Merge pull request ceph#54587 from cbodley/wip-45736

rgw: add headers to guide cache update in 304 response

Reviewed-by: Yuval Lifshitz <[email protected]>

Author: cbodley

src/rgw/driver/rados/rgw_rados.cc

@@ -6689,6 +6689,10 @@ int RGWRados::Object::Read::prepare(optional_yield y, const DoutPrefixProvider *
     }
   }
 
+  if (params.lastmod) {
+    *params.lastmod = astate->mtime;
+  }
+
   /* Convert all times go GMT to make them compatible */
   if (conds.mod_ptr || conds.unmod_ptr) {
     obj_time_weight src_weight;
@@ -6739,9 +6743,6 @@ int RGWRados::Object::Read::prepare(optional_yield y, const DoutPrefixProvider *
   if (params.obj_size) {
     *params.obj_size = astate->size;
   }
-  if (params.lastmod) {
-    *params.lastmod = astate->mtime;
-  }
   if (params.epoch) {
     *params.epoch = astate->epoch;
   }

src/rgw/rgw_op.cc

@@ -2275,12 +2275,12 @@ void RGWGetObj::execute(optional_yield y)
   }
 
   op_ret = read_op->prepare(s->yield, this);
-  if (op_ret < 0)
-    goto done_err;
   version_id = s->object->get_instance();
   s->obj_size = s->object->get_obj_size();
   attrs = s->object->get_attrs();
   multipart_parts_count = read_op->params.parts_count;
+  if (op_ret < 0)
+    goto done_err;
 
   /* STAT ops don't need data, and do no i/o */
   if (get_type() == RGW_OP_STAT_OBJ) {

src/rgw/rgw_rest_s3.cc

@@ -579,6 +579,20 @@ int RGWGetObj_ObjStore_S3::send_response_data(bufferlist& bl, off_t bl_ofs,
   }
 
   if (op_ret == -ERR_NOT_MODIFIED) {
+      dump_last_modified(s, lastmod);
+
+      auto iter = attrs.find(RGW_ATTR_ETAG);
+      if (iter != attrs.end())
+        dump_etag(s, iter->second.to_str());
+
+      iter = attrs.find(RGW_ATTR_CACHE_CONTROL);
+      if (iter != attrs.end())
+        dump_header(s, rgw_to_http_attrs[RGW_ATTR_CACHE_CONTROL], iter->second);
+
+      iter = attrs.find(RGW_ATTR_EXPIRES);
+      if (iter != attrs.end())
+        dump_header(s, rgw_to_http_attrs[RGW_ATTR_EXPIRES], iter->second);
+
       end_header(s, this);
   } else {
       if (!content_type)