On 08/16, Petar Penkov wrote:
> From: Petar Penkov <ppenkov@xxxxxxxxxx>
>
> There is a race in this test between receiving the ACK for the
> single-byte packet sent in the test, and reading the values from the
> map.
>
> This patch fixes this by having the client wait until there are no more
> unacknowledged packets.
Reviewed-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
Thanks!
>
> Before:
> for i in {1..1000}; do ../net/in_netns.sh ./test_tcp_rtt; \
> done | grep -c PASSED
> < trimmed error messages >
> 993
>
> After:
> for i in {1..10000}; do ../net/in_netns.sh ./test_tcp_rtt; \
> done | grep -c PASSED
> 10000
>
> Fixes: b55873984dab ("selftests/bpf: test BPF_SOCK_OPS_RTT_CB")
> Signed-off-by: Petar Penkov <ppenkov@xxxxxxxxxx>
> ---
> tools/testing/selftests/bpf/test_tcp_rtt.c | 31 ++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/test_tcp_rtt.c b/tools/testing/selftests/bpf/test_tcp_rtt.c
> index 90c3862f74a8..93916a69823e 100644
> --- a/tools/testing/selftests/bpf/test_tcp_rtt.c
> +++ b/tools/testing/selftests/bpf/test_tcp_rtt.c
> @@ -6,6 +6,7 @@
> #include <sys/types.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
> +#include <netinet/tcp.h>
> #include <pthread.h>
>
> #include <linux/filter.h>
> @@ -34,6 +35,30 @@ static void send_byte(int fd)
> error(1, errno, "Failed to send single byte");
> }
>
> +static int wait_for_ack(int fd, int retries)
> +{
> + struct tcp_info info;
> + socklen_t optlen;
> + int i, err;
> +
> + for (i = 0; i < retries; i++) {
> + optlen = sizeof(info);
> + err = getsockopt(fd, SOL_TCP, TCP_INFO, &info, &optlen);
> + if (err < 0) {
> + log_err("Failed to lookup TCP stats");
> + return err;
> + }
> +
> + if (info.tcpi_unacked == 0)
> + return 0;
> +
> + usleep(10);
> + }
> +
> + log_err("Did not receive ACK");
> + return -1;
> +}
> +
> static int verify_sk(int map_fd, int client_fd, const char *msg, __u32 invoked,
> __u32 dsack_dups, __u32 delivered, __u32 delivered_ce,
> __u32 icsk_retransmits)
> @@ -149,6 +174,11 @@ static int run_test(int cgroup_fd, int server_fd)
> /*icsk_retransmits=*/0);
>
> send_byte(client_fd);
> + if (wait_for_ack(client_fd, 100) < 0) {
> + err = -1;
> + goto close_client_fd;
> + }
> +
>
> err += verify_sk(map_fd, client_fd, "first payload byte",
> /*invoked=*/2,
> @@ -157,6 +187,7 @@ static int run_test(int cgroup_fd, int server_fd)
> /*delivered_ce=*/0,
> /*icsk_retransmits=*/0);
>
> +close_client_fd:
> close(client_fd);
>
> close_bpf_object:
> --
> 2.23.0.rc1.153.gdeed80330f-goog
>
