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Message-ID: <6eb5b283-a9bd-4081-8bce-a60d72af430c@quicinc.com>
Date: Tue, 30 Apr 2024 12:16:35 -0700
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Subject: Re: [RFC PATCH bpf-next v5 2/2] net: Add additional bit to support
 clockid_t timestamp type
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To: Martin KaFai Lau <martin.lau@linux.dev>,
        Willem de Bruijn
	<willemdebruijn.kernel@gmail.com>
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>
References: <20240424222028.1080134-1-quic_abchauha@quicinc.com>
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 <2b2c3eb1-df87-40fe-b871-b52812c8ecd0@linux.dev>
 <e761e1de-0e11-4541-a4db-a1b793a60674@quicinc.com>
 <379558fe-a6e2-444b-a6a7-ef233efa8311@linux.dev>
From: "Abhishek Chauhan (ABC)" <quic_abchauha@quicinc.com>
In-Reply-To: <379558fe-a6e2-444b-a6a7-ef233efa8311@linux.dev>
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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:
>>>
>>> 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.