copying each header to the cache, we must leave space for the string

header, also, if there are duplicate headers, then we must write the
duplicate header.

earlier in the presence of duplicates, there was a double shift at the
beginning of the copying procedure
CSTR_MOVE_HDR
CSTR_WRITE_HDR
*CSTR_MOVE_HDR*
*CSTR_MOVE_HDR*
CSTR_WRITE_HDR

tempesta_fw/cache.c

@@ -1152,23 +1152,22 @@ tfw_cache_h2_copy_hdr(TfwCacheEntry *ce, char **p, TdbVRec **trec, TfwStr *hdr,
 		return -ENOMEM;
 	}
 
-	CSTR_MOVE_HDR();
-
 	if (TFW_STR_DUP(hdr)) {
-		CSTR_WRITE_HDR(TFW_STR_DUPLICATE, hdr->nchunks);
 		CSTR_MOVE_HDR();
+		CSTR_WRITE_HDR(TFW_STR_DUPLICATE, hdr->nchunks);
 	}
 
 	TFW_STR_FOR_EACH_DUP(dup, hdr, dup_end) {
-		unsigned int prev_len = ce->hdr_len;
+		unsigned int prev_len;
 
 		if (dupl) {
 			TFW_STR_INIT(&s_nm);
 			TFW_STR_INIT(&s_val);
 			tfw_http_hdr_split(dup, &s_nm, &s_val, true);
 			st_index = dup->hpack_idx;
-			CSTR_MOVE_HDR();
 		}
+		CSTR_MOVE_HDR();
+		prev_len = ce->hdr_len;
 
 		if (st_index) {
 			if (tfw_cache_h2_copy_int(&ce->hdr_len, st_index, 0xF,