Re: [RFC PATCH bpf-next v7 3/3] selftests/bpf: Handle forwarding of UDP CLOCK_TAI packets

[Martin KaFai Lau <martin.lau@linux.dev>]

On 5/8/24 2:58 PM, 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.

The set lgtm. I have a few final nits on the test.

> 
> Link: https://lore.kernel.org/netdev/bc037db4-58bb-4861-ac31-a361a93841d3@linux.dev/
> Signed-off-by: Abhishek Chauhan <quic_abchauha@quicinc.com>
> ---
> Changes since v7
> - Fixed  issues in the ctx_rewrite.c
>    with respect to dissembly in both
>    .read and .write
> 
> Changes since v6
> - Moved all the selftest to another patch
> 
> Changes since v1 - v5
> - Patch was not present
> 
>   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

nit. Please move this bpf.h sync changes to patch 2 where the uapi changes happen.

> @@ -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..08b6391f2f56 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 *)($ctx + sk_buff::__mono_tc_offset);"
> -			 "w11 &= 3;"
> -			 "if w11 != 0x3 goto pc+2;"
> +			 "if w11 & 0x4 goto pc+1;"
> +			 "goto pc+4;"
> +			 "if w11 & 0x3 goto pc+1;"
> +			 "goto pc+2;"
>   			 "$dst = 0;"
>   			 "goto pc+1;"
>   			 "$dst = *(u64 *)($ctx + sk_buff::tstamp);",
>   		.write = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
> -			 "if w11 & 0x2 goto pc+1;"
> +			 "if w11 & 0x4 goto pc+1;"
>   			 "goto pc+2;"
> -			 "w11 &= -2;"
> +			 "w11 &= -4;"
>   			 "*(u8 *)($ctx + sk_buff::__mono_tc_offset) = r11;"
>   			 "*(u64 *)($ctx + sk_buff::tstamp) = $src;",
>   	},
> diff --git a/tools/testing/selftests/bpf/prog_tests/tc_redirect.c b/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
> index b1073d36d77a..327d51f59142 100644
> --- a/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
> +++ b/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
> @@ -890,9 +890,6 @@ static void test_udp_dtime(struct test_tc_dtime *skel, int family, bool bpf_fwd)
>   
>   	ASSERT_EQ(dtimes[INGRESS_FWDNS_P100], 0,
>   		  dtime_cnt_str(t, INGRESS_FWDNS_P100));
> -	/* non mono delivery time is not forwarded */
> -	ASSERT_EQ(dtimes[INGRESS_FWDNS_P101], 0,
> -		  dtime_cnt_str(t, INGRESS_FWDNS_P101));
>   	for (i = EGRESS_FWDNS_P100; i < SET_DTIME; i++)
>   		ASSERT_GT(dtimes[i], 0, dtime_cnt_str(t, i));
>   
> diff --git a/tools/testing/selftests/bpf/progs/test_tc_dtime.c b/tools/testing/selftests/bpf/progs/test_tc_dtime.c
> index 74ec09f040b7..21f5be202e4b 100644
> --- a/tools/testing/selftests/bpf/progs/test_tc_dtime.c
> +++ b/tools/testing/selftests/bpf/progs/test_tc_dtime.c
> @@ -222,13 +222,19 @@ int egress_host(struct __sk_buff *skb)
>   		return TC_ACT_OK;
>   
>   	if (skb_proto(skb_type) == IPPROTO_TCP) {
> -		if (skb->tstamp_type == BPF_SKB_TSTAMP_DELIVERY_MONO &&
> +		if (skb->tstamp_type == BPF_SKB_CLOCK_MONOTONIC &&
> +		    skb->tstamp)
> +			inc_dtimes(EGRESS_ENDHOST);
> +		else
> +			inc_errs(EGRESS_ENDHOST);
> +	} else if (skb_proto(skb_type) == IPPROTO_UDP) {
> +		if (skb->tstamp_type == BPF_SKB_CLOCK_TAI &&
>   		    skb->tstamp)
>   			inc_dtimes(EGRESS_ENDHOST);
>   		else
>   			inc_errs(EGRESS_ENDHOST);
>   	} else {
> -		if (skb->tstamp_type == BPF_SKB_TSTAMP_UNSPEC &&
> +		if (skb->tstamp_type == BPF_SKB_CLOCK_REALTIME &&
>   		    skb->tstamp)

Since the UDP+TAI can be handled properly in the above "else if" case now, I 
would like to further tighten the bolt on detecting the non-zero REALTIME 
skb->tstamp here since it should not happen at egress. Something like:

	} else {
		if (skb->tstamp_type == BPF_SKB_CLOCK_REALTIME &&
		    skb->tstamp)
			inc_errs(EGRESS_ENDHOST);
	}

I ran the test (w or w/o the above inc_errs changes) in a loop and it 
consistently passes now.

Other than the above small nits, in the next re-spin, please remove the RFC tag 
and you can carry my reviewed-by to all 3 patches. Thanks.

Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>

>   			inc_dtimes(EGRESS_ENDHOST);
>   		else