[PATCH] selftests/net: test generic-netlink policy dump operation ID

[Sahaj Chaudhari <sahaj123.sc@gmail.com>]

Check that a generic-netlink policy dump reports the requested command's
operation ID rather than zero.

Request the policy for CTRL_CMD_GETPOLICY from the control family and
verify that the response contains operation ID 10. Register the test as
a generated net selftest and ignore its built binary.

Tested: reproduces the missing operation ID on 7.0.0-34-generic and
passes on fixed 7.3.0-rc6-00063-g0c2669a9f4a1 in QEMU.

Signed-off-by: Sahaj Chaudhari <sahaj123.sc@gmail.com>
---
 tools/testing/selftests/net/.gitignore        |   1 +
 tools/testing/selftests/net/Makefile          |   1 +
 .../selftests/net/netlink_policy_dump_opid.c  | 223 ++++++++++++++++++
 3 files changed, 225 insertions(+)
 create mode 100644 tools/testing/selftests/net/netlink_policy_dump_opid.c

diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
index dacd36ed8455..5fa1c6024672 100644
--- a/tools/testing/selftests/net/.gitignore
+++ b/tools/testing/selftests/net/.gitignore
@@ -20,6 +20,7 @@ ipv6_fragmentation
 log.txt
 msg_zerocopy
 netlink-dumps
+netlink_policy_dump_opid
 nettest
 proc_net_pktgen
 psock_fanout
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 590b33e16d9f..09960735cb1a 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -186,6 +186,7 @@ TEST_GEN_PROGS := \
 	icmp_rfc4884 \
 	ipv6_flowlabel_mgr \
 	ipv6_fragmentation \
+	netlink_policy_dump_opid \
 	proc_net_pktgen \
 	reuseaddr_conflict \
 	reuseport_bpf \
diff --git a/tools/testing/selftests/net/netlink_policy_dump_opid.c b/tools/testing/selftests/net/netlink_policy_dump_opid.c
new file mode 100644
index 000000000000..4b53a8853109
--- /dev/null
+++ b/tools/testing/selftests/net/netlink_policy_dump_opid.c
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include <linux/genetlink.h>
+#include <linux/netlink.h>
+
+#include "kselftest.h"
+
+#define REQUEST_SIZE 128
+#define REPLY_SIZE 4096
+
+struct genl_request {
+	struct nlmsghdr nlh;
+	struct genlmsghdr genl;
+	char attrs[REQUEST_SIZE];
+};
+
+static int add_attr(struct genl_request *request, size_t size, uint16_t type,
+		    const void *data, size_t data_size)
+{
+	size_t offset = NLMSG_ALIGN(request->nlh.nlmsg_len);
+	size_t attr_size = NLA_HDRLEN + data_size;
+	size_t aligned_size = NLA_ALIGN(attr_size);
+	struct nlattr *attr;
+
+	if (offset + aligned_size > size)
+		return -E2BIG;
+
+	attr = (struct nlattr *)((char *)request + offset);
+	attr->nla_len = attr_size;
+	attr->nla_type = type;
+	memcpy((char *)attr + NLA_HDRLEN, data, data_size);
+	memset((char *)attr + attr_size, 0, aligned_size - attr_size);
+	request->nlh.nlmsg_len = offset + aligned_size;
+
+	return 0;
+}
+
+static int next_attr(const char **cursor, size_t *remaining,
+		     struct nlattr **attr)
+{
+	size_t length, aligned_length;
+
+	if (!*remaining)
+		return 0;
+	if (*remaining < NLA_HDRLEN)
+		return -EBADMSG;
+
+	*attr = (struct nlattr *)*cursor;
+	length = (*attr)->nla_len;
+	if (length < NLA_HDRLEN || length > *remaining)
+		return -EBADMSG;
+	aligned_length = NLA_ALIGN(length);
+	if (aligned_length > *remaining)
+		return -EBADMSG;
+
+	*cursor += aligned_length;
+	*remaining -= aligned_length;
+	return 1;
+}
+
+static int find_op_id(const struct nlattr *op_policy, bool *found)
+{
+	const char *cursor = (const char *)op_policy + NLA_HDRLEN;
+	size_t remaining = op_policy->nla_len - NLA_HDRLEN;
+	struct nlattr *attr;
+	int ret;
+
+	while ((ret = next_attr(&cursor, &remaining, &attr)) > 0) {
+		if ((attr->nla_type & NLA_TYPE_MASK) == CTRL_CMD_GETPOLICY)
+			*found = true;
+	}
+
+	return ret;
+}
+
+static int parse_policy_message(const struct nlmsghdr *nlh, bool *found)
+{
+	const char *cursor = (const char *)nlh + NLMSG_LENGTH(GENL_HDRLEN);
+	size_t remaining = nlh->nlmsg_len - NLMSG_LENGTH(GENL_HDRLEN);
+	struct nlattr *attr;
+	int ret;
+
+	while ((ret = next_attr(&cursor, &remaining, &attr)) > 0) {
+		if ((attr->nla_type & NLA_TYPE_MASK) == CTRL_ATTR_OP_POLICY) {
+			ret = find_op_id(attr, found);
+			if (ret < 0)
+				return ret;
+		}
+	}
+
+	return ret;
+}
+
+static int check_policy_dump(int fd)
+{
+	struct genl_request request = {
+		.nlh = {
+			.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN),
+			.nlmsg_type = GENL_ID_CTRL,
+			.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP | NLM_F_ACK,
+			.nlmsg_seq = 1,
+		},
+		.genl = {
+			.cmd = CTRL_CMD_GETPOLICY,
+			.version = 1,
+		},
+	};
+	char reply[REPLY_SIZE];
+	const __u16 family_id = GENL_ID_CTRL;
+	const __u32 op = CTRL_CMD_GETPOLICY;
+	bool found_op = false;
+	struct sockaddr_nl kernel = {
+		.nl_family = AF_NETLINK,
+	};
+	ssize_t sent;
+	int ret;
+
+	ret = add_attr(&request, sizeof(request), CTRL_ATTR_FAMILY_ID,
+		       &family_id, sizeof(family_id));
+	if (ret)
+		return ret;
+	ret = add_attr(&request, sizeof(request), CTRL_ATTR_OP,
+		       &op, sizeof(op));
+	if (ret)
+		return ret;
+
+	sent = sendto(fd, &request, request.nlh.nlmsg_len, 0,
+		      (struct sockaddr *)&kernel, sizeof(kernel));
+	if (sent < 0)
+		return -errno;
+	if (sent != request.nlh.nlmsg_len)
+		return -EIO;
+
+	for (;;) {
+		ssize_t received = recv(fd, reply, sizeof(reply), 0);
+		size_t offset = 0;
+
+		if (received < 0) {
+			if (errno == EINTR)
+				continue;
+			return -errno;
+		}
+
+		while (offset + NLMSG_HDRLEN <= received) {
+			struct nlmsghdr *nlh = (struct nlmsghdr *)(reply + offset);
+			size_t aligned_length;
+
+			if (nlh->nlmsg_len < NLMSG_HDRLEN ||
+			    nlh->nlmsg_len > received - offset)
+				return -EBADMSG;
+			if (nlh->nlmsg_seq != 1) {
+				offset += NLMSG_ALIGN(nlh->nlmsg_len);
+				continue;
+			}
+			if (nlh->nlmsg_type == NLMSG_ERROR) {
+				int error;
+
+				if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(error)))
+					return -EBADMSG;
+				error = *(int *)NLMSG_DATA(nlh);
+				if (error)
+					return error;
+			} else if (nlh->nlmsg_type == NLMSG_DONE) {
+				if (nlh->nlmsg_flags & NLM_F_DUMP_INTR)
+					return -EINTR;
+				return found_op ? 0 : -ENOENT;
+			} else if (nlh->nlmsg_type == GENL_ID_CTRL) {
+				if (nlh->nlmsg_len < NLMSG_LENGTH(GENL_HDRLEN))
+					return -EBADMSG;
+				ret = parse_policy_message(nlh, &found_op);
+				if (ret < 0)
+					return ret;
+			}
+
+			aligned_length = NLMSG_ALIGN(nlh->nlmsg_len);
+			if (aligned_length > received - offset)
+				return -EBADMSG;
+			offset += aligned_length;
+		}
+	}
+}
+
+int main(void)
+{
+	struct sockaddr_nl local = {
+		.nl_family = AF_NETLINK,
+	};
+	int fd, ret;
+
+	ksft_print_header();
+	ksft_set_plan(1);
+
+	fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_GENERIC);
+	if (fd < 0)
+		ksft_exit_fail_perror("opening generic-netlink socket");
+	if (bind(fd, (struct sockaddr *)&local, sizeof(local))) {
+		close(fd);
+		ksft_exit_fail_perror("binding generic-netlink socket");
+	}
+
+	ret = check_policy_dump(fd);
+	if (close(fd) && !ret)
+		ret = -errno;
+	if (ret == -ENOENT) {
+		ksft_test_result_fail("missing policy op id %u\n",
+				      CTRL_CMD_GETPOLICY);
+	} else if (ret) {
+		errno = -ret;
+		ksft_test_result_fail("GETPOLICY dump failed: %s\n",
+				      strerror(errno));
+	} else {
+		ksft_test_result_pass("policy dump identified command id %u\n",
+				      CTRL_CMD_GETPOLICY);
+	}
+	ksft_finished();
+}
-- 
2.43.0