Merge c1875023b9 into 2e5b0412f9

Follow-up for 2b07a3211b.

Fixes the failure found in
https://autopkgtest.ubuntu.com/results/autopkgtest-noble-upstream-systemd-ci-systemd-ci/noble/amd64/s/systemd-upstream/20241115_182040_92382@/log.gz
. Relevant logs:
```
Nov 16 02:48:36 systemd-networkd[2706]: veth99: Reconfiguring with /run/systemd/network/25-dhcp-client-ipv6-only.network.
Nov 16 02:48:36 systemd-networkd[2706]: veth99: NDISC: Started IPv6 Router Solicitation client
Nov 16 02:48:36 systemd-networkd[2706]: veth99: IPv6 Router Discovery is configured and started.
Nov 16 02:48:36 systemd-networkd[2706]: veth99: NDISC: Sent Router Solicitation, next solicitation in 3s
Nov 16 02:48:36 systemd-networkd[2706]: veth99: NDISC: Received Router Advertisement from fe80::1034:56ff:fe78:9abd: flags=0xc0(managed, other), preference=medium, lifetime=30min
Nov 16 02:48:36 systemd-networkd[2706]: veth99: NDISC: Invoking callback for 'router' event.
Nov 16 02:48:36 systemd-networkd[2706]: veth99: link_check_ready(): dynamic addressing protocols are enabled but none of them finished yet.
Nov 16 02:48:36 systemd-networkd[2706]: veth99: DHCPv6 client: Starting in Solicit mode
Nov 16 02:48:36 systemd-networkd[2706]: veth99: DHCPv6 client: State changed: stopped -> solicitation
Nov 16 02:48:36 systemd-networkd[2706]: veth99: Acquiring DHCPv6 lease on NDisc request
Nov 16 02:48:36 systemd-networkd[2706]: veth99: DHCPv6 client: Sent Solicit
Nov 16 02:48:36 systemd-networkd[2706]: veth99: DHCPv6 client: Next retransmission in 1s
Nov 16 02:48:37 systemd-networkd[2706]: veth99: DHCPv6 client: Sent Solicit
Nov 16 02:48:37 systemd-networkd[2706]: veth99: DHCPv6 client: Next retransmission in 1s
Nov 16 02:48:39 systemd-networkd[2706]: veth99: NDISC: Received Neighbor Advertisement from fe80::1034:56ff:fe78:9abd: Router=yes, Solicited=yes, Override=no
Nov 16 02:48:39 systemd-networkd[2706]: veth99: NDISC: Invoking callback for 'neighbor' event.
Nov 16 02:48:39 systemd-networkd[2706]: veth99: DHCPv6 client: Processed Reply message
Nov 16 02:48:39 systemd-networkd[2706]: veth99: DHCPv6 client: T1 expires in 50s
Nov 16 02:48:39 systemd-networkd[2706]: veth99: DHCPv6 client: T2 expires in 55s
Nov 16 02:48:39 systemd-networkd[2706]: veth99: DHCPv6 client: Valid lifetime expires in 2min
Nov 16 02:48:39 systemd-networkd[2706]: veth99: DHCPv6 client: State changed: solicitation -> bound
Nov 16 02:48:39 systemd-networkd[2706]: veth99: DHCPv6 address 2600::15/128 (valid for 1min 59s, preferred for 1min 59s)
Nov 16 02:48:41 systemd-networkd[2706]: veth99: Received updated DHCPv6 address (configured): 2600::15/128 (valid for 1min 58s, preferred for 1min 58s), flags: no-prefixroute, scope: global
Nov 16 02:48:41 systemd-networkd[2706]: veth99: DHCPv6 addresses and routes set.
Nov 16 02:48:41 systemd-networkd[2706]: veth99: link_check_ready(): IPv4LL:no DHCPv4:no DHCPv6:yes DHCP-PD:no NDisc:no
Nov 16 02:48:41 systemd-networkd[2706]: veth99: State changed: configuring -> configured
```
The interface veth99 entered the configured state after 5 seconds, but
at the same time, the `wait_online()` in the test script considered the
test failed.
The function `wait_online()` first invokes
`systemd-networkd-wait-online` with `--timeout=20`, then check setup
states of interfaces with 5 seconds timeout. So, the failure suggests
that `systemd-networkd-wait-online` finishes immediately, as the state
file was not updated when it is invoked, and thus it handles the
interface veth99 already in the configured state.

src/basic/cgroup-util.c

@@ -1418,6 +1418,26 @@ int cg_pid_get_session(pid_t pid, char **ret_session) {
         return cg_path_get_session(cgroup, ret_session);
 }
 
+int cg_pidref_get_session(const PidRef *pidref, char **ret) {
+        int r;
+
+        if (!pidref_is_set(pidref))
+                return -ESRCH;
+
+        _cleanup_free_ char *session = NULL;
+        r = cg_pid_get_session(pidref->pid, &session);
+        if (r < 0)
+                return r;
+
+        r = pidref_verify(pidref);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = TAKE_PTR(session);
+        return 0;
+}
+
 int cg_path_get_owner_uid(const char *path, uid_t *ret_uid) {
         _cleanup_free_ char *slice = NULL;
         char *start, *end;
@@ -1455,6 +1475,27 @@ int cg_pid_get_owner_uid(pid_t pid, uid_t *ret_uid) {
         return cg_path_get_owner_uid(cgroup, ret_uid);
 }
 
+int cg_pidref_get_owner_uid(const PidRef *pidref, uid_t *ret) {
+        int r;
+
+        if (!pidref_is_set(pidref))
+                return -ESRCH;
+
+        uid_t uid;
+        r = cg_pid_get_owner_uid(pidref->pid, &uid);
+        if (r < 0)
+                return r;
+
+        r = pidref_verify(pidref);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = uid;
+
+        return 0;
+}
+
 int cg_path_get_slice(const char *p, char **ret_slice) {
         const char *e = NULL;
 

src/basic/cgroup-util.h

@@ -280,7 +280,9 @@ int cg_shift_path(const char *cgroup, const char *cached_root, const char **ret_
 int cg_pid_get_path_shifted(pid_t pid, const char *cached_root, char **ret_cgroup);
 
 int cg_pid_get_session(pid_t pid, char **ret_session);
+int cg_pidref_get_session(const PidRef *pidref, char **ret_session);
 int cg_pid_get_owner_uid(pid_t pid, uid_t *ret_uid);
+int cg_pidref_get_owner_uid(const PidRef *pidref, uid_t *ret_uid);
 int cg_pid_get_unit(pid_t pid, char **ret_unit);
 int cg_pidref_get_unit(const PidRef *pidref, char **ret);
 int cg_pid_get_user_unit(pid_t pid, char **ret_unit);

src/basic/pidref.c

@@ -429,7 +429,7 @@ int pidref_wait(const PidRef *pidref, siginfo_t *ret, int options) {
         if (pidref_is_remote(pidref))
                 return -EREMOTE;
 
-        if (pidref->pid == 1 || pidref->pid == getpid_cached())
+        if (pidref->pid == 1 || pidref_is_self(pidref))
                 return -ECHILD;
 
         siginfo_t si = {};

src/basic/socket-util.c

@@ -975,6 +975,28 @@ int getpeerpidfd(int fd) {
         return pidfd;
 }
 
+int getpeerpidref(int fd, PidRef *ret) {
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        int pidfd = getpeerpidfd(fd);
+        if (pidfd < 0)  {
+                if (!ERRNO_IS_NEG_NOT_SUPPORTED(pidfd))
+                        return pidfd;
+
+                struct ucred ucred;
+                r = getpeercred(fd, &ucred);
+                if (r < 0)
+                        return r;
+
+                return pidref_set_pid(ret, ucred.pid);
+        }
+
+        return pidref_set_pidfd_consume(ret, pidfd);
+}
+
 ssize_t send_many_fds_iov_sa(
                 int transport_fd,
                 int *fds_array, size_t n_fds_array,

src/basic/socket-util.h

@@ -20,6 +20,7 @@
 #include "macro.h"
 #include "missing_network.h"
 #include "missing_socket.h"
+#include "pidref.h"
 #include "sparse-endian.h"
 
 union sockaddr_union {
@@ -154,6 +155,7 @@ int getpeercred(int fd, struct ucred *ucred);
 int getpeersec(int fd, char **ret);
 int getpeergroups(int fd, gid_t **ret);
 int getpeerpidfd(int fd);
+int getpeerpidref(int fd, PidRef *ret);
 
 ssize_t send_many_fds_iov_sa(
                 int transport_fd,

src/basic/terminal-util.c

@@ -761,26 +761,24 @@ bool tty_is_console(const char *tty) {
 }
 
 int vtnr_from_tty(const char *tty) {
-        int i, r;
+        int r;
 
         assert(tty);
 
         tty = skip_dev_prefix(tty);
 
-        if (!startswith(tty, "tty") )
+        const char *e = startswith(tty, "tty");
+        if (!e)
                 return -EINVAL;
 
-        if (!ascii_isdigit(tty[3]))
+        unsigned u;
-                return -EINVAL;
+        r = safe_atou(e, &u);
-
-        r = safe_atoi(tty+3, &i);
         if (r < 0)
                 return r;
+        if (!vtnr_is_valid(u))
+                return -ERANGE;
 
-        if (i < 0 || i > 63)
+        return (int) u;
-                return -EINVAL;
-
-        return i;
 }
 
 int resolve_dev_console(char **ret) {

src/basic/terminal-util.h

@@ -157,3 +157,7 @@ int terminal_is_pty_fd(int fd);
 
 int pty_open_peer_racefree(int fd, int mode);
 int pty_open_peer(int fd, int mode);
+
+static inline bool vtnr_is_valid(unsigned n) {
+        return n >= 1 && n <= 63;
+}

src/libsystemd/sd-bus/test-bus-peersockaddr.c

@@ -81,7 +81,7 @@ static void *server(void *p) {
                 _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
 
                 assert_se(pidref_set_pidfd_take(&pidref, pidfd) >= 0);
-                assert_se(pidref.pid == getpid_cached());
+                assert_se(pidref_is_self(&pidref));
         }
 
         const gid_t *gl = NULL;

src/libsystemd/sd-json/json-util.c

@@ -125,14 +125,13 @@ int json_dispatch_in_addr(const char *name, sd_json_variant *variant, sd_json_di
         return 0;
 }
 
-int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
+int json_dispatch_const_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
-        char **p = ASSERT_PTR(userdata);
+        const char **p = ASSERT_PTR(userdata), *path;
-        const char *path;
 
         assert(variant);
 
         if (sd_json_variant_is_null(variant)) {
-                *p = mfree(*p);
+                *p = NULL;
                 return 0;
         }
 
@@ -145,8 +144,24 @@ int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispa
         if (!path_is_absolute(path))
                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an absolute file system path.", strna(name));
 
-        if (free_and_strdup(p, path) < 0)
+        *p = path;
-                return json_log_oom(variant, flags);
+        return 0;
+}
+
+int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
+        char **s = ASSERT_PTR(userdata);
+        const char *p;
+        int r;
+
+        assert_return(variant, -EINVAL);
+
+        r = json_dispatch_const_path(name, variant, flags, &p);
+        if (r < 0)
+                return r;
+
+        r = free_and_strdup(s, p);
+        if (r < 0)
+                return json_log(variant, flags, r, "Failed to allocate path string: %m");
 
         return 0;
 }

src/libsystemd/sd-json/json-util.h

@@ -113,6 +113,7 @@ int json_dispatch_user_group_name(const char *name, sd_json_variant *variant, sd
 int json_dispatch_const_user_group_name(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_in_addr(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
+int json_dispatch_const_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_devnum(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_ifindex(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);

src/libsystemd/sd-login/sd-login.c

@@ -334,46 +334,46 @@ _public_ int sd_pidfd_get_cgroup(int pidfd, char **ret_cgroup) {
         return 0;
 }
 
-_public_ int sd_peer_get_session(int fd, char **session) {
+_public_ int sd_peer_get_session(int fd, char **ret) {
-        struct ucred ucred = UCRED_INVALID;
         int r;
 
         assert_return(fd >= 0, -EBADF);
-        assert_return(session, -EINVAL);
+        assert_return(ret, -EINVAL);
 
-        r = getpeercred(fd, &ucred);
+        _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
+        r = getpeerpidref(fd, &pidref);
         if (r < 0)
                 return r;
 
-        return cg_pid_get_session(ucred.pid, session);
+        return cg_pidref_get_session(&pidref, ret);
 }
 
-_public_ int sd_peer_get_owner_uid(int fd, uid_t *uid) {
+_public_ int sd_peer_get_owner_uid(int fd, uid_t *ret) {
-        struct ucred ucred;
         int r;
 
         assert_return(fd >= 0, -EBADF);
-        assert_return(uid, -EINVAL);
+        assert_return(ret, -EINVAL);
 
-        r = getpeercred(fd, &ucred);
+        _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
+        r = getpeerpidref(fd, &pidref);
         if (r < 0)
                 return r;
 
-        return cg_pid_get_owner_uid(ucred.pid, uid);
+        return cg_pidref_get_owner_uid(&pidref, ret);
 }
 
-_public_ int sd_peer_get_unit(int fd, char **unit) {
+_public_ int sd_peer_get_unit(int fd, char **ret) {
-        struct ucred ucred;
         int r;
 
         assert_return(fd >= 0, -EBADF);
-        assert_return(unit, -EINVAL);
+        assert_return(ret, -EINVAL);
 
-        r = getpeercred(fd, &ucred);
+        _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
+        r = getpeerpidref(fd, &pidref);
         if (r < 0)
                 return r;
 
-        return cg_pid_get_unit(ucred.pid, unit);
+        return cg_pidref_get_unit(&pidref, ret);
 }
 
 _public_ int sd_peer_get_user_unit(int fd, char **unit) {

src/libsystemd/sd-varlink/sd-varlink.c

@@ -1698,7 +1698,8 @@ _public_ int sd_varlink_get_events(sd_varlink *v) {
                 ret |= EPOLLIN;
 
         if (!v->write_disconnected &&
-            v->output_buffer_size > 0)
+            (v->output_queue ||
+             v->output_buffer_size > 0))
                 ret |= EPOLLOUT;
 
         return ret;
@@ -3218,7 +3219,13 @@ _public_ int sd_varlink_server_new(sd_varlink_server **ret, sd_varlink_server_fl
         int r;
 
         assert_return(ret, -EINVAL);
-        assert_return((flags & ~(SD_VARLINK_SERVER_ROOT_ONLY|SD_VARLINK_SERVER_MYSELF_ONLY|SD_VARLINK_SERVER_ACCOUNT_UID|SD_VARLINK_SERVER_INHERIT_USERDATA|SD_VARLINK_SERVER_INPUT_SENSITIVE)) == 0, -EINVAL);
+        assert_return((flags & ~(SD_VARLINK_SERVER_ROOT_ONLY|
+                                 SD_VARLINK_SERVER_MYSELF_ONLY|
+                                 SD_VARLINK_SERVER_ACCOUNT_UID|
+                                 SD_VARLINK_SERVER_INHERIT_USERDATA|
+                                 SD_VARLINK_SERVER_INPUT_SENSITIVE|
+                                 SD_VARLINK_SERVER_ALLOW_FD_PASSING_INPUT|
+                                 SD_VARLINK_SERVER_ALLOW_FD_PASSING_OUTPUT)) == 0, -EINVAL);
 
         s = new(sd_varlink_server, 1);
         if (!s)
@@ -3399,6 +3406,9 @@ _public_ int sd_varlink_server_add_connection_pair(
         if (asprintf(&desc, "%s-%i-%i", varlink_server_description(server), input_fd, output_fd) >= 0)
                 v->description = TAKE_PTR(desc);
 
+        (void) sd_varlink_set_allow_fd_passing_input(v, FLAGS_SET(server->flags, SD_VARLINK_SERVER_ALLOW_FD_PASSING_INPUT));
+        (void) sd_varlink_set_allow_fd_passing_output(v, FLAGS_SET(server->flags, SD_VARLINK_SERVER_ALLOW_FD_PASSING_OUTPUT));
+
         /* Link up the server and the connection, and take reference in both directions. Note that the
          * reference on the connection is left dangling. It will be dropped when the connection is closed,
          * which happens in varlink_close(), including in the event loop quit callback. */

src/login/logind-dbus.c

@@ -85,6 +85,8 @@ static int get_sender_session(
         const char *name;
         int r;
 
+        assert(m);
+
         /* Acquire the sender's session. This first checks if the sending process is inside a session itself,
          * and returns that. If not and 'consult_display' is true, this returns the display session of the
          * owning user of the caller. */
@@ -827,186 +829,18 @@ static int method_list_inhibitors(sd_bus_message *message, void *userdata, sd_bu
         return sd_bus_send(NULL, reply, NULL);
 }
 
-static int create_session(
+static int manager_choose_session_id(
-                sd_bus_message *message,
+                Manager *m,
-                void *userdata,
+                PidRef *leader,
-                sd_bus_error *error,
+                char **ret_id) {
-                uid_t uid,
+
-                pid_t leader_pid,
+        assert(m);
-                int leader_pidfd,
+        assert(pidref_is_set(leader));
-                const char *service,
+        assert(ret_id);
-                const char *type,
-                const char *class,
-                const char *desktop,
-                const char *cseat,
-                uint32_t vtnr,
-                const char *tty,
-                const char *display,
-                int remote,
-                const char *remote_user,
-                const char *remote_host,
-                uint64_t flags) {
 
-        _cleanup_(pidref_done) PidRef leader = PIDREF_NULL;
-        Manager *m = ASSERT_PTR(userdata);
         _cleanup_free_ char *id = NULL;
-        Session *session = NULL;
         uint32_t audit_id = 0;
-        User *user = NULL;
+        (void) audit_session_from_pid(leader, &audit_id);
-        Seat *seat = NULL;
-        SessionType t;
-        SessionClass c;
-        int r;
-
-        assert(message);
-
-        if (!uid_is_valid(uid))
-                return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid UID");
-
-        if (flags != 0)
-                return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Flags must be zero.");
-
-        if (leader_pidfd >= 0)
-                r = pidref_set_pidfd(&leader, leader_pidfd);
-        else if (leader_pid == 0)
-                r = bus_query_sender_pidref(message, &leader);
-        else {
-                if (leader_pid < 0)
-                        return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Leader PID is not valid");
-
-                r = pidref_set_pid(&leader, leader_pid);
-        }
-        if (r < 0)
-                return r;
-
-        if (leader.pid == 1 || leader.pid == getpid_cached())
-                return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid leader PID");
-
-        if (isempty(type))
-                t = _SESSION_TYPE_INVALID;
-        else {
-                t = session_type_from_string(type);
-                if (t < 0)
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "Invalid session type %s", type);
-        }
-
-        if (isempty(class))
-                c = _SESSION_CLASS_INVALID;
-        else {
-                c = session_class_from_string(class);
-                if (c < 0)
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "Invalid session class %s", class);
-        }
-
-        if (isempty(desktop))
-                desktop = NULL;
-        else {
-                if (!string_is_safe(desktop))
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "Invalid desktop string %s", desktop);
-        }
-
-        if (isempty(cseat))
-                seat = NULL;
-        else {
-                seat = hashmap_get(m->seats, cseat);
-                if (!seat)
-                        return sd_bus_error_setf(error, BUS_ERROR_NO_SUCH_SEAT,
-                                                 "No seat '%s' known", cseat);
-        }
-
-        if (tty_is_vc(tty)) {
-                int v;
-
-                if (!seat)
-                        seat = m->seat0;
-                else if (seat != m->seat0)
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "TTY %s is virtual console but seat %s is not seat0", tty, seat->id);
-
-                v = vtnr_from_tty(tty);
-                if (v <= 0)
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "Cannot determine VT number from virtual console TTY %s", tty);
-
-                if (vtnr == 0)
-                        vtnr = (uint32_t) v;
-                else if (vtnr != (uint32_t) v)
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "Specified TTY and VT number do not match");
-
-        } else if (tty_is_console(tty)) {
-
-                if (!seat)
-                        seat = m->seat0;
-                else if (seat != m->seat0)
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "Console TTY specified but seat is not seat0");
-
-                if (vtnr != 0)
-                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                 "Console TTY specified but VT number is not 0");
-        }
-
-        if (seat) {
-                if (seat_has_vts(seat)) {
-                        if (vtnr <= 0 || vtnr > 63)
-                                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                         "VT number out of range");
-                } else {
-                        if (vtnr != 0)
-                                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
-                                                         "Seat has no VTs but VT number not 0");
-                }
-        }
-
-        if (t == _SESSION_TYPE_INVALID) {
-                if (!isempty(display))
-                        t = SESSION_X11;
-                else if (!isempty(tty))
-                        t = SESSION_TTY;
-                else
-                        t = SESSION_UNSPECIFIED;
-        }
-
-        if (c == _SESSION_CLASS_INVALID) {
-                if (t == SESSION_UNSPECIFIED)
-                        c = SESSION_BACKGROUND;
-                else
-                        c = SESSION_USER;
-        }
-
-        /* Check if we are already in a logind session, and if so refuse. */
-        r = manager_get_session_by_pidref(m, &leader, /* ret_session= */ NULL);
-        if (r < 0)
-                return log_debug_errno(
-                                r,
-                                "Failed to check if process " PID_FMT " is already in a session: %m",
-                                leader.pid);
-        if (r > 0)
-                return sd_bus_error_setf(error, BUS_ERROR_SESSION_BUSY,
-                                         "Already running in a session or user slice");
-
-        /* Old gdm and lightdm start the user-session on the same VT as the greeter session. But they destroy
-         * the greeter session after the user-session and want the user-session to take over the VT. We need
-         * to support this for backwards-compatibility, so make sure we allow new sessions on a VT that a
-         * greeter is running on. Furthermore, to allow re-logins, we have to allow a greeter to take over a
-         * used VT for the exact same reasons. */
-        if (c != SESSION_GREETER &&
-            vtnr > 0 &&
-            vtnr < MALLOC_ELEMENTSOF(m->seat0->positions) &&
-            m->seat0->positions[vtnr] &&
-            m->seat0->positions[vtnr]->class != SESSION_GREETER)
-                return sd_bus_error_set(error, BUS_ERROR_SESSION_BUSY, "Already occupied by a session");
-
-        if (hashmap_size(m->sessions) >= m->sessions_max)
-                return sd_bus_error_setf(error, SD_BUS_ERROR_LIMITS_EXCEEDED,
-                                         "Maximum number of sessions (%" PRIu64 ") reached, refusing further sessions.",
-                                         m->sessions_max);
-
-        (void) audit_session_from_pid(&leader, &audit_id);
         if (audit_session_is_valid(audit_id)) {
                 /* Keep our session IDs and the audit session IDs in sync */
 
@@ -1022,7 +856,7 @@ static int create_session(
                 }
         }
 
-        if (!id) {
+        if (!id)
                 do {
                         id = mfree(id);
 
@@ -1030,15 +864,97 @@ static int create_session(
                                 return -ENOMEM;
 
                 } while (hashmap_contains(m->sessions, id));
-        }
 
         /* The generated names should not clash with 'auto' or 'self' */
         assert(!SESSION_IS_SELF(id));
         assert(!SESSION_IS_AUTO(id));
 
+        *ret_id = TAKE_PTR(id);
+        return 0;
+}
+
+int manager_create_session(
+                Manager *m,
+                uid_t uid,
+                PidRef *leader, /* consumed */
+                const char *service,
+                SessionType type,
+                SessionClass class,
+                const char *desktop,
+                Seat *seat,
+                unsigned vtnr,
+                const char *tty,
+                const char *display,
+                bool remote,
+                const char *remote_user,
+                const char *remote_host,
+                Session **ret_session) {
+
+        int r;
+
+        assert(m);
+        assert(uid_is_valid(uid));
+        assert(pidref_is_set(leader));
+        assert(ret_session);
+
+        /* Returns:
+         *    -EBUSY         → client is already in a session
+         *    -EADDRNOTAVAIL → VT is already taken
+         *    -EUSERS        → limit of sessions reached
+         */
+
+        if (type == _SESSION_TYPE_INVALID) {
+                if (!isempty(display))
+                        type = SESSION_X11;
+                else if (!isempty(tty))
+                        type = SESSION_TTY;
+                else
+                        type = SESSION_UNSPECIFIED;
+        }
+
+        if (class == _SESSION_CLASS_INVALID) {
+                if (type == SESSION_UNSPECIFIED)
+                        class = SESSION_BACKGROUND;
+                else
+                        class = SESSION_USER;
+        }
+
+        /* Check if we are already in a logind session, and if so refuse. */
+        r = manager_get_session_by_pidref(m, leader, /* ret_session= */ NULL);
+        if (r < 0)
+                return log_debug_errno(
+                                r,
+                                "Failed to check if process " PID_FMT " is already in a session: %m",
+                                leader->pid);
+        if (r > 0)
+                return log_debug_errno(SYNTHETIC_ERRNO(EBUSY), "Client is already in a session.");
+
+        /* Old gdm and lightdm start the user-session on the same VT as the greeter session. But they destroy
+         * the greeter session after the user-session and want the user-session to take over the VT. We need
+         * to support this for backwards-compatibility, so make sure we allow new sessions on a VT that a
+         * greeter is running on. Furthermore, to allow re-logins, we have to allow a greeter to take over a
+         * used VT for the exact same reasons. */
+        if (class != SESSION_GREETER &&
+            vtnr > 0 &&
+            vtnr < MALLOC_ELEMENTSOF(m->seat0->positions) &&
+            m->seat0->positions[vtnr] &&
+            m->seat0->positions[vtnr]->class != SESSION_GREETER)
+                return log_debug_errno(SYNTHETIC_ERRNO(EADDRNOTAVAIL), "VT already occupied by a session.");
+
+        if (hashmap_size(m->sessions) >= m->sessions_max)
+                return log_debug_errno(SYNTHETIC_ERRNO(EUSERS), "Maximum number of sessions (%" PRIu64 ") reached, refusing further sessions.", m->sessions_max);
+
+        _cleanup_free_ char *id = NULL;
+        r = manager_choose_session_id(m, leader, &id);
+        if (r < 0)
+                return r;
+
         /* If we are not watching utmp already, try again */
         manager_reconnect_utmp(m);
 
+        User *user = NULL;
+        Session *session = NULL;
+
         r = manager_add_user_by_uid(m, uid, &user);
         if (r < 0)
                 goto fail;
@@ -1048,21 +964,21 @@ static int create_session(
                 goto fail;
 
         session_set_user(session, user);
-        r = session_set_leader_consume(session, TAKE_PIDREF(leader));
+        r = session_set_leader_consume(session, TAKE_PIDREF(*leader));
         if (r < 0)
                 goto fail;
 
-        session->original_type = session->type = t;
+        session->original_type = session->type = type;
         session->remote = remote;
         session->vtnr = vtnr;
-        session->class = c;
+        session->class = class;
 
         /* Once the first session that is of a pinning class shows up we'll change the GC mode for the user
          * from USER_GC_BY_ANY to USER_GC_BY_PIN, so that the user goes away once the last pinning session
          * goes away. Background: we want that user@.service – when started manually – remains around (which
          * itself is a non-pinning session), but gets stopped when the last pinning session goes away. */
 
-        if (SESSION_CLASS_PIN_USER(c))
+        if (SESSION_CLASS_PIN_USER(class))
                 user->gc_mode = USER_GC_BY_PIN;
 
         if (!isempty(tty)) {
@@ -1109,14 +1025,184 @@ static int create_session(
                         goto fail;
         }
 
+        *ret_session = session;
+        return 0;
+
+fail:
+        if (session)
+                session_add_to_gc_queue(session);
+
+        if (user)
+                user_add_to_gc_queue(user);
+
+        return r;
+}
+
+static int manager_create_session_by_bus(
+                Manager *m,
+                sd_bus_message *message,
+                sd_bus_error *error,
+                uid_t uid,
+                pid_t leader_pid,
+                int leader_pidfd,
+                const char *service,
+                const char *type,
+                const char *class,
+                const char *desktop,
+                const char *cseat,
+                uint32_t vtnr,
+                const char *tty,
+                const char *display,
+                int remote,
+                const char *remote_user,
+                const char *remote_host,
+                uint64_t flags) {
+
+        int r;
+
+        assert(m);
+        assert(message);
+
+        if (!uid_is_valid(uid))
+                return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid UID");
+
+        if (flags != 0)
+                return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Flags must be zero.");
+
+        _cleanup_(pidref_done) PidRef leader = PIDREF_NULL;
+        if (leader_pidfd >= 0)
+                r = pidref_set_pidfd(&leader, leader_pidfd);
+        else if (leader_pid == 0)
+                r = bus_query_sender_pidref(message, &leader);
+        else {
+                if (leader_pid < 0)
+                        return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Leader PID is not valid");
+
+                r = pidref_set_pid(&leader, leader_pid);
+        }
+        if (r < 0)
+                return r;
+
+        if (leader.pid == 1 || pidref_is_self(&leader))
+                return sd_bus_error_set(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid leader PID");
+
+        SessionType t;
+        if (isempty(type))
+                t = _SESSION_TYPE_INVALID;
+        else {
+                t = session_type_from_string(type);
+                if (t < 0)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "Invalid session type %s", type);
+        }
+
+        SessionClass c;
+        if (isempty(class))
+                c = _SESSION_CLASS_INVALID;
+        else {
+                c = session_class_from_string(class);
+                if (c < 0)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "Invalid session class %s", class);
+        }
+
+        if (isempty(desktop))
+                desktop = NULL;
+        else {
+                if (!string_is_safe(desktop))
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "Invalid desktop string %s", desktop);
+        }
+
+        Seat *seat = NULL;
+        if (isempty(cseat))
+                seat = NULL;
+        else {
+                seat = hashmap_get(m->seats, cseat);
+                if (!seat)
+                        return sd_bus_error_setf(error, BUS_ERROR_NO_SUCH_SEAT,
+                                                 "No seat '%s' known", cseat);
+        }
+
+        if (isempty(tty))
+                tty = NULL;
+        else if (tty_is_vc(tty)) {
+                int v;
+
+                if (!seat)
+                        seat = m->seat0;
+                else if (seat != m->seat0)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "TTY %s is virtual console but seat %s is not seat0", tty, seat->id);
+
+                v = vtnr_from_tty(tty);
+                if (v <= 0)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "Cannot determine VT number from virtual console TTY %s", tty);
+
+                if (vtnr == 0)
+                        vtnr = (uint32_t) v;
+                else if (vtnr != (uint32_t) v)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "Specified TTY and VT number do not match");
+
+        } else if (tty_is_console(tty)) {
+
+                if (!seat)
+                        seat = m->seat0;
+                else if (seat != m->seat0)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "Console TTY specified but seat is not seat0");
+
+                if (vtnr != 0)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                 "Console TTY specified but VT number is not 0");
+        }
+
+        if (seat) {
+                if (seat_has_vts(seat)) {
+                        if (!vtnr_is_valid(vtnr))
+                                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                         "VT number out of range");
+                } else {
+                        if (vtnr != 0)
+                                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                                         "Seat has no VTs but VT number not 0");
+                }
+        }
+
+        Session *session;
+        r = manager_create_session(
+                        m,
+                        uid,
+                        &leader,
+                        service,
+                        t,
+                        c,
+                        desktop,
+                        seat,
+                        vtnr,
+                        tty,
+                        display,
+                        remote,
+                        remote_user,
+                        remote_host,
+                        &session);
+        if (r == -EBUSY)
+                return sd_bus_error_setf(error, BUS_ERROR_SESSION_BUSY, "Already running in a session or user slice");
+        if (r == -EADDRNOTAVAIL)
+                return sd_bus_error_set(error, BUS_ERROR_SESSION_BUSY, "Virtual terminal already occupied by a session");
+        if (r == -EUSERS)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_LIMITS_EXCEEDED, "Maximum number of sessions (%" PRIu64 ") reached, refusing further sessions.", m->sessions_max);
+        if (r < 0)
+                return r;
+
         r = sd_bus_message_enter_container(message, 'a', "(sv)");
         if (r < 0)
                 goto fail;
-
         r = session_start(session, message, error);
         if (r < 0)
                 goto fail;
-
         r = sd_bus_message_exit_container(message);
         if (r < 0)
                 goto fail;
@@ -1130,7 +1216,7 @@ static int create_session(
          * all is complete - or wait again. */
         r = session_send_create_reply(session, /* error= */ NULL);
         if (r < 0)
-                return r;
+                goto fail;
 
         return 1;
 
@@ -1138,9 +1224,6 @@ fail:
         if (session)
                 session_add_to_gc_queue(session);
 
-        if (user)
-                user_add_to_gc_queue(user);
-
         return r;
 }
 
@@ -1175,9 +1258,9 @@ static int method_create_session(sd_bus_message *message, void *userdata, sd_bus
         if (r < 0)
                 return r;
 
-        return create_session(
+        return manager_create_session_by_bus(
-                        message,
                         userdata,
+                        message,
                         error,
                         uid,
                         leader_pid,
@@ -1223,9 +1306,9 @@ static int method_create_session_pidfd(sd_bus_message *message, void *userdata,
         if (r < 0)
                 return r;
 
-        return create_session(
+        return manager_create_session_by_bus(
-                        message,
                         userdata,
+                        message,
                         error,
                         uid,
                         /* leader_pid = */ 0,

src/login/logind-dbus.h

@@ -47,4 +47,21 @@ int manager_job_is_active(Manager *manager, const char *path, sd_bus_error *erro
 
 void manager_load_scheduled_shutdown(Manager *m);
 
+int manager_create_session(
+                Manager *m,
+                uid_t uid,
+                PidRef *leader,
+                const char *service,
+                SessionType type,
+                SessionClass class,
+                const char *desktop,
+                Seat *seat,
+                unsigned vtnr,
+                const char *tty,
+                const char *display,
+                bool remote,
+                const char *remote_user,
+                const char *remote_host,
+                Session **ret_session);
+
 extern const BusObjectImplementation manager_object;

src/login/logind-session-dbus.c

@@ -899,62 +899,40 @@ int session_send_lock_all(Manager *m, bool lock) {
         return r;
 }
 
-static bool session_job_pending(Session *s) {
+int session_send_create_reply_bus(Session *s, const sd_bus_error *error) {
-        assert(s);
-        assert(s->user);
-
-        /* Check if we have some jobs enqueued and not finished yet. Each time we get JobRemoved signal about
-         * relevant units, session_send_create_reply and hence us is called (see match_job_removed).
-         * Note that we don't care about job result here. */
-
-        return s->scope_job ||
-               s->user->runtime_dir_job ||
-               (SESSION_CLASS_WANTS_SERVICE_MANAGER(s->class) && s->user->service_manager_job);
-}
-
-int session_send_create_reply(Session *s, sd_bus_error *error) {
-        _cleanup_(sd_bus_message_unrefp) sd_bus_message *c = NULL;
-        _cleanup_close_ int fifo_fd = -EBADF;
-        _cleanup_free_ char *p = NULL;
-
         assert(s);
 
-        /* This is called after the session scope and the user service were successfully created, and finishes where
+        /* This is called after the session scope and the user service were successfully created, and
-         * bus_manager_create_session() left off. */
+         * finishes where manager_create_session() left off. */
 
-        if (!s->create_message)
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *c = TAKE_PTR(s->create_message);
+        if (!c)
                 return 0;
 
-        /* If error occurred, return it immediately. Otherwise let's wait for all jobs to finish before
+        if (sd_bus_error_is_set(error))
-         * continuing. */
-        if (!sd_bus_error_is_set(error) && session_job_pending(s))
-                return 0;
-
-        c = TAKE_PTR(s->create_message);
-        if (error)
                 return sd_bus_reply_method_error(c, error);
 
-        fifo_fd = session_create_fifo(s);
+        _cleanup_close_ int fifo_fd = session_create_fifo(s);
         if (fifo_fd < 0)
                 return fifo_fd;
 
         /* Update the session state file before we notify the client about the result. */
         session_save(s);
 
-        p = session_bus_path(s);
+        _cleanup_free_ char *p = session_bus_path(s);
         if (!p)
                 return -ENOMEM;
 
-        log_debug("Sending reply about created session: "
+        log_debug("Sending D-Bus reply about created session: "
-                  "id=%s object_path=%s uid=%u runtime_path=%s "
+                  "id=%s object_path=%s uid=" UID_FMT " runtime_path=%s "
                   "session_fd=%d seat=%s vtnr=%u",
                   s->id,
                   p,
-                  (uint32_t) s->user->user_record->uid,
+                  s->user->user_record->uid,
                   s->user->runtime_path,
                   fifo_fd,
                   s->seat ? s->seat->id : "",
-                  (uint32_t) s->vtnr);
+                  s->vtnr);
 
         return sd_bus_reply_method_return(
                         c, "soshusub",
@@ -968,7 +946,7 @@ int session_send_create_reply(Session *s, sd_bus_error *error) {
                         false);
 }
 
-int session_send_upgrade_reply(Session *s, sd_bus_error *error) {
+int session_send_upgrade_reply(Session *s, const sd_bus_error *error) {
         _cleanup_(sd_bus_message_unrefp) sd_bus_message *c = NULL;
         assert(s);
 

src/login/logind-session-dbus.h

@@ -15,8 +15,8 @@ int session_send_changed(Session *s, const char *properties, ...) _sentinel_;
 int session_send_lock(Session *s, bool lock);
 int session_send_lock_all(Manager *m, bool lock);
 
-int session_send_create_reply(Session *s, sd_bus_error *error);
+int session_send_create_reply_bus(Session *s, const sd_bus_error *error);
-int session_send_upgrade_reply(Session *s, sd_bus_error *error);
+int session_send_upgrade_reply(Session *s, const sd_bus_error *error);
 
 int bus_session_method_activate(sd_bus_message *message, void *userdata, sd_bus_error *error);
 int bus_session_method_lock(sd_bus_message *message, void *userdata, sd_bus_error *error);

src/login/logind-session.c

@@ -29,6 +29,7 @@
 #include "logind-session-dbus.h"
 #include "logind-session.h"
 #include "logind-user-dbus.h"
+#include "logind-varlink.h"
 #include "mkdir-label.h"
 #include "parse-util.h"
 #include "path-util.h"
@@ -192,6 +193,8 @@ Session* session_free(Session *s) {
         sd_bus_message_unref(s->create_message);
         sd_bus_message_unref(s->upgrade_message);
 
+        sd_varlink_unref(s->create_link);
+
         free(s->tty);
         free(s->display);
         free(s->remote_host);
@@ -1648,6 +1651,35 @@ void session_drop_controller(Session *s) {
         session_restore_vt(s);
 }
 
+bool session_job_pending(Session *s) {
+        assert(s);
+        assert(s->user);
+
+        /* Check if we have some jobs enqueued and not finished yet. Each time we get JobRemoved signal about
+         * relevant units, session_send_create_reply and hence us is called (see match_job_removed).
+         * Note that we don't care about job result here. */
+
+        return s->scope_job ||
+               s->user->runtime_dir_job ||
+               (SESSION_CLASS_WANTS_SERVICE_MANAGER(s->class) && s->user->service_manager_job);
+}
+
+int session_send_create_reply(Session *s, const sd_bus_error *error) {
+        int r;
+
+        assert(s);
+
+        /* If error occurred, return it immediately. Otherwise let's wait for all jobs to finish before
+         * continuing. */
+        if (!sd_bus_error_is_set(error) && session_job_pending(s))
+                return 0;
+
+        r = 0;
+        RET_GATHER(r, session_send_create_reply_bus(s, error));
+        RET_GATHER(r, session_send_create_reply_varlink(s, error));
+        return r;
+}
+
 static const char* const session_state_table[_SESSION_STATE_MAX] = {
         [SESSION_OPENING] = "opening",
         [SESSION_ONLINE]  = "online",

src/login/logind-session.h

@@ -150,6 +150,8 @@ struct Session {
         sd_bus_message *create_message;   /* The D-Bus message used to create the session, which we haven't responded to yet */
         sd_bus_message *upgrade_message;  /* The D-Bus message used to upgrade the session class user-incomplete → user, which we haven't responded to yet */
 
+        sd_varlink *create_link; /* The Varlink connection used to create session, which we haven't responded to yet */
+
         /* Set up when a client requested to release the session via the bus */
         sd_event_source *timer_event_source;
 
@@ -216,6 +218,10 @@ bool session_is_controller(Session *s, const char *sender);
 int session_set_controller(Session *s, const char *sender, bool force, bool prepare);
 void session_drop_controller(Session *s);
 
+bool session_job_pending(Session *s);
+
+int session_send_create_reply(Session *s, const sd_bus_error *error);
+
 static inline bool SESSION_IS_SELF(const char *name) {
         return isempty(name) || streq(name, "self");
 }

src/login/logind-varlink.c

@@ -0,0 +1,373 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "cgroup-util.h"
+#include "fd-util.h"
+#include "json-util.h"
+#include "logind.h"
+#include "logind-dbus.h"
+#include "logind-session-dbus.h"
+#include "logind-varlink.h"
+#include "terminal-util.h"
+#include "user-util.h"
+#include "varlink-io.systemd.Login.h"
+#include "varlink-util.h"
+
+static int manager_varlink_get_session_by_peer(
+                Manager *m,
+                sd_varlink *link,
+                bool consult_display,
+                Session **ret) {
+
+        int r;
+
+        assert(m);
+        assert(link);
+        assert(ret);
+
+        /* Determines the session of the peer. If the peer is not part of a session, but consult_display is
+         * true, then will return the display session of the peer's owning user */
+
+        _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
+        r = varlink_get_peer_pidref(link, &pidref);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire peer PID: %m");
+
+        Session *session = NULL;
+        _cleanup_free_ char *name = NULL;
+        r = cg_pidref_get_session(&pidref, &name);
+        if (r < 0) {
+                if (!consult_display)
+                        log_debug_errno(r, "Failed to acquire session of peer, giving up: %m");
+                else {
+                        log_debug_errno(r, "Failed to acquire session of peer, trying to find owner UID: %m");
+
+                        uid_t uid;
+                        r = cg_pidref_get_owner_uid(&pidref, &uid);
+                        if (r < 0)
+                                log_debug_errno(r, "Failed to acquire owning UID of peer, giving up: %m");
+                        else {
+                                User *user = hashmap_get(m->users, UID_TO_PTR(uid));
+                                if (user)
+                                        session = user->display;
+                         }
+                }
+        } else
+                session = hashmap_get(m->sessions, name);
+
+        if (!session)
+                return sd_varlink_error(link, "io.systemd.Login.NoSuchSession", /* parameters= */ NULL);
+
+        *ret = session;
+        return 0;
+}
+
+static int manager_varlink_get_session_by_name(
+                Manager *m,
+                sd_varlink *link,
+                const char *name,
+                Session **ret) {
+
+        assert(m);
+        assert(link);
+        assert(ret);
+
+        /* Resolves a session name to a session object. Supports resolving the special names "self" and "auto". */
+
+        if (SESSION_IS_SELF(name))
+                return manager_varlink_get_session_by_peer(m, link, /* consult_display= */ false, ret);
+        if (SESSION_IS_AUTO(name))
+                return manager_varlink_get_session_by_peer(m, link, /* consult_display= */ true, ret);
+
+        Session *session = hashmap_get(m->sessions, name);
+        if (!session)
+                return sd_varlink_error(link, "io.systemd.Login.NoSuchSession", /* parameters= */ NULL);
+
+        *ret = session;
+        return 0;
+}
+
+int session_send_create_reply_varlink(Session *s, const sd_bus_error *error) {
+        assert(s);
+
+        /* This is called after the session scope and the user service were successfully created, and
+         * finishes where manager_create_session() left off. */
+
+        _cleanup_(sd_varlink_unrefp) sd_varlink *vl = TAKE_PTR(s->create_link);
+        if (!vl)
+                return 0;
+
+        if (sd_bus_error_is_set(error))
+                return sd_varlink_error(vl, "io.systemd.Login.UnitAllocationFailed", /* parameters= */ NULL);
+
+        _cleanup_close_ int fifo_fd = session_create_fifo(s);
+        if (fifo_fd < 0)
+                return fifo_fd;
+
+        /* Update the session state file before we notify the client about the result. */
+        session_save(s);
+
+        log_debug("Sending Varlink reply about created session: "
+                  "id=%s uid=" UID_FMT " runtime_path=%s "
+                  "session_fd=%d seat=%s vtnr=%u",
+                  s->id,
+                  s->user->user_record->uid,
+                  s->user->runtime_path,
+                  fifo_fd,
+                  s->seat ? s->seat->id : "",
+                  s->vtnr);
+
+        int fifo_fd_idx = sd_varlink_push_fd(vl, fifo_fd);
+        if (fifo_fd_idx < 0) {
+                log_error_errno(fifo_fd_idx, "Failed to push FIFO fd to Varlink: %m");
+                return sd_varlink_error_errno(vl, fifo_fd_idx);
+        }
+
+        TAKE_FD(fifo_fd);
+
+        return sd_varlink_replybo(
+                        vl,
+                        SD_JSON_BUILD_PAIR_STRING("Id", s->id),
+                        SD_JSON_BUILD_PAIR_STRING("RuntimePath", s->user->runtime_path),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("SessionFileDescriptor", fifo_fd_idx),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("UID", s->user->user_record->uid),
+                        SD_JSON_BUILD_PAIR_CONDITION(!!s->seat, "Seat", SD_JSON_BUILD_STRING(s->seat ? s->seat->id : NULL)),
+                        SD_JSON_BUILD_PAIR_CONDITION(s->vtnr > 0, "VTNr", SD_JSON_BUILD_UNSIGNED(s->vtnr)));
+}
+
+static JSON_DISPATCH_ENUM_DEFINE(json_dispatch_session_class, SessionClass, session_class_from_string);
+static JSON_DISPATCH_ENUM_DEFINE(json_dispatch_session_type, SessionType, session_type_from_string);
+
+static int vl_method_create_session(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+        int r;
+
+        struct {
+                uid_t uid;
+                const char *service;
+                SessionType type;
+                SessionClass class;
+                const char *desktop;
+                const char *seat;
+                unsigned vtnr;
+                const char *tty;
+                const char *display;
+                int remote;
+                const char *remote_user;
+                const char *remote_host;
+        } p = {
+                .uid = UID_INVALID,
+                .class = _SESSION_CLASS_INVALID,
+                .type = _SESSION_TYPE_INVALID,
+                .remote = -1,
+        };
+
+        static const sd_json_dispatch_field dispatch_table[] = {
+                { "UID",        _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid,      voffsetof(p, uid),         SD_JSON_MANDATORY },
+                { "Service",    SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, service),     0                 },
+                { "Type",       SD_JSON_VARIANT_STRING,        json_dispatch_session_type,    voffsetof(p, type),        SD_JSON_MANDATORY },
+                { "Class",      SD_JSON_VARIANT_STRING,        json_dispatch_session_class,   voffsetof(p, class),       SD_JSON_MANDATORY },
+                { "Desktop",    SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, desktop),     SD_JSON_STRICT    },
+                { "Seat",       SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, seat),        0                 },
+                { "VTNr",       _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint,         voffsetof(p, vtnr),        0                 },
+                { "TTY",        SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, tty),         0                 },
+                { "Display",    SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, display),     0                 },
+                { "Remote",     SD_JSON_VARIANT_BOOLEAN,       sd_json_dispatch_tristate,     voffsetof(p, remote),      0                 },
+                { "RemoteUser", SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, remote_user), 0                 },
+                { "RemoteHost", SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, remote_host), 0                 },
+                {}
+        };
+
+        r = sd_varlink_dispatch(link, parameters, dispatch_table, &p);
+        if (r != 0)
+                return r;
+
+        Seat *seat = NULL;
+        if (p.seat) {
+                seat = hashmap_get(m->seats, p.seat);
+                if (!seat)
+                        return sd_varlink_replyb(link, "io.systemd.Login.NoSuchSeat", /* parameters= */ NULL);
+        }
+
+        if (p.tty) {
+                if (tty_is_vc(p.tty)) {
+                        if (!seat)
+                                seat = m->seat0;
+                        else if (seat != m->seat0)
+                                return sd_varlink_error_invalid_parameter_name(link, "Seat");
+
+                        int v = vtnr_from_tty(p.tty);
+                        if (v <= 0)
+                                return sd_varlink_error_invalid_parameter_name(link, "TTY");
+
+                        if (p.vtnr == 0)
+                                p.vtnr = v;
+                        else if (p.vtnr != (unsigned) v)
+                                return sd_varlink_error_invalid_parameter_name(link, "VTNr");
+
+                } else if (tty_is_console(p.tty)) {
+                        if (!seat)
+                                seat = m->seat0;
+                        else if (seat != m->seat0)
+                                return sd_varlink_error_invalid_parameter_name(link, "Seat");
+
+                        if (p.vtnr != 0)
+                                return sd_varlink_error_invalid_parameter_name(link, "VTNr");
+                }
+        }
+
+        if (seat) {
+                if (seat_has_vts(seat)) {
+                        if (!vtnr_is_valid(p.vtnr))
+                                return sd_varlink_error_invalid_parameter_name(link, "VTNr");
+                } else {
+                        if (p.vtnr != 0)
+                                return sd_varlink_error_invalid_parameter_name(link, "VTNr");
+                }
+        }
+
+        if (p.remote < 0)
+                p.remote = p.remote_user || p.remote_host;
+
+        /* Before we continue processing this, let's ensure the peer is privileged */
+        uid_t peer_uid;
+        r = sd_varlink_get_peer_uid(link, &peer_uid);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to get peer UID: %m");
+        if (peer_uid != 0)
+                return sd_varlink_error(link, SD_VARLINK_ERROR_PERMISSION_DENIED, /* parameters= */ NULL);
+
+        _cleanup_(pidref_done) PidRef leader = PIDREF_NULL;
+        r = varlink_get_peer_pidref(link, &leader);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to get peer pidref: %m");
+
+        Session *session;
+        r = manager_create_session(
+                        m,
+                        p.uid,
+                        &leader,
+                        p.service,
+                        p.type,
+                        p.class,
+                        p.desktop,
+                        seat,
+                        p.vtnr,
+                        p.tty,
+                        p.display,
+                        p.remote,
+                        p.remote_user,
+                        p.remote_host,
+                        &session);
+        if (r == -EBUSY)
+                return sd_varlink_error(link, "io.systemd.Login.AlreadySessionMember", /* parameters= */ NULL);
+        if (r == -EADDRNOTAVAIL)
+                return sd_varlink_error(link, "io.systemd.Login.VirtualTerminalAlreadyTaken", /* parameters= */ NULL);
+        if (r == -EUSERS)
+                return sd_varlink_error(link, "io.systemd.Login.TooManySessions", /* parameters= */ NULL);
+        if (r < 0)
+                return r;
+
+        r = session_start(session, /* properties= */ NULL, /* error= */ NULL);
+        if (r < 0)
+                goto fail;
+
+        session->create_link = sd_varlink_ref(link);
+
+        /* Let's check if this is complete now */
+        r = session_send_create_reply(session, /* error= */ NULL);
+        if (r < 0)
+                goto fail;
+
+        return 1;
+
+fail:
+        if (session)
+                session_add_to_gc_queue(session);
+
+        return r;
+}
+
+static int vl_method_release_session(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+        int r;
+
+        struct {
+                const char *id;
+        } p;
+
+        static const sd_json_dispatch_field dispatch_table[] = {
+                { "Id", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, voffsetof(p, id), SD_JSON_MANDATORY },
+                {}
+        };
+
+        r = sd_varlink_dispatch(link, parameters, dispatch_table, &p);
+        if (r != 0)
+                return r;
+
+        Session *session;
+        r = manager_varlink_get_session_by_name(m, link, p.id, &session);
+        if (r != 0)
+                return r;
+
+        Session *peer_session;
+        r = manager_varlink_get_session_by_peer(m, link, /* consult_display= */ false, &peer_session);
+        if (r != 0)
+                return r;
+
+        if (session != peer_session)
+                return sd_varlink_error(link, SD_VARLINK_ERROR_PERMISSION_DENIED, /* parameters= */ NULL);
+
+        r = session_release(session);
+        if (r < 0)
+                return r;
+
+        return sd_varlink_replyb(link, SD_JSON_BUILD_EMPTY_OBJECT);
+}
+
+int manager_varlink_init(Manager *m) {
+        _cleanup_(sd_varlink_server_unrefp) sd_varlink_server *s = NULL;
+        int r;
+
+        assert(m);
+
+        if (m->varlink_server)
+                return 0;
+
+        r = sd_varlink_server_new(
+                        &s,
+                        SD_VARLINK_SERVER_ACCOUNT_UID|
+                        SD_VARLINK_SERVER_INHERIT_USERDATA|
+                        SD_VARLINK_SERVER_ALLOW_FD_PASSING_OUTPUT);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate varlink server object: %m");
+
+        sd_varlink_server_set_userdata(s, m);
+
+        r = sd_varlink_server_add_interface(s, &vl_interface_io_systemd_Login);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add Login interface to varlink server: %m");
+
+        r = sd_varlink_server_bind_method_many(
+                        s,
+                        "io.systemd.Login.CreateSession",  vl_method_create_session,
+                        "io.systemd.Login.ReleaseSession", vl_method_release_session);
+        if (r < 0)
+                return log_error_errno(r, "Failed to register varlink methods: %m");
+
+        r = sd_varlink_server_listen_address(s, "/run/systemd/io.systemd.Login", 0666);
+        if (r < 0)
+                return log_error_errno(r, "Failed to bind to varlink socket: %m");
+
+        r = sd_varlink_server_attach_event(s, m->event, SD_EVENT_PRIORITY_NORMAL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to attach varlink connection to event loop: %m");
+
+        m->varlink_server = TAKE_PTR(s);
+        return 0;
+}
+
+void manager_varlink_done(Manager *m) {
+        assert(m);
+
+        m->varlink_server = sd_varlink_server_unref(m->varlink_server);
+}

src/login/logind-varlink.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-bus.h"
+
+#include "logind.h"
+#include "logind-session.h"
+
+int manager_varlink_init(Manager *m);
+void manager_varlink_done(Manager *m);
+
+int session_send_create_reply_varlink(Session *s, const sd_bus_error *error);

src/login/logind.c

@@ -24,11 +24,12 @@
 #include "fd-util.h"
 #include "format-util.h"
 #include "fs-util.h"
+#include "logind.h"
 #include "logind-dbus.h"
 #include "logind-seat-dbus.h"
 #include "logind-session-dbus.h"
 #include "logind-user-dbus.h"
-#include "logind.h"
+#include "logind-varlink.h"
 #include "main-func.h"
 #include "mkdir-label.h"
 #include "parse-util.h"
@@ -153,6 +154,8 @@ static Manager* manager_free(Manager *m) {
 
         hashmap_free(m->polkit_registry);
 
+        manager_varlink_done(m);
+
         sd_bus_flush_close_unref(m->bus);
         sd_event_unref(m->event);
 
@@ -1114,6 +1117,10 @@ static int manager_startup(Manager *m) {
         if (r < 0)
                 return r;
 
+        r = manager_varlink_init(m);
+        if (r < 0)
+                return r;
+
         /* Instantiate magic seat 0 */
         r = manager_add_seat(m, "seat0", &m->seat0);
         if (r < 0)

src/login/logind.h

@@ -7,6 +7,7 @@
 #include "sd-bus.h"
 #include "sd-device.h"
 #include "sd-event.h"
+#include "sd-varlink.h"
 
 #include "calendarspec.h"
 #include "conf-parser.h"
@@ -145,6 +146,8 @@ struct Manager {
         struct stat efi_loader_entry_one_shot_stat;
 
         CalendarSpec *maintenance_time;
+
+        sd_varlink_server *varlink_server;
 };
 
 void manager_reset_config(Manager *m);

src/login/meson.build

@@ -26,6 +26,7 @@ liblogind_core_sources = files(
         'logind-session.c',
         'logind-user-dbus.c',
         'logind-user.c',
+        'logind-varlink.c',
         'logind-wall.c',
 )
 

src/login/pam_systemd.c

@@ -18,6 +18,9 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include "sd-bus.h"
+#include "sd-varlink.h"
+
 #include "alloc-util.h"
 #include "audit-util.h"
 #include "bus-common-errors.h"
@@ -35,6 +38,7 @@
 #include "format-util.h"
 #include "fs-util.h"
 #include "hostname-util.h"
+#include "json-util.h"
 #include "locale-util.h"
 #include "login-util.h"
 #include "macro.h"
@@ -390,116 +394,108 @@ static int export_legacy_dbus_address(
 }
 
 static int append_session_memory_max(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
-        uint64_t val;
         int r;
 
+        assert(handle);
+        assert(m);
+
         if (isempty(limit))
-                return PAM_SUCCESS;
+                return 0;
 
-        if (streq(limit, "infinity")) {
+        if (streq(limit, "infinity"))
-                r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", UINT64_MAX);
+                return sd_bus_message_append(m, "(sv)", "MemoryMax", "t", UINT64_MAX);
-                if (r < 0)
-                        return pam_bus_log_create_error(handle, r);
-
-                return PAM_SUCCESS;
-        }
 
         r = parse_permyriad(limit);
-        if (r >= 0) {
+        if (r < 0) {
-                r = sd_bus_message_append(m, "(sv)", "MemoryMaxScale", "u", UINT32_SCALE_FROM_PERMYRIAD(r));
+                uint64_t val;
-                if (r < 0)
-                        return pam_bus_log_create_error(handle, r);
-
-                return PAM_SUCCESS;
-        }
-
                 r = parse_size(limit, 1024, &val);
-        if (r >= 0) {
+                if (r < 0) {
-                r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", val);
-                if (r < 0)
-                        return pam_bus_log_create_error(handle, r);
-
-                return PAM_SUCCESS;
-        }
-
                         pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.memory_max, ignoring: %s", limit);
                         return PAM_SUCCESS;
+                }
+
+                return sd_bus_message_append(m, "(sv)", "MemoryMax", "t", val);
+        }
+
+        return sd_bus_message_append(m, "(sv)", "MemoryMaxScale", "u", UINT32_SCALE_FROM_PERMYRIAD(r));
 }
 
 static int append_session_runtime_max_sec(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
-        usec_t val;
         int r;
 
+        assert(handle);
+        assert(m);
+
         /* No need to parse "infinity" here, it will be set by default later in scope_init() */
         if (isempty(limit) || streq(limit, "infinity"))
-                return PAM_SUCCESS;
+                return 0;
 
+        usec_t val;
         r = parse_sec(limit, &val);
-        if (r >= 0) {
+        if (r < 0) {
-                r = sd_bus_message_append(m, "(sv)", "RuntimeMaxUSec", "t", (uint64_t) val);
-                if (r < 0)
-                        return pam_bus_log_create_error(handle, r);
-        } else
                 pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.runtime_max_sec: %s, ignoring.", limit);
+                return 0;
+        }
 
-        return PAM_SUCCESS;
+        return sd_bus_message_append(m, "(sv)", "RuntimeMaxUSec", "t", (uint64_t) val);
 }
 
 static int append_session_tasks_max(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
-        uint64_t val;
         int r;
 
+        assert(handle);
+        assert(m);
+
         /* No need to parse "infinity" here, it will be set unconditionally later in manager_start_scope() */
         if (isempty(limit) || streq(limit, "infinity"))
-                return PAM_SUCCESS;
+                return 0;
 
+        uint64_t val;
         r = safe_atou64(limit, &val);
-        if (r >= 0) {
+        if (r < 0) {
-                r = sd_bus_message_append(m, "(sv)", "TasksMax", "t", val);
-                if (r < 0)
-                        return pam_bus_log_create_error(handle, r);
-        } else
                 pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.tasks_max, ignoring: %s", limit);
+                return 0;
+        }
 
-        return PAM_SUCCESS;
+        return sd_bus_message_append(m, "(sv)", "TasksMax", "t", val);
 }
 
 static int append_session_cpu_weight(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
-        uint64_t val;
         int r;
 
-        if (isempty(limit))
+        assert(handle);
-                return PAM_SUCCESS;
+        assert(m);
 
+        if (isempty(limit))
+                return 0;
+
+        uint64_t val;
         r = cg_cpu_weight_parse(limit, &val);
-        if (r < 0)
+        if (r < 0) {
                 pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.cpu_weight, ignoring: %s", limit);
-        else {
+                return 0;
-                r = sd_bus_message_append(m, "(sv)", "CPUWeight", "t", val);
-                if (r < 0)
-                        return pam_bus_log_create_error(handle, r);
         }
 
-        return PAM_SUCCESS;
+        return sd_bus_message_append(m, "(sv)", "CPUWeight", "t", val);
 }
 
 static int append_session_io_weight(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
-        uint64_t val;
         int r;
 
-        if (isempty(limit))
+        assert(handle);
-                return PAM_SUCCESS;
+        assert(m);
 
+        if (isempty(limit))
+                return 0;
+
+        uint64_t val;
         r = cg_weight_parse(limit, &val);
-        if (r < 0)
+        if (r < 0) {
                 pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.io_weight, ignoring: %s", limit);
-        else {
+                return 0;
-                r = sd_bus_message_append(m, "(sv)", "IOWeight", "t", val);
-                if (r < 0)
-                        return pam_bus_log_create_error(handle, r);
         }
 
-        return PAM_SUCCESS;
+        return sd_bus_message_append(m, "(sv)", "IOWeight", "t", val);
 }
 
 static const char* getenv_harder(pam_handle_t *handle, const char *key, const char *fallback) {
@@ -549,6 +545,26 @@ static bool getenv_harder_bool(pam_handle_t *handle, const char *key, bool fallb
         return r;
 }
 
+static uint32_t getenv_harder_uint32(pam_handle_t *handle, const char *key, uint32_t fallback) {
+        int r;
+
+        assert(handle);
+        assert(key);
+
+        const char *v = getenv_harder(handle, key, NULL);
+        if (isempty(v))
+                return fallback;
+
+        uint32_t u;
+        r = safe_atou32(v, &u);
+        if (r < 0) {
+                pam_syslog(handle, LOG_ERR, "Unsigned integer environment variable value of '%s' is not valid: %s", key, v);
+                return fallback;
+        }
+
+        return u;
+}
+
 static int update_environment(pam_handle_t *handle, const char *key, const char *value) {
         int r;
 
@@ -826,17 +842,15 @@ static uint64_t pick_default_capability_ambient_set(
 }
 
 typedef struct SessionContext {
-        const uid_t uid;
-        const pid_t pid;
         const char *service;
         const char *type;
         const char *class;
         const char *desktop;
         const char *seat;
-        const uint32_t vtnr;
+        uint32_t vtnr;
         const char *tty;
         const char *display;
-        const bool remote;
+        bool remote;
         const char *remote_user;
         const char *remote_host;
         const char *memory_max;
@@ -844,11 +858,13 @@ typedef struct SessionContext {
         const char *cpu_weight;
         const char *io_weight;
         const char *runtime_max_sec;
+        bool incomplete;
 } SessionContext;
 
 static int create_session_message(
                 sd_bus *bus,
                 pam_handle_t *handle,
+                UserRecord *ur,
                 const SessionContext *context,
                 bool avoid_pidfd,
                 sd_bus_message **ret) {
@@ -859,6 +875,7 @@ static int create_session_message(
 
         assert(bus);
         assert(handle);
+        assert(ur);
         assert(context);
         assert(ret);
 
@@ -872,10 +889,11 @@ static int create_session_message(
         if (r < 0)
                 return r;
 
-        r = sd_bus_message_append(m,
+        r = sd_bus_message_append(
+                        m,
                         pidfd >= 0 ? "uhsssssussbss" : "uusssssussbss",
-                                  (uint32_t) context->uid,
+                        (uint32_t) ur->uid,
-                                  pidfd >= 0 ? pidfd : context->pid,
+                        pidfd >= 0 ? pidfd : 0,
                         context->service,
                         context->type,
                         context->class,
@@ -901,23 +919,23 @@ static int create_session_message(
                 return r;
 
         r = append_session_memory_max(handle, m, context->memory_max);
-        if (r != PAM_SUCCESS)
+        if (r < 0)
                 return r;
 
         r = append_session_runtime_max_sec(handle, m, context->runtime_max_sec);
-        if (r != PAM_SUCCESS)
+        if (r < 0)
                 return r;
 
         r = append_session_tasks_max(handle, m, context->tasks_max);
-        if (r != PAM_SUCCESS)
+        if (r < 0)
                 return r;
 
         r = append_session_cpu_weight(handle, m, context->cpu_weight);
-        if (r != PAM_SUCCESS)
+        if (r < 0)
                 return r;
 
         r = append_session_io_weight(handle, m, context->io_weight);
-        if (r != PAM_SUCCESS)
+        if (r < 0)
                 return r;
 
         r = sd_bus_message_close_container(m);
@@ -928,211 +946,251 @@ static int create_session_message(
         return 0;
 }
 
-_public_ PAM_EXTERN int pam_sm_open_session(
+static void session_context_mangle(
                 pam_handle_t *handle,
-                int flags,
+                SessionContext *c,
-                int argc, const char **argv) {
+                UserRecord *ur,
-
+                bool debug) {
-        /* Let's release the D-Bus connection once this function exits, after all the session might live
-         * quite a long time, and we are not going to process the bus connection in that time, so let's
-         * better close before the daemon kicks us off because we are not processing anything. */
-        _cleanup_(pam_bus_data_disconnectp) PamBusData *d = NULL;
-        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
-        _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL, *reply = NULL;
-        const char
-                *id, *object_path, *runtime_path,
-                *service = NULL,
-                *tty = NULL, *display = NULL,
-                *remote_user = NULL, *remote_host = NULL,
-                *seat = NULL,
-                *type = NULL, *class = NULL,
-                *class_pam = NULL, *type_pam = NULL, *cvtnr = NULL, *desktop = NULL, *desktop_pam = NULL,
-                *memory_max = NULL, *tasks_max = NULL, *cpu_weight = NULL, *io_weight = NULL, *runtime_max_sec = NULL;
-        uint64_t default_capability_bounding_set = UINT64_MAX, default_capability_ambient_set = UINT64_MAX;
-        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
-        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
-        int session_fd = -EBADF, existing, r;
-        bool debug = false, remote, incomplete;
-        uint32_t vtnr = 0;
-        uid_t original_uid;
 
         assert(handle);
+        assert(c);
+        assert(ur);
 
-        pam_log_setup();
+        if (streq_ptr(c->service, "systemd-user")) {
-
-        if (parse_argv(handle,
-                       argc, argv,
-                       &class_pam,
-                       &type_pam,
-                       &desktop_pam,
-                       &debug,
-                       &default_capability_bounding_set,
-                       &default_capability_ambient_set) < 0)
-                return PAM_SESSION_ERR;
-
-        pam_debug_syslog(handle, debug, "pam-systemd initializing");
-
-        r = acquire_user_record(handle, &ur);
-        if (r != PAM_SUCCESS)
-                return r;
-
-        /* Make most of this a NOP on non-logind systems */
-        if (!logind_running())
-                goto success;
-
-        r = pam_get_item_many(
-                        handle,
-                        PAM_SERVICE, &service,
-                        PAM_XDISPLAY, &display,
-                        PAM_TTY, &tty,
-                        PAM_RUSER, &remote_user,
-                        PAM_RHOST, &remote_host);
-        if (r != PAM_SUCCESS)
-                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM items: @PAMERR@");
-
-        seat = getenv_harder(handle, "XDG_SEAT", NULL);
-        cvtnr = getenv_harder(handle, "XDG_VTNR", NULL);
-        type = getenv_harder(handle, "XDG_SESSION_TYPE", type_pam);
-        class = getenv_harder(handle, "XDG_SESSION_CLASS", class_pam);
-        desktop = getenv_harder(handle, "XDG_SESSION_DESKTOP", desktop_pam);
-        incomplete = getenv_harder_bool(handle, "XDG_SESSION_INCOMPLETE", false);
-
-        if (streq_ptr(service, "systemd-user")) {
                 /* If we detect that we are running in the "systemd-user" PAM stack, then let's patch the class to
                  * 'manager' if not set, simply for robustness reasons. */
-                type = "unspecified";
+                c->type = "unspecified";
-                class = IN_SET(user_record_disposition(ur), USER_INTRINSIC, USER_SYSTEM, USER_DYNAMIC) ?
+                c->class = IN_SET(user_record_disposition(ur), USER_INTRINSIC, USER_SYSTEM, USER_DYNAMIC) ?
                         "manager-early" : "manager";
-                tty = NULL;
+                c->tty = NULL;
 
-        } else if (tty && strchr(tty, ':')) {
+        } else if (c->tty && strchr(c->tty, ':')) {
                 /* A tty with a colon is usually an X11 display, placed there to show up in utmp. We rearrange things
                  * and don't pretend that an X display was a tty. */
-                if (isempty(display))
+                if (isempty(c->display))
-                        display = tty;
+                        c->display = c->tty;
-                tty = NULL;
+                c->tty = NULL;
 
-        } else if (streq_ptr(tty, "cron")) {
+        } else if (streq_ptr(c->tty, "cron")) {
                 /* cron is setting PAM_TTY to "cron" for some reason (the commit carries no information why, but
                  * probably because it wants to set it to something as pam_time/pam_access/… require PAM_TTY to be set
                  * (as they otherwise even try to update it!) — but cron doesn't actually allocate a TTY for its forked
                  * off processes.) */
-                type = "unspecified";
+                c->type = "unspecified";
-                class = "background";
+                c->class = "background";
-                tty = NULL;
+                c->tty = NULL;
 
-        } else if (streq_ptr(tty, "ssh")) {
+        } else if (streq_ptr(c->tty, "ssh")) {
                 /* ssh has been setting PAM_TTY to "ssh" (for the same reason as cron does this, see above. For further
                  * details look for "PAM_TTY_KLUDGE" in the openssh sources). */
-                type = "tty";
+                c->type = "tty";
-                class = "user";
+                c->class = "user";
-                tty = NULL; /* This one is particularly sad, as this means that ssh sessions — even though usually
+                c->tty = NULL; /* This one is particularly sad, as this means that ssh sessions — even though
-                             * associated with a pty — won't be tracked by their tty in logind. This is because ssh
+                               * usually associated with a pty — won't be tracked by their tty in
-                             * does the PAM session registration early for new connections, and registers a pty only
+                               * logind. This is because ssh does the PAM session registration early for new
-                             * much later (this is because it doesn't know yet if it needs one at all, as whether to
+                               * connections, and registers a pty only much later (this is because it doesn't
-                             * register a pty or not is negotiated much later in the protocol). */
+                               * know yet if it needs one at all, as whether to register a pty or not is
+                               * negotiated much later in the protocol). */
 
-        } else if (tty)
+        } else if (c->tty)
                 /* Chop off leading /dev prefix that some clients specify, but others do not. */
-                tty = skip_dev_prefix(tty);
+                c->tty = skip_dev_prefix(c->tty);
 
-        /* If this fails vtnr will be 0, that's intended */
+        if (!isempty(c->display) && !c->vtnr) {
-        if (!isempty(cvtnr))
+                if (isempty(c->seat))
-                (void) safe_atou32(cvtnr, &vtnr);
+                        (void) get_seat_from_display(c->display, &c->seat, &c->vtnr);
-
+                else if (streq(c->seat, "seat0"))
-        if (!isempty(display) && !vtnr) {
+                        (void) get_seat_from_display(c->display, /* seat= */ NULL, &c->vtnr);
-                if (isempty(seat))
-                        (void) get_seat_from_display(display, &seat, &vtnr);
-                else if (streq(seat, "seat0"))
-                        (void) get_seat_from_display(display, NULL, &vtnr);
         }
 
-        if (seat && !streq(seat, "seat0") && vtnr != 0) {
+        if (c->seat && !streq(c->seat, "seat0") && c->vtnr != 0) {
-                pam_debug_syslog(handle, debug, "Ignoring vtnr %"PRIu32" for %s which is not seat0", vtnr, seat);
+                pam_debug_syslog(handle, debug, "Ignoring vtnr %"PRIu32" for %s which is not seat0", c->vtnr, c->seat);
-                vtnr = 0;
+                c->vtnr = 0;
         }
 
-        if (isempty(type))
+        if (isempty(c->type))
-                type = !isempty(display) ? "x11" :
+                c->type = !isempty(c->display) ? "x11" :
-                           !isempty(tty) ? "tty" : "unspecified";
+                              !isempty(c->tty) ? "tty" : "unspecified";
 
-        if (isempty(class))
+        if (isempty(c->class))
-                class = streq(type, "unspecified") ? "background" :
+                c->class = streq(c->type, "unspecified") ? "background" :
                         ((IN_SET(user_record_disposition(ur), USER_INTRINSIC, USER_SYSTEM, USER_DYNAMIC) &&
-                         streq(type, "tty")) ? "user-early" : "user");
+                         streq(c->type, "tty")) ? "user-early" : "user");
 
-        if (incomplete) {
+        if (c->incomplete) {
-                if (streq(class, "user"))
+                if (streq(c->class, "user"))
-                        class = "user-incomplete";
+                        c->class = "user-incomplete";
                 else
-                        pam_syslog_pam_error(handle, LOG_WARNING, 0, "PAM session of class '%s' is incomplete, which is not supported, ignoring.", class);
+                        pam_syslog_pam_error(handle, LOG_WARNING, 0, "PAM session of class '%s' is incomplete, which is not supported, ignoring.", c->class);
         }
 
-        remote = !isempty(remote_host) && !is_localhost(remote_host);
+        c->remote = !isempty(c->remote_host) && !is_localhost(c->remote_host);
+}
 
-        r = pam_get_data(handle, "systemd.memory_max", (const void **)&memory_max);
+static bool can_use_varlink(const SessionContext *c) {
-        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+        /* Since PID 1 currently doesn't do Varlink right now, we cannot directly set properties for the
-                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.memory_max data: @PAMERR@");
+         * scope, for now.  */
-        r = pam_get_data(handle, "systemd.tasks_max",  (const void **)&tasks_max);
+        return !c->memory_max &&
-        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                !c->runtime_max_sec &&
-                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.tasks_max data: @PAMERR@");
+                !c->tasks_max &&
-        r = pam_get_data(handle, "systemd.cpu_weight", (const void **)&cpu_weight);
+                !c->cpu_weight &&
-        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                !c->io_weight;
-                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.cpu_weight data: @PAMERR@");
+}
-        r = pam_get_data(handle, "systemd.io_weight",  (const void **)&io_weight);
+
-        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+static int register_session(
-                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.io_weight data: @PAMERR@");
+                pam_handle_t *handle,
-        r = pam_get_data(handle, "systemd.runtime_max_sec", (const void **)&runtime_max_sec);
+                SessionContext *c,
-        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                UserRecord *ur,
-                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.runtime_max_sec data: @PAMERR@");
+                bool debug,
+                char **ret_seat) {
+
+        int r;
+
+        assert(handle);
+        assert(c);
+        assert(ur);
+        assert(ret_seat);
+
+        /* Make most of this a NOP on non-logind systems */
+        if (!logind_running())
+                goto skip;
+
+        pam_debug_syslog(handle, debug,
+                         "Asking logind to create session: "
+                         "uid="UID_FMT" pid="PID_FMT" service=%s type=%s class=%s desktop=%s seat=%s vtnr=%"PRIu32" tty=%s display=%s remote=%s remote_user=%s remote_host=%s",
+                         ur->uid, getpid_cached(),
+                         strempty(c->service),
+                         c->type, c->class, strempty(c->desktop),
+                         strempty(c->seat), c->vtnr, strempty(c->tty), strempty(c->display),
+                         yes_no(c->remote), strempty(c->remote_user), strempty(c->remote_host));
+        pam_debug_syslog(handle, debug,
+                         "Session limits: "
+                         "memory_max=%s tasks_max=%s cpu_weight=%s io_weight=%s runtime_max_sec=%s",
+                         strna(c->memory_max), strna(c->tasks_max), strna(c->cpu_weight), strna(c->io_weight), strna(c->runtime_max_sec));
+
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL; /* the following variables point into this message, hence pin it for longer */
+        _cleanup_(sd_json_variant_unrefp) sd_json_variant *vreply = NULL; /* similar */
+        _cleanup_(sd_varlink_unrefp) sd_varlink *vl = NULL; /* similar */
+        const char *id = NULL, *object_path = NULL, *runtime_path = NULL, *real_seat = NULL;
+        int session_fd = -EBADF, existing = false;
+        uint32_t original_uid = UID_INVALID, real_vtnr = 0;
+
+        bool done = false;
+        if (can_use_varlink(c)) {
+
+                r = sd_varlink_connect_address(&vl, "/run/systemd/io.systemd.Login");
+                if (r < 0)
+                        log_debug_errno(r, "Failed to connect to logind via Varlink, falling back to D-Bus: %m");
+                else {
+                        r = sd_varlink_set_allow_fd_passing_input(vl, true);
+                        if (r < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to enable input fd passing on Varlink socket: %m");
+
+                        r = sd_varlink_set_allow_fd_passing_output(vl, true);
+                        if (r < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to enable output fd passing on Varlink socket: %m");
+
+                        r = sd_varlink_set_relative_timeout(vl, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC);
+                        if (r < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to set relative timeout on Varlink socket: %m");
+
+                        const char *error_id = NULL;
+                        r = sd_varlink_callbo(
+                                        vl,
+                                        "io.systemd.Login.CreateSession",
+                                        &vreply,
+                                        &error_id,
+                                        SD_JSON_BUILD_PAIR_UNSIGNED("UID", ur->uid),
+                                        JSON_BUILD_PAIR_STRING_NON_EMPTY("Service", c->service),
+                                        SD_JSON_BUILD_PAIR("Type", JSON_BUILD_STRING_UNDERSCORIFY(c->type)),
+                                        SD_JSON_BUILD_PAIR("Class", JSON_BUILD_STRING_UNDERSCORIFY(c->class)),
+                                        JSON_BUILD_PAIR_STRING_NON_EMPTY("Desktop", c->desktop),
+                                        JSON_BUILD_PAIR_STRING_NON_EMPTY("Seat", c->seat),
+                                        SD_JSON_BUILD_PAIR_CONDITION(c->vtnr > 0, "VTNr", SD_JSON_BUILD_UNSIGNED(c->vtnr)),
+                                        JSON_BUILD_PAIR_STRING_NON_EMPTY("TTY", c->tty),
+                                        JSON_BUILD_PAIR_STRING_NON_EMPTY("Display", c->display),
+                                        SD_JSON_BUILD_PAIR_BOOLEAN("Remote", c->remote),
+                                        JSON_BUILD_PAIR_STRING_NON_EMPTY("RemoteUser", c->remote_user),
+                                        JSON_BUILD_PAIR_STRING_NON_EMPTY("RemoteHost", c->remote_host));
+                        if (r < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, r,
+                                                        "Failed to register session: %s", error_id);
+                        if (streq_ptr(error_id, "io.systemd.Login.AlreadySessionMember")) {
+                                /* We are already in a session, don't do anything */
+                                pam_debug_syslog(handle, debug, "Not creating session: %s", error_id);
+                                goto skip;
+                        }
+                        if (error_id)
+                                return pam_syslog_errno(handle, LOG_ERR, sd_varlink_error_to_errno(error_id, vreply),
+                                                        "Failed to issue CreateSession() varlink call: %s", error_id);
+
+                        struct {
+                                const char *id;
+                                const char *runtime_path;
+                                unsigned session_fd_idx;
+                                uid_t uid;
+                                const char *seat;
+                                unsigned vtnr;
+                                bool existing;
+                        } p = {
+                                .session_fd_idx = UINT_MAX,
+                                .uid = UID_INVALID,
+                        };
+
+                        static const sd_json_dispatch_field dispatch_table[] = {
+                                { "Id",                    SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, id),             SD_JSON_MANDATORY },
+                                { "RuntimePath",           SD_JSON_VARIANT_STRING,        json_dispatch_const_path,      voffsetof(p, runtime_path),   SD_JSON_MANDATORY },
+                                { "SessionFileDescriptor", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint64,       voffsetof(p, session_fd_idx), SD_JSON_MANDATORY },
+                                { "UID",                   _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid,      voffsetof(p, uid),            SD_JSON_MANDATORY },
+                                { "Seat",                  SD_JSON_VARIANT_STRING,        sd_json_dispatch_const_string, voffsetof(p, seat),           0                 },
+                                { "VTNr",                  _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint,         voffsetof(p, vtnr),           0                 },
+                                {}
+                        };
+
+                        r = sd_json_dispatch(vreply, dispatch_table, SD_JSON_ALLOW_EXTENSIONS, &p);
+                        if (r < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to parse CreateSession() reply: %m");
+
+                        session_fd = sd_varlink_peek_fd(vl, p.session_fd_idx);
+                        if (session_fd < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, session_fd, "Failed to extract session fd from CreateSession() reply: %m");
+
+                        id = p.id;
+                        runtime_path = p.runtime_path;
+                        original_uid = p.uid;
+                        real_seat = p.seat;
+                        real_vtnr = p.vtnr;
+                        existing = false; /* Even on D-Bus logind only returns false these days */
+
+                        done = true;
+                }
+        }
+
+        if (!done) {
+                /* Let's release the D-Bus connection once we are done here, after all the session might live
+                 * quite a long time, and we are not going to process the bus connection in that time, so
+                 * let's better close before the daemon kicks us off because we are not processing
+                 * anything. */
+                _cleanup_(pam_bus_data_disconnectp) PamBusData *d = NULL;
+                _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 
                 /* Talk to logind over the message bus */
                 r = pam_acquire_bus_connection(handle, "pam-systemd", debug, &bus, &d);
                 if (r != PAM_SUCCESS)
                         return r;
 
-        pam_debug_syslog(handle, debug,
+                _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
-                         "Asking logind to create session: "
+                r = create_session_message(
-                         "uid="UID_FMT" pid="PID_FMT" service=%s type=%s class=%s desktop=%s seat=%s vtnr=%"PRIu32" tty=%s display=%s remote=%s remote_user=%s remote_host=%s",
+                                bus,
-                         ur->uid, getpid_cached(),
-                         strempty(service),
-                         type, class, strempty(desktop),
-                         strempty(seat), vtnr, strempty(tty), strempty(display),
-                         yes_no(remote), strempty(remote_user), strempty(remote_host));
-        pam_debug_syslog(handle, debug,
-                         "Session limits: "
-                         "memory_max=%s tasks_max=%s cpu_weight=%s io_weight=%s runtime_max_sec=%s",
-                         strna(memory_max), strna(tasks_max), strna(cpu_weight), strna(io_weight), strna(runtime_max_sec));
-
-        const SessionContext context = {
-                .uid = ur->uid,
-                .pid = 0,
-                .service = service,
-                .type = type,
-                .class = class,
-                .desktop = desktop,
-                .seat = seat,
-                .vtnr = vtnr,
-                .tty = tty,
-                .display = display,
-                .remote = remote,
-                .remote_user = remote_user,
-                .remote_host = remote_host,
-                .memory_max = memory_max,
-                .tasks_max = tasks_max,
-                .cpu_weight = cpu_weight,
-                .io_weight = io_weight,
-                .runtime_max_sec = runtime_max_sec,
-        };
-
-        r = create_session_message(bus,
                                 handle,
-                                   &context,
+                                ur,
+                                c,
                                 /* avoid_pidfd = */ false,
                                 &m);
                 if (r < 0)
                         return pam_bus_log_create_error(handle, r);
 
+                _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
                 r = sd_bus_call(bus, m, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC, &error, &reply);
                 if (r < 0 && sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_METHOD)) {
                         sd_bus_error_free(&error);
@@ -1142,7 +1200,8 @@ _public_ PAM_EXTERN int pam_sm_open_session(
                         m = sd_bus_message_unref(m);
                         r = create_session_message(bus,
                                                    handle,
-                                           &context,
+                                                   ur,
+                                                   c,
                                                    /* avoid_pidfd = */ true,
                                                    &m);
                         if (r < 0)
@@ -1155,7 +1214,7 @@ _public_ PAM_EXTERN int pam_sm_open_session(
                                 /* We are already in a session, don't do anything */
                                 pam_debug_syslog(handle, debug,
                                                  "Not creating session: %s", bus_error_message(&error, r));
-                        goto success;
+                                goto skip;
                         }
 
                         pam_syslog(handle, LOG_ERR,
@@ -1163,23 +1222,25 @@ _public_ PAM_EXTERN int pam_sm_open_session(
                         return PAM_SESSION_ERR;
                 }
 
-        r = sd_bus_message_read(reply,
+                r = sd_bus_message_read(
+                                reply,
                                 "soshusub",
                                 &id,
                                 &object_path,
                                 &runtime_path,
                                 &session_fd,
                                 &original_uid,
-                                &seat,
+                                &real_seat,
-                                &vtnr,
+                                &real_vtnr,
                                 &existing);
                 if (r < 0)
                         return pam_bus_log_parse_error(handle, r);
+        }
 
         pam_debug_syslog(handle, debug,
                          "Reply from logind: "
                          "id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
-                         id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);
+                         id, strna(object_path), runtime_path, session_fd, real_seat, real_vtnr, original_uid);
 
         /* Please update manager_default_environment() in core/manager.c accordingly if more session envvars
          * shall be added. */
@@ -1202,38 +1263,25 @@ _public_ PAM_EXTERN int pam_sm_open_session(
          * somewhere else (for example PAM module parameters). Let's now update the environment variables, so that this
          * data is inherited into the session processes, and programs can rely on them to be initialized. */
 
-        r = update_environment(handle, "XDG_SESSION_TYPE", type);
+        r = update_environment(handle, "XDG_SESSION_TYPE", c->type);
         if (r != PAM_SUCCESS)
                 return r;
 
-        r = update_environment(handle, "XDG_SESSION_CLASS", class);
+        r = update_environment(handle, "XDG_SESSION_CLASS", c->class);
         if (r != PAM_SUCCESS)
                 return r;
 
-        r = update_environment(handle, "XDG_SESSION_DESKTOP", desktop);
+        r = update_environment(handle, "XDG_SESSION_DESKTOP", c->desktop);
         if (r != PAM_SUCCESS)
                 return r;
 
-        r = update_environment(handle, "XDG_SEAT", seat);
+        r = update_environment(handle, "XDG_SEAT", real_seat);
         if (r != PAM_SUCCESS)
                 return r;
 
-        static const char *const propagate[] = {
+        if (real_vtnr > 0) {
-                "shell.prompt.prefix", "SHELL_PROMPT_PREFIX",
+                char buf[DECIMAL_STR_MAX(real_vtnr)];
-                "shell.prompt.suffix", "SHELL_PROMPT_SUFFIX",
+                sprintf(buf, "%u", real_vtnr);
-                "shell.welcome",       "SHELL_WELCOME",
-                NULL
-        };
-
-        STRV_FOREACH_PAIR(k, v, propagate) {
-                r = propagate_credential_to_environment(handle, *k, *v);
-                if (r != PAM_SUCCESS)
-                        return r;
-        }
-
-        if (vtnr > 0) {
-                char buf[DECIMAL_STR_MAX(vtnr)];
-                sprintf(buf, "%u", vtnr);
 
                 r = update_environment(handle, "XDG_VTNR", buf);
                 if (r != PAM_SUCCESS)
@@ -1255,9 +1303,118 @@ _public_ PAM_EXTERN int pam_sm_open_session(
                 TAKE_FD(fd);
         }
 
-success:
+        /* Everything worked, hence let's patch in the data we learned. Since 'real_set' points into the
+         * D-Bus message, let's copy it and return it as a buffer */
+        char *rs = NULL;
+        if (real_seat) {
+                rs = strdup(real_seat);
+                if (!rs)
+                        return pam_log_oom(handle);
+        }
+
+        c->seat = *ret_seat = rs;
+        c->vtnr = real_vtnr;
+
+        return PAM_SUCCESS;
+
+skip:
+        *ret_seat = NULL;
+        return PAM_SUCCESS;
+}
+
+static int import_shell_credentials(pam_handle_t *handle) {
+
+        static const char *const propagate[] = {
+                "shell.prompt.prefix", "SHELL_PROMPT_PREFIX",
+                "shell.prompt.suffix", "SHELL_PROMPT_SUFFIX",
+                "shell.welcome",       "SHELL_WELCOME",
+                NULL
+        };
+        int r;
+
+        assert(handle);
+
+        STRV_FOREACH_PAIR(k, v, propagate) {
+                r = propagate_credential_to_environment(handle, *k, *v);
+                if (r != PAM_SUCCESS)
+                        return r;
+        }
+
+        return PAM_SUCCESS;
+}
+
+_public_ PAM_EXTERN int pam_sm_open_session(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        int r;
+
+        assert(handle);
+
+        pam_log_setup();
+
+        uint64_t default_capability_bounding_set = UINT64_MAX, default_capability_ambient_set = UINT64_MAX;
+        const char *class_pam = NULL, *type_pam = NULL, *desktop_pam = NULL;
+        bool debug = false;
+        if (parse_argv(handle,
+                       argc, argv,
+                       &class_pam,
+                       &type_pam,
+                       &desktop_pam,
+                       &debug,
+                       &default_capability_bounding_set,
+                       &default_capability_ambient_set) < 0)
+                return PAM_SESSION_ERR;
+
+        pam_debug_syslog(handle, debug, "pam-systemd initializing");
+
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+        r = acquire_user_record(handle, &ur);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        SessionContext c = {};
+        r = pam_get_item_many(
+                        handle,
+                        PAM_SERVICE,  &c.service,
+                        PAM_XDISPLAY, &c.display,
+                        PAM_TTY,      &c.tty,
+                        PAM_RUSER,    &c.remote_user,
+                        PAM_RHOST,    &c.remote_host);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM items: @PAMERR@");
+
+        c.seat = getenv_harder(handle, "XDG_SEAT", NULL);
+        c.vtnr = getenv_harder_uint32(handle, "XDG_VTNR", 0);
+        c.type = getenv_harder(handle, "XDG_SESSION_TYPE", type_pam);
+        c.class = getenv_harder(handle, "XDG_SESSION_CLASS", class_pam);
+        c.desktop = getenv_harder(handle, "XDG_SESSION_DESKTOP", desktop_pam);
+        c.incomplete = getenv_harder_bool(handle, "XDG_SESSION_INCOMPLETE", false);
+
+        r = pam_get_data_many(
+                        handle,
+                        "systemd.memory_max",      &c.memory_max,
+                        "systemd.tasks_max",       &c.tasks_max,
+                        "systemd.cpu_weight",      &c.cpu_weight,
+                        "systemd.io_weight",       &c.io_weight,
+                        "systemd.runtime_max_sec", &c.runtime_max_sec);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM data: @PAMERR@");
+
+        session_context_mangle(handle, &c, ur, debug);
+
+        _cleanup_free_ char *seat_buffer = NULL;
+        r = register_session(handle, &c, ur, debug, &seat_buffer);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = import_shell_credentials(handle);
+        if (r != PAM_SUCCESS)
+                return r;
+
         if (default_capability_ambient_set == UINT64_MAX)
-                default_capability_ambient_set = pick_default_capability_ambient_set(ur, service, seat);
+                default_capability_ambient_set = pick_default_capability_ambient_set(ur, c.service, c.seat);
 
         return apply_user_record_settings(handle, ur, debug, default_capability_bounding_set, default_capability_ambient_set);
 }
@@ -1297,13 +1454,39 @@ _public_ PAM_EXTERN int pam_sm_close_session(
 
         id = pam_getenv(handle, "XDG_SESSION_ID");
         if (id && !existing) {
+                _cleanup_(sd_varlink_unrefp) sd_varlink *vl = NULL;
+                bool done = false;
+
+                r = sd_varlink_connect_address(&vl, "/run/systemd/io.systemd.Login");
+                if (r < 0)
+                        log_debug_errno(r, "Failed to connect to logind via Varlink, falling back to D-Bus: %m");
+                else {
+                        _cleanup_(sd_json_variant_unrefp) sd_json_variant *vreply = NULL;
+                        const char *error_id = NULL;
+                        r = sd_varlink_callbo(
+                                        vl,
+                                        "io.systemd.Login.ReleaseSession",
+                                        /* ret_reply= */ NULL,
+                                        &error_id,
+                                        SD_JSON_BUILD_PAIR_STRING("Id", id));
+                        if (r < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to register session: %s", error_id);
+                        if (error_id)
+                                return pam_syslog_errno(handle, LOG_ERR, sd_varlink_error_to_errno(error_id, vreply),
+                                                        "Failed to issue ReleaseSession() varlink call: %s", error_id);
+
+                        done = true;
+                }
+
+                if (!done) {
                         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+                        _cleanup_(pam_bus_data_disconnectp) PamBusData *d = NULL;
                         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 
                         /* Before we go and close the FIFO we need to tell logind that this is a clean session
                          * shutdown, so that it doesn't just go and slaughter us immediately after closing the fd */
 
-                r = pam_acquire_bus_connection(handle, "pam-systemd", debug, &bus, NULL);
+                        r = pam_acquire_bus_connection(handle, "pam-systemd", debug, &bus, &d);
                         if (r != PAM_SUCCESS)
                                 return r;
 
@@ -1312,6 +1495,7 @@ _public_ PAM_EXTERN int pam_sm_close_session(
                                 return pam_syslog_pam_error(handle, LOG_ERR, PAM_SESSION_ERR,
                                                             "Failed to release session: %s", bus_error_message(&error, r));
                 }
+        }
 
         /* Note that we are knowingly leaking the FIFO fd here. This way, logind can watch us die. If we
          * closed it here it would not have any clue when that is completed. Given that one cannot really

src/network/networkd-link.c

@@ -1443,6 +1443,7 @@ int link_reconfigure_impl(Link *link, LinkReconfigurationFlag flags) {
 }
 
 typedef struct LinkReconfigurationData {
+        Manager *manager;
         Link *link;
         LinkReconfigurationFlag flags;
         sd_bus_message *message;
@@ -1473,6 +1474,12 @@ static void link_reconfiguration_data_destroy_callback(LinkReconfigurationData *
                 }
 
                 if (!data->counter || *data->counter <= 0) {
+                        /* Update the state files before replying the bus method. Otherwise,
+                         * systemd-networkd-wait-online following networkctl reload/reconfigure may read an
+                         * outdated state file and wrongly handle an interface is already in the configured
+                         * state. */
+                        (void) manager_clean_all(data->manager);
+
                         r = sd_bus_reply_method_return(data->message, NULL);
                         if (r < 0)
                                 log_warning_errno(r, "Failed to reply for DBus method, ignoring: %m");
@@ -1521,6 +1528,7 @@ int link_reconfigure_full(Link *link, LinkReconfigurationFlag flags, sd_bus_mess
         }
 
         *data = (LinkReconfigurationData) {
+                .manager = link->manager,
                 .link = link_ref(link),
                 .flags = flags,
                 .message = sd_bus_message_ref(message), /* message may be NULL, but _ref() works fine. */

src/shared/meson.build

@@ -182,6 +182,7 @@ shared_sources = files(
         'varlink-io.systemd.Hostname.c',
         'varlink-io.systemd.Import.c',
         'varlink-io.systemd.Journal.c',
+        'varlink-io.systemd.Login.c',
         'varlink-io.systemd.Machine.c',
         'varlink-io.systemd.MachineImage.c',
         'varlink-io.systemd.ManagedOOM.c',

src/shared/pam-util.c

@@ -253,17 +253,17 @@ int pam_get_item_many_internal(pam_handle_t *handle, ...) {
         va_list ap;
         int r;
 
+        assert(handle);
+
         va_start(ap, handle);
         for (;;) {
                 int item_type = va_arg(ap, int);
-
                 if (item_type <= 0) {
                         r = PAM_SUCCESS;
                         break;
                 }
 
                 const void **value = ASSERT_PTR(va_arg(ap, const void **));
-
                 r = pam_get_item(handle, item_type, value);
                 if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
                         break;
@@ -273,6 +273,30 @@ int pam_get_item_many_internal(pam_handle_t *handle, ...) {
         return r;
 }
 
+int pam_get_data_many_internal(pam_handle_t *handle, ...) {
+        va_list ap;
+        int r;
+
+        assert(handle);
+
+        va_start(ap, handle);
+        for (;;) {
+                const char *data_name = va_arg(ap, const char *);
+                if (!data_name) {
+                        r = PAM_SUCCESS;
+                        break;
+                }
+
+                const void **value = ASSERT_PTR(va_arg(ap, const void **));
+                r = pam_get_data(handle, data_name, value);
+                if (!IN_SET(r, PAM_NO_MODULE_DATA, PAM_SUCCESS))
+                        break;
+        }
+        va_end(ap);
+
+        return r;
+}
+
 int pam_prompt_graceful(pam_handle_t *handle, int style, char **ret_response, const char *fmt, ...) {
         va_list args;
         int r;

src/shared/pam-util.h

@@ -44,7 +44,9 @@ int pam_get_bus_data(pam_handle_t *handle, const char *module_name, PamBusData *
 void pam_cleanup_free(pam_handle_t *handle, void *data, int error_status);
 
 int pam_get_item_many_internal(pam_handle_t *handle, ...);
-
 #define pam_get_item_many(handle, ...) pam_get_item_many_internal(handle, __VA_ARGS__, -1)
 
+int pam_get_data_many_internal(pam_handle_t *handle, ...);
+#define pam_get_data_many(handle, ...) pam_get_data_many_internal(handle, __VA_ARGS__, NULL)
+
 int pam_prompt_graceful(pam_handle_t *handle, int style, char **ret_response, const char *fmt, ...) _printf_(4,5);

src/shared/varlink-io.systemd.Login.c

@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "bus-polkit.h"
+#include "varlink-io.systemd.Login.h"
+
+static SD_VARLINK_DEFINE_ENUM_TYPE(
+                SessionType,
+                SD_VARLINK_DEFINE_ENUM_VALUE(unspecified),
+                SD_VARLINK_DEFINE_ENUM_VALUE(tty),
+                SD_VARLINK_DEFINE_ENUM_VALUE(x11),
+                SD_VARLINK_DEFINE_ENUM_VALUE(wayland),
+                SD_VARLINK_DEFINE_ENUM_VALUE(mir),
+                SD_VARLINK_DEFINE_ENUM_VALUE(web));
+
+static SD_VARLINK_DEFINE_ENUM_TYPE(
+                SessionClass,
+                SD_VARLINK_DEFINE_ENUM_VALUE(user),
+                SD_VARLINK_DEFINE_ENUM_VALUE(user_early),
+                SD_VARLINK_DEFINE_ENUM_VALUE(user_incomplete),
+                SD_VARLINK_DEFINE_ENUM_VALUE(greeter),
+                SD_VARLINK_DEFINE_ENUM_VALUE(lock_screen),
+                SD_VARLINK_DEFINE_ENUM_VALUE(background),
+                SD_VARLINK_DEFINE_ENUM_VALUE(background_light),
+                SD_VARLINK_DEFINE_ENUM_VALUE(manager),
+                SD_VARLINK_DEFINE_ENUM_VALUE(manager_early));
+
+static SD_VARLINK_DEFINE_METHOD(
+                CreateSession,
+                SD_VARLINK_FIELD_COMMENT("Numeric UNIX UID of the user this session shall be owned by"),
+                SD_VARLINK_DEFINE_INPUT(UID, SD_VARLINK_INT, 0),
+                SD_VARLINK_FIELD_COMMENT("PAM service name of the program requesting the session"),
+                SD_VARLINK_DEFINE_INPUT(Service, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_FIELD_COMMENT("The type of session"),
+                SD_VARLINK_DEFINE_INPUT_BY_TYPE(Type, SessionType, 0),
+                SD_VARLINK_DEFINE_INPUT_BY_TYPE(Class, SessionClass, 0),
+                SD_VARLINK_DEFINE_INPUT(Desktop, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(Seat, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(VTNr, SD_VARLINK_INT, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(TTY, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(Display, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(Remote, SD_VARLINK_BOOL, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(RemoteUser, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(RemoteHost, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_FIELD_COMMENT("The identifier string of the session of the user."),
+                SD_VARLINK_DEFINE_OUTPUT(Id, SD_VARLINK_STRING, 0),
+                SD_VARLINK_FIELD_COMMENT("The runtime path ($XDG_RUNTIME_DIR) of the user."),
+                SD_VARLINK_DEFINE_OUTPUT(RuntimePath, SD_VARLINK_STRING, 0),
+                SD_VARLINK_FIELD_COMMENT("Index into the file descriptor table of this reply with the session tracking fd for this session."),
+                SD_VARLINK_DEFINE_OUTPUT(SessionFileDescriptor, SD_VARLINK_INT, 0),
+                SD_VARLINK_FIELD_COMMENT("The original UID of this session."),
+                SD_VARLINK_DEFINE_OUTPUT(UID, SD_VARLINK_INT, 0),
+                SD_VARLINK_FIELD_COMMENT("The seat this session has been assigned to"),
+                SD_VARLINK_DEFINE_OUTPUT(Seat, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_FIELD_COMMENT("The virtual terminal number the session has been assigned to"),
+                SD_VARLINK_DEFINE_OUTPUT(VTNr, SD_VARLINK_INT, SD_VARLINK_NULLABLE));
+
+static SD_VARLINK_DEFINE_METHOD(
+                ReleaseSession,
+                SD_VARLINK_FIELD_COMMENT("The identifier string of the session to release. If unspecified or 'self', will return the callers session."),
+                SD_VARLINK_DEFINE_INPUT(Id, SD_VARLINK_STRING, SD_VARLINK_NULLABLE));
+
+static SD_VARLINK_DEFINE_ERROR(NoSuchSession);
+static SD_VARLINK_DEFINE_ERROR(NoSuchSeat);
+static SD_VARLINK_DEFINE_ERROR(AlreadySessionMember);
+static SD_VARLINK_DEFINE_ERROR(VirtualTerminalAlreadyTaken);
+static SD_VARLINK_DEFINE_ERROR(TooManySessions);
+static SD_VARLINK_DEFINE_ERROR(UnitAllocationFailed);
+
+SD_VARLINK_DEFINE_INTERFACE(
+                io_systemd_Login,
+                "io.systemd.Login",
+                SD_VARLINK_INTERFACE_COMMENT("APIs for managing login sessions."),
+                SD_VARLINK_SYMBOL_COMMENT("Various types of sessions"),
+                &vl_type_SessionType,
+                SD_VARLINK_SYMBOL_COMMENT("Various classes of sessions"),
+                &vl_type_SessionClass,
+                SD_VARLINK_SYMBOL_COMMENT("Allocates a new session."),
+                &vl_method_CreateSession,
+                SD_VARLINK_SYMBOL_COMMENT("Releases an existing session. Currently, will be refuses unless originating from the session to release itself."),
+                &vl_method_ReleaseSession,
+                SD_VARLINK_SYMBOL_COMMENT("No session by this name found"),
+                &vl_error_NoSuchSession,
+                SD_VARLINK_SYMBOL_COMMENT("No seat by this name found"),
+                &vl_error_NoSuchSeat,
+                SD_VARLINK_SYMBOL_COMMENT("Process already member of a session"),
+                &vl_error_AlreadySessionMember,
+                SD_VARLINK_SYMBOL_COMMENT("The specified virtual terminal (VT) is already taken by another session"),
+                &vl_error_VirtualTerminalAlreadyTaken,
+                SD_VARLINK_SYMBOL_COMMENT("Maximum number of sessions reached"),
+                &vl_error_TooManySessions,
+                SD_VARLINK_SYMBOL_COMMENT("Failed to allocate a unit for the session"),
+                &vl_error_UnitAllocationFailed);

src/shared/varlink-io.systemd.Login.h

@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-varlink-idl.h"
+
+extern const sd_varlink_interface vl_interface_io_systemd_Login;

src/systemd/sd-varlink.h

@@ -70,6 +70,8 @@ __extension__ typedef enum _SD_ENUM_TYPE_S64(sd_varlink_server_flags_t) {
         SD_VARLINK_SERVER_ACCOUNT_UID             = 1 << 2, /* Do per user accounting */
         SD_VARLINK_SERVER_INHERIT_USERDATA        = 1 << 3, /* Initialize Varlink connection userdata from sd_varlink_server userdata */
         SD_VARLINK_SERVER_INPUT_SENSITIVE         = 1 << 4, /* Automatically mark all connection input as sensitive */
+        SD_VARLINK_SERVER_ALLOW_FD_PASSING_INPUT  = 1 << 5, /* Allow receiving fds over all connections */
+        SD_VARLINK_SERVER_ALLOW_FD_PASSING_OUTPUT = 1 << 6, /* Allow sending fds over all connections */
         _SD_ENUM_FORCE_S64(SD_VARLINK_SERVER)
 } sd_varlink_server_flags_t;
 

src/test/test-cgroup-util.c

@@ -212,8 +212,8 @@ TEST(proc) {
 
                 cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid.pid, &path);
                 cg_pid_get_path_shifted(pid.pid, NULL, &path_shifted);
-                cg_pid_get_owner_uid(pid.pid, &uid);
+                cg_pidref_get_owner_uid(&pid, &uid);
-                cg_pid_get_session(pid.pid, &session);
+                cg_pidref_get_session(&pid, &session);
                 cg_pid_get_unit(pid.pid, &unit);
                 cg_pid_get_user_unit(pid.pid, &user_unit);
                 cg_pid_get_machine_name(pid.pid, &machine);

src/test/test-varlink-idl.c

@@ -14,6 +14,7 @@
 #include "varlink-io.systemd.Credentials.h"
 #include "varlink-io.systemd.Import.h"
 #include "varlink-io.systemd.Journal.h"
+#include "varlink-io.systemd.Login.h"
 #include "varlink-io.systemd.Machine.h"
 #include "varlink-io.systemd.MachineImage.h"
 #include "varlink-io.systemd.ManagedOOM.h"
@@ -193,6 +194,8 @@ TEST(parse_format) {
         print_separator();
         test_parse_format_one(&vl_interface_io_systemd_MachineImage);
         print_separator();
+        test_parse_format_one(&vl_interface_io_systemd_Login);
+        print_separator();
         test_parse_format_one(&vl_interface_xyz_test);
 }
 

test/test-network/systemd-networkd-tests.py

@@ -6406,11 +6406,11 @@ class NetworkdRATests(unittest.TestCase, Utilities):
 
         for i in [100, 200, 300, 512, 1024, 2048]:
             if i not in [metric_1, metric_2]:
-                self.assertNotIn(f'{i}', output)
+                self.assertNotIn(f'metric {i} ', output)
 
         for i in ['low', 'medium', 'high']:
             if i not in [preference_1, preference_2]:
-                self.assertNotIn(f'{i}', output)
+                self.assertNotIn(f'pref {i}', output)
 
     def test_router_preference(self):
         copy_network_unit('25-veth-client.netdev',