lua: refactor the cgroup API

    
This is a simplification which is necessary for adding consistent
support for accessing the parent cgroup.

debian/changelog

@@ -1,6 +1,6 @@
 cm4all-qrelay (0.26) unstable; urgency=low
 
-  * lua: remove deprecated method "mail:get_cgroup()"
+  * lua: refactor the cgroup API
   * lua: close Lua file descriptors when connection is closed
   * lua: fix broken cgroup xattr access
 

doc/index.rst

@@ -75,12 +75,14 @@ The following attributes can be queried:
 
 * :samp:`gid`: The client's group id.
 
-* :samp:`cgroup`: The control group path of the client process as
-  noted in :file:`/proc/self/cgroup`,
-  e.g. :file:`/user.slice/user-1000.slice/session-42.scope`
+* :samp:`cgroup`: The control group of the client process with the
+  following attributes:
 
-* ``cgroup_xattr``: A table containing extended attributes of the
-  control group.
+  * ``path``: the cgroup path as noted in :file:`/proc/self/cgroup`,
+    e.g. :file:`/user.slice/user-1000.slice/session-42.scope`
+
+  * ``xattr``: A table containing extended attributes of the
+    control group.
 
 The following methods can access more data:
 

src/LMail.cxx

@@ -10,7 +10,7 @@
 #include "lua/Class.hxx"
 #include "lua/Error.hxx"
 #include "lua/FenvCache.hxx"
-#include "lua/io/XattrTable.hxx"
+#include "lua/io/CgroupInfo.hxx"
 #include "lua/net/SocketAddress.hxx"
 #include "uri/EmailAddress.hxx"
 #include "util/StringAPI.hxx"
@@ -314,26 +314,7 @@ IncomingMail::Index(lua_State *L)
 		if (path.empty())
 			return 0;
 
-		Lua::Push(L, path);
-		return 1;
-	} else if (StringIsEqual(name, "cgroup_xattr")) {
-		if (!HavePeerCred())
-			return 0;
-
-		const auto path = ReadProcessCgroup(GetPid());
-		if (path.empty())
-			return 0;
-
-		try {
-			const auto sys_fs_cgroup = OpenPath("/sys/fs/cgroup");
-			auto fd = OpenReadOnlyBeneath({sys_fs_cgroup, path.c_str() + 1});
-			Lua::NewXattrTable(L, std::move(fd));
-		} catch (...) {
-			Lua::RaiseCurrent(L);
-		}
-
-		// auto-close the file descriptor when the connection is closed
-		auto_close->Add(L, Lua::RelativeStackIndex{-1});
+		Lua::NewCgroupInfo(L, *auto_close, path);
 
 		// copy a reference to the fenv (our cache)
 		Lua::SetFenvCache(L, 1, name, Lua::RelativeStackIndex{-1});

src/Main.cxx

@@ -15,6 +15,7 @@
 #include "lua/PushCClosure.hxx"
 #include "lua/RunFile.hxx"
 #include "lua/io/XattrTable.hxx"
+#include "lua/io/CgroupInfo.hxx"
 #include "lua/net/SocketAddress.hxx"
 #include "lua/event/Init.hxx"
 #include "lua/pg/Init.hxx"
@@ -143,6 +144,7 @@ SetupRuntimeState(lua_State *L)
 	Lua::SetGlobal(L, "qmqp_listen", nullptr);
 
 	Lua::InitXattrTable(L);
+	Lua::RegisterCgroupInfo(L);
 
 	QmqpRelayConnection::Register(L);