ethtool: set device ring sizes with RINGS_SET request

Implement RINGS_SET netlink request to set ring sizes of a network device.
These are traditionally set with ETHTOOL_SRINGPARAM ioctl request.

Like the ioctl implementation, the generic ethtool code checks if supplied
values do not exceed driver defined limits; if they do, first offending
attribute is reported using extack.

v2:
  - fix netdev reference leak in error path (found by Jakub Kicinsky)
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ethtool-netlink.rst

@@ -194,6 +194,7 @@ Userspace to kernel:
   ``ETHTOOL_MSG_PRIVFLAGS_GET``         get private flags
   ``ETHTOOL_MSG_PRIVFLAGS_SET``         set private flags
   ``ETHTOOL_MSG_RINGS_GET``             get ring sizes
+  ``ETHTOOL_MSG_RINGS_SET``             set ring sizes
   ===================================== ================================
 
 Kernel to userspace:
@@ -673,6 +674,26 @@ Kernel response contents:
   ====================================  ======  ==========================
 
 
+RINGS_SET
+=========
+
+Sets ring sizes like ``ETHTOOL_SRINGPARAM`` ioctl request.
+
+Request contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_RINGS_HEADER``            nested  reply header
+  ``ETHTOOL_A_RINGS_RX``                u32     size of RX ring
+  ``ETHTOOL_A_RINGS_RX_MINI``           u32     size of RX mini ring
+  ``ETHTOOL_A_RINGS_RX_JUMBO``          u32     size of RX jumbo ring
+  ``ETHTOOL_A_RINGS_TX``                u32     size of TX ring
+  ====================================  ======  ==========================
+
+Kernel checks that requested ring sizes do not exceed limits reported by
+driver. Driver may impose additional constraints and may not suspport all
+attributes.
+
+
 Request translation
 ===================
 
@@ -700,7 +721,7 @@ have their netlink replacement yet.
   ``ETHTOOL_GCOALESCE``               n/a
   ``ETHTOOL_SCOALESCE``               n/a
   ``ETHTOOL_GRINGPARAM``              ``ETHTOOL_MSG_RINGS_GET``
-  ``ETHTOOL_SRINGPARAM``              n/a
+  ``ETHTOOL_SRINGPARAM``              ``ETHTOOL_MSG_RINGS_SET``
   ``ETHTOOL_GPAUSEPARAM``             n/a
   ``ETHTOOL_SPAUSEPARAM``             n/a
   ``ETHTOOL_GRXCSUM``                 ``ETHTOOL_MSG_FEATURES_GET``

include/uapi/linux/ethtool_netlink.h

@@ -29,6 +29,7 @@ enum {
 	ETHTOOL_MSG_PRIVFLAGS_GET,
 	ETHTOOL_MSG_PRIVFLAGS_SET,
 	ETHTOOL_MSG_RINGS_GET,
+	ETHTOOL_MSG_RINGS_SET,
 
 	/* add new constants above here */
 	__ETHTOOL_MSG_USER_CNT,

net/ethtool/netlink.c

@@ -756,6 +756,11 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.dumpit	= ethnl_default_dumpit,
 		.done	= ethnl_default_done,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_RINGS_SET,
+		.flags	= GENL_UNS_ADMIN_PERM,
+		.doit	= ethnl_set_rings,
+	},
 };
 
 static const struct genl_multicast_group ethtool_nl_mcgrps[] = {

net/ethtool/netlink.h

@@ -347,5 +347,6 @@ int ethnl_set_debug(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_wol(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_features(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_privflags(struct sk_buff *skb, struct genl_info *info);
+int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info);
 
 #endif /* _NET_ETHTOOL_NETLINK_H */

net/ethtool/rings.c

@@ -106,3 +106,92 @@ const struct ethnl_request_ops ethnl_rings_request_ops = {
 	.reply_size		= rings_reply_size,
 	.fill_reply		= rings_fill_reply,
 };
+
+/* RINGS_SET */
+
+static const struct nla_policy
+rings_set_policy[ETHTOOL_A_RINGS_MAX + 1] = {
+	[ETHTOOL_A_RINGS_UNSPEC]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_RINGS_HEADER]		= { .type = NLA_NESTED },
+	[ETHTOOL_A_RINGS_RX_MAX]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_RINGS_RX_MINI_MAX]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_RINGS_RX_JUMBO_MAX]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_RINGS_TX_MAX]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_RINGS_RX]			= { .type = NLA_U32 },
+	[ETHTOOL_A_RINGS_RX_MINI]		= { .type = NLA_U32 },
+	[ETHTOOL_A_RINGS_RX_JUMBO]		= { .type = NLA_U32 },
+	[ETHTOOL_A_RINGS_TX]			= { .type = NLA_U32 },
+};
+
+int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info)
+{
+	struct nlattr *tb[ETHTOOL_A_RINGS_MAX + 1];
+	struct ethtool_ringparam ringparam = {};
+	struct ethnl_req_info req_info = {};
+	const struct nlattr *err_attr;
+	const struct ethtool_ops *ops;
+	struct net_device *dev;
+	bool mod = false;
+	int ret;
+
+	ret = nlmsg_parse(info->nlhdr, GENL_HDRLEN, tb,
+			  ETHTOOL_A_RINGS_MAX, rings_set_policy,
+			  info->extack);
+	if (ret < 0)
+		return ret;
+	ret = ethnl_parse_header_dev_get(&req_info,
+					 tb[ETHTOOL_A_RINGS_HEADER],
+					 genl_info_net(info), info->extack,
+					 true);
+	if (ret < 0)
+		return ret;
+	dev = req_info.dev;
+	ops = dev->ethtool_ops;
+	ret = -EOPNOTSUPP;
+	if (!ops->get_ringparam || !ops->set_ringparam)
+		goto out_dev;
+
+	rtnl_lock();
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto out_rtnl;
+	ops->get_ringparam(dev, &ringparam);
+
+	ethnl_update_u32(&ringparam.rx_pending, tb[ETHTOOL_A_RINGS_RX], &mod);
+	ethnl_update_u32(&ringparam.rx_mini_pending,
+			 tb[ETHTOOL_A_RINGS_RX_MINI], &mod);
+	ethnl_update_u32(&ringparam.rx_jumbo_pending,
+			 tb[ETHTOOL_A_RINGS_RX_JUMBO], &mod);
+	ethnl_update_u32(&ringparam.tx_pending, tb[ETHTOOL_A_RINGS_TX], &mod);
+	ret = 0;
+	if (!mod)
+		goto out_ops;
+
+	/* ensure new ring parameters are within limits */
+	if (ringparam.rx_pending > ringparam.rx_max_pending)
+		err_attr = tb[ETHTOOL_A_RINGS_RX];
+	else if (ringparam.rx_mini_pending > ringparam.rx_mini_max_pending)
+		err_attr = tb[ETHTOOL_A_RINGS_RX_MINI];
+	else if (ringparam.rx_jumbo_pending > ringparam.rx_jumbo_max_pending)
+		err_attr = tb[ETHTOOL_A_RINGS_RX_JUMBO];
+	else if (ringparam.tx_pending > ringparam.tx_max_pending)
+		err_attr = tb[ETHTOOL_A_RINGS_TX];
+	else
+		err_attr = NULL;
+	if (err_attr) {
+		ret = -EINVAL;
+		NL_SET_ERR_MSG_ATTR(info->extack, err_attr,
+				    "requested ring size exceeeds maximum");
+		goto out_ops;
+	}
+
+	ret = dev->ethtool_ops->set_ringparam(dev, &ringparam);
+
+out_ops:
+	ethnl_ops_complete(dev);
+out_rtnl:
+	rtnl_unlock();
+out_dev:
+	dev_put(dev);
+	return ret;
+}