Subject: Re: [PATCH net-next v7 14/17] ethtool: set link settings with LINKINFO_SET request

From: Jiri Pirko <[email-masked]>
Date: Fri, 11 Oct 2019 07:59:51 +0200

Thu, Oct 10, 2019 at 09:30:44PM CEST, [email-masked] wrote:
>On Thu, Oct 10, 2019 at 05:37:54PM +0200, Jiri Pirko wrote:
>> Wed, Oct 09, 2019 at 10:59:43PM CEST, [email-masked] wrote:
>> >Implement LINKINFO_SET netlink request to set link settings queried by
>> >LINKINFO_GET message.
>> >
>> >Only physical port, phy MDIO address and MDI(-X) control can be set,
>> >attempt to modify MDI(-X) status and transceiver is rejected.
>> >
>> >When any data is modified, ETHTOOL_MSG_LINKINFO_NTF message in the same
>> >format as reply to LINKINFO_GET request is sent to notify userspace about
>> >the changes. The same notification is also sent when these settings are
>> >modified using the ioctl interface.
>> >
>> 
>> It is a bit confusing and harder to follow when you have set and notify
>> code in the same patch. Could you please split?
>
>As the notification is composed and sent by ethnl_std_notify() with help
>of the callback functions used to generate the reply to GET request, the
>only notification related changes in this patch are the three calls to
>ethtool_notify() (one in netlink code, two in ioctl code) and the entry
>added to ethnl_notify_handlers[].
>
>But I have no objection to splitting these out into a separate patch,
>except for having sacrifice some of the patches actually implementing
>something so that the series doesn't get too long.

Please split.

>
>> 
>> [...]
>> 
>> 
>> >+/* LINKINFO_SET */
>> >+
>> >+static const struct nla_policy linkinfo_hdr_policy[ETHTOOL_A_HEADER_MAX + 1] = {
>> >+	[ETHTOOL_A_HEADER_UNSPEC]		= { .type = NLA_REJECT },
>> >+	[ETHTOOL_A_HEADER_DEV_INDEX]		= { .type = NLA_U32 },
>> >+	[ETHTOOL_A_HEADER_DEV_NAME]		= { .type = NLA_NUL_STRING,
>> >+						    .len = IFNAMSIZ - 1 },
>> >+	[ETHTOOL_A_HEADER_GFLAGS]		= { .type = NLA_U32 },
>> >+	[ETHTOOL_A_HEADER_RFLAGS]		= { .type = NLA_REJECT },
>> >+};
>> 
>> This is what I was talking about in the other email. These common attrs
>> should have common policy and should be parsed by generic netlink code
>> by default and be available for ethnl_set_linkinfo() in info->attrs.
>
>NLA_REJECT for ETHTOOL_A_HEADER_RFLAGS is probably an overkill here. If
>I just check that client does not set flags we do not know, I can have
>one universal header policy as well. I'll probably do that.
>
>> >+int ethnl_set_linkinfo(struct sk_buff *skb, struct genl_info *info)
>> >+{
>> >+	struct nlattr *tb[ETHTOOL_A_LINKINFO_MAX + 1];
>> >+	struct ethtool_link_ksettings ksettings = {};
>> >+	struct ethtool_link_settings *lsettings;
>> >+	struct ethnl_req_info req_info = {};
>> >+	struct net_device *dev;
>> >+	bool mod = false;
>> >+	int ret;
>> >+
>> >+	ret = nlmsg_parse(info->nlhdr, GENL_HDRLEN, tb,
>> >+			  ETHTOOL_A_LINKINFO_MAX, linkinfo_set_policy,
>> >+			  info->extack);
>> 
>> Yeah, genl code should do this parse..
>
>Not really. It would only parse the top level - which, in your design,
>would only be the common header. In other words, it would do what is now
>done by the call to nla_parse_nested() inside ethnl_parse_header(). For
>equivalent of this parse, you would still have to call your own
>nla_parse_nested() on the "request specific data" nested attribute.

Okay, the parse would stay, you are correct.

>
>> >+	if (ret < 0)
>> >+		return ret;
>> >+	ret = ethnl_parse_header(&req_info, tb[ETHTOOL_A_LINKINFO_HEADER],
>> >+				 genl_info_net(info), info->extack,
>> >+				 linkinfo_hdr_policy, true);
>> 
>> and pre_doit should do this one.
>
>...and also (each) start(). Which means you would either duplicate the
>code or introduce the same helper. All you would save would be that one
>call of nla_parse_nested() in ethnl_parse_header().

Sure, it could be a same helper called fro pre_doit and start. No
problem.

>
>> >+
>> >+	ret = 0;
>> >+	if (mod) {
>> 
>> 	if (!mod)
>> 		goto out_ops;
>> 
>> ?
>
>OK
>
>> >+		ret = dev->ethtool_ops->set_link_ksettings(dev, &ksettings);
>> >+		if (ret < 0)
>> >+			GENL_SET_ERR_MSG(info, "link settings update failed");
>> >+		else
>> >+			ethtool_notify(dev, ETHTOOL_MSG_LINKINFO_NTF, NULL);
>> >+	}
>> >+
>> >+out_ops:
>> >+	ethnl_after_ops(dev);
>> >+out_rtnl:
>> >+	rtnl_unlock();
>> >+	dev_put(dev);
>> >+	return ret;
>> >+}
>...
>> >@@ -683,6 +688,7 @@ typedef void (*ethnl_notify_handler_t)(struct net_device *dev, unsigned int cmd,
>> > 				       const void *data);
>> > 
>> > static const ethnl_notify_handler_t ethnl_notify_handlers[] = {
>> >+	[ETHTOOL_MSG_LINKINFO_NTF]	= ethnl_std_notify,
>> 
>> Correct me if I'm wrong, but this is the only notification I found in
>> this patchset. Do you expect other then ethnl_std_notify() handler?
>> Bacause otherwise this can ba simplified down to just a single table
>> similar you have for GET.
>
>Yes, there will be other handlers; ethnl_std_notify() can only handle
>the simplest (even if most common) type of notification where caller
>does not pass any information except the device, the notification
>message is exactly the same as reply to corresponding GET request would
>be and that GET request does not have any attributes (so that it can be
>handled with ethnl_get_doit()).
>
>There will be notifications which will need their own handlers, e.g. all
>notifications triggered by an action request (e.g. renegotiation or
>device reset) or notifications triggered by "ethtool -X".
>
>Michal