Re: [RFC PATCH bpf-next v6 3/3] selftests/bpf: Handle forwarding of UDP CLOCK_TAI packets
From: Martin KaFai Lau
Date: Mon May 06 2024 - 20:54:33 EST
On 5/6/24 1:50 PM, Abhishek Chauhan (ABC) wrote:
On 5/6/2024 12:04 PM, Willem de Bruijn wrote:
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 *)($ctx + sk_buff::__mono_tc_offset);"
- "w11 &= 3;"
- "if w11 != 0x3 goto pc+2;"
+ "if w11 == 0x4 goto pc+1;"
+ "goto pc+4;"
+ "if w11 == 0x3 goto pc+1;"
+ "goto pc+2;"
Not an expert on this code, and I see that the existing code already
has this below, but: isn't it odd and unnecessary to jump to an
unconditional jump statement?
I am closely looking into your comment and i will evalute it(Martin can correct me
if the jumps are correct or not as i am new to BPF as well) but i found out that
JSET = "&" and not "==". So the above two ins has to change from -
Yes, this should be bitwise "&" instead of "==".
The bpf CI did report this:
https://github.com/kernel-patches/bpf/actions/runs/8947652196/job/24579927178
Please monitor the bpf CI test result.
Do you have issue running the test locally?
"if w11 == 0x4 goto pc+1;" ==>(needs to be corrected to) "if w11 & 0x4 goto pc+1;"
"if w11 == 0x3 goto pc+1;" ==> (needs to be correct to) "if w11 & 0x3 goto pc+1;"
"$dst = 0;"
"goto pc+1;"
"$dst = *(u64 *)($ctx + sk_buff::tstamp);",
.write = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
- "if w11 & 0x2 goto pc+1;"
+ "if w11 & 0x4 goto pc+1;"
"goto pc+2;"
- "w11 &= -2;"
+ "w11 &= -3;"
Martin,
Also i am not sure why the the dissembly complains because the value of SKB_TSTAMP_TYPE_MASK = 3 and we are
negating it ~3 = -3.
Can't match disassembly(left) with pattern(right):
r11 = *(u8 *)(r1 +129) ; r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset)
if w11 & 0x4 goto pc+1 ; if w11 & 0x4 goto pc+1
goto pc+2 ; goto pc+2
w11 &= -4 ; w11 &= -3
"*(u8 *)($ctx + sk_buff::__mono_tc_offset) = r11;"
"*(u64 *)($ctx + sk_buff::tstamp) = $src;",
},