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selftests/bpf: fix race in test_tcp_rtt test

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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: b55873984d ("selftests/bpf: test BPF_SOCK_OPS_RTT_CB")
Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Petar Penkov 2019-08-16 10:08:25 -07:00 committed by Daniel Borkmann
parent 929ffa6e9d
commit fae55527ac
1 changed files with 31 additions and 0 deletions
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31
tools/testing/selftests/bpf/test_tcp_rtt.c
View File

@ -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: