strace/tests/netlink_protocol.c - nest-cam/4320010/strace - Git at Google

 /*
  * Check decoding of netlink protocol.
  *
  * Copyright (c) 2014-2016 Dmitry V. Levin <ldv@altlinux.org>
  * Copyright (c) 2016 Fabien Siron <fabien.siron@epita.fr>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. The name of the author may not be used to endorse or promote products
  *    derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "tests.h"

 #ifdef HAVE_SYS_XATTR_H

 # include <stdio.h>
 # include <stdlib.h>
 # include <string.h>
 # include <unistd.h>
 # include <sys/xattr.h>
 # include <netinet/in.h>
 # include <linux/netlink.h>
 # include <linux/sock_diag.h>
 # include <linux/netlink_diag.h>

 # if !defined NETLINK_SOCK_DIAG && defined NETLINK_INET_DIAG
 #  define NETLINK_SOCK_DIAG NETLINK_INET_DIAG
 # endif

 static void
 send_query(const int fd)
 {
 	static const struct req {
 		struct nlmsghdr nlh;
 		const char magic[4];
 	} c_req = {
 		.nlh = {
 			.nlmsg_len = sizeof(struct req),
 			.nlmsg_type = NLMSG_NOOP,
 			.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST
 		},
 		.magic = "abcd"
 	};
 	struct req *const req = tail_memdup(&c_req, sizeof(c_req));

 	/* zero address */
 	if (sendto(fd, NULL, sizeof(*req), MSG_DONTWAIT, NULL, 0) != -1)
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, NULL, %u, MSG_DONTWAIT, NULL, 0) = -1 %s (%m)\n",
 	       fd, (unsigned) sizeof(*req), errno2name());

 	/* zero length */
 	if (sendto(fd, req, 0, MSG_DONTWAIT, NULL, 0) != 0)
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, \"\", 0, MSG_DONTWAIT, NULL, 0) = 0\n", fd);

 	/* zero address and length */
 	if (sendto(fd, NULL, 0, MSG_DONTWAIT, NULL, 0) != 0)
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, NULL, 0, MSG_DONTWAIT, NULL, 0) = 0\n", fd);

 	/* unfetchable struct nlmsghdr */
 	const void *const efault = tail_alloc(sizeof(struct nlmsghdr) - 1);
 	sendto(fd, efault, sizeof(struct nlmsghdr), MSG_DONTWAIT, NULL, 0);

 	printf("sendto(%d, %p, %u, MSG_DONTWAIT, NULL, 0) = -1 EFAULT (%m)\n",
 	       fd, efault, (unsigned) sizeof(struct nlmsghdr));

 	/* whole message length < sizeof(struct nlmsghdr) */
 	if (sendto(fd, req->magic, sizeof(req->magic), MSG_DONTWAIT, NULL, 0)
 	    != (unsigned) sizeof(req->magic))
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, \"abcd\", %u, MSG_DONTWAIT, NULL, 0) = %u\n",
 	       fd, (unsigned) sizeof(req->magic), (unsigned) sizeof(req->magic));

 	/* a single message with some data */
 	if (sendto(fd, req, sizeof(*req), MSG_DONTWAIT, NULL, 0) !=
 	    (unsigned) sizeof(*req))
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}, \"abcd\"}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
 	       fd, req->nlh.nlmsg_len, NLM_F_DUMP,
 	       (unsigned) sizeof(*req), (unsigned) sizeof(*req));

 	/* a single message without data */
 	req->nlh.nlmsg_len = sizeof(req->nlh);

 	if (sendto(fd, &req->nlh, sizeof(req->nlh), MSG_DONTWAIT, NULL, 0)
 	    != (unsigned) sizeof(req->nlh))
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
 	       fd, req->nlh.nlmsg_len, NLM_F_DUMP,
 	       (unsigned) sizeof(req->nlh), (unsigned) sizeof(req->nlh));

 	/* nlmsg_len > whole message length */
 	req->nlh.nlmsg_len = sizeof(*req) + 8;
 	if (sendto(fd, req, sizeof(*req), MSG_DONTWAIT, NULL, 0) !=
 	    (unsigned) sizeof(*req))
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}, \"abcd\"}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
 	       fd, req->nlh.nlmsg_len, NLM_F_DUMP,
 	       (unsigned) sizeof(*req), (unsigned) sizeof(*req));

 	/* nlmsg_len < sizeof(struct nlmsghdr) */
 	req->nlh.nlmsg_len = 8;
 	if (sendto(fd, req, sizeof(*req), MSG_DONTWAIT, NULL, 0) != sizeof(*req))
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
 	       fd, req->nlh.nlmsg_len, NLM_F_DUMP,
 	       (unsigned) sizeof(*req), (unsigned) sizeof(*req));

 	/* a sequence of two nlmsg objects */
 	struct reqs {
 		struct req req1;
 		char padding[NLMSG_ALIGN(sizeof(struct req)) - sizeof(struct req)];
 		struct req req2;
 	} *const reqs = tail_alloc(sizeof(*reqs));
 	memcpy(&reqs->req1, &c_req, sizeof(c_req));
 	memcpy(&reqs->req2, &c_req, sizeof(c_req));

 	sendto(fd, reqs, sizeof(*reqs), MSG_DONTWAIT, NULL, 0);

 	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}, \"abcd\"}, {{len=%u, type=NLMSG_NOOP"
 	       ", flags=NLM_F_REQUEST|0x%x, seq=0, pid=0}, \"abcd\"}]"
 	       ", %u, MSG_DONTWAIT, NULL, 0) = %u\n",
 	       fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP,
 	       reqs->req2.nlh.nlmsg_len, NLM_F_DUMP,
 	       (unsigned) sizeof(*reqs), (unsigned) sizeof(*reqs));

 	/* unfetchable second struct nlmsghdr */
 	void *const efault2 = tail_memdup(&reqs->req1, sizeof(reqs->req1));
 	sendto(fd, efault2, sizeof(*reqs), MSG_DONTWAIT, NULL, 0);

 	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}, \"abcd\"}, %p], %u, MSG_DONTWAIT, NULL, 0)"
 	       " = -1 EFAULT (%m)\n",
 	       fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP,
 	       &((struct reqs *) efault2)->req2, (unsigned) sizeof(*reqs));

 	/* message length is not enough for the second struct nlmsghdr */
 	if (sendto(fd, reqs, sizeof(*reqs) - sizeof(req->nlh), MSG_DONTWAIT, NULL, 0)
 	    != sizeof(*reqs) - sizeof(req->nlh))
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}, \"abcd\"}, \"",
 	       fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP);
 	print_quoted_memory((void *) &reqs->req2.nlh,
 			    sizeof(reqs->req2) - sizeof(req->nlh));
 	printf("\"], %u, MSG_DONTWAIT, NULL, 0) = %u\n",
 	       (unsigned) (sizeof(*reqs) - sizeof(req->nlh)),
 	       (unsigned) (sizeof(*reqs) - sizeof(req->nlh)));

 	/* second nlmsg_len < sizeof(struct nlmsghdr) */
 	reqs->req2.nlh.nlmsg_len = 4;
 	if (sendto(fd, reqs, sizeof(*reqs), MSG_DONTWAIT, NULL, 0)
 	    != sizeof(*reqs))
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 	       ", seq=0, pid=0}, \"abcd\"}, {{len=%u, type=NLMSG_NOOP"
 	       ", flags=NLM_F_REQUEST|0x%x, seq=0, pid=0}}], %u"
 	       ", MSG_DONTWAIT, NULL, 0) = %u\n",
 	       fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP,
 	       reqs->req2.nlh.nlmsg_len, NLM_F_DUMP,
 	       (unsigned) sizeof(*reqs), (unsigned) sizeof(*reqs));

 	/* abbreviated output */
 # define DEFAULT_STRLEN 32
 # define ABBREV_LEN (DEFAULT_STRLEN + 1)
 	const unsigned int msg_len = sizeof(struct nlmsghdr) * ABBREV_LEN;
 	struct nlmsghdr *const msgs = tail_alloc(msg_len);
 	unsigned int i;
 	for (i = 0; i < ABBREV_LEN; ++i) {
 		msgs[i].nlmsg_len = sizeof(*msgs);
 		msgs[i].nlmsg_type = NLMSG_NOOP;
 		msgs[i].nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST;
 		msgs[i].nlmsg_seq = i;
 		msgs[i].nlmsg_pid = 0;
 	}

 	if (sendto(fd, msgs, msg_len, MSG_DONTWAIT, NULL, 0) != (int) msg_len)
 		perror_msg_and_skip("sendto");

 	printf("sendto(%d, [", fd);
 	for (i = 0; i < DEFAULT_STRLEN; ++i) {
 		if (i)
 			printf(", ");
 		printf("{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST|0x%x"
 		       ", seq=%u, pid=0}}",
 		       msgs[i].nlmsg_len, NLM_F_DUMP, msgs[i].nlmsg_seq);
 	}
 	printf(", ...], %u, MSG_DONTWAIT, NULL, 0) = %u\n", msg_len, msg_len);
 }

 int main(void)
 {
 	struct sockaddr_nl addr;
 	socklen_t len = sizeof(addr);
 	int fd;

 	memset(&addr, 0, sizeof(addr));
 	addr.nl_family = AF_NETLINK;

 	if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG)) == -1)
 		perror_msg_and_skip("socket AF_NETLINK");

 	printf("socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG) = %d\n",
 	       fd);
 	if (bind(fd, (struct sockaddr *) &addr, len))
 		perror_msg_and_skip("bind");
 	printf("bind(%d, {sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}"
 	       ", %u) = 0\n", fd, len);

 	char *path;
 	if (asprintf(&path, "/proc/self/fd/%u", fd) < 0)
 		perror_msg_and_fail("asprintf");
 	char buf[256];
 	if (getxattr(path, "system.sockprotoname", buf, sizeof(buf) - 1) < 0)
 		perror_msg_and_skip("getxattr");
 	free(path);

 	send_query(fd);

 	printf("+++ exited with 0 +++\n");

 	return 0;
 }

 #else

 SKIP_MAIN_UNDEFINED("HAVE_SYS_XATTR_H")

 #endif
	/*
	* Check decoding of netlink protocol.
	*
	* Copyright (c) 2014-2016 Dmitry V. Levin <ldv@altlinux.org>
	* Copyright (c) 2016 Fabien Siron <fabien.siron@epita.fr>
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. The name of the author may not be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "tests.h"

	#ifdef HAVE_SYS_XATTR_H

	# include <stdio.h>
	# include <stdlib.h>
	# include <string.h>
	# include <unistd.h>
	# include <sys/xattr.h>
	# include <netinet/in.h>
	# include <linux/netlink.h>
	# include <linux/sock_diag.h>
	# include <linux/netlink_diag.h>

	# if !defined NETLINK_SOCK_DIAG && defined NETLINK_INET_DIAG
	# define NETLINK_SOCK_DIAG NETLINK_INET_DIAG
	# endif

	static void
	send_query(const int fd)
	{
	static const struct req {
	struct nlmsghdr nlh;
	const char magic[4];
	} c_req = {
	.nlh = {
	.nlmsg_len = sizeof(struct req),
	.nlmsg_type = NLMSG_NOOP,
	.nlmsg_flags = NLM_F_DUMP \| NLM_F_REQUEST
	},
	.magic = "abcd"
	};
	struct req *const req = tail_memdup(&c_req, sizeof(c_req));

	/* zero address */
	if (sendto(fd, NULL, sizeof(*req), MSG_DONTWAIT, NULL, 0) != -1)
	perror_msg_and_skip("sendto");

	printf("sendto(%d, NULL, %u, MSG_DONTWAIT, NULL, 0) = -1 %s (%m)\n",
	fd, (unsigned) sizeof(*req), errno2name());

	/* zero length */
	if (sendto(fd, req, 0, MSG_DONTWAIT, NULL, 0) != 0)
	perror_msg_and_skip("sendto");

	printf("sendto(%d, \"\", 0, MSG_DONTWAIT, NULL, 0) = 0\n", fd);

	/* zero address and length */
	if (sendto(fd, NULL, 0, MSG_DONTWAIT, NULL, 0) != 0)
	perror_msg_and_skip("sendto");

	printf("sendto(%d, NULL, 0, MSG_DONTWAIT, NULL, 0) = 0\n", fd);

	/* unfetchable struct nlmsghdr */
	const void *const efault = tail_alloc(sizeof(struct nlmsghdr) - 1);
	sendto(fd, efault, sizeof(struct nlmsghdr), MSG_DONTWAIT, NULL, 0);

	printf("sendto(%d, %p, %u, MSG_DONTWAIT, NULL, 0) = -1 EFAULT (%m)\n",
	fd, efault, (unsigned) sizeof(struct nlmsghdr));

	/* whole message length < sizeof(struct nlmsghdr) */
	if (sendto(fd, req->magic, sizeof(req->magic), MSG_DONTWAIT, NULL, 0)
	!= (unsigned) sizeof(req->magic))
	perror_msg_and_skip("sendto");

	printf("sendto(%d, \"abcd\", %u, MSG_DONTWAIT, NULL, 0) = %u\n",
	fd, (unsigned) sizeof(req->magic), (unsigned) sizeof(req->magic));

	/* a single message with some data */
	if (sendto(fd, req, sizeof(*req), MSG_DONTWAIT, NULL, 0) !=
	(unsigned) sizeof(*req))
	perror_msg_and_skip("sendto");

	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}, \"abcd\"}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
	fd, req->nlh.nlmsg_len, NLM_F_DUMP,
	(unsigned) sizeof(req), (unsigned) sizeof(req));

	/* a single message without data */
	req->nlh.nlmsg_len = sizeof(req->nlh);

	if (sendto(fd, &req->nlh, sizeof(req->nlh), MSG_DONTWAIT, NULL, 0)
	!= (unsigned) sizeof(req->nlh))
	perror_msg_and_skip("sendto");

	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
	fd, req->nlh.nlmsg_len, NLM_F_DUMP,
	(unsigned) sizeof(req->nlh), (unsigned) sizeof(req->nlh));

	/* nlmsg_len > whole message length */
	req->nlh.nlmsg_len = sizeof(*req) + 8;
	if (sendto(fd, req, sizeof(*req), MSG_DONTWAIT, NULL, 0) !=
	(unsigned) sizeof(*req))
	perror_msg_and_skip("sendto");

	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}, \"abcd\"}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
	fd, req->nlh.nlmsg_len, NLM_F_DUMP,
	(unsigned) sizeof(req), (unsigned) sizeof(req));

	/* nlmsg_len < sizeof(struct nlmsghdr) */
	req->nlh.nlmsg_len = 8;
	if (sendto(fd, req, sizeof(req), MSG_DONTWAIT, NULL, 0) != sizeof(req))
	perror_msg_and_skip("sendto");

	printf("sendto(%d, {{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}}, %u, MSG_DONTWAIT, NULL, 0) = %u\n",
	fd, req->nlh.nlmsg_len, NLM_F_DUMP,
	(unsigned) sizeof(req), (unsigned) sizeof(req));

	/* a sequence of two nlmsg objects */
	struct reqs {
	struct req req1;
	char padding[NLMSG_ALIGN(sizeof(struct req)) - sizeof(struct req)];
	struct req req2;
	} const reqs = tail_alloc(sizeof(reqs));
	memcpy(&reqs->req1, &c_req, sizeof(c_req));
	memcpy(&reqs->req2, &c_req, sizeof(c_req));

	sendto(fd, reqs, sizeof(*reqs), MSG_DONTWAIT, NULL, 0);

	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}, \"abcd\"}, {{len=%u, type=NLMSG_NOOP"
	", flags=NLM_F_REQUEST\|0x%x, seq=0, pid=0}, \"abcd\"}]"
	", %u, MSG_DONTWAIT, NULL, 0) = %u\n",
	fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP,
	reqs->req2.nlh.nlmsg_len, NLM_F_DUMP,
	(unsigned) sizeof(reqs), (unsigned) sizeof(reqs));

	/* unfetchable second struct nlmsghdr */
	void *const efault2 = tail_memdup(&reqs->req1, sizeof(reqs->req1));
	sendto(fd, efault2, sizeof(*reqs), MSG_DONTWAIT, NULL, 0);

	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}, \"abcd\"}, %p], %u, MSG_DONTWAIT, NULL, 0)"
	" = -1 EFAULT (%m)\n",
	fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP,
	&((struct reqs ) efault2)->req2, (unsigned) sizeof(reqs));

	/* message length is not enough for the second struct nlmsghdr */
	if (sendto(fd, reqs, sizeof(*reqs) - sizeof(req->nlh), MSG_DONTWAIT, NULL, 0)
	!= sizeof(*reqs) - sizeof(req->nlh))
	perror_msg_and_skip("sendto");

	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}, \"abcd\"}, \"",
	fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP);
	print_quoted_memory((void *) &reqs->req2.nlh,
	sizeof(reqs->req2) - sizeof(req->nlh));
	printf("\"], %u, MSG_DONTWAIT, NULL, 0) = %u\n",
	(unsigned) (sizeof(*reqs) - sizeof(req->nlh)),
	(unsigned) (sizeof(*reqs) - sizeof(req->nlh)));

	/* second nlmsg_len < sizeof(struct nlmsghdr) */
	reqs->req2.nlh.nlmsg_len = 4;
	if (sendto(fd, reqs, sizeof(*reqs), MSG_DONTWAIT, NULL, 0)
	!= sizeof(*reqs))
	perror_msg_and_skip("sendto");

	printf("sendto(%d, [{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=0, pid=0}, \"abcd\"}, {{len=%u, type=NLMSG_NOOP"
	", flags=NLM_F_REQUEST\|0x%x, seq=0, pid=0}}], %u"
	", MSG_DONTWAIT, NULL, 0) = %u\n",
	fd, reqs->req1.nlh.nlmsg_len, NLM_F_DUMP,
	reqs->req2.nlh.nlmsg_len, NLM_F_DUMP,
	(unsigned) sizeof(reqs), (unsigned) sizeof(reqs));

	/* abbreviated output */
	# define DEFAULT_STRLEN 32
	# define ABBREV_LEN (DEFAULT_STRLEN + 1)
	const unsigned int msg_len = sizeof(struct nlmsghdr) * ABBREV_LEN;
	struct nlmsghdr *const msgs = tail_alloc(msg_len);
	unsigned int i;
	for (i = 0; i < ABBREV_LEN; ++i) {
	msgs[i].nlmsg_len = sizeof(*msgs);
	msgs[i].nlmsg_type = NLMSG_NOOP;
	msgs[i].nlmsg_flags = NLM_F_DUMP \| NLM_F_REQUEST;
	msgs[i].nlmsg_seq = i;
	msgs[i].nlmsg_pid = 0;
	}

	if (sendto(fd, msgs, msg_len, MSG_DONTWAIT, NULL, 0) != (int) msg_len)
	perror_msg_and_skip("sendto");

	printf("sendto(%d, [", fd);
	for (i = 0; i < DEFAULT_STRLEN; ++i) {
	if (i)
	printf(", ");
	printf("{{len=%u, type=NLMSG_NOOP, flags=NLM_F_REQUEST\|0x%x"
	", seq=%u, pid=0}}",
	msgs[i].nlmsg_len, NLM_F_DUMP, msgs[i].nlmsg_seq);
	}
	printf(", ...], %u, MSG_DONTWAIT, NULL, 0) = %u\n", msg_len, msg_len);
	}

	int main(void)
	{
	struct sockaddr_nl addr;
	socklen_t len = sizeof(addr);
	int fd;

	memset(&addr, 0, sizeof(addr));
	addr.nl_family = AF_NETLINK;

	if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG)) == -1)
	perror_msg_and_skip("socket AF_NETLINK");

	printf("socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG) = %d\n",
	fd);
	if (bind(fd, (struct sockaddr *) &addr, len))
	perror_msg_and_skip("bind");
	printf("bind(%d, {sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}"
	", %u) = 0\n", fd, len);

	char *path;
	if (asprintf(&path, "/proc/self/fd/%u", fd) < 0)
	perror_msg_and_fail("asprintf");
	char buf[256];
	if (getxattr(path, "system.sockprotoname", buf, sizeof(buf) - 1) < 0)
	perror_msg_and_skip("getxattr");
	free(path);

	send_query(fd);

	printf("+++ exited with 0 +++\n");

	return 0;
	}

	#else

	SKIP_MAIN_UNDEFINED("HAVE_SYS_XATTR_H")

	#endif