Re: [PATCH net-next v18 17/25] ovpn: implement keepalive mechanism

[Antonio Quartulli <antonio@openvpn.net>]

On 03/02/2025 10:20, Sabrina Dubroca wrote:
> 2025-01-13, 10:31:36 +0100, Antonio Quartulli wrote:
>> +void ovpn_xmit_special(struct ovpn_peer *peer, const void *data,
>> +		       const unsigned int len)
>> +{
>> +	struct ovpn_priv *ovpn;
>> +	struct sk_buff *skb;
>> +
>> +	ovpn = peer->ovpn;
>> +	if (unlikely(!ovpn))
>> +		return;
>> +
>> +	skb = alloc_skb(256 + len, GFP_ATOMIC);
>> +	if (unlikely(!skb))
>> +		return;
>> +
>> +	skb_reserve(skb, 128);
>> +	skb->priority = TC_PRIO_BESTEFFORT;
>> +	__skb_put_data(skb, data, len);
>> +
>> +	/* increase reference counter when passing peer to sending queue */
>> +	if (!ovpn_peer_hold(peer)) {
>> +		netdev_dbg(ovpn->dev,
>> +			   "cannot hold peer reference for sending special packet\n");
>> +		kfree_skb(skb);
>> +		return;
>> +	}
>> +
>> +	ovpn_send(ovpn, skb, peer);
>> +}
> 
> [...]
>> +static void ovpn_peer_keepalive_send(struct work_struct *work)
>> +{
>> +	struct ovpn_peer *peer = container_of(work, struct ovpn_peer,
>> +					      keepalive_work);
>> +
>> +	local_bh_disable();
>> +	ovpn_xmit_special(peer, ovpn_keepalive_message,
>> +			  sizeof(ovpn_keepalive_message));
>> +	local_bh_enable();
>> +	ovpn_peer_put(peer);
> 
> nit: could we simply drop this put and the hold in ovpn_xmit_special?
> ovpn_peer_keepalive_send has a reference on the peer from the WQ, just
> transfer it to ovpn_xmit_special and then ovpn_send. No need to
> pretend to acquire one for ovpn_send's sake and drop the one we got
> from the WQ? (ovpn_xmit_special would need to _put(peer) in case of
> early return)

Ok, will drop both and add a comment to remember the casual reader that 
we already hold a reference (+ put() in error path).

Regards,

> 
>> +}
> 

-- 
Antonio Quartulli
OpenVPN Inc.