On Tue, Feb 15, 2022 at 09:49:07PM +0100, Daniel Borkmann wrote:
> On 2/11/22 8:12 AM, Martin KaFai Lau wrote:
> [...]
> > The current use case is to keep the TCP mono delivery_time (EDT) and
> > to be used with sch_fq. A later patch will also allow tc-bpf@ingress
> > to read and change the mono delivery_time.
> >
> > In the future, another bit (e.g. skb->user_delivery_time) can be added
> [...]
> > ---
> > include/linux/skbuff.h | 13 +++++++++++++
> > net/bridge/netfilter/nf_conntrack_bridge.c | 5 +++--
> > net/ipv4/ip_output.c | 7 +++++--
> > net/ipv4/tcp_output.c | 16 +++++++++-------
> > net/ipv6/ip6_output.c | 5 +++--
> > net/ipv6/netfilter.c | 5 +++--
> > net/ipv6/tcp_ipv6.c | 2 +-
> > 7 files changed, 37 insertions(+), 16 deletions(-)
> >
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index a5adbf6b51e8..32c793de3801 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -747,6 +747,10 @@ 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.
> > * @napi_id: id of the NAPI struct this skb came from
> > * @sender_cpu: (aka @napi_id) source CPU in XPS
> > * @secmark: security marking
> > @@ -917,6 +921,7 @@ struct sk_buff {
> > __u8 decrypted:1;
> > #endif
> > __u8 slow_gro:1;
> > + __u8 mono_delivery_time:1;
>
> Don't you also need to extend sch_fq to treat any non-mono_delivery_time marked
> skb similar as if it hadn't been marked with a delivery time?
The current skb does not have clock base info, so the sch_fq does not depend
on it to work also. fq_packet_beyond_horizon() should already be a good guard
on the clock base difference. An extra check on the new mono_delivery_time does
not necessary add extra value on top.
