[PATCH bpf-next v2 2/4] selftests/bpf: Avoid jiffies quantization error in setget_sockopt

[Pu Lehui]

From: Pu Lehui <pulehui@xxxxxxxxxx>

The setget_sockopt selftest fails on kernels with HZ=250 (such as the
default on riscv64), specifically in the TCP_BPF_DELACK_MAX and
TCP_BPF_RTO_MIN sub-tests.

The test sets a socket option value in microseconds via bpf_setsockopt()
and immediately reads it back via bpf_getsockopt() to verify that it
matches. However, the kernel converts the value to jiffies internally
for storage and converts it back to microseconds upon retrieval. When
HZ=250 (4000 us per jiffy), 30000 us cannot be divided evenly:

  usecs_to_jiffies(30000) -> 8 jiffies
  jiffies_to_usecs(8)     -> 32000 us (!= 30000 us)

This mismatch triggers an assertion failure.

Change the test value from 30000 to 40000. 40000 us divides evenly
across common kernel timer frequencies (HZ=100, HZ=250, and HZ=1000),
avoiding quantization errors and making the test robust across different
architectures.

Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
---
 tools/testing/selftests/bpf/progs/setget_sockopt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/setget_sockopt.c b/tools/testing/selftests/bpf/progs/setget_sockopt.c
index d96e99b67aeb..95e6a337ab71 100644
--- a/tools/testing/selftests/bpf/progs/setget_sockopt.c
+++ b/tools/testing/selftests/bpf/progs/setget_sockopt.c
@@ -61,8 +61,8 @@ static const struct sockopt_test sol_tcp_tests[] = {
 	{ .opt = TCP_NOTSENT_LOWAT, .new = 1314, .expected = 1314, },
 	{ .opt = TCP_BPF_SOCK_OPS_CB_FLAGS, .new = BPF_SOCK_OPS_ALL_CB_FLAGS,
 	  .expected = BPF_SOCK_OPS_ALL_CB_FLAGS, },
-	{ .opt = TCP_BPF_DELACK_MAX, .new = 30000, .expected = 30000, },
-	{ .opt = TCP_BPF_RTO_MIN, .new = 30000, .expected = 30000, },
+	{ .opt = TCP_BPF_DELACK_MAX, .new = 40000, .expected = 40000, },
+	{ .opt = TCP_BPF_RTO_MIN, .new = 40000, .expected = 40000, },
 	{ .opt = TCP_RTO_MAX_MS, .new = 2000, .expected = 2000, },
 	{ .opt = 0, },
 };
-- 
2.34.1