[net-next] selftest: epoll_busy_poll: epoll busy poll tests

diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
index d996a0ab0765..777cfd027076 100644
--- a/tools/testing/selftests/net/.gitignore
+++ b/tools/testing/selftests/net/.gitignore
@@ -5,6 +5,7 @@  bind_wildcard
 csum
 cmsg_sender
 diag_uid
+epoll_busy_poll
 fin_ack_lat
 gro
 hwtstamp_config
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 5befca249452..c83c5d9c1ad9 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -84,6 +84,7 @@  TEST_GEN_FILES += sctp_hello
 TEST_GEN_FILES += csum
 TEST_GEN_FILES += ip_local_port_range
 TEST_GEN_FILES += bind_wildcard
+TEST_GEN_FILES += epoll_busy_poll
 TEST_PROGS += test_vxlan_mdb.sh
 TEST_PROGS += test_bridge_neigh_suppress.sh
 TEST_PROGS += test_vxlan_nolocalbypass.sh
diff --git a/tools/testing/selftests/net/epoll_busy_poll.c b/tools/testing/selftests/net/epoll_busy_poll.c
new file mode 100644
index 000000000000..3066a41a2acb
--- /dev/null
+++ b/tools/testing/selftests/net/epoll_busy_poll.c
@@ -0,0 +1,279 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Basic per-epoll context busy poll test.
+ *
+ * Only tests the ioctls, but should be expanded to test two connected hosts in
+ * the future
+ */
+
+#define _GNU_SOURCE
+
+#include <error.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/epoll.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+
+/* if the headers haven't been updated, we need to define some things */
+#if !defined(EPOLL_IOC_TYPE)
+struct epoll_params {
+	uint32_t busy_poll_usecs;
+	uint16_t busy_poll_budget;
+	uint8_t prefer_busy_poll;
+
+	/* pad the struct to a multiple of 64bits */
+	uint8_t __pad;
+};
+
+#define EPOLL_IOC_TYPE 0x8A
+#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
+#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
+#endif
+
+enum epoll_test_types {
+	TEST_UNDEFINED = -1,
+	TEST_SIMPLE = 0,
+};
+
+static enum epoll_test_types test_type = TEST_UNDEFINED;
+
+static void usage(const char *filepath)
+{
+	error(1, 0, "Usage: %s [options]", filepath);
+}
+
+static void parse_opts(int argc, char **argv)
+{
+	int c;
+
+	while ((c = getopt(argc, argv, "s")) != -1) {
+		switch (c) {
+		case 's':
+			test_type = TEST_SIMPLE;
+			break;
+		}
+	}
+
+	if (optind != argc)
+		usage(argv[0]);
+}
+
+static void do_simple_test_get_params(int fd)
+{
+	/* begin by getting the epoll params from the kernel
+	 *
+	 * the default should be default and all fields should be zero'd by the
+	 * kernel, so set params fields to garbage to test this.
+	 */
+	struct epoll_params *invalid_params;
+	struct epoll_params params;
+	int ret = 0;
+
+	params.busy_poll_usecs = 0xff;
+	params.busy_poll_budget = 0xff;
+	params.prefer_busy_poll = 1;
+	params.__pad = 0xf;
+
+	if (ioctl(fd, EPIOCGPARAMS, &params) != 0)
+		error(1, errno, "ioctl EPIOCGPARAMS");
+
+	if (params.busy_poll_usecs != 0)
+		error(1, 0, "EPIOCGPARAMS busy_poll_usecs should have been 0");
+
+	if (params.busy_poll_budget != 0)
+		error(1, 0, "EPIOCGPARAMS busy_poll_budget should have been 0");
+
+	if (params.prefer_busy_poll != 0)
+		error(1, 0, "EPIOCGPARAMS prefer_busy_poll should have been 0");
+
+	if (params.__pad != 0)
+		error(1, 0, "EPIOCGPARAMS __pad should have been 0");
+
+	invalid_params = (struct epoll_params *)0xdeadbeef;
+	ret = ioctl(fd, EPIOCGPARAMS, invalid_params);
+	if (ret != -1)
+		error(1, 0, "EPIOCGPARAMS should error with invalid params");
+
+	if (errno != EFAULT)
+		error(1, 0,
+		      "EPIOCGPARAMS with invalid params should set errno to EFAULT");
+}
+
+static void do_simple_test_set_invalid(int fd)
+{
+	/* Set some unacceptable values and check for error */
+	struct epoll_params *invalid_params;
+	struct epoll_params params;
+	int ret;
+
+	memset(&params, 0, sizeof(struct epoll_params));
+
+	params.__pad = 1;
+
+	ret = ioctl(fd, EPIOCSPARAMS, &params);
+
+	if (ret != -1)
+		error(1, 0, "EPIOCSPARAMS with non-zero __pad should error");
+
+	if (errno != EINVAL)
+		error(1, 0, "EPIOCSPARAMS with non-zero __pad errno should be EINVAL");
+
+	params.__pad = 0;
+	params.busy_poll_usecs = (unsigned int)INT_MAX + 1;
+
+	ret = ioctl(fd, EPIOCSPARAMS, &params);
+
+	if (ret != -1)
+		error(1, 0, "EPIOCSPARAMS should error busy_poll_usecs > S32_MAX");
+
+	if (errno != EINVAL)
+		error(1, 0, "EPIOCSPARAMS with busy_poll_usecs > S32_MAX, errno should be EINVAL");
+
+	params.__pad = 0;
+	params.busy_poll_usecs = 32;
+	params.prefer_busy_poll = 2;
+
+	ret = ioctl(fd, EPIOCSPARAMS, &params);
+
+	if (ret != -1)
+		error(1, 0, "EPIOCSPARAMS should error prefer_busy_poll > 1");
+
+	if (errno != EINVAL)
+		error(1, 0, "EPIOCSPARAMS with prefer_busy_poll > 1 errno should be EINVAL");
+
+	params.__pad = 0;
+	params.busy_poll_usecs = 32;
+	params.prefer_busy_poll = 1;
+	params.busy_poll_budget = 65535;
+
+	ret = ioctl(fd, EPIOCSPARAMS, &params);
+
+	if (ret != -1)
+		error(1, 0, "EPIOCSPARAMS should error busy_poll_budget > NAPI_POLL_WEIGHT");
+
+	if (errno != EPERM)
+		error(1, 0,
+		      "EPIOCSPARAMS with busy_poll_budget > NAPI_POLL_WEIGHT (without CAP_NET_ADMIN) errno should be EPERM");
+
+	invalid_params = (struct epoll_params *)0xdeadbeef;
+	ret = ioctl(fd, EPIOCSPARAMS, invalid_params);
+
+	if (ret != -1)
+		error(1, 0, "EPIOCSPARAMS should error when epoll_params is invalid");
+
+	if (errno != EFAULT)
+		error(1, 0, "EPIOCSPARAMS should set errno to EFAULT when epoll_params is invalid");
+}
+
+static void do_simple_test_set_and_get_valid(int fd)
+{
+	struct epoll_params params;
+	int ret;
+
+	memset(&params, 0, sizeof(struct epoll_params));
+
+	params.busy_poll_usecs = 25;
+	params.busy_poll_budget = 16;
+	params.prefer_busy_poll = 1;
+
+	ret = ioctl(fd, EPIOCSPARAMS, &params);
+
+	if (ret != 0)
+		error(1, errno, "EPIOCSPARAMS with valid params should not error");
+
+	/* check that the kernel returns the same values back */
+
+	memset(&params, 0, sizeof(struct epoll_params));
+
+	ret = ioctl(fd, EPIOCGPARAMS, &params);
+
+	if (ret != 0)
+		error(1, errno, "EPIOCGPARAMS should not error");
+
+	if (params.busy_poll_usecs != 25 ||
+	    params.busy_poll_budget != 16 ||
+	    params.prefer_busy_poll != 1 ||
+	    params.__pad != 0)
+		error(1, 0, "EPIOCGPARAMS returned incorrect values");
+}
+
+static void do_simple_test_invalid_fd(void)
+{
+	struct epoll_params params;
+	int ret;
+	int fd;
+
+	fd = socket(AF_UNIX, SOCK_DGRAM, 0);
+
+	if (fd == -1)
+		error(1, errno, "creating unix socket");
+
+	ret = ioctl(fd, EPIOCGPARAMS, &params);
+
+	if (ret != -1)
+		error(1, 0, "EPIOCGPARAMS on invalid epoll FD should error");
+
+	if (errno != ENOTTY)
+		error(1, 0, "EPIOCGPARAMS on invalid epoll FD should set errno to ENOTTY");
+
+	memset(&params, 0, sizeof(struct epoll_params));
+
+	ret = ioctl(fd, EPIOCSPARAMS, &params);
+
+	if (ret != -1)
+		error(1, 0, "EPIOCSPARAMS on invalid epoll FD should error");
+
+	if (errno != ENOTTY)
+		error(1, 0, "EPIOCSPARAMS on invalid epoll FD should set errno to ENOTTY");
+}
+
+static void do_simple_test_invalid_ioctl(int fd)
+{
+	struct epoll_params params;
+	int invalid_ioctl = EPIOCGPARAMS + 10;
+	int ret;
+
+	ret = ioctl(fd, invalid_ioctl, &params);
+
+	if (ret != -1)
+		error(1, 0, "invalid ioctl should return error");
+
+	if (errno != EINVAL)
+		error(1, 0, "invalid ioctl should set errno to EINVAL");
+}
+
+static void do_simple_test(void)
+{
+	int fd;
+
+	fd = epoll_create1(0);
+	if (fd == -1)
+		error(1, errno, "epoll_create");
+
+	do_simple_test_invalid_fd();
+	do_simple_test_invalid_ioctl(fd);
+	do_simple_test_get_params(fd);
+	do_simple_test_set_invalid(fd);
+	do_simple_test_set_and_get_valid(fd);
+
+	if (close(fd))
+		error(1, errno, "close");
+}
+
+int main(int argc, char **argv)
+{
+	parse_opts(argc, argv);
+
+	if (test_type == TEST_SIMPLE)
+		do_simple_test();
+	else
+		error(1, 0, "unknown test type: %d", test_type);
+
+	return 0;
+}