On 3/12/2024 4:52 PM, Martin KaFai Lau wrote: > On 3/1/24 12:13 PM, Abhishek Chauhan wrote: >> Bridge driver today has no support to forward the userspace timestamp >> packets and ends up resetting the timestamp. ETF qdisc checks the >> packet coming from userspace and encounters to be 0 thereby dropping >> time sensitive packets. These changes will allow userspace timestamps >> packets to be forwarded from the bridge to NIC drivers. >> >> Setting the same bit (mono_delivery_time) to avoid dropping of >> userspace tstamp packets in the forwarding path. >> >> Existing functionality of mono_delivery_time remains unaltered here, >> instead just extended with userspace tstamp support for bridge >> forwarding path. > > The patch currently broke the bpf selftest test_tc_dtime: https://github.com/kernel-patches/bpf/actions/runs/8242487344/job/22541746675 > > In particular, there is a uapi field __sk_buff->tstamp_type which currently has BPF_SKB_TSTAMP_DELIVERY_MONO to mean skb->tstamp has the MONO "delivery" time. BPF_SKB_TSTAMP_UNSPEC means everything else (this could be a rx timestamp at ingress or a delivery time set by user space). > > __sk_buff->tstamp_type depends on skb->mono_delivery_time which does not necessarily mean mono after this patch. I thought about fixing it on the bpf side such that reading __sk_buff->tstamp_type only returns BPF_SKB_TSTAMP_DELIVERY_MONO when the skb->mono_delivery_time is set and skb->sk is IPPROTO_TCP. However, it won't work because of bpf_skb_set_tstamp(). > > There is a bpf helper, bpf_skb_set_tstamp(skb, tstamp, BPF_SKB_TSTAMP_DELIVERY_MONO). This helper changes both the skb->tstamp and the skb->mono_delivery_time. The expectation is this could change skb->tstamp in the ingress skb and redirect to egress sch_fq. It could also set a mono time to skb->tstamp where the udp sk->sk_clockid may not be necessary in mono and then bpf_redirect to egress sch_fq. When bpf_skb_set_tstamp(skb, tstamp, BPF_SKB_TSTAMP_DELIVERY_MONO) succeeds, reading __sk_buff->tstamp_type expects BPF_SKB_TSTAMP_DELIVERY_MONO also. > > I ran out of idea to solve this uapi breakage. > > I am afraid it may need to go back to v1 idea and use another bit (user_delivery_time) in the skb. > I am okay to switch back to version 1 of this patch by adding another bit called userspace_time_stamp as that was the initial intent. Martin what do you suggest ?
