Re: [PATCH net-next v24 07/23] ovpn: implement basic TX path (UDP)

[Antonio Quartulli]

On 01/04/2025 15:49, Sabrina Dubroca wrote:
> 2025-03-18, 02:40:42 +0100, Antonio Quartulli wrote:
> > +static int ovpn_udp_output(struct ovpn_peer *peer, struct dst_cache *cache,
> > +			   struct sock *sk, struct sk_buff *skb)
> > +{
> > +	struct ovpn_bind *bind;
> > +	int ret;
> > +
> > +	/* set sk to null if skb is already orphaned */
> > +	if (!skb->destructor)
> > +		skb->sk = NULL;
> > +
> > +	/* always permit openvpn-created packets to be (outside) fragmented */
> > +	skb->ignore_df = 1;
>
> Have you tested this with IPv4 encap? AFAICT it doesn't have any
> effect because of the call chain:
>
> ovpn_udp4_output -> udp_tunnel_xmit_skb -> iptunnel_xmit -> skb_scrub_packet
>
> which does
>
>      skb->ignore_df = 0;
>
>
> But since you pass df = 0 to udp_tunnel_xmit_skb, I suspect it works
> as intended despite skb_scrub_packet.

Yeah, seems so. Passing df = 0 basically does what we need.
So you're right, that ignore_df = 1 is useless.
Will drop it.

> [note: that was the last comment I wanted to send, I have a few more
> suggestions that don't need to be addressed at this time]

Thanks! :-)
I'll answer all other open comments in the meantime..

Regards,

> > +
> > +	rcu_read_lock();
> > +	bind = rcu_dereference(peer->bind);
> > +	if (unlikely(!bind)) {
> > +		net_warn_ratelimited("%s: no bind for remote peer %u\n",
> > +				     netdev_name(peer->ovpn->dev), peer->id);
> > +		ret = -ENODEV;
> > +		goto out;
> > +	}
> > +
> > +	switch (bind->remote.in4.sin_family) {
> > +	case AF_INET:
> > +		ret = ovpn_udp4_output(peer, bind, cache, sk, skb);
> > +		break;
> > +#if IS_ENABLED(CONFIG_IPV6)
> > +	case AF_INET6:
> > +		ret = ovpn_udp6_output(peer, bind, cache, sk, skb);
> > +		break;
> > +#endif
> > +	default:
> > +		ret = -EAFNOSUPPORT;
> > +		break;
> > +	}
> > +
> > +out:
> > +	rcu_read_unlock();
> > +	return ret;
> > +}

--
Antonio Quartulli
OpenVPN Inc.