MEDIUM: cache: Save body size of cached objects and track it on delivery

We now save the body size of cached objets in the cache entry strucutre. In
addition, the cache applet tracks the body part already sent.

This will be mandatory to add support of endpoint-to-endpoint
fast-forwarding in the cache applet.

src/cache.c

@@ -73,10 +73,12 @@ struct cache_appctx {
 	struct cache_tree *cache_tree;
 	struct cache_entry *entry;       /* Entry to be sent from cache. */
 	unsigned int sent;               /* The number of bytes already sent for this cache entry. */
+	unsigned int data_sent;           /* The number of bytes of the payload 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;
+	/* 4 bytes hole here */
 	struct shared_block *next;       /* The next block of data to be sent for this cache entry. */
 };
 
@@ -193,7 +195,7 @@ struct cache_entry {
 	unsigned int latest_validation;     /* latest validation date */
 	unsigned int expire;      /* expiration date (wall clock time) */
 	unsigned int age;         /* Origin server "Age" header value */
-
+	unsigned int body_size;         /* Size of the body */
 	int refcount;
 
 	struct eb32_node eb;     /* ebtree node used to hold the cache object */
@@ -751,6 +753,7 @@ cache_store_http_payload(struct stream *s, struct filter *filter, struct http_ms
 	struct htx_blk *blk;
 	struct shared_block *fb;
 	struct htx_ret htxret;
+	size_t data_len = 0;
 	unsigned int orig_len, to_forward;
 	int ret;
 
@@ -787,6 +790,7 @@ cache_store_http_payload(struct stream *s, struct filter *filter, struct http_ms
 				chunk_memcat(&trash, (char *)&info, sizeof(info));
 				chunk_istcat(&trash, v);
 				to_forward += v.len;
+				data_len += v.len;
 				len -= v.len;
 				break;
 
@@ -815,6 +819,7 @@ cache_store_http_payload(struct stream *s, struct filter *filter, struct http_ms
 		goto no_cache;
 	}
 
+	((struct cache_entry *)st->first_block->data)->body_size += data_len;
 	ret = shctx_row_data_append(shctx, st->first_block,
 				    (unsigned char *)b_head(&trash), b_data(&trash));
 	if (ret < 0)
@@ -1519,7 +1524,7 @@ static unsigned int htx_cache_dump_data_blk(struct appctx *appctx, struct htx *h
 	struct cache_appctx *ctx = appctx->svcctx;
 	struct cache_flt_conf *cconf = appctx->rule->arg.act.p[0];
 	struct shared_context *shctx = shctx_ptr(cconf->c.cache);
-	unsigned int max, total, rem_data;
+	unsigned int max, total, rem_data, data_len;
 	uint32_t blksz;
 
 	max = htx_get_max_blksz(htx,
@@ -1527,6 +1532,7 @@ static unsigned int htx_cache_dump_data_blk(struct appctx *appctx, struct htx *h
 	if (!max)
 		return 0;
 
+	data_len = 0;
 	rem_data = 0;
 	if (ctx->rem_data) {
 		blksz = ctx->rem_data;
@@ -1549,6 +1555,7 @@ static unsigned int htx_cache_dump_data_blk(struct appctx *appctx, struct htx *h
 		offset += sz;
 		blksz  -= sz;
 		total  += sz;
+		data_len += sz;
 		if (sz < max)
 			break;
 		if (blksz || offset == shctx->block_size) {
@@ -1560,6 +1567,7 @@ static unsigned int htx_cache_dump_data_blk(struct appctx *appctx, struct htx *h
 	ctx->offset   = offset;
 	ctx->next     = shblk;
 	ctx->sent    += total;
+	ctx->data_sent += data_len;
 	ctx->rem_data = rem_data + blksz;
 	return total;
 }
@@ -2062,7 +2070,7 @@ enum act_return http_action_req_cache_use(struct act_rule *rule, struct proxy *p
 			ctx->cache_tree = cache_tree;
 			ctx->entry = res;
 			ctx->next = NULL;
-			ctx->sent = 0;
+			ctx->sent = ctx->data_sent = 0;
 			ctx->send_notmodified =
                                 should_send_notmodified_response(cache, htxbuf(&s->req.buf), res);