From: Mat Martineau <mathew.j.martineau@linux.intel.com>
To: Paolo Abeni <pabeni@redhat.com>
Cc: Jianguo Wu <wujianguo106@163.com>, mptcp@lists.linux.dev, fw@strlen.de
Subject: Re: [PATCH v5 4/4] mptcp: avoid processing packet if a subflow reset
Date: Thu, 24 Jun 2021 15:38:40 -0700 (PDT) [thread overview]
Message-ID: <88512964-7469-83e0-99e6-a9311ed0f770@linux.intel.com> (raw)
In-Reply-To: <7c26d28d7249536615bf945b09d683f81eb06be0.camel@redhat.com>
On Thu, 24 Jun 2021, Paolo Abeni wrote:
> On Thu, 2021-06-24 at 09:57 +0800, Jianguo Wu wrote:
>>
>> On 2021/6/23 17:48, Paolo Abeni wrote:
>>> On Tue, 2021-06-22 at 17:00 -0700, Mat Martineau wrote:
>>>> On Mon, 21 Jun 2021, Jianguo Wu wrote:
>>>>
>>>>> Hi Mat,
>>>>>
>>>>> On 2021/6/19 8:19, Mat Martineau wrote:
>>>>>> On Wed, 16 Jun 2021, wujianguo106@163.com wrote:
>>>>>>
>>>>>>> From: Jianguo Wu <wujianguo@chinatelecom.cn>
>>>>>>>
>>>>>>> If check_fully_established() causes a subflow reset, it should not
>>>>>>> continue to process the packet in tcp_data_queue().
>>>>>>>
>>>>>>> setting:
>>>>>>> TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
>>>>>>>
>>>>>>> so that the following check will drop the pkt in
>>>>>>> tcp_data_queue():
>>>>>>> if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
>>>>>>> __kfree_skb(skb);
>>>>>>> return;
>>>>>>> }
>>>>>>>
>>>>>>> Fixes: d582484726c4 ("mptcp: fix fallback for MP_JOIN subflows")
>>>>>>> Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
>>>>>>> ---
>>>>>>> net/mptcp/options.c | 6 ++++++
>>>>>>> 1 file changed, 6 insertions(+)
>>>>>>>
>>>>>>> diff --git a/net/mptcp/options.c b/net/mptcp/options.c
>>>>>>> index 1aec01686c1a..be435c5421cd 100644
>>>>>>> --- a/net/mptcp/options.c
>>>>>>> +++ b/net/mptcp/options.c
>>>>>>> @@ -926,6 +926,12 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
>>>>>>> return true;
>>>>>>>
>>>>>>> reset:
>>>>>>> + /* If a subflow is reset, the packet should not continue to be
>>>>>>> + * processed in tcp_data_queue(), so setting: end_seq = seq,
>>>>>>> + * then tcp_data_queue() will drop the packet.
>>>>>>> + */
>>>>>>> + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
>>>>>>> +
>>>>>>
>>>>>> This does have the desired effect when mptcp_incoming_options() is
>>>>>> called from tcp_data_queue(), but mptcp_incoming_options() is also
>>>>>> called from tcp_reset() and tcp_rcv_state_process(). The other callers
>>>>>> appear to tolerate the sequence number modification.
>>>>>>
>>>>>> I think it would be clearer to either add a return value or output
>>>>>> parameter to mptcp_incoming_options() to explicitly tell the caller
>>>>>> that a reset has been sent and tcp_done() called. Then it would be
>>>>>> clearer in tcp_data_queue() that the packet is being discarded due to
>>>>>> mptcp header content.
>>>>>>
>>>>>
>>>>> If a reset has been sent and tcp_done() called in
>>>>> check_fully_established(), the sk_state will be TCP_CLOSE, how about
>>>>> just do (sk_state == TCP_CLOSE) check in tcp_data_queue() as it did in
>>>>> the V1 of this patch?
>>>>
>>>> Oh, I see now that Paolo suggested the the end_seq assignment in order to
>>>> only modify MPTCP code.
>>>>
>>>> I still think it's better to make it clear that we're discarding a packet
>>>> due to the mptcp headers - using the existing sequence check (intended to
>>>> detect acks) in tcp_data_queue() seems sneaky to me.
>>>>
>>>> Something like
>>>>
>>>> if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb)) {
>>>> __kfree_skb(skb);
>>>> return;
>>>> }
>>>>
>>>> seems both compact and clear. Does that seem ok Paolo?
>>>
>>> Uhmmm... we need to touch every mptcp_incoming_options() call site, and
>>> in tcp_reset() the above chunk looks a bit strange to me. Probably we
>>> could just ignore the mptcp_incoming_options() return value there.
>>>
>>> Otherwise no big objections - not sure about upstream ;)
>>>
>>
>> Hi Mat and Paolo,
>>
>> If you both agree, I will send a new version that mptcp_incoming_options() add a return value, and only check return value in tcp_data_queue(),
>> ignore the return value in other call site.
>
> Even the hook in tcp_rcv_state_process() can be followed by
> tcp_data_queue().
>
> I *think* it's better ignoring the return value of
> mptcp_incoming_options() only in tcp_reset(), adding there a comment -
> something alike "mptcp can't tell us to ignore reset pkts".
>
This sounds like a good approach, thanks.
--
Mat Martineau
Intel
next prev parent reply other threads:[~2021-06-24 22:38 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-16 10:49 [PATCH v5 0/4] Fix some mptcp syncookie process bugs wujianguo106
2021-06-16 10:49 ` [PATCH v5 1/4] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join wujianguo106
2021-06-18 22:40 ` Mat Martineau
2021-06-21 6:14 ` Jianguo Wu
2021-06-21 10:09 ` Jianguo Wu
2021-06-22 23:38 ` Mat Martineau
2021-06-16 10:49 ` [PATCH v5 2/4] mptcp: remove redundant req destruct in subflow_check_req() wujianguo106
2021-06-16 10:49 ` [PATCH v5 3/4] mptcp: fix syncookie process if mptcp can not_accept new subflow wujianguo106
2021-06-18 23:19 ` Mat Martineau
2021-06-21 6:24 ` Jianguo Wu
2021-06-24 2:08 ` Jianguo Wu
2021-06-24 22:36 ` Mat Martineau
2021-06-16 10:49 ` [PATCH v5 4/4] mptcp: avoid processing packet if a subflow reset wujianguo106
2021-06-19 0:19 ` Mat Martineau
2021-06-21 6:35 ` Jianguo Wu
2021-06-23 0:00 ` Mat Martineau
2021-06-23 9:48 ` Paolo Abeni
2021-06-24 1:57 ` Jianguo Wu
2021-06-24 10:02 ` Paolo Abeni
2021-06-24 22:38 ` Mat Martineau [this message]
2021-06-25 0:51 ` Jianguo Wu
2021-06-19 0:26 ` [PATCH v5 0/4] Fix some mptcp syncookie process bugs Mat Martineau
2021-06-21 6:39 ` Jianguo Wu
2021-06-23 0:07 ` Mat Martineau
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