diff options
Diffstat (limited to 'modules/http2/h2_push.h')
| -rw-r--r-- | modules/http2/h2_push.h | 86 |
1 files changed, 62 insertions, 24 deletions
diff --git a/modules/http2/h2_push.h b/modules/http2/h2_push.h index bc24e68..947b73b 100644 --- a/modules/http2/h2_push.h +++ b/modules/http2/h2_push.h @@ -17,10 +17,12 @@ #ifndef __mod_h2__h2_push__ #define __mod_h2__h2_push__ +#include <http_protocol.h> + #include "h2.h" +#include "h2_headers.h" struct h2_request; -struct h2_headers; struct h2_ngheader; struct h2_session; struct h2_stream; @@ -35,6 +37,44 @@ typedef enum { H2_PUSH_DIGEST_SHA256 } h2_push_digest_type; +/******************************************************************************* + * push diary + * + * - The push diary keeps track of resources already PUSHed via HTTP/2 on this + * connection. It records a hash value from the absolute URL of the resource + * pushed. + * - Lacking openssl, + * - with openssl, it uses SHA256 to calculate the hash value, otherwise it + * falls back to apr_hashfunc_default() + * - whatever the method to generate the hash, the diary keeps a maximum of 64 + * bits per hash, limiting the memory consumption to about + * H2PushDiarySize * 8 + * bytes. Entries are sorted by most recently used and oldest entries are + * forgotten first. + * - While useful by itself to avoid duplicated PUSHes on the same connection, + * the original idea was that clients provided a 'Cache-Digest' header with + * the values of *their own* cached resources. This was described in + * <https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/> + * and some subsequent revisions that tweaked values but kept the overall idea. + * - The draft was abandoned by the IETF http-wg, as support from major clients, + * e.g. browsers, was lacking for various reasons. + * - For these reasons, mod_h2 abandoned its support for client supplied values + * but keeps the diary. It seems to provide value for applications using PUSH, + * is configurable in size and defaults to a very moderate amount of memory + * used. + * - The cache digest header is a Golomb Coded Set of hash values, but it may + * limit the amount of bits per hash value even further. For a good description + * of GCS, read here: + * <http://giovanni.bajo.it/post/47119962313/golomb-coded-sets-smaller-than-bloom-filters> + ******************************************************************************/ + + +/* + * The push diary is based on the abandoned draft + * <https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/> + * that describes how to use golomb filters. + */ + typedef struct h2_push_diary h2_push_diary; typedef void h2_push_digest_calc(h2_push_diary *diary, apr_uint64_t *phash, h2_push *push); @@ -59,14 +99,21 @@ struct h2_push_diary { * @param res the response from the server * @return array of h2_push addresses or NULL */ -apr_array_header_t *h2_push_collect(apr_pool_t *p, - const struct h2_request *req, - int push_policy, +#if AP_HAS_RESPONSE_BUCKETS +apr_array_header_t *h2_push_collect(apr_pool_t *p, + const struct h2_request *req, + apr_uint32_t push_policy, + const ap_bucket_response *res); +#else +apr_array_header_t *h2_push_collect(apr_pool_t *p, + const struct h2_request *req, + apr_uint32_t push_policy, const struct h2_headers *res); +#endif /** * Create a new push diary for the given maximum number of entries. - * + * * @param p the pool to use * @param N the max number of entries, rounded up to 2^x * @return the created diary, might be NULL of max_entries is 0 @@ -83,14 +130,21 @@ apr_array_header_t *h2_push_diary_update(struct h2_session *session, apr_array_h * Collect pushes for the given request/response pair, enter them into the * diary and return those pushes newly entered. */ -apr_array_header_t *h2_push_collect_update(struct h2_stream *stream, - const struct h2_request *req, +#if AP_HAS_RESPONSE_BUCKETS +apr_array_header_t *h2_push_collect_update(struct h2_stream *stream, + const struct h2_request *req, + const ap_bucket_response *res); +#else +apr_array_header_t *h2_push_collect_update(struct h2_stream *stream, + const struct h2_request *req, const struct h2_headers *res); +#endif + /** * Get a cache digest as described in * https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/ * from the contents of the push diary. - * + * * @param diary the diary to calculdate the digest from * @param p the pool to use * @param authority the authority to get the data for, use NULL/"*" for all @@ -101,20 +155,4 @@ apr_status_t h2_push_diary_digest_get(h2_push_diary *diary, apr_pool_t *p, int maxP, const char *authority, const char **pdata, apr_size_t *plen); -/** - * Initialize the push diary by a cache digest as described in - * https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/ - * . - * @param diary the diary to set the digest into - * @param authority the authority to set the data for - * @param data the binary cache digest - * @param len the length of the cache digest - * @return APR_EINVAL if digest was not successfully parsed - */ -apr_status_t h2_push_diary_digest_set(h2_push_diary *diary, const char *authority, - const char *data, apr_size_t len); - -apr_status_t h2_push_diary_digest64_set(h2_push_diary *diary, const char *authority, - const char *data64url, apr_pool_t *pool); - #endif /* defined(__mod_h2__h2_push__) */ |