre-processor. I.e. this:

	if (SOME_SYMBOL)
	frobnicate();

	rather than:

	#ifdef SOME_SYMBOL
	frobnicate ();
	#endif /* SOME_SYMBOL */

	Note that the former approach requires ensuring that SOME_SYMBOL will be
	defined (watch your AC_DEFINEs).

	COMMIT MESSAGES

	The commit message should provide:

	* A suitable one-line summary as the very first line of the message, in the
	form:

	topic: high-level, one line summary

	Where topic would tend to be name of a subdirectory, and/or daemon, unless
	there's a more suitable topic (e.g. 'build'). This topic is used to
	organise change summaries in release announcements.

	* An optional introduction, discussing the general intent of the change.
	* A short description of each change made, preferably:
	* file by file
	* function by function (use of "ditto", or globs is allowed)

	to provide a short description of the general intent of the patch, in terms
	of the problem it solves and how it achieves it, to help reviewers
	understand.


	The reason for such itemised commit messages is to encourage the author to
	self-review every line of the patch, as well as provide reviewers an index
	of which changes are intended, along with a short description for each.
	Some discretion is obviously required. A C-to-english description is not
	desireable. For short patches, a per-function/file break-down may be
	redundant. For longer patches, such a break-down may be essential.

	An example (where the general discussion is obviously somewhat redundant,
	given the one-line summary):

	zebra: Enhance frob FSM to detect loss of frob

	* (general) Add a new DOWN state to the frob state machine
	to allow the barinator to detect loss of frob.
	* frob.h: (struct frob) Add DOWN state flag.
	* frob.c: (frob_change) set/clear DOWN appropriately on state change.
	* bar.c: (barinate) Check frob for DOWN state.


	HACKING THE BUILD SYSTEM

	If you change or add to the build system (configure.ac, any Makefile.am,
	etc.), try to check that the following things still work:

	- make dist
	- resulting dist tarball builds
	- out-of-tree builds

	The quagga.net site relies on make dist to work to generate snapshots. It
	must work. Common problems are to forget to have some additional file
	included in the dist, or to have a make rule refer to a source file without
	using the srcdir variable.

	RELEASE PROCEDURE

	* Tag the apppropriate commit with a release tag (follow existing
	conventions).
	[This enables recreating the release, and is just good CM practice.]

	* Create a fresh tar archive of the quagga.net repository, and do a test
	build:

	git-clone git:///code.quagga.net/quagga.git quagga
	git-archive --remote=git://code.quagga.net/quagga.git \
	--prefix=quagga-release/ master \| tar -xf -
	cd quagga-release

	autoreconf -i
	./configure
	make
	make dist

	The tarball which 'make dist' creates is the tarball to be released! The
	git-archive step ensures you're working with code corresponding to that in
	the official repository, and also carries out keyword expansion. If any
	errors occur, move tags as needed and start over from the fresh checkouts.
	Do not append to tarballs, as this has produced non-standards-conforming
	tarballs in the past.

	See also: http://wiki.quagga.net/index.php/Main/Processes

	[TODO: collation of a list of deprecated commands. Possibly can be scripted
	to extract from vtysh/vtysh_cmd.c]


	TOOL VERSIONS

	Require versions of support tools are listed in INSTALL.quagga.txt.
	Required versions should only be done with due deliberation, as it can
	cause environments to no longer be able to compile quagga.


	SHARED LIBRARY VERSIONING

	[this section is at the moment just gdt's opinion]

	Quagga builds several shared libaries (lib/libzebra, ospfd/libospf,
	ospfclient/libsopfapiclient). These may be used by external programs,
	e.g. a new routing protocol that works with the zebra daemon, or
	ospfapi clients. The libtool info pages (node Versioning) explain
	when major and minor version numbers should be changed. These values
	are set in Makefile.am near the definition of the library. If you
	make a change that requires changing the shared library version,
	please update Makefile.am.

	libospf exports far more than it should, and is needed by ospfapi
	clients. Only bump libospf for changes to functions for which it is
	reasonable for a user of ospfapi to call, and please err on the side
	of not bumping.

	There is no support intended for installing part of zebra. The core
	library libzebra and the included daemons should always be built and
	installed together.


	PATCH SUBMISSION

	* Send a clean diff against the 'master' branch of the quagga.git
	repository, in unified diff format, preferably with the '-p' argument to
	show C function affected by any chunk, and with the -w and -b arguments to
	minimise changes. E.g:

	git diff -up mybranch..remotes/quagga.net/master

	Or by using git-format-patch.

	* Not doing so is a definite hindrance to patch application.

	* Include NEWS entries as appropriate.

	* Please, please include an appropriate commit message with any emailed
	patches. Doing so makes it easier to review a patch, and apply it.

	* Include only one semantic change or group of changes per patch.

	* Do not make gratuitous changes to whitespace. See the w and b arguments
	to diff.

	* State on which platforms and with what daemons the patch has been
	tested. Understand that if the set of testing locations is small,
	and the patch might have unforeseen or hard to fix consequences that
	there may be a call for testers on quagga-dev, and that the patch
	may be blocked until test results appear.

	If there are no users for a platform on quagga-dev who are able and
	willing to verify -current occasionally, that platform may be
	dropped from the "should be checked" list.


	PATCH APPLICATION

	* Only apply patches that meet the submission guidelines.

	* If the patch might break something, issue a call for testing on the
	mailinglist.

	* Give an appropriate commit message (see above), and use the --author
	argument to git-commit, if required, to ensure proper attribution (you
	should still be listed as committer)

	* Immediately after commiting, double-check (with git-log and/or gitk). If
	there's a small mistake you can easily fix it with 'git commit --amend ..'

	* By committing a patch, you are responsible for fixing problems
	resulting from it (or backing it out).


	STABLE PLATFORMS AND DAEMONS

	The list of platforms that should be tested follow. This is a list
	derived from what quagga is thought to run on and for which
	maintainers can test or there are people on quagga-dev who are able
	and willing to verify that -current does or does not work correctly.

	BSD (Free, Net or Open, any platform) # without capabilities
	GNU/Linux (any distribution, i386)
	Solaris (strict alignment, any platform)
	[future: NetBSD/sparc64]

	The list of daemons that are thought to be stable and that should be
	tested are:

	zebra
	bgpd
	ripd
	ospfd
	ripngd

	Daemons which are in a testing phase are

	ospf6d
	isisd
	watchquagga


	IMPORT OR UPDATE VENDOR SPECIFIC ROUTING PROTOCOLS

	The source code of Quagga is based on two vendors:

	zebra_org (http://www.zebra.org/)
	isisd_sf (http://isisd.sf.net/)

	To import code from further sources, e.g. for archival purposes without
	necessarily having to review and/or fix some changeset, create a branch from
	'master':

	git checkout -b archive/foo master
	<apply changes>
	git commit -a "Joe Bar <joe@example.com>"
	git push quagga archive/foo

	presuming 'quagga' corresponds to a file in your .git/remotes with
	configuration for the appropriate Quagga.net repository.