MINOR: cache: Process the If-Modified-Since header in conditional requests
If a client sends a conditional request containing an If-Modified-Since
header (and no If-None-Match header), we try to compare the date with
the one stored in the cache entry (coming either from a Last-Modified
head, or a Date header, or corresponding to the first response's
reception time). If the request's date is earlier than the stored one,
we send a "304 Not Modified" response back. Otherwise, the stored is sent
(through a 200 OK response).
This resolves GitHub issue #821.
diff --git a/src/cache.c b/src/cache.c
index 29de7cd..a98ca66 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -1183,7 +1183,13 @@
* 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).
+ * valid and should receive a "304 Not Modified" response (RFC 7234#4.3.2).
+ *
+ * If no "If-None-Match" header was found, look for an "If-Modified-Since"
+ * header and compare its value (date) to the one stored in the cache_entry.
+ * If the request's date is later than the cached one, we also send a
+ * "304 Not Modified" response (see RFCs 7232#3.3 and 7234#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,
@@ -1194,14 +1200,16 @@
struct http_hdr_ctx ctx = { .blk = NULL };
struct ist cache_entry_etag = IST_NULL;
struct buffer *etag_buffer = NULL;
+ int if_none_match_found = 0;
- if (entry->etag_length == 0)
- return 0;
+ struct tm tm = {};
+ time_t if_modified_since = 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. */
+ * 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)) {
+ if_none_match_found = 1;
/* A '*' matches everything. */
if (isteq(ctx.value, ist("*")) != 0) {
@@ -1209,6 +1217,10 @@
break;
}
+ /* No need to rebuild an etag if none was stored in the cache. */
+ if (entry->etag_length == 0)
+ break;
+
/* Rebuild the stored ETag. */
if (etag_buffer == NULL) {
etag_buffer = get_trash_chunk();
@@ -1230,6 +1242,23 @@
}
}
+ /* If the request did not contain an "If-None-Match" header, we look for
+ * an "If-Modified-Since" header (see RFC 7232#3.3). */
+ if (retval == 0 && if_none_match_found == 0) {
+ ctx.blk = NULL;
+ if (http_find_header(htx, ist("if-modified-since"), &ctx, 1)) {
+ if (parse_http_date(istptr(ctx.value), istlen(ctx.value), &tm)) {
+ if_modified_since = my_timegm(&tm);
+
+ /* We send a "304 Not Modified" response if the
+ * entry's last modified date is earlier than
+ * the one found in the "If-Modified-Since"
+ * header. */
+ retval = (entry->last_modified <= if_modified_since);
+ }
+ }
+ }
+
return retval;
}