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util_filter.h
/* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * @file util_filter.h * @brief Apache filter library */ #ifndef AP_FILTER_H #define AP_FILTER_H #include "apr.h" #include "apr_buckets.h" #include "httpd.h" #if APR_HAVE_STDARG_H #include <stdarg.h> #endif #ifdef __cplusplus extern "C" { #endif /** * @brief input filtering modes */ typedef enum { /** The filter should return at most readbytes data. */ AP_MODE_READBYTES, /** The filter should return at most one line of CRLF data. * (If a potential line is too long or no CRLF is found, the * filter may return partial data). */ AP_MODE_GETLINE, /** The filter should implicitly eat any CRLF pairs that it sees. */ AP_MODE_EATCRLF, /** The filter read should be treated as speculative and any returned * data should be stored for later retrieval in another mode. */ AP_MODE_SPECULATIVE, /** The filter read should be exhaustive and read until it can not * read any more. * Use this mode with extreme caution. */ AP_MODE_EXHAUSTIVE, /** The filter should initialize the connection if needed, * NNTP or FTP over SSL for example. */ AP_MODE_INIT } ap_input_mode_t; /** * @defgroup APACHE_CORE_FILTER Filter Chain * @ingroup APACHE_CORE * * Filters operate using a "chaining" mechanism. The filters are chained * together into a sequence. When output is generated, it is passed through * each of the filters on this chain, until it reaches the end (or "bottom") * and is placed onto the network. * * The top of the chain, the code generating the output, is typically called * a "content generator." The content generator's output is fed into the * filter chain using the standard Apache output mechanisms: ap_rputs(), * ap_rprintf(), ap_rwrite(), etc. * * Each filter is defined by a callback. This callback takes the output from * the previous filter (or the content generator if there is no previous * filter), operates on it, and passes the result to the next filter in the * chain. This pass-off is performed using the ap_fc_* functions, such as * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc. * * When content generation is complete, the system will pass an "end of * stream" marker into the filter chain. The filters will use this to flush * out any internal state and to detect incomplete syntax (for example, an * unterminated SSI directive). * * @{ */ /* forward declare the filter type */ typedef struct ap_filter_t ap_filter_t; /** * @name Filter callbacks * * This function type is used for filter callbacks. It will be passed a * pointer to "this" filter, and a "bucket brigade" containing the content * to be filtered. * * In filter->ctx, the callback will find its context. This context is * provided here, so that a filter may be installed multiple times, each * receiving its own per-install context pointer. * * Callbacks are associated with a filter definition, which is specified * by name. See ap_register_input_filter() and ap_register_output_filter() * for setting the association between a name for a filter and its * associated callback (and other information). * * If the initialization function argument passed to the registration * functions is non-NULL, it will be called iff the filter is in the input * or output filter chains and before any data is generated to allow the * filter to prepare for processing. * * The bucket brigade always belongs to the caller, but the filter * is free to use the buckets within it as it sees fit. Normally, * the brigade will be returned empty. Buckets *may not* be retained * between successive calls to the filter unless they have been * "set aside" with a call apr_bucket_setaside. Typically this will * be done with ap_save_brigade(). Buckets removed from the brigade * become the responsibility of the filter, which must arrange for * them to be deleted, either by doing so directly or by inserting * them in a brigade which will subsequently be destroyed. * * For the input and output filters, the return value of a filter should be * an APR status value. For the init function, the return value should * be an HTTP error code or OK if it was successful. * * @ingroup filter * @{ */ typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f, apr_bucket_brigade *b); typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f, apr_bucket_brigade *b, ap_input_mode_t mode, apr_read_type_e block, apr_off_t readbytes); typedef int (*ap_init_filter_func)(ap_filter_t *f); typedef union ap_filter_func { ap_out_filter_func out_func; ap_in_filter_func in_func; } ap_filter_func; /** @} */ /** * Filters have different types/classifications. These are used to group * and sort the filters to properly sequence their operation. * * The types have a particular sort order, which allows us to insert them * into the filter chain in a determistic order. Within a particular grouping, * the ordering is equivalent to the order of calls to ap_add_*_filter(). */ typedef enum { /** These filters are used to alter the content that is passed through * them. Examples are SSI or PHP. */ AP_FTYPE_RESOURCE = 10, /** These filters are used to alter the content as a whole, but after all * AP_FTYPE_RESOURCE filters are executed. These filters should not * change the content-type. An example is deflate. */ AP_FTYPE_CONTENT_SET = 20, /** These filters are used to handle the protocol between server and * client. Examples are HTTP and POP. */ AP_FTYPE_PROTOCOL = 30, /** These filters implement transport encodings (e.g., chunking). */ AP_FTYPE_TRANSCODE = 40, /** These filters will alter the content, but in ways that are * more strongly associated with the connection. Examples are * splitting an HTTP connection into multiple requests and * buffering HTTP responses across multiple requests. * * It is important to note that these types of filters are not * allowed in a sub-request. A sub-request's output can certainly * be filtered by ::AP_FTYPE_RESOURCE filters, but all of the "final * processing" is determined by the main request. */ AP_FTYPE_CONNECTION = 50, /** These filters don't alter the content. They are responsible for * sending/receiving data to/from the client. */ AP_FTYPE_NETWORK = 60 } ap_filter_type; /** * This is the request-time context structure for an installed filter (in * the output filter chain). It provides the callback to use for filtering, * the request this filter is associated with (which is important when * an output chain also includes sub-request filters), the context for this * installed filter, and the filter ordering/chaining fields. * * Filter callbacks are free to use ->ctx as they please, to store context * during the filter process. Generally, this is superior over associating * the state directly with the request. A callback should not change any of * the other fields. */ typedef struct ap_filter_rec_t ap_filter_rec_t; typedef struct ap_filter_provider_t ap_filter_provider_t; /** * @brief This structure is used for recording information about the * registered filters. It associates a name with the filter's callback * and filter type. * * At the moment, these are simply linked in a chain, so a ->next pointer * is available. * * It is used for any filter that can be inserted in the filter chain. * This may be either a httpd-2.0 filter or a mod_filter harness. * In the latter case it contains dispatch, provider and protocol information. * In the former case, the new fields (from dispatch) are ignored. */ struct ap_filter_rec_t { /** The registered name for this filter */ const char *name; /** The function to call when this filter is invoked. */ ap_filter_func filter_func; /** The function to call directly before the handlers are invoked * for a request. The init function is called once directly * before running the handlers for a request or subrequest. The * init function is never called for a connection filter (with * ftype >= AP_FTYPE_CONNECTION). Any use of this function for * filters for protocols other than HTTP is specified by the * module supported that protocol. */ ap_init_filter_func filter_init_func; /** The next filter_rec in the list */ struct ap_filter_rec_t *next; /** Providers for this filter */ ap_filter_provider_t *providers; /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION. * An AP_FTYPE_CONTENT filter modifies the data based on information * found in the content. An AP_FTYPE_CONNECTION filter modifies the * data based on the type of connection. */ ap_filter_type ftype; /** Trace level for this filter */ int debug; /** Protocol flags for this filter */ unsigned int proto_flags; }; /** * @brief The representation of a filter chain. * * Each request has a list * of these structures which are called in turn to filter the data. Sub * requests get an exact copy of the main requests filter chain. */ struct ap_filter_t { /** The internal representation of this filter. This includes * the filter's name, type, and the actual function pointer. */ ap_filter_rec_t *frec; /** A place to store any data associated with the current filter */ void *ctx; /** The next filter in the chain */ ap_filter_t *next; /** The request_rec associated with the current filter. If a sub-request * adds filters, then the sub-request is the request associated with the * filter. */ request_rec *r; /** The conn_rec associated with the current filter. This is analogous * to the request_rec, except that it is used for connection filters. */ conn_rec *c; }; /** * Get the current bucket brigade from the next filter on the filter * stack. The filter returns an apr_status_t value. If the bottom-most * filter doesn't read from the network, then ::AP_NOBODY_READ is returned. * The bucket brigade will be empty when there is nothing left to get. * @param filter The next filter in the chain * @param bucket The current bucket brigade. The original brigade passed * to ap_get_brigade() must be empty. * @param mode The way in which the data should be read * @param block How the operations should be performed * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ * @param readbytes How many bytes to read from the next filter. */ AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket, ap_input_mode_t mode, apr_read_type_e block, apr_off_t readbytes); /** * Pass the current bucket brigade down to the next filter on the filter * stack. The filter returns an apr_status_t value. If the bottom-most * filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned. * @param filter The next filter in the chain * @param bucket The current bucket brigade * * @remark Ownership of the brigade is retained by the caller. On return, * the contents of the brigade are UNDEFINED, and the caller must * either call apr_brigade_cleanup or apr_brigade_destroy on * the brigade. */ AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket); /** * Pass the current bucket brigade down to the next filter on the filter * stack checking for filter errors. The filter returns an apr_status_t value. * Returns ::OK if the brigade is successfully passed * ::AP_FILTER_ERROR on a filter error * ::HTTP_INTERNAL_SERVER_ERROR on all other errors * @param r The request rec * @param bucket The current bucket brigade * @param fmt The format string. If NULL defaults to "ap_pass_brigade returned" * @param ... The arguments to use to fill out the format string * @remark Ownership of the brigade is retained by the caller. On return, * the contents of the brigade are UNDEFINED, and the caller must * either call apr_brigade_cleanup or apr_brigade_destroy on * the brigade. */ AP_DECLARE(apr_status_t) ap_pass_brigade_fchk(request_rec *r, apr_bucket_brigade *bucket, const char *fmt, ...) __attribute__((format(printf,3,4))); /** * This function is used to register an input filter with the system. * After this registration is performed, then a filter may be added * into the filter chain by using ap_add_input_filter() and simply * specifying the name. * * @param name The name to attach to the filter function * @param filter_func The filter function to name * @param filter_init The function to call before the filter handlers are invoked * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT_SET or * ::AP_FTYPE_CONNECTION * @see add_input_filter() */ AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name, ap_in_filter_func filter_func, ap_init_filter_func filter_init, ap_filter_type ftype); /** @deprecated @see ap_register_output_filter_protocol */ AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name, ap_out_filter_func filter_func, ap_init_filter_func filter_init, ap_filter_type ftype); /* For httpd-?.? I suggest replacing the above with #define ap_register_output_filter(name,ffunc,init,ftype) \ ap_register_output_filter_protocol(name,ffunc,init,ftype,0) */ /** * This function is used to register an output filter with the system. * After this registration is performed, then a filter may be added * directly to the filter chain by using ap_add_output_filter() and * simply specifying the name, or as a provider under mod_filter. * * @param name The name to attach to the filter function * @param filter_func The filter function to name * @param filter_init The function to call before the filter handlers * are invoked * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT_SET or * ::AP_FTYPE_CONNECTION * @param proto_flags Protocol flags: logical OR of AP_FILTER_PROTO_* bits * @return the filter rec * @see ap_add_output_filter() */ AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter_protocol( const char *name, ap_out_filter_func filter_func, ap_init_filter_func filter_init, ap_filter_type ftype, unsigned int proto_flags); /** * Adds a named filter into the filter chain on the specified request record. * The filter will be installed with the specified context pointer. * * Filters added in this way will always be placed at the end of the filters * that have the same type (thus, the filters have the same order as the * calls to ap_add_filter). If the current filter chain contains filters * from another request, then this filter will be added before those other * filters. * * To re-iterate that last comment. This function is building a FIFO * list of filters. Take note of that when adding your filter to the chain. * * @param name The name of the filter to add * @param ctx Context data to provide to the filter * @param r The request to add this filter for (or NULL if it isn't associated with a request) * @param c The connection to add the fillter for */ AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx, request_rec *r, conn_rec *c); /** * Variant of ap_add_input_filter() that accepts a registered filter handle * (as returned by ap_register_input_filter()) rather than a filter name * * @param f The filter handle to add * @param ctx Context data to provide to the filter * @param r The request to add this filter for (or NULL if it isn't associated with a request) * @param c The connection to add the fillter for */ AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f, void *ctx, request_rec *r, conn_rec *c); /** * Returns the filter handle for use with ap_add_input_filter_handle. * * @param name The filter name to look up */ AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name); /** * Add a filter to the current request. Filters are added in a FIFO manner. * The first filter added will be the first filter called. * @param name The name of the filter to add * @param ctx Context data to set in the filter * @param r The request to add this filter for (or NULL if it isn't associated with a request) * @param c The connection to add this filter for * @note If adding a connection-level output filter (i.e. where the type * is >= AP_FTYPE_CONNECTION) during processing of a request, the request * object r must be passed in to ensure the filter chains are modified * correctly. f->r will still be initialized as NULL in the new filter. */ AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx, request_rec *r, conn_rec *c); /** * Variant of ap_add_output_filter() that accepts a registered filter handle * (as returned by ap_register_output_filter()) rather than a filter name * * @param f The filter handle to add * @param ctx Context data to set in the filter * @param r The request to add this filter for (or NULL if it isn't associated with a request) * @param c The connection to add the filter for * @note If adding a connection-level output filter (i.e. where the type * is >= AP_FTYPE_CONNECTION) during processing of a request, the request * object r must be passed in to ensure the filter chains are modified * correctly. f->r will still be initialized as NULL in the new filter. */ AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f, void *ctx, request_rec *r, conn_rec *c); /** * Returns the filter handle for use with ap_add_output_filter_handle. * * @param name The filter name to look up */ AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name); /** * Remove an input filter from either the request or connection stack * it is associated with. * @param f The filter to remove */ AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f); /** * Remove an output filter from either the request or connection stack * it is associated with. * @param f The filter to remove */ AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f); /** * Remove an input filter from either the request or connection stack * it is associated with. * @param next The filter stack to search * @param handle The filter handle (name) to remove * @return APR_SUCCESS on removal or error */ AP_DECLARE(apr_status_t) ap_remove_input_filter_byhandle(ap_filter_t *next, const char *handle); /** * Remove an output filter from either the request or connection stack * it is associated with. * @param next The filter stack to search * @param handle The filter handle (name) to remove * @return APR_SUCCESS on removal or error */ AP_DECLARE(apr_status_t) ap_remove_output_filter_byhandle(ap_filter_t *next, const char *handle); /* The next two filters are for abstraction purposes only. They could be * done away with, but that would require that we break modules if we ever * want to change our filter registration method. The basic idea, is that * all filters have a place to store data, the ctx pointer. These functions * fill out that pointer with a bucket brigade, and retrieve that data on * the next call. The nice thing about these functions, is that they * automatically concatenate the bucket brigades together for you. This means * that if you have already stored a brigade in the filters ctx pointer, then * when you add more it will be tacked onto the end of that brigade. When * you retrieve data, if you pass in a bucket brigade to the get function, * it will append the current brigade onto the one that you are retrieving. */ /** * prepare a bucket brigade to be setaside. If a different brigade was * set-aside earlier, then the two brigades are concatenated together. * @param f The current filter * @param save_to The brigade that was previously set-aside. Regardless, the * new bucket brigade is returned in this location. * @param b The bucket brigade to save aside. This brigade is always empty * on return * @param p Ensure that all data in the brigade lives as long as this pool */ AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f, apr_bucket_brigade **save_to, apr_bucket_brigade **b, apr_pool_t *p); /** * Flush function for apr_brigade_* calls. This calls ap_pass_brigade * to flush the brigade if the brigade buffer overflows. * @param bb The brigade to flush * @param ctx The filter to pass the brigade to * @note this function has nothing to do with FLUSH buckets. It is simply * a way to flush content out of a brigade and down a filter stack. */ AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb, void *ctx); /** * Flush the current brigade down the filter stack. * @param f The filter we are passing to * @param bb The brigade to flush */ AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb); /** * Write a buffer for the current filter, buffering if possible. * @param f the filter we are writing to * @param bb The brigade to buffer into * @param data The data to write * @param nbyte The number of bytes in the data */ #define ap_fwrite(f, bb, data, nbyte) \ apr_brigade_write(bb, ap_filter_flush, f, data, nbyte) /** * Write a buffer for the current filter, buffering if possible. * @param f the filter we are writing to * @param bb The brigade to buffer into * @param str The string to write */ #define ap_fputs(f, bb, str) \ apr_brigade_write(bb, ap_filter_flush, f, str, strlen(str)) /** * Write a character for the current filter, buffering if possible. * @param f the filter we are writing to * @param bb The brigade to buffer into * @param c The character to write */ #define ap_fputc(f, bb, c) \ apr_brigade_putc(bb, ap_filter_flush, f, c) /** * Write an unspecified number of strings to the current filter * @param f the filter we are writing to * @param bb The brigade to buffer into * @param ... The strings to write */ AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f, apr_bucket_brigade *bb, ...) AP_FN_ATTR_SENTINEL; /** * Output data to the filter in printf format * @param f the filter we are writing to * @param bb The brigade to buffer into * @param fmt The format string * @param ... The arguments to use to fill out the format string */ AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f, apr_bucket_brigade *bb, const char *fmt, ...) __attribute__((format(printf,3,4))); /** * set protocol requirements for an output content filter * (only works with AP_FTYPE_RESOURCE and AP_FTYPE_CONTENT_SET) * @param f the filter in question * @param proto_flags Logical OR of AP_FILTER_PROTO_* bits */ AP_DECLARE(void) ap_filter_protocol(ap_filter_t* f, unsigned int proto_flags); /** Filter changes contents (so invalidating checksums/etc) */ #define AP_FILTER_PROTO_CHANGE 0x1 /** Filter changes length of contents (so invalidating content-length/etc) */ #define AP_FILTER_PROTO_CHANGE_LENGTH 0x2 /** Filter requires complete input and can't work on byteranges */ #define AP_FILTER_PROTO_NO_BYTERANGE 0x4 /** Filter should not run in a proxy */ #define AP_FILTER_PROTO_NO_PROXY 0x8 /** Filter makes output non-cacheable */ #define AP_FILTER_PROTO_NO_CACHE 0x10 /** Filter is incompatible with "Cache-Control: no-transform" */ #define AP_FILTER_PROTO_TRANSFORM 0x20 /** * @} */ #ifdef __cplusplus } #endif #endif /* !AP_FILTER_H */
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