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
* Pass the current bucket brigade down to the next filter on the filter
319
* stack checking for filter errors. The filter returns an apr_status_t value.
320
* Returns ::OK if the brigade is successfully passed
321
* ::AP_FILTER_ERROR on a filter error
322
* ::HTTP_INTERNAL_SERVER_ERROR on all other errors
323
* @param r The request rec
324
* @param bucket The current bucket brigade
325
* @param fmt The format string. If NULL defaults to "ap_pass_brigade returned"
326
* @param ... The arguments to use to fill out the format string
327
* @remark Ownership of the brigade is retained by the caller. On return,
328
* the contents of the brigade are UNDEFINED, and the caller must
329
* either call apr_brigade_cleanup or apr_brigade_destroy on
332
AP_DECLARE(apr_status_t) ap_pass_brigade_fchk(request_rec *r,
333
apr_bucket_brigade *bucket,
339
* This function is used to register an input filter with the system.
340
* After this registration is performed, then a filter may be added
341
* into the filter chain by using ap_add_input_filter() and simply
342
* specifying the name.
344
* @param name The name to attach to the filter function
345
* @param filter_func The filter function to name
346
* @param filter_init The function to call before the filter handlers
348
* @param ftype The type of filter function, either ::AP_FTYPE_CONTENT_SET or
349
* ::AP_FTYPE_CONNECTION
350
* @see add_input_filter()
352
AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
353
ap_in_filter_func filter_func,
354
ap_init_filter_func filter_init,
355
ap_filter_type ftype);
357
/** @deprecated @see ap_register_output_filter_protocol */
358
AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
359
ap_out_filter_func filter_func,
360
ap_init_filter_func filter_init,
361
ap_filter_type ftype);
363
/* For httpd-?.? I suggest replacing the above with
364
#define ap_register_output_filter(name,ffunc,init,ftype) \
365
ap_register_output_filter_protocol(name,ffunc,init,ftype,0)
369
* This function is used to register an output filter with the system.
370
* After this registration is performed, then a filter may be added
371
* directly to the filter chain by using ap_add_output_filter() and
372
* simply specifying the name, or as a provider under mod_filter.
374
* @param name The name to attach to the filter function
375
* @param filter_func The filter function to name
376
* @param filter_init The function to call before the filter handlers
378
* @param ftype The type of filter function, either ::AP_FTYPE_CONTENT_SET or
379
* ::AP_FTYPE_CONNECTION
380
* @param proto_flags Protocol flags: logical OR of AP_FILTER_PROTO_* bits
381
* @return the filter rec
382
* @see ap_add_output_filter()
384
AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter_protocol(
386
ap_out_filter_func filter_func,
387
ap_init_filter_func filter_init,
388
ap_filter_type ftype,
389
unsigned int proto_flags);
392
* Adds a named filter into the filter chain on the specified request record.
393
* The filter will be installed with the specified context pointer.
395
* Filters added in this way will always be placed at the end of the filters
396
* that have the same type (thus, the filters have the same order as the
397
* calls to ap_add_filter). If the current filter chain contains filters
398
* from another request, then this filter will be added before those other
401
* To re-iterate that last comment. This function is building a FIFO
402
* list of filters. Take note of that when adding your filter to the chain.
404
* @param name The name of the filter to add
405
* @param ctx Context data to provide to the filter
406
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
407
* @param c The connection to add the fillter for
409
AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx,
410
request_rec *r, conn_rec *c);
413
* Variant of ap_add_input_filter() that accepts a registered filter handle
414
* (as returned by ap_register_input_filter()) rather than a filter name
416
* @param f The filter handle to add
417
* @param ctx Context data to provide to the filter
418
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
419
* @param c The connection to add the fillter for
421
AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
427
* Returns the filter handle for use with ap_add_input_filter_handle.
429
* @param name The filter name to look up
431
AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name);
434
* Add a filter to the current request. Filters are added in a FIFO manner.
435
* The first filter added will be the first filter called.
436
* @param name The name of the filter to add
437
* @param ctx Context data to set in the filter
438
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
439
* @param c The connection to add this filter for
440
* @note If adding a connection-level output filter (i.e. where the type
441
* is >= AP_FTYPE_CONNECTION) during processing of a request, the request
442
* object r must be passed in to ensure the filter chains are modified
443
* correctly. f->r will still be initialized as NULL in the new filter.
445
AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
446
request_rec *r, conn_rec *c);
449
* Variant of ap_add_output_filter() that accepts a registered filter handle
450
* (as returned by ap_register_output_filter()) rather than a filter name
452
* @param f The filter handle to add
453
* @param ctx Context data to set in the filter
454
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
455
* @param c The connection to add the filter for
456
* @note If adding a connection-level output filter (i.e. where the type
457
* is >= AP_FTYPE_CONNECTION) during processing of a request, the request
458
* object r must be passed in to ensure the filter chains are modified
459
* correctly. f->r will still be initialized as NULL in the new filter.
461
AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
467
* Returns the filter handle for use with ap_add_output_filter_handle.
469
* @param name The filter name to look up
471
AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name);
474
* Remove an input filter from either the request or connection stack
475
* it is associated with.
476
* @param f The filter to remove
479
AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f);
482
* Remove an output filter from either the request or connection stack
483
* it is associated with.
484
* @param f The filter to remove
487
AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
489
/* The next two filters are for abstraction purposes only. They could be
490
* done away with, but that would require that we break modules if we ever
491
* want to change our filter registration method. The basic idea, is that
492
* all filters have a place to store data, the ctx pointer. These functions
493
* fill out that pointer with a bucket brigade, and retrieve that data on
494
* the next call. The nice thing about these functions, is that they
495
* automatically concatenate the bucket brigades together for you. This means
496
* that if you have already stored a brigade in the filters ctx pointer, then
497
* when you add more it will be tacked onto the end of that brigade. When
498
* you retrieve data, if you pass in a bucket brigade to the get function,
499
* it will append the current brigade onto the one that you are retrieving.
503
* prepare a bucket brigade to be setaside. If a different brigade was
504
* set-aside earlier, then the two brigades are concatenated together.
505
* @param f The current filter
506
* @param save_to The brigade that was previously set-aside. Regardless, the
507
* new bucket brigade is returned in this location.
508
* @param b The bucket brigade to save aside. This brigade is always empty
510
* @param p Ensure that all data in the brigade lives as long as this pool
512
AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f,
513
apr_bucket_brigade **save_to,
514
apr_bucket_brigade **b, apr_pool_t *p);
517
* Flush function for apr_brigade_* calls. This calls ap_pass_brigade
518
* to flush the brigade if the brigade buffer overflows.
519
* @param bb The brigade to flush
520
* @param ctx The filter to pass the brigade to
521
* @note this function has nothing to do with FLUSH buckets. It is simply
522
* a way to flush content out of a brigade and down a filter stack.
524
AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb,
528
* Flush the current brigade down the filter stack.
529
* @param f The filter we are passing to
530
* @param bb The brigade to flush
532
AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
535
* Write a buffer for the current filter, buffering if possible.
536
* @param f the filter we are writing to
537
* @param bb The brigade to buffer into
538
* @param data The data to write
539
* @param nbyte The number of bytes in the data
541
#define ap_fwrite(f, bb, data, nbyte) \
542
apr_brigade_write(bb, ap_filter_flush, f, data, nbyte)
545
* Write a buffer for the current filter, buffering if possible.
546
* @param f the filter we are writing to
547
* @param bb The brigade to buffer into
548
* @param str The string to write
550
#define ap_fputs(f, bb, str) \
551
apr_brigade_puts(bb, ap_filter_flush, f, str)
554
* Write a character for the current filter, buffering if possible.
555
* @param f the filter we are writing to
556
* @param bb The brigade to buffer into
557
* @param c The character to write
559
#define ap_fputc(f, bb, c) \
560
apr_brigade_putc(bb, ap_filter_flush, f, c)
563
* Write an unspecified number of strings to the current filter
564
* @param f the filter we are writing to
565
* @param bb The brigade to buffer into
566
* @param ... The strings to write
568
AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
569
apr_bucket_brigade *bb,
574
* Output data to the filter in printf format
575
* @param f the filter we are writing to
576
* @param bb The brigade to buffer into
577
* @param fmt The format string
578
* @param ... The arguments to use to fill out the format string
580
AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
581
apr_bucket_brigade *bb,
584
__attribute__((format(printf,3,4)));
587
* set protocol requirements for an output content filter
588
* (only works with AP_FTYPE_RESOURCE and AP_FTYPE_CONTENT_SET)
589
* @param f the filter in question
590
* @param proto_flags Logical OR of AP_FILTER_PROTO_* bits
592
AP_DECLARE(void) ap_filter_protocol(ap_filter_t* f, unsigned int proto_flags);
594
/** Filter changes contents (so invalidating checksums/etc) */
595
#define AP_FILTER_PROTO_CHANGE 0x1
597
/** Filter changes length of contents (so invalidating content-length/etc) */
598
#define AP_FILTER_PROTO_CHANGE_LENGTH 0x2
600
/** Filter requires complete input and can't work on byteranges */
601
#define AP_FILTER_PROTO_NO_BYTERANGE 0x4
603
/** Filter should not run in a proxy */
604
#define AP_FILTER_PROTO_NO_PROXY 0x8
606
/** Filter makes output non-cacheable */
607
#define AP_FILTER_PROTO_NO_CACHE 0x10
609
/** Filter is incompatible with "Cache-Control: no-transform" */
610
#define AP_FILTER_PROTO_TRANSFORM 0x20
620
#endif /* !AP_FILTER_H */