Re: [RFC PATCH bpf-next v6 3/3] selftests/bpf: Handle forwarding of UDP CLOCK_TAI packets

From: Willem de Bruijn
Date: Mon May 06 2024 - 15:04:34 EST


Abhishek Chauhan wrote:
> With changes in the design to forward CLOCK_TAI in the skbuff
> framework, existing selftest framework needs modification
> to handle forwarding of UDP packets with CLOCK_TAI as clockid.
>
> Link: https://lore.kernel.org/netdev/bc037db4-58bb-4861-ac31-a361a93841d3@xxxxxxxxx/
> Signed-off-by: Abhishek Chauhan <quic_abchauha@xxxxxxxxxxx>
> ---
> tools/include/uapi/linux/bpf.h | 15 ++++---
> .../selftests/bpf/prog_tests/ctx_rewrite.c | 10 +++--
> .../selftests/bpf/prog_tests/tc_redirect.c | 3 --
> .../selftests/bpf/progs/test_tc_dtime.c | 39 +++++++++----------
> 4 files changed, 34 insertions(+), 33 deletions(-)
>
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 90706a47f6ff..25ea393cf084 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -6207,12 +6207,17 @@ union { \
> __u64 :64; \
> } __attribute__((aligned(8)))
>
> +/* The enum used in skb->tstamp_type. It specifies the clock type
> + * of the time stored in the skb->tstamp.
> + */
> enum {
> - BPF_SKB_TSTAMP_UNSPEC,
> - BPF_SKB_TSTAMP_DELIVERY_MONO, /* tstamp has mono delivery time */
> - /* For any BPF_SKB_TSTAMP_* that the bpf prog cannot handle,
> - * the bpf prog should handle it like BPF_SKB_TSTAMP_UNSPEC
> - * and try to deduce it by ingress, egress or skb->sk->sk_clockid.
> + BPF_SKB_TSTAMP_UNSPEC = 0, /* DEPRECATED */
> + BPF_SKB_TSTAMP_DELIVERY_MONO = 1, /* DEPRECATED */
> + BPF_SKB_CLOCK_REALTIME = 0,
> + BPF_SKB_CLOCK_MONOTONIC = 1,
> + BPF_SKB_CLOCK_TAI = 2,
> + /* For any future BPF_SKB_CLOCK_* that the bpf prog cannot handle,
> + * the bpf prog can try to deduce it by ingress/egress/skb->sk->sk_clockid.
> */
> };
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c b/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c
> index 3b7c57fe55a5..71940f4ef0fb 100644
> --- a/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c
> +++ b/tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c
> @@ -69,15 +69,17 @@ static struct test_case test_cases[] = {
> {
> N(SCHED_CLS, struct __sk_buff, tstamp),
> .read = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
> - "w11 &= 3;"
> - "if w11 != 0x3 goto pc+2;"
> + "if w11 == 0x4 goto pc+1;"
> + "goto pc+4;"
> + "if w11 == 0x3 goto pc+1;"
> + "goto pc+2;"

Not an expert on this code, and I see that the existing code already
has this below, but: isn't it odd and unnecessary to jump to an
unconditional jump statement?

> "$dst = 0;"
> "goto pc+1;"
> "$dst = *(u64 *)($ctx + sk_buff::tstamp);",
> .write = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
> - "if w11 & 0x2 goto pc+1;"
> + "if w11 & 0x4 goto pc+1;"
> "goto pc+2;"
> - "w11 &= -2;"
> + "w11 &= -3;"
> "*(u8 *)($ctx + sk_buff::__mono_tc_offset) = r11;"
> "*(u64 *)($ctx + sk_buff::tstamp) = $src;",
> },