diff --git a/include/linux/inet_diag.h b/include/linux/inet_diag.h
index 39faaaf843e1..c91cf2dee12a 100644
--- a/include/linux/inet_diag.h
+++ b/include/linux/inet_diag.h
@@ -2,15 +2,10 @@
 #ifndef _INET_DIAG_H_
 #define _INET_DIAG_H_ 1
 
+#include <net/netlink.h>
 #include <uapi/linux/inet_diag.h>
 
-struct net;
-struct sock;
 struct inet_hashinfo;
-struct nlattr;
-struct nlmsghdr;
-struct sk_buff;
-struct netlink_callback;
 
 struct inet_diag_handler {
 	void		(*dump)(struct sk_buff *skb,
@@ -62,6 +57,17 @@ int inet_diag_bc_sk(const struct nlattr *_bc, struct sock *sk);
 
 void inet_diag_msg_common_fill(struct inet_diag_msg *r, struct sock *sk);
 
+static inline size_t inet_diag_msg_attrs_size(void)
+{
+	return	  nla_total_size(1)  /* INET_DIAG_SHUTDOWN */
+		+ nla_total_size(1)  /* INET_DIAG_TOS */
+#if IS_ENABLED(CONFIG_IPV6)
+		+ nla_total_size(1)  /* INET_DIAG_TCLASS */
+		+ nla_total_size(1)  /* INET_DIAG_SKV6ONLY */
+#endif
+		+ nla_total_size(4)  /* INET_DIAG_MARK */
+		+ nla_total_size(4); /* INET_DIAG_CLASS_ID */
+}
 int inet_diag_msg_attrs_fill(struct sock *sk, struct sk_buff *skb,
 			     struct inet_diag_msg *r, int ext,
 			     struct user_namespace *user_ns, bool net_admin);
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 9742b37afe1d..f0957ebf82cf 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -104,13 +104,9 @@ static size_t inet_sk_attr_size(struct sock *sk,
 		aux = handler->idiag_get_aux_size(sk, net_admin);
 
 	return	  nla_total_size(sizeof(struct tcp_info))
-		+ nla_total_size(1) /* INET_DIAG_SHUTDOWN */
-		+ nla_total_size(1) /* INET_DIAG_TOS */
-		+ nla_total_size(1) /* INET_DIAG_TCLASS */
-		+ nla_total_size(4) /* INET_DIAG_MARK */
-		+ nla_total_size(4) /* INET_DIAG_CLASS_ID */
-		+ nla_total_size(sizeof(struct inet_diag_meminfo))
 		+ nla_total_size(sizeof(struct inet_diag_msg))
+		+ inet_diag_msg_attrs_size()
+		+ nla_total_size(sizeof(struct inet_diag_meminfo))
 		+ nla_total_size(SK_MEMINFO_VARS * sizeof(u32))
 		+ nla_total_size(TCP_CA_NAME_MAX)
 		+ nla_total_size(sizeof(struct tcpvegas_info))
@@ -151,6 +147,24 @@ int inet_diag_msg_attrs_fill(struct sock *sk, struct sk_buff *skb,
 	if (net_admin && nla_put_u32(skb, INET_DIAG_MARK, sk->sk_mark))
 		goto errout;
 
+	if (ext & (1 << (INET_DIAG_CLASS_ID - 1)) ||
+	    ext & (1 << (INET_DIAG_TCLASS - 1))) {
+		u32 classid = 0;
+
+#ifdef CONFIG_SOCK_CGROUP_DATA
+		classid = sock_cgroup_classid(&sk->sk_cgrp_data);
+#endif
+		/* Fallback to socket priority if class id isn't set.
+		 * Classful qdiscs use it as direct reference to class.
+		 * For cgroup2 classid is always zero.
+		 */
+		if (!classid)
+			classid = sk->sk_priority;
+
+		if (nla_put_u32(skb, INET_DIAG_CLASS_ID, classid))
+			goto errout;
+	}
+
 	r->idiag_uid = from_kuid_munged(user_ns, sock_i_uid(sk));
 	r->idiag_inode = sock_i_ino(sk);
 
@@ -288,24 +302,6 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
 			goto errout;
 	}
 
-	if (ext & (1 << (INET_DIAG_CLASS_ID - 1)) ||
-	    ext & (1 << (INET_DIAG_TCLASS - 1))) {
-		u32 classid = 0;
-
-#ifdef CONFIG_SOCK_CGROUP_DATA
-		classid = sock_cgroup_classid(&sk->sk_cgrp_data);
-#endif
-		/* Fallback to socket priority if class id isn't set.
-		 * Classful qdiscs use it as direct reference to class.
-		 * For cgroup2 classid is always zero.
-		 */
-		if (!classid)
-			classid = sk->sk_priority;
-
-		if (nla_put_u32(skb, INET_DIAG_CLASS_ID, classid))
-			goto errout;
-	}
-
 out:
 	nlmsg_end(skb, nlh);
 	return 0;
diff --git a/net/ipv4/raw_diag.c b/net/ipv4/raw_diag.c
index 6367ecdf76c4..1d84b02ec765 100644
--- a/net/ipv4/raw_diag.c
+++ b/net/ipv4/raw_diag.c
@@ -99,8 +99,9 @@ static int raw_diag_dump_one(struct sk_buff *in_skb,
 	if (IS_ERR(sk))
 		return PTR_ERR(sk);
 
-	rep = nlmsg_new(sizeof(struct inet_diag_msg) +
-			sizeof(struct inet_diag_meminfo) + 64,
+	rep = nlmsg_new(nla_total_size(sizeof(struct inet_diag_msg)) +
+			inet_diag_msg_attrs_size() +
+			nla_total_size(sizeof(struct inet_diag_meminfo)) + 64,
 			GFP_KERNEL);
 	if (!rep) {
 		sock_put(sk);
diff --git a/net/ipv4/udp_diag.c b/net/ipv4/udp_diag.c
index d9ad986c7b2c..cc3f6da306c6 100644
--- a/net/ipv4/udp_diag.c
+++ b/net/ipv4/udp_diag.c
@@ -67,8 +67,9 @@ static int udp_dump_one(struct udp_table *tbl, struct sk_buff *in_skb,
 		goto out;
 
 	err = -ENOMEM;
-	rep = nlmsg_new(sizeof(struct inet_diag_msg) +
-			sizeof(struct inet_diag_meminfo) + 64,
+	rep = nlmsg_new(nla_total_size(sizeof(struct inet_diag_msg)) +
+			inet_diag_msg_attrs_size() +
+			nla_total_size(sizeof(struct inet_diag_meminfo)) + 64,
 			GFP_KERNEL);
 	if (!rep)
 		goto out;
diff --git a/net/sctp/diag.c b/net/sctp/diag.c
index 435847d98b51..8767405de9fa 100644
--- a/net/sctp/diag.c
+++ b/net/sctp/diag.c
@@ -252,15 +252,11 @@ static size_t inet_assoc_attr_size(struct sctp_association *asoc)
 		addrcnt++;
 
 	return	  nla_total_size(sizeof(struct sctp_info))
-		+ nla_total_size(1) /* INET_DIAG_SHUTDOWN */
-		+ nla_total_size(1) /* INET_DIAG_TOS */
-		+ nla_total_size(1) /* INET_DIAG_TCLASS */
-		+ nla_total_size(4) /* INET_DIAG_MARK */
-		+ nla_total_size(4) /* INET_DIAG_CLASS_ID */
 		+ nla_total_size(addrlen * asoc->peer.transport_count)
 		+ nla_total_size(addrlen * addrcnt)
-		+ nla_total_size(sizeof(struct inet_diag_meminfo))
 		+ nla_total_size(sizeof(struct inet_diag_msg))
+		+ inet_diag_msg_attrs_size()
+		+ nla_total_size(sizeof(struct inet_diag_meminfo))
 		+ 64;
 }