[PATCH bpf-next v8 1/9] selftests/bpf: Add backlog for network_helper_opts

[Geliang Tang]

From: Geliang Tang <tanggeli...@kylinos.cn>

Some callers expect __start_server() helper to pass their own "backlog"
value to listen() instead of the default of 1. So this patch adds struct
member "backlog" for network_helper_opts to allow callers to set "backlog"
value via start_server_str() helper.

listen(fd, 0 /* backlog */) can be used to enforce syncookie. Meaning
backlog 0 is a legit value.

Using 0 as a default and changing it to 1 here is fine. It makes the test
program easier to write for the common case. Enforcing syncookie mode by
using backlog 0 is a niche use case but it should at least have a way for
the caller to do that.

Signed-off-by: Geliang Tang <tanggeli...@kylinos.cn>
---
 tools/testing/selftests/bpf/network_helpers.c | 2 +-
 tools/testing/selftests/bpf/network_helpers.h | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c 
b/tools/testing/selftests/bpf/network_helpers.c
index 44c2c8fa542a..e0cba4178e41 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -106,7 +106,7 @@ static int __start_server(int type, const struct sockaddr 
*addr, socklen_t addrl
        }
 
        if (type == SOCK_STREAM) {
-               if (listen(fd, 1) < 0) {
+               if (listen(fd, opts->backlog ? MAX(opts->backlog, 0) : 1) < 0) {
                        log_err("Failed to listed on socket");
                        goto error_close;
                }
diff --git a/tools/testing/selftests/bpf/network_helpers.h 
b/tools/testing/selftests/bpf/network_helpers.h
index 9ea36524b9db..4f26bfc2dbf5 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -25,6 +25,10 @@ struct network_helper_opts {
        int timeout_ms;
        bool must_fail;
        int proto;
+       /* The backlog argument for listen(), defines the maximum length to 
which
+        * the queue of pending connections for sockfd may grow.
+        */
+       int backlog;
        int (*post_socket_cb)(int fd, void *opts);
        void *cb_opts;
 };
-- 
2.43.0