cgroup: remove support for NetClass= directive

Support for net_cls.class_id through the NetClass= configuration directive
has been added in v227 in preparation for a per-unit packet filter mechanism.
However, it turns out the kernel people have decided to deprecate the net_cls
and net_prio controllers in v2. Tejun provides a comprehensive justification
for this in his commit, which has landed during the merge window for kernel
v4.5:

  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bd1060a1d671

As we're aiming for full support for the v2 cgroup hierarchy, we can no
longer support this feature. Userspace tool such as nftables are moving over
to setting rules that are specific to the full cgroup path of a task, which
obsoletes these controllers anyway.

This commit removes support for tweaking details in the net_cls controller,
but keeps the NetClass= directive around for legacy compatibility reasons.

13 files changed, 16 insertions, 237 deletions

diff --git a/NEWS b/NEWS
index 51c0faefd5..0a5fdd7cd3 100644
--- a/NEWS
+++ b/NEWS
@@ -97,6 +97,17 @@ CHANGES WITH 229:
           initrd, this part of the logic remains in timesyncd, and is not done
           by PID 1.
 
+        * Support for tweaking details in net_cls.class_id through the
+          NetClass= configuration directive has been removed, as the kernel
+          people have decided to deprecate that controller in cgroup v2.
+          Userspace tools such as nftables are moving over to setting rules
+          that are specific to the full cgroup path of a task, which obsoletes
+          these controllers anyway. The NetClass= directive is kept around for
+          legacy compatibility reasons. For a more in-depth description of the
+          kernel change, please refer to the respective upstream commit:
+
+            https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bd1060a1d671
+
         * A new service setting RuntimeMaxSec= has been added that may be used
           to specify a maximum runtime for a service. If the timeout is hit, the
           service is terminated and put into a failure state.
diff --git a/man/systemd.resource-control.xml b/man/systemd.resource-control.xml
index b6b38fde58..08cdf06e23 100644
--- a/man/systemd.resource-control.xml
+++ b/man/systemd.resource-control.xml
@@ -424,23 +424,6 @@
       </varlistentry>
 
       <varlistentry>
-        <term><varname>NetClass=</varname></term>
-        <listitem><para>Configures a network class number to assign to the
-        unit. This value will be set to the
-        <literal>net_cls.class_id</literal> property of the
-        <literal>net_cls</literal> cgroup of the unit. The directive
-        accepts a numerical value (for fixed number assignment) and the keyword
-        <literal>auto</literal> (for dynamic allocation). Network traffic of
-        all processes inside the unit will have the network class ID assigned
-        by the kernel. Also see
-        the kernel docs for
-        <ulink url="https://www.kernel.org/doc/Documentation/cgroups/net_cls.txt">net_cls controller</ulink>
-        and
-        <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
-        </para></listitem>
-      </varlistentry>
-
-      <varlistentry>
         <term><varname>Slice=</varname></term>
 
         <listitem>
diff --git a/shell-completion/zsh/_systemd b/shell-completion/zsh/_systemd
index 05459dc5f6..62114ff095 100644
--- a/shell-completion/zsh/_systemd
+++ b/shell-completion/zsh/_systemd
@@ -27,7 +27,7 @@ case "$service" in
             '--no-pager[Do not pipe output into a pager]' \
             {-a,--all}'[Show all groups, including empty]' \
             '-k[Include kernel threads in output]' \
-            ':cgroups:(cpuset cpu cpuacct memory devices freezer net_cls blkio)'
+            ':cgroups:(cpuset cpu cpuacct memory devices freezer blkio)'
     ;;
     systemd-cgtop)
         _arguments \
diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index b47748f982..6ef00d51df 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -2269,7 +2269,6 @@ static const char *cgroup_controller_table[_CGROUP_CONTROLLER_MAX] = {
         [CGROUP_CONTROLLER_MEMORY] = "memory",
         [CGROUP_CONTROLLER_DEVICES] = "devices",
         [CGROUP_CONTROLLER_PIDS] = "pids",
-        [CGROUP_CONTROLLER_NET_CLS] = "net_cls",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(cgroup_controller, CGroupController);
diff --git a/src/basic/cgroup-util.h b/src/basic/cgroup-util.h
index 42807576b5..ad1edd9cdb 100644
--- a/src/basic/cgroup-util.h
+++ b/src/basic/cgroup-util.h
@@ -38,7 +38,6 @@ typedef enum CGroupController {
         CGROUP_CONTROLLER_MEMORY,
         CGROUP_CONTROLLER_DEVICES,
         CGROUP_CONTROLLER_PIDS,
-        CGROUP_CONTROLLER_NET_CLS,
         _CGROUP_CONTROLLER_MAX,
         _CGROUP_CONTROLLER_INVALID = -1,
 } CGroupController;
@@ -53,7 +52,6 @@ typedef enum CGroupMask {
         CGROUP_MASK_MEMORY = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_MEMORY),
         CGROUP_MASK_DEVICES = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_DEVICES),
         CGROUP_MASK_PIDS = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_PIDS),
-        CGROUP_MASK_NET_CLS = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_NET_CLS),
         _CGROUP_MASK_ALL = CGROUP_CONTROLLER_TO_MASK(_CGROUP_CONTROLLER_MAX) - 1
 } CGroupMask;
 
diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 7a6a4024e5..39235a95f6 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -51,8 +51,6 @@ void cgroup_context_init(CGroupContext *c) {
         c->startup_blockio_weight = CGROUP_BLKIO_WEIGHT_INVALID;
 
         c->tasks_max = (uint64_t) -1;
-
-        c->netclass_type = CGROUP_NETCLASS_TYPE_NONE;
 }
 
 void cgroup_context_free_device_allow(CGroupContext *c, CGroupDeviceAllow *a) {
@@ -297,7 +295,7 @@ fail:
         return -errno;
 }
 
-void cgroup_context_apply(CGroupContext *c, CGroupMask mask, const char *path, uint32_t netclass, ManagerState state) {
+void cgroup_context_apply(CGroupContext *c, CGroupMask mask, const char *path, ManagerState state) {
         bool is_root;
         int r;
 
@@ -495,17 +493,6 @@ void cgroup_context_apply(CGroupContext *c, CGroupMask mask, const char *path, u
                         log_full_errno(IN_SET(r, -ENOENT, -EROFS, -EACCES) ? LOG_DEBUG : LOG_WARNING, r,
                                        "Failed to set pids.max on %s: %m", path);
         }
-
-        if (mask & CGROUP_MASK_NET_CLS) {
-                char buf[DECIMAL_STR_MAX(uint32_t)];
-
-                sprintf(buf, "%" PRIu32, netclass);
-
-                r = cg_set_attribute("net_cls", path, "net_cls.classid", buf);
-                if (r < 0)
-                        log_full_errno(IN_SET(r, -ENOENT, -EROFS, -EACCES) ? LOG_DEBUG : LOG_WARNING, r,
-                                       "Failed to set net_cls.classid on %s: %m", path);
-        }
 }
 
 CGroupMask cgroup_context_get_mask(CGroupContext *c) {
@@ -538,9 +525,6 @@ CGroupMask cgroup_context_get_mask(CGroupContext *c) {
             c->tasks_max != (uint64_t) -1)
                 mask |= CGROUP_MASK_PIDS;
 
-        if (c->netclass_type != CGROUP_NETCLASS_TYPE_NONE)
-                mask |= CGROUP_MASK_NET_CLS;
-
         return mask;
 }
 
@@ -908,103 +892,6 @@ static bool unit_has_mask_realized(Unit *u, CGroupMask target_mask) {
         return u->cgroup_realized && u->cgroup_realized_mask == target_mask;
 }
 
-static int unit_find_free_netclass_cgroup(Unit *u, uint32_t *ret) {
-
-        uint32_t start, i;
-        Manager *m;
-
-        assert(u);
-
-        m = u->manager;
-
-        i = start = m->cgroup_netclass_registry_last;
-
-        do {
-                i++;
-
-                if (!hashmap_get(m->cgroup_netclass_registry, UINT_TO_PTR(i))) {
-                        m->cgroup_netclass_registry_last = i;
-                        *ret = i;
-                        return 0;
-                }
-
-                if (i == UINT32_MAX)
-                        i = CGROUP_NETCLASS_FIXED_MAX;
-
-        } while (i != start);
-
-        return -ENOBUFS;
-}
-
-int unit_add_to_netclass_cgroup(Unit *u) {
-
-        CGroupContext *cc;
-        Unit *first;
-        void *key;
-        int r;
-
-        assert(u);
-
-        cc = unit_get_cgroup_context(u);
-        if (!cc)
-                return 0;
-
-        switch (cc->netclass_type) {
-        case CGROUP_NETCLASS_TYPE_NONE:
-                return 0;
-
-        case CGROUP_NETCLASS_TYPE_FIXED:
-                u->cgroup_netclass_id = cc->netclass_id;
-                break;
-
-        case CGROUP_NETCLASS_TYPE_AUTO:
-                /* Allocate a new ID in case it was requested and not done yet */
-                if (u->cgroup_netclass_id == 0) {
-                        r = unit_find_free_netclass_cgroup(u, &u->cgroup_netclass_id);
-                        if (r < 0)
-                                return r;
-
-                        log_debug("Dynamically assigned netclass cgroup id %" PRIu32 " to %s", u->cgroup_netclass_id, u->id);
-                }
-
-                break;
-        }
-
-        r = hashmap_ensure_allocated(&u->manager->cgroup_netclass_registry, &trivial_hash_ops);
-        if (r < 0)
-                return r;
-
-        key = UINT32_TO_PTR(u->cgroup_netclass_id);
-        first = hashmap_get(u->manager->cgroup_netclass_registry, key);
-
-        if (first) {
-                LIST_PREPEND(cgroup_netclass, first, u);
-                return hashmap_replace(u->manager->cgroup_netclass_registry, key, u);
-        }
-
-        return hashmap_put(u->manager->cgroup_netclass_registry, key, u);
-}
-
-int unit_remove_from_netclass_cgroup(Unit *u) {
-
-        Unit *head;
-        void *key;
-
-        assert(u);
-
-        key = UINT32_TO_PTR(u->cgroup_netclass_id);
-
-        LIST_FIND_HEAD(cgroup_netclass, u, head);
-        LIST_REMOVE(cgroup_netclass, head, u);
-
-        if (head)
-                return hashmap_replace(u->manager->cgroup_netclass_registry, key, head);
-
-        hashmap_remove(u->manager->cgroup_netclass_registry, key);
-
-        return 0;
-}
-
 /* Check if necessary controllers and attributes for a unit are in place.
  *
  * If so, do nothing.
@@ -1040,7 +927,7 @@ static int unit_realize_cgroup_now(Unit *u, ManagerState state) {
                 return r;
 
         /* Finally, apply the necessary attributes. */
-        cgroup_context_apply(unit_get_cgroup_context(u), target_mask, u->cgroup_path, u->cgroup_netclass_id, state);
+        cgroup_context_apply(unit_get_cgroup_context(u), target_mask, u->cgroup_path, state);
 
         return 0;
 }
diff --git a/src/core/cgroup.h b/src/core/cgroup.h
index 2157cffe9d..360bbca30f 100644
--- a/src/core/cgroup.h
+++ b/src/core/cgroup.h
@@ -24,11 +24,6 @@
 #include "list.h"
 #include "time-util.h"
 
-/* Maximum value for fixed (manual) net class ID assignment,
- * and also the value at which the range of automatic assignments starts
- */
-#define CGROUP_NETCLASS_FIXED_MAX UINT32_C(65535)
-
 typedef struct CGroupContext CGroupContext;
 typedef struct CGroupDeviceAllow CGroupDeviceAllow;
 typedef struct CGroupBlockIODeviceWeight CGroupBlockIODeviceWeight;
@@ -50,17 +45,6 @@ typedef enum CGroupDevicePolicy {
         _CGROUP_DEVICE_POLICY_INVALID = -1
 } CGroupDevicePolicy;
 
-typedef enum CGroupNetClassType {
-        /* Default - do not assign a net class */
-        CGROUP_NETCLASS_TYPE_NONE,
-
-        /* Automatically assign a net class */
-        CGROUP_NETCLASS_TYPE_AUTO,
-
-        /* Assign the net class that was provided by the user */
-        CGROUP_NETCLASS_TYPE_FIXED,
-} CGroupNetClassType;
-
 struct CGroupDeviceAllow {
         LIST_FIELDS(CGroupDeviceAllow, device_allow);
         char *path;
@@ -102,9 +86,6 @@ struct CGroupContext {
         CGroupDevicePolicy device_policy;
         LIST_HEAD(CGroupDeviceAllow, device_allow);
 
-        CGroupNetClassType netclass_type;
-        uint32_t netclass_id;
-
         uint64_t tasks_max;
 
         bool delegate;
@@ -116,7 +97,7 @@ struct CGroupContext {
 void cgroup_context_init(CGroupContext *c);
 void cgroup_context_done(CGroupContext *c);
 void cgroup_context_dump(CGroupContext *c, FILE* f, const char *prefix);
-void cgroup_context_apply(CGroupContext *c, CGroupMask mask, const char *path, uint32_t netclass_id, ManagerState state);
+void cgroup_context_apply(CGroupContext *c, CGroupMask mask, const char *path, ManagerState state);
 
 CGroupMask cgroup_context_get_mask(CGroupContext *c);
 
@@ -144,9 +125,6 @@ int unit_watch_cgroup(Unit *u);
 
 int unit_attach_pids_to_cgroup(Unit *u);
 
-int unit_add_to_netclass_cgroup(Unit *u);
-int unit_remove_from_netclass_cgroup(Unit *u);
-
 int manager_setup_cgroup(Manager *m);
 void manager_shutdown_cgroup(Manager *m, bool delete);
 
diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index 33da1a61e9..b351f6a2c2 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -701,7 +701,6 @@ const sd_bus_vtable bus_unit_vtable[] = {
         SD_BUS_PROPERTY("Asserts", "a(sbbsi)", property_get_conditions, offsetof(Unit, asserts), 0),
         SD_BUS_PROPERTY("LoadError", "(ss)", property_get_load_error, 0, SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("Transient", "b", bus_property_get_bool, offsetof(Unit, transient), SD_BUS_VTABLE_PROPERTY_CONST),
-        SD_BUS_PROPERTY("NetClass", "u", NULL, offsetof(Unit, cgroup_netclass_id), 0),
         SD_BUS_PROPERTY("StartLimitInterval", "t", bus_property_get_usec, offsetof(Unit, start_limit.interval), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("StartLimitBurst", "u", bus_property_get_unsigned, offsetof(Unit, start_limit.burst), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("StartLimitAction", "s", property_get_failure_action, offsetof(Unit, start_limit_action), SD_BUS_VTABLE_PROPERTY_CONST),
diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index c2a47c7b11..8f7aa35b8f 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -129,7 +129,7 @@ $1.BlockIOWriteBandwidth,        config_parse_blockio_bandwidth,     0,
 $1.TasksAccounting,              config_parse_bool,                  0,                             offsetof($1, cgroup_context.tasks_accounting)
 $1.TasksMax,                     config_parse_tasks_max,             0,                             offsetof($1, cgroup_context.tasks_max)
 $1.Delegate,                     config_parse_bool,                  0,                             offsetof($1, cgroup_context.delegate)
-$1.NetClass,                     config_parse_netclass,              0,                             offsetof($1, cgroup_context)'
+$1.NetClass,                     config_parse_warn_compat,           DISABLED_LEGACY,               0'
 )m4_dnl
 Unit.Description,                config_parse_unit_string_printf,    0,                             offsetof(Unit, description)
 Unit.Documentation,              config_parse_documentation,         0,                             offsetof(Unit, documentation)
diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 8e5ef935f7..5a71fc0dda 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -3122,47 +3122,6 @@ int config_parse_blockio_bandwidth(
         return 0;
 }
 
-int config_parse_netclass(
-                const char *unit,
-                const char *filename,
-                unsigned line,
-                const char *section,
-                unsigned section_line,
-                const char *lvalue,
-                int ltype,
-                const char *rvalue,
-                void *data,
-                void *userdata) {
-
-        CGroupContext *c = data;
-        unsigned v;
-        int r;
-
-        assert(filename);
-        assert(lvalue);
-        assert(rvalue);
-
-        if (streq(rvalue, "auto")) {
-                c->netclass_type = CGROUP_NETCLASS_TYPE_AUTO;
-                return 0;
-        }
-
-        r = safe_atou32(rvalue, &v);
-        if (r < 0) {
-                log_syntax(unit, LOG_ERR, filename, line, r, "Netclass '%s' invalid. Ignoring.", rvalue);
-                return 0;
-        }
-
-        if (v > CGROUP_NETCLASS_FIXED_MAX)
-                log_syntax(unit, LOG_ERR, filename, line, 0,
-                           "Fixed netclass %" PRIu32 " out of allowed range (0-%d). Applying anyway.", v, (uint32_t) CGROUP_NETCLASS_FIXED_MAX);
-
-        c->netclass_id = v;
-        c->netclass_type = CGROUP_NETCLASS_TYPE_FIXED;
-
-        return 0;
-}
-
 DEFINE_CONFIG_PARSE_ENUM(config_parse_job_mode, job_mode, JobMode, "Failed to parse job mode");
 
 int config_parse_job_mode_isolate(
diff --git a/src/core/manager.c b/src/core/manager.c
index 9aa7e8af38..f36cf5e320 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -596,8 +596,6 @@ int manager_new(ManagerRunningAs running_as, bool test_run, Manager **_m) {
         m->have_ask_password = -EINVAL; /* we don't know */
         m->first_boot = -1;
 
-        m->cgroup_netclass_registry_last = CGROUP_NETCLASS_FIXED_MAX;
-
         m->test_run = test_run;
 
         /* Reboot immediately if the user hits C-A-D more often than 7x per 2s */
@@ -981,8 +979,6 @@ Manager* manager_free(Manager *m) {
         hashmap_free(m->cgroup_unit);
         set_free_free(m->unit_path_cache);
 
-        hashmap_free(m->cgroup_netclass_registry);
-
         free(m->switch_root);
         free(m->switch_root_init);
 
diff --git a/src/core/manager.h b/src/core/manager.h
index 5b226bc084..9803f73129 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -305,10 +305,6 @@ struct Manager {
         const char *unit_log_format_string;
 
         int first_boot;
-
-        /* Used for NetClass=auto units */
-        Hashmap *cgroup_netclass_registry;
-        uint32_t cgroup_netclass_registry_last;
 };
 
 int manager_new(ManagerRunningAs running_as, bool test_run, Manager **m);
diff --git a/src/core/unit.c b/src/core/unit.c
index ffefae2b94..d39e3dcaeb 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -458,7 +458,6 @@ static void unit_free_requires_mounts_for(Unit *u) {
 static void unit_done(Unit *u) {
         ExecContext *ec;
         CGroupContext *cc;
-        int r;
 
         assert(u);
 
@@ -475,10 +474,6 @@ static void unit_done(Unit *u) {
         cc = unit_get_cgroup_context(u);
         if (cc)
                 cgroup_context_done(cc);
-
-        r = unit_remove_from_netclass_cgroup(u);
-        if (r < 0)
-                log_warning_errno(r, "Unable to remove unit from netclass group: %m");
 }
 
 void unit_free(Unit *u) {
@@ -1263,14 +1258,6 @@ int unit_load(Unit *u) {
                 }
 
                 unit_update_cgroup_members_masks(u);
-
-                /* If we are reloading, we need to wait for the deserializer
-                 * to restore the net_cls ids that have been set previously */
-                if (u->manager->n_reloading <= 0) {
-                        r = unit_add_to_netclass_cgroup(u);
-                        if (r < 0)
-                                return r;
-                }
         }
 
         assert((u->load_state != UNIT_MERGED) == !u->merged_into);
@@ -2601,9 +2588,6 @@ int unit_serialize(Unit *u, FILE *f, FDSet *fds, bool serialize_jobs) {
                 unit_serialize_item(u, f, "cgroup", u->cgroup_path);
         unit_serialize_item(u, f, "cgroup-realized", yes_no(u->cgroup_realized));
 
-        if (u->cgroup_netclass_id)
-                unit_serialize_item_format(u, f, "netclass-id", "%" PRIu32, u->cgroup_netclass_id);
-
         if (serialize_jobs) {
                 if (u->job) {
                         fprintf(f, "job\n");
@@ -2841,17 +2825,6 @@ int unit_deserialize(Unit *u, FILE *f, FDSet *fds) {
                                 u->cgroup_realized = b;
 
                         continue;
-                } else if (streq(l, "netclass-id")) {
-                        r = safe_atou32(v, &u->cgroup_netclass_id);
-                        if (r < 0)
-                                log_unit_debug(u, "Failed to parse netclass ID %s, ignoring.", v);
-                        else {
-                                r = unit_add_to_netclass_cgroup(u);
-                                if (r < 0)
-                                        log_unit_debug_errno(u, r, "Failed to add unit to netclass cgroup, ignoring: %m");
-                        }
-
-                        continue;
                 }
 
                 if (unit_can_serialize(u)) {