selftests/bpf: Test TCP_NODELAY in TCP hdr opt callbacks

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.

Signed-off-by: KaFai Wan <kafai.wan@linux.dev>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://patch.msgid.link/20260421155804.135786-4-kafai.wan@linux.dev

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 56685fc03c7e9ecedb4212f888abd38ab7ff1152..80e6315da2a51507074b7f7882e96a271cfd77e6 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/tcp_hdr_options.c
+++ b/tools/testing/selftests/bpf/prog_tests/tcp_hdr_options.c
@@ -507,6 +507,10 @@ static void misc(void)
 
        ASSERT_EQ(misc_skel->bss->nr_hwtstamp, 0, "nr_hwtstamp");
 
+       ASSERT_TRUE(misc_skel->bss->nodelay_est_ok, "nodelay_est_ok");
+       ASSERT_TRUE(misc_skel->bss->nodelay_hdr_len_reject, "nodelay_hdr_len_reject");
+       ASSERT_TRUE(misc_skel->bss->nodelay_write_hdr_reject, "nodelay_write_hdr_reject");
+
 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 d487153a839d71b9a4203fd0e476a85ef38660e0..ed5a0011b8639fa839f4eed307973e36dd43c484 100644 (file)
--- 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 = false;
+bool nodelay_hdr_len_reject = false;
+bool nodelay_write_hdr_reject = false;
+
 /* Check the header received from the active side */
 static int __check_active_hdr_in(struct bpf_sock_ops *skops, bool check_syn)
 {
@@ -300,7 +304,7 @@ static int handle_passive_estab(struct bpf_sock_ops *skops)
 SEC("sockops")
 int misc_estab(struct bpf_sock_ops *skops)
 {
-       int true_val = 1;
+       int true_val = 1, false_val = 0, ret;
 
        switch (skops->op) {
        case BPF_SOCK_OPS_TCP_LISTEN_CB:
@@ -316,10 +320,19 @@ int misc_estab(struct bpf_sock_ops *skops)
        case BPF_SOCK_OPS_PARSE_HDR_OPT_CB:
                return handle_parse_hdr(skops);
        case BPF_SOCK_OPS_HDR_OPT_LEN_CB:
+               ret = bpf_setsockopt(skops, SOL_TCP, TCP_NODELAY, &true_val, sizeof(true_val));
+               if (ret == -EOPNOTSUPP)
+                       nodelay_hdr_len_reject = true;
                return handle_hdr_opt_len(skops);
        case BPF_SOCK_OPS_WRITE_HDR_OPT_CB:
+               ret = bpf_setsockopt(skops, SOL_TCP, TCP_NODELAY, &true_val, sizeof(true_val));
+               if (ret == -EOPNOTSUPP)
+                       nodelay_write_hdr_reject = true;
                return handle_write_hdr_opt(skops);
        case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
+               ret = bpf_setsockopt(skops, SOL_TCP, TCP_NODELAY, &false_val, sizeof(false_val));
+               if (!ret)
+                       nodelay_est_ok = true;
                return handle_passive_estab(skops);
        }