Re: [bpf-next PATCH v2 2/5] selftests/bpf: Drop python client/server in favor of threads

[Alexander Duyck <alexander.duyck@gmail.com>]

On Mon, Nov 2, 2020 at 4:38 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Sat, Oct 31, 2020 at 11:52:18AM -0700, Alexander Duyck wrote:
> > From: Alexander Duyck <alexanderduyck@fb.com>
> >
> > Drop the tcp_client/server.py files in favor of using a client and server
> > thread within the test case. Specifically we spawn a new thread to play the
> The thread comment may be outdated in v2.
>
> > role of the server, and the main testing thread plays the role of client.
> >
> > Add logic to the end of the run_test function to guarantee that the sockets
> > are closed when we begin verifying results.
> >
> > Doing this we are able to reduce overhead since we don't have two python
> > workers possibly floating around. In addition we don't have to worry about
> > synchronization issues and as such the retry loop waiting for the threads
> > to close the sockets can be dropped as we will have already closed the
> > sockets in the local executable and synchronized the server thread.
> >
> > Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
> > ---
> >  .../testing/selftests/bpf/prog_tests/tcpbpf_user.c |   96 ++++++++++++++++----
> >  tools/testing/selftests/bpf/tcp_client.py          |   50 ----------
> >  tools/testing/selftests/bpf/tcp_server.py          |   80 -----------------
> >  3 files changed, 78 insertions(+), 148 deletions(-)
> >  delete mode 100755 tools/testing/selftests/bpf/tcp_client.py
> >  delete mode 100755 tools/testing/selftests/bpf/tcp_server.py
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c b/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c
> > index 54f1dce97729..17d4299435df 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/tcpbpf_user.c
> > @@ -1,13 +1,14 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <inttypes.h>
> >  #include <test_progs.h>
> > +#include <network_helpers.h>
> >
> >  #include "test_tcpbpf.h"
> >
> > +#define LO_ADDR6 "::1"
> >  #define CG_NAME "/tcpbpf-user-test"
> >
> > -/* 3 comes from one listening socket + both ends of the connection */
> > -#define EXPECTED_CLOSE_EVENTS                3
> > +static __u32 duration;
> >
> >  #define EXPECT_EQ(expected, actual, fmt)                     \
> >       do {                                                    \
> > @@ -42,7 +43,9 @@ int verify_result(const struct tcpbpf_globals *result)
> >       EXPECT_EQ(0x80, result->bad_cb_test_rv, PRIu32);
> >       EXPECT_EQ(0, result->good_cb_test_rv, PRIu32);
> >       EXPECT_EQ(1, result->num_listen, PRIu32);
> > -     EXPECT_EQ(EXPECTED_CLOSE_EVENTS, result->num_close_events, PRIu32);
> > +
> > +     /* 3 comes from one listening socket + both ends of the connection */
> > +     EXPECT_EQ(3, result->num_close_events, PRIu32);
> >
> >       return ret;
> >  }
> > @@ -66,6 +69,75 @@ int verify_sockopt_result(int sock_map_fd)
> >       return ret;
> >  }
> >
> > +static int run_test(void)
> > +{
> > +     int listen_fd = -1, cli_fd = -1, accept_fd = -1;
> > +     char buf[1000];
> > +     int err = -1;
> > +     int i;
> > +
> > +     listen_fd = start_server(AF_INET6, SOCK_STREAM, LO_ADDR6, 0, 0);
> > +     if (CHECK(listen_fd == -1, "start_server", "listen_fd:%d errno:%d\n",
> > +               listen_fd, errno))
> > +             goto done;
> > +
> > +     cli_fd = connect_to_fd(listen_fd, 0);
> > +     if (CHECK(cli_fd == -1, "connect_to_fd(listen_fd)",
> > +               "cli_fd:%d errno:%d\n", cli_fd, errno))
> > +             goto done;
> > +
> > +     accept_fd = accept(listen_fd, NULL, NULL);
> > +     if (CHECK(accept_fd == -1, "accept(listen_fd)",
> > +               "accept_fd:%d errno:%d\n", accept_fd, errno))
> > +             goto done;
> > +
> > +     /* Send 1000B of '+'s from cli_fd -> accept_fd */
> > +     for (i = 0; i < 1000; i++)
> > +             buf[i] = '+';
> > +
> > +     err = send(cli_fd, buf, 1000, 0);
> > +     if (CHECK(err != 1000, "send(cli_fd)", "err:%d errno:%d\n", err, errno))
> > +             goto done;
> > +
> > +     err = recv(accept_fd, buf, 1000, 0);
> > +     if (CHECK(err != 1000, "recv(accept_fd)", "err:%d errno:%d\n", err, errno))
> > +             goto done;
> > +
> > +     /* Send 500B of '.'s from accept_fd ->cli_fd */
> > +     for (i = 0; i < 500; i++)
> > +             buf[i] = '.';
> > +
> > +     err = send(accept_fd, buf, 500, 0);
> > +     if (CHECK(err != 500, "send(accept_fd)", "err:%d errno:%d\n", err, errno))
> > +             goto done;
> > +
> > +     err = recv(cli_fd, buf, 500, 0);
> Unlikely, but err from the above send()/recv() could be 0.

Is that an issue? It would still trigger the check below as that is not 500.

> > +     if (CHECK(err != 500, "recv(cli_fd)", "err:%d errno:%d\n", err, errno))
> > +             goto done;
> > +
> > +     /*
> > +      * shutdown accept first to guarantee correct ordering for
> > +      * bytes_received and bytes_acked when we go to verify the results.
> > +      */
> > +     shutdown(accept_fd, SHUT_WR);
> > +     err = recv(cli_fd, buf, 1, 0);
> > +     if (CHECK(err, "recv(cli_fd) for fin", "err:%d errno:%d\n", err, errno))
> > +             goto done;
> > +
> > +     shutdown(cli_fd, SHUT_WR);
> > +     err = recv(accept_fd, buf, 1, 0);
> hmm... I was thinking cli_fd may still be in TCP_LAST_ACK
> but we can go with this version first and see if CI could
> really hit this case before resurrecting the idea on testing
> the TCP_LAST_ACK instead of TCP_CLOSE in test_tcpbpf_kern.c.

I ran with this for several hours and saw no issues with over 100K
iterations all of them passing. That is why I opted to just drop the
TCP_LAST_ACK patch.