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

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Message-ID: <663929b249143_516de2945@willemb.c.googlers.com.notmuch>
Date: Mon, 06 May 2024 15:04:18 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Abhishek Chauhan <quic_abchauha@...cinc.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>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.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 3/3] selftests/bpf: Handle forwarding of
 UDP CLOCK_TAI packets

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@linux.dev/
> Signed-off-by: Abhishek Chauhan <quic_abchauha@...cinc.com>
> ---
>  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;",
>  	},