Compilation Configuration Process

Organization

The gated building process allows the compilation of gated for different architectures using the same source tree. Each different system can use a subdirectory of the src directory to compile the source files into architecture dependent object files.

Moreover the list of files to be compiled, and their content are dependent on the list of protocols the user chooses to configure in his Config file.

The 'make config' process is in charge of configuring the object directory with the set of files needed for a certain configuration, as well as creating certain files used during the building process.

The make config process

The 'make config' process creates the following files:

• obj/defines.h contains a list of #define clauses to be included in all the C source code. The value of those #define are generated from the options statements in the Config file as well as from the protocol statements.
• obj/paths.h contains a list of paths for different files gated uses, like the config file, dump file, etc... It is generated from src/paths.h by substitution (C.f. section 7.2.4).
• obj/version.c contains a list of version numbers for each source file as well as for the gated release. The version numbers are embedded in C string constants to be hardcoded in the gated binary.
• obj/parser.y is the real yacc source file to generate the parser for gated for the selected protocols. It is generated from src/parser.y by substitution (C.f. section 7.2.4).
• obj/signames.c is the C declaration of the sys_signame[] variable if the system does not support it. signames.c is generated from <signal.h> only if the NEED_SIGNAME option is defined in the Config file.
• obj/Makefile is the make rule file used to build gated. It is generated from util/Makefile.temp by substitution (C.f. section 7.2.4) and contains only the rules for the configured source files.
• obj/*.c obj/*.h obj/*.y obj/*.l A set of symbolic link to the source files in src/.

The files needed for this configuration process are:

• util/configure.pl is a perl script doing the configuration.
• util/Makefile.templ is a template for the Makefile.
• util/files is the list of files to compile. The list is sorted by protocols.
• parser.y is the full yacc source file with support for all protocols.
• *.c *.h are all the source files in the scr/ directory.

To summarize, when executing make config the util/configure.pl script is first run. This script will:

• find out about the current directory and the object directory used for that system,
• generate all the files previously listed in the object directory.

• clean up the object directory,
• create parser.c and parser.h by running yacc or bison on parser.y.
• create the symbolic links,
• compute the file dependencies by running the mkdep command.

Make's targets list

The object directory Makefile defines the following targets for any program to be built. Other can be added on a case by case rule.

• all:: Default target when executing make.
• lint:: Used when checking the code with lint(1).
• install:: Used to install the software's executable.
• install-man:: Used to install the software's manual pages and documentation
• clean:: Used to clean up the directory.
• cleanall:: A better clean than clean::. clean:: removes only object files. cleanall:: removes any file which can be generated from the original distribution.

File filtering

Some files in the distribution package are run through a filter to obtain a version which only supports of the user configured protocols. For example if only rip and bgp are needed then the resulting file will only contain the code for RIP and BGP, which makes the final binary smaller. The general syntax for filtering in or out some part of the code is similar to the C processor. The syntax is:

@BEGIN [NOT] SYMBOL [| SYMBOL2...] text... @END

The text in between @BEGIN and @END will be kept if the symbol SYMBOL (or SYMBOL2...) is defined. Those symbols are any variable, protocol or option defined in the Config file. They include program names ( cc, lex...), directory or file names ( path_config, mandir, ...), options ( NEED_STRERROR, POSIX_SIGNALS, ...) and protocols ( bgp, rip, ...). For the later the symbol to add after @BEGIN is PROTO_BGP for bgp, PROTO_RIP for rip, etc... (See the %proto definition in util/configure.pl for the equivalence between protocol names and symbols).

Also some generic names (as the dump file name, configuration file name, etc...) are replaced by their real value chosen by the user. If the source file contains the tokens @(symbol) then this token will be replaced by the value of symbol defined in the Config file. For instance, if the Config file contains

path_config /etc/\%s.conf

and the file paths.h contains

#define _PATH_CONFIG "@(_path_config)"

then the resulting file will be

#define _PATH_CONFIG "/etc/\%s.config"

[ Note: trailing '_' are ignored and substitution is case insensitive.]

Adding a new protocol

The following are recommendation to install a new protocol into gated:

• Define a name for the protocol to be used in the Config file, and add this name to the %proto definition in util/configure.pl. Also, if any new option is needed in the Config file add the default value to the %options table. You also may want to look at the %dirPath (directories and files used to configure the Makefile), runtimePath (directories and files to be hardcoded in paths.h), %miscParam (some more parameters for the Makefile), %unixCmd (Unix commands for the Makefile), %cmdFlags (flags for the Unix commands).
• Add all the new source files (C, yacc, etc... code) into the util/files file using the syntax defined in section 7.2.4.
• Modify util/Makefile.temp to add any new target.
• Update parser.y to add support for the new protocol configuration into the gated parser. Conditional compilation can be done by using the syntax defined in section 7.2.4.