[PATCH v3 19/36] net/tcp: Add TCP-AO SNE support

[Dmitry Safonov <dima@arista.com>]

Add Sequence Number Extension (SNE) extension for TCP-AO.
This is needed to protect long-living TCP-AO connections from replaying
attacks after sequence number roll-over, see RFC5925 (6.2).

Co-developed-by: Francesco Ruggeri <fruggeri@arista.com>
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Co-developed-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 net/ipv4/tcp_input.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index df3087c8179f..2ba46d5db421 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3528,9 +3528,21 @@ static inline bool tcp_may_update_window(const struct tcp_sock *tp,
 static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
 {
 	u32 delta = ack - tp->snd_una;
+#ifdef CONFIG_TCP_AO
+	struct tcp_ao_info *ao;
+#endif
 
 	sock_owned_by_me((struct sock *)tp);
 	tp->bytes_acked += delta;
+#ifdef CONFIG_TCP_AO
+	ao = rcu_dereference_protected(tp->ao_info,
+				       lockdep_sock_is_held((struct sock *)tp));
+	if (ao) {
+		if (ack < ao->snd_sne_seq)
+			ao->snd_sne++;
+		ao->snd_sne_seq = ack;
+	}
+#endif
 	tp->snd_una = ack;
 }
 
@@ -3538,9 +3550,21 @@ 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;
+#ifdef CONFIG_TCP_AO
+	struct tcp_ao_info *ao;
+#endif
 
 	sock_owned_by_me((struct sock *)tp);
 	tp->bytes_received += delta;
+#ifdef CONFIG_TCP_AO
+	ao = rcu_dereference_protected(tp->ao_info,
+				       lockdep_sock_is_held((struct sock *)tp));
+	if (ao) {
+		if (seq < ao->rcv_sne_seq)
+			ao->rcv_sne++;
+		ao->rcv_sne_seq = seq;
+	}
+#endif
 	WRITE_ONCE(tp->rcv_nxt, seq);
 }
 
@@ -6357,6 +6381,17 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 		 * simultaneous connect with crossed SYNs.
 		 * Particularly, it can be connect to self.
 		 */
+#ifdef CONFIG_TCP_AO
+		struct tcp_ao_info *ao;
+
+		ao = rcu_dereference_protected(tp->ao_info,
+					       lockdep_sock_is_held(sk));
+		if (ao) {
+			ao->risn = th->seq;
+			ao->rcv_sne = 0;
+			ao->rcv_sne_seq = ntohl(th->seq);
+		}
+#endif
 		tcp_set_state(sk, TCP_SYN_RECV);
 
 		if (tp->rx_opt.saw_tstamp) {
-- 
2.38.1