netdev-genl: create a simple family for netdev stuff

Add a Netlink spec-compatible family for netdevs.
This is a very simple implementation without much
thought going into it.

It allows us to reap all the benefits of Netlink specs,
one can use the generic client to issue the commands:

  $ ./gen.py --spec netdev.yaml --do dev_get --json='{"ifindex": 2}'
  {'ifindex': 2, 'xdp-features': 31}

  $ ./gen.py --spec netdev.yaml --dump dev_get
  [{'ifindex': 1, 'xdp-features': 0}, {'ifindex': 2, 'xdp-features': 31}]

the generic python library does not have flags-by-name
support, yet, but we also don't have to carry strings
in the messages, as user space can get the names from
the spec.

Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Co-developed-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Co-developed-by: Marek Majtyka <alardam@gmail.com>
Signed-off-by: Marek Majtyka <alardam@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/netdev.yaml

@@ -0,0 +1,72 @@
+name: netdev
+
+doc:
+  netdev configuration over generic netlink.
+
+definitions:
+  -
+    type: enum
+    name: xdp-feat
+    entries: [ aborted, drop, pass, redirect,
+               ndo-xmit, xsk-zerocopy,
+               hw-offload, rx-sg, ndo-xmit-sg
+    ]
+
+attribute-sets:
+  -
+    name: dev
+    attributes:
+      -
+        name: ifindex
+        doc: netdev ifindex
+        type: u32
+        value: 1
+        checks:
+          min: 1
+      -
+        name: pad
+        type: pad
+      -
+        name: xdp-features
+        doc: Bitmask of enabled xdp-features.
+        type: u64
+        enum: xdp-feat
+        enum-as-flags: true
+
+operations:
+  list:
+    -
+      name: dev-get
+      doc: Get / dump information about a netdev.
+      value: 1
+      attribute-set: dev
+      do:
+        request:
+          attributes:
+            - ifindex
+        reply: &dev-all
+          attributes:
+            - ifindex
+            - xdp-features
+      dump:
+        reply: *dev-all
+    -
+      name: dev-add-ntf
+      doc: Notification about device appearing.
+      notify: dev-get
+      mcgrp: mgmt
+    -
+      name: dev-del-ntf
+      doc: Notification about device disappearing.
+      notify: dev-get
+      mcgrp: mgmt
+    -
+      name: dev-change-ntf
+      doc: Notification about device configuration being changed.
+      notify: dev-get
+      mcgrp: mgmt
+
+mcast-groups:
+  list:
+    -
+      name: mgmt

include/linux/netdevice.h

@@ -47,6 +47,7 @@
 #include <uapi/linux/netdevice.h>
 #include <uapi/linux/if_bonding.h>
 #include <uapi/linux/pkt_cls.h>
+#include <uapi/linux/netdev.h>
 #include <linux/hashtable.h>
 #include <linux/rbtree.h>
 #include <net/net_trackers.h>
@@ -2048,6 +2049,7 @@ struct net_device {
 
 	/* Read-mostly cache-line for fast-path access */
 	unsigned int		flags;
+	xdp_features_t		xdp_features;
 	unsigned long long	priv_flags;
 	const struct net_device_ops *netdev_ops;
 	int			ifindex;

include/net/xdp.h

@@ -7,6 +7,7 @@
 #define __LINUX_NET_XDP_H__
 
 #include <linux/skbuff.h> /* skb_shared_info */
+#include <uapi/linux/netdev.h>
 
 /**
  * DOC: XDP RX-queue information
@@ -43,6 +44,8 @@ enum xdp_mem_type {
 	MEM_TYPE_MAX,
 };
 
+typedef u32 xdp_features_t;
+
 /* XDP flags for ndo_xdp_xmit */
 #define XDP_XMIT_FLUSH		(1U << 0)	/* doorbell signal consumer */
 #define XDP_XMIT_FLAGS_MASK	XDP_XMIT_FLUSH

include/uapi/linux/netdev.h

@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/netdev.yaml */
+/* YNL-GEN uapi header */
+
+#ifndef _UAPI_LINUX_NETDEV_H
+#define _UAPI_LINUX_NETDEV_H
+
+#define NETDEV_FAMILY_NAME	"netdev"
+#define NETDEV_FAMILY_VERSION	1
+
+enum netdev_xdp_act {
+	NETDEV_XDP_ACT_ABORTED_BIT,
+	NETDEV_XDP_ACT_DROP_BIT,
+	NETDEV_XDP_ACT_PASS_BIT,
+	NETDEV_XDP_ACT_TX_BIT,
+	NETDEV_XDP_ACT_REDIRECT_BIT,
+	NETDEV_XDP_ACT_NDO_XMIT_BIT,
+	NETDEV_XDP_ACT_XSK_ZEROCOPY_BIT,
+	NETDEV_XDP_ACT_HW_OFFLOAD_BIT,
+	NETDEV_XDP_ACT_RX_SG_BIT,
+	NETDEV_XDP_ACT_NDO_XMIT_SG_BIT
+};
+
+#define NETDEV_XDP_ACT_ABORTED		BIT(NETDEV_XDP_ACT_ABORTED_BIT)
+#define NETDEV_XDP_ACT_DROP		BIT(NETDEV_XDP_ACT_DROP_BIT)
+#define NETDEV_XDP_ACT_PASS		BIT(NETDEV_XDP_ACT_PASS_BIT)
+#define NETDEV_XDP_ACT_TX		BIT(NETDEV_XDP_ACT_TX_BIT)
+#define NETDEV_XDP_ACT_REDIRECT		BIT(NETDEV_XDP_ACT_REDIRECT_BIT)
+#define NETDEV_XDP_ACT_NDO_XMIT		BIT(NETDEV_XDP_ACT_NDO_XMIT_BIT)
+#define NETDEV_XDP_ACT_XSK_ZEROCOPY	BIT(NETDEV_XDP_ACT_XSK_ZEROCOPY_BIT)
+#define NETDEV_XDP_ACT_HW_OFFLOAD	BIT(NETDEV_XDP_ACT_HW_OFFLOAD_BIT)
+#define NETDEV_XDP_ACT_RX_SG		BIT(NETDEV_XDP_ACT_RX_SG_BIT)
+#define NETDEV_XDP_ACT_NDO_XMIT_SG	BIT(NETDEV_XDP_ACT_NDO_XMIT_SG_BIT)
+
+#define NETDEV_XDP_ACT_BASIC		(NETDEV_XDP_ACT_DROP |	\
+					 NETDEV_XDP_ACT_PASS |	\
+					 NETDEV_XDP_ACT_TX |	\
+					 NETDEV_XDP_ACT_ABORTED)
+#define NETDEV_XDP_ACT_FULL		(NETDEV_XDP_ACT_BASIC |	\
+					 NETDEV_XDP_ACT_REDIRECT)
+#define NETDEV_XDP_ACT_ZC		(NETDEV_XDP_ACT_FULL |	\
+					 NETDEV_XDP_ACT_XSK_ZEROCOPY)
+
+enum {
+	NETDEV_A_DEV_IFINDEX = 1,
+	NETDEV_A_DEV_PAD,
+	NETDEV_A_DEV_XDP_FEATURES,
+
+	__NETDEV_A_DEV_MAX,
+	NETDEV_A_DEV_MAX = (__NETDEV_A_DEV_MAX - 1)
+};
+
+enum {
+	NETDEV_CMD_DEV_GET = 1,
+	NETDEV_CMD_DEV_ADD_NTF,
+	NETDEV_CMD_DEV_DEL_NTF,
+	NETDEV_CMD_DEV_CHANGE_NTF,
+
+	__NETDEV_CMD_MAX,
+	NETDEV_CMD_MAX = (__NETDEV_CMD_MAX - 1)
+};
+
+#define NETDEV_MCGRP_MGMT	"mgmt"
+
+#endif /* _UAPI_LINUX_NETDEV_H */

net/core/Makefile

@@ -12,7 +12,8 @@ obj-$(CONFIG_SYSCTL) += sysctl_net_core.o
 obj-y		     += dev.o dev_addr_lists.o dst.o netevent.o \
 			neighbour.o rtnetlink.o utils.o link_watch.o filter.o \
 			sock_diag.o dev_ioctl.o tso.o sock_reuseport.o \
-			fib_notifier.o xdp.o flow_offload.o gro.o
+			fib_notifier.o xdp.o flow_offload.o gro.o \
+			netdev-genl.o netdev-genl-gen.o
 
 obj-$(CONFIG_NETDEV_ADDR_LIST_TEST) += dev_addr_lists_test.o
 

net/core/netdev-genl-gen.c

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: BSD-3-Clause
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/netdev.yaml */
+/* YNL-GEN kernel source */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "netdev-genl-gen.h"
+
+#include <linux/netdev.h>
+
+// NETDEV_CMD_DEV_GET - do
+static const struct nla_policy netdev_dev_get_nl_policy[NETDEV_A_DEV_IFINDEX + 1] = {
+	[NETDEV_A_DEV_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
+};
+
+// Ops table for netdev
+static const struct genl_split_ops netdev_nl_ops[2] = {
+	{
+		.cmd		= NETDEV_CMD_DEV_GET,
+		.doit		= netdev_nl_dev_get_doit,
+		.policy		= netdev_dev_get_nl_policy,
+		.maxattr	= NETDEV_A_DEV_IFINDEX,
+		.flags		= GENL_CMD_CAP_DO,
+	},
+	{
+		.cmd	= NETDEV_CMD_DEV_GET,
+		.dumpit	= netdev_nl_dev_get_dumpit,
+		.flags	= GENL_CMD_CAP_DUMP,
+	},
+};
+
+static const struct genl_multicast_group netdev_nl_mcgrps[] = {
+	[NETDEV_NLGRP_MGMT] = { "mgmt", },
+};
+
+struct genl_family netdev_nl_family __ro_after_init = {
+	.name		= NETDEV_FAMILY_NAME,
+	.version	= NETDEV_FAMILY_VERSION,
+	.netnsok	= true,
+	.parallel_ops	= true,
+	.module		= THIS_MODULE,
+	.split_ops	= netdev_nl_ops,
+	.n_split_ops	= ARRAY_SIZE(netdev_nl_ops),
+	.mcgrps		= netdev_nl_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(netdev_nl_mcgrps),
+};

net/core/netdev-genl-gen.h

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: BSD-3-Clause
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/netdev.yaml */
+/* YNL-GEN kernel header */
+
+#ifndef _LINUX_NETDEV_GEN_H
+#define _LINUX_NETDEV_GEN_H
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include <linux/netdev.h>
+
+int netdev_nl_dev_get_doit(struct sk_buff *skb, struct genl_info *info);
+int netdev_nl_dev_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
+
+enum {
+	NETDEV_NLGRP_MGMT,
+};
+
+extern struct genl_family netdev_nl_family;
+
+#endif /* _LINUX_NETDEV_GEN_H */