tests/inode_of_sockfd.c

/*
 * This file is part of strace test suite.
 *
 * Copyright (c) 2016 Dmitry V. Levin <ldv@altlinux.org>
 * 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"
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>

unsigned long
inode_of_sockfd(const int fd)
{
	assert(fd >= 0);

	char linkpath[sizeof("/proc/self/fd/%u") + sizeof(int) * 3];
	assert(snprintf(linkpath, sizeof(linkpath), "/proc/self/fd/%u", fd)
	       < (int) sizeof(linkpath));

	char path[PATH_MAX + 1];
	const ssize_t path_len = readlink(linkpath, path, sizeof(path) - 1);
	if (path_len < 0)
		perror_msg_and_fail("readlink: %s", linkpath);
	path[path_len] = '\0';

	static const char prefix[] = "socket:[";
	const size_t prefix_len = sizeof(prefix) - 1;
	assert(strncmp(path, prefix, prefix_len) == 0
	       && path[path_len - 1] == ']');

	return strtoul(path + prefix_len, NULL, 10);
}