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

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Message-ID: <78e59cd0-332e-4a97-8060-ccdf023e8a91@openvpn.net>
Date: Mon, 3 Feb 2025 14:12:52 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: Sabrina Dubroca <sd@...asysnail.net>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Donald Hunter <donald.hunter@...il.com>, Shuah Khan <shuah@...nel.org>,
 ryazanov.s.a@...il.com, Andrew Lunn <andrew+netdev@...n.ch>,
 Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Xiao Liang <shaw.leon@...il.com>
Subject: Re: [PATCH net-next v18 12/25] ovpn: implement TCP transport

On 03/02/2025 11:05, Sabrina Dubroca wrote:
> 2025-01-13, 10:31:31 +0100, Antonio Quartulli wrote:
>> +static void ovpn_tcp_rcv(struct strparser *strp, struct sk_buff *skb)
>> +{
> [...]
>> +	/* we need the first byte of data to be accessible
>> +	 * to extract the opcode and the key ID later on
>> +	 */
>> +	if (!pskb_may_pull(skb, 1)) {
> 
> make sure we have 1B...
> 
>> +		net_warn_ratelimited("%s: packet too small to fetch opcode for peer %u\n",
>> +				     netdev_name(peer->ovpn->dev), peer->id);
>> +		goto err;
>> +	}
>> +
>> +	/* DATA_V2 packets are handled in kernel, the rest goes to user space */
>> +	opcode = ovpn_opcode_from_skb(skb, 0);
> 
> but this reads a u32 (4B) from skb->data

ACK, hand-in-hand with the comment not updated.
Will fix this.

> 
> [...]
>> +void ovpn_tcp_socket_detach(struct ovpn_socket *ovpn_sock)
>> +{
>> +	struct ovpn_peer *peer = ovpn_sock->peer;
>> +	struct socket *sock = ovpn_sock->sock;
>> +
>> +	strp_stop(&peer->tcp.strp);
>> +
>> +	skb_queue_purge(&peer->tcp.user_queue);
>>
>> +	/* restore CBs that were saved in ovpn_sock_set_tcp_cb() */
>> +	sock->sk->sk_data_ready = peer->tcp.sk_cb.sk_data_ready;
>> +	sock->sk->sk_write_space = peer->tcp.sk_cb.sk_write_space;
>> +	sock->sk->sk_prot = peer->tcp.sk_cb.prot;
>> +	sock->sk->sk_socket->ops = peer->tcp.sk_cb.ops;
>> +
>> +	/* drop reference to peer */
> 
> nit: not really :)

drop comment :)

> 
>> +	rcu_assign_sk_user_data(sock->sk, NULL);
>> +
>> +	/* before canceling any ongoing work we must ensure that CBs
>> +	 * have been reset to prevent workers from being re-armed
>> +	 */
>> +	barrier();
>> +
>> +	cancel_work_sync(&peer->tcp.tx_work);
>> +	strp_done(&peer->tcp.strp);
>> +	skb_queue_purge(&peer->tcp.out_queue);
> 
> Also kfree_skb(peer->tcp.out_msg.skb)?

hm yeah, it could be we allocated one but did not finish filling it.

> 
>> +	ovpn_peer_put(peer);
>> +}
> 
> 
> [...]
>> +static int ovpn_tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
>> +{
> [...]
>> +	ret = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
>> +	if (ret) {
>> +		kfree_skb(skb);
>> +		net_err_ratelimited("%s: skb copy from iter failed: %d\n",
>> +				    netdev_name(sock->peer->ovpn->dev), ret);
>> +		goto peer_free;
>> +	}
>> +
>> +	ovpn_tcp_send_sock_skb(sock->peer, skb);
> 
> This isn't propagating MSG_DONTWAIT down to ovpn_tcp_send_sock?
> 

patch 14/25 will add a new member to ovpn_cb which will be filled right 
before calling ovpn_tcp_send_sock_skb() and that gets picked later.

Cheers,


-- 
Antonio Quartulli
OpenVPN Inc.