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MEDIUM: cache: Add support for 'If-None-Match' request header

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Partial support of conditional HTTP requests. This commit adds the
support of the 'If-None-Match' header (see RFC 7232#3.2).
When a client specifies a list of ETags through one or more
'If-None-Match' headers, they are all compared to the one that might have
been stored in the corresponding http cache entry until one of them
matches.
If a match happens, a specific "304 Not Modified" response is
sent instead of the cached data. This response has all the stored
headers but no other data (see RFC 7232#4.1). Otherwise, the whole cached data
is sent.
Although unlikely in a GET/HEAD request, the "If-None-Match: *" syntax is
valid and also receives a "304 Not Modified" response (RFC 7434#4.3.2).

This resolves a part of GitHub issue #821.
This commit is contained in:
Remi Tricot-Le Breton 2020-10-22 10:40:05 +02:00 committed by William Lallemand
parent dbb65b5a7a
commit 6cb10384a3
2 changed files with 68 additions and 2 deletions
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3
include/haproxy/applet-t.h
View File

@ -112,6 +112,9 @@ struct appctx {
unsigned int sent; /* The number of bytes already sent for this cache entry. */
unsigned int offset; /* start offset of remaining data relative to beginning of the next block */
unsigned int rem_data; /* Remaining bytes for the last data block (HTX only, 0 means process next block) */
unsigned int send_notmodified:1; /* In case of conditional request, we might want to send a "304 Not Modified"
* response instead of the stored data. */
unsigned int unused:31;
struct shared_block *next; /* The next block of data to be sent for this cache entry. */
} cache;
/* all entries below are used by various CLI commands, please

67
src/cache.c
View File

@ -933,8 +933,14 @@ static void http_cache_io_handler(struct appctx *appctx)
!htx_cache_add_age_hdr(appctx, res_htx))
goto error;
/* Skip response body for HEAD requests */
if (si_strm(si)->txn->meth == HTTP_METH_HEAD)
/* In case of a conditional request, we might want to send a
* "304 Not Modified" response instead of the stored data. */
if (appctx->ctx.cache.send_notmodified)
http_replace_res_status(res_htx, ist("304"), ist("Not Modified"));
/* Skip response body for HEAD requests or in case of "304 Not
* Modified" response. */
if (si_strm(si)->txn->meth == HTTP_METH_HEAD || appctx->ctx.cache.send_notmodified)
appctx->st0 = HTX_CACHE_EOM;
else
appctx->st0 = HTX_CACHE_DATA;
@ -1121,6 +1127,61 @@ int sha1_hosturi(struct stream *s)
return 1;
}
/* Looks for "If-None-Match" headers in the request and compares their value
* with the one that might have been stored in the cache_entry. If any of them
* matches, a "304 Not Modified" response should be sent instead of the cached
* data.
* Although unlikely in a GET/HEAD request, the "If-None-Match: *" syntax is
* valid and should receive a "304 Not Modified" response (RFC 7434#4.3.2).
* Returns 1 if "304 Not Modified" should be sent, 0 otherwise.
*/
static int should_send_notmodified_response(struct cache *cache, struct htx *htx,
struct cache_entry *entry)
{
int retval = 0;
struct http_hdr_ctx ctx = { .blk = NULL };
struct ist cache_entry_etag = IST_NULL;
struct buffer *etag_buffer = NULL;
if (entry->etag_length == 0)
return 0;
/* If we find a "If-None-Match" header in the request, rebuild the
* cache_entry's ETag in order to perform comparisons. */
/* There could be multiple "if-none-match" header lines. */
while (http_find_header(htx, ist("if-none-match"), &ctx, 0)) {
/* A '*' matches everything. */
if (isteq(ctx.value, ist("*")) != 0) {
retval = 1;
break;
}
/* Rebuild the stored ETag. */
if (etag_buffer == NULL) {
etag_buffer = get_trash_chunk();
if (shctx_row_data_get(shctx_ptr(cache), block_ptr(entry),
(unsigned char*)b_orig(etag_buffer),
entry->etag_offset, entry->etag_length) == 0) {
cache_entry_etag = ist2(b_orig(etag_buffer), entry->etag_length);
} else {
/* We could not rebuild the ETag in one go, we
* won't send a "304 Not Modified" response. */
break;
}
}
if (http_compare_etags(cache_entry_etag, ctx.value) == 1) {
retval = 1;
break;
}
}
return retval;
}
enum act_return http_action_req_cache_use(struct act_rule *rule, struct proxy *px,
struct session *sess, struct stream *s, int flags)
{
@ -1165,6 +1226,8 @@ enum act_return http_action_req_cache_use(struct act_rule *rule, struct proxy *p
appctx->ctx.cache.entry = res;
appctx->ctx.cache.next = NULL;
appctx->ctx.cache.sent = 0;
appctx->ctx.cache.send_notmodified =
should_send_notmodified_response(cache, htxbuf(&s->req.buf), res);
if (px == strm_fe(s))
_HA_ATOMIC_ADD(&px->fe_counters.p.http.cache_hits, 1);