1 /* Copyright 2000-2006 The Apache Software Foundation or its licensors, as
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 * @brief Apache filter library
26 #include "apr_buckets.h"
38 /** Returned by the bottom-most filter if no data was written.
39 * @see ap_pass_brigade(). */
40 #define AP_NOBODY_WROTE -1
41 /** Returned by the bottom-most filter if no data was read.
42 * @see ap_get_brigade(). */
43 #define AP_NOBODY_READ -2
44 /** Returned when?? @bug find out when! */
45 #define AP_FILTER_ERROR -3
48 * @brief input filtering modes
51 /** The filter should return at most readbytes data. */
53 /** The filter should return at most one line of CRLF data.
54 * (If a potential line is too long or no CRLF is found, the
55 * filter may return partial data).
58 /** The filter should implicitly eat any CRLF pairs that it sees. */
60 /** The filter read should be treated as speculative and any returned
61 * data should be stored for later retrieval in another mode. */
63 /** The filter read should be exhaustive and read until it can not
65 * Use this mode with extreme caution.
68 /** The filter should initialize the connection if needed,
69 * NNTP or FTP over SSL for example.
75 * @defgroup APACHE_CORE_FILTER Filter Chain
76 * @ingroup APACHE_CORE
78 * Filters operate using a "chaining" mechanism. The filters are chained
79 * together into a sequence. When output is generated, it is passed through
80 * each of the filters on this chain, until it reaches the end (or "bottom")
81 * and is placed onto the network.
83 * The top of the chain, the code generating the output, is typically called
84 * a "content generator." The content generator's output is fed into the
85 * filter chain using the standard Apache output mechanisms: ap_rputs(),
86 * ap_rprintf(), ap_rwrite(), etc.
88 * Each filter is defined by a callback. This callback takes the output from
89 * the previous filter (or the content generator if there is no previous
90 * filter), operates on it, and passes the result to the next filter in the
91 * chain. This pass-off is performed using the ap_fc_* functions, such as
92 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
94 * When content generation is complete, the system will pass an "end of
95 * stream" marker into the filter chain. The filters will use this to flush
96 * out any internal state and to detect incomplete syntax (for example, an
97 * unterminated SSI directive).
100 /* forward declare the filter type */
101 typedef struct ap_filter_t ap_filter_t;
104 * @name Filter callbacks
106 * This function type is used for filter callbacks. It will be passed a
107 * pointer to "this" filter, and a "bucket" containing the content to be
110 * In filter->ctx, the callback will find its context. This context is
111 * provided here, so that a filter may be installed multiple times, each
112 * receiving its own per-install context pointer.
114 * Callbacks are associated with a filter definition, which is specified
115 * by name. See ap_register_input_filter() and ap_register_output_filter()
116 * for setting the association between a name for a filter and its
117 * associated callback (and other information).
119 * If the initialization function argument passed to the registration
120 * functions is non-NULL, it will be called iff the filter is in the input
121 * or output filter chains and before any data is generated to allow the
122 * filter to prepare for processing.
124 * The *bucket structure (and all those referenced by ->next and ->prev)
125 * should be considered "const". The filter is allowed to modify the
126 * next/prev to insert/remove/replace elements in the bucket list, but
127 * the types and values of the individual buckets should not be altered.
129 * For the input and output filters, the return value of a filter should be
130 * an APR status value. For the init function, the return value should
131 * be an HTTP error code or OK if it was successful.
136 typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f,
137 apr_bucket_brigade *b);
138 typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f,
139 apr_bucket_brigade *b,
140 ap_input_mode_t mode,
141 apr_read_type_e block,
142 apr_off_t readbytes);
143 typedef int (*ap_init_filter_func)(ap_filter_t *f);
145 typedef union ap_filter_func {
146 ap_out_filter_func out_func;
147 ap_in_filter_func in_func;
153 * Filters have different types/classifications. These are used to group
154 * and sort the filters to properly sequence their operation.
156 * The types have a particular sort order, which allows us to insert them
157 * into the filter chain in a determistic order. Within a particular grouping,
158 * the ordering is equivalent to the order of calls to ap_add_*_filter().
161 /** These filters are used to alter the content that is passed through
162 * them. Examples are SSI or PHP. */
163 AP_FTYPE_RESOURCE = 10,
164 /** These filters are used to alter the content as a whole, but after all
165 * AP_FTYPE_RESOURCE filters are executed. These filters should not
166 * change the content-type. An example is deflate. */
167 AP_FTYPE_CONTENT_SET = 20,
168 /** These filters are used to handle the protocol between server and
169 * client. Examples are HTTP and POP. */
170 AP_FTYPE_PROTOCOL = 30,
171 /** These filters implement transport encodings (e.g., chunking). */
172 AP_FTYPE_TRANSCODE = 40,
173 /** These filters will alter the content, but in ways that are
174 * more strongly associated with the connection. Examples are
175 * splitting an HTTP connection into multiple requests and
176 * buffering HTTP responses across multiple requests.
178 * It is important to note that these types of filters are not
179 * allowed in a sub-request. A sub-request's output can certainly
180 * be filtered by ::AP_FTYPE_RESOURCE filters, but all of the "final
181 * processing" is determined by the main request. */
182 AP_FTYPE_CONNECTION = 50,
183 /** These filters don't alter the content. They are responsible for
184 * sending/receiving data to/from the client. */
185 AP_FTYPE_NETWORK = 60
189 * This is the request-time context structure for an installed filter (in
190 * the output filter chain). It provides the callback to use for filtering,
191 * the request this filter is associated with (which is important when
192 * an output chain also includes sub-request filters), the context for this
193 * installed filter, and the filter ordering/chaining fields.
195 * Filter callbacks are free to use ->ctx as they please, to store context
196 * during the filter process. Generally, this is superior over associating
197 * the state directly with the request. A callback should not change any of
201 typedef struct ap_filter_rec_t ap_filter_rec_t;
202 typedef struct ap_filter_provider_t ap_filter_provider_t;
205 * @brief This structure is used for recording information about the
206 * registered filters. It associates a name with the filter's callback
209 * At the moment, these are simply linked in a chain, so a ->next pointer
212 * It is used for any filter that can be inserted in the filter chain.
213 * This may be either a httpd-2.0 filter or a mod_filter harness.
214 * In the latter case it contains dispatch, provider and protocol information.
215 * In the former case, the new fields (from dispatch) are ignored.
217 struct ap_filter_rec_t {
218 /** The registered name for this filter */
221 /** The function to call when this filter is invoked. */
222 ap_filter_func filter_func;
224 /** The function to call before the handlers are invoked. Notice
225 * that this function is called only for filters participating in
226 * the http protocol. Filters for other protocols are to be
227 * initialized by the protocols themselves.
229 ap_init_filter_func filter_init_func;
231 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
232 * An AP_FTYPE_CONTENT filter modifies the data based on information
233 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
234 * data based on the type of connection.
236 ap_filter_type ftype;
238 /** The next filter_rec in the list */
239 struct ap_filter_rec_t *next;
241 /** Providers for this filter */
242 ap_filter_provider_t *providers;
244 /** Trace level for this filter */
247 /** Protocol flags for this filter */
248 unsigned int proto_flags;
252 * @brief The representation of a filter chain.
254 * Each request has a list
255 * of these structures which are called in turn to filter the data. Sub
256 * requests get an exact copy of the main requests filter chain.
259 /** The internal representation of this filter. This includes
260 * the filter's name, type, and the actual function pointer.
262 ap_filter_rec_t *frec;
264 /** A place to store any data associated with the current filter */
267 /** The next filter in the chain */
270 /** The request_rec associated with the current filter. If a sub-request
271 * adds filters, then the sub-request is the request associated with the
276 /** The conn_rec associated with the current filter. This is analogous
277 * to the request_rec, except that it is used for input filtering.
283 * Get the current bucket brigade from the next filter on the filter
284 * stack. The filter returns an apr_status_t value. If the bottom-most
285 * filter doesn't read from the network, then ::AP_NOBODY_READ is returned.
286 * The bucket brigade will be empty when there is nothing left to get.
287 * @param filter The next filter in the chain
288 * @param bucket The current bucket brigade. The original brigade passed
289 * to ap_get_brigade() must be empty.
290 * @param mode The way in which the data should be read
291 * @param block How the operations should be performed
292 * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ
293 * @param readbytes How many bytes to read from the next filter.
295 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter,
296 apr_bucket_brigade *bucket,
297 ap_input_mode_t mode,
298 apr_read_type_e block,
299 apr_off_t readbytes);
302 * Pass the current bucket brigade down to the next filter on the filter
303 * stack. The filter returns an apr_status_t value. If the bottom-most
304 * filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned.
305 * The caller relinquishes ownership of the brigade.
306 * @param filter The next filter in the chain
307 * @param bucket The current bucket brigade
309 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter,
310 apr_bucket_brigade *bucket);
313 * This function is used to register an input filter with the system.
314 * After this registration is performed, then a filter may be added
315 * into the filter chain by using ap_add_input_filter() and simply
316 * specifying the name.
318 * @param name The name to attach to the filter function
319 * @param filter_func The filter function to name
320 * @param filter_init The function to call before the filter handlers
322 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
323 * ::AP_FTYPE_CONNECTION
324 * @see add_input_filter()
326 AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
327 ap_in_filter_func filter_func,
328 ap_init_filter_func filter_init,
329 ap_filter_type ftype);
331 /** @deprecated @see ap_register_output_filter_protocol */
332 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
333 ap_out_filter_func filter_func,
334 ap_init_filter_func filter_init,
335 ap_filter_type ftype);
337 /* For httpd-?.? I suggest replacing the above with
338 #define ap_register_output_filter(name,ffunc,init,ftype) \
339 ap_register_output_filter_protocol(name,ffunc,init,ftype,0)
343 * This function is used to register an output filter with the system.
344 * After this registration is performed, then a filter may be added
345 * directly to the filter chain by using ap_add_output_filter() and
346 * simply specifying the name, or as a provider under mod_filter.
348 * @param name The name to attach to the filter function
349 * @param filter_func The filter function to name
350 * @param filter_init The function to call before the filter handlers
352 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
353 * ::AP_FTYPE_CONNECTION
354 * @param proto_flags Protocol flags: logical OR of AP_FILTER_PROTO_* bits
355 * @return the filter rec
356 * @see ap_add_output_filter()
358 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter_protocol(
360 ap_out_filter_func filter_func,
361 ap_init_filter_func filter_init,
362 ap_filter_type ftype,
363 unsigned int proto_flags);
366 * Adds a named filter into the filter chain on the specified request record.
367 * The filter will be installed with the specified context pointer.
369 * Filters added in this way will always be placed at the end of the filters
370 * that have the same type (thus, the filters have the same order as the
371 * calls to ap_add_filter). If the current filter chain contains filters
372 * from another request, then this filter will be added before those other
375 * To re-iterate that last comment. This function is building a FIFO
376 * list of filters. Take note of that when adding your filter to the chain.
378 * @param name The name of the filter to add
379 * @param ctx Context data to provide to the filter
380 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
381 * @param c The connection to add the fillter for
383 AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx,
384 request_rec *r, conn_rec *c);
387 * Variant of ap_add_input_filter() that accepts a registered filter handle
388 * (as returned by ap_register_input_filter()) rather than a filter name
390 * @param f The filter handle to add
391 * @param ctx Context data to provide to the filter
392 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
393 * @param c The connection to add the fillter for
395 AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
401 * Returns the filter handle for use with ap_add_input_filter_handle.
403 * @param name The filter name to look up
405 AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name);
408 * Add a filter to the current request. Filters are added in a FIFO manner.
409 * The first filter added will be the first filter called.
410 * @param name The name of the filter to add
411 * @param ctx Context data to set in the filter
412 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
413 * @param c The connection to add this filter for
415 AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
416 request_rec *r, conn_rec *c);
419 * Variant of ap_add_output_filter() that accepts a registered filter handle
420 * (as returned by ap_register_output_filter()) rather than a filter name
422 * @param f The filter handle to add
423 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
424 * @param c The connection to add the fillter for
426 AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
432 * Returns the filter handle for use with ap_add_output_filter_handle.
434 * @param name The filter name to look up
436 AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name);
439 * Remove an input filter from either the request or connection stack
440 * it is associated with.
441 * @param f The filter to remove
444 AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f);
447 * Remove an output filter from either the request or connection stack
448 * it is associated with.
449 * @param f The filter to remove
452 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
454 /* The next two filters are for abstraction purposes only. They could be
455 * done away with, but that would require that we break modules if we ever
456 * want to change our filter registration method. The basic idea, is that
457 * all filters have a place to store data, the ctx pointer. These functions
458 * fill out that pointer with a bucket brigade, and retrieve that data on
459 * the next call. The nice thing about these functions, is that they
460 * automatically concatenate the bucket brigades together for you. This means
461 * that if you have already stored a brigade in the filters ctx pointer, then
462 * when you add more it will be tacked onto the end of that brigade. When
463 * you retrieve data, if you pass in a bucket brigade to the get function,
464 * it will append the current brigade onto the one that you are retrieving.
468 * prepare a bucket brigade to be setaside. If a different brigade was
469 * set-aside earlier, then the two brigades are concatenated together.
470 * @param f The current filter
471 * @param save_to The brigade that was previously set-aside. Regardless, the
472 * new bucket brigade is returned in this location.
473 * @param b The bucket brigade to save aside. This brigade is always empty
475 * @param p Ensure that all data in the brigade lives as long as this pool
477 AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f,
478 apr_bucket_brigade **save_to,
479 apr_bucket_brigade **b, apr_pool_t *p);
482 * Flush function for apr_brigade_* calls. This calls ap_pass_brigade
483 * to flush the brigade if the brigade buffer overflows.
484 * @param bb The brigade to flush
485 * @param ctx The filter to pass the brigade to
486 * @note this function has nothing to do with FLUSH buckets. It is simply
487 * a way to flush content out of a brigade and down a filter stack.
489 AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb,
493 * Flush the current brigade down the filter stack.
494 * @param f The filter we are passing to
495 * @param bb The brigade to flush
497 AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
500 * Write a buffer for the current filter, buffering if possible.
501 * @param f the filter we are writing to
502 * @param bb The brigade to buffer into
503 * @param data The data to write
504 * @param nbyte The number of bytes in the data
506 #define ap_fwrite(f, bb, data, nbyte) \
507 apr_brigade_write(bb, ap_filter_flush, f, data, nbyte)
510 * Write a buffer for the current filter, buffering if possible.
511 * @param f the filter we are writing to
512 * @param bb The brigade to buffer into
513 * @param str The string to write
515 #define ap_fputs(f, bb, str) \
516 apr_brigade_puts(bb, ap_filter_flush, f, str)
519 * Write a character for the current filter, buffering if possible.
520 * @param f the filter we are writing to
521 * @param bb The brigade to buffer into
522 * @param c The character to write
524 #define ap_fputc(f, bb, c) \
525 apr_brigade_putc(bb, ap_filter_flush, f, c)
528 * Write an unspecified number of strings to the current filter
529 * @param f the filter we are writing to
530 * @param bb The brigade to buffer into
531 * @param ... The strings to write
533 AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
534 apr_bucket_brigade *bb,
538 * Output data to the filter in printf format
539 * @param f the filter we are writing to
540 * @param bb The brigade to buffer into
541 * @param fmt The format string
542 * @param ... The argumets to use to fill out the format string
544 AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
545 apr_bucket_brigade *bb,
548 __attribute__((format(printf,3,4)));
551 * set protocol requirements for an output content filter
552 * (only works with AP_FTYPE_RESOURCE and AP_FTYPE_CONTENT_SET)
553 * @param f the filter in question
554 * @param proto_flags Logical OR of AP_FILTER_PROTO_* bits
556 AP_DECLARE(void) ap_filter_protocol(ap_filter_t* f, unsigned int proto_flags);
558 /** Filter changes contents (so invalidating checksums/etc) */
559 #define AP_FILTER_PROTO_CHANGE 0x1
561 /** Filter changes length of contents (so invalidating content-length/etc) */
562 #define AP_FILTER_PROTO_CHANGE_LENGTH 0x2
564 /** Filter requires complete input and can't work on byteranges */
565 #define AP_FILTER_PROTO_NO_BYTERANGE 0x4
567 /** Filter should not run in a proxy */
568 #define AP_FILTER_PROTO_NO_PROXY 0x8
570 /** Filter makes output non-cacheable */
571 #define AP_FILTER_PROTO_NO_CACHE 0x10
573 /** Filter is incompatible with "Cache-Control: no-transform" */
574 #define AP_FILTER_PROTO_TRANSFORM 0x20
580 #endif /* !AP_FILTER_H */