Re: [PATCH net-next v18 12/25] ovpn: implement TCP transport

Antonio Quartulli
2025-01-20T14:11:33Z

On 17/01/2025 18:14, Sabrina Dubroca wrote:
> 2025-01-13, 10:31:31 +0100, Antonio Quartulli wrote:
>> +static int ovpn_tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
>> + int flags, int *addr_len)
>> +{
>> + int err = 0, off, copied = 0, ret;
>> + struct ovpn_socket *sock;
>> + struct ovpn_peer *peer;
>> + struct sk_buff *skb;
>> +
>> + rcu_read_lock();
>> + sock = rcu_dereference_sk_user_data(sk);
>> + if (!sock || !sock->peer) {
>> + rcu_read_unlock();
>> + return -EBADF;
>> + }
>> + /* we take a reference to the peer linked to this TCP socket, because
>> + * in turn the peer holds a reference to the socket itself.

Going back now to this specific comment:

>
> Not anymore since v12? [*]
>
> I think it's ok here because we're only using peer and sk (not
> anything from ovpn_socket), but it is relevant in _sendmsg, which has
> the same peer_hold pattern without this comment.

After applying to _sendmsg() the modifications you suggested (i.e.
reference peer directly instead of sock->peer), it also only uses peer
and sk, but not ovpn_socket.
Therefore it should be fine too.

This said, the comment above should go away or at least should be modified.

>
> [*]
> v11:
> - https://lore.kernel.org/netdev/20241029-b4-ovpn-v11-8-de4698c73a25@openvpn.net/
> ovpn_peer_release -> ovpn_socket_put
>
> v12:
> - https://lore.kernel.org/netdev/20241202-b4-ovpn-v12-9-239ff733bf97@openvpn.net/
> ovpn_peer_release doesn't do ovpn_socket_put
>
> - https://lore.kernel.org/netdev/20241202-b4-ovpn-v12-7-239ff733bf97@openvpn.net/
> ovpn_socket_put is done directly at ovpn_peer_remove time, before the final peer_put

Right - the lifetime of ovpn_socket is not tied to ovpn_peer anymore.
However, with the current code I don't think we ever assume that.

Regards,

--
Antonio Quartulli
OpenVPN Inc.