From: "Abhishek Chauhan (ABC)" <quic_abchauha@quicinc.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Andrew Halaney <ahalaney@redhat.com>,
"Martin KaFai Lau" <martin.lau@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>,
<kernel@quicinc.com>
Subject: Re: [RFC PATCH bpf-next v5 2/2] net: Add additional bit to support clockid_t timestamp type
Date: Tue, 30 Apr 2024 13:40:10 -0700 [thread overview]
Message-ID: <30c91655-a1ba-44da-900b-f2a70ed9f961@quicinc.com> (raw)
In-Reply-To: <663153f92a297_33210f29423@willemb.c.googlers.com.notmuch>
On 4/30/2024 1:26 PM, Willem de Bruijn wrote:
> Abhishek Chauhan (ABC) wrote:
>>
>>
>> On 4/26/2024 4:50 PM, Martin KaFai Lau wrote:
>>> On 4/26/24 11:46 AM, Abhishek Chauhan (ABC) wrote:
>>>>>> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
>>>>>> index 591226dcde26..f195b31d6e75 100644
>>>>>> --- a/net/ipv4/ip_output.c
>>>>>> +++ b/net/ipv4/ip_output.c
>>>>>> @@ -1457,7 +1457,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
>>>>>> skb->priority = (cork->tos != -1) ? cork->priority: READ_ONCE(sk->sk_priority);
>>>>>> skb->mark = cork->mark;
>>>>>> - skb->tstamp = cork->transmit_time;
>>>>>> + skb_set_tstamp_type_frm_clkid(skb, cork->transmit_time, sk->sk_clockid);
>>>>> hmm... I think this will break for tcp. This sequence in particular:
>
> Good catch, thanks!
>
>>>>>
>>>>> tcp_v4_timewait_ack()
>>>>> tcp_v4_send_ack()
>>>>> ip_send_unicast_reply()
>>>>> ip_push_pending_frames()
>>>>> ip_finish_skb()
>>>>> __ip_make_skb()
>>>>> /* sk_clockid is REAL but cork->transmit_time should be in mono */
>>>>> skb_set_tstamp_type_frm_clkid(skb, cork->transmit_time, sk->sk_clockid);;
>>>>>
>>>>> I think I hit it from time to time when running the test in this patch set.
>>>>>
>>>> do you think i need to check for protocol type here . since tcp uses Mono and the rest according to the new design is based on
>>>> sk->sk_clockid
>>>> if (iph->protocol == IPPROTO_TCP)
>>>> skb_set_tstamp_type_frm_clkid(skb, cork->transmit_time, CLOCK_MONOTONIC);
>>>> else
>>>> skb_set_tstamp_type_frm_clkid(skb, cork->transmit_time, sk->sk_clockid);
>>>
>>> Looks ok. iph->protocol is from sk->sk_protocol. I would defer to Willem input here.
>>>
>>> There is at least one more place that needs this protocol check, __ip6_make_skb().
>>
>> Sounds good. I will wait for Willem to comment here.
>
> This would be sk_is_tcp(sk).
>
> I think we want to avoid special casing if we can. Note the if.
>
> If TCP always uses monotonic, we could consider initializing
> sk_clockid to CLOCK_MONONOTIC in tcp_init_sock.
>
> I guess TCP logic currently entirely ignores sk_clockid. If we are to
> start using this, then setsocktop SO_TXTIME must explicitly fail or
> ignore for TCP sockets, or silently skip the write.
>
> All of that is more complexity. Than is maybe warranted for this one
> case. So no objections from me to special casing using sk_is_tcp(sk)
> either.
>
>
Thanks Willem and Martin for all the support and reviews.
I will take care of this in the next RFC patch
- adding the sk_is_tcp check and setting tstamp_type to mono for tcp
>
>
next prev parent reply other threads:[~2024-04-30 20:40 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-24 22:20 [RFC PATCH bpf-next v5 0/2] Replace mono_delivery_time with tstamp_type Abhishek Chauhan
2024-04-24 22:20 ` [RFC PATCH bpf-next v5 1/2] net: Rename mono_delivery_time to tstamp_type for scalabilty Abhishek Chauhan
2024-04-25 14:31 ` Willem de Bruijn
2024-04-25 19:02 ` Abhishek Chauhan (ABC)
2024-04-25 23:50 ` Martin KaFai Lau
2024-04-25 23:55 ` Abhishek Chauhan (ABC)
2024-04-24 22:20 ` [RFC PATCH bpf-next v5 2/2] net: Add additional bit to support clockid_t timestamp type Abhishek Chauhan
2024-04-25 14:42 ` Willem de Bruijn
2024-04-25 19:12 ` Abhishek Chauhan (ABC)
2024-04-26 4:37 ` Martin KaFai Lau
2024-04-26 18:46 ` Abhishek Chauhan (ABC)
2024-04-26 23:50 ` Martin KaFai Lau
2024-04-30 19:16 ` Abhishek Chauhan (ABC)
2024-04-30 20:26 ` Willem de Bruijn
2024-04-30 20:40 ` Abhishek Chauhan (ABC) [this message]
2024-05-03 21:33 ` Abhishek Chauhan (ABC)
2024-05-03 21:41 ` Martin KaFai Lau
2024-05-03 22:14 ` Abhishek Chauhan (ABC)
2024-04-26 23:55 ` Martin KaFai Lau
2024-04-30 19:59 ` Abhishek Chauhan (ABC)
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