linux-kernel - Re: [PATCH net-next v24 09/23] ovpn: implement packet processing

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Message-ID: <Z-J6EmX-wZRUYt4f@krikkit>
Date: Tue, 25 Mar 2025 10:40:34 +0100
From: Sabrina Dubroca <sd@...asysnail.net>
To: Antonio Quartulli <antonio@...nvpn.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 v24 09/23] ovpn: implement packet processing

2025-03-24, 21:53:02 +0100, Antonio Quartulli wrote:
> On 24/03/2025 12:02, Sabrina Dubroca wrote:
> > 2025-03-18, 02:40:44 +0100, Antonio Quartulli wrote:
> > > +int ovpn_crypto_state_reset(struct ovpn_crypto_state *cs,
> > > +			    const struct ovpn_peer_key_reset *pkr)
> > > +{
> > > +	struct ovpn_crypto_key_slot *old = NULL, *new;
> > > +	u8 idx;
> > > +
> > > +	if (pkr->slot != OVPN_KEY_SLOT_PRIMARY &&
> > > +	    pkr->slot != OVPN_KEY_SLOT_SECONDARY)
> > > +		return -EINVAL;
> > > +
> > > +	new = ovpn_aead_crypto_key_slot_new(&pkr->key);
> > > +	if (IS_ERR(new))
> > > +		return PTR_ERR(new);
> > > +
> > > +	spin_lock_bh(&cs->lock);
> > 
> > At this point, should there be a check that we're not installing 2
> > keys with the same key_id at the same time? I expect a well-behaved
> > userspace never does that, but it would confuse
> > ovpn_crypto_key_id_to_slot if it ever happened.
> > 
> > ["well, then the tunnel is broken. if userspace sets up a broken
> > config that's not the kernel's problem." is an acceptable answer]
> > 
> 
> The behaviour of ovpn_crypto_key_id_to_slot() is still "deterministic" as we
> will first lookup the primary key.
> 
> Therefore we will simply always use the primary key and never the other,
> which is what we should expect in this situation from the code.
> 
> I'd say this is just an ill-formed configuration, yet not invalid.
> As per your statement, I'd say it's userspace's problem.

Ok, sounds good, thanks.

-- 
Sabrina