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Date: Mon, 6 May 2024 12:55:57 -0700
From: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
"David S. Miller"
<davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
<kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, Andrew Halaney <ahalaney@...hat.com>,
"Martin
KaFai Lau" <martin.lau@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Daniel Borkmann <daniel@...earbox.net>, bpf <bpf@...r.kernel.org>
CC: <kernel@...cinc.com>
Subject: Re: [RFC PATCH bpf-next v6 1/3] net: Rename mono_delivery_time to
tstamp_type for scalabilty
On 5/6/2024 11:51 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.
>>
>> Also skb_set_delivery_type_by_clockid is a new function which accepts
>> clockid to determine the tstamp_type.
>>
>> 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@linux.dev/
>> Signed-off-by: Abhishek Chauhan <quic_abchauha@...cinc.com>
>> ---
>> Changes since v5
>> - Avoided using garble function names as mentioned by
>> Willem.
>> - Implemented a conversion function stead of duplicating
>> the same logic as mentioned by Willem.
>> - Fixed indentation problems and minor documentation issues
>> which mentions tstamp_type as a whole instead of bitfield
>> notations. (Mentioned both by Willem and Martin)
>>
>> Changes since v4
>> - Introduce new function to directly delivery_time and
>> another to set tstamp_type based on clockid.
>> - Removed un-necessary comments in skbuff.h as
>> enums were obvious and understood.
>>
>> Changes since v3
>> - Fixed inconsistent capitalization in skbuff.h
>> - remove reference to MONO_DELIVERY_TIME_MASK in skbuff.h
>> and point it to skb_tstamp_type now.
>> - Explicitely setting SKB_CLOCK_MONO if valid transmit_time
>> ip_send_unicast_reply
>> - Keeping skb_tstamp inline with skb_clear_tstamp.
>> - skb_set_delivery_time checks if timstamp is 0 and
>> sets the tstamp_type to SKB_CLOCK_REAL.
>> - Above comments are given by Willem
>> - Found out that skbuff.h has access to uapi/linux/time.h
>> So now instead of using CLOCK_REAL/CLOCK_MONO
>> i am checking actual clockid_t directly to set tstamp_type
>> example:- CLOCK_REALTIME/CLOCK_MONOTONIC
>> - Compilation error fixed in
>> net/ieee802154/6lowpan/reassembly.c
>>
>> Changes since v2
>> - Minor changes to commit subject
>>
>> Changes since v1
>> - Squashed the two commits into one as mentioned by Willem.
>> - Introduced switch in skb_set_delivery_time.
>> - Renamed and removed directionality aspects w.r.t tstamp_type
>> as mentioned by Willem.
>>
>> include/linux/skbuff.h | 53 ++++++++++++++++------
>> include/net/inet_frag.h | 4 +-
>> net/bridge/netfilter/nf_conntrack_bridge.c | 6 +--
>> net/core/dev.c | 2 +-
>> net/core/filter.c | 10 ++--
>> net/ieee802154/6lowpan/reassembly.c | 2 +-
>> net/ipv4/inet_fragment.c | 2 +-
>> net/ipv4/ip_fragment.c | 2 +-
>> net/ipv4/ip_output.c | 9 ++--
>> net/ipv4/tcp_output.c | 16 +++----
>> net/ipv6/ip6_output.c | 6 +--
>> net/ipv6/netfilter.c | 6 +--
>> net/ipv6/netfilter/nf_conntrack_reasm.c | 2 +-
>> net/ipv6/reassembly.c | 2 +-
>> net/ipv6/tcp_ipv6.c | 2 +-
>> net/sched/act_bpf.c | 4 +-
>> net/sched/cls_bpf.c | 4 +-
>> 17 files changed, 80 insertions(+), 52 deletions(-)
>>
>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>> index 1c2902eaebd3..de3915e2bfdb 100644
>> --- a/include/linux/skbuff.h
>> +++ b/include/linux/skbuff.h
>> @@ -706,6 +706,11 @@ typedef unsigned int sk_buff_data_t;
>> typedef unsigned char *sk_buff_data_t;
>> #endif
>>
>> +enum skb_tstamp_type {
>> + SKB_CLOCK_REALTIME,
>> + SKB_CLOCK_MONOTONIC,
>> +};
>> +
>> /**
>> * DOC: Basic sk_buff geometry
>> *
>> @@ -823,10 +828,9 @@ 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
>> - * delivery_time in mono clock base (i.e. EDT). Otherwise, the
>> - * skb->tstamp has the (rcv) timestamp at ingress and
>> - * delivery_time at egress.
>> + * @tstamp_type: When set, skb->tstamp has the
>> + * delivery_time in mono clock base Otherwise, the
>> + * timestamp is considered real clock base.
>
> Missing period. More importantly, no longer conditional. It always
> captures the type of skb->tstamp.
>
I think i should move the patchset 2 documentation to this patch itself.
@tstamp_type: When set, skb->tstamp has the
+ * delivery_time clock base of skb->tstamp.
>> --- a/net/ipv4/tcp_output.c
>> +++ b/net/ipv4/tcp_output.c
>> @@ -1301,7 +1301,7 @@ 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_type_by_clockid(skb, tp->tcp_wstamp_ns, CLOCK_MONOTONIC);
>> if (clone_it) {
>> oskb = skb;
>>
>> @@ -1655,7 +1655,7 @@ int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
>>
>> skb_split(skb, buff, len);
>>
>> - skb_set_delivery_time(buff, skb->tstamp, true);
>> + skb_set_delivery_type_by_clockid(buff, skb->tstamp, CLOCK_MONOTONIC);
>> tcp_fragment_tstamp(skb, buff);
>
> All these hardcoded monotonic calls in TCP can be the shorter version
>
> skb_set_delivery_type(.., SKB_CLOCK_MONOTONIC);
I think i should directly call skb_set_delivery_time if i know that TCP always uses Monotonic clock base,
rather than calling the wrapper api which does nothing but switch and then calls skb_set_delivery_Time.
Makes sense. I will make the changes in v7 .
>
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