[RFC net-next v2 2/6] ethtool: Add loopback GET/SET netlink implementation

["Björn Töpel" <bjorn@kernel.org>]

Add the kernel-side ETHTOOL_MSG_LOOPBACK_GET,
ETHTOOL_MSG_LOOPBACK_SET, and ETHTOOL_MSG_LOOPBACK_NTF handlers using
the standard ethnl_request_ops infrastructure.

GET collects loopback entries from per-component helpers via
loopback_get_entries(). SET parses the nested entry attributes,
dispatches each to loopback_set_one(), and only sends a notification
when the state is changed.

No components are wired yet.

Signed-off-by: Björn Töpel <bjorn@kernel.org>
---
 include/linux/ethtool.h |  28 +++++
 net/ethtool/Makefile    |   2 +-
 net/ethtool/loopback.c  | 246 ++++++++++++++++++++++++++++++++++++++++
 net/ethtool/netlink.c   |  20 ++++
 net/ethtool/netlink.h   |   3 +
 5 files changed, 298 insertions(+), 1 deletion(-)
 create mode 100644 net/ethtool/loopback.c

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 83c375840835..b1ebfe22c355 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -846,6 +846,34 @@ void ethtool_mmsv_set_mm(struct ethtool_mmsv *mmsv, struct ethtool_mm_cfg *cfg);
 void ethtool_mmsv_init(struct ethtool_mmsv *mmsv, struct net_device *dev,
 		       const struct ethtool_mmsv_ops *ops);
 
+/**
+ * struct ethtool_loopback_entry - Per-component loopback configuration
+ * @id: Optional component instance identifier, 0 means not specified
+ * @supported: Bitmask of supported directions
+ * @component: Loopback component
+ * @direction: Current loopback direction, 0 means disabled
+ * @name: Subsystem-specific name for the loopback point
+ */
+struct ethtool_loopback_entry {
+	enum ethtool_loopback_component component;
+	u32 id;
+	u32 supported;
+	u32 direction;
+	char name[ETH_GSTRING_LEN];
+};
+
+#define ETHTOOL_LOOPBACK_MAX_ENTRIES	16
+
+/**
+ * struct ethtool_loopback_cfg - Loopback configuration
+ * @entries: Array of per-component loopback configurations
+ * @n_entries: Number of valid entries in the array
+ */
+struct ethtool_loopback_cfg {
+	struct ethtool_loopback_entry entries[ETHTOOL_LOOPBACK_MAX_ENTRIES];
+	u32 n_entries;
+};
+
 /**
  * struct ethtool_rxfh_param - RXFH (RSS) parameters
  * @hfunc: Defines the current RSS hash function used by HW (or to be set to).
diff --git a/net/ethtool/Makefile b/net/ethtool/Makefile
index 629c10916670..ef534b55d724 100644
--- a/net/ethtool/Makefile
+++ b/net/ethtool/Makefile
@@ -9,4 +9,4 @@ ethtool_nl-y	:= netlink.o bitset.o strset.o linkinfo.o linkmodes.o rss.o \
 		   channels.o coalesce.o pause.o eee.o tsinfo.o cabletest.o \
 		   tunnels.o fec.o eeprom.o stats.o phc_vclocks.o mm.o \
 		   module.o cmis_fw_update.o cmis_cdb.o pse-pd.o plca.o \
-		   phy.o tsconfig.o mse.o
+		   phy.o tsconfig.o mse.o loopback.o
diff --git a/net/ethtool/loopback.c b/net/ethtool/loopback.c
new file mode 100644
index 000000000000..1c6d27857f8a
--- /dev/null
+++ b/net/ethtool/loopback.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "netlink.h"
+#include "common.h"
+
+struct loopback_req_info {
+	struct ethnl_req_info base;
+};
+
+struct loopback_reply_data {
+	struct ethnl_reply_data base;
+	struct ethtool_loopback_cfg cfg;
+};
+
+#define LOOPBACK_REPDATA(__reply_base) \
+	container_of(__reply_base, struct loopback_reply_data, base)
+
+/* GET */
+
+static const struct nla_policy
+ethnl_loopback_entry_policy[ETHTOOL_A_LOOPBACK_ENTRY_MAX + 1] = {
+	[ETHTOOL_A_LOOPBACK_ENTRY_COMPONENT] =
+		NLA_POLICY_MAX(NLA_U32, ETHTOOL_LOOPBACK_COMPONENT_MODULE),
+	[ETHTOOL_A_LOOPBACK_ENTRY_ID] =
+		NLA_POLICY_MIN(NLA_U32, 1),
+	[ETHTOOL_A_LOOPBACK_ENTRY_NAME] =
+		{ .type = NLA_NUL_STRING, .len = ETH_GSTRING_LEN - 1 },
+	[ETHTOOL_A_LOOPBACK_ENTRY_DIRECTION] =
+		NLA_POLICY_MASK(NLA_U32, ETHTOOL_LOOPBACK_DIRECTION_NEAR_END |
+				ETHTOOL_LOOPBACK_DIRECTION_FAR_END),
+};
+
+const struct nla_policy ethnl_loopback_get_policy[] = {
+	[ETHTOOL_A_LOOPBACK_HEADER] = NLA_POLICY_NESTED(ethnl_header_policy),
+};
+
+static int loopback_get_entries(struct net_device *dev,
+				struct ethtool_loopback_cfg *cfg)
+{
+	return 0;
+}
+
+static int loopback_prepare_data(const struct ethnl_req_info *req_base,
+				 struct ethnl_reply_data *reply_base,
+				 const struct genl_info *info)
+{
+	struct loopback_reply_data *data = LOOPBACK_REPDATA(reply_base);
+	struct net_device *dev = reply_base->dev;
+	int ret;
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		return ret;
+
+	ret = loopback_get_entries(dev, &data->cfg);
+
+	ethnl_ops_complete(dev);
+
+	return ret;
+}
+
+static int loopback_reply_size(const struct ethnl_req_info *req_base,
+			       const struct ethnl_reply_data *reply_base)
+{
+	const struct loopback_reply_data *data = LOOPBACK_REPDATA(reply_base);
+	int entry_size;
+
+	/* Per-entry: nest + component + id + name + supported + direction */
+	entry_size = nla_total_size(0) +		/* nest */
+		nla_total_size(sizeof(u32)) +		/* component */
+		nla_total_size(sizeof(u32)) +		/* id */
+		nla_total_size(sizeof(u32)) +		/* supported */
+		nla_total_size(sizeof(u32)) +		/* direction */
+		nla_total_size(ETH_GSTRING_LEN);	/* name */
+
+	return data->cfg.n_entries * entry_size;
+}
+
+static int loopback_fill_entry(struct sk_buff *skb,
+			       const struct ethtool_loopback_entry *entry)
+{
+	struct nlattr *nest;
+
+	nest = nla_nest_start(skb, ETHTOOL_A_LOOPBACK_ENTRY);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(skb, ETHTOOL_A_LOOPBACK_ENTRY_COMPONENT,
+			entry->component))
+		goto err_cancel;
+
+	if (entry->id &&
+	    nla_put_u32(skb, ETHTOOL_A_LOOPBACK_ENTRY_ID, entry->id))
+		goto err_cancel;
+
+	if (nla_put_u32(skb, ETHTOOL_A_LOOPBACK_ENTRY_SUPPORTED,
+			entry->supported) ||
+	    nla_put_u32(skb, ETHTOOL_A_LOOPBACK_ENTRY_DIRECTION,
+			entry->direction) ||
+	    nla_put_string(skb, ETHTOOL_A_LOOPBACK_ENTRY_NAME,
+			   entry->name))
+		goto err_cancel;
+
+	nla_nest_end(skb, nest);
+	return 0;
+
+err_cancel:
+	nla_nest_cancel(skb, nest);
+	return -EMSGSIZE;
+}
+
+static int loopback_fill_reply(struct sk_buff *skb,
+			       const struct ethnl_req_info *req_base,
+			       const struct ethnl_reply_data *reply_base)
+{
+	const struct loopback_reply_data *data = LOOPBACK_REPDATA(reply_base);
+	const struct ethtool_loopback_cfg *cfg = &data->cfg;
+	u32 i;
+
+	for (i = 0; i < cfg->n_entries; i++) {
+		int ret = loopback_fill_entry(skb, &cfg->entries[i]);
+
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+/* SET */
+
+const struct nla_policy ethnl_loopback_set_policy[ETHTOOL_A_LOOPBACK_ENTRY + 1] = {
+	[ETHTOOL_A_LOOPBACK_HEADER] = NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_LOOPBACK_ENTRY]  = NLA_POLICY_NESTED(ethnl_loopback_entry_policy),
+};
+
+static int loopback_parse_entry(struct nlattr *attr,
+				struct ethtool_loopback_entry *entry,
+				struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[ETHTOOL_A_LOOPBACK_ENTRY_MAX + 1];
+	int ret;
+
+	ret = nla_parse_nested(tb, ETHTOOL_A_LOOPBACK_ENTRY_MAX, attr,
+			       ethnl_loopback_entry_policy, extack);
+	if (ret < 0)
+		return ret;
+
+	if (!tb[ETHTOOL_A_LOOPBACK_ENTRY_COMPONENT]) {
+		NL_SET_ERR_MSG_ATTR(extack, attr,
+				    "loopback component is required");
+		return -EINVAL;
+	}
+
+	entry->component = nla_get_u32(tb[ETHTOOL_A_LOOPBACK_ENTRY_COMPONENT]);
+
+	if (tb[ETHTOOL_A_LOOPBACK_ENTRY_ID])
+		entry->id = nla_get_u32(tb[ETHTOOL_A_LOOPBACK_ENTRY_ID]);
+
+	if (!tb[ETHTOOL_A_LOOPBACK_ENTRY_NAME]) {
+		NL_SET_ERR_MSG_ATTR(extack, attr,
+				    "loopback name is required");
+		return -EINVAL;
+	}
+	nla_strscpy(entry->name, tb[ETHTOOL_A_LOOPBACK_ENTRY_NAME],
+		    sizeof(entry->name));
+
+	if (!tb[ETHTOOL_A_LOOPBACK_ENTRY_DIRECTION]) {
+		NL_SET_ERR_MSG_ATTR(extack, attr,
+				    "loopback direction is required");
+		return -EINVAL;
+	}
+
+	entry->direction = nla_get_u32(tb[ETHTOOL_A_LOOPBACK_ENTRY_DIRECTION]);
+
+	return 0;
+}
+
+static int loopback_set_one(struct net_device *dev,
+			    const struct ethtool_loopback_entry *entry,
+			    struct netlink_ext_ack *extack)
+{
+	switch (entry->component) {
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int ethnl_set_loopback(struct ethnl_req_info *req_info,
+			      struct genl_info *info)
+{
+	struct net_device *dev = req_info->dev;
+	struct ethtool_loopback_cfg cfg = {};
+	int rem, ret, mod = 0;
+	struct nlattr *attr;
+	u32 i;
+
+	nla_for_each_attr(attr, genlmsg_data(info->genlhdr),
+			  genlmsg_len(info->genlhdr), rem) {
+		if (nla_type(attr) != ETHTOOL_A_LOOPBACK_ENTRY)
+			continue;
+
+		if (cfg.n_entries >= ETHTOOL_LOOPBACK_MAX_ENTRIES) {
+			NL_SET_ERR_MSG(info->extack,
+				       "too many loopback entries");
+			return -EINVAL;
+		}
+
+		ret = loopback_parse_entry(attr, &cfg.entries[cfg.n_entries],
+					   info->extack);
+		if (ret < 0)
+			return ret;
+
+		cfg.n_entries++;
+	}
+
+	if (!cfg.n_entries) {
+		NL_SET_ERR_MSG(info->extack, "no loopback entries specified");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < cfg.n_entries; i++) {
+		ret = loopback_set_one(dev, &cfg.entries[i], info->extack);
+		if (ret < 0)
+			return ret;
+		if (ret > 0)
+			mod = 1;
+	}
+
+	return mod;
+}
+
+const struct ethnl_request_ops ethnl_loopback_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_LOOPBACK_GET,
+	.reply_cmd		= ETHTOOL_MSG_LOOPBACK_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_LOOPBACK_HEADER,
+	.req_info_size		= sizeof(struct loopback_req_info),
+	.reply_data_size	= sizeof(struct loopback_reply_data),
+
+	.prepare_data		= loopback_prepare_data,
+	.reply_size		= loopback_reply_size,
+	.fill_reply		= loopback_fill_reply,
+
+	.set			= ethnl_set_loopback,
+	.set_ntf_cmd		= ETHTOOL_MSG_LOOPBACK_NTF,
+};
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 6e5f0f4f815a..c438828ea072 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -421,6 +421,8 @@ ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_TSCONFIG_SET]	= &ethnl_tsconfig_request_ops,
 	[ETHTOOL_MSG_PHY_GET]		= &ethnl_phy_request_ops,
 	[ETHTOOL_MSG_MSE_GET]		= &ethnl_mse_request_ops,
+	[ETHTOOL_MSG_LOOPBACK_GET]	= &ethnl_loopback_request_ops,
+	[ETHTOOL_MSG_LOOPBACK_SET]	= &ethnl_loopback_request_ops,
 };
 
 static struct ethnl_dump_ctx *ethnl_dump_context(struct netlink_callback *cb)
@@ -962,6 +964,7 @@ ethnl_default_notify_ops[ETHTOOL_MSG_KERNEL_MAX + 1] = {
 	[ETHTOOL_MSG_MM_NTF]		= &ethnl_mm_request_ops,
 	[ETHTOOL_MSG_RSS_NTF]		= &ethnl_rss_request_ops,
 	[ETHTOOL_MSG_RSS_CREATE_NTF]	= &ethnl_rss_request_ops,
+	[ETHTOOL_MSG_LOOPBACK_NTF]	= &ethnl_loopback_request_ops,
 };
 
 /* default notification handler */
@@ -1070,6 +1073,7 @@ static const ethnl_notify_handler_t ethnl_notify_handlers[] = {
 	[ETHTOOL_MSG_MM_NTF]		= ethnl_default_notify,
 	[ETHTOOL_MSG_RSS_NTF]		= ethnl_default_notify,
 	[ETHTOOL_MSG_RSS_CREATE_NTF]	= ethnl_default_notify,
+	[ETHTOOL_MSG_LOOPBACK_NTF]	= ethnl_default_notify,
 };
 
 void ethnl_notify(struct net_device *dev, unsigned int cmd,
@@ -1544,6 +1548,22 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.policy = ethnl_mse_get_policy,
 		.maxattr = ARRAY_SIZE(ethnl_mse_get_policy) - 1,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_LOOPBACK_GET,
+		.doit	= ethnl_default_doit,
+		.start	= ethnl_default_start,
+		.dumpit	= ethnl_default_dumpit,
+		.done	= ethnl_default_done,
+		.policy = ethnl_loopback_get_policy,
+		.maxattr = ARRAY_SIZE(ethnl_loopback_get_policy) - 1,
+	},
+	{
+		.cmd	= ETHTOOL_MSG_LOOPBACK_SET,
+		.flags	= GENL_UNS_ADMIN_PERM,
+		.doit	= ethnl_default_set_doit,
+		.policy = ethnl_loopback_set_policy,
+		.maxattr = ARRAY_SIZE(ethnl_loopback_set_policy) - 1,
+	},
 };
 
 static const struct genl_multicast_group ethtool_nl_mcgrps[] = {
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 89010eaa67df..5660ce494916 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -443,6 +443,7 @@ extern const struct ethnl_request_ops ethnl_mm_request_ops;
 extern const struct ethnl_request_ops ethnl_phy_request_ops;
 extern const struct ethnl_request_ops ethnl_tsconfig_request_ops;
 extern const struct ethnl_request_ops ethnl_mse_request_ops;
+extern const struct ethnl_request_ops ethnl_loopback_request_ops;
 
 extern const struct nla_policy ethnl_header_policy[ETHTOOL_A_HEADER_FLAGS + 1];
 extern const struct nla_policy ethnl_header_policy_stats[ETHTOOL_A_HEADER_FLAGS + 1];
@@ -499,6 +500,8 @@ extern const struct nla_policy ethnl_phy_get_policy[ETHTOOL_A_PHY_HEADER + 1];
 extern const struct nla_policy ethnl_tsconfig_get_policy[ETHTOOL_A_TSCONFIG_HEADER + 1];
 extern const struct nla_policy ethnl_tsconfig_set_policy[ETHTOOL_A_TSCONFIG_MAX + 1];
 extern const struct nla_policy ethnl_mse_get_policy[ETHTOOL_A_MSE_HEADER + 1];
+extern const struct nla_policy ethnl_loopback_get_policy[ETHTOOL_A_LOOPBACK_HEADER + 1];
+extern const struct nla_policy ethnl_loopback_set_policy[ETHTOOL_A_LOOPBACK_ENTRY + 1];
 
 int ethnl_set_features(struct sk_buff *skb, struct genl_info *info);
 int ethnl_act_cable_test(struct sk_buff *skb, struct genl_info *info);
-- 
2.53.0