network: TC - introduce DRR

Introduce the Deficit Round Robin Scheduler is a classful queuing discipline as
a more flexible replacement for Stochastic Fairness Queuing.

http://man7.org/linux/man-pages/man8/tc-drr.8.html

man/systemd.network.xml

@@ -2739,6 +2739,32 @@
     </variablelist>
   </refsect1>
 
+  <refsect1>
+    <title>[DeficitRoundRobinScheduler] Section Options</title>
+    <para>The <literal>[DeficitRoundRobinScheduler]</literal> section manages the queueing discipline (qdisc) of
+    Deficit Round Robin Scheduler (DRR).</para>
+
+    <variablelist class='network-directives'>
+      <varlistentry>
+        <term><varname>Parent=</varname></term>
+        <listitem>
+          <para>Specifies the parent Queueing Discipline (qdisc). Takes one of <literal>root</literal>,
+          <literal>clsact</literal>, <literal>ingress</literal> or a class id. The class id takes the
+          major and minor number in hexadecimal ranges 1 to ffff separated with a colon
+          (<literal>major:minor</literal>). Defaults to <literal>root</literal>.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>Handle=</varname></term>
+        <listitem>
+          <para>Specifies the major number of unique identifier of the qdisc, known as the handle.
+          Takes a number in hexadecimal ranges 1 to ffff. Defaults to unset.</para>
+        </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
   <refsect1>
     <title>[GenericRandomEarlyDetection] Section Options</title>
     <para>The <literal>[GenericRandomEarlyDetection]</literal> section manages the queueing discipline

src/network/meson.build

@@ -111,6 +111,8 @@ sources = files('''
         tc/cake.h
         tc/codel.c
         tc/codel.h
+        tc/drr.c
+        tc/drr.h
         tc/fifo.c
         tc/fifo.h
         tc/fq.c

src/network/networkd-network-gperf.gperf

@@ -269,6 +269,8 @@ ControlledDelay.TargetSec,                   config_parse_controlled_delay_usec,
 ControlledDelay.IntervalSec,                 config_parse_controlled_delay_usec,                       QDISC_KIND_CODEL,              0
 ControlledDelay.CEThresholdSec,              config_parse_controlled_delay_usec,                       QDISC_KIND_CODEL,              0
 ControlledDelay.ECN,                         config_parse_controlled_delay_bool,                       QDISC_KIND_CODEL,              0
+DeficitRoundRobinScheduler.Parent,           config_parse_qdisc_parent,                                QDISC_KIND_DRR,                0
+DeficitRoundRobinScheduler.Handle,           config_parse_qdisc_handle,                                QDISC_KIND_DRR,                0
 PFIFO.Parent,                                config_parse_qdisc_parent,                                QDISC_KIND_PFIFO,              0
 PFIFO.Handle,                                config_parse_qdisc_handle,                                QDISC_KIND_PFIFO,              0
 PFIFO.PacketLimit,                           config_parse_fifo_size,                                   QDISC_KIND_PFIFO,              0

src/network/networkd-network.c

@@ -488,6 +488,7 @@ int network_load_one(Manager *manager, OrderedHashmap **networks, const char *fi
                               "QDisc\0"
                               "CAKE\0"
                               "ControlledDelay\0"
+                              "DeficitRoundRobinScheduler\0"
                               "PFIFO\0"
                               "FairQueueing\0"
                               "FairQueueingControlledDelay\0"

src/network/tc/drr.c

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: LGPL-2.1+
+ * Copyright © 2020 VMware, Inc. */
+
+#include "drr.h"
+
+const QDiscVTable drr_vtable = {
+        .object_size = sizeof(DeficitRoundRobinScheduler),
+        .tca_kind = "drr",
+};

src/network/tc/drr.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: LGPL-2.1+
+ * Copyright © 2020 VMware, Inc. */
+#pragma once
+
+#include "qdisc.h"
+
+typedef struct DeficitRoundRobinScheduler {
+        QDisc meta;
+} DeficitRoundRobinScheduler;
+
+DEFINE_QDISC_CAST(DRR, DeficitRoundRobinScheduler);
+extern const QDiscVTable drr_vtable;

src/network/tc/qdisc.c

@@ -18,6 +18,7 @@
 const QDiscVTable * const qdisc_vtable[_QDISC_KIND_MAX] = {
         [QDISC_KIND_CAKE] = &cake_vtable,
         [QDISC_KIND_CODEL] = &codel_vtable,
+        [QDISC_KIND_DRR] = &drr_vtable,
         [QDISC_KIND_FQ] = &fq_vtable,
         [QDISC_KIND_FQ_CODEL] = &fq_codel_vtable,
         [QDISC_KIND_GRED] = &gred_vtable,

src/network/tc/qdisc.h

@@ -11,6 +11,7 @@
 typedef enum QDiscKind {
         QDISC_KIND_CAKE,
         QDISC_KIND_CODEL,
+        QDISC_KIND_DRR,
         QDISC_KIND_FQ,
         QDISC_KIND_FQ_CODEL,
         QDISC_KIND_GRED,
@@ -88,6 +89,7 @@ CONFIG_PARSER_PROTOTYPE(config_parse_qdisc_handle);
 #include "htb.h"
 #include "pie.h"
 #include "netem.h"
+#include "drr.h"
 #include "sfb.h"
 #include "sfq.h"
 #include "tbf.h"

test/fuzz/fuzz-network-parser/directives.network

@@ -374,3 +374,6 @@ PacketLimit=
 Parent=
 Handle=
 PacketLimit=
+[DeficitRoundRobinScheduler]
+Parent=
+Handle=