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selftest: Don't reuse port for SO_INCOMING_CPU test.

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Jakub reported that ASSERT_EQ(cpu, i) in so_incoming_cpu.c seems to
fire somewhat randomly.

  # #  RUN           so_incoming_cpu.before_reuseport.test3 ...
  # # so_incoming_cpu.c:191:test3:Expected cpu (32) == i (0)
  # # test3: Test terminated by assertion
  # #          FAIL  so_incoming_cpu.before_reuseport.test3
  # not ok 3 so_incoming_cpu.before_reuseport.test3

When the test failed, not-yet-accepted CLOSE_WAIT sockets received
SYN with a "challenging" SEQ number, which was sent from an unexpected
CPU that did not create the receiver.

The test basically does:

  1. for each cpu:
    1-1. create a server
    1-2. set SO_INCOMING_CPU

  2. for each cpu:
    2-1. set cpu affinity
    2-2. create some clients
    2-3. let clients connect() to the server on the same cpu
    2-4. close() clients

  3. for each server:
    3-1. accept() all child sockets
    3-2. check if all children have the same SO_INCOMING_CPU with the server

The root cause was the close() in 2-4. and net.ipv4.tcp_tw_reuse.

In a loop of 2., close() changed the client state to FIN_WAIT_2, and
the peer transitioned to CLOSE_WAIT.

In another loop of 2., connect() happened to select the same port of
the FIN_WAIT_2 socket, and it was reused as the default value of
net.ipv4.tcp_tw_reuse is 2.

As a result, the new client sent SYN to the CLOSE_WAIT socket from
a different CPU, and the receiver's sk_incoming_cpu was overwritten
with unexpected CPU ID.

Also, the SYN had a different SEQ number, so the CLOSE_WAIT socket
responded with Challenge ACK.  The new client properly returned RST
and effectively killed the CLOSE_WAIT socket.

This way, all clients were created successfully, but the error was
detected later by 3-2., ASSERT_EQ(cpu, i).

To avoid the failure, let's make sure that (i) the number of clients
is less than the number of available ports and (ii) such reuse never
happens.

Fixes: 6df96146b202 ("selftest: Add test for SO_INCOMING_CPU.")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Tested-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20240120031642.67014-1-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2024-01-19 19:16:42 -08:00 committed by Paolo Abeni
parent 7267e8dcad
commit 97de5a15ed
1 changed files with 50 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
tools/testing/selftests/net/so_incoming_cpu.c
View File

@ -3,19 +3,16 @@
#define _GNU_SOURCE
#include <sched.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/sysinfo.h>
#include "../kselftest_harness.h"
#define CLIENT_PER_SERVER 32 /* More sockets, more reliable */
#define NR_SERVER self->nproc
#define NR_CLIENT (CLIENT_PER_SERVER * NR_SERVER)
FIXTURE(so_incoming_cpu)
{
int nproc;
int *servers;
union {
struct sockaddr addr;
@ -56,12 +53,47 @@ FIXTURE_VARIANT_ADD(so_incoming_cpu, after_all_listen)
.when_to_set = AFTER_ALL_LISTEN,
};
static void write_sysctl(struct __test_metadata *_metadata,
char *filename, char *string)
{
int fd, len, ret;
fd = open(filename, O_WRONLY);
ASSERT_NE(fd, -1);
len = strlen(string);
ret = write(fd, string, len);
ASSERT_EQ(ret, len);
}
static void setup_netns(struct __test_metadata *_metadata)
{
ASSERT_EQ(unshare(CLONE_NEWNET), 0);
ASSERT_EQ(system("ip link set lo up"), 0);
write_sysctl(_metadata, "/proc/sys/net/ipv4/ip_local_port_range", "10000 60001");
write_sysctl(_metadata, "/proc/sys/net/ipv4/tcp_tw_reuse", "0");
}
#define NR_PORT (60001 - 10000 - 1)
#define NR_CLIENT_PER_SERVER_DEFAULT 32
static int nr_client_per_server, nr_server, nr_client;
FIXTURE_SETUP(so_incoming_cpu)
{
self->nproc = get_nprocs();
ASSERT_LE(2, self->nproc);
setup_netns(_metadata);
self->servers = malloc(sizeof(int) * NR_SERVER);
nr_server = get_nprocs();
ASSERT_LE(2, nr_server);
if (NR_CLIENT_PER_SERVER_DEFAULT * nr_server < NR_PORT)
nr_client_per_server = NR_CLIENT_PER_SERVER_DEFAULT;
else
nr_client_per_server = NR_PORT / nr_server;
nr_client = nr_client_per_server * nr_server;
self->servers = malloc(sizeof(int) * nr_server);
ASSERT_NE(self->servers, NULL);
self->in_addr.sin_family = AF_INET;
@ -74,7 +106,7 @@ FIXTURE_TEARDOWN(so_incoming_cpu)
{
int i;
for (i = 0; i < NR_SERVER; i++)
for (i = 0; i < nr_server; i++)
close(self->servers[i]);
free(self->servers);
@ -110,10 +142,10 @@ int create_server(struct __test_metadata *_metadata,
if (variant->when_to_set == BEFORE_LISTEN)
set_so_incoming_cpu(_metadata, fd, cpu);
/* We don't use CLIENT_PER_SERVER here not to block
/* We don't use nr_client_per_server here not to block
* this test at connect() if SO_INCOMING_CPU is broken.
*/
ret = listen(fd, NR_CLIENT);
ret = listen(fd, nr_client);
ASSERT_EQ(ret, 0);
if (variant->when_to_set == AFTER_LISTEN)
@ -128,7 +160,7 @@ void create_servers(struct __test_metadata *_metadata,
{
int i, ret;
for (i = 0; i < NR_SERVER; i++) {
for (i = 0; i < nr_server; i++) {
self->servers[i] = create_server(_metadata, self, variant, i);
if (i == 0) {
@ -138,7 +170,7 @@ void create_servers(struct __test_metadata *_metadata,
}
if (variant->when_to_set == AFTER_ALL_LISTEN) {
for (i = 0; i < NR_SERVER; i++)
for (i = 0; i < nr_server; i++)
set_so_incoming_cpu(_metadata, self->servers[i], i);
}
}
@ -149,7 +181,7 @@ void create_clients(struct __test_metadata *_metadata,
cpu_set_t cpu_set;
int i, j, fd, ret;
for (i = 0; i < NR_SERVER; i++) {
for (i = 0; i < nr_server; i++) {
CPU_ZERO(&cpu_set);
CPU_SET(i, &cpu_set);
@ -162,7 +194,7 @@ void create_clients(struct __test_metadata *_metadata,
ret = sched_setaffinity(0, sizeof(cpu_set), &cpu_set);
ASSERT_EQ(ret, 0);
for (j = 0; j < CLIENT_PER_SERVER; j++) {
for (j = 0; j < nr_client_per_server; j++) {
fd = socket(AF_INET, SOCK_STREAM, 0);
ASSERT_NE(fd, -1);
@ -180,8 +212,8 @@ void verify_incoming_cpu(struct __test_metadata *_metadata,
int i, j, fd, cpu, ret, total = 0;
socklen_t len = sizeof(int);
for (i = 0; i < NR_SERVER; i++) {
for (j = 0; j < CLIENT_PER_SERVER; j++) {
for (i = 0; i < nr_server; i++) {
for (j = 0; j < nr_client_per_server; j++) {
/* If we see -EAGAIN here, SO_INCOMING_CPU is broken */
fd = accept(self->servers[i], &self->addr, &self->addrlen);
ASSERT_NE(fd, -1);
@ -195,7 +227,7 @@ void verify_incoming_cpu(struct __test_metadata *_metadata,
}
}
ASSERT_EQ(total, NR_CLIENT);
ASSERT_EQ(total, nr_client);
TH_LOG("SO_INCOMING_CPU is very likely to be "
"working correctly with %d sockets.", total);
}