[RFC PATCH net-next v3 07/21] ethtool: implement EVENT notifications

From: Michal Kubecek
Date: Mon Feb 18 2019 - 13:22:11 EST

Three types of netlink notifications are introduced:

- ETHA_EVENT_NEWDEV to notify about newly registered network devices
- ETHA_EVENT_DELDEV to notify about unregistered network devices
- ETHA_EVENT_RENAMEDEV to notify about renamed network device

The notifications are triggered by NETDEV_REGISTER, NETDEV_UNREGISTER and
NETDEV_CHANGENAME notifiers.

These notifications are intended for applications and daemons monitoring
ethtool events to allow updating the list of existing devices without
having to open another socket for rtnetlink.

Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
---
Documentation/networking/ethtool-netlink.txt | 27 ++++++++
include/uapi/linux/ethtool_netlink.h | 37 +++++++++++
net/ethtool/netlink.c | 65 ++++++++++++++++++++
3 files changed, 129 insertions(+)

diff --git a/Documentation/networking/ethtool-netlink.txt b/Documentation/networking/ethtool-netlink.txt
index 205ae4462e9e..b79c26b5e92b 100644
--- a/Documentation/networking/ethtool-netlink.txt
+++ b/Documentation/networking/ethtool-netlink.txt
@@ -125,6 +125,8 @@ which the request applies.
List of message types
---------------------

+ ETHNL_CMD_EVENT notification only
+
All constants use ETHNL_CMD_ prefix, usually followed by "GET", "SET" or "ACT"
to indicate the type.

@@ -136,9 +138,34 @@ messages marked as "response only" in the table above. "Get" messages with
NLM_F_DUMP flags and no device identification dump the information for all
devices supporting the request.

+Type ETHNL_CMD_EVENT is special, these messages are never used in userspace
+requests or kernel replies. They are only sent by kernel to sockets listening
+to "monitor" multicast group to inform userspace about certain events.
+
Later sections describe the format and semantics of these request messages.


+EVENT
+-----
+
+EVENT messages are only used in kernel multicast notifications. Atributes
+correspond to specific event types, the same type can appear multiple times.
+
+ ETHA_EVENT_NEWDEV (nested) new device was registered
+ ETHA_NEWDEV_DEV (nested) new device
+ ETHA_EVENT_DELDEV (nested) device was unregistered
+ ETHA_DELDEV_DEV (nested) removed device
+ ETHA_EVENT_RENAMEDEV (nested) device was renamed
+ ETHA_RENAMEDEV_DEV (nested) renamed device
+
+For ETHA_EVENT_RENAMEDEV, the name ETHA_RENAME_DEV/ETHA_DEV_NAME is the new
+name after the rename.
+
+Userspace application must expect multiple events to be present in one message
+and also multiple events of the same type (e.g. two or more newly registered
+devices).
+
+
Request translation
-------------------

diff --git a/include/uapi/linux/ethtool_netlink.h b/include/uapi/linux/ethtool_netlink.h
index b662d75a0636..7e192ad8ce3a 100644
--- a/include/uapi/linux/ethtool_netlink.h
+++ b/include/uapi/linux/ethtool_netlink.h
@@ -7,6 +7,7 @@

enum {
ETHNL_CMD_NOOP,
+ ETHNL_CMD_EVENT, /* only for notifications */

__ETHNL_CMD_CNT,
ETHNL_CMD_MAX = (__ETHNL_CMD_CNT - 1)
@@ -55,6 +56,42 @@ enum {
ETHA_BITSET_MAX = (__ETHA_BITSET_CNT - 1)
};

+/* events */
+
+enum {
+ ETHA_NEWDEV_UNSPEC,
+ ETHA_NEWDEV_DEV, /* nest - ETHA_DEV_* */
+
+ __ETHA_NEWDEV_CNT,
+ ETHA_NEWDEV_MAX = (__ETHA_NEWDEV_CNT - 1)
+};
+
+enum {
+ ETHA_DELDEV_UNSPEC,
+ ETHA_DELDEV_DEV, /* nest - ETHA_DEV_* */
+
+ __ETHA_DELDEV_CNT,
+ ETHA_DELDEV_MAX = (__ETHA_DELDEV_CNT - 1)
+};
+
+enum {
+ ETHA_RENAMEDEV_UNSPEC,
+ ETHA_RENAMEDEV_DEV, /* nest - ETHA_DEV_* */
+
+ __ETHA_RENAMEDEV_CNT,
+ ETHA_RENAMEDEV_MAX = (__ETHA_RENAMEDEV_CNT - 1)
+};
+
+enum {
+ ETHA_EVENT_UNSPEC,
+ ETHA_EVENT_NEWDEV, /* nest - ETHA_NEWDEV_* */
+ ETHA_EVENT_DELDEV, /* nest - ETHA_DELDEV_* */
+ ETHA_EVENT_RENAMEDEV, /* nest - ETHA_RENAMEDEV_* */
+
+ __ETHA_EVENT_CNT,
+ ETHA_EVENT_MAX = (__ETHA_EVENT_CNT - 1)
+};
+
/* generic netlink info */
#define ETHTOOL_GENL_NAME "ethtool"
#define ETHTOOL_GENL_VERSION 1
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index a5fa54c2b743..ee3424cd1f90 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -148,6 +148,67 @@ void ethtool_notify(struct net_device *dev, struct netlink_ext_ack *extack,
}
EXPORT_SYMBOL(ethtool_notify);

+/* size of NEWDEV/DELDEV notification */
+static inline unsigned int dev_notify_size(void)
+{
+ return nla_total_size(dev_ident_size());
+}
+
+static void ethnl_notify_devlist(struct netdev_notifier_info *info,
+ u16 ev_type, u16 dev_attr)
+{
+ struct net_device *dev = netdev_notifier_info_to_dev(info);
+ struct sk_buff *skb;
+ struct nlattr *nest;
+ void *ehdr;
+ int ret;
+
+ skb = genlmsg_new(dev_notify_size(), GFP_KERNEL);
+ if (!skb)
+ return;
+ ehdr = genlmsg_put(skb, 0, ++ethnl_bcast_seq, &ethtool_genl_family, 0,
+ ETHNL_CMD_EVENT);
+ if (!ehdr)
+ goto out_skb;
+ nest = ethnl_nest_start(skb, ev_type);
+ if (!nest)
+ goto out_skb;
+ ret = ethnl_fill_dev(skb, dev, dev_attr);
+ if (ret < 0)
+ goto out_skb;
+ nla_nest_end(skb, nest);
+ genlmsg_end(skb, ehdr);
+
+ genlmsg_multicast(&ethtool_genl_family, skb, 0, ETHNL_MCGRP_MONITOR,
+ GFP_KERNEL);
+ return;
+out_skb:
+ nlmsg_free(skb);
+}
+
+static int ethnl_netdev_event(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ switch (event) {
+ case NETDEV_REGISTER:
+ ethnl_notify_devlist(ptr, ETHA_EVENT_NEWDEV, ETHA_NEWDEV_DEV);
+ break;
+ case NETDEV_UNREGISTER:
+ ethnl_notify_devlist(ptr, ETHA_EVENT_DELDEV, ETHA_DELDEV_DEV);
+ break;
+ case NETDEV_CHANGENAME:
+ ethnl_notify_devlist(ptr, ETHA_EVENT_RENAMEDEV,
+ ETHA_RENAMEDEV_DEV);
+ break;
+ }
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block ethnl_netdev_notifier = {
+ .notifier_call = ethnl_netdev_event,
+};
+
/* genetlink setup */

static const struct genl_ops ethtool_genl_ops[] = {
@@ -179,6 +240,10 @@ static int __init ethnl_init(void)
if (ret < 0)
panic("ethtool: could not register genetlink family\n");

+ ret = register_netdevice_notifier(&ethnl_netdev_notifier);
+ if (ret < 0)
+ panic("ethtool: could not register netdev notifier\n");
+
return 0;
}

--
2.20.1