Commit fae55527 authored by Petar Penkov's avatar Petar Penkov Committed by Daniel Borkmann
Browse files

selftests/bpf: fix race in test_tcp_rtt test 



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: b5587398 ("selftests/bpf: test BPF_SOCK_OPS_RTT_CB")
Signed-off-by: default avatarPetar Penkov <ppenkov@google.com>
Reviewed-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 929ffa6e

tools/testing/selftests/bpf/test_tcp_rtt.c

+31 −0
Original line number Diff line number Diff line
@@ -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:

CRA Git | Maintained and supported by SUSTech CRA and CCSE