diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h
index 4e872af7b180..d5d344d599f7 100644
--- a/include/net/tcp_authopt.h
+++ b/include/net/tcp_authopt.h
@@ -62,10 +62,14 @@ struct tcp_authopt_info {
 	u32 flags;
 	/** @src_isn: Local Initial Sequence Number */
 	u32 src_isn;
 	/** @dst_isn: Remote Initial Sequence Number */
 	u32 dst_isn;
+	/** @rcv_sne: Recv-side Sequence Number Extension tracking tcp_sock.rcv_nxt */
+	u32 rcv_sne;
+	/** @snd_sne: Send-side Sequence Number Extension tracking tcp_sock.snd_nxt */
+	u32 snd_sne;
 };
 
 /* TCP authopt as found in header */
 struct tcphdr_authopt {
 	u8 num;
@@ -180,10 +184,34 @@ static inline int tcp_authopt_inbound_check_req(struct request_sock *req, struct
 		if (info)
 			return __tcp_authopt_inbound_check((struct sock *)req, skb, info, opt);
 	}
 	return 0;
 }
+void __tcp_authopt_update_rcv_sne(struct tcp_sock *tp, struct tcp_authopt_info *info, u32 seq);
+static inline void tcp_authopt_update_rcv_sne(struct tcp_sock *tp, u32 seq)
+{
+	struct tcp_authopt_info *info;
+
+	if (tcp_authopt_needed) {
+		info = rcu_dereference_protected(tp->authopt_info,
+						 lockdep_sock_is_held((struct sock *)tp));
+		if (info)
+			__tcp_authopt_update_rcv_sne(tp, info, seq);
+	}
+}
+void __tcp_authopt_update_snd_sne(struct tcp_sock *tp, struct tcp_authopt_info *info, u32 seq);
+static inline void tcp_authopt_update_snd_sne(struct tcp_sock *tp, u32 seq)
+{
+	struct tcp_authopt_info *info;
+
+	if (tcp_authopt_needed) {
+		info = rcu_dereference_protected(tp->authopt_info,
+						 lockdep_sock_is_held((struct sock *)tp));
+		if (info)
+			__tcp_authopt_update_snd_sne(tp, info, seq);
+	}
+}
 #else
 static inline int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen)
 {
 	return -ENOPROTOOPT;
 }
@@ -230,8 +258,14 @@ static inline int tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb
 static inline int tcp_authopt_inbound_check_req(struct request_sock *sk, struct sk_buff *skb,
 						const u8 *opt)
 {
 	return 0;
 }
+static inline void tcp_authopt_update_rcv_sne(struct tcp_sock *tp, u32 seq)
+{
+}
+static inline void tcp_authopt_update_snd_sne(struct tcp_sock *tp, u32 seq)
+{
+}
 #endif
 
 #endif /* _LINUX_TCP_AUTHOPT_H */
diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
index 85de430d3326..05234923cb9f 100644
--- a/net/ipv4/tcp_authopt.c
+++ b/net/ipv4/tcp_authopt.c
@@ -631,10 +631,97 @@ static int tcp_authopt_get_isn(struct sock *sk,
 		*disn = htonl(info->dst_isn);
 	}
 	return 0;
 }
 
+/* compute_sne - Calculate Sequence Number Extension
+ *
+ * Give old upper/lower 32bit values and a new lower 32bit value determine the
+ * new value of the upper 32 bit. The new sequence number can be 2^31 before or
+ * after prev_seq but TCP window scaling should limit this further.
+ *
+ * For correct accounting the stored SNE value should be only updated together
+ * with the SEQ.
+ */
+static u32 compute_sne(u32 sne, u32 prev_seq, u32 seq)
+{
+	if (before(seq, prev_seq)) {
+		if (seq > prev_seq)
+			--sne;
+	} else {
+		if (seq < prev_seq)
+			++sne;
+	}
+
+	return sne;
+}
+
+/* Update rcv_sne, must be called immediately before rcv_nxt update */
+void __tcp_authopt_update_rcv_sne(struct tcp_sock *tp,
+				  struct tcp_authopt_info *info, u32 seq)
+{
+	info->rcv_sne = compute_sne(info->rcv_sne, tp->rcv_nxt, seq);
+}
+
+/* Update snd_sne, must be called immediately before snd_nxt update */
+void __tcp_authopt_update_snd_sne(struct tcp_sock *tp,
+				  struct tcp_authopt_info *info, u32 seq)
+{
+	info->snd_sne = compute_sne(info->snd_sne, tp->snd_nxt, seq);
+}
+
+/* Compute SNE for a specific packet (by seq). */
+static int compute_packet_sne(struct sock *sk, struct tcp_authopt_info *info,
+			      u32 seq, bool input, __be32 *sne)
+{
+	u32 rcv_nxt, snd_nxt;
+
+	// For TCP_NEW_SYN_RECV we have no tcp_authopt_info but tcp_request_sock holds ISN.
+	if (sk->sk_state == TCP_NEW_SYN_RECV) {
+		struct tcp_request_sock *rsk = tcp_rsk((struct request_sock *)sk);
+
+		if (input)
+			*sne = htonl(compute_sne(0, rsk->rcv_isn, seq));
+		else
+			*sne = htonl(compute_sne(0, rsk->snt_isn, seq));
+		return 0;
+	}
+
+	/* TCP_LISTEN only receives SYN */
+	if (sk->sk_state == TCP_LISTEN && input)
+		return 0;
+
+	/* TCP_SYN_SENT only sends SYN and receives SYN/ACK
+	 * For the input case rcv_nxt is initialized after the packet is
+	 * validated so tcp_sk(sk)->rcv_nxt is not initialized.
+	 */
+	if (sk->sk_state == TCP_SYN_SENT)
+		return 0;
+
+	if (sk->sk_state == TCP_TIME_WAIT) {
+		rcv_nxt = tcp_twsk(sk)->tw_rcv_nxt;
+		snd_nxt = tcp_twsk(sk)->tw_snd_nxt;
+	} else {
+		if (WARN_ONCE(!sk_fullsock(sk),
+			      "unexpected minisock sk=%p state=%d", sk,
+			      sk->sk_state))
+			return -EINVAL;
+		rcv_nxt = tcp_sk(sk)->rcv_nxt;
+		snd_nxt = tcp_sk(sk)->snd_nxt;
+	}
+
+	if (WARN_ONCE(!info, "unexpected missing info for sk=%p sk_state=%d", sk, sk->sk_state))
+		return -EINVAL;
+
+	if (input)
+		*sne = htonl(compute_sne(info->rcv_sne, rcv_nxt, seq));
+	else
+		*sne = htonl(compute_sne(info->snd_sne, snd_nxt, seq));
+
+	return 0;
+}
+
 /* Feed one buffer into ahash
  * The buffer is assumed to be DMA-able
  */
 static int crypto_ahash_buf(struct ahash_request *req, u8 *buf, uint len)
 {
@@ -686,10 +773,13 @@ int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct r
 	if (!new_info)
 		return -ENOMEM;
 
 	new_info->src_isn = tcp_rsk(req)->snt_isn;
 	new_info->dst_isn = tcp_rsk(req)->rcv_isn;
+	/* Caller is tcp_create_openreq_child and already initializes snd_nxt/rcv_nxt */
+	new_info->snd_sne = compute_sne(0, new_info->src_isn, tcp_sk(newsk)->snd_nxt);
+	new_info->rcv_sne = compute_sne(0, new_info->dst_isn, tcp_sk(newsk)->rcv_nxt);
 	INIT_HLIST_HEAD(&new_info->head);
 	err = tcp_authopt_clone_keys(newsk, oldsk, new_info, old_info);
 	if (err) {
 		tcp_authopt_free(newsk, new_info);
 		return err;
@@ -703,10 +793,12 @@ int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct r
 void __tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb,
 				  struct tcp_authopt_info *info)
 {
 	info->src_isn = ntohl(tcp_hdr(skb)->ack_seq) - 1;
 	info->dst_isn = ntohl(tcp_hdr(skb)->seq);
+	info->snd_sne = compute_sne(0, info->src_isn, tcp_sk(sk)->snd_nxt);
+	info->rcv_sne = compute_sne(0, info->dst_isn, tcp_sk(sk)->rcv_nxt);
 }
 
 /* feed traffic key into ahash */
 static int tcp_authopt_ahash_traffic_key(struct tcp_authopt_alg_pool *pool,
 					 struct sock *sk,
@@ -952,14 +1044,16 @@ static int tcp_authopt_hash_packet(struct tcp_authopt_alg_pool *pool,
 				   bool ipv6,
 				   bool include_options,
 				   u8 *macbuf)
 {
 	struct tcphdr *th = tcp_hdr(skb);
+	__be32 sne = 0;
 	int err;
 
-	/* NOTE: SNE unimplemented */
-	__be32 sne = 0;
+	err = compute_packet_sne(sk, info, ntohl(th->seq), input, &sne);
+	if (err)
+		return err;
 
 	err = crypto_ahash_init(pool->req);
 	if (err)
 		return err;
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4c9e403971fb..bc0a90c72391 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3517,10 +3517,11 @@ static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
 static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
 {
 	u32 delta = seq - tp->rcv_nxt;
 
 	sock_owned_by_me((struct sock *)tp);
+	tcp_authopt_update_rcv_sne(tp, seq);
 	tp->bytes_received += delta;
 	WRITE_ONCE(tp->rcv_nxt, seq);
 }
 
 /* Update our send window.
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b959e8b949b6..6a6024a0b9e9 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -67,10 +67,11 @@ static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	unsigned int prior_packets = tp->packets_out;
 
+	tcp_authopt_update_snd_sne(tp, TCP_SKB_CB(skb)->end_seq);
 	WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
 
 	__skb_unlink(skb, &sk->sk_write_queue);
 	tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
 
