docs: cgroup-v2: fix misc.events key format descriptiongrafted

In misc cgroup, misc.events does not output a simple "max" key. Instead,
each registered misc resource outputs a separate key suffixed with ".max"
(i.e., "<res>.max").
Update the documentation to clarify that the entry key is "<res>.max".

Suggested-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Cheng Lingfei <chenglingfei@foxmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/net/ipv4/netlink.c b/net/ipv4/netlink.c
new file mode 100644
index 000000000..b920e1bdc
--- /dev/null
+++ b/net/ipv4/netlink.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <linux/types.h>
+#include <net/net_namespace.h>
+#include <net/netlink.h>
+#include <linux/in6.h>
+#include <net/ip.h>
+
+int rtm_getroute_parse_ip_proto(struct nlattr *attr, u8 *ip_proto, u8 family,
+				struct netlink_ext_ack *extack)
+{
+	*ip_proto = nla_get_u8(attr);
+
+	switch (*ip_proto) {
+	case IPPROTO_TCP:
+	case IPPROTO_UDP:
+		return 0;
+	case IPPROTO_ICMP:
+		if (family != AF_INET)
+			break;
+		return 0;
+#if IS_ENABLED(CONFIG_IPV6)
+	case IPPROTO_ICMPV6:
+		if (family != AF_INET6)
+			break;
+		return 0;
+#endif
+	}
+	NL_SET_ERR_MSG(extack, "Unsupported ip proto");
+	return -EOPNOTSUPP;
+}
+EXPORT_SYMBOL_GPL(rtm_getroute_parse_ip_proto);