ethtool: rss: support removing contexts via Netlink

Implement removing additional RSS contexts via Netlink.
Technically it'd be possible to shoehorn the delete operation
into ethnl_request_ops-compatible handler. The code ends
up longer than open coded version, and I think we'll need
a custom way of sending notifications at some stage (if we
allow tying the context lifetime to the netlink socket, in
the future).

Link: https://patch.msgid.link/20250717234343.2328602-8-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ethtool/common.c

@@ -1136,5 +1136,6 @@ void ethtool_rxfh_context_lost(struct net_device *dev, u32 context_id)
 	netdev_err(dev, "device error, RSS context %d lost\n", context_id);
 	ctx = xa_erase(&dev->ethtool->rss_ctx, context_id);
 	kfree(ctx);
+	ethtool_rss_notify(dev, ETHTOOL_MSG_RSS_DELETE_NTF, context_id);
 }
 EXPORT_SYMBOL(ethtool_rxfh_context_lost);

net/ethtool/ioctl.c

@@ -1647,6 +1647,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 			     !memchr_inv(ethtool_rxfh_context_key(ctx), 0,
 					 ctx->key_size));
 	} else if (rxfh_dev.rss_delete) {
+		ntf = ETHTOOL_MSG_RSS_DELETE_NTF;
 		ret = ops->remove_rxfh_context(dev, ctx, rxfh.rss_context,
 					       extack);
 	} else {

net/ethtool/netlink.c

@@ -1527,6 +1527,13 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.policy	= ethnl_rss_create_policy,
 		.maxattr = ARRAY_SIZE(ethnl_rss_create_policy) - 1,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_RSS_DELETE_ACT,
+		.flags	= GENL_UNS_ADMIN_PERM,
+		.doit	= ethnl_rss_delete_doit,
+		.policy	= ethnl_rss_delete_policy,
+		.maxattr = ARRAY_SIZE(ethnl_rss_delete_policy) - 1,
+	},
 };
 
 static const struct genl_multicast_group ethtool_nl_mcgrps[] = {

net/ethtool/netlink.h

@@ -487,6 +487,7 @@ extern const struct nla_policy ethnl_pse_set_policy[ETHTOOL_A_PSE_MAX + 1];
 extern const struct nla_policy ethnl_rss_get_policy[ETHTOOL_A_RSS_START_CONTEXT + 1];
 extern const struct nla_policy ethnl_rss_set_policy[ETHTOOL_A_RSS_FLOW_HASH + 1];
 extern const struct nla_policy ethnl_rss_create_policy[ETHTOOL_A_RSS_INPUT_XFRM + 1];
+extern const struct nla_policy ethnl_rss_delete_policy[ETHTOOL_A_RSS_CONTEXT + 1];
 extern const struct nla_policy ethnl_plca_get_cfg_policy[ETHTOOL_A_PLCA_HEADER + 1];
 extern const struct nla_policy ethnl_plca_set_cfg_policy[ETHTOOL_A_PLCA_MAX + 1];
 extern const struct nla_policy ethnl_plca_get_status_policy[ETHTOOL_A_PLCA_HEADER + 1];
@@ -510,6 +511,7 @@ int ethnl_tsinfo_start(struct netlink_callback *cb);
 int ethnl_tsinfo_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
 int ethnl_tsinfo_done(struct netlink_callback *cb);
 int ethnl_rss_create_doit(struct sk_buff *skb, struct genl_info *info);
+int ethnl_rss_delete_doit(struct sk_buff *skb, struct genl_info *info);
 
 extern const char stats_std_names[__ETHTOOL_STATS_CNT][ETH_GSTRING_LEN];
 extern const char stats_eth_phy_names[__ETHTOOL_A_STATS_ETH_PHY_CNT][ETH_GSTRING_LEN];

net/ethtool/rss.c

@@ -486,13 +486,49 @@ int ethnl_rss_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 
 /* RSS_NTF */
 
+static void ethnl_rss_delete_notify(struct net_device *dev, u32 rss_context)
+{
+	struct sk_buff *ntf;
+	size_t ntf_size;
+	void *hdr;
+
+	ntf_size = ethnl_reply_header_size() +
+		nla_total_size(sizeof(u32));	/* _RSS_CONTEXT */
+
+	ntf = genlmsg_new(ntf_size, GFP_KERNEL);
+	if (!ntf)
+		goto out_warn;
+
+	hdr = ethnl_bcastmsg_put(ntf, ETHTOOL_MSG_RSS_DELETE_NTF);
+	if (!hdr)
+		goto out_free_ntf;
+
+	if (ethnl_fill_reply_header(ntf, dev, ETHTOOL_A_RSS_HEADER) ||
+	    nla_put_u32(ntf, ETHTOOL_A_RSS_CONTEXT, rss_context))
+		goto out_free_ntf;
+
+	genlmsg_end(ntf, hdr);
+	if (ethnl_multicast(ntf, dev))
+		goto out_warn;
+
+	return;
+
+out_free_ntf:
+	nlmsg_free(ntf);
+out_warn:
+	pr_warn_once("Failed to send a RSS delete notification");
+}
+
 void ethtool_rss_notify(struct net_device *dev, u32 type, u32 rss_context)
 {
 	struct rss_req_info req_info = {
 		.rss_context = rss_context,
 	};
 
-	ethnl_notify(dev, type, &req_info.base);
+	if (type == ETHTOOL_MSG_RSS_DELETE_NTF)
+		ethnl_rss_delete_notify(dev, rss_context);
+	else
+		ethnl_notify(dev, type, &req_info.base);
 }
 
 /* RSS_SET */
@@ -1096,3 +1132,74 @@ err_unlock_free_ctx:
 	kfree(ctx);
 	goto exit_unlock;
 }
+
+/* RSS_DELETE */
+
+const struct nla_policy ethnl_rss_delete_policy[ETHTOOL_A_RSS_CONTEXT + 1] = {
+	[ETHTOOL_A_RSS_HEADER]	= NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_RSS_CONTEXT]	= NLA_POLICY_MIN(NLA_U32, 1),
+};
+
+int ethnl_rss_delete_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ethtool_rxfh_context *ctx;
+	struct nlattr **tb = info->attrs;
+	struct ethnl_req_info req = {};
+	const struct ethtool_ops *ops;
+	struct net_device *dev;
+	u32 rss_context;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, ETHTOOL_A_RSS_CONTEXT))
+		return -EINVAL;
+	rss_context = nla_get_u32(tb[ETHTOOL_A_RSS_CONTEXT]);
+
+	ret = ethnl_parse_header_dev_get(&req, tb[ETHTOOL_A_RSS_HEADER],
+					 genl_info_net(info), info->extack,
+					 true);
+	if (ret < 0)
+		return ret;
+
+	dev = req.dev;
+	ops = dev->ethtool_ops;
+
+	if (!ops->create_rxfh_context)
+		goto exit_free_dev;
+
+	rtnl_lock();
+	netdev_lock_ops(dev);
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto exit_dev_unlock;
+
+	mutex_lock(&dev->ethtool->rss_lock);
+	ret = ethtool_check_rss_ctx_busy(dev, rss_context);
+	if (ret)
+		goto exit_unlock;
+
+	ctx = xa_load(&dev->ethtool->rss_ctx, rss_context);
+	if (!ctx) {
+		ret = -ENOENT;
+		goto exit_unlock;
+	}
+
+	ret = ops->remove_rxfh_context(dev, ctx, rss_context, info->extack);
+	if (ret)
+		goto exit_unlock;
+
+	WARN_ON(xa_erase(&dev->ethtool->rss_ctx, rss_context) != ctx);
+	kfree(ctx);
+
+	ethnl_rss_delete_notify(dev, rss_context);
+
+exit_unlock:
+	mutex_unlock(&dev->ethtool->rss_lock);
+	ethnl_ops_complete(dev);
+exit_dev_unlock:
+	netdev_unlock_ops(dev);
+	rtnl_unlock();
+exit_free_dev:
+	ethnl_parse_header_dev_put(&req);
+	return ret;
+}