selftest: Add test for SO_INCOMING_CPU.

Some highly optimised applications use SO_INCOMING_CPU to make them
efficient, but they didn't test if it's working correctly by getsockopt()
to avoid slowing down.  As a result, no one noticed it had been broken
for years, so it's a good time to add a test to catch future regression.

The test does

  1) Create $(nproc) TCP listeners associated with each CPU.

  2) Create 32 child sockets for each listener by calling
     sched_setaffinity() for each CPU.

  3) Check if accept()ed sockets' sk_incoming_cpu matches
     listener's one.

If we see -EAGAIN, SO_INCOMING_CPU is broken.  However, we might not see
any error even if broken; the kernel could miraculously distribute all SYN
to correct listeners.  Not to let that happen, we must increase the number
of clients and CPUs to some extent, so the test requires $(nproc) >= 2 and
creates 64 sockets at least.

Test:
  $ nproc
  96
  $ ./so_incoming_cpu

Before the previous patch:

  # Starting 12 tests from 5 test cases.
  #  RUN           so_incoming_cpu.before_reuseport.test1 ...
  # so_incoming_cpu.c:191:test1:Expected cpu (5) == i (0)
  # test1: Test terminated by assertion
  #          FAIL  so_incoming_cpu.before_reuseport.test1
  not ok 1 so_incoming_cpu.before_reuseport.test1
  ...
  # FAILED: 0 / 12 tests passed.
  # Totals: pass:0 fail:12 xfail:0 xpass:0 skip:0 error:0

After:

  # Starting 12 tests from 5 test cases.
  #  RUN           so_incoming_cpu.before_reuseport.test1 ...
  # so_incoming_cpu.c:199:test1:SO_INCOMING_CPU is very likely to be working correctly with 3072 sockets.
  #            OK  so_incoming_cpu.before_reuseport.test1
  ok 1 so_incoming_cpu.before_reuseport.test1
  ...
  # PASSED: 12 / 12 tests passed.
  # Totals: pass:12 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

tools/testing/selftests/net/.gitignore

@@ -25,6 +25,7 @@ rxtimestamp
 sk_bind_sendto_listen
 sk_connect_zero_addr
 socket
+so_incoming_cpu
 so_netns_cookie
 so_txtime
 stress_reuseport_listen

tools/testing/selftests/net/Makefile

@@ -71,6 +71,7 @@ TEST_GEN_FILES += bind_bhash
 TEST_GEN_PROGS += sk_bind_sendto_listen
 TEST_GEN_PROGS += sk_connect_zero_addr
 TEST_PROGS += test_ingress_egress_chaining.sh
+TEST_GEN_PROGS += so_incoming_cpu
 
 TEST_FILES := settings
 

tools/testing/selftests/net/so_incoming_cpu.c

@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+#define _GNU_SOURCE
+#include <sched.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;
+		struct sockaddr_in in_addr;
+	};
+	socklen_t addrlen;
+};
+
+enum when_to_set {
+	BEFORE_REUSEPORT,
+	BEFORE_LISTEN,
+	AFTER_LISTEN,
+	AFTER_ALL_LISTEN,
+};
+
+FIXTURE_VARIANT(so_incoming_cpu)
+{
+	int when_to_set;
+};
+
+FIXTURE_VARIANT_ADD(so_incoming_cpu, before_reuseport)
+{
+	.when_to_set = BEFORE_REUSEPORT,
+};
+
+FIXTURE_VARIANT_ADD(so_incoming_cpu, before_listen)
+{
+	.when_to_set = BEFORE_LISTEN,
+};
+
+FIXTURE_VARIANT_ADD(so_incoming_cpu, after_listen)
+{
+	.when_to_set = AFTER_LISTEN,
+};
+
+FIXTURE_VARIANT_ADD(so_incoming_cpu, after_all_listen)
+{
+	.when_to_set = AFTER_ALL_LISTEN,
+};
+
+FIXTURE_SETUP(so_incoming_cpu)
+{
+	self->nproc = get_nprocs();
+	ASSERT_LE(2, self->nproc);
+
+	self->servers = malloc(sizeof(int) * NR_SERVER);
+	ASSERT_NE(self->servers, NULL);
+
+	self->in_addr.sin_family = AF_INET;
+	self->in_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+	self->in_addr.sin_port = htons(0);
+	self->addrlen = sizeof(struct sockaddr_in);
+}
+
+FIXTURE_TEARDOWN(so_incoming_cpu)
+{
+	int i;
+
+	for (i = 0; i < NR_SERVER; i++)
+		close(self->servers[i]);
+
+	free(self->servers);
+}
+
+void set_so_incoming_cpu(struct __test_metadata *_metadata, int fd, int cpu)
+{
+	int ret;
+
+	ret = setsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, sizeof(int));
+	ASSERT_EQ(ret, 0);
+}
+
+int create_server(struct __test_metadata *_metadata,
+		  FIXTURE_DATA(so_incoming_cpu) *self,
+		  const FIXTURE_VARIANT(so_incoming_cpu) *variant,
+		  int cpu)
+{
+	int fd, ret;
+
+	fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
+	ASSERT_NE(fd, -1);
+
+	if (variant->when_to_set == BEFORE_REUSEPORT)
+		set_so_incoming_cpu(_metadata, fd, cpu);
+
+	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &(int){1}, sizeof(int));
+	ASSERT_EQ(ret, 0);
+
+	ret = bind(fd, &self->addr, self->addrlen);
+	ASSERT_EQ(ret, 0);
+
+	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
+	 * this test at connect() if SO_INCOMING_CPU is broken.
+	 */
+	ret = listen(fd, NR_CLIENT);
+	ASSERT_EQ(ret, 0);
+
+	if (variant->when_to_set == AFTER_LISTEN)
+		set_so_incoming_cpu(_metadata, fd, cpu);
+
+	return fd;
+}
+
+void create_servers(struct __test_metadata *_metadata,
+		    FIXTURE_DATA(so_incoming_cpu) *self,
+		    const FIXTURE_VARIANT(so_incoming_cpu) *variant)
+{
+	int i, ret;
+
+	for (i = 0; i < NR_SERVER; i++) {
+		self->servers[i] = create_server(_metadata, self, variant, i);
+
+		if (i == 0) {
+			ret = getsockname(self->servers[i], &self->addr, &self->addrlen);
+			ASSERT_EQ(ret, 0);
+		}
+	}
+
+	if (variant->when_to_set == AFTER_ALL_LISTEN) {
+		for (i = 0; i < NR_SERVER; i++)
+			set_so_incoming_cpu(_metadata, self->servers[i], i);
+	}
+}
+
+void create_clients(struct __test_metadata *_metadata,
+		    FIXTURE_DATA(so_incoming_cpu) *self)
+{
+	cpu_set_t cpu_set;
+	int i, j, fd, ret;
+
+	for (i = 0; i < NR_SERVER; i++) {
+		CPU_ZERO(&cpu_set);
+
+		CPU_SET(i, &cpu_set);
+		ASSERT_EQ(CPU_COUNT(&cpu_set), 1);
+		ASSERT_NE(CPU_ISSET(i, &cpu_set), 0);
+
+		/* Make sure SYN will be processed on the i-th CPU
+		 * and finally distributed to the i-th listener.
+		 */
+		sched_setaffinity(0, sizeof(cpu_set), &cpu_set);
+		ASSERT_EQ(ret, 0);
+
+		for (j = 0; j < CLIENT_PER_SERVER; j++) {
+			fd  = socket(AF_INET, SOCK_STREAM, 0);
+			ASSERT_NE(fd, -1);
+
+			ret = connect(fd, &self->addr, self->addrlen);
+			ASSERT_EQ(ret, 0);
+
+			close(fd);
+		}
+	}
+}
+
+void verify_incoming_cpu(struct __test_metadata *_metadata,
+			 FIXTURE_DATA(so_incoming_cpu) *self)
+{
+	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++) {
+			/* If we see -EAGAIN here, SO_INCOMING_CPU is broken */
+			fd = accept(self->servers[i], &self->addr, &self->addrlen);
+			ASSERT_NE(fd, -1);
+
+			ret = getsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, &len);
+			ASSERT_EQ(ret, 0);
+			ASSERT_EQ(cpu, i);
+
+			close(fd);
+			total++;
+		}
+	}
+
+	ASSERT_EQ(total, NR_CLIENT);
+	TH_LOG("SO_INCOMING_CPU is very likely to be "
+	       "working correctly with %d sockets.", total);
+}
+
+TEST_F(so_incoming_cpu, test1)
+{
+	create_servers(_metadata, self, variant);
+	create_clients(_metadata, self);
+	verify_incoming_cpu(_metadata, self);
+}
+
+TEST_F(so_incoming_cpu, test2)
+{
+	int server;
+
+	create_servers(_metadata, self, variant);
+
+	/* No CPU specified */
+	server = create_server(_metadata, self, variant, -1);
+	close(server);
+
+	create_clients(_metadata, self);
+	verify_incoming_cpu(_metadata, self);
+}
+
+TEST_F(so_incoming_cpu, test3)
+{
+	int server, client;
+
+	create_servers(_metadata, self, variant);
+
+	/* No CPU specified */
+	server = create_server(_metadata, self, variant, -1);
+
+	create_clients(_metadata, self);
+
+	/* Never receive any requests */
+	client = accept(server, &self->addr, &self->addrlen);
+	ASSERT_EQ(client, -1);
+
+	verify_incoming_cpu(_metadata, self);
+}
+
+TEST_HARNESS_MAIN