Re: [PATCH bpf v3 2/2] selftests/bpf: Test TCP_NODELAY in TCP hdr opt callbacks

[Jiayuan Chen]

On 4/17/26 5:20 PM, KaFai Wan wrote:

Add a sockops selftest for the TCP_NODELAY restriction in
BPF_SOCK_OPS_HDR_OPT_LEN_CB and BPF_SOCK_OPS_WRITE_HDR_OPT_CB.

With BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG enabled,
bpf_setsockopt(TCP_NODELAY) returns -EOPNOTSUPP from
BPF_SOCK_OPS_HDR_OPT_LEN_CB and BPF_SOCK_OPS_WRITE_HDR_OPT_CB, avoiding
unbounded recursion and kernel stack overflow.

Other cases continue to work as before, including
BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB and user space
setsockopt(TCP_NODELAY).

Signed-off-by: KaFai Wan <kafai....@linux.dev>

Reviewed-by: Jiayuan Chen <jiayuan.c...@linux.dev>


A little nit below, no need to resend.

---
  .../selftests/bpf/prog_tests/tcp_hdr_options.c    | 12 +++++++++++-
  .../bpf/progs/test_misc_tcp_hdr_options.c         | 15 ++++++++++++++-
  2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_hdr_options.c 
b/tools/testing/selftests/bpf/prog_tests/tcp_hdr_options.c
index 56685fc03c7e..7b9dbbb84316 100644
--- a/tools/testing/selftests/bpf/prog_tests/tcp_hdr_options.c
+++ b/tools/testing/selftests/bpf/prog_tests/tcp_hdr_options.c
@@ -461,7 +461,7 @@ static void misc(void)
        const unsigned int nr_data = 2;
        struct bpf_link *link;
        struct sk_fds sk_fds;
-       int i, ret;
+       int i, ret, true_val = 1;

NIT: please follow the reverse xmas tree variable ordering

        lport_linum_map_fd = bpf_map__fd(misc_skel->maps.lport_linum_map);

@@ -477,6 +477,10 @@ static void misc(void)

                return;
        }

+ ret = setsockopt(sk_fds.active_fd, SOL_TCP, TCP_NODELAY, &true_val, sizeof(true_val));

+       if (!ASSERT_OK(ret, "setsockopt(TCP_NODELAY)"))
+               goto check_linum;
+
        for (i = 0; i < nr_data; i++) {
                /* MSG_EOR to ensure skb will not be combined */
                ret = send(sk_fds.active_fd, send_msg, sizeof(send_msg),
@@ -507,6 +511,12 @@ static void misc(void)

ASSERT_EQ(misc_skel->bss->nr_hwtstamp, 0, "nr_hwtstamp"); + ASSERT_TRUE(misc_skel->data->nodelay_est_ok, "unexpected nodelay_est_ok");

+
+       ASSERT_TRUE(misc_skel->data->nodelay_hdr_len_err, "unexpected 
nodelay_hdr_len_err");
+
+       ASSERT_TRUE(misc_skel->data->nodelay_write_hdr_err, "unexpected 
nodelay_write_hdr_err");
+

NIT: It's would be misleading if you run ./test_progs with "-v"
misc:PASS:unexpected nodelay_est_ok 0 nsec

"PASS:unexpected" ?

  check_linum:
        ASSERT_FALSE(check_error_linum(&sk_fds), "check_error_linum");
        sk_fds_close(&sk_fds);
diff --git a/tools/testing/selftests/bpf/progs/test_misc_tcp_hdr_options.c 
b/tools/testing/selftests/bpf/progs/test_misc_tcp_hdr_options.c
index d487153a839d..a02e28d9db2e 100644
--- a/tools/testing/selftests/bpf/progs/test_misc_tcp_hdr_options.c
+++ b/tools/testing/selftests/bpf/progs/test_misc_tcp_hdr_options.c
@@ -29,6 +29,10 @@ unsigned int nr_syn = 0;
  unsigned int nr_fin = 0;
  unsigned int nr_hwtstamp = 0;

+bool nodelay_est_ok = true;

+bool nodelay_hdr_len_err = true;
+bool nodelay_write_hdr_err = true;

I prefer "nodelay_hdr_len_reject"