linux-kernel - Re: [PATCH net-next v11 09/23] ovpn: implement basic RX path (UDP)

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Message-ID: <3aa1644e-ddca-44ef-aa7c-da1382083f77@openvpn.net>
Date: Thu, 31 Oct 2024 14:04:33 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: Sabrina Dubroca <sd@...asysnail.net>
Cc: 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@...n.ch>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v11 09/23] ovpn: implement basic RX path (UDP)

On 31/10/2024 12:29, Sabrina Dubroca wrote:
> 2024-10-29, 11:47:22 +0100, Antonio Quartulli wrote:
>> +static int ovpn_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
>> +{
> [...]
>> +	opcode = ovpn_opcode_from_skb(skb, sizeof(struct udphdr));
>> +	if (unlikely(opcode != OVPN_DATA_V2)) {
>> +		/* DATA_V1 is not supported */
>> +		if (opcode == OVPN_DATA_V1)
> 
> The TCP encap code passes everything that's not V2 to userspace. Why
> not do that with UDP as well?

If that's the case, then this is a bug in the TCP code.

DATA_Vx packets are part of the data channel and userspace can't do 
anything with them (userspace handles the control channel only when the 
ovpn module is in use).

I'll go check the TCP code then, because sending DATA_V1 to userspace is 
not expected. Thanks for noticing this discrepancy.

> 
>> +			goto drop;
>> +
>> +		/* unknown or control packet: let it bubble up to userspace */
>> +		return 1;
>> +	}
>> +
>> +	peer_id = ovpn_peer_id_from_skb(skb, sizeof(struct udphdr));
>> +	/* some OpenVPN server implementations send data packets with the
>> +	 * peer-id set to undef. In this case we skip the peer lookup by peer-id
>> +	 * and we try with the transport address
>> +	 */
>> +	if (peer_id != OVPN_PEER_ID_UNDEF) {
>> +		peer = ovpn_peer_get_by_id(ovpn, peer_id);
>> +		if (!peer) {
>> +			net_err_ratelimited("%s: received data from unknown peer (id: %d)\n",
>> +					    __func__, peer_id);
>> +			goto drop;
>> +		}
>> +	}
>> +
>> +	if (!peer) {
> 
> nit: that could be an "else" combined with the previous case?

mhh that's true. Then I can combine the two "if (!peer)" in one block only.


Thanks!
Regards,

> 
>> +		/* data packet with undef peer-id */
>> +		peer = ovpn_peer_get_by_transp_addr(ovpn, skb);
>> +		if (unlikely(!peer)) {
>> +			net_dbg_ratelimited("%s: received data with undef peer-id from unknown source\n",
>> +					    __func__);
>> +			goto drop;
>> +		}
>> +	}
> 

-- 
Antonio Quartulli
OpenVPN Inc.