sd_login: Be slightly more verbose with type names.

9 files changed, 107 insertions, 91 deletions

diff --git a/sd_login/.gitignore b/sd_login/.gitignore
index 721c03c..e94b335 100644
--- a/sd_login/.gitignore
+++ b/sd_login/.gitignore
@@ -1 +1 @@
-/systemd_pid.go
+/systemd_process.go
diff --git a/sd_login/Makefile b/sd_login/Makefile
index 98f0746..bed4104 100644
--- a/sd_login/Makefile
+++ b/sd_login/Makefile
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-files.src.gen += systemd_pid.go
+files.src.gen += systemd_process.go
 
 files.generate: $(files.src.gen)
 maintainer-clean:
diff --git a/sd_login/doc.go b/sd_login/doc.go
index 33c31be..00e7250 100644
--- a/sd_login/doc.go
+++ b/sd_login/doc.go
@@ -17,14 +17,16 @@
 // Package sd_login introspects session and login information from
 // systemd, logind, and machined.
 //
-// There are 5 basic object types that these three system services manage.
+// There are 5 basic object types that these three system services
+// manage and are introspected by this package.
 //
 // The machine manager maintains a list of "machines":
 //
 //  1. machine: A local container or virtual machine
 //
 // The host system, and machines hosted on it, may each run their own
-// login manager, which keeps track of seats, sessions, and users:
+// login manager, which keeps track of "seats", "sessions", and
+// "users":
 //
 //  2. seat: A set of hardware devices for a workspace; i.e. a screen
 //     and keyboard
@@ -36,10 +38,10 @@
 //     more sessions
 //
 // Finally, sessions and users can be used to group together
-// processes, which are kept track of by cgroup manager:
+// "processes", which are kept track of by cgroup manager:
 //
-//  5. pid: A process may belong to a session, or directly to a user
-//     if it is not part of a session.  This "belonging" is separate
-//     accounting by the login manager; it is NOT the same as the
-//     EUID/RUID.
+//  5. process: A process may belong to a session, or directly to a
+//     user if it is not part of a session.  This "belonging" is
+//     separate accounting by the cgroup manager; it is NOT the same
+//     as the EUID/RUID.
 package sd_login
diff --git a/sd_login/logind_seat.go b/sd_login/logind_seat.go
index a62effc..4879950 100644
--- a/sd_login/logind_seat.go
+++ b/sd_login/logind_seat.go
@@ -21,33 +21,46 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// A Seat represents a set of hardware devices for a workspace; i.e. a
+// A SeatName represents a set of hardware devices for a workspace; i.e. a
 // screen and keyboard.
 //
-// Multiple sessions may be associated with a seat, but only one
-// session may be active on a seat at a time.
-type Seat string
+// Multiple sessions may be associated with a seat (if
+// seat.CanMultiSession()), but only one session may be active on a
+// seat at a time.
+type SeatName string
+
+// A SessionNameWithUID is a just a SessionName with a User ID already
+// associated with it, so that a separate lookup for GetUser isn't
+// necessary.
+type SessionNameWithUID struct {
+	SessionName
+	User UserID
+}
+
+func (sess SessionNameWithUID) GetUser() (UserID, error) {
+	return sess.User, nil
+}
 
-func (seat Seat) isValid() bool {
+func (seat SeatName) isValid() bool {
 	return valid_filename(string(seat))
 }
 
 // GetSeats returns a list of all currently available local seats.
-func GetSeats() ([]Seat, error) {
+func GetSeats() ([]SeatName, error) {
 	strs, err := get_files_in_directory("/run/systemd/seats/")
 	if err != nil {
 		return nil, err
 	}
-	seats := make([]Seat, len(strs))
+	seats := make([]SeatName, len(strs))
 	for i := range strs {
-		seats[i] = Seat(strs[i])
+		seats[i] = SeatName(strs[i])
 	}
 	return seats, nil
 }
 
 // GetActive returns which session is currently active on this seat,
 // or nil if there is no currently active session.
-func (seat Seat) GetActive() (sess AnnotatedSession, err error) {
+func (seat SeatName) GetActive() (sess SessionNameWithUID, err error) {
 	if !seat.isValid() {
 		err = unix.EINVAL
 		return
@@ -71,15 +84,15 @@ func (seat Seat) GetActive() (sess AnnotatedSession, err error) {
 	if err != nil {
 		return
 	}
-	sess.Session = Session(strName)
-	sess.User = User(intUid)
+	sess.SessionName = SessionName(strName)
+	sess.User = UserID(intUid)
 
 	return
 }
 
 // GetSessions returns a list of all sessions associated with the
 // seat, whether they are active or not.
-func (seat Seat) GetSessions() ([]AnnotatedSession, error) {
+func (seat SeatName) GetSessions() ([]SessionNameWithUID, error) {
 	if !seat.isValid() {
 		return nil, unix.EINVAL
 	}
@@ -102,20 +115,20 @@ func (seat Seat) GetSessions() ([]AnnotatedSession, error) {
 	if len(arySessions) != len(aryUids) {
 		return nil, unix.ENXIO
 	}
-	ret := make([]AnnotatedSession, len(arySessions))
+	ret := make([]SessionNameWithUID, len(arySessions))
 	for i := 0; i < len(arySessions); i++ {
 		uid, err := strconv.Atoi(aryUids[i])
 		if err != nil {
 			return nil, err
 		}
-		ret[i].Session = Session(arySessions[i])
-		ret[i].User = User(uid)
+		ret[i].SessionName = SessionName(arySessions[i])
+		ret[i].User = UserID(uid)
 	}
 
 	return ret, nil
 }
 
-func (seat Seat) can(cap string) (bool, error) {
+func (seat SeatName) can(cap string) (bool, error) {
 	if !seat.isValid() {
 		return false, unix.EINVAL
 	}
@@ -126,14 +139,21 @@ func (seat Seat) can(cap string) (bool, error) {
 	return parse_boolean(env["CAN_"+cap])
 }
 
-func (seat Seat) CanMultiSession() (bool, error) {
+// CanMultiSession returns whether this seat is capable of
+// multi-session, i.e. login sessions in parallel (with only one being
+// active at a time).
+func (seat SeatName) CanMultiSession() (bool, error) {
 	return seat.can("MULTI_SESSION")
 }
 
-func (seat Seat) CanTTY() (bool, error) {
+// CanTTY returns whether this seat provides TTY functionality,
+// i.e. is useful as a text console.
+func (seat SeatName) CanTTY() (bool, error) {
 	return seat.can("TTY")
 }
 
-func (seat Seat) CanGraphical() (bool, error) {
+// CanGraphical returns whether this seat provides graphics
+// functionality, i.e. is useful as a graphics display.
+func (seat SeatName) CanGraphical() (bool, error) {
 	return seat.can("GRAPHICAL")
 }
diff --git a/sd_login/logind_session.go b/sd_login/logind_session.go
index e692426..5c2c5ca 100644
--- a/sd_login/logind_session.go
+++ b/sd_login/logind_session.go
@@ -14,63 +14,58 @@
 
 package sd_login
 
-type Session string
-
-type AnnotatedSession struct {
-	Session
-	User User
-}
-
-func (sess AnnotatedSession) GetUser() (User, error) {
-	return sess.User, nil
-}
+// A SessionName represents a login session.
+type SessionName string
 
 type SessionState int
 
 const (
+	// logged in, in background
 	SessionOnline SessionState = iota
+
+	// logged in, in foreground
 	SessionActive
+
+	// nominally logged out, but some processes belonging to it
+	// are still around.
 	SessionClosing
 )
 
-func GetSessions() ([]Session, error) {
+func GetSessions() ([]SessionName, error) {
 	strs, err := get_files_in_directory("/run/systemd/sessions/")
 	if err != nil {
 		return nil, err
 	}
-	sessions := make([]Session, len(strs))
+	sessions := make([]SessionName, len(strs))
 	for i := range strs {
-		sessions[i] = Session(strs[i])
+		sessions[i] = SessionName(strs[i])
 	}
 	return sessions, nil
 }
 
-func (sess Session) IsActive() bool {
-	state, err := sess.GetState()
-	return err == nil && state == SessionActive
-}
-func (sess Session) IsRemote() bool
-func (sess Session) GetState() (SessionState, error)
-func (sess Session) GetUser() (User, error)
-func (sess Session) GetSeat() (Seat, error)
+func (sess SessionName) IsActive() (bool, error)
+func (sess SessionName) IsRemote() (bool, error)
+func (sess SessionName) GetState() (SessionState, error)
+func (sess SessionName) GetUser() (UserID, error)
+func (sess SessionName) GetSeat() (SeatName, error)
 
 // PAM
-func (sess Session) GetService() (string, error)
+func (sess SessionName) GetService() (string, error)
 
 // tty, x11, wayland, mir, unspecified
-func (sess Session) GetType() (string, error)
+func (sess SessionName) GetType() (string, error)
 
 // user, greeter, lock-screen
-func (sess Session) GetClass() (string, error)
+func (sess SessionName) GetClass() (string, error)
 
 // GNOME, KDE, systemd-console
-func (sess Session) GetDesktop() (string, error)
+func (sess SessionName) GetDesktop() (string, error)
 
 // X11 DISPLAY
-func (sess Session) GetDisplay() (string, error)
-func (sess Session) GetRemoteHost() (string, error)
+func (sess SessionName) GetDisplay() (string, error)
+func (sess SessionName) GetRemoteHost() (string, error)
 
 // PAM
-func (sess Session) GetRemoteUser() (string, error)
-func (sess Session) GetTTY() (string, error)
-func (sess Session) GetVT() (uint, error)
+func (sess SessionName) GetRemoteUser() (string, error)
+func (sess SessionName) GetTTY() (string, error)
+func (sess SessionName) GetVT() (uint, error)
diff --git a/sd_login/logind_user.go b/sd_login/logind_user.go
index 81a5418..8d20d4b 100644
--- a/sd_login/logind_user.go
+++ b/sd_login/logind_user.go
@@ -18,7 +18,7 @@ import (
 	"strconv"
 )
 
-type User int
+type UserID int
 
 type UserState int
 
@@ -32,26 +32,26 @@ const (
 
 // GetUsers returns a list of all users who currently have login
 // sessions.
-func GetUsers() ([]User, error) {
+func GetUsers() ([]UserID, error) {
 	strs, err := get_files_in_directory("/run/systemd/users/")
 	if err != nil {
 		return nil, err
 	}
-	var users []User
+	var users []UserID
 	for _, uid_str := range strs {
 		uid, err := strconv.Atoi(uid_str)
 		if err != nil {
 			continue
 		}
-		users = append(users, User(uid))
+		users = append(users, UserID(uid))
 	}
 	return users, nil
 }
 
-func (uid User) IsOnSeat(seat Seat, requireActive bool) bool
-func (uid User) GetState() (UserState, error)
+func (uid UserID) IsOnSeat(seat SeatName, requireActive bool) bool
+func (uid UserID) GetState() (UserState, error)
 
 // primary session
-func (uid User) GetDisplay() (Session, error)
-func (uid User) GetSessions(requireActive bool) ([]Session, error)
-func (uid User) GetSeats(requireActive bool) ([]Seat, error)
+func (uid UserID) GetDisplay() (SessionName, error)
+func (uid UserID) GetSessions(requireActive bool) ([]SessionName, error)
+func (uid UserID) GetSeats(requireActive bool) ([]SeatName, error)
diff --git a/sd_login/machined_machine.go b/sd_login/machined_machine.go
index d89eaad..f9fb771 100644
--- a/sd_login/machined_machine.go
+++ b/sd_login/machined_machine.go
@@ -21,12 +21,11 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// A Machine is a name representing a locally running container or
+// A MachineName is a name representing a locally running container or
 // virtual machine that is registerd with (systemd-)machined.
-type Machine string
+type MachineName string
 
-// isValid returns whether the Machine name is valid.
-func (m Machine) isValid() bool {
+func (m MachineName) isValid() bool {
 	if len(m) > host_name_max {
 		// Note that Linux HOST_NAME_MAX is 64, but DNS allows
 		// 255, so names from DNS might be invalid.
@@ -59,18 +58,18 @@ func (m Machine) isValid() bool {
 
 // GetMachines returns a list of currently running containers/virtual
 // machines.
-func GetMachines() ([]Machine, error) {
+func GetMachines() ([]MachineName, error) {
 	strs, err := get_files_in_directory("/run/systemd/machines/")
 	if err != nil {
 		return nil, err
 	}
-	var machines []Machine
+	var machines []MachineName
 	for _, str := range strs {
-		machine := Machine(str)
+		machine := MachineName(str)
 		if strings.HasPrefix(str, "unit:") || machine.isValid() {
 			continue
 		}
-		machines = append(machines, Machine(str))
+		machines = append(machines, machine)
 	}
 	return machines, nil
 }
@@ -78,7 +77,7 @@ func GetMachines() ([]Machine, error) {
 // GetClass returns the class of a locally running machine.  The class
 // is either "vm" or "container", depending on if the machine is an
 // virtual machine or a container.
-func (m Machine) GetClass() (string, error) {
+func (m MachineName) GetClass() (string, error) {
 	if !m.isValid() {
 		return "", unix.EINVAL
 	}
@@ -96,7 +95,7 @@ func (m Machine) GetClass() (string, error) {
 
 // GetIfIndices returns the numeric indices of the network interfaces
 // on the host that are pointing toward this machine.
-func (m Machine) GetIfIndices() ([]int, error) {
+func (m MachineName) GetIfIndices() ([]int, error) {
 	if !m.isValid() {
 		return nil, unix.EINVAL
 	}
diff --git a/sd_login/systemd_cgroup.go b/sd_login/systemd_cgroup.go
index 0ceef37..12d5ade 100644
--- a/sd_login/systemd_cgroup.go
+++ b/sd_login/systemd_cgroup.go
@@ -2,9 +2,9 @@ package sd_login
 
 type _Cgroup interface {
 	MustSkipSystemPrefix() _Cgroup
-	GetSession() Session
-	GetOwnerUser() User
-	GetMachine() Machine
+	GetSession() SessionName
+	GetOwnerUser() UserID
+	GetMachine() MachineName
 
 	GetUserSlice() string
 	GetUserUnit() string
@@ -13,4 +13,4 @@ type _Cgroup interface {
 	GetUnit() string
 }
 
-func (pid PID) getCgroup() (_Cgroup, error)
+func (pid ProcessID) getCgroup() (_Cgroup, error)
diff --git a/sd_login/systemd_pid.go.gen b/sd_login/systemd_process.go.gen
index 8d5e5fb..cadbfc6 100755
--- a/sd_login/systemd_pid.go.gen
+++ b/sd_login/systemd_process.go.gen
@@ -27,29 +27,29 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// A PID represents a process.
+// A ProcessID represents a process.
 //
-// As a special case, PID(0) refers to the current process.
-type PID int
+// As a special case, ProcessID(0) refers to the current process.
+type ProcessID int
 
-func (pid PID) isValid() bool {
+func (pid ProcessID) isValid() bool {
 	return pid >= 0
 }
 
-func GetPeer(conn *net.UnixConn) (PID, error) {
+func GetPeer(conn *net.UnixConn) (ProcessID, error) {
 	ucred, err := getpeercred(conn)
 	if err != nil {
 		return -1, err
 	}
-	return PID(ucred.Pid), nil
+	return ProcessID(ucred.Pid), nil
 }
 
 EOF
 
 	data=(
-		'GetSession Session'
-		'GetOwnerUser User'
-		'GetMachine Machine'
+		'GetSession SessionName'
+		'GetOwnerUser UserID'
+		'GetMachine MachineName'
 
 		'GetUnit string'
 		'GetUserUnit string'
@@ -60,7 +60,7 @@ EOF
 		read Func Type <<<"$item"
 		cat <<EOF
 
-func (pid PID) ${Func}() (v ${Type}, err error) {
+func (pid ProcessID) ${Func}() (v ${Type}, err error) {
 	if !pid.isValid() {
 		err = unix.EINVAL
 		return