[PATCH v4 4/7] net/tcp: Allow removing current/rnext TCP-AO keys on TCP_LISTEN sockets

[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>
---
 net/ipv4/tcp_ao.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index c8be1d526eac..bf41be6d4721 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -1818,8 +1818,16 @@ static int tcp_ao_del_cmd(struct sock *sk, unsigned short int family,
 		if (!new_rnext)
 			return -ENOENT;
 	}
-	if (cmd.del_async && sk->sk_state != TCP_LISTEN)
-		return -EINVAL;
+	if (sk->sk_state == TCP_LISTEN) {
+		/* Cleaning up possible "stale" current/rnext keys state,
+		 * that may have preserved from TCP_CLOSE, before sys_listen()
+		 */
+		ao_info->current_key = NULL;
+		ao_info->rnext_key = NULL;
+	} else {
+		if (cmd.del_async)
+			return -EINVAL;
+	}
 
 	if (family == AF_INET) {
 		struct sockaddr_in *sin = (struct sockaddr_in *)&cmd.addr;
-- 
2.43.0