Re: [PATCH net-next v6 07/15] ethtool: support for netlink notifications

[Jiri Pirko <jiri@resnulli.us>]

Tue, Jul 02, 2019 at 01:50:14PM CEST, mkubecek@suse.cz wrote:
>Add infrastructure for ethtool netlink notifications. There is only one
>multicast group "monitor" which is used to notify userspace about changes
>and actions performed. Notification messages (types using suffix _NTF)
>share the format with replies to GET requests.
>
>Notifications are supposed to be broadcasted on every configuration change,
>whether it is done using the netlink interface or ioctl one. Netlink SET
>requests only trigger a notification if some data is actually changed.
>
>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. Handlers sending messages for specific notification message types
>are registered in ethnl_notify_handlers array. As notifications can be
>triggered from other code, ethnl_ok flag is used to prevent an attempt to
>send notification before genetlink family is registered.
>
>Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
>---
> include/linux/ethtool_netlink.h      |  5 ++++
> include/linux/netdevice.h            | 12 ++++++++++
> include/uapi/linux/ethtool_netlink.h |  2 ++
> net/ethtool/netlink.c                | 35 ++++++++++++++++++++++++++++
> 4 files changed, 54 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 88292953aa6f..c57d9917fd50 100644
>--- a/include/linux/netdevice.h
>+++ b/include/linux/netdevice.h
>@@ -4350,6 +4350,18 @@ 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 805f314f4454..8938a1f09057 100644
>--- a/include/uapi/linux/ethtool_netlink.h
>+++ b/include/uapi/linux/ethtool_netlink.h
>@@ -91,4 +91,6 @@ 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 e13f29bbd625..a7a0bfe1818c 100644
>--- a/net/ethtool/netlink.c
>+++ b/net/ethtool/netlink.c
>@@ -6,6 +6,8 @@
> 
> static struct genl_family ethtool_genl_family;
> 
>+static bool ethnl_ok __read_mostly;
>+
> static const struct nla_policy dflt_header_policy[ETHTOOL_A_HEADER_MAX + 1] = {
> 	[ETHTOOL_A_HEADER_UNSPEC]	= { .type = NLA_REJECT },
> 	[ETHTOOL_A_HEADER_DEV_INDEX]	= { .type = NLA_U32 },
>@@ -176,11 +178,41 @@ 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);
>+
>+static const 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)

What's "req_mask" ?


>+{
>+	if (unlikely(!ethnl_ok))
>+		return;
>+	ASSERT_RTNL();
>+
>+	if (likely(cmd < ARRAY_SIZE(ethnl_notify_handlers) &&
>+		   ethnl_notify_handlers[cmd]))

How it could be null?


>+		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 },
>+};
>+
> static struct genl_family ethtool_genl_family = {
> 	.name		= ETHTOOL_GENL_NAME,
> 	.version	= ETHTOOL_GENL_VERSION,
>@@ -188,6 +220,8 @@ static 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 */
>@@ -199,6 +233,7 @@ static int __init ethnl_init(void)
> 	ret = genl_register_family(&ethtool_genl_family);
> 	if (WARN(ret < 0, "ethtool: genetlink family registration failed"))
> 		return ret;
>+	ethnl_ok = true;
> 
> 	return 0;
> }
>-- 
>2.22.0
>