ethtool: set link settings with LINKINFO_SET request

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.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ethtool-netlink.rst

@@ -181,6 +181,7 @@ Userspace to kernel:
   ===================================== ================================
   ``ETHTOOL_MSG_STRSET_GET``            get string set
   ``ETHTOOL_MSG_LINKINFO_GET``          get link settings
+  ``ETHTOOL_MSG_LINKINFO_SET``          set link settings
   ===================================== ================================
 
 Kernel to userspace:
@@ -311,6 +312,25 @@ corresponding ioctl structures.
 devices supporting the request).
 
 
+LINKINFO_SET
+============
+
+``LINKINFO_SET`` request allows setting some of the attributes reported by
+``LINKINFO_GET``.
+
+Request contents:
+
+  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKINFO_HEADER``         nested  request header
+  ``ETHTOOL_A_LINKINFO_PORT``           u8      physical port
+  ``ETHTOOL_A_LINKINFO_PHYADDR``        u8      phy MDIO address
+  ``ETHTOOL_A_LINKINFO_TP_MDIX_CTRL``   u8      MDI(-X) control
+  ====================================  ======  ==========================
+
+MDI(-X) status and transceiver cannot be set, request with the corresponding
+attributes is rejected.
+
+
 Request translation
 ===================
 
@@ -322,7 +342,7 @@ have their netlink replacement yet.
   ioctl command                       netlink command
   =================================== =====================================
   ``ETHTOOL_GSET``                    ``ETHTOOL_MSG_LINKINFO_GET``
-  ``ETHTOOL_SSET``                    n/a
+  ``ETHTOOL_SSET``                    ``ETHTOOL_MSG_LINKINFO_SET``
   ``ETHTOOL_GDRVINFO``                n/a
   ``ETHTOOL_GREGS``                   n/a
   ``ETHTOOL_GWOL``                    n/a
@@ -396,7 +416,7 @@ have their netlink replacement yet.
   ``ETHTOOL_GPHYSTATS``               n/a
   ``ETHTOOL_PERQUEUE``                n/a
   ``ETHTOOL_GLINKSETTINGS``           ``ETHTOOL_MSG_LINKINFO_GET``
-  ``ETHTOOL_SLINKSETTINGS``           n/a
+  ``ETHTOOL_SLINKSETTINGS``           ``ETHTOOL_MSG_LINKINFO_SET``
   ``ETHTOOL_PHY_GTUNABLE``            n/a
   ``ETHTOOL_PHY_STUNABLE``            n/a
   ``ETHTOOL_GFECPARAM``               n/a

include/uapi/linux/ethtool_netlink.h

@@ -16,6 +16,7 @@ enum {
 	ETHTOOL_MSG_USER_NONE,
 	ETHTOOL_MSG_STRSET_GET,
 	ETHTOOL_MSG_LINKINFO_GET,
+	ETHTOOL_MSG_LINKINFO_SET,
 
 	/* add new constants above here */
 	__ETHTOOL_MSG_USER_CNT,

net/ethtool/linkinfo.c

@@ -92,3 +92,74 @@ const struct ethnl_request_ops ethnl_linkinfo_request_ops = {
 	.reply_size		= linkinfo_reply_size,
 	.fill_reply		= linkinfo_fill_reply,
 };
+
+/* LINKINFO_SET */
+
+static const struct nla_policy
+linkinfo_set_policy[ETHTOOL_A_LINKINFO_MAX + 1] = {
+	[ETHTOOL_A_LINKINFO_UNSPEC]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_LINKINFO_HEADER]		= { .type = NLA_NESTED },
+	[ETHTOOL_A_LINKINFO_PORT]		= { .type = NLA_U8 },
+	[ETHTOOL_A_LINKINFO_PHYADDR]		= { .type = NLA_U8 },
+	[ETHTOOL_A_LINKINFO_TP_MDIX]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_LINKINFO_TP_MDIX_CTRL]	= { .type = NLA_U8 },
+	[ETHTOOL_A_LINKINFO_TRANSCEIVER]	= { .type = NLA_REJECT },
+};
+
+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);
+	if (ret < 0)
+		return ret;
+	ret = ethnl_parse_header(&req_info, tb[ETHTOOL_A_LINKINFO_HEADER],
+				 genl_info_net(info), info->extack, true);
+	if (ret < 0)
+		return ret;
+	dev = req_info.dev;
+	if (!dev->ethtool_ops->get_link_ksettings ||
+	    !dev->ethtool_ops->set_link_ksettings)
+		return -EOPNOTSUPP;
+
+	rtnl_lock();
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto out_rtnl;
+
+	ret = __ethtool_get_link_ksettings(dev, &ksettings);
+	if (ret < 0) {
+		if (info)
+			GENL_SET_ERR_MSG(info, "failed to retrieve link settings");
+		goto out_ops;
+	}
+	lsettings = &ksettings.base;
+
+	ethnl_update_u8(&lsettings->port, tb[ETHTOOL_A_LINKINFO_PORT], &mod);
+	ethnl_update_u8(&lsettings->phy_address, tb[ETHTOOL_A_LINKINFO_PHYADDR],
+			&mod);
+	ethnl_update_u8(&lsettings->eth_tp_mdix_ctrl,
+			tb[ETHTOOL_A_LINKINFO_TP_MDIX_CTRL], &mod);
+	ret = 0;
+	if (!mod)
+		goto out_ops;
+
+	ret = dev->ethtool_ops->set_link_ksettings(dev, &ksettings);
+	if (ret < 0)
+		GENL_SET_ERR_MSG(info, "link settings update failed");
+
+out_ops:
+	ethnl_ops_complete(dev);
+out_rtnl:
+	rtnl_unlock();
+	dev_put(dev);
+	return ret;
+}

net/ethtool/netlink.c

@@ -534,6 +534,11 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.dumpit	= ethnl_default_dumpit,
 		.done	= ethnl_default_done,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_LINKINFO_SET,
+		.flags	= GENL_UNS_ADMIN_PERM,
+		.doit	= ethnl_set_linkinfo,
+	},
 };
 
 static const struct genl_multicast_group ethtool_nl_mcgrps[] = {

net/ethtool/netlink.h

@@ -331,4 +331,6 @@ struct ethnl_request_ops {
 extern const struct ethnl_request_ops ethnl_strset_request_ops;
 extern const struct ethnl_request_ops ethnl_linkinfo_request_ops;
 
+int ethnl_set_linkinfo(struct sk_buff *skb, struct genl_info *info);
+
 #endif /* _NET_ETHTOOL_NETLINK_H */