Re: [RFC PATCH bpf-next v4 1/2] net: Rename mono_delivery_time to tstamp_type for scalabilty

From: Abhishek Chauhan (ABC)
Date: Thu Apr 18 2024 - 16:00:05 EST




On 4/18/2024 11:47 AM, Willem de Bruijn wrote:
> Abhishek Chauhan wrote:
>> mono_delivery_time was added to check if skb->tstamp has delivery
>> time in mono clock base (i.e. EDT) otherwise skb->tstamp has
>> timestamp in ingress and delivery_time at egress.
>>
>> Renaming the bitfield from mono_delivery_time to tstamp_type is for
>> extensibilty for other timestamps such as userspace timestamp
>> (i.e. SO_TXTIME) set via sock opts.
>>
>> As we are renaming the mono_delivery_time to tstamp_type, it makes
>> sense to start assigning tstamp_type based on enum defined
>> in this commit.
>>
>> Earlier we used bool arg flag to check if the tstamp is mono in
>> function skb_set_delivery_time, Now the signature of the functions
>> accepts tstamp_type to distinguish between mono and real time.
>>
>> In future tstamp_type:1 can be extended to support userspace timestamp
>> by increasing the bitfield.
>>
>> Link: https://lore.kernel.org/netdev/bc037db4-58bb-4861-ac31-a361a93841d3@xxxxxxxxx/
>> Signed-off-by: Abhishek Chauhan <quic_abchauha@xxxxxxxxxxx>
>
>> +/**
>> + * tstamp_type:1 can take 2 values each
>> + * represented by time base in skb
>> + * 0x0 => real timestamp_type
>> + * 0x1 => mono timestamp_type
>> + */
>> +enum skb_tstamp_type {
>> + SKB_CLOCK_REAL, /* Time base is skb is REALTIME */
>> + SKB_CLOCK_MONO, /* Time base is skb is MONOTONIC */
>> +};
>> +
>
> Can drop the comments. These names are self documenting.

Noted! . I will take care of this
>
>> /**
>> * DOC: Basic sk_buff geometry
>> *
>> @@ -819,7 +830,7 @@ typedef unsigned char *sk_buff_data_t;
>> * @dst_pending_confirm: need to confirm neighbour
>> * @decrypted: Decrypted SKB
>> * @slow_gro: state present at GRO time, slower prepare step required
>> - * @mono_delivery_time: When set, skb->tstamp has the
>> + * @tstamp_type: When set, skb->tstamp has the
>> * delivery_time in mono clock base (i.e. EDT). Otherwise, the
>> * skb->tstamp has the (rcv) timestamp at ingress and
>> * delivery_time at egress.
>
> Is this still correct? I think all egress does now annotate correctly
> as SKB_CLOCK_MONO. So when not set it always is SKB_CLOCK_REAL.
>
That is correct.

>> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
>> index 61119d42b0fd..a062f88c47c3 100644
>> --- a/net/ipv4/tcp_output.c
>> +++ b/net/ipv4/tcp_output.c
>> @@ -1300,7 +1300,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
>> tp = tcp_sk(sk);
>> prior_wstamp = tp->tcp_wstamp_ns;
>> tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
>> - skb_set_delivery_time(skb, tp->tcp_wstamp_ns, true);
>> + skb_set_delivery_time(skb, tp->tcp_wstamp_ns, CLOCK_MONOTONIC);
>
> Multiple references to CLOCK_MONOTONIC left
>
I think i took care of all the references. Apologies if i didn't understand your comment here.


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