[PATCH 4/7] net/tcp: Reset TCP-AO cached keys on listen() syscall

[Dmitry Safonov <dima@arista.com>]

TCP_LISTEN sockets are not connected to any peer, so having
current_key/rnext_key doesn't make sense.

The userspace may falter over this issue by setting current or rnext
TCP-AO key before listen() syscall. setsockopt(TCP_AO_DEL_KEY) doesn't
allow removing a key that is in use (in accordance to RFC 5925), so
it might be inconvenient to have keys that can be destroyed only with
listener socket.

Fixes: 4954f17ddefc ("net/tcp: Introduce TCP_AO setsockopt()s")
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 include/net/tcp_ao.h |  5 +++++
 net/ipv4/af_inet.c   |  1 +
 net/ipv4/tcp_ao.c    | 14 ++++++++++++++
 3 files changed, 20 insertions(+)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index 647781080613..e36057ca5ed8 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -270,6 +270,7 @@ int tcp_v6_ao_synack_hash(char *ao_hash, struct tcp_ao_key *ao_key,
 void tcp_ao_established(struct sock *sk);
 void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb);
 void tcp_ao_connect_init(struct sock *sk);
+void tcp_ao_listen(struct sock *sk);
 void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
 		      struct tcp_request_sock *treq,
 		      unsigned short int family, int l3index);
@@ -330,6 +331,10 @@ static inline void tcp_ao_connect_init(struct sock *sk)
 {
 }
 
+static inline void tcp_ao_listen(struct sock *sk)
+{
+}
+
 static inline int tcp_ao_get_mkts(struct sock *sk, sockptr_t optval, sockptr_t optlen)
 {
 	return -ENOPROTOOPT;
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index fb81de10d332..a08d1266344f 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -200,6 +200,7 @@ int __inet_listen_sk(struct sock *sk, int backlog)
 	 * we can only allow the backlog to be adjusted.
 	 */
 	if (old_state != TCP_LISTEN) {
+		tcp_ao_listen(sk);
 		/* Enable TFO w/o requiring TCP_FASTOPEN socket option.
 		 * Note that only TCP sockets (SOCK_STREAM) will reach here.
 		 * Also fastopen backlog may already been set via the option
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index c8be1d526eac..71c8c9c59642 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -1052,6 +1052,20 @@ static int tcp_ao_cache_traffic_keys(const struct sock *sk,
 	return ret;
 }
 
+void tcp_ao_listen(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_ao_info *ao_info;
+
+	ao_info = rcu_dereference_protected(tp->ao_info,
+					    lockdep_sock_is_held(sk));
+	if (!ao_info)
+		return;
+
+	WRITE_ONCE(ao_info->current_key, NULL);
+	WRITE_ONCE(ao_info->rnext_key, NULL);
+}
+
 void tcp_ao_connect_init(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-- 
2.42.0