Re: [PATCH bpf v1 2/2] selftests/bpf: Add protocol check test for bpf_sk_assign_tcp_reqsk()

[Martin KaFai Lau]

On 3/23/26 3:54 AM, Jiayuan Chen wrote:
+void test_tcp_custom_syncookie_protocol_check(void)
+{
+       struct test_tcp_custom_syncookie *skel;
+       struct sockaddr_in tcp_addr, udp_addr;
+       socklen_t addr_len = sizeof(tcp_addr);
+       int tcp_server = -1, udp_client = -1;
+       char buf[32] = "test";
+       int ret;
+
+       if (setup_netns())
+               return;
+
+       skel = test_tcp_custom_syncookie__open_and_load();
+       if (!ASSERT_OK_PTR(skel, "open_and_load"))
+               return;
  
+	/* Create a TCP listener so the BPF can find a LISTEN socket */
+       tcp_server = start_server(AF_INET, SOCK_STREAM, "127.0.0.1", 0, 0);
+       if (!ASSERT_NEQ(tcp_server, -1, "start tcp_server"))
+               goto destroy_skel;
+
+       ret = getsockname(tcp_server, (struct sockaddr *)&tcp_addr, &addr_len);
+       if (!ASSERT_OK(ret, "getsockname"))
+               goto close_tcp;
+
+       skel->bss->tcp_listener_port = ntohs(tcp_addr.sin_port);
+       skel->bss->udp_test_port = 9999;
+
+       ret = bpf_program__fd(skel->progs.tcp_custom_syncookie_badproto);
+       if (setup_tc(ret))
+               goto close_tcp;
+
+       udp_client = socket(AF_INET, SOCK_DGRAM, 0);
+       if (!ASSERT_NEQ(udp_client, -1, "udp socket"))
+               goto cleanup_tc;
+
+       memset(&udp_addr, 0, sizeof(udp_addr));
+       udp_addr.sin_family = AF_INET;
+       udp_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+       udp_addr.sin_port = htons(9999);
+
+       ret = sendto(udp_client, buf, sizeof(buf), 0,
+                    (struct sockaddr *)&udp_addr, sizeof(udp_addr));
+       ASSERT_EQ(ret, sizeof(buf), "sendto udp");
+
+       /* Wait for TC ingress BPF to process the skb. */
+       kern_sync_rcu();

hmm... is it guaranteed to work? Regardless, it checks the error 
returned from bpf_sk_assign_tcp_reqsk(). Maybe bpf_prog_test_run is simpler?

pw-bot: cr

+
+       ASSERT_EQ(skel->bss->udp_intercepted, true, "udp_intercepted");
+
+       /* assign_ret == 0 means kfunc accepted UDP skb (bug).
+        * assign_ret < 0 means kfunc correctly rejected it (fixed).
+        */
+       ASSERT_NEQ(skel->data->assign_ret, 0, "assign_ret");
+
+cleanup_tc:
+       system("tc qdisc del dev lo clsact");
+       if (udp_client >= 0)
+               close(udp_client);
+close_tcp:
+       close(tcp_server);
+destroy_skel:
        test_tcp_custom_syncookie__destroy(skel);
  }