最近好像很多公司都在开始做OpenBMC，真的好夯，所以今天来聊聊OpenBMC的Redfish怎么快速上手， 如果对redfish没有很熟的话，可以先看"认识Redfish"里面讲解的概念

10分钟认识下一代数据中心基础设施管理标准 - 红鱼(Redfish)_yeiris的博客-CSDN博客这几年BMC领域中最受瞩目的两件事情就是Redfish的出现和OpenBMC的崛起，所以今天我想用10分钟来聊聊下一代数据中心基础设施管理标准 - 红鱼(Redfish)红鱼的诞生Redfish 是在2015年由DMTF(Distributed Management Task Force) 这个组织开始着手建立的伺服器管理标准，官方的描述是A standard, Redfish is designed to deliver simple and secure management for https://blog.csdn.net/yeiris/article/details/122755165

Code 在哪里?

Redfish的Code 是放在bmcweb这一包里面

GitHub - openbmc/bmcweb: A do everything Redfish, KVM, GUI, and DBus webserver for OpenBMChttps://github.com/openbmc/bmcweb目前OpenBMC的Web打算采用前后端分离的方式，后端是Redfish，前端是webui-vue，所以我猜bmcweb这个名字是这样来的

如何开始? 该先看哪只程式码?

RedfishService

在src\webserver_main.cpp 中将RedfishServices加到router

RedfishServices (redfish-core\include\redfish.hpp)里面有很多sub router

這些subrouter定義的程式碼都在"redfish-core\lib\"資料夾底下，以requestAccountServiceRoutes為例，定義在account_service.hpp中 

使用者权限 (privileges)

根据Redfish.md里面的描述，User Role有三种可以选择 Administrator, Operator 和 ReadOnly

这边还是以AccountService的redfish::privileges::getAccountService为范例，在redfish-core\include\registries\privilege_registry.hpp可看到

// AccountService
const static auto& getAccountService = privilegeSetLogin;

其中privilegeSetLogin 是Login 權限，所以Administrator, Operator 和 ReadOnly User都可以GET /redfish/v1/AccountService/

namespace redfish::privileges
{
// clang-format off
const std::array<Privileges, 1> privilegeSetLogin = {{{"Login"}
}};
const std::array<Privileges, 1> privilegeSetConfigureComponents = {{{"ConfigureComponents"}
}};
const std::array<Privileges, 1> privilegeSetConfigureUsers = {{{"ConfigureUsers"}
}};
const std::array<Privileges, 1> privilegeSetConfigureManager = {{{"ConfigureManager"}
}};
const std::array<Privileges, 2> privilegeSetConfigureManagerOrConfigureComponents = {{{"ConfigureManager"},{"ConfigureComponents"}
}};
const std::array<Privileges, 2> privilegeSetConfigureManagerOrConfigureSelf = {{{"ConfigureManager"},{"ConfigureSelf"}
}};
const std::array<Privileges, 3> privilegeSetConfigureManagerOrConfigureUsersOrConfigureSelf = {{{"ConfigureManager"},{"ConfigureUsers"},{"ConfigureSelf"}
}};
const std::array<Privileges, 2> privilegeSetLoginOrNoAuth = {{{"Login"},{}
}};

redfish-core\lib

这个资料夹中存放了所有support 的redfish resource的程式码，可以先看自己要研究的API，例如常見的ComputerServices

//redfish-core\lib\systems.hpp
BMCWEB_ROUTE(app, "/redfish/v1/Systems/system/").privileges(redfish::privileges::getComputerSystem).methods(boost::beast::http::verb::get)([](const crow::Request&,const std::shared_ptr<bmcweb::AsyncResp>& asyncResp) {}

资料操作皆来自Dbus

什么是Dbus

OpenBMC提供了介绍影片，我觉得讲得很完整 sdbusplus & phosphor-dbus-interface - YouTube

OpenBMC是由很多个daemon所组成的，像是ipmid, fwupd, fscd等，dbus可以想像成他们的共享资料夹，所以当我们要修改资料或是拿取资料的时候，就去dbus相对位置拿取就可以了，底下是我在维基看到的图片，从图片中可以感受到有了Dbus之后，Daemon间的沟通变得简单有条理

Dbus的组成有三个元素：

Service - A daemon attached to the dbus and providing objects.

root@romulus:~# busctl
xyz.openbmc_project.State.BMC

Object Paths – A tree, like a file system, of paths to objects.(对象路径的树，如文件系统)

root@romulus:~# busctl  tree xyz.openbmc_project.State.BMC
└─/xyz└─/xyz/openbmc_project└─/xyz/openbmc_project/state└─/xyz/openbmc_project/state/bmc0

Interface – The ‘class’ of an object. Objects support multiple inheritance.(对象的“class”。 对象支持多重继承)

• Property – Store values. Some can be written to (存储值。有些可以改写)
• Method – Make method calls.(进行方法调用)
• Signal – Inform other process about an event. (将事件通知其他进程)

root@romulus:~# busctl introspect xyz.openbmc_project.State.BMC /xyz/openbmc_project/state/bmc0
NAME                                TYPE			SIGNATURE       RESULT/VALUE                                 FLAGS
xyz.openbmc_project.State.BMC       interface		-				-                                            -
.CurrentBMCState                    property        s               "xyz.openbmc_project.State.BMC.BMCState…     emits-change writable
.LastRebootTime                     property        t               1619401752000                                emits-change writable
.RequestedBMCTransition             property		s               "xyz.openbmc_project.State.BMC.Transiti…     emits-change writable

所以如果Redfish 想要取得BMC的LastRebootTime,那他就要下get-property指令

get-property SERVICE   OBJECT   INTERFACE   PROPERTY... 

busctl get-property xyz.openbmc_project.State.BMC /xyz/openbmc_project/state/bmc0 xyz.openbmc_project.State.BMC LastRebootTime

那在程式码实作就是如下，可以看到他在get-property 的function中分别带入service, object ,interface和property

//redfish-core\lib\managers.hpp
inline voidmanagerGetLastResetTime(const std::shared_ptr<bmcweb::AsyncResp>& aResp)
{BMCWEB_LOG_DEBUG << "Getting Manager Last Reset Time";sdbusplus::asio::getProperty<uint64_t>(*crow::connections::systemBus, "xyz.openbmc_project.State.BMC","/xyz/openbmc_project/state/bmc0", "xyz.openbmc_project.State.BMC","LastRebootTime",[aResp](const boost::system::error_code ec,const uint64_t lastResetTime) {if (ec){BMCWEB_LOG_DEBUG << "D-BUS response error " << ec;return;}// LastRebootTime is epoch time, in milliseconds// https://github.com/openbmc/phosphor-dbus-interfaces/blob/7f9a128eb9296e926422ddc312c148b625890bb6/xyz/openbmc_project/State/BMC.interface.yaml#L19uint64_t lastResetTimeStamp = lastResetTime / 1000;// Convert to ISO 8601 standardaResp->res.jsonValue["LastResetTime"] =crow::utility::getDateTimeUint(lastResetTimeStamp);});
}

回调函数(Callback function)

刚刚知道了redfish 怎么从dbus获取资料之后，就会想到，那如果我要更改或新增资料(patch, post)，这样要怎么做到dbus完成后才回传Status code，在redfish中大量用到callback function , 这样可以达到到dbus完成后再进行下一步

这边我们先用AccountService/Accounts的patch Method为例，再确定要patch 的 property value(UserName, Password, RoleId..)没问题之后，它便呼叫了dbus function，等到dbus完成之后再执行callback function

//sdbusplus/include/sdbusplus/asio/connection.hpp
void async_method_call(MessageHandler&& handler, const std::string& service,const std::string& objpath,const std::string& interf, const std::string& method,const InputArgs&... a)

//redfish-core\lib\account_service.hpp
BMCWEB_ROUTE(app, "/redfish/v1/AccountService/Accounts/<str>/").privileges({{"ConfigureUsers"}, {"ConfigureSelf"}}).methods(boost::beast::http::verb::patch)([](const crow::Request& req,const std::shared_ptr<bmcweb::AsyncResp>& asyncResp,const std::string& username) -> void {//verify value, 先省略掉crow::connections::systemBus->async_method_call(//callback function start[asyncResp, username, password(std::move(password)),roleId(std::move(roleId)), enabled,newUser{std::string(*newUserName)},locked](const boost::system::error_code ec,sdbusplus::message::message& m) {if (ec){userErrorMessageHandler(m.get_error(), asyncResp,newUser, username);return;}updateUserProperties(asyncResp, newUser, password,enabled, roleId, locked);} //callback function end,"xyz.openbmc_project.User.Manager","/xyz/openbmc_project/user","xyz.openbmc_project.User.Manager", "RenameUser", username,*newUserName);});

那如果要设定很多项呢? 你就会发现有巢状回调函数的出现，这样可以执行完一个method后再call 下一个mthod

crow::connections::systemBus->async_method_call([asyncResp](const boost::system::error_code ec,sdbusplus::message::message& m) {if (ec){return;}crow::connections::systemBus->async_method_call([asyncResp](const boost::system::error_code ec,sdbusplus::message::message& m) {if (ec){return;}crow::connections::systemBus->async_method_call([asyncResp](const boost::system::error_code ec,sdbusplus::message::message& m) {if (ec){return;}updateUserProperties(asyncResp, newUser, password,enabled, roleId, locked);},"Service 3","object path3","Interface", "method", value, value');},"Service 2","object path2","Interface", "method", value, value');},"Service 1","object path","Interface", "method", value, value');

如果掌握以上几点再去看bmcweb的code，会发现其实也没这么复杂