X-Git-Url: https://granicus.if.org/sourcecode?a=blobdiff_plain;f=docs%2Fmanual%2Fdeveloper%2Fmodguide.html.en;h=91fffe1cb9b36846c8f4bf0a8c02935ff57f6865;hb=88445a671fe9d8c5f34a305cdd5eeb57a1cf7ee5;hp=80240dc5ea56100ef2945cfb6f2479af871d03ac;hpb=93ca524412929f08d0a4cba70e6e89a535e75fb4;p=apache diff --git a/docs/manual/developer/modguide.html.en b/docs/manual/developer/modguide.html.en index 80240dc5ea..91fffe1cb9 100644 --- a/docs/manual/developer/modguide.html.en +++ b/docs/manual/developer/modguide.html.en @@ -8,10 +8,13 @@
Apache HTTP Server Version 2.5
-This document will discuss how you can easily create modules for the Apache
-HTTP Server 2.4 ("Apache"), by exploring an example module called
+This document will discuss how you can create modules for the Apache
+HTTP Server 2.4, by exploring an example module called
mod_example
. In the first part of this document, the purpose
of this module will be to calculate and print out various digest values for
existing files on your web server, whenever we access the URL
@@ -48,24 +51,26 @@ MD5 digest value of the file located at
http://www.example.com/index.html
, we would visit
http://www.example.com/index.html.sum
.
In the second part of this document, which deals with configuration directive and context awareness, we will be looking at a module that simply write out its own configuration to the client.
+First and foremost, you are expected to have a basic knowledge of how the C programming language works. In most cases, we will try to be as pedagogical as possible and link to documents describing the functions used in the examples, but there are also many cases where it is necessary to either -just assume that "it works" or do some digging youself into what the hows +just assume that "it works" or do some digging yourself into what the hows and whys of various function calls.
Lastly, you will need to have a basic understanding of how modules are -loaded and configured in Apache, as well as how to get the headers for +loaded and configured in the Apache HTTP Server, as well as how to get the headers for Apache if you do not have them already, as these are needed for compiling new modules.
@@ -76,96 +81,109 @@ To compile the source code we are building in this document, we will be using APXS. Assuming your source file is called mod_example.c, compiling, installing and activating the module is as simple as: +apxs -i -a -c mod_example.c
Every module starts with the same declaration, or name tag if you will, -that defines a module as a separate entity within Apache: - - - -
-module AP_MODULE_DECLARE_DATA example_module=
-{
- STANDARD20_MODULE_STUFF,
- create_dir_conf,
/* Per-directory configuration handler */
- merge_dir_conf,
/* Merge handler for per-directory configurations */
- create_svr_conf,
/* Per-server configuration handler */
- merge_svr_conf,
/* Merge handler for per-server configurations */
- directives,
/* Any directives we may have for httpd */
- register_hooks/* Our hook registering function */
-}
;
++
+ + + +
+Every module starts with the same declaration, or name tag if you will, +that defines a module as a separate entity within Apache:+module AP_MODULE_DECLARE_DATA example_module = +{ + STANDARD20_MODULE_STUFF, + create_dir_conf, /* Per-directory configuration handler */ + merge_dir_conf, /* Merge handler for per-directory configurations */ + create_svr_conf, /* Per-server configuration handler */ + merge_svr_conf, /* Merge handler for per-server configurations */ + directives, /* Any directives we may have for httpd */ + register_hooks /* Our hook registering function */ +};-This bit of code lets Apache know that we have now registered a new module ++This bit of code lets the server know that we have now registered a new module in the system, and that its name is
example_module
. The name -of the module is used primarilly for two things:
+of the module is used primarily for two things:
+
For now, we're only concerned with the first purpose of the module name,
-which comes into play when we need to load the module:
-
LoadModule example_module modules/mod_example.so
mod_example.so
and look for a module
+which comes into play when we need to load the module:
+
++LoadModule example_module modules/mod_example.so ++ +
+In essence, this tells the server to open up mod_example.so
and look for a module
called example_module
.
Within this name tag of ours is also a bunch of references to how we would like to handle things: Which directives do we respond to in a configuration file or .htaccess, how do we operate within specific contexts, and what -handlers are we interested in registering with the Apache service. We'll +handlers are we interested in registering with the Apache HTTP service. We'll return to all these elements later in this document.
-When handling requests in Apache, the first thing you will need to do is
+When handling requests in Apache HTTP Server 2.4, the first thing you will need to do is
create a hook into the request handling process. A hook is essentially a
-message telling Apache that you are willing to either serve or at least
+message telling the server that you are willing to either serve or at least
take a glance at certain requests given by clients. All handlers, whether
it's mod_rewrite, mod_authn_*, mod_proxy and so on, are hooked into
specific parts of the request process. As you are probably aware, modules
serve different purposes; Some are authentication/authorization handlers,
others are file or script handlers while some third modules rewrite URIs or
-proxies content. Furthermore, in the end, it is up to the user of Apache
-how and when each module will come into place. Thus, Apache itself does not
+proxies content. Furthermore, in the end, it is up to the user of the server
+how and when each module will come into place. Thus, the server itself does not
presume to know which module is responsible for handling a specific
request, and will ask each module whether they have an interest in a given
request or not. It is then up to each module to either gently decline
serving a request, accept serving it or flat out deny the request from
being served, as authentication/authorization modules do:
-
+
To make it a bit easier for handlers such as our mod_example to know
-whether the client is requesting content we should handle or not, Apache
+whether the client is requesting content we should handle or not, the server
has directives for hinting to modules whether their assistance is needed or
not. Two of these are AddHandler
and SetHandler
. Let's take a look at
an example using AddHandler
. In
our example case, we want every request ending with .sum to be served by
mod_example
, so we'll add a configuration directive that tells
-Apache to do just that:
-
+the server to do just that: + +AddHandler example-handler .sum -
+What this tells the server is the following: Whenever we receive a request
for a URI ending in .sum, we are to let all modules know that we are
looking for whoever goes by the name of "example-handler" .
-Thus, when a request is being served that ends in .sum, Apache will let all
+Thus, when a request is being served that ends in .sum, the server will let all
modules know, that this request should be served by "example-handler
". As you will see later, when we start building mod_example, we will
check for this handler tag relayed by AddHandler
and reply to
-Apache based on the value of this tag.
+the server based on the value of this tag.
+module AP_MODULE_DECLARE_DATA example_module = { STANDARD20_MODULE_STUFF, --This lets Apache know that we are not interesting in anything fancy, we + +NULL
, -NULL
, -NULL
, -NULL
, -NULL
, -register_hooks
+ NULL, + NULL, + NULL, + NULL, + NULL, + register_hooks /* Our hook registering function */ };
/* Our hook registering function */
This lets the server know that we are not interesting in anything fancy, we just want to hook onto the requests and possibly handle some of them.
+The reference in our example declaration,
- -register_hooks
is the name of a function we will create to manage how we hook onto the request process. In this example module, the function has just one purpose; To create a simple hook that gets called after all the rewrites, access -control etc has been handled. Thus, we will let Apache know, that we want +control etc has been handled. Thus, we will let the server know, that we want to hook into its process as one of the last modules: +-static
void
register_hooks(
apr_pool_t*
pool)
-{
-/* Create a hook in the request handler, so we get called when a request arrives */
-ap_hook_handler
(
example_handler,
NULL
,
NULL
,
APR_HOOK_LAST)
;
-}
++static void register_hooks(apr_pool_t *pool) +{ + /* Create a hook in the request handler, so we get called when a request arrives */ + ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST); +}+The
@@ -221,122 +242,135 @@ the request. We will discuss how to create a handler in the next chapter.example_handler
reference is the function that will handle the request. We will discuss how to create a handler in the next chapter.Hooking into the request handling phase is but one of many hooks that you can create. Some other ways of hooking are: +
ap_hook_child_init
: Place a hook that executes when a child process is spawned (commonly used for initializing modules after Apache has forked)ap_hook_child_init
: Place a hook that executes when a child process is spawned (commonly used for initializing modules after the server has forked)ap_hook_pre_config
: Place a hook that executes before any configuration data has been read (very early hook)ap_hook_post_config
: Place a hook that executes after configuration has been parsed, but before Apache has forkedap_hook_post_config
: Place a hook that executes after configuration has been parsed, but before the server has forkedap_hook_translate_name
: Place a hook that executes when a URI needs to be translated into a filename on the server (think mod_rewrite
)ap_hook_quick_handler
: Similar to ap_hook_handler
, except it is run before any other request hooks (translation, auth, fixups etc)ap_hook_log_transaction
: Place a hook that executes when the server is about to add a log entry of the current requestA handler is essentially a function that receives a callback when a request -to Apache is made. It is passed a record of the current request (how it was +to the server is made. It is passed a record of the current request (how it was made, which headers and requests were passed along, who's giving the -request and so on), and is put in charge of either telling Apache that it's +request and so on), and is put in charge of either telling the server that it's not interested in the request or handle the request with the tools provided.
Let's start off by making a very simple request handler +that does the following: +
text/html
+In C code, our example handler will now look like this: +
--static
int
example_handler(
request_rec*
r)
-{
-/* First off, we need to check if this is a call for the "example-handler" handler.
-* If it is, we accept it and do our things, if not, we simply return DECLINED,
-* and Apache will try somewhere else.
-*/
-if
(
!
r-
>
handler
|
|
strcmp
(
r-
>
handler
,
"
example-handler
"
)
)
return
(
DECLINED)
;
++static int example_handler(request_rec *r) +{ + /* First off, we need to check if this is a call for the "example-handler" handler. + * If it is, we accept it and do our things, if not, we simply return DECLINED, + * and the server will try somewhere else. + */ + if (!r->handler || strcmp(r->handler, "example-handler")) return (DECLINED); -+/* Now that we are handling this request, we'll write out "Hello, world!" to the client.
-* To do so, we must first set the appropriate content type, followed by our output.
-*/
- ap_set_content_type(
r,
"
text/html
"
)
;
- ap_rprintf(
r,
"
Hello, world!
"
)
;
+ /* Now that we are handling this request, we'll write out "Hello, world!" to the client. + * To do so, we must first set the appropriate content type, followed by our output. + */ + ap_set_content_type(r, "text/html"); + ap_rprintf(r, "Hello, world!"); -/* Lastly, we must tell Apache that we took care of this request and everything went fine.
-* We do so by simply returning the value OK to Apache.
-*/
-return
OK;
-}
+ /* Lastly, we must tell the server that we took care of this request and everything went fine. + * We do so by simply returning the value OK to the server. + */ + return OK; +}Now, we put all we have learned together and end up with a program that looks like mod_example_1.c . The functions used in this example will be explained later in the section -"Some useful functions you should know" -.
The request_rec structure -
The most essential part of any request is the request record +"Some useful functions you should know". +
+ +The request_rec structure
+The most essential part of any request is the request record . In a call to a handler function, this is represented by the
request_req*
structure passed along with every call that is made. This struct, typically just refered to asr
in modules, contains all the information you need for your module to fully process any HTTP request and respond accordingly.Some key elements of the
request_req
structure are: +
r->handler
(char*)
: Contains the name of the handler Apache is currently asking to do the handling of this requestr->method
(char*)
: Contains the HTTP method being used, f.x. GET or POSTr->filename
(char*)
: Contains the translated filename the client is requestingr->args
(char*)
: Contains the query string of the request, if anyr->headers_in
(apr_table_t*)
: Contains all the headers sent by the clientr->connection
(conn_rec*)
: A record containing information about the current connectionr->useragent_ip
(char*)
: The IP address of the client connecting to usr->pool
(apr_pool_t*)
: The memory pool of this request. We'll discuss this in the "
-Memory management" chapter.r->handler (char*):
Contains the name of the handler the server is currently asking to do the handling of this requestr->method (char*):
Contains the HTTP method being used, f.x. GET or POSTr->filename (char*):
Contains the translated filename the client is requestingr->args (char*):
Contains the query string of the request, if anyr->headers_in (apr_table_t*):
Contains all the headers sent by the clientr->connection (conn_rec*):
A record containing information about the current connectionr->user (char*):
If the URI requires authentication, this is set to the username providedr->useragent_ip (char*):
The IP address of the client connecting to usr->pool (apr_pool_t*)
: The memory pool of this request. We'll discuss this in the
+"Memory management" chapter.
A complete list of all the values contained with in the request_req
structure can be found in
the httpd.h
header
file or at http://ci.apache.org/projects/httpd/trunk/doxygen/structrequest__rec.html.
Let's try out some of these variables in another example handler:
+
+static int example_handler(request_rec *r) +{ + /* Set the appropriate content type */ + ap_set_content_type(r, "text/html"); ---static
int
example_handler(
request_rec*
r)
-{
-/* Set the appropriate content type */
- ap_set_content_type(
r,
"
text/html
"
)
;
- -/* Print out the IP address of the client connecting to us: */
- ap_rprintf(
r,
"
<h2>Hello,
%s
!</h2>
"
,
r-
>
useragent_ip
)
;
+ /* Print out the IP address of the client connecting to us: */ + ap_rprintf(r, "<h2>Hello, %s!</h2>", r->useragent_ip); -/* If we were reached through a GET or a POST request, be happy, else sad. */
-if
(
!
strcmp
(
r-
>
method
,
"
POST
"
)
|
|
!
strcmp
(
r-
>
method
,
"
GET
"
)
)
{
- ap_rputs(
"
You used a GET or a POST method, that makes us happy!<br>
"
,
r)
;
-}
-else
{
- ap_rputs(
"
You did not use POST or GET, that makes us sad :(<br>
"
,
r)
;
-}
- -/* Lastly, if there was a query string, let's print that too! */
-if
(
r-
>
args
)
{
- ap_rprintf(
r,
"
Your query string was:
%s
"
,
r-
>
args
)
;
-}
-return
OK;
-}
+ /* If we were reached through a GET or a POST request, be happy, else sad. */ + if ( !strcmp(r->method, "POST") || !strcmp(r->method, "GET") ) { + ap_rputs("You used a GET or a POST method, that makes us happy!<br/>", r); + } + else { + ap_rputs("You did not use POST or GET, that makes us sad :(<br/>", r); + } + + /* Lastly, if there was a query string, let's print that too! */ + if (r->args) { + ap_rprintf(r, "Your query string was: %s", r->args); + } + return OK; +}Return values
@@ -347,35 +381,39 @@ module is not interested in handling a specific request, it should always return the valueDECLINED
. If it is handling a request, it should either return the generic valueOK
, or a specific HTTP status code, for example: + - --static
int
example_handler(
request_rec*
r)
-{
-/* Return 404: Not found */
-return
HTTP_NOT_FOUND;
-}
++static int example_handler(request_rec *r) +{ + /* Return 404: Not found */ + return HTTP_NOT_FOUND; +}-ReturningOK
or a HTTP status code does not necessarilly mean -that the request will end. Apache may still have other handlers that are ++Returning
OK
or a HTTP status code does not necessarily mean +that the request will end. The server may still have other handlers that are interested in this request, for instance the logging modules which, upon a successful request, will write down a summary of what was requested and how it went. To do a full stop and prevent any further processing after your -module is done, you can return the valueDONE
to let Apache +module is done, you can return the valueDONE
to let the server know that it should cease all activity on this request and carry on with the next, without informing other handlers.
General response codes: +
DECLINED
: We are not handling this requestOK
: We handled this request and it went wellDONE
: We handled this request and Apache should just close this thread without further processingDONE
: We handled this request and the server should just close this thread without further processingHTTP specific return codes (excerpt): +
HTTP_OK (200)
: Request was okayHTTP_MOVED_PERMANENTLY (301)
: The resource has moved to a new URLHTTP_NOT_FOUND (404)
: File not foundHTTP_INTERNAL_SERVER_ERROR (500)
: Internal server error (self explanatory)ap_rputs+(
"
Hello, world!
"
,
r)
;
ap_rputs("Hello, world!", r);+ @@ -409,7 +447,8 @@ the next, without informing other handlers. -
+ap_rprintf
(
r,
"
Hello,
%s
!
"
,
r-
>
useragent_ip
)
;
ap_rprintf(r, "Hello, %s!", r->useragent_ip);+ @@ -420,7 +459,8 @@ the next, without informing other handlers. -
+ap_set_content_type
(
r,
"
text/plain
"
)
;
/* force a raw text output */
ap_set_content_type(r, "text/plain"); /* force a raw text output */+ @@ -431,7 +471,7 @@ the next, without informing other handlers.
-Managing your resources in Apache is quite easy, thanks to the memory pool +Managing your resources in Apache HTTP Server 2.4 is quite easy, thanks to the memory pool system. In essence, each server, connection and request have their own memory pool that gets cleaned up when its scope ends, e.g. when a request is done or when a server process shuts down. All your module needs to do is @@ -440,10 +480,11 @@ clean up after yourself - pretty neat, huh?
-In our module, we will primarilly be allocating memory for each request, so
-it's appropriate to use the r->pool
+In our module, we will primarily be allocating memory for each request, so
+it's appropriate to use the r->pool
reference when creating new objects. A few of the functions for allocating
memory within a pool are:
+
void* apr_palloc(
apr_pool_t *p, apr_size_t size)
: Allocates size
number of bytes in the pool for yousize
number of by
char* apr_pstrdup(
apr_pool_t *p, const char *s)
: Creates a duplicate of the string s
. This is useful for copying constant values so you can edit themchar* apr_psprintf(
-apr_pool_t *p, const char *fmt, ...)
: Similar to sprintf
, except Apache supplies you with an appropriately allocated target variablesprintf
, except the server supplies you with an appropriately allocated target variable
Let's put these functions into an example handler:
--static
int
example_handler(
request_rec*
r)
-{
-const
char
*
original=
"
You can't edit this!
"
;
-char
*
copy;
-int
*
integers;
+ ++static int example_handler(request_rec *r) +{ + const char* original = "You can't edit this!"; + char* copy; + int* integers; -+ +/* Allocate space for 10 integer values and set them all to zero. */
- integers=
apr_pcalloc(
r-
>
pool,
sizeof
(
int
)
*
10
)
;
+ /* Allocate space for 10 integer values and set them all to zero. */ + integers = apr_pcalloc(r->pool, sizeof(int)*10); -/* Create a copy of the 'original' variable that we can edit. */
- copy=
apr_pstrdup(
r-
>
pool,
original)
;
-return
OK;
-}
+ /* Create a copy of the 'original' variable that we can edit. */ + copy = apr_pstrdup(r->pool, original); + return OK; +}This is all well and good for our module, which won't need any pre-initialized variables or structures. However, if we wanted to initialize something early on, before the requests come rolling in, we could simply add a call to a function in our
-register_hooks
function to sort it out: +-static
void
register_hooks(
apr_pool_t*
pool)
-{
-/* Call a function that initializes some stuff */
-example_init_function
(
pool)
;
-/* Create a hook in the request handler, so we get called when a request arrives */
-ap_hook_handler
(
example_handler,
NULL
,
NULL
,
APR_HOOK_LAST)
;
-}
++static void register_hooks(apr_pool_t *pool) +{ + /* Call a function that initializes some stuff */ + example_init_function(pool); + /* Create a hook in the request handler, so we get called when a request arrives */ + ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST); +}+ +In this pre-request initialization function we would not be using the same pool as we did when allocating resources for request-based functions. -Instead, we would use the pool given to us by Apache for allocating memory +Instead, we would use the pool given to us by the server for allocating memory on a per-process based level. -
@@ -515,40 +560,45 @@ md5, we'll produce an MD5 digest, otherwise we'll produce a SHA1 digest.-Since the introduction of Apache 2.4, parsing request data from GET and +Since the introduction of Apache HTTP Server 2.4, parsing request data from GET and POST requests have never been easier. All we require to parse both GET and -POST data is four simple lines: +POST data is four simple lines: +
--apr_table_t *GET; -apr_array_header_t *POST; - -ap_args_to_table(r, &GET); -ap_parse_form_data(r,NULL
, &POST, -1, 8192); ++apr_table_t *GET; +apr_array_header_t*POST; + + + +ap_args_to_table(r, &GET); + +ap_parse_form_data(r, NULL, &POST, -1, 8192);+In our specific example module, we're looking for the
-digest
value from the query string, which now resides inside a table calledGET
. To extract this value, we need only perform a simple operation: -
- +-/* Get the "digest" key from the query string, if any. */
-const
char
*
digestType=
apr_table_get(
GET,
"
digest
"
)
;
-/* If no key was returned, we will set a default value instead. */
-if
(
!
digestType)
digestType=
"
sha1
"
;
++/* Get the "digest" key from the query string, if any. */ +const char *digestType = apr_table_get(GET, "digest"); +/* If no key was returned, we will set a default value instead. */ +if (!digestType) digestType = "sha1";+The structures used for the POST and GET data are not exactly the same, so if we were to fetch a value from POST data instead of the query string, we would have to resort to a few more lines, as outlined in this example in the last chapter of this document. @@ -556,130 +606,131 @@ would have to resort to a few more lines, as outlined in thi
+ + + +Making an advanced handler
+Now that we have learned how to parse form data and manage our resources, we can move on to creating an advanced version of our module, that spits -out the MD5 or SHA1 digest of files:
- - - --static
int
example_handler(
request_rec*
r)
-{
-int
rc,
exists;
- apr_finfo_t finfo;
- apr_file_t*
file;
-char
*
filename;
-char
buffer[
256
]
;
- apr_size_t readBytes;
-int
n;
- apr_table_t*
GET;
- apr_array_header_t*
POST;
-const
char
*
digestType;
+out the MD5 or SHA1 digest of files: ++static int example_handler(request_rec *r) +{ + int rc, exists; + apr_finfo_t finfo; + apr_file_t *file; + char *filename; + char buffer[256]; + apr_size_t readBytes; + int n; + apr_table_t *GET; + apr_array_header_t *POST; + const char *digestType; -+/* Check that the "example-handler" handler is being called. */
-if
(
!
r-
>
handler
|
|
strcmp
(
r-
>
handler
,
"
example-handler
"
)
)
return
(
DECLINED)
;
+ /* Check that the "example-handler" handler is being called. */ + if (!r->handler || strcmp(r->handler, "example-handler")) return (DECLINED); -/* Figure out which file is being requested by removing the .sum from it */
- filename=
apr_pstrdup(
r-
>
pool
,
r-
>
filename
)
;
- filename[
strlen
(
filename)
-
4
]
=
0
;
/* Cut off the last 4 characters. */
+ /* Figure out which file is being requested by removing the .sum from it */ + filename = apr_pstrdup(r->pool, r->filename); + filename[strlen(filename)-4] = 0; /* Cut off the last 4 characters. */ -/* Figure out if the file we request a sum on exists and isn't a directory */
- rc=
apr_stat(
&
finfo,
filename,
APR_FINFO_MIN,
r-
>
pool
)
;
-if
(
rc=
=
APR_SUCCESS)
{
- exists=
-(
-(
finfo.
filetype!
=
APR_NOFILE)
-&
&
!
(
finfo.
filetype&
APR_DIR)
-)
;
-if
(
!
exists)
return
HTTP_NOT_FOUND;
/* Return a 404 if not found. */
-}
-/* If apr_stat failed, we're probably not allowed to check this file. */
-else
return
HTTP_FORBIDDEN;
+ /* Figure out if the file we request a sum on exists and isn't a directory */ + rc = apr_stat(&finfo, filename, APR_FINFO_MIN, r->pool); + if (rc == APR_SUCCESS) { + exists = + ( + (finfo.filetype != APR_NOFILE) + && !(finfo.filetype & APR_DIR) + ); + if (!exists) return HTTP_NOT_FOUND; /* Return a 404 if not found. */ + } + /* If apr_stat failed, we're probably not allowed to check this file. */ + else return HTTP_FORBIDDEN; -/* Parse the GET and, optionally, the POST data sent to us */
+ /* Parse the GET and, optionally, the POST data sent to us */ - ap_args_to_table(
r,
&
GET)
;
- ap_parse_form_data(
r,
NULL
,
&
POST,
-
1
,
8192
)
;
+ ap_args_to_table(r, &GET); + ap_parse_form_data(r, NULL, &POST, -1, 8192); -/* Set the appropriate content type */
- ap_set_content_type(
r,
"
text/html
"
)
;
+ /* Set the appropriate content type */ + ap_set_content_type(r, "text/html"); -/* Print a title and some general information */
- ap_rprintf(
r,
"
<h2>Information on
%s
:</h2>
"
,
filename)
;
- ap_rprintf(
r,
"
<b>Size:</b>
%u
bytes<br/>
"
,
finfo.
size)
;
+ /* Print a title and some general information */ + ap_rprintf(r, "<h2>Information on %s:</h2>", filename); + ap_rprintf(r, "<b>Size:</b> %u bytes<br/>", finfo.size); -/* Get the digest type the client wants to see */
- digestType=
apr_table_get(
GET,
"
digest
"
)
;
-if
(
!
digestType)
digestType=
"
MD5
"
;
+ /* Get the digest type the client wants to see */ + digestType = apr_table_get(GET, "digest"); + if (!digestType) digestType = "MD5"; - rc=
apr_file_open(
&
file,
filename,
APR_READ,
APR_OS_DEFAULT,
r-
>
pool
)
;
-if
(
rc=
=
APR_SUCCESS)
{
+ rc = apr_file_open(&file, filename, APR_READ, APR_OS_DEFAULT, r->pool); + if (rc == APR_SUCCESS) { -/* Are we trying to calculate the MD5 or the SHA1 digest? */
-if
(
!
strcasecmp(
digestType,
"
md5
"
)
)
{
-/* Calculate the MD5 sum of the file */
-union
{
-char
chr[
16
]
;
- uint32_t num[
4
]
;
-}
digest;
- apr_md5_ctx_t md5;
- apr_md5_init(
&
md5)
;
- readBytes=
256
;
-while
(
apr_file_read(
file,
buffer,
&
readBytes)
=
=
APR_SUCCESS)
{
- apr_md5_update(
&
md5,
buffer,
readBytes)
;
-}
- apr_md5_final(
digest.
chr,
&
md5)
;
+ /* Are we trying to calculate the MD5 or the SHA1 digest? */ + if (!strcasecmp(digestType, "md5")) { + /* Calculate the MD5 sum of the file */ + union { + char chr[16]; + uint32_t num[4]; + } digest; + apr_md5_ctx_t md5; + apr_md5_init(&md5); + readBytes = 256; + while ( apr_file_read(file, buffer, &readBytes) == APR_SUCCESS ) { + apr_md5_update(&md5, buffer, readBytes); + } + apr_md5_final(digest.chr, &md5); -/* Print out the MD5 digest */
- ap_rputs(
"
<b>MD5: </b><code>
"
,
r)
;
-for
(
n=
0
;
n<
APR_MD5_DIGESTSIZE/
4
;
n+
+
)
{
- ap_rprintf(
r,
"
%08x
"
,
digest.
num[
n]
)
;
-}
- ap_rputs(
"
</code>
"
,
r)
;
-/* Print a link to the SHA1 version */
- ap_rputs(
"
<br/><a href='?digest=sha1'>View the SHA1 hash instead</a>
"
,
r)
;
-}
-else
{
-/* Calculate the SHA1 sum of the file */
-union
{
-char
chr[
20
]
;
- uint32_t num[
5
]
;
-}
digest;
- apr_sha1_ctx_t sha1;
- apr_sha1_init(
&
sha1)
;
- readBytes=
256
;
-while
(
apr_file_read(
file,
buffer,
&
readBytes)
=
=
APR_SUCCESS)
{
- apr_sha1_update(
&
sha1,
buffer,
readBytes)
;
-}
- apr_sha1_final(
digest.
chr,
&
sha1)
;
+ /* Print out the MD5 digest */ + ap_rputs("<b>MD5: </b><code>", r); + for (n = 0; n < APR_MD5_DIGESTSIZE/4; n++) { + ap_rprintf(r, "%08x", digest.num[n]); + } + ap_rputs("</code>", r); + /* Print a link to the SHA1 version */ + ap_rputs("<br/><a href='?digest=sha1'>View the SHA1 hash instead</a>", r); + } + else { + /* Calculate the SHA1 sum of the file */ + union { + char chr[20]; + uint32_t num[5]; + } digest; + apr_sha1_ctx_t sha1; + apr_sha1_init(&sha1); + readBytes = 256; + while ( apr_file_read(file, buffer, &readBytes) == APR_SUCCESS ) { + apr_sha1_update(&sha1, buffer, readBytes); + } + apr_sha1_final(digest.chr, &sha1); -/* Print out the SHA1 digest */
- ap_rputs(
"
<b>SHA1: </b><code>
"
,
r)
;
-for
(
n=
0
;
n<
APR_SHA1_DIGESTSIZE/
4
;
n+
+
)
{
- ap_rprintf(
r,
"
%08x
"
,
digest.
num[
n]
)
;
-}
- ap_rputs(
"
</code>
"
,
r)
;
+ /* Print out the SHA1 digest */ + ap_rputs("<b>SHA1: </b><code>", r); + for (n = 0; n < APR_SHA1_DIGESTSIZE/4; n++) { + ap_rprintf(r, "%08x", digest.num[n]); + } + ap_rputs("</code>", r); -/* Print a link to the MD5 version */
- ap_rputs(
"
<br/><a href='?digest=md5'>View the MD5 hash instead</a>
"
,
r)
;
-}
- apr_file_close(
file)
;
+ /* Print a link to the MD5 version */ + ap_rputs("<br/><a href='?digest=md5'>View the MD5 hash instead</a>", r); + } + apr_file_close(file); -}
- - - -/* Let Apache know that we responded to this request. */
-return
OK;
-}
+ } + /* Let the server know that we responded to this request. */ + return OK; +}This version in its entirity can be found here: mod_example_2.c. +
+If you are reading this, then you probably already know
what a configuration directive is. Simply put, a directive is a way of
telling an individual module (or a set of modules) how to behave, such as
these directives control how mod_rewrite
works:
-
+ +RewriteEngine On RewriteCond %{REQUEST_URI} ^/foo/bar RewriteRule ^/foo/bar/(.*)$ /foobar?page=$1 -
Each of these configuration directives are handled by a separate function, that parses the parameters given and sets up a configuration accordingly. +
To begin with, we'll create a basic configuration in C-space:
--typedef
struct
{
-int
enabled;
/* Enable or disable our module */
-const
char
*
path;
/* Some path to...something */
-int
typeOfAction;
/* 1 means action A, 2 means action B and so on */
-}
example_config;
++typedef struct { + int enabled; /* Enable or disable our module */ + const char *path; /* Some path to...something */ + int typeOfAction; /* 1 means action A, 2 means action B and so on */ +} example_config;+Now, let's put this into perspective by creating a very small module that just prints out a hard-coded configuration. You'll notice that we use the
+ +register_hooks
function for initializing the configuration values to their defaults: ++typedef struct { + int enabled; /* Enable or disable our module */ + const char *path; /* Some path to...something */ + int typeOfAction; /* 1 means action A, 2 means action B and so on */ +} example_config; +static example_config config; -+ +-+typedef
struct
{
-int
enabled;
/* Enable or disable our module */
-const
char
*
path;
/* Some path to...something */
-int
typeOfAction;
/* 1 means action A, 2 means action B and so on */
-}
example_config;
- -static
example_config config;
- -static
int
example_handler(
request_rec*
r)
-{
-if
(
!
r-
>
handler
|
|
strcmp
(
r-
>
handler
,
"
example-handler
"
)
)
return
(
DECLINED)
;
- ap_set_content_type(
r,
"
text/plain
"
)
;
- ap_rprintf(r,
"
Enabled:
%u
\n
"
,
config.
enabled)
;
- ap_rprintf(r,
"
Path:
%s
\n
"
,
config.
path)
;
- ap_rprintf(r,
"
TypeOfAction:
%x
\n
"
,
config.
typeOfAction)
;
-return
OK;
-}
- -static
void
register_hooks(
apr_pool_t*
pool)
-{
- config.
enabled=
1
;
- config.
path=
"
/foo/bar
"
;
- config.
typeOfAction=
0x00
;
- ap_hook_handler(
example_handler,
NULL
,
NULL
,
APR_HOOK_LAST)
;
-}
- -/* Define our module as an entity and assign a function for registering hooks */
- -module AP_MODULE_DECLARE_DATA example_module=
-{
- STANDARD20_MODULE_STUFF,
-NULL
,
/* Per-directory configuration handler */
-NULL
,
/* Merge handler for per-directory configurations */
-NULL
,
/* Per-server configuration handler */
-NULL
,
/* Merge handler for per-server configurations */
-NULL
,
/* Any directives we may have for httpd */
- register_hooks/* Our hook registering function */
-}
;
+static int example_handler(request_rec *r) +{ + if (!r->handler || strcmp(r->handler, "example-handler")) return(DECLINED); + ap_set_content_type(r, "text/plain"); + ap_rprintf(r, "Enabled: %u\n", config.enabled); + ap_rprintf(r, "Path: %s\n", config.path); + ap_rprintf(r, "TypeOfAction: %x\n", config.typeOfAction); + return OK; +} + +static void register_hooks(apr_pool_t *pool) +{ + config.enabled = 1; + config.path = "/foo/bar"; + config.typeOfAction = 0x00; + ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST); +} + +/* Define our module as an entity and assign a function for registering hooks */ + +module AP_MODULE_DECLARE_DATA example_module = +{ + STANDARD20_MODULE_STUFF, + NULL, /* Per-directory configuration handler */ + NULL, /* Merge handler for per-directory configurations */ + NULL, /* Per-server configuration handler */ + NULL, /* Merge handler for per-server configurations */ + NULL, /* Any directives we may have for httpd */ + register_hooks /* Our hook registering function */ +};So far so good. To access our new handler, we could add the following to our configuration: -
++ +<Location /example> SetHandler example-handler </Location> -When we visit, we'll see our current configuration being spit out by our module. +
-Registering directives with Apache
+Registering directives with the server
+What if we want to change our configuration, not by hard-coding new values into the module, but by using either the httpd.conf file or possibly a -.htaccess file? It's time to let Apache know that we want this to be +.htaccess file? It's time to let the server know that we want this to be possible. To do so, we must first change our name tag to include a -reference to the configuration directives we want to register with Apache: - +reference to the configuration directives we want to register with the server: +
-+module AP_MODULE_DECLARE_DATA example_module = { STANDARD20_MODULE_STUFF, --This will tell Apache that we are now accepting directives from the +NULL
,/* Per-directory configuration handler */
-NULL
,/* Merge handler for per-directory configurations */
-NULL
,/* Per-server configuration handler */
-NULL
,/* Merge handler for per-server configurations */
- example_directives,/* Any directives we may have for httpd */
- register_hooks/* Our hook registering function */
+ NULL, /* Per-directory configuration handler */ + NULL, /* Merge handler for per-directory configurations */ + NULL, /* Per-server configuration handler */ + NULL, /* Merge handler for per-server configurations */ + example_directives, /* Any directives we may have for httpd */ + register_hooks /* Our hook registering function */ };+This will tell the server that we are now accepting directives from the configuration files, and that the structure called
- -example_directives
holds information on what our directives are and how they work. Since we have three different variables in our module configuration, we will add a structure with three directives and a NULL at the end: ++static const command_rec example_directives[] = { --AP_INIT_TAKE1
("exampleEnabled", example_set_enabled,NULL
, RSRC_CONF, "Enable or disable mod_example"), -AP_INIT_TAKE1
("examplePath", example_set_path,NULL
, RSRC_CONF, "The path to whatever"), -AP_INIT_TAKE2
("exampleAction", example_set_action,NULL
, RSRC_CONF, "Special action value!"), - {NULL
} + AP_INIT_TAKE1("exampleEnabled", example_set_enabled, NULL, RSRC_CONF, "Enable or disable mod_example"), + AP_INIT_TAKE1("examplePath", example_set_path, NULL, RSRC_CONF, "The path to whatever"), + AP_INIT_TAKE2("exampleAction", example_set_action, NULL, RSRC_CONF, "Special action value!"), + { NULL } };
+
As you can see, each directive needs at least 5 parameters set: +-
+AP_INIT_TAKE1
: This is a macro that tells Apache that this directive takes one and only one argument. +AP_INIT_TAKE1
: This is a macro that tells the server that this directive takes one and only one argument. If we required two arguments, we could use the macroAP_INIT_TAKE2
and so on (refer to httpd_conf.h for more macros).exampleEnabled
: This is the name of our directive. More precisely, it is what the user must put in his/her configuration in order to invoke a configuration change in our module.- -
example_set_enabled
: This is a reference to a C function that parses the directive and sets the configuration accordingly. We will discuss how to make this in the following paragraph.- +
RSRC_CONF
: This tells Apache where the directive is permissable. We'll go into details on this value in the -later chapters, but for now,RSRC_CONF
means that Apache will only accept these directives in a server context.RSRC_CONF
: This tells the server where the directive is permitted. We'll go into details on this value in the +later chapters, but for now,RSRC_CONF
means that the server will only accept these directives in a server context."Enable or disable...."
: This is simply a brief description of what the directive does.(The "missing" parameter in our definition, which is usually set to
NULL
, is an optional function that can be run after the initial function to parse the arguments have been run. This is usually @@ -850,182 +917,185 @@ set them.)The directive handler function
-Now that we've told Apache to expect some directives for our module, it's -time to make a few functions for handling these. What Apache reads in the +Now that we've told the server to expect some directives for our module, it's +time to make a few functions for handling these. What the server reads in the configuration file(s) is text, and so naturally, what it passes along to our directive handler is one or more strings, that we ourselves need to recognize and act upon. You'll notice, that since we set our
exampleAction
directive to accept two arguments, its C function also -has an additional parameter defined:
- - --+ +/* Handler for the "exambleEnabled" directive */
-const
char
*
example_set_enabled(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
-{
-if
(
!
strcasecmp(
arg,
"
on
"
)
)
config.
enabled=
1
;
-else
config.
enabled=
0
;
-return
NULL
;
-}
- -/* Handler for the "examplePath" directive */
-const
char
*
example_set_path(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
-{
- config.
path=
arg;
-return
NULL
;
-}
- -/* Handler for the "exampleAction" directive */
-/* Let's pretend this one takes one argument (file or db), and a second (deny or allow), */
-/* and we store it in a bit-wise manner. */
-const
char
*
example_set_action(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg1,
const
char
*
arg2)
-{
-if
(
!
strcasecmp(
arg1,
"
file
"
)
)
config.
typeOfAction=
0x01
;
-else
config.
typeOfAction=
0x02
;
+has an additional parameter defined: + + ++/* Handler for the "exambleEnabled" directive */ +const char *example_set_enabled(cmd_parms *cmd, void *cfg, const char *arg) +{ + if(!strcasecmp(arg, "on")) config.enabled = 1; + else config.enabled = 0; + return NULL; +} + +/* Handler for the "examplePath" directive */ +const char *example_set_path(cmd_parms *cmd, void *cfg, const char *arg) +{ + config.path = arg; + return NULL; +} + +/* Handler for the "exampleAction" directive */ +/* Let's pretend this one takes one argument (file or db), and a second (deny or allow), */ +/* and we store it in a bit-wise manner. */ +const char *example_set_action(cmd_parms *cmd, void *cfg, const char *arg1, const char* arg2) +{ + if(!strcasecmp(arg1, "file")) config.typeOfAction = 0x01; + else config.typeOfAction = 0x02; -- +if
(
!
strcasecmp(
arg2,
"
deny
"
)
)
config.
typeOfAction+
=
0x10
;
-else
config.
typeOfAction+
=
0x20
;
-return
NULL
;
-}
+ if(!strcasecmp(arg2, "deny")) config.typeOfAction += 0x10; + else config.typeOfAction += 0x20; + return NULL; +}Putting it all together
Now that we have our directives set up, and handlers configured for them, we can assemble our module into one big file: +
++/* mod_example_config_simple.c: */ +#include <stdio.h> +#include "apr_hash.h" +#include "ap_config.h" +#include "ap_provider.h" +#include "httpd.h" +#include "http_core.h" +#include "http_config.h" +#include "http_log.h" +#include "http_protocol.h" +#include "http_request.h" + +/* + ============================================================================== + Our configuration prototype and declaration: + ============================================================================== + */ +typedef struct { + int enabled; /* Enable or disable our module */ + const char *path; /* Some path to...something */ + int typeOfAction; /* 1 means action A, 2 means action B and so on */ +} example_config; + +static example_config config; + +/* + ============================================================================== + Our directive handlers: + ============================================================================== + */ +/* Handler for the "exambleEnabled" directive */ +const char *example_set_enabled(cmd_parms *cmd, void *cfg, const char *arg) +{ + if(!strcasecmp(arg, "on")) config.enabled = 1; + else config.enabled = 0; + return NULL; +} -+ +-- +/* mod_example_config_simple.c: */
-#
include
<
stdio.h
>
-#
include
"
apr_hash.h
"
-#
include
"
ap_config.h
"
-#
include
"
ap_provider.h
"
-#
include
"
httpd.h
"
-#
include
"
http_core.h
"
-#
include
"
http_config.h
"
-#
include
"
http_log.h
"
-#
include
"
http_protocol.h
"
-#
include
"
http_request.h
"
- -/*
-==============================================================================
-Our configuration prototype and declaration:
-==============================================================================
-*/
-typedef
struct
{
-int
enabled;
/* Enable or disable our module */
-const
char
*
path;
/* Some path to...something */
-int
typeOfAction;
/* 1 means action A, 2 means action B and so on */
-}
example_config;
- -static
example_config config;
- -/*
-==============================================================================
-Our directive handlers:
-==============================================================================
-*/
-/* Handler for the "exambleEnabled" directive */
-const
char
*
example_set_enabled(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
-{
-if
(
!
strcasecmp(
arg,
"
on
"
)
)
config.
enabled=
1
;
-else
config.
enabled=
0
;
-return
NULL
;
-}
- -/* Handler for the "examplePath" directive */
-const
char
*
example_set_path(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
-{
- config.
path=
arg;
-return
NULL
;
-}
- -/* Handler for the "exampleAction" directive */
-/* Let's pretend this one takes one argument (file or db), and a second (deny or allow), */
-/* and we store it in a bit-wise manner. */
-const
char
*
example_set_action(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg1,
const
char
*
arg2)
-{
-if
(
!
strcasecmp(
arg1,
"
file
"
)
)
config.
typeOfAction=
0x01
;
-else
config.
typeOfAction=
0x02
;
+/* Handler for the "examplePath" directive */ +const char *example_set_path(cmd_parms *cmd, void *cfg, const char *arg) +{ + config.path = arg; + return NULL; +} + +/* Handler for the "exampleAction" directive */ +/* Let's pretend this one takes one argument (file or db), and a second (deny or allow), */ +/* and we store it in a bit-wise manner. */ +const char *example_set_action(cmd_parms *cmd, void *cfg, const char *arg1, const char* arg2) +{ + if(!strcasecmp(arg1, "file")) config.typeOfAction = 0x01; + else config.typeOfAction = 0x02; -if
(
!
strcasecmp(
arg2,
"
deny
"
)
)
config.
typeOfAction+
=
0x10
;
-else
config.
typeOfAction+
=
0x20
;
-return
NULL
;
-}
- -/*
-==============================================================================
-The directive structure for our name tag:
-==============================================================================
-*/
-static
const
command_rec example_directives[
]
=
-{
- AP_INIT_TAKE1(
"
exampleEnabled
"
,
example_set_enabled,
NULL
,
RSRC_CONF,
"
Enable or disable mod_example
"
)
,
- AP_INIT_TAKE1(
"
examplePath
"
,
example_set_path,
NULL
,
RSRC_CONF,
"
The path to whatever
"
)
,
- AP_INIT_TAKE2(
"
exampleAction
"
,
example_set_action,
NULL
,
RSRC_CONF,
"
Special action value!
"
)
,
-{
NULL
}
-}
;
-/*
-==============================================================================
-Our module handler:
-==============================================================================
-*/
-static
int
example_handler(
request_rec*
r)
-{
-if
(
!
r-
>
handler
|
|
strcmp
(
r-
>
handler
,
"
example-handler
"
)
)
return
(
DECLINED)
;
- ap_set_content_type(
r,
"
text/plain
"
)
;
- ap_rprintf(
r,
"
Enabled:
%u
\n
"
,
config.
enabled)
;
- ap_rprintf(
r,
"
Path:
%s
\n
"
,
config.
path)
;
- ap_rprintf(
r,
"
TypeOfAction:
%x
\n
"
,
config.
typeOfAction)
;
-return
OK;
-}
- -/*
-==============================================================================
-The hook registration function (also initializes the default config values):
-==============================================================================
-*/
-static
void
register_hooks(
apr_pool_t*
pool)
-{
- config.
enabled=
1
;
- config.
path=
"
/foo/bar
"
;
- config.
typeOfAction=
3
;
- ap_hook_handler(
example_handler,
NULL
,
NULL
,
APR_HOOK_LAST)
;
-}
-/*
-==============================================================================
-Our module name tag:
-==============================================================================
-*/
-module AP_MODULE_DECLARE_DATA example_module=
-{
- STANDARD20_MODULE_STUFF,
-NULL
,
/* Per-directory configuration handler */
-NULL
,
/* Merge handler for per-directory configurations */
-NULL
,
/* Per-server configuration handler */
-NULL
,
/* Merge handler for per-server configurations */
- example_directives,
/* Any directives we may have for httpd */
- register_hooks/* Our hook registering function */
-}
;
+ if(!strcasecmp(arg2, "deny")) config.typeOfAction += 0x10; + else config.typeOfAction += 0x20; + return NULL; +} + +/* + ============================================================================== + The directive structure for our name tag: + ============================================================================== + */ +static const command_rec example_directives[] = +{ + AP_INIT_TAKE1("exampleEnabled", example_set_enabled, NULL, RSRC_CONF, "Enable or disable mod_example"), + AP_INIT_TAKE1("examplePath", example_set_path, NULL, RSRC_CONF, "The path to whatever"), + AP_INIT_TAKE2("exampleAction", example_set_action, NULL, RSRC_CONF, "Special action value!"), + { NULL } +}; +/* + ============================================================================== + Our module handler: + ============================================================================== + */ +static int example_handler(request_rec *r) +{ + if(!r->handler || strcmp(r->handler, "example-handler")) return(DECLINED); + ap_set_content_type(r, "text/plain"); + ap_rprintf(r, "Enabled: %u\n", config.enabled); + ap_rprintf(r, "Path: %s\n", config.path); + ap_rprintf(r, "TypeOfAction: %x\n", config.typeOfAction); + return OK; +} + +/* + ============================================================================== + The hook registration function (also initializes the default config values): + ============================================================================== + */ +static void register_hooks(apr_pool_t *pool) +{ + config.enabled = 1; + config.path = "/foo/bar"; + config.typeOfAction = 3; + ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST); +} +/* + ============================================================================== + Our module name tag: + ============================================================================== + */ +module AP_MODULE_DECLARE_DATA example_module = +{ + STANDARD20_MODULE_STUFF, + NULL, /* Per-directory configuration handler */ + NULL, /* Merge handler for per-directory configurations */ + NULL, /* Per-server configuration handler */ + NULL, /* Merge handler for per-server configurations */ + example_directives, /* Any directives we may have for httpd */ + register_hooks /* Our hook registering function */ +};In our httpd.conf file, we can now change the hard-coded configuration by adding a few lines: -
++ +ExampleEnabled On ExamplePath "/usr/bin/foo" ExampleAction file allow -And thus we apply the configuration, visit
/example
on our web site, and we see the configuration has adapted to what we wrote in our configuration file. @@ -1038,11 +1108,12 @@ configuration file.Context aware configurations
Introduction to context aware configurations
-In Apache, different URLs, virtual hosts, directories etc can have very -different meanings to the user of Apache, and thus different contexts +In Apache HTTP Server 2.4, different URLs, virtual hosts, directories etc can have very +different meanings to the user of the server, and thus different contexts within which modules must operate. For example, let's assume you have this configuration set up for mod_rewrite: -
++ +<Directory "/var/www"> RewriteCond %{HTTP_HOST} ^example.com$ RewriteRule (.*) http://www.example.com/$1 @@ -1050,34 +1121,38 @@ configuration set up for mod_rewrite: <Directory "/var/www/sub"> RewriteRule ^foobar$ index.php?foobar=true </Directory> -In this example, you will have set up two different contexts for -mod_rewrite: +mod_rewrite:
-If mod_rewrite (or Apache for that matter) wasn't context aware, then +
- Inside
/var/www
, all requests forhttp://example.com
must go tohttp://www.example.com
- Inside
/var/www/sub
, all requests forfoobar
must go toindex.php?foobar=true
+If mod_rewrite (or the entire server for that matter) wasn't context aware, then these rewrite rules would just apply to every and any request made, regardless of where and how they were made, but since the module can pull -the context specific configuration straight from Apache, it does not need +the context specific configuration straight from the server, it does not need to know itself, which of the directives are valid in this context, since -Apache takes care of this.
+the server takes care of this.So how does a module get the specific configuration for the server, directory or location in question? It does so by making one simple call: +
- -+++example_config *config = (example_config*) ap_get_module_config(r->per_dir_config, &example_module); +-example_config *config = (example_config*) ap_get_module_config(r->per_dir_config
, &example_module); -That's it! Of course, a whole lot goes on behind the scenes, which we will -discuss in this chapter, starting with how Apache came to know what our +discuss in this chapter, starting with how the server came to know what our configuration looks like, and how it came to be set up as it is in the specific context.
@@ -1087,62 +1162,58 @@ specific context.In this chapter, we will be working with a slightly modified version of our previous context structure. We will set a
-context
variable that we can use to track which context configuration is being -used by Apache in various places: - - +used by the server in various places: +-typedef
struct
{
-char
context[
256
]
;
-char
path[
256
]
;
-int
typeOfAction;
-int
enabled;
-}
example_config;
++typedef struct { + char context[256]; + char path[256]; + int typeOfAction; + int enabled; +} example_config;- - -Our handler for requests will also be modified, yet still very simple: +
Our handler for requests will also be modified, yet still very simple:
--static
int
example_handler(
request_rec*
r)
-{
-if
(
!
r-
>
handler
|
|
strcmp
(
r-
>
handler
,
"
example-handler
"
)
)
return
(
DECLINED)
;
- example_config*
config=
(
example_config*
)
ap_get_module_config(
r-
>
per_dir_config
,
&
example_module)
;
- ap_set_content_type(
r,
"
text/plain
"
)
;
- ap_rprintf(
"
Enabled:
%u
\n
"
,
config-
>
enabled
)
;
- ap_rprintf(
"
Path:
%s
\n
"
,
config-
>
path
)
;
- ap_rprintf(
"
TypeOfAction:
%x
\n
"
,
config-
>
typeOfAction
)
;
- ap_rprintf(
"
Context:
%s
\n
"
,
config-
>
context
)
;
-return
OK;
-}
++static int example_handler(request_rec *r) +{ + if(!r->handler || strcmp(r->handler, "example-handler")) return(DECLINED); + example_config *config = (example_config*) ap_get_module_config(r->per_dir_config, &example_module); + ap_set_content_type(r, "text/plain"); + ap_rprintf("Enabled: %u\n", config->enabled); + ap_rprintf("Path: %s\n", config->path); + ap_rprintf("TypeOfAction: %x\n", config->typeOfAction); + ap_rprintf("Context: %s\n", config->context); + return OK; +}- -Choosing a context
Before we can start making our module context aware, we must first define, which contexts we will accept. As we saw in the previous chapter, defining -a directive required five elements be set: +a directive required five elements be set:
--AP_INIT_TAKE1
("exampleEnabled", example_set_enabled,NULL
, RSRC_CONF, "Enable or disable mod_example"), ++AP_INIT_TAKE1("exampleEnabled", example_set_enabled, NULL, RSRC_CONF, "Enable or disable mod_example"),-TheRSRC_CONF
definition told Apache that we would only allow + +The
-RSRC_CONF
definition told the server that we would only allow this directive in a global server context, but since we are now trying out a context aware version of our module, we should set this to something more lenient, namely the valueACCESS_CONF
, which lets us use @@ -1150,69 +1221,68 @@ the directive inside <Directory> and <Location> blocks.Using Apache to allocate configuration slots
-A much smarter way to manage your configurations is by letting Apache +
Using the server to allocate configuration slots
+A much smarter way to manage your configurations is by letting the server help you create them. To do so, we must first start off by changing our -name tag to let Apache know, that it should assist us in creating +name tag to let the server know, that it should assist us in creating and managing our configurations. Since we have chosen the per-directory (or per-location) context for our module configurations, we'll add a -per-directory creator and merger function reference in our tag: - - -
-module AP_MODULE_DECLARE_DATA example_module+per-directory creator and merger function reference in our tag: +=
-{
- STANDARD20_MODULE_STUFF,
- create_dir_conf,
/* Per-directory configuration handler */
- merge_dir_conf,
/* Merge handler for per-directory configurations */
-NULL
,
/* Per-server configuration handler */
-NULL
,
/* Merge handler for per-server configurations */
- directives,
/* Any directives we may have for httpd */
- register_hooks/* Our hook registering function */
-}
;
-+module AP_MODULE_DECLARE_DATA example_module = +{ + STANDARD20_MODULE_STUFF, + create_dir_conf, /* Per-directory configuration handler */ + merge_dir_conf, /* Merge handler for per-directory configurations */ + NULL, /* Per-server configuration handler */ + NULL, /* Merge handler for per-server configurations */ + directives, /* Any directives we may have for httpd */ + register_hooks /* Our hook registering function */ +}; +- -Creating new context configurations
+ +Creating new context configurations
-Now that we have told Apache to help us create and manage configurations, +Now that we have told the server to help us create and manage configurations, our first step is to make a function for creating new, blank configurations. We do so by creating the function we just referenced in -our name tag as the Per-directory configuration handler: - -
-+ +void
*
example_create_dir_conf(
apr_pool_t*
pool,
char
*
context)
{
- context=
context?
context:
"
(undefined context)
"
;
- example_config*
cfg=
apr_pcalloc(
pool,
sizeof
(
example_config)
)
;
-if
(
cfg)
{
-/* Set some default values */
-strcpy
(
cfg-
>
context
,
x)
;
- cfg-
>
enabled
=
0
;
- cfg-
>
path
=
"
/foo/bar
"
;
- cfg-
>
typeOfAction
=
0x11
;
-}
-return
dir;
-}
+our name tag as the Per-directory configuration handler: + ++void* example_create_dir_conf(apr_pool_t* pool, char* context) { + context = context ? context : "(undefined context)"; + example_config *cfg = apr_pcalloc(pool, sizeof(example_config)); + if(cfg) { + /* Set some default values */ + strcpy(cfg->context, x); + cfg->enabled = 0; + cfg->path = "/foo/bar"; + cfg->typeOfAction = 0x11; + } + return cfg; +}- -Merging configurations
+ +Merging configurations
Our next step in creating a context aware configuration is merging configurations. This part of the process particularly apply to scenarios where you have a parent configuration and a child, such as the following: -
++ +<Directory "/var/www"> ExampleEnable On ExamplePath /foo/bar @@ -1221,12 +1291,15 @@ where you have a parent configuration and a child, such as the following: <Directory "/var/www/subdir"> ExampleAction file deny </Directory> -In this example, it is natural to assume that the directory
/var/www/subdir
should inherit the value set for the/var/www
directory, as we did not specify aExampleEnable
nor -anExamplePath
for this directory. Apache does not presume to +anExamplePath
for this directory. The server does not presume to know if this is true, but cleverly does the following: ++
- Creates a new configuration for
/var/www
- Sets the configuration values according to the directives given for
@@ -1234,36 +1307,40 @@ know if this is true, but cleverly does the following:/var/www
- Sets the configuration values according to the directives given for
/var/www/subdir
- Proposes a merge of the two configurations into a new configuration for
/var/www/subdir
This proposal is handled by the
-merge_dir_conf
function we referenced in our name tag. The purpose of this function is to assess the -two configurations and decide how they are to be merged: +two configurations and decide how they are to be merged:-+ +void
*
merge_dir_conf(
apr_pool_t*
pool,
void
*
BASE,
void
*
ADD)
{
- example_config*
base=
BASE;
- example_config*
add=
ADD;
- example_config*
conf=
create_dir_conf(
pool,
"
Merged configuration
"
)
;
++void* merge_dir_conf(apr_pool_t* pool, void* BASE, void* ADD) { + example_config* base = (example_config *) BASE ; /* This is what was set in the parent context */ + example_config* add = (example_config *) ADD ; /* This is what is set in the new context */ + example_config* conf = (example_config *) create_dir_conf(pool, "Merged configuration"); /* This will be the merged configuration */ - conf- --
>
enabled
=
(
add-
>
enabled
=
=
0
)
?
base-
>
enabled
:
add-
>
enabled
;
- conf-
>
typeOfAction
=
add-
>
typeOfAction
?
add-
>
typeOfAction
:
base-
>
typeOfAction
;
-strcpy
(
conf-
>
path
,
strlen
(
add-
>
path
)
?
add-
>
path
:
base-
>
path
)
;
+ /* Merge configurations */ + conf->enabled = ( add->enabled == 0 ) ? base->enabled : add->enabled ; + conf->typeOfAction = add->typeOfAction ? add->typeOfAction : base->typeOfAction; + strcpy(conf->path, strlen(add->path) ? add->path : base->path); -return
conf;
-}
+ return conf ; +}Trying out our new context aware configurations
+ + +Trying out our new context aware configurations
Now, let's try putting it all together to create a new module that is context aware. First off, we'll create a configuration that lets us test how the module works: -
++ +<Location "/a"> SetHandler example-handler ExampleEnabled on @@ -1281,238 +1358,240 @@ how the module works: ExamplePath "/foo/bar/baz" ExampleEnabled on </Location> -Then we'll assemble our module code. Note, that since we are now using our name tag as reference when fetching configurations in our handler, I have added some prototypes to keep the compiler happy:
--/*$6
-+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-* mod_example_config.c
-+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-*/
- - -#
include
<
stdio.h
>
-#
include
"
apr_hash.h
"
-#
include
"
ap_config.h
"
-#
include
"
ap_provider.h
"
-#
include
"
httpd.h
"
-#
include
"
http_core.h
"
-#
include
"
http_config.h
"
-#
include
"
http_log.h
"
-#
include
"
http_protocol.h
"
-#
include
"
http_request.h
"
- -/*$1
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Configuration structure
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-*/
- -typedef
struct
-{
-char
context[
256
]
;
-char
path[
256
]
;
-int
typeOfAction;
-int
enabled;
-}
example_config;
- -/*$1
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Prototypes
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-*/
- -static
int
example_handler(
request_rec*
r)
;
-const
char
*
example_set_enabled(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
;
-const
char
*
example_set_path(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
;
-const
char
*
example_set_action(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg1,
const
char
*
arg2)
;
-void
*
create_dir_conf(
apr_pool_t*
pool,
char
*
context)
;
-void
*
merge_dir_conf(
apr_pool_t*
pool,
void
*
BASE,
void
*
ADD)
;
-static
void
register_hooks(
apr_pool_t*
pool)
;
- -/*$1
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Configuration directives
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-*/
- -static
const
command_rec directives[
]
=
-{
- AP_INIT_TAKE1(
"
exampleEnabled
"
,
example_set_enabled,
NULL
,
ACCESS_CONF,
"
Enable or disable mod_example
"
)
,
- AP_INIT_TAKE1(
"
examplePath
"
,
example_set_path,
NULL
,
ACCESS_CONF,
"
The path to whatever
"
)
,
- AP_INIT_TAKE2(
"
exampleAction
"
,
example_set_action,
NULL
,
ACCESS_CONF,
"
Special action value!
"
)
,
-{
NULL
}
-}
;
- -/*$1
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Our name tag
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-*/
- -module AP_MODULE_DECLARE_DATA example_module=
-{
- STANDARD20_MODULE_STUFF,
- create_dir_conf,
/* Per-directory configuration handler */
- merge_dir_conf,
/* Merge handler for per-directory configurations */
-NULL
,
/* Per-server configuration handler */
-NULL
,
/* Merge handler for per-server configurations */
- directives,
/* Any directives we may have for httpd */
- register_hooks/* Our hook registering function */
-}
;
- -/*
-=======================================================================================================================
-Hook registration function
-=======================================================================================================================
-*/
-static
void
register_hooks(
apr_pool_t*
pool)
-{
- ap_hook_handler(
example_handler,
NULL
,
NULL
,
APR_HOOK_LAST)
;
-}
- -/*
-=======================================================================================================================
-Our example web service handler
-=======================================================================================================================
-*/
-static
int
example_handler(
request_rec*
r)
-{
-if
(
!
r-
>
handler
|
|
strcmp
(
r-
>
handler
,
"
example-handler
"
)
)
return
(
DECLINED)
;
- -/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- example_config*
config=
(
example_config*
)
ap_get_module_config(
r-
>
per_dir_config
,
&
example_module)
;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- - ap_set_content_type(
r,
"
text/plain
"
)
;
- ap_rprintf(
r,
"
Enabled:
%u
\n
"
,
config-
>
enabled
)
;
- ap_rprintf(
r,
"
Path:
%s
\n
"
,
config-
>
path
)
;
- ap_rprintf(
r,
"
TypeOfAction:
%x
\n
"
,
config-
>
typeOfAction
)
;
- ap_rprintf(
r,
"
Context:
%s
\n
"
,
config-
>
context
)
;
-return
OK;
-}
- -/*
-=======================================================================================================================
-Handler for the "exambleEnabled" directive
-=======================================================================================================================
-*/
-const
char
*
example_set_enabled(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
-{
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- example_config*
conf=
(
example_config*
)
cfg;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- -if
(
conf)
-{
-if
(
!
strcasecmp(
arg,
"
on
"
)
)
- conf-
>
enabled
=
1
;
-else
- conf-
>
enabled
=
0
;
-}
- -return
NULL
;
-}
- -/*
-=======================================================================================================================
-Handler for the "examplePath" directive
-=======================================================================================================================
-*/
-const
char
*
example_set_path(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg)
-{
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- example_config*
conf=
(
example_config*
)
cfg;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- -if
(
conf)
-{
-strcpy
(
conf-
>
path
,
arg)
;
-}
- -return
NULL
;
-}
- -/*
-=======================================================================================================================
-Handler for the "exampleAction" directive ;
-Let's pretend this one takes one argument (file or db), and a second (deny or allow), ;
-and we store it in a bit-wise manner.
-=======================================================================================================================
-*/
-const
char
*
example_set_action(
cmd_parms*
cmd,
void
*
cfg,
const
char
*
arg1,
const
char
*
arg2)
-{
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- example_config*
conf=
(
example_config*
)
cfg;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- -if
(
conf)
-{
-{
-if
(
!
strcasecmp(
arg1,
"
file
"
)
)
- conf-
>
typeOfAction
=
0x01
;
-else
- conf-
>
typeOfAction
=
0x02
;
-if
(
!
strcasecmp(
arg2,
"
deny
"
)
)
- conf-
>
typeOfAction
+
=
0x10
;
-else
- conf-
>
typeOfAction
+
=
0x20
;
-}
-}
- -return
NULL
;
-}
- -/*
-=======================================================================================================================
-Function for creating new configurations for per-directory contexts
-=======================================================================================================================
-*/
-void
*
create_dir_conf(
apr_pool_t*
pool,
char
*
context)
-{
- context=
context?
context:
"
Newly created configuration
"
;
- -/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- example_config*
cfg=
apr_pcalloc(
pool,
sizeof
(
example_config)
)
;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- -if
(
cfg)
-{
-{
-/* Set some default values */
-strcpy
(
cfg-
>
context
,
context)
;
- cfg-
>
enabled
=
0
;
-memset
(
cfg-
>
path
,
0
,
256
)
;
- cfg-
>
typeOfAction
=
0x00
;
-}
-}
- -return
cfg;
-}
- -/*
-=======================================================================================================================
-Merging function for configurations
-=======================================================================================================================
-*/
-void
*
merge_dir_conf(
apr_pool_t*
pool,
void
*
BASE,
void
*
ADD)
-{
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- example_config*
base=
BASE;
- example_config*
add=
ADD;
- example_config*
conf=
create_dir_conf(
pool,
"
Merged configuration
"
)
;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- - conf-
>
enabled
=
(
add-
>
enabled
=
=
0
)
?
base-
>
enabled
:
add-
>
enabled
;
- conf-
>
typeOfAction
=
add-
>
typeOfAction
?
add-
>
typeOfAction
:
base-
>
typeOfAction
;
-strcpy
(
conf-
>
path
,
strlen
(
add-
>
path
)
?
add-
>
path
:
base-
>
path
)
;
-return
conf;
-}
++/*$6 + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + * mod_example_config.c + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + */ + + +#include <stdio.h> +#include "apr_hash.h" +#include "ap_config.h" +#include "ap_provider.h" +#include "httpd.h" +#include "http_core.h" +#include "http_config.h" +#include "http_log.h" +#include "http_protocol.h" +#include "http_request.h" + +/*$1 + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + Configuration structure + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + */ + +typedef struct +{ + char context[256]; + char path[256]; + int typeOfAction; + int enabled; +} example_config; + +/*$1 + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + Prototypes + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + */ + +static int example_handler(request_rec *r); +const char *example_set_enabled(cmd_parms *cmd, void *cfg, const char *arg); +const char *example_set_path(cmd_parms *cmd, void *cfg, const char *arg); +const char *example_set_action(cmd_parms *cmd, void *cfg, const char *arg1, const char *arg2); +void *create_dir_conf(apr_pool_t *pool, char *context); +void *merge_dir_conf(apr_pool_t *pool, void *BASE, void *ADD); +static void register_hooks(apr_pool_t *pool); + +/*$1 + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + Configuration directives + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + */ + +static const command_rec directives[] = +{ + AP_INIT_TAKE1("exampleEnabled", example_set_enabled, NULL, ACCESS_CONF, "Enable or disable mod_example"), + AP_INIT_TAKE1("examplePath", example_set_path, NULL, ACCESS_CONF, "The path to whatever"), + AP_INIT_TAKE2("exampleAction", example_set_action, NULL, ACCESS_CONF, "Special action value!"), + { NULL } +}; + +/*$1 + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + Our name tag + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + */ + +module AP_MODULE_DECLARE_DATA example_module = +{ + STANDARD20_MODULE_STUFF, + create_dir_conf, /* Per-directory configuration handler */ + merge_dir_conf, /* Merge handler for per-directory configurations */ + NULL, /* Per-server configuration handler */ + NULL, /* Merge handler for per-server configurations */ + directives, /* Any directives we may have for httpd */ + register_hooks /* Our hook registering function */ +}; + +/* + ======================================================================================================================= + Hook registration function + ======================================================================================================================= + */ +static void register_hooks(apr_pool_t *pool) +{ + ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST); +} + +/* + ======================================================================================================================= + Our example web service handler + ======================================================================================================================= + */ +static int example_handler(request_rec *r) +{ + if(!r->handler || strcmp(r->handler, "example-handler")) return(DECLINED); + + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + example_config *config = (example_config *) ap_get_module_config(r->per_dir_config, &example_module); + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + ap_set_content_type(r, "text/plain"); + ap_rprintf(r, "Enabled: %u\n", config->enabled); + ap_rprintf(r, "Path: %s\n", config->path); + ap_rprintf(r, "TypeOfAction: %x\n", config->typeOfAction); + ap_rprintf(r, "Context: %s\n", config->context); + return OK; +} + +/* + ======================================================================================================================= + Handler for the "exambleEnabled" directive + ======================================================================================================================= + */ +const char *example_set_enabled(cmd_parms *cmd, void *cfg, const char *arg) +{ + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + example_config *conf = (example_config *) cfg; + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + if(conf) + { + if(!strcasecmp(arg, "on")) + conf->enabled = 1; + else + conf->enabled = 0; + } + + return NULL; +} + +/* + ======================================================================================================================= + Handler for the "examplePath" directive + ======================================================================================================================= + */ +const char *example_set_path(cmd_parms *cmd, void *cfg, const char *arg) +{ + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + example_config *conf = (example_config *) cfg; + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + if(conf) + { + strcpy(conf->path, arg); + } + + return NULL; +} + +/* + ======================================================================================================================= + Handler for the "exampleAction" directive ; + Let's pretend this one takes one argument (file or db), and a second (deny or allow), ; + and we store it in a bit-wise manner. + ======================================================================================================================= + */ +const char *example_set_action(cmd_parms *cmd, void *cfg, const char *arg1, const char *arg2) +{ + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + example_config *conf = (example_config *) cfg; + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + if(conf) + { + { + if(!strcasecmp(arg1, "file")) + conf->typeOfAction = 0x01; + else + conf->typeOfAction = 0x02; + if(!strcasecmp(arg2, "deny")) + conf->typeOfAction += 0x10; + else + conf->typeOfAction += 0x20; + } + } + + return NULL; +} + +/* + ======================================================================================================================= + Function for creating new configurations for per-directory contexts + ======================================================================================================================= + */ +void *create_dir_conf(apr_pool_t *pool, char *context) +{ + context = context ? context : "Newly created configuration"; + + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + example_config *cfg = apr_pcalloc(pool, sizeof(example_config)); + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + if(cfg) + { + { + /* Set some default values */ + strcpy(cfg->context, context); + cfg->enabled = 0; + memset(cfg->path, 0, 256); + cfg->typeOfAction = 0x00; + } + } + + return cfg; +} + +/* + ======================================================================================================================= + Merging function for configurations + ======================================================================================================================= + */ +void *merge_dir_conf(apr_pool_t *pool, void *BASE, void *ADD) +{ + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + example_config *base = (example_config *) BASE; + example_config *add = (example_config *) ADD; + example_config *conf = (example_config *) create_dir_conf(pool, "Merged configuration"); + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + conf->enabled = (add->enabled == 0) ? base->enabled : add->enabled; + conf->typeOfAction = add->typeOfAction ? add->typeOfAction : base->typeOfAction; + strcpy(conf->path, strlen(add->path) ? add->path : base->path); + return conf; +}@@ -1520,11 +1599,12 @@ module AP_MODULE_DECLARE_DATA example_module=< +
Summing up
-We have now looked at how to create simple modules for Apache and +We have now looked at how to create simple modules for Apache HTTP Server 2.4 and configuring them. What you do next is entirely up to you, but it is my hope that something valuable has come out of reading this documentation. If you have questions on how to further develop modules, you are welcome @@ -1535,38 +1615,60 @@ or check out the rest of our documentation for further tips.
Some useful snippets of code
-Retrieve a variable from POST form data
- - - --+ @@ -1576,23 +1678,24 @@ or check out the rest of our documentation for further tips. -const
char
*
read_post_value(
const
char
*
key)
-{
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
-const
apr_array_header_t*
fields;
-int
i;
- apr_table_entry_t*
e=
0
;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- e=
(
apr_table_entry_t*
)
fields-
>
elts;
-for
(
i=
0
;
i<
fields-
>
nelts;
i+
+
)
{
-if
(
!
strcmp
(
e[
i]
.
key,
key)
)
return
e[
i]
.
val;
-}
-return
0
;
-}
-static
int
example_handler(
request_req*
r)
-{
-/*~~~~~~~~~~~~~~~~~~~~~~*/
- apr_array_header_t*
POST;
-const
char
*
value;
-/*~~~~~~~~~~~~~~~~~~~~~~*/
- ap_parse_form_data(
r,
NULL
,
&
POST,
-
1
,
8192
)
;
+Retrieve variables from POST form data
+ + + ++typedef struct { + const char* key; + const char* value; +} keyValuePair; + +keyValuePair* readPost(request_req* r) { + apr_array_header_t *pairs = NULL; + apr_off_t len; + apr_size_t size; + int res; + int i = 0; + char *buffer; + keyValuePair* kvp; + + res = ap_parse_form_data(r, NULL, &pairs, -1, HUGE_STRING_LEN); + if (res != OK || !pairs) return NULL; /* Return NULL if we failed or if there are is no POST data */ + kvp = apr_pcalloc(r->pool, sizeof(keyValuePair) * (pairs->nelts + 1)); + while (pairs && !apr_is_empty_array(pairs)) { + i++; + ap_form_pair_t *pair = (ap_form_pair_t *) apr_array_pop(pairs); + apr_brigade_length(pair->value, 1, &len); + size = (apr_size_t) len; + buffer = apr_palloc(r->pool, size + 1); + apr_brigade_flatten(pair->value, buffer, &size); + buffer[len] = 0; + kvp[i]->key = apr_pstrdup(r->pool, pair->name); + kvp[i]->value = buffer; + } + return kvp; +} + +static int example_handler(request_req *r) +{ + /*~~~~~~~~~~~~~~~~~~~~~~*/ - value+ keyValuePair* formData; + /*~~~~~~~~~~~~~~~~~~~~~~*/ + + formData = readPost(); + if (formData) { + int i; + for (i = 0; formData[i]; i++) { + ap_rprintf(r, "%s = %s\n", formData[i]->key, formData[i]->value); + } + } + return OK; +} +=
read_post_value(
POST,
"
valueA
"
)
;
-if
(
!
value)
value=
"
(undefined)
"
;
- ap_rprintf(
r,
"
The value of valueA is:
%s
"
,
value)
;
-return
OK;
-}
--+static
int
example_handler(
request_req*
r)
-{
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
-const
apr_array_header_t*
fields;
-int
i;
- apr_table_entry_t*
e=
0
;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- - fields=
apr_table_elts(
r-
>
headers_in)
;
- e=
(
apr_table_entry_t*
)
fields-
>
elts;
-for
(
i=
0
;
i<
fields-
>
nelts;
i+
+
)
{
- ap_rprintf(
r,
"
<b>
%s
</b>:
%s
<br/>
"
,
e[
i]
.
key,
e[
i]
.
val)
;
-}
-return
OK;
-}
-+static int example_handler(request_req *r) +{ + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + const apr_array_header_t *fields; + int i; + apr_table_entry_t *e = 0; + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + fields = apr_table_elts(r->headers_in); + e = (apr_table_entry_t *) fields->elts; + for(i = 0; i < fields->nelts; i++) { + ap_rprintf(r, "<b>%s</b>: %s<br/>", e[i].key, e[i].val); + } + return OK; +} ++ @@ -1602,64 +1705,87 @@ or check out the rest of our documentation for further tips. --static
int
util_read(
request_rec*
r,
const
char
*
*
rbuf,
apr_off_t*
size)
-{
-/*~~~~~~~~*/
-int
rc=
OK;
-/*~~~~~~~~*/
- -if
(
(
rc=
ap_setup_client_block(
r,
REQUEST_CHUNKED_ERROR)
)
)
{
-return
(
rc)
;
-}
- -if
(
ap_should_client_block(
r)
)
{
- -/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
-char
argsbuffer[
HUGE_STRING_LEN]
;
- apr_off_t rsize,
len_read,
rpos=
0
;
- apr_off_t length=
r-
>
remaining
;
-/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
- -*
rbuf=
(
const
char
*
)
apr_pcalloc(
r-
>
pool
,
(
apr_size_t)
(
length+
1
)
)
;
-*
size=
length;
-while
(
(
len_read=
ap_get_client_block(
r,
argsbuffer,
sizeof
(
argsbuffer)
)
)
>
0
)
{
-if
(
(
rpos+
len_read)
>
length)
{
- rsize=
length-
rpos;
-}
-else
{
- rsize=
len_read;
-}
- -memcpy
(
(
char
*
)
*
rbuf+
rpos,
argsbuffer,
(
size_t
)
rsize)
;
- rpos+
=
rsize;
-}
-}
-return
(
rc)
;
-}
- -static
int
example_handler(
request_req*
r)
-{
-/*~~~~~~~~~~~~~~~~*/
- apr_off_t size;
-const
char
*
buffer;
-/*~~~~~~~~~~~~~~~~*/
- -if
(
util_read(
r,
&
data,
&
size)
=
=
OK)
{
- ap_rprintf(
"
We read a request body that was
%u
bytes long
"
,
size)
;
-}
-return
OK;
-}
++static int util_read(request_rec *r, const char **rbuf, apr_off_t *size) +{ + /*~~~~~~~~*/ + int rc = OK; + /*~~~~~~~~*/ + + if((rc = ap_setup_client_block(r, REQUEST_CHUNKED_ERROR))) { + return(rc); + } + + if(ap_should_client_block(r)) { + + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + char argsbuffer[HUGE_STRING_LEN]; + apr_off_t rsize, len_read, rpos = 0; + apr_off_t length = r->remaining; + /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ + + *rbuf = (const char *) apr_pcalloc(r->pool, (apr_size_t) (length + 1)); + *size = length; + while((len_read = ap_get_client_block(r, argsbuffer, sizeof(argsbuffer))) > 0) { + if((rpos + len_read) > length) { + rsize = length - rpos; + } + else { + rsize = len_read; + } + + memcpy((char *) *rbuf + rpos, argsbuffer, (size_t) rsize); + rpos += rsize; + } + } + return(rc); +} + +static int example_handler(request_req* r) +{ + /*~~~~~~~~~~~~~~~~*/ + apr_off_t size; + const char *buffer; + /*~~~~~~~~~~~~~~~~*/ + + if(util_read(r, &data, &size) == OK) { + ap_rprintf("We read a request body that was %u bytes long", size); + } + return OK; +}+ +Available Languages: en
-+Comments
Notice:+
This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our mailing lists.