1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements. See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License. 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"
39 * @brief input filtering modes
42 /** The filter should return at most readbytes data. */
44 /** The filter should return at most one line of CRLF data.
45 * (If a potential line is too long or no CRLF is found, the
46 * filter may return partial data).
49 /** The filter should implicitly eat any CRLF pairs that it sees. */
51 /** The filter read should be treated as speculative and any returned
52 * data should be stored for later retrieval in another mode. */
54 /** The filter read should be exhaustive and read until it can not
56 * Use this mode with extreme caution.
59 /** The filter should initialize the connection if needed,
60 * NNTP or FTP over SSL for example.
66 * @defgroup APACHE_CORE_FILTER Filter Chain
67 * @ingroup APACHE_CORE
69 * Filters operate using a "chaining" mechanism. The filters are chained
70 * together into a sequence. When output is generated, it is passed through
71 * each of the filters on this chain, until it reaches the end (or "bottom")
72 * and is placed onto the network.
74 * The top of the chain, the code generating the output, is typically called
75 * a "content generator." The content generator's output is fed into the
76 * filter chain using the standard Apache output mechanisms: ap_rputs(),
77 * ap_rprintf(), ap_rwrite(), etc.
79 * Each filter is defined by a callback. This callback takes the output from
80 * the previous filter (or the content generator if there is no previous
81 * filter), operates on it, and passes the result to the next filter in the
82 * chain. This pass-off is performed using the ap_fc_* functions, such as
83 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
85 * When content generation is complete, the system will pass an "end of
86 * stream" marker into the filter chain. The filters will use this to flush
87 * out any internal state and to detect incomplete syntax (for example, an
88 * unterminated SSI directive).
93 /* forward declare the filter type */
94 typedef struct ap_filter_t ap_filter_t;
97 * @name Filter callbacks
99 * This function type is used for filter callbacks. It will be passed a
100 * pointer to "this" filter, and a "bucket brigade" containing the content
103 * In filter->ctx, the callback will find its context. This context is
104 * provided here, so that a filter may be installed multiple times, each
105 * receiving its own per-install context pointer.
107 * Callbacks are associated with a filter definition, which is specified
108 * by name. See ap_register_input_filter() and ap_register_output_filter()
109 * for setting the association between a name for a filter and its
110 * associated callback (and other information).
112 * If the initialization function argument passed to the registration
113 * functions is non-NULL, it will be called iff the filter is in the input
114 * or output filter chains and before any data is generated to allow the
115 * filter to prepare for processing.
117 * The bucket brigade always belongs to the caller, but the filter
118 * is free to use the buckets within it as it sees fit. Normally,
119 * the brigade will be returned empty. Buckets *may not* be retained
120 * between successive calls to the filter unless they have been
121 * "set aside" with a call apr_bucket_setaside. Typically this will
122 * be done with ap_save_brigade(). Buckets removed from the brigade
123 * become the responsibility of the filter, which must arrange for
124 * them to be deleted, either by doing so directly or by inserting
125 * them in a brigade which will subsequently be destroyed.
127 * For the input and output filters, the return value of a filter should be
128 * an APR status value. For the init function, the return value should
129 * be an HTTP error code or OK if it was successful.
134 typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f,
135 apr_bucket_brigade *b);
136 typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f,
137 apr_bucket_brigade *b,
138 ap_input_mode_t mode,
139 apr_read_type_e block,
140 apr_off_t readbytes);
141 typedef int (*ap_init_filter_func)(ap_filter_t *f);
143 typedef union ap_filter_func {
144 ap_out_filter_func out_func;
145 ap_in_filter_func in_func;
151 * Filters have different types/classifications. These are used to group
152 * and sort the filters to properly sequence their operation.
154 * The types have a particular sort order, which allows us to insert them
155 * into the filter chain in a determistic order. Within a particular grouping,
156 * the ordering is equivalent to the order of calls to ap_add_*_filter().
159 /** These filters are used to alter the content that is passed through
160 * them. Examples are SSI or PHP. */
161 AP_FTYPE_RESOURCE = 10,
162 /** These filters are used to alter the content as a whole, but after all
163 * AP_FTYPE_RESOURCE filters are executed. These filters should not
164 * change the content-type. An example is deflate. */
165 AP_FTYPE_CONTENT_SET = 20,
166 /** These filters are used to handle the protocol between server and
167 * client. Examples are HTTP and POP. */
168 AP_FTYPE_PROTOCOL = 30,
169 /** These filters implement transport encodings (e.g., chunking). */
170 AP_FTYPE_TRANSCODE = 40,
171 /** These filters will alter the content, but in ways that are
172 * more strongly associated with the connection. Examples are
173 * splitting an HTTP connection into multiple requests and
174 * buffering HTTP responses across multiple requests.
176 * It is important to note that these types of filters are not
177 * allowed in a sub-request. A sub-request's output can certainly
178 * be filtered by ::AP_FTYPE_RESOURCE filters, but all of the "final
179 * processing" is determined by the main request. */
180 AP_FTYPE_CONNECTION = 50,
181 /** These filters don't alter the content. They are responsible for
182 * sending/receiving data to/from the client. */
183 AP_FTYPE_NETWORK = 60
187 * This is the request-time context structure for an installed filter (in
188 * the output filter chain). It provides the callback to use for filtering,
189 * the request this filter is associated with (which is important when
190 * an output chain also includes sub-request filters), the context for this
191 * installed filter, and the filter ordering/chaining fields.
193 * Filter callbacks are free to use ->ctx as they please, to store context
194 * during the filter process. Generally, this is superior over associating
195 * the state directly with the request. A callback should not change any of
199 typedef struct ap_filter_rec_t ap_filter_rec_t;
200 typedef struct ap_filter_provider_t ap_filter_provider_t;
203 * @brief This structure is used for recording information about the
204 * registered filters. It associates a name with the filter's callback
207 * At the moment, these are simply linked in a chain, so a ->next pointer
210 * It is used for any filter that can be inserted in the filter chain.
211 * This may be either a httpd-2.0 filter or a mod_filter harness.
212 * In the latter case it contains dispatch, provider and protocol information.
213 * In the former case, the new fields (from dispatch) are ignored.
215 struct ap_filter_rec_t {
216 /** The registered name for this filter */
219 /** The function to call when this filter is invoked. */
220 ap_filter_func filter_func;
222 /** The function to call directly before the handlers are invoked
223 * for a request. The init function is called once directly
224 * before running the handlers for a request or subrequest. The
225 * init function is never called for a connection filter (with
226 * ftype >= AP_FTYPE_CONNECTION). Any use of this function for
227 * filters for protocols other than HTTP is specified by the
228 * module supported that protocol.
230 ap_init_filter_func filter_init_func;
232 /** The next filter_rec in the list */
233 struct ap_filter_rec_t *next;
235 /** Providers for this filter */
236 ap_filter_provider_t *providers;
238 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
239 * An AP_FTYPE_CONTENT filter modifies the data based on information
240 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
241 * data based on the type of connection.
243 ap_filter_type ftype;
245 /** Trace level for this filter */
248 /** Protocol flags for this filter */
249 unsigned int proto_flags;
253 * @brief The representation of a filter chain.
255 * Each request has a list
256 * of these structures which are called in turn to filter the data. Sub
257 * requests get an exact copy of the main requests filter chain.
260 /** The internal representation of this filter. This includes
261 * the filter's name, type, and the actual function pointer.
263 ap_filter_rec_t *frec;
265 /** A place to store any data associated with the current filter */
268 /** The next filter in the chain */
271 /** The request_rec associated with the current filter. If a sub-request
272 * adds filters, then the sub-request is the request associated with the
277 /** The conn_rec associated with the current filter. This is analogous
278 * to the request_rec, except that it is used for connection filters.
284 * Get the current bucket brigade from the next filter on the filter
285 * stack. The filter returns an apr_status_t value. If the bottom-most
286 * filter doesn't read from the network, then ::AP_NOBODY_READ is returned.
287 * The bucket brigade will be empty when there is nothing left to get.
288 * @param filter The next filter in the chain
289 * @param bucket The current bucket brigade. The original brigade passed
290 * to ap_get_brigade() must be empty.
291 * @param mode The way in which the data should be read
292 * @param block How the operations should be performed
293 * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ
294 * @param readbytes How many bytes to read from the next filter.
296 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter,
297 apr_bucket_brigade *bucket,
298 ap_input_mode_t mode,
299 apr_read_type_e block,
300 apr_off_t readbytes);
303 * Pass the current bucket brigade down to the next filter on the filter
304 * stack. The filter returns an apr_status_t value. If the bottom-most
305 * filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned.
306 * @param filter The next filter in the chain
307 * @param bucket The current bucket brigade
309 * @remark Ownership of the brigade is retained by the caller. On return,
310 * the contents of the brigade are UNDEFINED, and the caller must
311 * either call apr_brigade_cleanup or apr_brigade_destroy on
314 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter,
315 apr_bucket_brigade *bucket);
318 * This function is used to register an input filter with the system.
319 * After this registration is performed, then a filter may be added
320 * into the filter chain by using ap_add_input_filter() and simply
321 * specifying the name.
323 * @param name The name to attach to the filter function
324 * @param filter_func The filter function to name
325 * @param filter_init The function to call before the filter handlers
327 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT_SET or
328 * ::AP_FTYPE_CONNECTION
329 * @see add_input_filter()
331 AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
332 ap_in_filter_func filter_func,
333 ap_init_filter_func filter_init,
334 ap_filter_type ftype);
336 /** @deprecated @see ap_register_output_filter_protocol */
337 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
338 ap_out_filter_func filter_func,
339 ap_init_filter_func filter_init,
340 ap_filter_type ftype);
342 /* For httpd-?.? I suggest replacing the above with
343 #define ap_register_output_filter(name,ffunc,init,ftype) \
344 ap_register_output_filter_protocol(name,ffunc,init,ftype,0)
348 * This function is used to register an output filter with the system.
349 * After this registration is performed, then a filter may be added
350 * directly to the filter chain by using ap_add_output_filter() and
351 * simply specifying the name, or as a provider under mod_filter.
353 * @param name The name to attach to the filter function
354 * @param filter_func The filter function to name
355 * @param filter_init The function to call before the filter handlers
357 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT_SET or
358 * ::AP_FTYPE_CONNECTION
359 * @param proto_flags Protocol flags: logical OR of AP_FILTER_PROTO_* bits
360 * @return the filter rec
361 * @see ap_add_output_filter()
363 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter_protocol(
365 ap_out_filter_func filter_func,
366 ap_init_filter_func filter_init,
367 ap_filter_type ftype,
368 unsigned int proto_flags);
371 * Adds a named filter into the filter chain on the specified request record.
372 * The filter will be installed with the specified context pointer.
374 * Filters added in this way will always be placed at the end of the filters
375 * that have the same type (thus, the filters have the same order as the
376 * calls to ap_add_filter). If the current filter chain contains filters
377 * from another request, then this filter will be added before those other
380 * To re-iterate that last comment. This function is building a FIFO
381 * list of filters. Take note of that when adding your filter to the chain.
383 * @param name The name of the filter to add
384 * @param ctx Context data to provide to the filter
385 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
386 * @param c The connection to add the fillter for
388 AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx,
389 request_rec *r, conn_rec *c);
392 * Variant of ap_add_input_filter() that accepts a registered filter handle
393 * (as returned by ap_register_input_filter()) rather than a filter name
395 * @param f The filter handle to add
396 * @param ctx Context data to provide to the filter
397 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
398 * @param c The connection to add the fillter for
400 AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
406 * Returns the filter handle for use with ap_add_input_filter_handle.
408 * @param name The filter name to look up
410 AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name);
413 * Add a filter to the current request. Filters are added in a FIFO manner.
414 * The first filter added will be the first filter called.
415 * @param name The name of the filter to add
416 * @param ctx Context data to set in the filter
417 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
418 * @param c The connection to add this filter for
419 * @note If adding a connection-level output filter (i.e. where the type
420 * is >= AP_FTYPE_CONNECTION) during processing of a request, the request
421 * object r must be passed in to ensure the filter chains are modified
422 * correctly. f->r will still be initialized as NULL in the new filter.
424 AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
425 request_rec *r, conn_rec *c);
428 * Variant of ap_add_output_filter() that accepts a registered filter handle
429 * (as returned by ap_register_output_filter()) rather than a filter name
431 * @param f The filter handle to add
432 * @param ctx Context data to set in the filter
433 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
434 * @param c The connection to add the filter for
435 * @note If adding a connection-level output filter (i.e. where the type
436 * is >= AP_FTYPE_CONNECTION) during processing of a request, the request
437 * object r must be passed in to ensure the filter chains are modified
438 * correctly. f->r will still be initialized as NULL in the new filter.
440 AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
446 * Returns the filter handle for use with ap_add_output_filter_handle.
448 * @param name The filter name to look up
450 AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name);
453 * Remove an input filter from either the request or connection stack
454 * it is associated with.
455 * @param f The filter to remove
458 AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f);
461 * Remove an output filter from either the request or connection stack
462 * it is associated with.
463 * @param f The filter to remove
466 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
468 /* The next two filters are for abstraction purposes only. They could be
469 * done away with, but that would require that we break modules if we ever
470 * want to change our filter registration method. The basic idea, is that
471 * all filters have a place to store data, the ctx pointer. These functions
472 * fill out that pointer with a bucket brigade, and retrieve that data on
473 * the next call. The nice thing about these functions, is that they
474 * automatically concatenate the bucket brigades together for you. This means
475 * that if you have already stored a brigade in the filters ctx pointer, then
476 * when you add more it will be tacked onto the end of that brigade. When
477 * you retrieve data, if you pass in a bucket brigade to the get function,
478 * it will append the current brigade onto the one that you are retrieving.
482 * prepare a bucket brigade to be setaside. If a different brigade was
483 * set-aside earlier, then the two brigades are concatenated together.
484 * @param f The current filter
485 * @param save_to The brigade that was previously set-aside. Regardless, the
486 * new bucket brigade is returned in this location.
487 * @param b The bucket brigade to save aside. This brigade is always empty
489 * @param p Ensure that all data in the brigade lives as long as this pool
491 AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f,
492 apr_bucket_brigade **save_to,
493 apr_bucket_brigade **b, apr_pool_t *p);
496 * Flush function for apr_brigade_* calls. This calls ap_pass_brigade
497 * to flush the brigade if the brigade buffer overflows.
498 * @param bb The brigade to flush
499 * @param ctx The filter to pass the brigade to
500 * @note this function has nothing to do with FLUSH buckets. It is simply
501 * a way to flush content out of a brigade and down a filter stack.
503 AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb,
507 * Flush the current brigade down the filter stack.
508 * @param f The filter we are passing to
509 * @param bb The brigade to flush
511 AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
514 * Write a buffer for the current filter, buffering if possible.
515 * @param f the filter we are writing to
516 * @param bb The brigade to buffer into
517 * @param data The data to write
518 * @param nbyte The number of bytes in the data
520 #define ap_fwrite(f, bb, data, nbyte) \
521 apr_brigade_write(bb, ap_filter_flush, f, data, nbyte)
524 * Write a buffer for the current filter, buffering if possible.
525 * @param f the filter we are writing to
526 * @param bb The brigade to buffer into
527 * @param str The string to write
529 #define ap_fputs(f, bb, str) \
530 apr_brigade_puts(bb, ap_filter_flush, f, str)
533 * Write a character for the current filter, buffering if possible.
534 * @param f the filter we are writing to
535 * @param bb The brigade to buffer into
536 * @param c The character to write
538 #define ap_fputc(f, bb, c) \
539 apr_brigade_putc(bb, ap_filter_flush, f, c)
542 * Write an unspecified number of strings to the current filter
543 * @param f the filter we are writing to
544 * @param bb The brigade to buffer into
545 * @param ... The strings to write
547 AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
548 apr_bucket_brigade *bb,
550 ap_func_attr_sentinel;
553 * Output data to the filter in printf format
554 * @param f the filter we are writing to
555 * @param bb The brigade to buffer into
556 * @param fmt The format string
557 * @param ... The argumets to use to fill out the format string
559 AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
560 apr_bucket_brigade *bb,
563 __attribute__((format(printf,3,4)));
566 * set protocol requirements for an output content filter
567 * (only works with AP_FTYPE_RESOURCE and AP_FTYPE_CONTENT_SET)
568 * @param f the filter in question
569 * @param proto_flags Logical OR of AP_FILTER_PROTO_* bits
571 AP_DECLARE(void) ap_filter_protocol(ap_filter_t* f, unsigned int proto_flags);
573 /** Filter changes contents (so invalidating checksums/etc) */
574 #define AP_FILTER_PROTO_CHANGE 0x1
576 /** Filter changes length of contents (so invalidating content-length/etc) */
577 #define AP_FILTER_PROTO_CHANGE_LENGTH 0x2
579 /** Filter requires complete input and can't work on byteranges */
580 #define AP_FILTER_PROTO_NO_BYTERANGE 0x4
582 /** Filter should not run in a proxy */
583 #define AP_FILTER_PROTO_NO_PROXY 0x8
585 /** Filter makes output non-cacheable */
586 #define AP_FILTER_PROTO_NO_CACHE 0x10
588 /** Filter is incompatible with "Cache-Control: no-transform" */
589 #define AP_FILTER_PROTO_TRANSFORM 0x20
599 #endif /* !AP_FILTER_H */