---
 include/net/tcp_ao.h |  12 +++++
 net/ipv4/tcp_ao.c    | 104 ++++++++++++++++++++++++++++++++++++++++++-
 net/ipv4/tcp_ipv4.c  |  69 ++++++++++++++++++++++------
 net/ipv6/tcp_ipv6.c  |  70 ++++++++++++++++++++++-------
 4 files changed, 225 insertions(+), 30 deletions(-)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index e685ad9db949..67f997aabd9c 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h

@@ -117,12 +117,24 @@ int tcp_ao_hash_skb(unsigned short int family,
 		    const u8 *tkey, int hash_offset, u32 sne);
 int tcp_parse_ao(struct sock *sk, int cmd, unsigned short int family,
 		 sockptr_t optval, int optlen);
+struct tcp_ao_key *tcp_ao_established_key(struct tcp_ao_info *ao,
+					  int sndid, int rcvid);
 int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
 			    unsigned int len, struct tcp_sigpool *hp);
 void tcp_ao_destroy_sock(struct sock *sk);
 struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
 				    const union tcp_ao_addr *addr,
 				    int family, int sndid, int rcvid);
+int tcp_ao_hash_hdr(unsigned short family, char *ao_hash,
+		    struct tcp_ao_key *key, const u8 *tkey,
+		    const union tcp_ao_addr *daddr,
+		    const union tcp_ao_addr *saddr,
+		    const struct tcphdr *th, u32 sne);
+int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb,
+			 const struct tcp_ao_hdr *aoh, int l3index, u32 seq,
+			 struct tcp_ao_key **key, char **traffic_key,
+			 bool *allocated_traffic_key, u8 *keyid, u32 *sne);
+
 /* ipv4 specific functions */
 int tcp_v4_parse_ao(struct sock *sk, int cmd, sockptr_t optval, int optlen);
 struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,

diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c

@@ -435,6 +495,46 @@ struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
 	return tcp_ao_do_lookup(sk, addr, AF_INET, sndid, rcvid);
 }
 
+int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb,
+			 const struct tcp_ao_hdr *aoh, int l3index, u32 seq,
+			 struct tcp_ao_key **key, char **traffic_key,
+			 bool *allocated_traffic_key, u8 *keyid, u32 *sne)
+{
+	struct tcp_ao_info *ao_info;
+
+	*allocated_traffic_key = false;
+	/* If there's no socket - than initial sisn/disn are unknown.
+	 * Drop the segment. RFC5925 (7.7) advises to require graceful
+	 * restart [RFC4724]. Alternatively, the RFC5925 advises to
+	 * save/restore traffic keys before/after reboot.
+	 * Linux TCP-AO support provides TCP_AO_ADD_KEY and TCP_AO_REPAIR
+	 * options to restore a socket post-reboot.
+	 */
+	if (!sk)
+		return -ENOTCONN;
+
+	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_NEW_SYN_RECV)) {
+		return -1;
+	} else {
+		struct tcp_ao_key *rnext_key;
+
+		if (sk->sk_state == TCP_TIME_WAIT)
+			return -1;
+		ao_info = rcu_dereference(tcp_sk(sk)->ao_info);
+		if (!ao_info)
+			return -ENOENT;
+
+		*key = tcp_ao_established_key(ao_info, aoh->rnext_keyid, -1);
+		if (!*key)
+			return -ENOENT;
+		*traffic_key = snd_other_key(*key);
+		rnext_key = READ_ONCE(ao_info->rnext_key);
+		*keyid = rnext_key->rcvid;
+		*sne = 0;
+	}
+	return 0;
+}
+
 static int tcp_ao_cache_traffic_keys(const struct sock *sk,
 				     struct tcp_ao_info *ao,
 				     struct tcp_ao_key *ao_key)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 31169971cc56..f07a12f478d4 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c

@@ -657,6 +657,52 @@ void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)
 }
 EXPORT_SYMBOL(tcp_v4_send_check);
 
+#define REPLY_OPTIONS_LEN      (MAX_TCP_OPTION_SPACE / sizeof(__be32))
+
+static bool tcp_v4_ao_sign_reset(const struct sock *sk, struct sk_buff *skb,
+				 const struct tcp_ao_hdr *aoh,
+				 struct ip_reply_arg *arg, struct tcphdr *reply,
+				 __be32 reply_options[REPLY_OPTIONS_LEN])
+{
+#ifdef CONFIG_TCP_AO
+	int sdif = tcp_v4_sdif(skb);
+	int dif = inet_iif(skb);
+	int l3index = sdif ? dif : 0;
+	bool allocated_traffic_key;
+	struct tcp_ao_key *key;
+	char *traffic_key;
+	bool drop = true;
+	u32 ao_sne = 0;
+	u8 keyid;
+
+	rcu_read_lock();
+	if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, reply->seq,
+				 &key, &traffic_key, &allocated_traffic_key,
+				 &keyid, &ao_sne))

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c

@@ -1064,6 +1088,19 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
 		ack_seq = ntohl(th->seq) + th->syn + th->fin + skb->len -
 			  (th->doff << 2);
 
+#ifdef CONFIG_TCP_AO
+	if (aoh) {
+		int l3index;
+
+		l3index = tcp_v6_sdif(skb) ? tcp_v6_iif_l3_slave(skb) : 0;
+		if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, htonl(seq),