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Message-ID: <cd992750-2b8b-4793-8575-89d69ff3624c@openvpn.net>
Date: Wed, 2 Apr 2025 14:08:18 +0200
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 v24 09/23] ovpn: implement packet processing
On 01/04/2025 11:59, Sabrina Dubroca wrote:
> 2025-03-18, 02:40:44 +0100, Antonio Quartulli wrote:
>> +/* this swap is not atomic, but there will be a very short time frame where the
>> + * old_secondary key won't be available. This should not be a big deal as most
>> + * likely both peers are already using the new primary at this point.
>> + */
>
> This is not the case anymore.
Oh right - this comment can go.
>
>> +void ovpn_crypto_key_slots_swap(struct ovpn_crypto_state *cs)
>> +{
>> + const struct ovpn_crypto_key_slot *old_primary, *old_secondary;
>> + u8 idx;
>> +
>> + spin_lock_bh(&cs->lock);
>> + idx = cs->primary_idx;
>> + old_primary = rcu_dereference_protected(cs->slots[idx],
>> + lockdep_is_held(&cs->lock));
>> + old_secondary = rcu_dereference_protected(cs->slots[!idx],
>> + lockdep_is_held(&cs->lock));
>> + /* perform real swap by switching the index of the primary key */
>> + WRITE_ONCE(cs->primary_idx, !cs->primary_idx);
>> +
>> + pr_debug("key swapped: (old primary) %d <-> (new primary) %d\n",
>> + old_primary ? old_primary->key_id : -1,
>> + old_secondary ? old_secondary->key_id : -1);
>> +
>> + spin_unlock_bh(&cs->lock);
>> +}
>
> [...]
>> +int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
>> + struct sk_buff *skb)
>> +{
> [...]
>> + /* encrypt it */
>> + return crypto_aead_encrypt(req);
>> +free_iv:
>> + kfree(ovpn_skb_cb(skb)->iv);
>> + ovpn_skb_cb(skb)->iv = NULL;
>> +free_sg:
>> + kfree(ovpn_skb_cb(skb)->sg);
>> + ovpn_skb_cb(skb)->sg = NULL;
>
> nit: Those shouldn't really be needed, since we'll call
> ovpn_encrypt_post that will take care of iv/sg/req. But it's fine if
> you leave them.
Right!
This code flow was re-arranged a couple of times, and I have missed that
we now always hit those free()s in post().
I prefer to drop them and put a comment indicating that cleanup happens
in post().
>
> (same thing on the decrypt side)
Yep
>
>> + return ret;
>> +}
>
>
> [...]
>> +/**
>> + * ovpn_key_id_from_skb - extract key ID from the skb head
>> + * @skb: the packet to extract the key ID code from
>> + *
>> + * Note: this function assumes that the skb head was pulled enough
>> + * to access the first byte.
>
> nit: another "first byte" that I missed previously :(
ACK!
>
>> + *
>> + * Return: the key ID
>> + */
>> +static inline u8 ovpn_key_id_from_skb(const struct sk_buff *skb)
>> +{
>> + u32 opcode = be32_to_cpu(*(__be32 *)skb->data);
>> +
>> + return FIELD_GET(OVPN_OPCODE_KEYID_MASK, opcode);
>> +}
>
Regards,
--
Antonio Quartulli
OpenVPN Inc.
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