1 /* Copyright 2000-2004 The Apache Software Foundation
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
7 * http://www.apache.org/licenses/LICENSE-2.0
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
20 #include "apr_buckets.h"
34 * @brief Apache filter library
37 /** Returned by the bottom-most filter if no data was written.
38 * @see ap_pass_brigade(). */
39 #define AP_NOBODY_WROTE -1
40 /** Returned by the bottom-most filter if no data was read.
41 * @see ap_get_brigade(). */
42 #define AP_NOBODY_READ -2
43 /** Returned when?? @bug find out when! */
44 #define AP_FILTER_ERROR -3
47 * input filtering modes
50 /** The filter should return at most readbytes data. */
52 /** The filter should return at most one line of CRLF data.
53 * (If a potential line is too long or no CRLF is found, the
54 * filter may return partial data).
57 /** The filter should implicitly eat any CRLF pairs that it sees. */
59 /** The filter read should be treated as speculative and any returned
60 * data should be stored for later retrieval in another mode. */
62 /** The filter read should be exhaustive and read until it can not
64 * Use this mode with extreme caution.
67 /** The filter should initialize the connection if needed,
68 * NNTP or FTP over SSL for example.
74 * @defgroup filter FILTER CHAIN
76 * Filters operate using a "chaining" mechanism. The filters are chained
77 * together into a sequence. When output is generated, it is passed through
78 * each of the filters on this chain, until it reaches the end (or "bottom")
79 * and is placed onto the network.
81 * The top of the chain, the code generating the output, is typically called
82 * a "content generator." The content generator's output is fed into the
83 * filter chain using the standard Apache output mechanisms: ap_rputs(),
84 * ap_rprintf(), ap_rwrite(), etc.
86 * Each filter is defined by a callback. This callback takes the output from
87 * the previous filter (or the content generator if there is no previous
88 * filter), operates on it, and passes the result to the next filter in the
89 * chain. This pass-off is performed using the ap_fc_* functions, such as
90 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
92 * When content generation is complete, the system will pass an "end of
93 * stream" marker into the filter chain. The filters will use this to flush
94 * out any internal state and to detect incomplete syntax (for example, an
95 * unterminated SSI directive).
98 /* forward declare the filter type */
99 typedef struct ap_filter_t ap_filter_t;
102 * @name Filter callbacks
104 * This function type is used for filter callbacks. It will be passed a
105 * pointer to "this" filter, and a "bucket" containing the content to be
108 * In filter->ctx, the callback will find its context. This context is
109 * provided here, so that a filter may be installed multiple times, each
110 * receiving its own per-install context pointer.
112 * Callbacks are associated with a filter definition, which is specified
113 * by name. See ap_register_input_filter() and ap_register_output_filter()
114 * for setting the association between a name for a filter and its
115 * associated callback (and other information).
117 * If the initialization function argument passed to the registration
118 * functions is non-NULL, it will be called iff the filter is in the input
119 * or output filter chains and before any data is generated to allow the
120 * filter to prepare for processing.
122 * The *bucket structure (and all those referenced by ->next and ->prev)
123 * should be considered "const". The filter is allowed to modify the
124 * next/prev to insert/remove/replace elements in the bucket list, but
125 * the types and values of the individual buckets should not be altered.
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 * 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 before the handlers are invoked. Notice
223 * that this function is called only for filters participating in
224 * the http protocol. Filters for other protocols are to be
225 * initialized by the protocols themselves.
227 ap_init_filter_func filter_init_func;
229 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
230 * An AP_FTYPE_CONTENT filter modifies the data based on information
231 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
232 * data based on the type of connection.
234 ap_filter_type ftype;
236 /** The next filter_rec in the list */
237 struct ap_filter_rec_t *next;
239 /** Providers for this filter */
240 ap_filter_provider_t *providers;
242 /** Trace level for this filter */
245 /** Protocol flags for this filter */
246 unsigned int proto_flags;
250 * The representation of a filter chain. Each request has a list
251 * of these structures which are called in turn to filter the data. Sub
252 * requests get an exact copy of the main requests filter chain.
255 /** The internal representation of this filter. This includes
256 * the filter's name, type, and the actual function pointer.
258 ap_filter_rec_t *frec;
260 /** A place to store any data associated with the current filter */
263 /** The next filter in the chain */
266 /** The request_rec associated with the current filter. If a sub-request
267 * adds filters, then the sub-request is the request associated with the
272 /** The conn_rec associated with the current filter. This is analogous
273 * to the request_rec, except that it is used for input filtering.
279 * Get the current bucket brigade from the next filter on the filter
280 * stack. The filter returns an apr_status_t value. If the bottom-most
281 * filter doesn't read from the network, then ::AP_NOBODY_READ is returned.
282 * The bucket brigade will be empty when there is nothing left to get.
283 * @param filter The next filter in the chain
284 * @param bucket The current bucket brigade. The original brigade passed
285 * to ap_get_brigade() must be empty.
286 * @param mode The way in which the data should be read
287 * @param block How the operations should be performed
288 * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ
289 * @param readbytes How many bytes to read from the next filter.
291 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter,
292 apr_bucket_brigade *bucket,
293 ap_input_mode_t mode,
294 apr_read_type_e block,
295 apr_off_t readbytes);
298 * Pass the current bucket brigade down to the next filter on the filter
299 * stack. The filter returns an apr_status_t value. If the bottom-most
300 * filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned.
301 * The caller relinquishes ownership of the brigade.
302 * @param filter The next filter in the chain
303 * @param bucket The current bucket brigade
305 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter,
306 apr_bucket_brigade *bucket);
309 * This function is used to register an input filter with the system.
310 * After this registration is performed, then a filter may be added
311 * into the filter chain by using ap_add_input_filter() and simply
312 * specifying the name.
314 * @param name The name to attach to the filter function
315 * @param filter_func The filter function to name
316 * @param filter_init The function to call before the filter handlers
318 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
319 * ::AP_FTYPE_CONNECTION
320 * @see add_input_filter()
322 AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
323 ap_in_filter_func filter_func,
324 ap_init_filter_func filter_init,
325 ap_filter_type ftype);
328 * This function is used to register an output filter with the system.
329 * After this registration is performed, then a filter may be added
330 * into the filter chain by using ap_add_output_filter() and simply
331 * specifying the name. It may also be used as a provider under mod_filter.
332 * This is (equivalent to) ap_register_output_filter_protocol with
333 * proto_flags=0, and is retained for back-compatibility with 2.0 modules.
335 * @param name The name to attach to the filter function
336 * @param filter_func The filter function to name
337 * @param filter_init The function to call before the filter handlers
339 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
340 * ::AP_FTYPE_CONNECTION
341 * @see ap_add_output_filter()
343 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
344 ap_out_filter_func filter_func,
345 ap_init_filter_func filter_init,
346 ap_filter_type ftype);
348 /* For httpd-2.2 I suggest replacing the above with
349 #define ap_register_output_filter(name,ffunc,init,ftype) \
350 ap_register_output_filter_protocol(name,ffunc,init,ftype,0)
354 * This function is used to register an output filter with the system.
355 * After this registration is performed, then a filter may be added
356 * into the filter chain by using ap_add_output_filter() and simply
357 * specifying the name. It may also be used as a provider under mod_filter.
359 * @param name The name to attach to the filter function
360 * @param filter_func The filter function to name
361 * @param filter_init The function to call before the filter handlers
363 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
364 * ::AP_FTYPE_CONNECTION
365 * @param proto_flags Protocol flags: logical OR of AP_FILTER_PROTO_* bits
366 * @see ap_add_output_filter()
368 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter_protocol(
370 ap_out_filter_func filter_func,
371 ap_init_filter_func filter_init,
372 ap_filter_type ftype,
373 unsigned int proto_flags);
376 * Adds a named filter into the filter chain on the specified request record.
377 * The filter will be installed with the specified context pointer.
379 * Filters added in this way will always be placed at the end of the filters
380 * that have the same type (thus, the filters have the same order as the
381 * calls to ap_add_filter). If the current filter chain contains filters
382 * from another request, then this filter will be added before those other
385 * To re-iterate that last comment. This function is building a FIFO
386 * list of filters. Take note of that when adding your filter to the chain.
388 * @param name The name of the filter to add
389 * @param ctx Context data to provide to the filter
390 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
391 * @param c The connection to add the fillter for
393 AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx,
394 request_rec *r, conn_rec *c);
397 * Variant of ap_add_input_filter() that accepts a registered filter handle
398 * (as returned by ap_register_input_filter()) rather than a filter name
400 * @param f The filter handle to add
401 * @param ctx Context data to provide to the filter
402 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
403 * @param c The connection to add the fillter for
405 AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
411 * Returns the filter handle for use with ap_add_input_filter_handle.
413 * @param name The filter name to look up
415 AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name);
418 * Add a filter to the current request. Filters are added in a FIFO manner.
419 * The first filter added will be the first filter called.
420 * @param name The name of the filter to add
421 * @param ctx Context data to set in the filter
422 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
423 * @param c The connection to add this filter for
425 AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
426 request_rec *r, conn_rec *c);
429 * Variant of ap_add_output_filter() that accepts a registered filter handle
430 * (as returned by ap_register_output_filter()) rather than a filter name
432 * @param f The filter handle to add
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 fillter for
436 AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
442 * Returns the filter handle for use with ap_add_output_filter_handle.
444 * @param name The filter name to look up
446 AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name);
449 * Remove an input filter from either the request or connection stack
450 * it is associated with.
451 * @param f The filter to remove
454 AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f);
457 * Remove an output filter from either the request or connection stack
458 * it is associated with.
459 * @param f The filter to remove
462 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
464 /* The next two filters are for abstraction purposes only. They could be
465 * done away with, but that would require that we break modules if we ever
466 * want to change our filter registration method. The basic idea, is that
467 * all filters have a place to store data, the ctx pointer. These functions
468 * fill out that pointer with a bucket brigade, and retrieve that data on
469 * the next call. The nice thing about these functions, is that they
470 * automatically concatenate the bucket brigades together for you. This means
471 * that if you have already stored a brigade in the filters ctx pointer, then
472 * when you add more it will be tacked onto the end of that brigade. When
473 * you retrieve data, if you pass in a bucket brigade to the get function,
474 * it will append the current brigade onto the one that you are retrieving.
478 * prepare a bucket brigade to be setaside. If a different brigade was
479 * set-aside earlier, then the two brigades are concatenated together.
480 * @param f The current filter
481 * @param save_to The brigade that was previously set-aside. Regardless, the
482 * new bucket brigade is returned in this location.
483 * @param b The bucket brigade to save aside. This brigade is always empty
485 * @param p Ensure that all data in the brigade lives as long as this pool
487 AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f,
488 apr_bucket_brigade **save_to,
489 apr_bucket_brigade **b, apr_pool_t *p);
492 * Flush function for apr_brigade_* calls. This calls ap_pass_brigade
493 * to flush the brigade if the brigade buffer overflows.
494 * @param bb The brigade to flush
495 * @param ctx The filter to pass the brigade to
496 * @note this function has nothing to do with FLUSH buckets. It is simply
497 * a way to flush content out of a brigade and down a filter stack.
499 AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb,
503 * Flush the current brigade down the filter stack.
504 * @param f The filter we are passing to
505 * @param bb The brigade to flush
507 AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
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 data The data to write
514 * @param nbyte The number of bytes in the data
516 #define ap_fwrite(f, bb, data, nbyte) \
517 apr_brigade_write(bb, ap_filter_flush, f, data, nbyte)
520 * Write a buffer for the current filter, buffering if possible.
521 * @param f the filter we are writing to
522 * @param bb The brigade to buffer into
523 * @param str The string to write
525 #define ap_fputs(f, bb, str) \
526 apr_brigade_puts(bb, ap_filter_flush, f, str)
529 * Write a character for the current filter, buffering if possible.
530 * @param f the filter we are writing to
531 * @param bb The brigade to buffer into
532 * @param c The character to write
534 #define ap_fputc(f, bb, c) \
535 apr_brigade_putc(bb, ap_filter_flush, f, c)
538 * Write an unspecified number of strings to the current filter
539 * @param f the filter we are writing to
540 * @param bb The brigade to buffer into
541 * @param ... The strings to write
543 AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
544 apr_bucket_brigade *bb,
548 * Output data to the filter in printf format
549 * @param f the filter we are writing to
550 * @param bb The brigade to buffer into
551 * @param fmt The format string
552 * @param ... The argumets to use to fill out the format string
554 AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
555 apr_bucket_brigade *bb,
558 __attribute__((format(printf,3,4)));
561 * set protocol requirements for an output content filter
562 * (only works with AP_FTYPE_RESOURCE and AP_FTYPE_CONTENT_SET)
563 * @param f the filter in question
564 * @param proto_flags Logical OR of AP_FILTER_PROTO_* bits
566 AP_DECLARE(void) ap_filter_protocol(ap_filter_t* f, unsigned int proto_flags);
568 /** Filter changes contents (so invalidating checksums/etc) */
569 #define AP_FILTER_PROTO_CHANGE 0x1
571 /** Filter changes length of contents (so invalidating content-length/etc) */
572 #define AP_FILTER_PROTO_CHANGE_LENGTH 0x2
574 /** Filter requires complete input and can't work on byteranges */
575 #define AP_FILTER_PROTO_NO_BYTERANGE 0x4
577 /** Filter should not run in a proxy */
578 #define AP_FILTER_PROTO_NO_PROXY 0x8
580 /** Filter makes output non-cacheable */
581 #define AP_FILTER_PROTO_NO_CACHE 0x10
583 /** Filter is incompatible with "Cache-Control: no-transform" */
584 #define AP_FILTER_PROTO_TRANSFORM 0x20
590 #endif /* !AP_FILTER_H */