On Fri, Aug 16, 2019 at 9:13 AM Stanislav Fomichev <sdf@xxxxxxxxxxx> wrote:
>
> 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.
> >
> > 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..2b4754473956 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;
> > +
> > + sleep(1);
> Isn't it too big of a hammer? Maybe usleep(10) here and do x100 retries
> instead?
>
I guess this is more consistent with the time we expect to wait for an
ACK in the test, will change and send out a v2 shortly. Thank you for
your quick review!
> > + }
> > +
> > + 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, 5) < 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
> >
