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

From: Jiri Pirko <jiri@resnulli.us>
To: Michal Kubecek <mkubecek@suse.cz>
Cc: netdev@vger.kernel.org, David Miller <davem@davemloft.net>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Florian Fainelli <f.fainelli@gmail.com>,
	John Linville <linville@tuxdriver.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Johannes Berg <johannes@sipsolutions.net>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next v6 07/15] ethtool: support for netlink notifications
Date: Thu, 4 Jul 2019 10:06:00 +0200	[thread overview]
Message-ID: <20190704080600.GG2250@nanopsycho> (raw)
In-Reply-To: <20190703141614.GL20101@unicorn.suse.cz>

Wed, Jul 03, 2019 at 04:16:14PM CEST, mkubecek@suse.cz wrote:
>On Wed, Jul 03, 2019 at 03:33:52PM +0200, Jiri Pirko wrote:
>> >+/* 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" ?
>
>It's infomask to interpret the same way as if it came from request
>header (the notification triggered by a SET request or its ioctl
>equivalent uses the same format as corresponding GET_REPLY message and
>is created by the same code). But it could be called infomask, I have no
>strong opinion about that.

The name should be same all along the code so the reader can track it.

>
>> >+{
>> >+	if (unlikely(!ethnl_ok))
>> >+		return;
>> >+	ASSERT_RTNL();
>> >+
>> >+	if (likely(cmd < ARRAY_SIZE(ethnl_notify_handlers) &&
>> >+		   ethnl_notify_handlers[cmd]))
>> 
>> How it could be null?
>
>Notification message types share the enum with other kernel messages:
>
>/* message types - kernel to userspace */
>enum {
>	ETHTOOL_MSG_KERNEL_NONE,
>	ETHTOOL_MSG_STRSET_GET_REPLY,
>	ETHTOOL_MSG_SETTINGS_GET_REPLY,
>	ETHTOOL_MSG_SETTINGS_NTF,
>	ETHTOOL_MSG_SETTINGS_SET_REPLY,
>	ETHTOOL_MSG_INFO_GET_REPLY,
>	ETHTOOL_MSG_PARAMS_GET_REPLY,
>	ETHTOOL_MSG_PARAMS_NTF,
>	ETHTOOL_MSG_NWAYRST_NTF,
>	ETHTOOL_MSG_PHYSID_NTF,
>	ETHTOOL_MSG_RESET_NTF,
>	ETHTOOL_MSG_RESET_ACT_REPLY,
>	ETHTOOL_MSG_RXFLOW_GET_REPLY,
>	ETHTOOL_MSG_RXFLOW_NTF,
>	ETHTOOL_MSG_RXFLOW_SET_REPLY,
>
>	/* add new constants above here */
>	__ETHTOOL_MSG_KERNEL_CNT,
>	ETHTOOL_MSG_KERNEL_MAX = (__ETHTOOL_MSG_KERNEL_CNT - 1)
>};
>
>Only entries for *_NTF types are non-null in ethnl_notify_handlers[]:
>
>static const ethnl_notify_handler_t ethnl_notify_handlers[] = {
>	[ETHTOOL_MSG_SETTINGS_NTF]	= ethnl_std_notify,
>	[ETHTOOL_MSG_PARAMS_NTF]	= ethnl_std_notify,
>	[ETHTOOL_MSG_NWAYRST_NTF]	= ethnl_nwayrst_notify,
>	[ETHTOOL_MSG_PHYSID_NTF]	= ethnl_physid_notify,
>	[ETHTOOL_MSG_RESET_NTF]		= ethnl_reset_notify,
>	[ETHTOOL_MSG_RXFLOW_NTF]	= ethnl_rxflow_notify,
>};
>
>If the check above fails, it means that kernel code tried to send
>a notification with type which does not exist or is not a notification,
>i.e. a bug in kernel; that's why the WARN_ONCE.

Got it, thanks!

>
>Michal
>
>> >+		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);