MEDIUM: cache: Store the ETag information in the cache_entry

When sent by a server for a given resource, the ETag header is
stored in the coresponding cache entry (as any other header). So in
order to perform future ETag comparisons (for subsequent conditional
HTTP requests), we keep the length of the ETag and its offset
relative to the start of the cache_entry.
If no ETag header exists, the length and offset are zero.

diff --git a/src/cache.c b/src/cache.c
index fe213a6aae872a0a2861fa43a150960512e3bbf2..8faaa44517b22bf01e64501fe0247ceee1bfdcba 100644 (file)
--- a/src/cache.c
+++ b/src/cache.c
@@ -21,6 +21,7 @@
 #include <haproxy/errors.h>
 #include <haproxy/filters.h>
 #include <haproxy/hash.h>
+#include <haproxy/http.h>
 #include <haproxy/http_ana.h>
 #include <haproxy/http_htx.h>
 #include <haproxy/http_rules.h>
@@ -73,6 +74,10 @@ struct cache_entry {
 
        struct eb32_node eb;     /* ebtree node used to hold the cache object */
        char hash[20];
+
+       unsigned int etag_length; /* Length of the ETag value (if one was found in the response). */
+       unsigned int etag_offset; /* Offset of the ETag value in the data buffer. */
+
        unsigned char data[0];
 };
 
@@ -537,6 +542,9 @@ enum act_return http_action_store_cache(struct act_rule *rule, struct proxy *px,
        struct http_hdr_ctx ctx;
        size_t hdrs_len = 0;
        int32_t pos;
+       unsigned int etag_length = 0;
+       unsigned int etag_offset = 0;
+       struct ist header_name = IST_NULL;
 
        /* Don't cache if the response came from a cache */
        if ((obj_type(s->target) == OBJ_TYPE_APPLET) &&
@@ -609,6 +617,18 @@ enum act_return http_action_store_cache(struct act_rule *rule, struct proxy *px,
                hdrs_len += sizeof(*blk) + sz;
                chunk_memcat(&trash, (char *)&blk->info, sizeof(blk->info));
                chunk_memcat(&trash, htx_get_blk_ptr(htx, blk), sz);
+
+               /* Look for optional ETag header.
+                * We need to store the offset of the ETag value in order for
+                * future conditional requests to be able to perform ETag
+                * comparisons. */
+               if (type == HTX_BLK_HDR) {
+                       header_name = htx_get_blk_name(htx, blk);
+                       if (isteq(header_name, ist("etag"))) {
+                               etag_length = sz - istlen(header_name);
+                               etag_offset = sizeof(struct cache_entry) + b_data(&trash) - sz + istlen(header_name);
+                       }
+               }
                if (type == HTX_BLK_EOH)
                        break;
        }
@@ -642,6 +662,10 @@ enum act_return http_action_store_cache(struct act_rule *rule, struct proxy *px,
         * those headers.
         */
 
+       /* Write the ETag information in the cache_entry if needed. */
+       object->etag_length = etag_length;
+       object->etag_offset = etag_offset;
+
        /* does not need to be locked because it's in the "hot" list,
         * copy the headers */
        if (shctx_row_data_append(shctx, first, NULL, (unsigned char *)trash.area, trash.data) < 0)