/* 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.
*/
/*
* mod_buffer.c --- Buffer the input and output filter stacks, collapse
* many small buckets into fewer large buckets.
*/
#include "apr.h"
#include "apr_strings.h"
#include "apr_buckets.h"
#include "apr_lib.h"
#include "ap_config.h"
#include "util_filter.h"
#include "httpd.h"
#include "http_config.h"
#include "http_log.h"
#include "http_request.h"
static const char bufferFilterName[] = "BUFFER";
module AP_MODULE_DECLARE_DATA buffer_module;
#define DEFAULT_BUFFER_SIZE 128*1024
typedef struct buffer_conf {
apr_off_t size; /* size of the buffer */
int size_set; /* has the size been set */
} buffer_conf;
typedef struct buffer_ctx {
apr_bucket_brigade *bb;
apr_bucket_brigade *tmp;
buffer_conf *conf;
apr_off_t remaining;
int seen_eos;
} buffer_ctx;
/**
* Buffer buckets being written to the output filter stack.
*/
static apr_status_t buffer_out_filter(ap_filter_t *f, apr_bucket_brigade *bb) {
apr_bucket *e;
request_rec *r = f->r;
buffer_ctx *ctx = f->ctx;
apr_status_t rv = APR_SUCCESS;
int move = 0;
/* first time in? create a context */
if (!ctx) {
/* buffering won't work on subrequests, it would be nice if
* it did. Within subrequests, we have no EOS to check for,
* so we don't know when to flush the buffer to the network
*/
if (f->r->main) {
ap_remove_output_filter(f);
return ap_pass_brigade(f->next, bb);
}
ctx = f->ctx = apr_pcalloc(r->pool, sizeof(*ctx));
ctx->bb = apr_brigade_create(r->pool, f->c->bucket_alloc);
ctx->conf = ap_get_module_config(f->r->per_dir_config, &buffer_module);
}
/* Do nothing if asked to filter nothing. */
if (APR_BRIGADE_EMPTY(bb)) {
return ap_pass_brigade(f->next, bb);
}
/* Empty buffer means we can potentially optimise below */
if (APR_BRIGADE_EMPTY(ctx->bb)) {
move = 1;
}
while (APR_SUCCESS == rv && !APR_BRIGADE_EMPTY(bb)) {
const char *data;
apr_off_t len;
apr_size_t size;
e = APR_BRIGADE_FIRST(bb);
/* EOS means we are done. */
if (APR_BUCKET_IS_EOS(e)) {
/* should we add an etag? */
/* pass the EOS across */
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
/* pass what we have down the chain */
rv = ap_pass_brigade(f->next, ctx->bb);
continue;
}
/* A flush takes precedence over buffering */
if (APR_BUCKET_IS_FLUSH(e)) {
/* pass the flush bucket across */
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
/* pass what we have down the chain */
rv = ap_pass_brigade(f->next, ctx->bb);
continue;
}
/* metadata buckets are preserved as is */
if (APR_BUCKET_IS_METADATA(e)) {
/*
* Remove meta data bucket from old brigade and insert into the
* new.
*/
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
continue;
}
/* is our buffer full?
* If so, send what we have down the filter chain. If the buffer
* gets full, we can no longer compute a content length.
*/
apr_brigade_length(ctx->bb, 1, &len);
if (len > ctx->conf->size) {
/* pass what we have down the chain */
rv = ap_pass_brigade(f->next, ctx->bb);
if (rv) {
/* should break out of the loop, since our write to the client
* failed in some way. */
continue;
}
}
/* at this point we are ready to buffer.
* Buffering takes advantage of an optimisation in the handling of
* bucket brigades. Heap buckets are always created at a fixed
* size, regardless of the size of the data placed into them.
* The apr_brigade_write() call will first try and pack the data
* into any free space in the most recent heap bucket, before
* allocating a new bucket if necessary.
*/
if (APR_SUCCESS == (rv = apr_bucket_read(e, &data, &size,
APR_BLOCK_READ))) {
/* further optimisation: if the buckets are already heap
* buckets, and the buckets stay exactly APR_BUCKET_BUFF_SIZE
* long (as they would be if we were reading bits of a
* large bucket), then move the buckets instead of copying
* them.
*/
if (move && APR_BUCKET_IS_HEAP(e)) {
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
if (APR_BUCKET_BUFF_SIZE != size) {
move = 0;
}
} else {
apr_brigade_write(ctx->bb, NULL, NULL, data, size);
apr_bucket_delete(e);
}
}
}
return rv;
}
/**
* Buffer buckets being read from the input filter stack.
*/
static apr_status_t buffer_in_filter(ap_filter_t *f, apr_bucket_brigade *bb,
ap_input_mode_t mode, apr_read_type_e block, apr_off_t readbytes) {
apr_bucket *e, *after;
apr_status_t rv;
buffer_ctx *ctx = f->ctx;
/* buffer on main requests only */
if (!ap_is_initial_req(f->r)) {
ap_remove_input_filter(f);
return ap_get_brigade(f->next, bb, mode, block, readbytes);
}
/* first time in? create a context */
if (!ctx) {
ctx = f->ctx = apr_pcalloc(f->r->pool, sizeof(*ctx));
ctx->bb = apr_brigade_create(f->r->pool, f->c->bucket_alloc);
ctx->tmp = apr_brigade_create(f->r->pool, f->c->bucket_alloc);
ctx->conf = ap_get_module_config(f->r->per_dir_config, &buffer_module);
}
/* just get out of the way of things we don't want. */
if (mode != AP_MODE_READBYTES) {
return ap_get_brigade(f->next, bb, mode, block, readbytes);
}
/* if our buffer is empty, read off the network until the buffer is full */
if (APR_BRIGADE_EMPTY(ctx->bb)) {
int seen_flush = 0;
ctx->remaining = ctx->conf->size;
while (!ctx->seen_eos && !seen_flush && ctx->remaining > 0) {
const char *data;
apr_size_t size = 0;
if (APR_BRIGADE_EMPTY(ctx->tmp)) {
rv = ap_get_brigade(f->next, ctx->tmp, mode, block,
ctx->remaining);
/* if an error was received, bail out now. If the error is
* EAGAIN and we have not yet seen an EOS, we will definitely
* be called again, at which point we will send our buffered
* data. Instead of sending EAGAIN, some filters return an
* empty brigade instead when data is not yet available. In
* this case, pass through the APR_SUCCESS and emulate the
* underlying filter.
*/
if (rv != APR_SUCCESS || APR_BRIGADE_EMPTY(ctx->tmp)) {
return rv;
}
}
do {
e = APR_BRIGADE_FIRST(ctx->tmp);
/* if we see an EOS, we are done */
if (APR_BUCKET_IS_EOS(e)) {
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
ctx->seen_eos = 1;
break;
}
/* flush buckets clear the buffer */
if (APR_BUCKET_IS_FLUSH(e)) {
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
seen_flush = 1;
break;
}
/* pass metadata buckets through */
if (APR_BUCKET_IS_METADATA(e)) {
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
continue;
}
/* read the bucket in, pack it into the buffer */
if (APR_SUCCESS == (rv = apr_bucket_read(e, &data, &size,
APR_BLOCK_READ))) {
apr_brigade_write(ctx->bb, NULL, NULL, data, size);
ctx->remaining -= size;
apr_bucket_delete(e);
} else {
return rv;
}
} while (!APR_BRIGADE_EMPTY(ctx->tmp));
}
}
/* give the caller the data they asked for from the buffer */
apr_brigade_partition(ctx->bb, readbytes, &after);
e = APR_BRIGADE_FIRST(ctx->bb);
while (e != after) {
if (APR_BUCKET_IS_EOS(e)) {
/* last bucket read, step out of the way */
ap_remove_input_filter(f);
}
APR_BUCKET_REMOVE(e);
APR_BRIGADE_INSERT_TAIL(bb, e);
e = APR_BRIGADE_FIRST(ctx->bb);
}
return APR_SUCCESS;
}
static void *create_buffer_config(apr_pool_t *p, char *dummy) {
buffer_conf *new = (buffer_conf *) apr_pcalloc(p, sizeof(buffer_conf));
new->size_set = 0; /* unset */
new->size = DEFAULT_BUFFER_SIZE; /* default size */
return (void *) new;
}
static void *merge_buffer_config(apr_pool_t *p, void *basev, void *addv) {
buffer_conf *new = (buffer_conf *) apr_pcalloc(p, sizeof(buffer_conf));
buffer_conf *add = (buffer_conf *) addv;
buffer_conf *base = (buffer_conf *) basev;
new->size = (add->size_set == 0) ? base->size : add->size;
new->size_set = add->size_set || base->size_set;
return new;
}
static const char *set_buffer_size(cmd_parms *cmd, void *dconf, const char *arg) {
buffer_conf *conf = dconf;
if (APR_SUCCESS != apr_strtoff(&(conf->size), arg, NULL, 10) || conf->size
<= 0) {
return "BufferSize must be a size in bytes, and greater than zero";
}
conf->size_set = 1;
return NULL;
}
static const command_rec buffer_cmds[] = { AP_INIT_TAKE1("BufferSize",
set_buffer_size, NULL, ACCESS_CONF,
"Maximum size of the buffer used by the buffer filter"), { NULL } };
static void register_hooks(apr_pool_t *p) {
ap_register_output_filter(bufferFilterName, buffer_out_filter, NULL,
AP_FTYPE_CONTENT_SET);
ap_register_input_filter(bufferFilterName, buffer_in_filter, NULL,
AP_FTYPE_CONTENT_SET);
}
AP_DECLARE_MODULE(buffer) = {
STANDARD20_MODULE_STUFF,
create_buffer_config, /* create per-directory config structure */
merge_buffer_config, /* merge per-directory config structures */
NULL, /* create per-server config structure */
NULL, /* merge per-server config structures */
buffer_cmds, /* command apr_table_t */
register_hooks /* register hooks */
};