[RFC PATCH net-next v3 06/21] ethtool: support for netlink notifications

[Michal Kubecek]

Add infrastructure for ethtool netlink notifications. There is only one
multicast group "monitor" which is used to notify userspace about changes.
Notifications are supposed to be broadcasted on every configuration change,
whether it is done using the netlink interface or legacy ioctl one.

To trigger an ethtool notification, both ethtool netlink and external code
use ethtool_notify() helper. This helper requires RTNL to be held and may
sleep.

Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
---
 include/linux/ethtool_netlink.h      |  5 +++++
 include/linux/netdevice.h            | 12 +++++++++++
 include/uapi/linux/ethtool_netlink.h |  2 ++
 net/ethtool/netlink.c                | 32 ++++++++++++++++++++++++++++
 net/ethtool/netlink.h                |  2 ++
 5 files changed, 53 insertions(+)

diff --git a/include/linux/ethtool_netlink.h b/include/linux/ethtool_netlink.h
index 0412adb4f42f..2a15e64a16f3 100644
--- a/include/linux/ethtool_netlink.h
+++ b/include/linux/ethtool_netlink.h
@@ -5,5 +5,10 @@
 
 #include <uapi/linux/ethtool_netlink.h>
 #include <linux/ethtool.h>
+#include <linux/netdevice.h>
+
+enum ethtool_multicast_groups {
+	ETHNL_MCGRP_MONITOR,
+};
 
 #endif /* _LINUX_ETHTOOL_NETLINK_H_ */
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index aab4d9f6613d..9a50a67f328f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4340,6 +4340,18 @@ struct netdev_notifier_bonding_info {
 void netdev_bonding_info_change(struct net_device *dev,
 				struct netdev_bonding_info *bonding_info);
 
+#if IS_ENABLED(CONFIG_ETHTOOL_NETLINK)
+void ethtool_notify(struct net_device *dev, struct netlink_ext_ack *extack,
+		    unsigned int cmd, u32 req_mask, const void *data);
+#else
+static inline void ethtool_notify(struct net_device *dev,
+				  struct netlink_ext_ack *extack,
+				  unsigned int cmd, u32 req_mask,
+				  const void *data)
+{
+}
+#endif
+
 static inline
 struct sk_buff *skb_gso_segment(struct sk_buff *skb, netdev_features_t features)
 {
diff --git a/include/uapi/linux/ethtool_netlink.h b/include/uapi/linux/ethtool_netlink.h
index 7f3d401977b4..b662d75a0636 100644
--- a/include/uapi/linux/ethtool_netlink.h
+++ b/include/uapi/linux/ethtool_netlink.h
@@ -59,4 +59,6 @@ enum {
 #define ETHTOOL_GENL_NAME "ethtool"
 #define ETHTOOL_GENL_VERSION 1
 
+#define ETHTOOL_MCGRP_MONITOR_NAME "monitor"
+
 #endif /* _UAPI_LINUX_ETHTOOL_NETLINK_H_ */
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index ffdcc7c9d4bc..a5fa54c2b743 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -4,6 +4,8 @@
 #include <linux/ethtool_netlink.h>
 #include "netlink.h"
 
+u32 ethnl_bcast_seq;
+
 static const struct nla_policy dev_policy[ETHA_DEV_MAX + 1] = {
 	[ETHA_DEV_UNSPEC]	= { .type = NLA_REJECT },
 	[ETHA_DEV_INDEX]	= { .type = NLA_U32 },
@@ -122,11 +124,39 @@ struct sk_buff *ethnl_reply_init(size_t payload, struct net_device *dev, u8 cmd,
 	return NULL;
 }
 
+/* notifications */
+
+typedef void (*ethnl_notify_handler_t)(struct net_device *dev,
+				       struct netlink_ext_ack *extack,
+				       unsigned int cmd, u32 req_mask,
+				       const void *data);
+
+ethnl_notify_handler_t ethnl_notify_handlers[] = {
+};
+
+void ethtool_notify(struct net_device *dev, struct netlink_ext_ack *extack,
+		    unsigned int cmd, u32 req_mask, const void *data)
+{
+	ASSERT_RTNL();
+
+	if (likely(cmd < ARRAY_SIZE(ethnl_notify_handlers) &&
+		   ethnl_notify_handlers[cmd]))
+		ethnl_notify_handlers[cmd](dev, extack, cmd, req_mask, data);
+	else
+		WARN_ONCE(1, "notification %u not implemented (dev=%s, req_mask=0x%x)\n",
+			  cmd, netdev_name(dev), req_mask);
+}
+EXPORT_SYMBOL(ethtool_notify);
+
 /* genetlink setup */
 
 static const struct genl_ops ethtool_genl_ops[] = {
 };
 
+static const struct genl_multicast_group ethtool_nl_mcgrps[] = {
+	[ETHNL_MCGRP_MONITOR] = { .name = ETHTOOL_MCGRP_MONITOR_NAME },
+};
+
 struct genl_family ethtool_genl_family = {
 	.hdrsize	= 0,
 	.name		= ETHTOOL_GENL_NAME,
@@ -135,6 +165,8 @@ struct genl_family ethtool_genl_family = {
 	.parallel_ops	= true,
 	.ops		= ethtool_genl_ops,
 	.n_ops		= ARRAY_SIZE(ethtool_genl_ops),
+	.mcgrps		= ethtool_nl_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(ethtool_nl_mcgrps),
 };
 
 /* module setup */
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index ba638eb5a99a..78385baeaec0 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -11,6 +11,8 @@
 #define ETHNL_SET_ERRMSG(info, msg) \
 	do { if (info) GENL_SET_ERR_MSG(info, msg); } while (0)
 
+extern u32 ethnl_bcast_seq;
+
 extern struct genl_family ethtool_genl_family;
 
 struct net_device *ethnl_dev_get(struct genl_info *info, struct nlattr *nest);
-- 
2.20.1